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Aqueous Cleaning

HandbookA GUIDE TO CRITICAL-CLEANING

PROCEDURES, TECHNIQUES, AND VALIDATION

Aqueous Cleaning

Handbook

ince their first use in healthcare and laboratorysettings, aqueous critical cleaners—cleaners which leave no interfering residues—have found increasing application in a wide range ofindustries as an environmentally benign alter-

native to ozone-depleting compounds and haz-ardous solvents.

This book distills and presents practical infor-mation covering the history of such cleaners—whatthey are, how they work, and how to make best useof them in cleaning products and components inelectronics, metalworking, precision manufacturing;pharmaceutical, food-and-beverage, and chemicalprocessing; and many other industrial applications.

It is written by a medical doctor, Alan Zisman,and a director of aqueous-cleaner marketing,Malcolm McLaughlin, who also has academictraining and professional experience in chemistry.Both are employed by Alconox, Inc., a New Yorkfirm which has been a leading developer and sup-plier of aqueous cleaners for laboratory, healthcare,and industrial applications for more than 50 years.

ABOUT THE AUTHORSMalcolm McLaughlin, M.A. is Vice President,Marketing, for Alconox, Inc., a leading developer andmanufacturer of critical-cleaning aqueous detergents. Heearned his M.A. in Chemistry from Columbia University. Alan Zisman, M.D. is President and Director of Alconox,Inc. He earned his M.D. at Columbia University’s Collegeof Physicians and Surgeons.

S

Malcolm C. McLaughlin, M.A.Alan S. Zisman, M.D.

and the Technical Services Staff of Alconox, Inc.

$39.95 Third Edition

2002 Handbook Cover 9/24/02 11:33 AM

T H E

Aqueous Cleaning

Handbook

Aqueous Cleaning

HandbookA GUIDE TO CRITICAL-CLEANING

PROCEDURES, TECHNIQUES, AND VALIDATION

Malcolm C. McLaughlin, M.A.Alan S. Zisman, M.D.

and the Technical Services Staff of Alconox, Inc.

ContentsFOREWORD v

INTRODUCTION ix

CHAPTER ONEWhat Is an Aqueous Cleaner? 1

CHAPTER TWOThe Chemistry of Aqueous Cleaning 9

CHAPTER THREEAqueous-Cleaning Processes 19

CHAPTER FOURSelecting an Aqueous-Cleaning Detergent 41

CHAPTER FIVETesting and Selecting a Detergent and Cleaning System 51

CHAPTER SIXIndustrial Cleaning Applications 65

CHAPTER SEVENStandard Operating Procedures 97

iii

© 1998 Alconox, Inc.© 2000 Alconox, Inc.

Second Printing© 2002 Alconox, Inc.

Third Printing

All rights reserved under Pan-American CopyrightConventions.

Published in the United States by AL Technical Communications, LLC,

White Plains, NYUnauthorized reproduction of this book is forbidden by law.

International Standard Book Number0-9723478-0-1

Library of Congress Catalog Card Number2002110614

Special thanks to Peter Levin, Elliot Lebowitz, andAndrew Jacobson of Alconox, Inc.; Jim Morris-Lee, Mary Kane, Steve Smith

and Mea Andreasen of The Morris-Lee Group; without whose tireless (but now at least not thankless) help this book would not have been possible.

ii

ForewordMost cleaning practitioners are familiar with the story: thescientists who developed chlorofluorocarbons (CFCs), first asrefrigerants and then as solvents, had struck upon what theythought were safe, inert materials. CFCs would replace petro-leum-based chemicals known for their health hazards. CFCswere relatively inexpensive, readily available and most impor-tantly, they worked.

What the researchers did not know was the impact thesechlorine-containing substances would have on the ozone layer:that portion of the atmosphere responsible for shielding theearth from some of the solar system’s most harmful ultraviolet(UV) rays.

Chlorine (Cl) atoms participate in the destruction of ozone(O3) as they randomly make their way into the upper atmos-phere. The reaction is catalytic with the potential for one (1) Clatom to destroy thousands of O3 molecules. The introductionof hydrochlorofluorocarbons (HCFCs) as secondary replace-ment chemicals reduced but did not eliminate this danger.

CFCs and HCFCs also increase global warming by interfer-ing with the atmosphere’s natural ability to radiate heat awayfrom the planet. This exacerbates the Greenhouse Effect mostnoticeably impacted by fossil fuel burning.

The international Montreal Protocol treaty and the U.S.Clean Air Act Amendments govern the usage and productionof most of these compounds, including VOC (volatile organic

Foreword v

CHAPTER EIGHTCleaning Validation 119

CHAPTER NINEWastewater Treatment and Cleaner Recycling 129

CHAPTER TENMeasuring Cleanliness 141

CHAPTER ELEVENEnvironmental Health and Safety Considerations 155

APPENDIXI Clean Air Act Amendments 162II Cleaner Types from Alconox, Inc. 163III Detergent Selection Guide 164IV Glossary of Essential Terms 165V Application Case Histories 171

Optical Substrate 171Metal Valves 172Pharmaceutical Equipment 173Glass 174Filter Membranes 175Wine Tasting Glasses 176Laboratory Pipets 177

VI Index 179

For every book printed, Alconox, Inc. will donate one dollar toAmerican Forests to support forestry conservation and tree-plantingprojects. American Forests has been promoting protection and sus-tainable management of forest ecosystems since 1875. For informa-tion, contact Alconox, Inc., 30 Glenn Street, White Plains, NY 10603,USA, 914-948-4040, fax 914-948-4088, [email protected],www.alconox.com.

iv The Aqueous Cleaning Handbook

Methods of extrapolating test data as well as gender and agedifferentials require review.

Other problems remain. Most government policies focuson chemical handling and use. They do not necessarily takeinto account a chemical’s life cycle or environmental fate. Nordo they fully consider the drain that chemical manufacturecan place on natural resources and raw materials. Risks maysimply be shifting from the site of usage to the chemical’s pro-duction plant (or power plant) rather than real progress beingmade. This is especially worrisome in light of environmentaljustice issues.

It is no wonder, then, that many industries are rediscover-ing water (H2O) as the ideal cleaning medium, the only uni-versal solvent truly non-toxic to both humans and the environ-ment. Like the CFC and HCFC designers, today’s formulatorswill undoubtedly push aqueous (i.e., water-based) cleaners tothe scientific limits of the day. This is no time for intellectualarrogance. Chemical exposures effect workers, consumers andcommunities. Early partnering with stakeholders may amelio-rate the mistakes historically associated with the discoveryprocess.

The constituents and mechanisms of aqueous cleanersmust be understood. Surfactants and emulsifiers, alkalinebuilders and the dependence on water and energy (increasing-ly precious resources in an over-populated world), all matterto the concerned scientist. One suspects that not all aqueouscleaners are created equal.

There are challenging opportunities for advancement. It ispossible to envision the day when manufacturers will nolonger be forced to use hazardous materials for surface clean-ing in the production of quality goods and services.Furthermore, toxic-free analytical techniques for surface eval-uation will be invented that are superior to those now in use.

Based on the cornerstones of pollution prevention andcleaner production,* pursuit of this vision minimizes or elimi-nates environmental impacts and health and safety riskslinked to many industrial cleaning applications. These objec-tives support a more sustainable business plan, leading to bet-ter job security and overall quality of life.

Alconox, Inc. deserves much credit for its self-imposed

Foreword vii

compound) emitters. The U.S. Environmental ProtectionAgency’s (EPA) Significant New Alternatives Policy (SNAP)identifies acceptable substitutes. These laws purposefully dev-astated organic and chlorinated solvent markets while foster-ing research and development. Hundreds of companies spe-cializing in surface preparation, cleaning, rinsing, drying andinspection owe their economic feasibility to regulatory drivers.

In addition, the U.S. EPA’s Toxic Release Inventory (TRI)provides a powerful tracking tool for looking at the places andthe reasons hazardous chemicals are used. This transpiredagainst a back drop of Right-to-Know legislation and chemicalaccidents culminating, in no small measure, with the incep-tion of Material Safety Data Sheets (MSDSs). The occurrenceof the words “test data unavailable” or “unknown” on many ofthese documents helped set the stage for other environmentalinitiatives.

Initiatives in northern Europe have begun to reflect theprecautionary principle. This is the EH&S equivalent to theHippocratic medical oath, “First do no harm.” The translation:sell no product whose environmental, health and safety con-cerns have not yet been elucidated.

The principle represents a radical departure from conven-tional thinking that may be lost on those not directly involvedin the chemical industry Thousands of new chemicals enterthe market each year while little is known about the vastmajority of existing chemicals. This would no longer be toler-ated under a system that demands thorough environmentaland health information before exposure (as opposed to after apotential, unknown disaster). Chemical manufacturers wouldhave stronger stewardship responsibilities. Products wouldtake longer to reach the marketplace. And once a substancewas deemed safe, who would be liable for any errors that aresure to occur? It remains to be seen whether American society,steeped in litigation, can rise to the occasion.

Testing parameters other than those based on the cancerparadigm need to be determined. The study of chemicals’effects at low concentrations, should be expanded (negativeimpacts from low-dose exposures include hormone mimickersand endocrine disrupters). The effects of chemical mixtures,individually thought to be benign, bear more investigation.

vi The Aqueous Cleaning Handbook

IntroductionToday, the terms precision or critical cleaning include anycleaning process where residue can cause a failure in the func-tion of the surface being cleaned. In general industry thisincludes electronic component cleaning and surface prepara-tion of metals prior to coating or bonding. It can also includecleaning applications in industries such as chemicals, foodand beverage, pharmaceuticals, and cosmetics where solidsand liquids come into contact with plastic, glass, and metalpiping and processing equipment.

Current practice for critical cleaning includes the use ofvolatile solvents, corrosive chemicals, and aqueous detergents.In today’s hazard-sensitive workplace, however, many compa-nies are closely examining their use of volatile-solvent and cor-rosive-chemical cleaners. In that regard, aqueous cleaning rep-resents an economical, environmentally benign alternative. Inmany cases aqueous cleaning is also the best available technol-ogy and provides a viable long-term solution to environmentalissues.

It is important that these cleaners not contain high con-centrations of volatile organic compounds or solvents due totheir air-pollution and ozone-depletion potential. They shouldalso be formulated to minimize worker hazards yet still delivercritical-cleaning performance in the intended application.

This handbook is designed to help laboratory and plantpersonnel select aqueous cleaners and systems more wisely

Introduction ix

mission to educate the public about aqueous cleaning.Readers, prepare to learn well from this Handbook.

— Carole LeBlanc Toxics Use Reduction Institute University of Massachusetts • Lowell

*The term cleaner production refers to safer, greener, and more sustain-able manufacturing methods and materials and not the production ofchemical cleaners.

viii The Aqueous Cleaning Handbook

CHAPTER ONE

What Is an Aqueous Cleaner?An aqueous cleaner is a blend of ingredients designed toenhance the cleaning ability of water. Typically an aqueouscleaner contains a surface active agent (surfactant) andbuilders to help the surfactant. The surfactant acts as a wet-ting agent to allow the cleaning solutions to penetrate intocrevices and around and under soils. The surfactant will usual-ly also act as an emulsifier to help form emulsions with water-insoluble oils. The builders usually react with dissolved metalions in the water to help stop them from interfering withcleaning. (Chapter Two of this handbook provides a thoroughdiscussion of these ingredients.)

HISTORY OF CLEANINGSurface cleaning or degreasing can be defined as the removalof contamination or unwanted material from a surface and theneed to remove soils—defined as any extraneous or unwantedmaterial deposited on, or attached to a substrate surface—foresthetic, medicinal, social, and scientific reasons. The historyof cleaning includes the development and use of four types ofcleaning compounds:

• Soaps—which use salts of organic acids with cleaningproperties such as sodium stearate in hand bar soap thatmake a surface active agent with wetting and emulsifyingproperties.

• Solvents—which use solvency to remove soils by dissolvingthem with the solvent to form a homogeneous mixture.

What Is An Aqueous Cleaner? 1

and maximize their cleaning performance. While by no meansexhaustive, it represents the culmination of more than 50years experience with aqueous-cleaning technology by thestaff of Alconox, Inc., a leading developer and supplier ofaqueous-cleaning detergents.

In its pages you will find handy, easy-to-read summaries ofwhat aqueous cleaning is and how it works—its chemistry andmechanical properties. This handbook also contains criticalinformation on how to select an aqueous cleaner and make themost of the cleaning potential of an aqueous-cleaning system.

To make it easy for you to find important information,cleaning considerations for each industry are also presented.

If you have any questions that are not included in thishandbook, please feel free to contact our technical servicesdepartment at Alconox, Inc. (877-877-2526). In fact, manyideas for new aqueous-cleaning compounds have come fromsuch contact, and you’ll find our technical service staff readyand willing to help with your questions or concerns.

Whether you have used aqueous cleaners and systems forsome time or are just now considering switching to aqueouscleaning, we hope you find this handbook helpful.

— Alan S. Zisman, M.D.Malcolm M. McLaughlin, M.A.Alconox, Inc.

x The Aqueous Cleaning Handbook

more readily removed from a reaction mixture by distillationor evaporation. In cleaning substrates, the most commonapplication for industrial solvents is to put dirty solid matter(parts, products, etc.) into the solvent where foreign matter onthe surface is dissolved into the solvent. The substrate is thenremoved from the solvent-dilute-foreign-matter mixture whichevaporates and deposits a relatively much smaller amount offoreign matter left over from the dilute mixture—leaving aproportionally clean substrate.

The principle of ‘like dissolves like’ was discovered early inhuman history by simple observation. In this trial-and-errorprocess some terpenes, natural organic compounds occurringin the essential oils and oleoresins of plants (lemon, orange)and conifers (balsam, pine), were found to have solvating pow-ers. It is very important to match the solvent character of yoursoil or foreign matter to the type of solvent with which you arecleaning. A given solvent will be “like” some soils and “unlike”other soils where it will not be able to dissolve and clean aswell as a solvent with like properties.

Synthetic Solvents—Nonaqueous solvent cleaners includechlorocarbons, chlorofluorocarbons (CFCs), and hydrochloro-fluorocarbons (HCFCs). Chlorocarbons are carbon-chlorinebased solvents. Halocarbons are halogen-carbon compounds(chlorine, fluorine, bromine, and iodine).

The most common examples used in cleaning are carbontetrachloride, trichlorocarbon (TCA, “trike,” or methylchoro-form), and perchloroethylene (PCE, or “Perc”). Chlorofluoro-carbons (CFCs) are carbon, fluorine, and chlorine based sol-vents. The most common example used in cleaning is CFC-113. Hydrofluorochlorocarbons (HCFCs) are modified CFCswith the addition of hydrogen. The HCFCs were developed asless hazardous replacements for CFCs.

The chlorocarbons have good cleaning properties butunfortunately have toxic vapors, usually with a narcotic effect.The vapors also contribute to smog formation. Chlorocarbonsare volatile organic compounds (VOCs).

The chlorofluorocarbons (CFCs) are less toxic than chloro-carbons, but unfortunately their vapors contribute to ozonedepletion in the atmosphere which can also contribute to glob-


• Synthetic solvents—which use manmade hydrocarbon-based compounds such as CFCs, HCFCs, and PFCs.

• Aqueous cleaners—which use blends of detergent com-pounds with surface active agents together with othercleaning chemicals that use detergency to lift soil from asurface by displacing it with surface active materials thathave a greater affinity for the surface than for the soil.

Soaps—A name stemming from the soapberry, the commonname for about 13 species of deciduous or evergreen trees inthe soapberry family whose fruit contains a soapy substancecalled saponin—a natural cleansing agent produced by thereaction of an alkali, typically sodium hydroxide (NaOH) andanimal fat or vegetable oil. Its use dates at least from the thirdmillennium BC. (In fact, clay tablets in Mesopotamia con-tained a recipe for soap that included potash—potassium car-bonate—and oil.)

The second-century writings of the Greek physician,Galen, referenced soap as a cleansing, medicinal product thathelped to cure skin ailments. Later, the ancient Romansshared their knowledge of soap formulation (sapo, the Latinword for soap is still used to describe the saponifiers oftenadded to today’s synthetic detergents) and by the Middle Agescommercial soapmaking centers were established in suchEuropean countries as France and Spain as well as inEngland. Manufacturing methods were crude, however, untildiscoveries by Nicholas LeBlanc in the 1800s and a centurylater by Michel Chevreul made it possible to make predictablesoap formulations.

Solvents—To understand solvents and their strengths and lia-bilities as cleaning materials, it’s important to understand “sol-vency”—the ability to dissolve. A solvent is usually a liquidsubstance that is capable of forming a physical, homogeneoussolution. Some materials are soluble in certain other materialsin all proportions, while others are soluble only up to a specif-ic percentage and any excess precipitates out of the solution.

Another important aspect of a solvent is its volatility,which is highly related to its boiling point. Solvents that have reasonably low boiling points are more volatile and can be

2 The Aqueous Cleaning Handbook

developing nations to restrict their use and manufacture. Thisagreement known as the Montreal Protocol on Substances thatDeplete the Ozone Layer was signed by 24 countries, includingthe U.S., on September 16, 1987. Today, more than 160 coun-tries have signed the Protocol.

In addition to the above-mentioned compounds, brominat-ed hydrocarbons, dibromomethane (for example, methylenebromine), are also used for cleaning, although on a muchsmaller scale. In addition to immersion, vapor degreasers areoften employed with these types compounds in industrialcleaning, but their mechanical action can be viewed as sec-ondary because of their excellent solvating properties.

In an effort to continue the use of CFC-related compounds,hydrochlorofluorocarbons (HCFCs) were developed. These aregenerally less toxic than chlorocarbons, and have less ozonedepleting potential than the CFCs. Nonetheless, the HCFCshave sufficient ozone depleting potential and global warmingpotential to be of concern to end users.

SEMIAQUEOUS CLEANERSThe acute and chronic toxicological profiles of the aforemen-tioned organic and first-alternative CFC cleaners, coupled withthe negative environmental impact of second-generationHCFC substitutes, stimulated the development of new, innova-tive cleaning techniques and a rebirth of aqueous and semi-aqueous cleaning.

Semiaqueous cleaning incorporates the principles of aque-ous and organic cleaners. This is accomplished by combining asurfactant with a low-volatility hydrocarbon such as a terpene,in particular limonene and pinene (citrus or pine in origin), toform a cleaning blend. Terpenes are homocyclic hydrocarbonsand have a characteristic strong odor; turpentine is an illustra-tive solvent that is a mixture of terpenes. Semiaqueous cleaninginvolves cleaning with a solvent or solvent/water mixture fol-lowed by rinsing with water as in traditional aqueous cleaning.

Unlike traditional vapor degreasing, however, cleaningwith semiaqueous cleaners does not rely on boiling liquids,nor is it restricted to a constant boiling composition. In itssimplest form, semiaqueous cleaning involves using its organ-ic components to dissolve soils and its water component to


al warming. The CFCs are ozone depleting substances (ODS),they have ozone depleting potential (ODP) and they have glob-al warming potential (GWP).

The history of halocarbon chemistry played an importantrole in the development of solvents and synthetic industrialsolvent cleaners—and was used to eventually foster develop-ment of aqueous cleaners as a replacement for environmentalreasons. Carbon tetrachloride (“carbon tet”)—an important,nonflammable solvent for fats and oils, asphalt, rubber, bitu-mens and gums, initially used as a degreasing and cleaningagent in the dry-cleaning and textile industries—was first pro-duced in Germany in 1839 and marketed as a grease remover.Its vapors, however, are highly toxic. Carbon tetra-chloride isalso a volatile organic compound (VOC). Evaporating into theatmosphere at ambient conditions, VOCs include almost allsynthetic and plant-derived solvents as well as fuels. The cal-culation of the amount of VOC in a particular product orprocess is important since ozone, the primary component ofsmog, is affected by VOC emissions.

In the 1890s Swarts discovered that the carbon-fluorinebond could be formed with antimony fluoride and the additionof trace quantities of pentavalent antimony as a fluorine carri-er to form chlorofluorocarbons (CFCs) from chlorocarbonssuch as carbon tetrachloride. Through his work, carbon tetra-chloride also became known as tetrachloromethane, the chem-ical precursor of CFCs—and led to the development of the firstcommercial refrigeration systems some thirty years later.

During the following 50 years, continuous reactor process-es were developed to control the degree of fluorination of thecarbon molecule for the manufacture of refrigerator coolants,some of which exhibited excellent characteristics as a solventand cleaning agent.

There are a number of carbon-derived cleaning com-pounds, including hydrocarbons, halocarbons, chlorofluorcar-bons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluo-roether, and perfluorocarbons (PFCs). While each has its owncleaning advantages, they all have built-in environmental lia-bilities—CFCs, HCFCs and PFCs are believed to contribute toglobal warming. Manufacture of ozone-depleting compoundswas phased out after a world meeting among industrial and


In addition to having a desirable dipole moment that helps dissolve other polar soils, water is capable of bonding tosoils by a mechanism called hydrogen bonding. The ability ofwater to undergo hydrogen bonding is relatively uniqueamong solvents. This additional bond capability gives watersignificant additional ability to dissolve soils as compared withother solvents.

Aqueous cleaners start with water as their basic “solvent”and add ingredients that enhance the ability of water to holdsoils. (The chemistry of, and cleaning mechanisms for, theseingredients are discussed in the next chapter.)

Figure 1A


remove blend-based residues and any other water-soluble soils.Surfactants are used when the water-solubility of the solvent islimited or to improve the emulsifying properties of the cleaner.

AQUEOUS CLEANERSThe first aqueous cleaners were soaps as discussed earlier.Detergents, sometimes referred to as synthetic soaps, werefirst introduced in the 1930s and were found to perform betterthan soaps in hard-water (mineral-laden) applications becausethey contained water softeners to effectively treat dissolvedmagnesium and calcium ions. The development of complexphosphates used to soften water following the Second WorldWar increased the cleaning power of these detergents.

Aqueous cleaners are synthetic detergent cleaning agentsused in a water solution. Water, considered by many to be the“universal solvent,” is an important component of aqueouscleaners because it dissolves many types of soils. Water—which may be municipal tapwater, or deionized or distilledwater based on the cleaning application—also functions as acarrying medium for detergent compounds. But while water iscapable of dissolving many inorganic and some organic conta-minants, not all soils dissolve readily in water. For this reason,aqueous detergent cleaners are complex mixtures specificallyformulated to create greater chemical and mechanical clean-ing action.

Water is a polar solvent that is good at dissolving a widerange of polar soils. Water has a unique “V” shaped structurewith two hydrogen atoms at the top of the “V” and an oxygenat the bottom (see figure 1A). One can think of the oxygen asbeing a large, dense electron rich atom. This gives the entirewater molecule an overall net negative, electron-rich end atthe base of the “V” (d-) and an electron-poor positive end (d+)of the molecule towards the hydrogen top of the “V.” Thisdirectional net-negative charge towards the base of the “V” iscalled a dipole moment. Polar molecules such as water have adipole moment.

This dipole moment is important because it allows stablesolutions of other dissolved polar-soil molecules to becomearranged in more thermodynamically stabile alternating posi-tive and negative ends of molecules (fig. 1B).


Figure 1B

H (∂+) H (∂+)

O (∂-)Water Molecule (H2O)

Partial Positive Charge

Partial Negative Charge

Dipo

le M

omen

t

H (∂+)

H (∂+)

O(∂-)(∂+) (∂-)

Water Dissolved Polar Soil

H (∂+)

H (∂+)

O (∂-)

Water

The electronegativity that attracts electrons toward Oxygen (O) and away fromHydrogen (H) gives water an electrical polarity or dipole moment

Simplified three body model showing possible stabilized arrangement of polarsoil molecule with water molecules with dipole moments arranged negative topositive

CHAPTER TWO

The Chemistry ofAqueous CleaningBefore reviewing the technologies and processes involved inaqueous cleaning, it is important to understand how aqueouscleaning works, and this begins with the cleaner itself.

Aqueous cleaners are typically composed of surfactants foremulsifying, wetting, and penetrating; builders for neutraliz-ing water hardness interference, chelating of inorganic soils,and saponification of natural oils; and additives for corrosioninhibition, anti-redeposition, and rinsing.

KEY DEFINITIONS OF AQUEOUS-CLEANER INGREDIENTSSurfactant—Short for “surface active agent,” it is an organicmolecule with a hydrophobic (water-hating/oil-loving) end anda hydrophilic (water-loving) end. Surfactants are often emulsi-fiers, wetting agents, and dispersants (see other definitions).The most common surfactant is sodium Linear AlkylbenzeneSulfonate (called LAS for short). The alkylbenzene portion ofthe molecule is the hydrophobic/oleophilic end of this surfac-tant and the negatively charged sulfonate molecule is the hy-drophilic end of the molecule. Surfactants are typically classi-fied as anionic, nonionic, and cationic. The class of surfactantdetermines the class of the cleaner.

Anionic surfactant—This is a surfactant that has a negativelycharged end of the molecule that gives it the hydrophilic partof the molecule. These negatively charged parts of the mole-cules are usually sulfonates, sulfates, or carboxylates, that are

The Chemistry of Aqueous Cleaning 9

Today, aqueous agents are used in the same wide range ofindustry applications as solvent cleaning systems. Many aque-ous cleaners now offer comparable or better cleaning perfor-mance to solvent-cleaning systems without using volatile sol-vents, or hazardous chemicals and without appreciable ozone-depletion potential. By switching to appropriate aqueouscleaning technologies now, it is possible to both eliminateozone-depletion potential and eliminate changes which maybe required under volatile organic compound (VOC) restric-tions associated with The Clean Air Act Amendments and stateor local VOC restrictions.

REFERENCESC. LeBlanc, The Evolution of Cleaning Solvents, Precision Cleaning, May

1997, p. 11–16.D. Noether, Encyclopedic Dictionary of Chemical Technology (VCH

Publishers, 1993).F. Swarts, Bull. Acad. R. Belg. 24, 309 (1892).H. Clauser, Materials Handbook, Thirteenth Editor (McGraw-Hill, 1991).National Center for Manufacturing Sciences, Focus (April, 1993).United Nations Environment Programme, Report of the Technology &

Economic Assessment Panel (1991).L. Manzer, The CFC-Ozone Issue: Progress on the Development of

Alternatives to CFCs, Science, Vol. 249 (6 July 1990).Shell Solvents: The VOC Challenge (Houston, TX, SC: 212–94).Toxics Use Reduction Institute, Surface Cleaning Series Fact Sheet No.

SC-2. HCFCs and Cleaning (University of Massachusetts, Lowell, MA01854-2866, 1996).

U.S. Federal Register, Vol. 61, No. 173 (Thursday, September 5, 1996).Toxics Use Reduction Institute, Surface Cleaning Series Fact Sheet NO.

SC-1, Surface Cleaning (University of Massachusetts, Lowell, MA01854-2866, 1996).

Toxics Use Reduction Institute, Handout, Hands On Cleaning andDegreasing Workshop, (University of Massachusetts, Lowell, MA01854-2866, 1996).

U.S. Environmental Protection Agency, Solvent Alternative Guide, (SAGE,version 2.1).

A.S. Davidsohn and B. Milwidsky, Synthetic Detergents, chapter onDevelopment of the Detergent Industry.

RESOURCESwww.alconox.comwww.cleantechcentral.com www.colin-houston.com


organic molecules) that are electrostatically attracted to par-ticulates, creating a bridge between the water and the waterinsoluble solid particulate (in some cases even repelling thesolid surface to help lift the particles into suspension).

Emulsifiers—These cleaner ingredients help emulsify water-insoluble oils into solution by helping to create a liquid-liquidmixture. Surfactants that use their hydrophobic (water-hatingor repelling) or oleophilic (oil-loving) end of their molecule tomix with water-insoluble oils and their hydrophilic (water-lov-ing) end to mix with water create a bridge to emulsify water-insoluble oils into solution. The specific structure of the bridgeis called a micelle that can be thought of as a hollow, oil-filledround ball with a skin made of surfactants with theirhydrophilic ends facing out in contact with the water solutionand the hydrophobic ends facing in to the oil-filled ball.

Wetting Agents—These are surfactants that lower the surfacetension of water and allow the cleaning solution to wet sur-faces and penetrate into, under and around soils and surfacecrevices. They create a bridge between the water and anyhydrophobic (water-hating or repelling) surface. You can thinkof a wetting agent as having one end of the molecule attractedto the surface while pulling the water solution towards the oth-erwise water-repelling surface, allowing the water solution tobe in contact with more of the surface that needs to be cleaned.

Builders—These cleaner ingredients react with interferingcalcium, magnesium, or iron ions that may be present in thewater solution. They stop them from reacting with soils andother detergent ingredients to form water insoluble and diffi-cult-to-clean calcium, magnesium, or iron salts. These metalsare present to varying degrees in all water, particularly tapwater. Builders are usually alkaline salts, chelating agents,and/or sequestering agents.

Alkaline salt builders—These are inorganic salts such as sodi-um carbonate or sodium phosphates. They react with calcium,magnesium, or iron to form water soluble or water dispersiblecompounds that tie up the calcium, magnesium, and iron.


usually neutralized by positively charged metal cations such assodium or potassium. Examples include sodium alkylbenzenesulfonates, sodium stearate (a soap), and potassium alcoholsulfates. Anionic surfactants are ionic and are made up of twoions—a positively charged usually metal ion and a negativelycharged organic ion.

Nonionic surfactants—These are surfactants that have noions. They derive their polarity from having an oxygen-richportion of the molecule at one end and a large organic mole-cule at the other end. The oxygen component is usuallyderived from short polymers of ethylene oxide or propyleneoxide. Just as in water chemistry, the oxygen is a dense elec-tron-rich atom that gives the entire molecule a partial net-neg-ative charge which makes the whole molecule polar and ableto participate in hydrogen bonding with water (as discussed inthe first chapter). Examples of nonionic surfactants are alco-hol ethoxylates, nonylphenoxy polyethylenoxy alcohols, andethylene oxide/propylene oxide block copolymers.

Cationic surfactants—These are positively charged moleculesusually derived from nitrogen compounds. They are not muchused as cleaning agents in hard-surface cleaners because ofthe tendency of the cationic positively charged molecule to beattracted to hard surfaces (that usually have a net-negativecharge). Many cationic surfactants have bacteriacidal or othersanitizing properties that are useful in creating disinfectantsthat leave a cationic disinfectant film on the surface. Cationicsurfactants are usually incompatible with anionic surfactants,because they will react with the negatively charged anionicsurfactant to form an insoluble or ineffective compound.

Amphoteric surfactants—Those surfactants that change theircharge with pH. They can be anionic, nonionic, or cationicdepending on pH. Usually, any one amphoteric can be any twoof the three charge states.

Dispersant—This is a cleaner ingredient that helps disperse orsuspend solid particles in solution. Dispersants include water-soluble surfactants or water-soluble polymers (long-chain


concentration, and the temperature of the cleaning formula-tion. The surfactant lifts oils off the metal surfaces to form asuspended oil-water-surfactant emulsion which is thenremoved by rinsing.

Typically, immersion cleaning involves submerging parts ina bath and providing air agitation, turbulation, and mechani-cal brushing or ultrasonics to realize desired levels of cleanli-ness while spray cleaning uses a pressurized wash stream tocreate even higher soil-removal rates.

Cleaning is then followed by water rinsing. In most aque-ous cleaning systems, more water is used in rinsing than incleaning. Also, rinse water must be purified by a recycling sys-tem to a higher level than the detergent solution. Rinse wateralso requires different separation equipment, since the rinsewater is the last solution to touch the surface being cleaned.

The chemical and mechanical action involved in aqueouscleaning is actually a number of processes. These can bedescribed as:

• Solubilization—a process whereby the solubility of asubstance is increased in a particular medium

• Wetting—to lower surface and interfacial tensions sothat the cleaner penetrates small spaces while gettingunder the soil to lift it from the substrate

• Emulsification—creating an oil/water mixture by coat-ing of oil droplets with surfactant to keep them fromrecombining and migrating to the surface of a cleaningbath (see previous emulsifier discussion)

• Deflocculation—breaking down soil into fine particlesin order prevent agglomeration by dispersing themthrough the cleaning medium

• Sequestration—reacting with ions such as calcium,magnesium, or heavy metals to prevent the formation ofinsoluble byproducts (such as soap scum)

• Saponification—alkaline hydrolysis of fat by the reac-tion of fatty acids with alkalies to form water-solublesoaps

To encourage such chemical and mechanical cleaning(unlike organic and chlorinated solvents, aqueous cleanersmay not depend on solvent penetrability for their cleaning effi-


Chelating agents—These are negatively charged or oxygencontaining molecules that react with positively charged metalions to form a stable complex. They have multiple locations inthe molecule to react with multiple positive charges that maybe present on multivalent metal ions that have more than onepositive charge on them. An example of a chelating agent isEDTA, ethylene diamine tetraacetic acid. EDTA has four aceticacid groups giving it a potential for four negatively chargedacetates to bond with up to four positively charged sites inmetal ions with multiple positive charges, such as calciumwhich has two (2) positive charges associated with it.

Sequestering agents—These are chelating agents (see above)that bind particularly tightly with metal ions and sequester orseparate them from reacting with other compounds.

Detergents use both chemical and physical action to clean,which are affected in turn by temperature, time, type of mechan-ical action, cleaner concentration, and additives. Mechanicalaction is provided by immersion, spray, or ultrasonics.

The detergents’ chemical action saponifies certain oils,producing water-soluble soap material. The surfactants usedin a cleaning formulation then work to physically reduce thesurface tension of the solution, in the process emulsifying andlifting soils away from the substrate being cleaned. These sur-factant molecules can be both free and aggregate forms calledmicelles, and their ratio is based on the type of surfactant, its

HOW ALKALINE CLEANERS WORK


• Saponifiers—Alkalies that react with fatty acids in oilsto form soaps. Chemistry may be mineral (sodium orpotassium) or organic-based (such as solutions ofethanol amines).

• Solvents—Aqueous or organic chemistries designed toenhance the removal of oily soils by dissolving them(e.g., glycol ethers, ethylene [Butyl Cellosolve], andpropylene compounds).

• Additives—act primarily as contaminant dispersants,anti-redeposition agents, brighteners, viscosity modifiers,antifoaming agents, and corrosion inhibitors or they mayhave special detergency on a specific soil type. Examplesinclude enzymes, amine compounds, and various poly-mers.

• Sequestering agents—produced as powders or liquidsto combine with calcium, magnesium, and other heavymetals in hard water. They form molecules in whichthese ions are held securely, or sequestered, so that theycan no longer react undesirably with other species insolution. Polyphosphates and polyacetates are commonlyused.

• Chelating agents—employed to solubilize hard watersalts so that they remain in solution. Produced in bothpowdered and liquid forms, they do not degrade or losetheir potency at elevated temperatures, which make themideal for aqueous cleaning. However, they can interferewith the ability of other chemicals to remove emulsifiedoils and dissolved metals from solution, which can leadto waste disposal problems. In addition to EDTA, nitrilotri acetate (NTA) is also used.

• Corrosion Inhibiting agents—are often added to aque-ous cleaners to minimize their effect on metal substrates.They are used for cleaning at high pH and as rustinhibitors to prevent the rusting or oxidation of cleanedparts (or cleaning equipment that is not constructed ofstainless steel).

• Stabilizers—added to extend the shelf life of detergentingredients and to maintain the uniformity of detergentblends. For example, dilute cleaner solutions may have atendency to grow microbes. The presence of biocidal


ciencies), aqueous cleaners may include a number of the fol-lowing ingredients, formulated to provide maximum cleaningeffectiveness for specific for various types of substrates andsoils by reducing surface tension, forming emulsions, and sus-pending insoluble particles for removal in the cleaning bath:

• Surfactants—alkaline surfactants that react with fattyacids to form soap. They improve cleaning action byreducing the water’s surface tension which also allowsfor greater penetration or wetting of the liquid onto thepart surface. Used to either emulsify a soil from a sub-strate or increase the surface’s wettability. Substanceswith both hydrophilic (water soluble) and lipophilic (oilsoluble) groups that may be cationic, anionic or nonionicdepending on the charge of the hydrophilic end. Anionicsurfactants are generally poor cleaners because of theirnegative charge. Cationic or positively-charged surfac-tants are water soluble and are commonly used inimmersion cleaning. Nonionic surfactants with nocharge are used for surface cleaning when a lower-foam-ing detergent is required. A class of synthetic com-pounds, nonionic surfactants are prepared by attachingethylene oxide molecules to water-insoluble polymers,but are usually biodegradable in aqueous cleaners. Inaddition to wetting, surfactants can also enhance theemulsifying and dispersing properties of a cleaner.

• Builders—inorganic salts that provide alkalinity andbuffering capacity common to almost all aqueous clean-ers (pH may be alkaline >7, neutral ~7, or acidic <7).Alkalinity may be provided by hydroxides, carbonates,borates, silicates, phosphates, or zeolites (crystallinehydrated aluminosilicates). Builders also soften water orhelp with saponification or deflocculation.

• Emulsifiers—substances that can form liquid-liquidmixtures (e.g., oil and grease) that do not dissolve inwater. Emulsifiers are useful for low soil loading, buttheir concentration in a detergent limits bath life.Separation of soil and cleaner may be accomplished bymaking the emulsion unstable by lowering the pH and/ortemperature. They are chemically similar to the semi-aqueous cleaners described below.


to aid in cleaning. Less foam is generally produced with theuse of a neutral cleaning agent. There are also semiaqueouscleaners which form neutral solutions upon dissolving oremulsifying in water.

The first issue in selecting a cleaner on the basis of pH(there are other factors, as we’ll see in later chapters) is howfast it needs to work. Most cleaners are alkaline in naturesince hydrolysis—and the chelation and dispersing of soils—typically occurs most effectively at alkaline pH levels.However, the higher the pH the more corrosive the cleaner:

TYPE OF CLEANER pH RANGE SOILS REMOVEDMineral-acid cleaner 0-2 Heavy scalesMild acid 2-5 1/2 Inorganic salts, water, and soluble

metal complexesNeutral 5 1/2 to 8 1/2 Light oils, small particulatesMild alkaline 8 1/2-11 Oils, particulates, filmsAlkaline 11-12 1/2 Oils, fats, proteinsCorrosive alkaline 12 1/2-14 Heavy grease/soils

Alkaline cleaners work best when the soil can be hydro-lyzed (typically natural oils and fats, fingerprints, naturalgreases, some types of food products, and protein residues).The cleaning process should be enclosed to avoid exposurehazards. (Workers should use personal protective equipmentwith handheld sprays.)

Time, temperature, and agitation also play important rolesin cleaning. But while maximum detergency is achieved athigh temperatures with high agitation over long periods oftime, the substrate must be robust since corrosion is also afactor.

As a rule of thumb, it is best to use the mildest cleaner possible.


additives in a formulation may be indicative of a formu-lation that is not concentrated (assuming the cleaner isnot designed as a biocidal cleaner). In contrast, couplingagents and hydrotropes that are included in detergentformulations are indicative of highly concentrated for-mulations because these are used to increase the solubili-ty and costability of various active detergent ingredients.

• Extenders—fillers which are added to detergent that donot improve detergency (and which also tend to increasethe packaging and handling costs associated with thecleaner itself). For example, water may be added to aconcentrated cleaner, or inert powders may be added todilute a concentrated powder cleaner. It is occasionallynecessary to add a small amount of inert powders asprocess aids in order to improve the freeflowing charac-teristics of a powdered detergent. However, one needs tobe careful not to purchase a cleaner that is diluted withexcess, cheap inert powder, since these types of extendersdo not improve detergency and also increase packagingand handling costs.

TYPES OF AQUEOUS CLEANERSIt is important to keep in mind that a cleaner’s pH value canhave a direct effect on cleaning effectiveness. Technicallyspeaking, pH is the “negative log of the hydrogenion concen-tration.” This means that the higher the pH, the greater the in-crease in hydroxide concentration and the faster hydrolysis—the breaking down of a natural fat or oil into a soap—occurs.

Aqueous cleaners are classified according to pH value asbeing neutral, acidic, or alkaline on a scale of zero to 14, witha pH of 7 being neutral. Thus, a pH value of less than seven isconsidered acidic, and higher than seven, alkaline.

Each detergent formulation has maximum effectiveness ata specific pH value. An acidic solution with a pH of 4.5, forexample, would be effective for removing metal oxides or scaleprior to pretreatment or painting. And an alkaline (basic) solu-tion with a pH of 13.5 could be formulated to remove carbona-ceous soils, heat scale, rust, oil, and grease. Neutral cleaningsolutions include alcohols and other water-soluble formulas,and generally contain detergents or other surfactant additives


CHAPTER THREE

Aqueous-CleaningProcessesBefore testing aqueous cleaners, it is important to understanda few basic processes regarding their use. The major variablesin cleaning using aqueous methods include:

1. Precleaning handling2. Cleaner 3. Agitation 4. Temperature5. Cleaning time 6. Rinse used7. Drying method8. Postcleaning handling

The way parts and substrates are handled prior to cleaningcan have a significant impact on their degree of difficulty incleaning. Soils can be more difficult to clean if they are:

• Allowed to dry, set up and cross link • Stored in a dirty environment • Stored in a humid or corrosive environment.

As a rule, it is important to clean parts as soon as feasibleafter they are soiled. In some instances it makes sense to takeparts directly from a manufacturing process and put them intoa soak solution where they may be able to sit for extendedperiods of time prior to cleaning.

Alternatively, parts can be placed in protective packaging,dipped in a protective coating or immerse in oil or grease tokeep them in a state that will not increase the burden on thecleaning process.

Aqueous Cleaning Processes 19

REFERENCESPersonal interview, University of Massachusetts at Lowell, Toxics Use

Reduction Institute.Alkaline Cleaner Recycle Handbook, Membrex, Inc., Fairfield, NJ, 1994, p.

5.Ibid., pp. 4–5. Ibid., pp. 3–5. Closed-Loop Aqueous Cleaning, University of Massachusetts, Toxics Use

Reduction Institute, Lowell, MA, 1995, p. 6.Ibid, p. 10.Salinas, M. “Water Works.” Parts Cleaning, Vol. 1, No. 2; July/August,

1997.Seelig, S.S.”Making Aqueous Systems Work.¸” CleanTech ’97 Proceedings,

Witter Publishing, May, 1997.Quitmeyer, J. “All Mixed Up: Qualities of Aqueous Degreasers.” Precision

Cleaning, Vol. 5, No. 9; September, 1997.Rolchigo, P.M. and Savage, G. “The Fundamentals of Recycling Alkaline

Cleaners Using Ultrafiltration.” CleanTech ’96 Proceedings, WitterPublishing, May, 1996

Davidson A S & Milwidsky B, “Synthetic Detergents, 7th Ed.” LongmanScientific and Technical copublisher John Wiley & Sons, New York,1987

RESOURCESwww.alconox.comwww.stepan.comwww.pilotchemical.comwww.rhodia-ppd.com


erly if the temperature is hot enough. You need to know theminimum temperature at which to use these cleaners.

Finally, there are controlled foam cleaners that usuallyhave limited foam suppressing capabilities. The surfactantsthemselves do not foam excessively, but they will not be ableto control much foam that results from soils.

It is critical that the detergent be scientifically formulatedto clean effectively and to rinse away without leaving interfer-ing residues. A scientifically formulated detergent will typical-ly have appropriate surfactant ingredients and nondepositingrinse-aids. The surfactant should have sufficient surface ten-sion lowering properties to assist in proper rinsing. A surfacetension below 35 dynes per centimeter for the cleaning solu-tion as used is often sufficient for the surfactant to contributeto good rinsing. Nondepositing rinse-aids can help complete aformulation to meet the rinsing requirements of critical clean-ing.

In addition, the detergents should be manufactured withappropriate quality-control procedures. In many critical-clean-ing applications it is desirable to choose a detergent that haslot number tracking and can be supplied with certificates ofanalysis from the manufacturer. These certificates documenteach lot of detergent to assure consistency and quality controlfrom lot to lot in order to control for potential cleaning failuredue to inconsistencies in manufacturing or unannounced for-mulation changes. It is desirable to choose a detergent from amanufacturer that maintains quality control on their rawmaterials and in turn keeps retained samples of each lot ofdetergent that is used to be able to respond to concerns abouta particular batch.

The detergent should be widely available and economicalto use (for optimum economy, a concentrated detergent is typ-ically used at 1:100 to 2:100 dilutions). The detergent concen-trate should be diluted according to the manufacturer’s in-structions; typically, warm (about 50°C) or hot (about 60°C)water is used. Ambient temperature water may be acceptable,especially for presoaking. For difficult soils, very hot watershould be used (over 65°C), and the recommended detergentconcentration doubled.


CLEANERThe cleaner or detergent used should be matched to thedesired cleaning method, and the surface and types of soilsbeing cleaned. For instance, a low-foaming detergent shouldbe used for spray or machine cleaning, a good anti-redeposi-tion detergent for soak and ultrasonic cleaning, a high emulsi-fying and wetting detergent for manual cleaning. The deter-gent, temperature, and degree of agitation should be strongenough to remove the soil to the desired level of cleanlinesswithout harming the substrate being cleaned.

There are some particularly critical aspects to understandin selecting and using a low- or nonfoaming detergent forspray or machine washing. It is very important to not havefoam when cleaning in or with a machine that relies on spray-ing for mechanical agitation.

Foam may build up and spill over from the machine creat-ing a mess. Foam will also build up on the substrate and inter-fere with the mechanical cleaning energy of the spray. Andfinally, foam may get sucked into recirculation pipes causingproblems with pumps in the machine. Foam is formed by thepresence of agitation at an air/solution interface when a foam-ing agent is present.

Surfactants are often foaming agents. Most aqueous clean-ers have surfactants in them. There are three basic types ofaqueous cleaners that are suitable for machine washing: clean-ers with no surfactant, cleaners with a nonfoaming surfac-tants, and cleaners with low- or controlled-foam surfactants.There are important differences among these types of clean-ers. Remember that foam forms in the presence of an agitatedfoaming agent where air is present. Many soils are foamingagents. In particular, soap formed by saponifiers in electronicsolder flux cleaning is a foaming agent. A surfactant-freecleaner will not protect against foam formed by soils. Youshould only clean nonfoaming soils with surfactant-free clean-ers. A nonfoaming cleaner usually has a nonionic polymer sur-factant. These surfactants have a unique property of comingout of solution at elevated temperatures and forming an oilslick on top of the solution. This oil slick is a barrier to aircontact which stops foam from forming or being stable. Thesecleaners will suppress foam from soils. They only work prop-


Cleaning time can be accelerated by increased agitation,more aggressive detergents, and by increasing temperature. Ifagitation, detergent, or temperature cannot be increased—per-haps because the substrate is too delicate or the proper equip-ment is unavailable—then one must be prepared to use longercleaning times to achieve the desired cleanliness. While manu-al cleaning may take minutes, and spray cleaning might eventake seconds, soaking for hours, or even overnight, may berequired to reach similar levels of cleanliness.

There are some instances when long cleaning times maypromote substrate corrosion, weakening, or swelling. The opti-mum cleaning time should be chosen relative to the specificsubstrate, temperature, cleaning method, and detergent.

RINSE USEDWith aqueous cleaning, the last thing to come into contactwith the cleaned surface is the rinse water. A thorough rinsewill remove soils which have been cleaned from the surfaceand any residue from the detergent itself. Whatever contami-nants are present in the rinse water to begin with can be pre-sent after rinsing. Therefore, the more stringent the cleaningrequirement, the greater the need for rinse water purity.

The important consideration is to remove whatever conta-mination or residues are present to levels that will not inter-fere with the further use of the parts or equipment.

• Standard critical cleaning. A thorough tap water rinsefollowed by a deionized water or distilled water rinse isusually sufficient. In general, a thorough rinse meansrinsing with at least three times the amount of rinsewater as the cleaning solution used, (for example, aspray washing cycle of five minutes should be followedby three rinse cycles of five minutes each in a spraywashing machine).

In soak or ultrasonically agitated rinsing, it is desir-able to have two counterflow-cascade rinse tanks withdripping “over the tank” for reduced dragout. Higher lev-els of cleaning may require the exclusive use of deion-ized or distilled water and in some cases more than threetimes the volume of rinse water.


AGITATIONAgitation can be a form of nonagitation (such as soaking), orperformed through manual (cloth, sponge, brush), ultrasonic,flow-through clean-in-place (for pipes, tanks and tubes), spraycleaning (a dishwasher, for example), and high-pressure spraycleaning. In general, the more agitation, the more effective thecleaning on bulk soils.

Cleaning often can be enhanced by presoaking, particular-ly if soils are dried or baked onto the part to be cleaned. It isalways desirable, whenever possible, to clean prior to soilsbecoming dried or baked onto surfaces.

Different agitation methods are often chosen with (1) timerequired and (2) number of parts being cleaned as the majorconsiderations. If large numbers of parts must be cleanedquickly, then a fast, high-agitation method such as spray wash-ing often is used with an aggressive detergent. For smallernumbers of batch or batch-continuous quantities of parts,ultrasonic soak cleaning with a milder detergent may be used.

TEMPERATUREIn general, higher-temperature cleaning solutions result in bet-ter cleaning. In practice, there is typically an optimum temper-ature for a given combination of cleaning variables. Manysoak, manual, and ultrasonic cleaning methods work best, forexample, at 50˚C to 55˚C. Many spray washing techniqueswork best at 60˚C to 70˚C. Waxy or oily soils are more easilycleaned at somewhat higher temperatures. Particulate soilstend to be more easily cleaned at slightly lower temperatures.

These are, of course, broad generalizations. It is not alwaysnecessary or practical to clean at the optimum temperature.You may have both waxy and particulate soils present, or thepart being cleaned may not be able to withstand the optimumtemperature.

CLEANING TIMEIn general, the longer the cleaning time, the more thoroughthe cleaning. Many cleaning mechanisms such as emulsifying,dissolving, suspending, and penetrating are time-dependent.Up to the point where cleaning has been completed, the longerthey’re employed, the more cleaning is accomplished.


aqueous-cleaner solvent replacement system is evaluated onthe basis of the drying process. Equipment cost and process-ing speed are also factors when large volumes of ultrapure rin-sewater are required to remove small amounts of residue.

There are two basic methods for drying substrates in aque-ous cleaning: physical drying and chemical drying. Physicaldrying consists of evaporation, forceful drying, and absorp-tion, or a combination of these. Chemical drying includes sol-ubilization (using a water-soluble solvent to dilute the water)and displacement (using a surfactant-based solvent that isinsoluble in water). While these are usually faster than physi-cal methods, they are not inherently environmentally safe. Inaddition, proper operation must be followed to realize costsavings and ensure health and safety.

Removing water by evaporation is the oldest and simplestphysical drying process. Convection ovens do just that. Wetparts are placed into an oven and heat is applied to remove thewater. Two problems are inherent with such drying solutions:

• Convection or microwave ovens are not always applica-ble due to space and time constraints or lack of automa-tion.

• Some types of parts are heat sensitive and others may betoo big or too dense, requiring large amounts of energy,to be efficiently dried by convection oven.

Mechanical systems for physical drying may be classifiedby the following types:

• Vacuum drying—similar to convection drying—requiresa negative pressure to be applied. This causes a decreasein the water’s boiling point in order to “suck” away themoisture. This method is ideal for removing trappedwater from blind holes and crevices but may also deformthe part. Also, shorter drying times are balanced out byhigher energy requirements. As with evaporation drying,an important consideration is that any contaminationcontained in the water will be left behind on a cleanedsurface. Multiple rinsing chambers with hot ultrapurewater may not be sufficient to remove these residues andwould add significantly to the time and cost involved.


• Electronic component and circuit board cleaning.Deionized water is preferred rather than tap water ordistilled water because deionized water has less potentialfor metallic cation deposition which leave conductiveresidues on sensitive electronic components. On metalparts, the use of deionized rinse water reduces the likeli-hood of depositing calcium, magnesium, and otherwater-spotting salts.

With soak or ultrasonically agitated rinsing, it isdesirable to have two counter-flow cascade rinse tankswith dripping “over the tank” to reduce dragout. In allcases, running water or otherwise agitated rinse is betterthan a static soak-tank rinse.

Higher levels of cleaning may require the exclusiveuse of deionized or distilled water and in some casesmore than three times the volume of rinse water.

For most cleanroom, electronic component, and cir-cuit board cleaning, deionized water is preferred overeither tap or distilled water because of its lesser potentialfor metallic cation deposition on sensitive electroniccomponents, leaving conductive residues. On metalparts, the use of deionized rinse water reduces the likeli-hood of depositing calcium, magnesium, or other waterspotting salts.

DRYING METHODDrying can affect residues and corrosion since impurities fromrinse water can be deposited during evaporation. Water, par-ticularly high-purity rinse water, can be corrosive to metalsubstrates during heated and air drying. The use of physicalremoval or drying techniques or the addition of corrosion in-hibitors (with the tolerance of corrosion inhibitor residues) tothe rinse water can help minimize such corrosion.

With aqueous systems, adequately drying any remainingwater from a part is critical to avoid corrosion of metals, par-ticulates sticking to surfaces, poor paint adhesion, short-cir-cuiting of electronics, and problems related to cross-contami-nation in food, beverage, and pharmaceutical processing. Thislast step in the manufacturing process is important both to theend user and detergent supplier since the performance of an


• Absorption—Moisture absorbing materials (corncobs,drierite) are cheap, simple, environmentally safe, andreusable for many drying applications. They are usuallytumbled with the cleaned parts to increase contact withthe water. Delicate parts may be damaged during tum-bling and the drying agents themselves may further cont-aminate the parts. Also, complex geometries with blindholes cannot be dried adequately.

The important thing to remember here is that not all dry-ing processes are applicable in every situation. As with select-ing an aqueous cleaner, the right drying process must be care-fully assessed based on the parts being cleaned and manufac-turing volume.

POSTCLEANING HANDLINGThe way in which parts and surfaces are handled after clean-ing can impact their cleanliness. For this reason it is impor-tant to consider how parts are handled and stored to ensurethat the purpose of the cleaning process is maintained.Depending on the environment, it may be advisable to makeprovisions for a clean storage place or conditions. It may beappropriate to determine how long a surface or part will stayclean while stored to determine if it needs to be re-cleanedprior to use.

DETERMINING PART DRYNESSInspection is probably the most common method for deter-mining dryness. For most precision cleaners, the observationof no visual wet spot constitutes a “dry” part. Tapping theparts on a brown paper towel will immediately indicate ifthere is trapped water. If any solvent is present, the wet spotwill disappear very quickly. A more thorough test for measur-ing remaining water involves using reagents found at anychemical supply house, solubilizing the water in methanol,and performing a relatively simple titration.

CLEANING METHODSThere are ten types of mechanical cleaning methods used inaqueous cleaning and each is employed—sometimes in combi-


• Forced-air, or blow-drying—a relatively old concept forremoving water. A more advanced method is the use ofan “air knife” that forces clean, dry air through a long,narrow chamber onto the substrate. Parts on a conveyorsystem pass under this intense stream of air and thewater is simply blown off. Parts, however, must beangled just right for water-soluble residues to beremoved and streaking to be avoided. Complex geome-tries, nestled parts, and high production volumes arealso difficult problems, and noise may also be of con-cern. Large volumes of clean and dry air are required fordrying to be successful. Automation may be easilyaccomplished, but batch processing is more difficult forthis type of drying system.

• Centrifugal drying—uses gravitational forces to removewater. Large volumes of parts and blind holes are han-dled easily; however, this approach is difficult to auto-mate and delicate parts may be damaged.

• Forced or filtered hot gas—combines convection heat-ing with an air knife and offers the advantages of evapo-rative and blow-drying actions. In humid situations,however, moisture can condense on the substrate, result-ing in wet parts. Forced drying is environmentally safeand can handle large volumes of work. Air knives dry rel-atively fast compared to most physical methods of dry-ing. They can also be economical and allow for automa-tion.

Forced/filtered gases can be used to effectively dryparts, particularly in batch process systems where clean-ing tanks are employed. After a tank is drained it con-tains wet parts where dry gas (such as dry nitrogen, oreven heated dry nitrogen) is forced through the closedchamber to dry the parts. This same principal can beused in a separate drying chamber in which a dry gas isalso used to evaporate the water and sweep any watervapor away from the parts. Particular attention shouldbe paid to the quality of the gas being used. Typically, fil-ters are employed on the incoming gas—with a filter sizeappropriate to the size of particulates which must beeexclude from the surface.


Of the two methods, spray clean in place uses far less solutionand can be more efficient.

Typically, the cleaning solution is circulated slowly for atleast one-half hour—with several hours required for large sys-tems. Displace the cleaning solution by pumping in one fullsystem capacity of water. Then complete rinsing by circulatingand draining at least two times the systems water capacity. Forspray clean-in-place, a low foaming detergent is used, followedby rinsing and flushing thoroughly.

• Ultrasonic—Ultrasonic cleaning is used for larger num-bers and repetitive batches of parts. To clean in an ultra-sonic tank, a solution is made up in a separate container,the ultrasonic tank filled, and the machine run for sever-al minutes to degas the solution and allow the heater toreach the correct temperature. Small articles should beplaced in racks or baskets; irregularly shaped articlesaligned so that the long axis faces the ultrasonic trans-ducer (usually the bottom); the machine should run 2–10minutes until parts are clean. A thorough rinse follows.

• Machine—Machine washing is used for cleaning largequantities of components. The machine’s directionsshould be consulted for details on proper use. In general,the parts are loaded on racks with open ends facing thespray nozzles. Narrow-necked parts should be placed inthe center of the racks, preferably on specificallydesigned spindles with spray nozzles directed into thenecks. Small articles should be grouped in baskets toprevent dislodging by spray. Avoid loading parts touch-ing each other where possible. Only low foam detergentsdesigned for these machines should be used. Typically,10 g or 10 mL of detergent per liter of hot, wash-cyclewater (approximately 60˚C) is used.

• Power Spray Wand—Commonly called a power washer,it consists of a pressurized tank with hot water and/orsteam that is connected to a hand-held wand. The wandwill have a trigger to release the hot water or steam andusually has a detergent metering device or injectiondevice to meter in detergent during spraying.


nation—for specific types of substrates, parts, and cleaningvolume factors. They include:

• Manual—Manual cleaning is used to clean small batchesof parts and surfaces. To clean manually, the article to becleaned should be wetted either by immersing it in thedetergent solution, or by using a soaking cloth orsponge. For nonabrasive scouring, undiluted detergentshould be poured onto a wet cloth or sponge for scrub-bing. A cloth, sponge, brush, or pad can be used forcleaning. A thorough rinse follows. Protective gloves andeye protection should be worn if recommended orrequired.

• Immersion/Soak—Soaking is used to clean small itemsand the insides of larger vessels. It should be used as apretreatment to prevent soils from drying onto a part.Soiled parts can be placed in a soak tank until such timethat they can be washed. Soaking is also effective toclean or pretreat very difficult, dried-on residues. Toclean by soaking, a detergent recommended for soakingshould be used, and a detergent soak solution made upaccording to the directions. The article should be com-pletely submerged to prevent any deposits or etching atthe air/solution interface. Soils should be soaked untilthey are removed; this may take several hours. Somesoils may require additional agitation or wiping in orderto remove them. A thorough rinse follows.

• Clean-in-Place (CIP)—Clean-in-Place is used to cleanpipes, tanks, and filtration systems. Its chief advantage isthat, as its name implies, it assures clean systems with-out disassembly. It requires, however, good circulationfor effective cleaning.

There are two main clean-in-place methods:

• Circulate clean-in-place—which involves filling atank and system with solution and circulating itthrough the system.

• Spray clean-in-place—which involves partially fill-ing the system and circulating the cleaning solutionthrough spray nozzles.


pense detergent and rinse water. There is a class of PCboard washer that is called a conveyorized or continuouswasher that has a conveyor belt that carries the boardspast a series of washing spray stations and rinsing sta-tions.

IMPROVING PERFORMANCE BY CONTROLLING EFFICIENCY VARIABLESBy choosing an appropriate cleaning method, using the rightrinsing and drying process, then varying the cleaner, concen-tration, temperature, and time, an optimized aqueous-cleaningsystem can be achieved.

Getting the greatest performance in aqueous critical clean-ing requires controlling the eight important variables thataffect cleaning performance.

1. Precleaning handlingAs a general rule, parts and surfaces must be cleaned promptlyafter becoming soiled to avoid drying and setting up the dirton them. Clean storage conditions for parts, or proper packingof parts by the parts supplier, can make it easier to successful-ly clean parts or surfaces.

2. Agitation/cleaning method Usually the cleaning method is selected first—depending, ofcourse, upon the practical considerations of your cleaningproblem. The cleaning method, in turn, dictates the type ofagitation available. While very large items or large quantitiesof items with less critical throughput requirements may behandled in large dip tanks, critical items—and their volume—will determine the type of cleaning procedure.

Examples:• Small items—Cleaning by hand with cloth, sponge, or

brush agitation may be acceptable for items that aresmall in volume and size.

• Important items—You may want to clean in ultrasonicimmersion tanks for items requiring more controlled,reliable, and reproducible cleaning that is less subject tohuman error.


• Washer/sanitizer—A high temperature washingmachine usually larger than a home dishwasher; it hasracks where devices to be cleaned are placed with veryhot water used during cleaning to give some thermalsanitation. Versions of these machines that are used incleaning medical instruments may even have pressureseals and use high pressure steam to achieve higher tem-peratures for higher degrees of disinfection.

• Glassware Washers—Glassware washers are used forwashing laboratory glassware. They are usually availablein small under counter sizes that are approximately thesize and dimension of a home dishwasher, or a variety oflarger floor standing models for cleaning higher volumesof glassware. As glassware washers, these will often beconnected to a deionized water source in order to beable to rinse with the deionized water. In laboratorycleaning it is often critical to have a deionized waterrinse to prevent any residue left from the rinse water.

• Parts washers—Parts washers are a class of washingmachinery used in industrial cleaning that covers a widevariety of types of cleaners. These vary from ultrasonicwashers which were discussed previously, to immersionsoak tanks, to elaborate agitation machines havingimmersion tanks with bubbles running through them orwith some kind of inert media that is vibrated insidethem with a solution, to variations on the washer sanitiz-ers or glassware washers as discussed above. If you aredealing with a machine called the parts washer it can beimportant to determine which kind of parts washer it is.If it is a parts washer which relies on spray agitation orpressurized spray as in a glassware washer or washersanitizer, then you need a low-foaming detergent. If it isa ultrasonic cleaner or an agitation under immersioncleaner you may be better off with those detergents suit-able for those kinds of cleaners.

• PC Board Washer—Like glassware washers these typi-cally come in under counter sizes, and floor standingmodels for larger numbers of boards or larger sizes ofboards. These are usually spray wash machines that haveracks mounted inside them with spray nozzles to dis-


4. Drying methodYou can dry by physically removing rinse water or by evapo-rating rinse water. Physically removing by wiping, blowing,centrifuging, drying fluids, or other physical removal tech-niques will remove the rinse water before it has a chance toevaporate. Such methods avoid precipitating out any impuri-ties or salts that may be present in the rinse water.

Evaporation drying methods such as air drying, heat dry-ing, and vacuum drying can potentially deposit any non-volatile impurities present in the rinse water. Note that vacu-um drying can evaporate a wide range of impurities that arenonvolatile at room temperatures.

5. Cleaner type and concentrationDetergents should be compatible with the cleaning methodand effective on the soils you are removing—one that will notdamage the substrate you are cleaning.

Choose a cleaner with the appropriate combination ofcleaning functions for your soil that will perform well withyour cleaning method.

6. TemperatureChanging this variable gives the most dramatic results.Generally, the higher the temperature, the faster and more effi-cient the cleaning. For cleaning mechanisms that have first-order reaction kinetics (such as emulsifying, saponifying, anddispersing), an increase of 10˚C (18˚F) will double the rate ofcleaning.

High temperatures are particularly important inmachine/spray washing where a droplet of solution only has asplit second to react with the soil before the next droplet ofcleaning solution displaces it from the surface. High tempera-tures also help remove soils such as wax or silicon oil that typ-ically can only be softened at temperatures above 170˚F inconjunction with a high-emulsifying cleaner. It’s important tonote, however, that high temperatures are not always desir-able. They must be balanced against a commensurate increasein corrosion.


• Large quantities—May also dictate the use of ultrasonicimmersion cleaning, batch-parts washers, or mechanicalwashers.

• Very large quantities—Parts with rapid throughputrequirements may require conveyor-type spray washers.

3. Rinse procedureRinsing methods are usually dictated by practical considera-tions that are compatible with the cleaning method you havechosen.

It is also important to use sufficient rinse water to assurecomplete soil and detergent removal. For basic crude cleaning,two volumes of rinse water for every volume of wash watermay be sufficient; for higher level cleaning three or more vol-umes of rinse water are usually required.

Agitated or running water is always preferable to stagnantsoak rinsing. It is important to choose rinse water that is freeof problem residues.

Be aware that the rinse water is the last thing to touch theitem you are cleaning. Whatever is in the rinse water can endup on your surface. The substrate and application for yourparts also help determine the type of rinse water.

Examples:

• Electronic components—Use ion-free deionized waterfor components that are conductive ion sensitive.

• Pharmaceutical, medical device, optical, and coatingapplications—Use organic-free distilled or reverse-osmosis water for organic, film-sensitive compounds orparts.

• Manufacturing—Use low calcium/magnesium softwater, deionized water, or distilled water to avoid calci-um/magnesium water spot deposits.

If the purified water is expensive to use, you can often getby with an initial regular tapwater rinse followed by a final,purified-water rinse. Another way to minimize rinse waterdeposits is to dry by a water-removing method rather a water-evaporating one.


Keep in mind, however, switching from an immersion- ormanual-cleaning method to a spray-cleaning method, mayrequire reconsidering the choice of detergent. This can beimportant in a validated cleaning environment—where afuture change in cleaning methods will also add additionalconcerns for validation. Therefore, at a smaller volume, it isoften wise to use a cleaning method that can be scaled up tohigh-volume manufacturing, if this level of output is anticipat-ed.

The following are the predominant cleaning methods:

• Manual cleaning—typically chosen for small-volumebatch cleaning. The levels of cleanliness that can beachieved by manual cleaning are actually very high,although the operator determines the consistency ofcleanliness. For consistent manual cleaning, rigorousoperator training and retraining needs to be considered.Well-written cleaning procedures and training proce-dures should be provided for—even going go so far as tocertify operators in different cleaning methods with peri-odic recertification.

• Soak cleaning—usually chosen for small quantities ofparts when there is sufficient time in which to cleanthem. Soaking is not labor intensive, although it is typi-cally a slow process. Care should be taken in choosing asoak method of delicate parts are being cleaned. Due tothe longer times involved in soaking, there is also moretime for corrosion due to interaction between the sur-face being cleaned and the solution used to clean it. As aresult, soaking is best suited to small volumes of robustparts where time is not terribly important.

• Ultrasonic cleaning—particularly effective on smallparts with blind holes and crevices that are inaccessibleby spray cleaning. This process is essentially soak clean-ing enhanced by ultrasonic sound energy. This greatlyaccelerates the speed of cleaning and can greatlyimprove cleaning in small spaces or crevices. Ultrasoundhelps with dispersing and mass transfer of the cleanerand the replenishing of fresh cleaning solution to thesurface of the parts being cleaned. Ultrasonic cleaninginvolves more expensive equipment and is typically suit-


Also, many materials require using only the highest tem-perature that will cause no harm to a substrate. Examplesinclude plastics, which often cannot be cleaned above 70˚C(160˚F), aluminum not above 60˚C (140˚F), and proteins notabove 55˚C (130˚F).

7. Cleaning time and concentrationAbove a certain minimum concentration of detergent, dou-bling the detergent concentration may only give a 10%increase in ability to remove soil and a 25% increase in bathlife. Beyond a certain minimum cleaning time, doubling thecleaning time may only give a 10% increase in ability toremove soil. The minimum concentration and the minimumlength of cleaning time may be around 25% of a typical con-servative recommendation from a detergent manufacturer.

To optimize your system, bracket the cleaner manufactur-er’s recommendation and then increase or decrease the time,temperature, concentration, and agitation according to yourneeds, recognizing that decreasing any one of these variablesmay require increasing the others. In many cases dropping thetemperature significantly can result in cleaning performancedecreases that cannot be made up for by increasing time, agi-tation, or cleaner concentration.

8. Postcleaning HandlingProviding for clean storage or clean packaging in which to putyour clean parts or surfaces can help maintain them in a cleanstate.

SELECTING A CLEANING METHODThe choice of cleaning method is determined by the quantityof parts to be cleaned, their configuration, the cleanliness levelthat needs to be achieved, and the budget available for equip-ment.

Often a cleaning method choice is based on volume, forexample, manual cleaning for small volumes. As the volumesor quantity of the parts or surfaces being cleaned increases,immersion cleaning system, possibly even including ultrasonicagitation, may be indicated. As the parts and volumes increasefurther still, some form of high-volume spray cleaning applica-tion will be required.


BATH-LIFE EXTENSION AND CONTROLFor the highest levels of critical cleaning only freshly made upsolutions should be used for cleaning to avoid any potential forcross contamination. For industrial critical cleaning applica-tions high levels of cleaning can still be achieved with extendedbath life. In general, a pH change of 1 pH unit towards neutralindicates an exhausted cleaning solution. Bath life can also beextended by physical filtration of particulates and cooling andsettling of sludge and skimming of oils. Bath life can also beextended by adding one half as much detergent of the initialload after partially depleting the cleaning life of a bath. Underfrequent daily use, detergent solutions can rarely be used morethan a week even with these bath life extension techniques.Conductivity, pH and, % solids by refractometer can be used tocontrol bath detergent concentration.

Free alkalinity titration can also be used to control bathlife of alkaline cleaners where the soil being cleaned depletesfree alkalinity—as is often the case with oily soils. The process:

• Titrate a fresh solution to determine new-solution free-alkalinity.

• Titrate the used solution to determine the percent drop infree alkalinity.

• Add more detergent to the bath to bring the free alkalini-ty back to the new solution free alkalinity. (For exampleif the initial solution is made up with 100 ml of cleanerconcentrate and a 25% drop in free alkalinity isobserved, try adding 25 ml of cleaner concentrate torecharge your solution.)

Perform a new free-alkalinity titration to confirm therecharge the first few times this recharging method is used tobe sure that the detergent being used is linear with respect tofree alkalinity depletion. This form of bath life extension can-not run indefinitely, sludge will eventually form. Fresh solu-tions must be made up periodically.

Bath lives can be controlled to extend them by using con-ductivity. Most cleaners have conductive salts in their ingredi-ents, which are detectable by conductivity. By knowing theconductivity response of the detergent, the depletion of thoseconductive salts can be measured.


able for somewhat larger volume batches where a higherlevel of cleaning is required.

• Clean-in-place by circulation system—typically usedfor piping or small tank systems where a spray clean inplace system can not used or in filtration systems wherethe filters being cleaned can not be accessed by spraynozzles.

• Spray clean-in-place—typically used in larger tank sys-tems where the efficiency achieved by less solution usagewarrants the cost of installing the spray system. Thespray cleaning of tanks can also give more reliable, com-plete coverage of the tank. (Also, an immersion cleaningsystem may have difficulty cleaning the top of a tank,requiring additional manual cleaning.)

One must keep in mind when choosing which method touse for cleaning tanks that a detergent that performs well forsoak cleaning may not perform as well in spray cleaning.Therefore, if it is anticipated that a process will ultimately bescaled up to a spray clean-in-place system, it may be wise toconsider using a spray-cleaning detergent that will also performadequately in soaking operations.

The choice of a cleaning machine depends on the batch andsize of the pieces being cleaned. As batch volumes move upfrom those that may be best addressed by ultrasonics, it oftenmakes sense to employ some form of cabinet, under-counter, orfloor standing washer.

For very high-volume parts washing, a conveyorized system,whereby parts are placed on a conveyor and are cleaned withspray nozzles as they pass through the conveyor cleaning sys-tem, may be appropriate.

Spray cleaning systems are very good for parts and surfacesthat are readily accessible to the spray. They are not as good atdealing with blind holes and small crevices. For instances whereyou have higher volumes of parts where it makes sense to usespray cleaning, you should investigate spray under immersion.

For cleaning very, very large parts (where an operator canphysically move around the part, for example, vehicles or verylarge assemblies) it makes sense to use a power spray want orhandheld pressure spray device to clean part exteriors.


Many cleaner manufacturers can supply the curves ofdetergent concentration versus conductivity. By adapting thesecurves to your conditions and measuring the conductivity, de-tergent depletion and dilution by make-up water can be deter-mined. This determination can be used to figure out howmuch detergent to add to the cleaning solution to restorecleaning performance. Typically this kind of measure andrecharge can be carried out through several iterations.

Keep in mind, however, the bath will ultimately reach apoint where it forms sludge (or where some other failuremechanism occurs), at which time the bath must be dumpedand a complete batch of new cleaner employed. The time todump the bath and start over is often defined as being after acertain number of parts or length of time as determined usingsome sort of cleanliness measurement. The conductivity willtypically not detect the point of cleaning failure, but will onlydetect concentration of cleaner present, whether depleted ornot. The following table gives specific examples of concentra-tion vs. conductivity for some specific Alconox-brand cleaners.Using the data below one can derive the concentration ofdetergent from measured conductivity. Note that conductivityis very temperature dependant and detergent solutions do nothave the same slope as many default settings on temperature-correcting conductivity meters. For best results, allow hotdetergent solutions to cool to a consistent temperature forcomparison.

TABLE CONDUCTIVITY (Ms) VS CONCENTRATION OF ALCONOX, INC CLEANERS AT 22 DEG CConcentration Alconox Alcojet Terg-a-zyme Alcotabs Liquinox Citranox Detergent 8 (uS) Det-o-jet

0.125% 1.136 1.354 1.184 1.011 0.108 0.195 21.00 0.614

0.250% 2.08 2.51 2.21 1.912 0.213 0.327 29.70 1.275

0.500% 3.83 4.6 4.1 3.48 0.402 0.475 41.60 2.58

1.000% 6.99 8.34 7.51 6.36 0.747 0.682 63.30 5.05

2.000% 12.71 15.02 13.65 11.55 1.38 0.987 87.60 9.68

4.000% 22.6 26.6 24.3 20.8 2.63 1.47 106.40 18.17

CORROSION INHIBITIONCorrosion during cleaning is accelerated by the same thingsthat accelerate cleaning: heat, aggressive chemicals, time, andagitation. To reduce metal corrosion concerns (in approximate

order of importance) use less heat, lower pH detergents, andshorten cleaning time and agitation.

In general, use the mildest pH detergent to limit metal cor-rosion. Higher pH detergents may have metasilicate corrosioninhibitors that often allow it to be used successfully to cleansoft metals such as aluminum. In general, to reduce plasticcorrosion, use less aggres-sive cleaners that have less solventor surfactant character or use lower concentrations of thosecleaners, use lower cleaning temperatures, use less contacttime, and finally, use less agitation.

With aqueous cleaning, metal corrosion can occur duringrinsing and drying. Corrosion inhibitors can be added to rinsewater provided that any associated inhibitor residue does notinterfere with the surface being cleaned. Keeping the surfacescleaned hot by using hot rinse water and by using rapid heator vacuum drying can accelerate drying and minimize metalcorrosion. Forced air drying and air knives that physicallyremove rinse water can also minimize corrosion, as well asdrying with hot oxygen-free gas such as nitrogen.

With mild steel one can have “flash rusting” when rinsingwith hot water and drying with hot air. In some instances, low-ering the water temperature or drying temperature can helpavoid corrosion on mild steel. For instance, in a case whereflash rusting on mild steel had been occurring due to using150°F rinse water and ambient air drying, it was found thatflash rusting could be avoided by using 120°F rinse water inplace of the 150°F rinse water.

REFERENCESAlconox Cleaning Solutions Newsletter, Vol. 1, Number 3 “Improving

Performance—Controlling the 6 Big Efficiency Variables.Alconox Guide to Critical Cleaning, Cleaning Procedures section.Drying Systems, Appropriate Drying Technology Completes Successful

Cleaning from Precision Cleaning, December 1997, p. 37.Variables and Vitals of Metal and Electronics Aqueous Cleaning article

by Malcolm McLaughlin, Precision Cleaning, January 1994.

RESOURCESwww.alconox.comwww.cleanersolutions.org.www.corrosionsource.comwww.clean.rti.org

Aqueous Cleaning Processes 3938 The Aqueous Cleaning Handbook

Selecting an Aqueous Cleaning Detergent 41

CHAPTER FOUR

Selecting an Aqueous-CleaningDetergentThe major requirement in cleaning electronic parts, assem-blies, precision parts, and metal surfaces is that there be noresidues that interfere with further use or processing of thecleaned surfaces. The cleaning method should be noncorrosiveto the component and the detergent chosen should exhibitexceptional free-rinsing qualities.

Critical cleaning requires careful selection of cleaningchemistry and methods to ensure adequate performance with-out sacrificing either worker safety or benign environmentalimpact. Current solvent cleaners may have ozone-depletingpotential or Clean-Air-Act-Amendment-regulated volatileorganic compounds (VOCs). Current corrosive mineral acid orcaustic cleaners may present worker exposure hazards andenvironmental disposal problems. The use of appropriateaqueous cleaners can replace the use of volatile organic andozone- depleting compounds for cleaning. In addition, suitableaqueous cleaners can be milder and easier to dispose of thanmineral acid or caustic cleaners.

In practice, it is important to be able to choose from arange of detergents to find one that performs well with thecleaning method and is suitable for the soils and surfaces needed to be cleaned. (See Table 4A) Key considerations include:


Selecting an Aqueous Cleaning Detergent 4342 The Aqueous Cleaning Handbook

Finally, particulate soils are best removed by disper-sant cleaners that can lift them into solution and form asuspension. Very small particulates, for example submi-cron particulates, need to be cleaned by a very high wet-ting, low surface tension cleaner that has the ability tolower the boundary layer between the surface and thesolution down to submicron distances to allow the agita-tion in the cleaning solution to access the submicronparticulate.

• Part complexity—Are there severe undercuts, blindholes, or numerous part cavities? Higher-powered wet-ting detergents with low surface tension may berequired.

• Level of cleanliness required—If the part being cleanedor the manufacturing process does not require excep-tionally high technical specifications for cleanliness,harsh, toxic cleaning agents can often be avoided.

• Manufacturing process—For example, if a part arriveswet at the cleaning station, an aqueous chemistry maybe best.

• Cleaning efficiency—As a rule, cleaning efficiencyincreases with time, temperature, and agitation, thougheach may affect other important considerations such asfoaming, costs, health, or safety.

• Environmental considerations—The environmentalimpact of cleaning operations can often be minimized orreduced by selecting the most appropriate aqueouscleaning agent, and appropriate cleaning and/or recy-cling system.

• Type of substrate—Metal (ferrous/nonferrous), glass,plastic, rubber. For example, substrates such as magne-sium, aluminum, and similar metals may be attacked bysome types of chemicals. Stainless steel alloys, on theother hand, often have a high resistance to both acidsand alkalies.

• Type of soil—What type of soil is it? Heavy or light,organic or inorganic, oil or particulate matter. This isperhaps the single most important question to ask whenyou are selecting an aqueous detergent. Heavy soilsrequire heavy-duty detergents or cleaners to re-movethem. The detergent should have a high concentration ofcleaning ingredients to give it a high capacity for remov-ing soil; typically heavy soils require very aggressivecleaners. A heavy soil may often be best handled by ahigh dispersing cleaner that is able to move bulk quanti-ties of soil without having to react chemically with eachindividual molecule of soil.

Light soils require a detergent that matches the exacttype of soil in order to be able to most completelyremove them. If you have a light soil it is more impor-tant to know more about what kind of soil it is so thatyou can go from a surface that is almost clean to a sur-face that’s extremely clean or meets your level of cleanli-ness. For example, many organic soils have limited watersolubility. These oily soils are often best cleaned by ahigh emulsifying cleaner. An inorganic soil again may ormay not be water soluble, but if it is not water soluble itis often able to be removed by chelation using a deter-gent that has a good dose of chelating agent or it may beable to be made water soluble by reacting with an acidcleaner by some of the acid solubilization mechanismswhich have been discussed in the detergent chemistrychapter. Oils are often readily cleaned by the same typesof cleaners that remove organic soils. Silicon oils are aspecial subset of oils that are very difficult to remove.They require a very high emulsifying cleaner and usuallyvery high temperatures to be removed. Silicon oils arefound in things such as mold release agents.


usually loosens all the soil from the surface and then therinse water needs to sweep it away. In residue-free clean-ing it is important to use a nondepositing rinse aid.Many rinse aids are positively charged compounds thatare attracted to a surface that repels the water from thesurface. This can leave what appears to be a nice cleansurface, but in fact it will be covered with the hydropho-bic water repelling rinse aid.

3. Is the detergent recommended for the desired clean-ing method? (See previous discussion.)

4. How hazardous is it? For example, is it highly alkalineor acidic, presenting a personal health hazard? Is it cor-rosive? Does it present a reactivity hazard with soils? Isit a flammable or volatile solvent? These considerationscan be evaluated by reviewing a Material Safety DataSheet for the agent. Preferably, it should not contain anyhazardous ingredients listed on the OSHA standard andHazardous Substance List 29CFR 1910 subpart Z.

5. Can it be disposed of easily? Any detergent chosenshould be readily disposable and biodegradable, contain-ing no RCRA Hazard Classification or EPA PriorityPollutants designation. Otherwise, the use of hazardouscleaners may require special, expensive waste-handlingtreatment.

6. Is it environmentally friendly? Considerations includeozone depletion potential and volatile organic compound(VOC) content regulated by the Clean Air ActAmendments. Approval under anticipated future restric-tions should be weighed as well.

7. How economical is it? The detergent should be widelyavailable and affordable. For optimal economy, a con-centrated detergent is typically used at 1:100 dilutions.

In choosing an appropriate detergent, one must considerthe equipment it is being used to clean; the level of cleanlinessand residue removal that is necessary; the cleaning methodthat is to be used; and the performance of the detergent. Keyquestions to ask about selecting a cleaner are:

• Does it have fillers? There are a number of ways to tell

TABLE 4A DETERGENT CLEANING APPLICATIONS AND METHODS

DETERGENT SELECTION Today’s aqueous critical-cleaning detergents are blended forspecific applications—substrates, degrees of soil load, andcleaning process used. Here are a few questions to ask about adetergent brand to ensure that it meets your specific cleaningneeds:

1. Does it have good detergency on the types of soilsthat you need to remove? A broad range of organicand inorganic soils are readily removed by mild-alkalinecleaners that contain a blend of surfactants and seques-tering agents. Metallic and inorganic soils are oftenreadily solubilized by acid cleaners. Proteinaceous soilsare effectively digested by protease enzyme cleaners.

2. Is it free-rinsing? Will it rinse away without leavinginterfering detergent residue? A properly formulateddetergent will contain rinse aids to help the rinse waterremove the detergent and soil solution. Rinsing is a criti-cal part of high-performance cleaning. The detergent

Metalworking and PrecisionManufacturingClean parts, avoid volatile solvents, strong acids, and other hazardous chemicals.

ElectronicsAvoid conductive residues, avoidCFCs, pass cleaning criteria.

Glass, ceramic, porcelain, stainless steel, plastic, rubber. Oils, chemicals, particulates.

Aluminum, brass, copper, and other soft metal parts. Oils, chemicals, particulates.

Inorganics, metallic complexes, trace metals and oxides, scale, salts, buffing compounds.

Silicone oils, mold-release agents, buffing compounds.

Metal oxides, scale, salts. Metal brightening.

Circuit boards, assemblies, screens, parts, conductive residues, resins, rosins, fluxes, particulates, salts.

Ceramic insulators and components.

Manual, Ultrasonic, Soak, C-I-P*

Machine washer, power wash


Parts washer, power wash


Parts washer, power wash


Parts washer, pressure spray


Parts washer spray

Manual, Ultrasonic, Soak

Machine washer, power sprayboard and screen washers


Parts washers

Mild alkaline

Low-foam alkaline

Mild alkaline

Inhibited low-foam alkaline

Mild acid

Low-foam mild acid

High-emulsifying, mild alkaline

Low-foam alkaline

Mild acid

Low-foam mild acid

Nonmetal-ion, Nonionic

Low-foam nonmetal-ion, Nonionic

Mild alkaline

Low-foam alkaline

Application RecommendedKey Concerns Articles Cleaned/Soil Removed Cleaning Method Detergent

*Clean-in-Place by circulating, for spray clean-in-place see machine washer detergents.


MONEY SPENT ON CLEANING AGENTS PER YEAR

HEALTH/SAFETY CONSIDERATIONS Human health and safety considerations include detergenttoxicity, corrosivity, reactivity, and flammability. These consid-erations can be evaluated by reviewing a Material Safety DataSheet for the solvent, chemical, or detergent with which youintend to clean. The detergent(s) you choose for your applica-tion preferably should:

• be formulated to minimize health-safety concerns whilestill offering outstanding cleaning performance

• not contain any hazardous ingredients listed on theOSHA standard and Hazardous Substance List 29CFR1910 subpart Z

• not have flash points or stability hazards.

Many detergents strong enough to remove fingerprints,can remove oils from skin and, therefore, have the potential todry out skin and cause “dishpan hands.” This is especially trueof detergents designed for machine spray washing which, inorder to perform in the limited contact time afforded duringspray cleaning, are considered to be aggressive cleaners.Protective neoprene, butyl, rubber, or vinyl gloves are recom-mended for any extensive manual cleaning operation. In addi-tion, many detergents are potential eye irritants, and shouldnot be used without eye protection. See Chapter Eleven,

whether the powder or liquid brand you’re consideringcontains any excess fillers and is optimally concentrated.

— What are the ingredients? Powders: When selecting a powdered brand, look atthe label, technical bulletins, and MSDS to see if itcontains any sodium chloride or sodium sulfate com-pounds which do not perform a useful cleaning func-tion but merely add to volume and weight (and ship-ping costs).

Liquids: With liquid detergents, the most commonfiller is water. It is important, however, that no morewater is used than necessary to ensure a good solu-tion, maintain stability, and prolong shelf life.

— What is the concentration? Powders: It is rare that a detergent will require morethan a 1 percent solution of detergent to water(1:100).

Liquids: A typical alkaline cleaner should not need tobe used at a dilution of more than 1:100. And, semi-aqueous or solvent-containing cleaners may reason-ably need to be used at dilutions of 2:100 or more.

• What are the operating costs? Operating costs for aqueous cleaners are generally lowsince these cleaners are usually concentrated—typicallyusing only one to five percent of cleaner solution towater. Also, aqueous cleaning baths last a relatively longtime without recycling.

Strong acid cleaners generally require constant sys-tem maintenance since their aggressive chemistry canattack tank walls, pump components, and other systemparts as well as the materials to be cleaned. (Inhibitorscan be used to reduce such attack.) Another disadvan-tage of strong acid cleaners stems from soil loading—particularly metal loading—which requires frequentdecanting and bath dumping, leading to relatively highoperating costs compared with alkaline cleaners.

In contrast, alkaline cleaners are often more economi-cal compared to acid chemistries, because they do notcause excessive maintenance problems.

$10,000-$50,00035.5%

Under $10,00046%

Over $50,00018.5%

Source: Precision Cleaning Magazine, December, 1996.


REFERENCESAqueous Cleaning Chemistries, Precision Cleaning, December 1996, p. 22.Selecting An Aqueous Cleaner by Malcolm McLaughlin, Precision

Cleaning ’97 Proceedings.

RESOURCESwww.alconox.comwww.cleantechcentral.comwww.clean.rti.orgwww.cleanersolutions.org

“Environmental Health and Safety Considerations,” for furtherdiscussion.

ENVIRONMENTAL CONSIDERATIONS Environmental considerations include concern over volatilesolvents with ozone-depleting potential and volatile-organiccompound content that is regulated by The Clean Air ActAmendments. Any detergent chosen should be biodegradableand readily disposable, and contain no RCRA Hazard Classifi-cation or EPA Priority Pollutants.

Surfactants are not generally viewed as a menace to theenvironment. Nonetheless, their environmental attributesoften receive as much attention as their technical propertiesand economic aspects. One reason may be the mental imagemost people have of foaming streams and rivers, formed overthree decades ago, has not faded entirely. This foam resultedfrom non- or poorly-biodegradable surfactants which are nolonger used in modern aqueous cleaner formulations.

Then, too, public environmental awareness has increasedmarkedly in recent years. In fact, environmentalism has tran-scended from a social attitude to an almost metaphysical level,or at least to a position that compares with spirituality. A largeportion of the public wants to “do the right thing,” environ-mentally speaking. To this end, regulations are enacted andproducts are being designed and marketed. We have enteredthe age of environmental marketing and are forming attitudesabout environmental attributes, sometimes without adequatecomprehension of the scientific disciplines that are required.

Much of the discussion of the environmental acceptabilityor preferability of surfactants centers on the standard againstwhich measurement is made and on the designation of what isenvironmentally important.

Both the issues of health and environmental safety areimportant and extremely complex. Again, for a more completedescription for health, safety and environmental issues seeChapter Eleven.

Testing and Selecting a Detergent and Cleaning System 51

CHAPTER FIVE

Testing and Selecting A Detergent and Cleaning SystemTesting and selecting an aqueous cleaning system involves aseven-step process:

1. Identify the key reason you are developing the system.

2. Select an evaluation method that will allow determi-nation that key cleaning criteria are satisfied.

3. Select a test cleaning system that includes a cleaningmethod, rinse method, and a drying method.

4. Select a test substrate for cleaning.

5. Select a test soil and method for applying the test soilto the test substrate.

6. Select an aqueous cleaner for evaluation.

7. Perform tests and optimize your selected system.

IDENTIFY REASONS FOR CHANGING CLEANING SYSTEMS It is important to identify the key reasons for a new system sothat the selection process satisfies all of the reasons a new sys-tem is desirable. The following table outlines some of the rea-sons for setting up new systems and the kinds of parametersthat must be evaluated for each.


Testing and Selecting a Detergent and Cleaning System 5352 The Aqueous Cleaning Handbook

Information sources—In order to help identify options andthose systems which may work best for you, you may wish toconsult some of the following sources of information. Theseresources should be used to help narrow your search for typesof systems and cleaning chemistries.

Look for information that correlates with your reasons forcleaning and the resulting key considerations.

TABLE 5BInternetAlconox detergent selection and use procedures (www.alconox.com)Precision Cleaning Web (www.precisioncleaningweb.com)Parts Cleaning Web (www.partscleaningweb.com)Toxic Use Reduction Institute (www.cleaningsolutions.org)Research Triangle Institute (www.clean.rti.org)US EPA (www.epa.gov)Pollution Prevention Gems (turi.uml.edu/P2GEMS/)Finishing (www.metalfinishing.com)Waste Reduction (www.owr.ehnr.state.nc.us/ref/00023.htm)

PublicationsCleantech (Witter Publishing, 84 Park Ave,

Flemington, NJ 08822)908-788-0343www.cleantechcentral.com

A2C2 (62 Route 101A, Suite 3, Amherst, NH 03031)Alconox Guide to Critical Cleaning (Alconox, Inc. 30 Glenn St., White Plains, NY 10603)

ConferencesCleantech (WPC Expositions, 84 Park Ave,

Flemington, NJ 08822)908-788-0343www.cleantechexpo.com

TABLE 5A REASONS FOR NEW CLEANING SYSTEMS AND THEIR CORRESPONDING NEEDS FOR EVALUATIONReason Key ConsiderationsWaste treatment concerns Estimate quantity and characteristics of discharge,

reporting status, hazards, permits neededAir pollution concerns Estimate quantity and characteristics of volatile

solvents, current and expected regulatory statusWorker safety Review equipment design and chemical characteristics,

flammability, corrosivity, toxicity, need for protective devices, ventilation, thresholds (TLVs), worker training needed

Improved detergency Review equipment design, rinsing and drying procedures,and cleaner chemical characteristics to see that they fit the type of soil and substrate being cleaned

Improved cleaning speed Review temperature, agitation, chemistry, and drying conditions

Lower cost Review recurring costs of chemistry, waste treatment, disposal, safety, regulatory compliance, maintenance, cleaning time labor, utilities, and capital costs

New process Prioritize and evaluate all of the above, use of existing equipment may be desirable

Organizational considerations—Having identified what isbeing cleaned, the contaminants being cleaned, and the rea-sons for changing or creating a new cleaning process, we mustnext consider the organizational implications of the newcleaning system. In short, who and what will be affected bythe system?

It is important to consider production personnel, supervi-sors, engineering, environmental compliance, purchasing,marketing, public relations, and quality control. It is also help-ful in getting a new process adopted to be able to identify keybenefits to each affected group in a manufacturing organiza-tion. Forming a team with influential representatives fromwithin these groups will help with the ultimate success of theadoption of the new cleaning process.


TABLE 5C MISTAKES TO AVOID IN EVALUATING A CLEANER AS PART OF CLEANING SYSTEM DEVELOPMENTMistake Result CorrectionUse immersion in small A high emulsifying gentler Use a Water Pik®, tanks or beakers to test cleaner will work best, but circulated or cleaners that will be used in will fail in the spray agitation the spray system spray cleaning environment system poured cleaning

solutions to mimicspray cleaning

Use a higher temperature A milder cleaner will give Match than will be available in adequate cleaning that fails temperaturesscale-up at lower tempClean for a longer time A milder cleaner will give Only use available than will be practical when adequate cleaning that cleaning timesyou scale-up fails in shorter timeUse flat substrates when small A system with inadequate Use a substrate tocrevices and blind holes will be agitation will work on flat mimic the scale-uppresent in scale-up surfaces that fails on crevices surface—perhaps

take flat plates pressed together

Use a soil that does not The wrong cleaner may Try to use similarrepresent the real soil be chosen soils for testing

It is often tempting when evaluating a cleaner to put thecleaner in a tank or beaker and dump some of the dirty parts init to see if simply soaking will achieve a modest amount ofcleaning. (Sometimes people also add heat and agitation sothey can get more cleaning from their system.) This is anacceptable bench test only when developing an immersion-cleaning system. Problems often occur with this approachwhen the ultimate intent is to use a spray washer or mechani-cal washer in the scaled-up process. The cleaning mechanismscan be very different in immersion cleaning than from thoseinvolved in spray cleaning. A system that cleans by soaking in abeaker may not work in a spray washing machine.

Immersion cleaning techniques can use cleaners that relyon kinetically slower mechanisms such as emulsifying, enzy-matic hydrolyzing, and dissolving. High-agitation sprayingmechanisms need a cleaner that relies on kinetically faster

SELECT AN EVALUATION METHODOnce the key reasons for testing and evaluating a new cleaningsystem are determined, methods for evaluating the success ofthe new method must be chosen. The literature availableabout the cleaner under consideration should be reviewed forany health, safety, and environmental concerns.

Cleaning performance must also be evaluated through testcleaning. First, determine a baseline level of cleanliness and away of measuring that baseline. (See Chapter Eight for meth-ods to measure cleanliness.) Often visual inspection is suffi-cient for initial development work. A relatively simple gra-vimetric analysis involving weighing a clean substrate beforesoiling, after soiling, and after cleaning to determine percentsoil removal is effective as a measure of cleaning performanceas long as the substrate is impervious to the cleaner. Otherreflective analytical techniques require special equipment tobe used such as Optically Stimulated Electron Emission(OSEE) as well as Grazing Angle Fourier Transform InfraredSpectroscopy (FTIR).

Surface contact-angle of deionized water on a flat surfacecan be used, along with a variety of methods that involveextracting soils from the surface and then performing ananalysis of the extract. As a rule of thumb, the simplestmethod that will provide suitably sensitive results should beemployed.

SELECTING THE TEST CLEANING SYSTEMIdeally, testing of a cleaning system should be achieved usingfull-scale conditions with actual dirty surfaces. In practice,however, this is often impossible. Accordingly, a small, bench-scale system which mimics the full-scale system must often becreated.

In mimicking the actual cleaning conditions for theprocess cleaning method, a rinsing and a drying method mustbe considered. In evaluating a cleaner, it is particularly impor-tant to mimic the time, temperature, and agitation that will beavailable in the scaled-up cleaning process. The followingtable outlines some mistakes when evaluating a cleaner usinga benchtop cleaning system.


The cleaner may not be appropriate for the higher agitationsystem, or the particle sizes of the soil may not be as easilycleaned in higher-turbulence, higher-boundary layer conditions.

Again, when performing bench-scale testing for spray clean-ing systems it is important to mimic the characteristics of theactual cleaning system. For instance, mimic the drenching of asurface by pouring or gently pumping cleaning solution over asurface in order to mimic high volume/low pressure cleaning, ormimic the blasting of a surface using a pump and nozzle orWater Pik®.

It is important to stress that although ultrasonic cleaningcan result in very high localized agitation from the cavitationcaused by the sound waves, the agitation occurs under immer-sion where immersion cleaning mechanisms are still effective.Even spray under immersion can allow for some of the kineti-cally slower immersion cleaning mechanisms to work, althoughthere is much more movement in the cleaning solution thatoccurs during spray under immersion and, thus, kinetically lesstime available for slower immersion cleaning mechanisms.

The following table outlines bench scale cleaning methodsand how they mimic larger-scale cleaning:

TABLE 5D TYPICAL BENCH-SCALE CLEANING SYSTEMS AND THE SCALE-UP SYSTEMS THEY MIMIC

CLEANING METHODSBench-Scale Full-ScaleManual cleaning with tool Manual cleaning with toolImmersion in a small tank Immersion in a big tankSmall tank with stirrer A clean-in-place,

agitated big tankSmall ultrasonic tank (be sure to use Bigger ultrasonic tank same frequencies and power densities)Gently hosing or pouring High volume/low pressure

washer onto a surfacePower spray onto surface Low volume/high pressure

washer

cleaning mechanisms such as alkaline or acid hydrolysis, wet-ting, penetrating, and dispersing. Spray cleaners need to bemore aggressive and faster acting since they have but a fractionof a second to do their cleaning before the next droplet of spraysweeps them from the surface. Immersion cleaning can haveminutes or hours of contact time.

It is possible to test a cleaner that will perform only margin-ally in immersion cleaning but performs excellently in a spray-washing environment. It is also very possible (and even likely)that a cleaner that performs excellently in immersion cleaningwill be very ineffective in a spray washing environment.

In particular, high-foaming cleaners that can work very wellin immersion do not perform well in enclosed spray cabinetwashers where the foam can create a barrier to the mechanicalenergy of the spray, and where the foam may burst the seals ofthe cabinet (and, possibly, cause cavitation in the circulatingpumps).

There is another more subtle difference in spray cleaningsystems where, in simplified terms, one is dealing with twomajor kinds of agitation. There is the high volume/low pressuremethod of spray washing and the low volume/high pressuremethod of spray washing. The first involves gently spraying ahigh volume of cleaning solution over the surface of a substrate,which results in a cascade of solution running down the surfaceto be cleaned. This results in a more nearly laminar flow at thesurface with a smaller boundary layer that allows for a widerrange of cleaning mechanisms and, in particular, the occur-rence of greater small-particulate dispersion.

It is not unusual for what is called a low-foaming or con-trolled foaming cleaner to perform well in such highvolume/low pressure washers. In low volume/high pressurespray washing, there is much greater turbulence and moremechanical energy with cleaning solution bouncing off the sur-faces with less cascading and sheeting action down the surface.In these very high agitation cleaning systems you may need anonfoaming cleaner.

A problem that sometimes occurs is when a perfectly suc-cessful high volume/low pressure cleaning system is changedinto a low volume/high pressure cleaning system in an effort toget faster cleaning cycle times and the system suddenly stopscleaning well.


can remove a particular soil from a surface. For bench-scale testing first choose a cleaning system and

then go on to test the system with a given cleaner. The follow-ing table shows typical bench-scale cleaning methods that areused to make up a cleaning system of cleaning, rinsing, anddrying:

TABLE 5E BENCH-SCALE RINSING AND DRYING METHODS AND THEIR CORRESPONDING SCALE-UP METHODS

RINSING METHODSBench-Scale Scale-UpStatic soak static soakOverflowing dip tank counter flow cascade tanksRunning water running water or efficient

counter flow cascade tank series

DRYING METHODSBench-Scale Scale-UpAir dry Air dryOven dry Hot air dryHair dryer Hot directed forced airCompressed air nozzle Air knifeVolatile solvent rinse Volatile solvent rinse

SELECT THE TEST SUBSTRATEOnce a cleaning method is selected for testing, the next step indeveloping a cleaning system is to select a substrate and a soilto clean. Ideally, actual parts or surfaces with actual soils thatwill be cleaned should be used. Sometimes, of course, this isnot possible, in which case similar materials should beemployed.

Also, small stainless steel coupons or glass slides are oftenused for bench-scale cleaning development. For many soils itis not critical what the substrate is, and for many cleaningmechanisms “a surface is a surface”—whether it be glass ormetal.

When cleaning plastics, however, the surface considera-tions are more critical, since some plastics will have particular

Select rinsing and drying conditions—In any bench-scalecleaning system it is also critical to understand how the rins-ing and drying processes can affect cleaning results. In bench-scale cleaning, it may be practical to use copious quantities ofrunning water for rinsing. Often, simply putting cleaned partsunder running water at a sink will be both acceptable and ahighly effective rinsing technique. The same level of rinsing,however, must be duplicated in scale-up.

The cleaner loosens all the soils and prepares them to berinsed away. A running water rinse is far more effective thanstatic dip-tank rinsing, or even a slow counterflow cascaderinse tank setup. Rinsing relies on essentially two types ofmechanisms:

• Mass displacement—where the rinse water physicallyreplaces the soil/solution mixture.

• Concentration gradient dissolving—where the highconcentration soil/solution mixture at the surface beingcleaned dissolves into the rinse water, creating a uniformlow-concentration mixture with a resulting low concen-tration of soil present near the solution/surface interface.

In a running water rinse system, mass displacement is thedominant rinse mechanism. In a static soak-tank rinse, con-centration gradient dissolving is the dominant rinsing mecha-nism. When testing bench-scale rinsing, mimic the rinsing thatwill be used in scale-up. For example, when using a series ofdip tanks or counterflow-cascade tanks in scale-up, a runningwater rinse may represent a more effective rinse, one thatmight allow the use of a less free-rinsing cleaner to performadequately in the bench-scale process, but cause failure in thescale-up process.

It is also desirable to use the same quality of rinse waterthat will be used in scale-up. If lab-grade deionized water isused for bench-scale rinsing, for example, the same type ofwater should be available for scale-up. (Conversely, it is oftenpossible to use tap water rinses in bench-scale testing—eventhough water spots will result that can be eliminated by usingdeionized water rinses with water removing—as opposed towater evaporating—drying methods.) Tap water rinses areoften sufficient to show in bench-scale that a cleaning system

Testing and Selecting A Detergent and Cleaning System 59


processes, but may become very difficult to remove if it drieson the surface for several hours. (If possible, it may be wise totry to avoid allowing soils to dry onto a surface in the actualcleaning conditions.)

If using the exact soils that will be present during actualcleaning is not possible, try to match the characteristics of thesoil. Match the particulate sizes, oil viscosities, wax meltingpoints, chemical character (for example, do not use a naturaloil to mimic a synthetic or petrochemical oil and vice versa).Try to apply the soil to the surfaces in the same manner andquantity that will be present under actual cleaning conditions.(Soiling the substrate on the heavy side can be helpful in de-signing a robust cleaning system.)

In addition, it may be critical to develop a way of uniform-ly soiling a surface in order to get significant reproducibleresults that are suitable for comparing cleaning systems. Oneapproach is to create a uniform slurry, paste, or solution of thesoil, possibly employing a volatile solvent carrier to apply theliquid mixture to surface, then using a glass rod with spacersto spread a uniform film of soil onto a coupon to achieve uni-form reproducible soil levels.

If the objective is to find a way to absolutely clean a soil—rather than compare cleaning systems—simply smearing orapplying some soil to the surface for visual inspection thatsome soil is present can suffice.

SELECTING AN AQUEOUS CLEANERAfter establishing combinations of cleaning, rinsing, and dry-ing, try a cleaner at different time, temperature, and detergentconcentrations to determine if the system will work. Reviewthe information in Chapter Four on Detergent Selection tomake sure you are testing a cleaner that has a reasonablechance of success. Match the cleaner to the desired cleaningmethod, soil, and surface being cleaned.

PERFORM TEST CLEANINGSIt is advisable to perform at least three cleanings using eachset of conditions to help minimize anomalous results. For crit-ical-cleaning system development, it is desirable to perform atleast six repetitions of each set of conditions.

affinity for organic soils. Also, when removing salts or inor-ganic soils from metals it is often important to use the exactmetal that will be cleaned when a process is scaled-up. Thesame is true for porous surfaces—such as gold and some ce-ramics—which may require use of the same substrate forbench-scale testing in order to develop a reliable cleaning sys-tem.

Similarly, it can also be very important to use the samesurface for testing in order to be sure that the cleaning systemwill not corrode or damage the surface. This is especially truefor aluminum.

It can be very useful to work with standard clean coupons.There are several suppliers of standard coupons that are morecommonly used with corrosion testing, but that can be adapt-ed for use in cleaning testing. Some suppliers include:

Metal Samples Corrosion Monitoring Systems A Division of Alabama Specialty Products, Inc.P.O. Box 8, 152 Metal Samples Rd. Munford, AL 36268(256) 358-4202http://www.alspi.com/msc.htm

Metaspec CO 790 West Mayfield BoulevardSan Antonio, TX 78211 (210) 923-5999

Q-PANEL LAB PRODUCTS 800 Canterbury RoadCleveland, OH 44145PH: (440) 835-8700http://www.q-panel.com

SELECT A TEST SOILIt is often more important to pay attention to the soil than thesurface during cleaning system development—using the samesoil in bench-top testing as in scale-up. Pay careful attention tohow dried-on the soil will be in the actual process. A freshlyapplied soil may be very easy to remove in bench-scale

Testing and Selecting A Detergent and Cleaning System 61

TABLE 5FTypical cleaner test conditionsOverkillDouble the recommended dilution of detergentMaximum practical temperatureMaximum practical cleaning timeMinimum20% of the recommended detergent dilutionRoom temperatureVery short cleaning timeOptimizedRecommended dilution120˚F (50˚C) for immersion or manual cleaning methods, 140˚F(60˚C) for sprayclean systemsPractical cleaning times

Once you have determined an “overkill” system that will workand a “minimal” system that probably partially fails, an opti-mum system can be identified. Decide when to stop bench-scale optimizing and when to move on to pilot-scale or full-scale use of the cleaning system.

REFERENCESGuidebook of Part Cleaning Alternatives, Karen Thomas Massachusetts

Toxics Use Reduction Institute. John LaPlante, Alan BuckleyMassachusetts Office of Technical Assistance, March 1997.

Developing a System, from Alconox Cleaning Solutions, Vol 1, Number 3.

RESOURCES

www.alconox.comwww.clean.rti.orgwww.cleanersolutions.org

Testing and Selecting A Detergent and Cleaning System 6362 The Aqueous Cleaning Handbook

Whether selecting an aqueous cleaner and cleaning systemfor a new manufacturing or processing application or switch-ing to an aqueous cleaner, the process is the same. It is a goodidea to start by using an “overkill” combination of time, tem-perature, concentration, and agitation than might typically berequired in a bench-test scenario to first prove that the systemyou are using is capable of delivering the cleanliness required.

Finding the minimums—Having proven that the system canwork, the next step is to try a combination of what one mightguess is slightly less than minimum time, temperature, con-centration, and agitation to get some idea of where the systemstarts to fail. A good, less-than-minimum starting point mightbe 20% of a conservative recommendation from the cleaner’smanufacturer. For example, if a cleaner is recommended foruse at 1% in water, 60˚C (140˚F) with a 10-minute soak, onemight try and see how badly it fails at 0.2%, 40˚C (105˚F) anda two-minute soak. This may provide a sense for how robust-ness of the cleaning process. One can then choose some com-bination of time, temperature, and concentration above theminimum based on how poorly the system failed to perform.

Based on these results, try a combination based on a guessof what might be slightly above the minimum requirements.One can then optimize the paramaters by successive iterationsof cleaning performance testing by going halfway between thelast combination of variables that worked (and the last combi-nation that failed) until satisfied that the system has been suf-ficiently optimized for the specific cleaning needs.

One can also hold any one or more variables constant,such as a maximum practical length of time, or a maximumsafe cleaning temperature while optimizing the other vari-ables. For example, if one needs to be able to clean a batch ofparts in two minutes, then vary the temperature and concen-tration within the two-minute time constraint.

Industrial Cleaning Applications 65

CHAPTER SIX

Industrial Cleaning ApplicationsToday, new applications for aqueous cleaning are found in awide range of industries—laboratory science, healthcare, phar-maceuticals, food-and-beverage processing, metalworking,and precision manufacturing of glass, plastic, and metal com-ponents.

This chapter describes key considerations in aqueouscleaning for each of these industries.

HEALTHCAREThe ultimate goals of healthcare cleaning procedures are tokeep instruments and equipment clean and sterile, prolong theirworking life, minimize cross-contamination, and reduce med-ical waste. The ideal detergent for getting reusable items cleanhas a neutral-range pH, in order to prevent corrosion or othersurface degradation. When proteinaceous soils from blood orbody fluids must be cleaned, adding enzymes to a cleanermeans the instruments will come clean with soaking and gentlecleaning rather than abrasive scrubbing—thus prolonging theirworking life and decreasing the chance of cross-contamination.

Cleaning in a healthcare setting often means preparing asurface for sterilization. It is very important to have a clean sur-face with no dirt on it so that when a sterilization process is car-ried out you do not wind up sterilizing the dirt—leaving unster-ilized surfaces beneath the dirt. In short, effective sterilizationrequires effective cleaning.

Although healthcare instruments themselves are oftenmade up of robust plastics or stainless steel, the trays they are


66 The Aqueous Cleaning Handbook Industrial Cleaning Applications 67

handled in as instrument kits and are cleaned in are oftenmade of light-duty plastics or aluminum. Therefore, the clean-ing agents chosen must not damage the light-duty plastic oraluminum instrument-handling trays.

TABLE 6A DETERGENT SELECTION GUIDE FOR HEALTHCARE CLEANING

Healthcare instruments that are cleaned are usually exam-ining instruments of one kind or another. Most healthcareinstruments that come into contact with blood or body fluidsare disposed of so as to completely eliminate, or substantiallyreduce, the risk of cross-contamination from blood-bornpathogens. Some reusable examining and probing instruments(such as endoscopes) actually come in contact with blood orbody fluids and must be cleaned very carefully.

Cleaning healthcare instruments varies from cleaningsmall groups of instruments—such as what may be found inan individual doctor’s office or clinic—that are handled insmall soak trays and sometimes cleaned ultrasonically, tolarge-scale central cleaning found in hospitals and large med-ical centers. In control cleaning, the instruments in the entirefacility are grouped in trays and sent to a central cleaning orcentral sterilization facility. These facilities will typically uselarge batch washer/sterilizers to perform their cleaning.

PHARMACEUTICALPharmaceutical process equipment cleaning includes every-thing from bench scale lab production for trial use to full scalemanufacturing of bulk pharmaceuticals. All share the need toclean and document to government regulated standards. Thesestandards are commonly called GMP (good manufacturingpractice) or the update as cGMP (current good manufacturingpractice). There are regulations that need to be complied with

from the US FDA, the EU (European Union), and the Interna-tional Conference on Harmonization (ICH), to name a few.For a discussion of the cleaning validations required underthese regulations see the chapter 8 on cleaning validation. Forexamples of the types of standard operating procedures(SOPs) used in pharmaceutical process equipment cleaningsee the Chapter 7 on cleaning procedures.

The types of residues that need to be cleaned range fromeasy to clean water-soluble excipients to difficultpetrolatum/metal oxide mixtures. To simplify regulatory com-pliance, it is desirable to use as few cleaners as you can toremove the entire range of residues encountered. It is alsodesirable for these cleaners to be effective on a wide range ofresidues used in a wide range of cleaning techniques, frommanual, soak and ultrasonic cleaning to clean-in-place spraysystems.

The materials of construction that typically need to becleaned are glass, 316L stainless steel, Teflon, polypropylene,and silicon elastomers used in seals. In some cases, pharma-ceutical manufacturers will use disposable seals, pipes and fil-ters to avoid having to validate their cleaning. It can be saferand more cost effective to use some equipment once ratherthan clean it.

There is no more demanding application for precisioncleaning than pharmaceutical manufacturing—where cross-contamination can be costly in lost product and the creationof risk to human and animal health.

Today many leading drug companies, as well as firms thatmanufacture medical devices, are finding that aqueous clean-ers provide the same kind of scrupulous cleaning required forprocessing healthcare products. Examples:

• Capsules and tablets—Some pharmaceutical ingredi-ents resist going into solution, making tablet presses anddies difficult to clean. Even stubborn, sustained-releaseproduct residues come clean quickly with appropriateaqueous cleaners.

• Suspensions—Aqueous cleaners also eliminate intensivescrubbing and human contact in cleaning large stainlesssteel tanks (even 2,000 gal) used in manufacturing liquidsuspensions.

HealthcareEffective prepara-tion for steriliza-tion, longer instru-ment life. Minimizecross-contamina-tion. Reduce waste.

Surgical, anaesthetic, and examin-ing instruments and equipment.Catheters and tubes.

Difficult proteinaceous soils, bloodand other body fluids, tissue oninstruments.

Manual, Ultrasonic, SoakMachine washer, sani-sterilizerManual, Ultrasonic, SoakMachine washer, sani-sterilizer

Mild alkalineInhibited low-foam alkalineEnzymeInhibited low-foam alkaline


Industrial Cleaning Applications 6968 The Aqueous Cleaning Handbook

Pyrogens on packaging materials can be controlled byheating alone or in combination with alkali or strong oxi-dizing solutions or by washing with detergent(1)...Pharmaceutical makers can render plastic containerspyrogen-free by washing the containers with an alkaline (iepH 9-10) cleaning agent on a machine integrated with thefilling line. When washing is the pyrogen-removal methodof choice, any cleaning agent residue must be adequatelyremoved...The favored method of removing pyrogens formstoppers is washing... many stopper makers now offer pre-washed stopers, which are treated to reduce endotoxin lev-els by 3 logs. 1

Liqui-nox is certainly a detergent that is used in pyrogencontrol. Most laboratories that do LAL testing for pyrogensuse Liqui-nox to clean their glassware and testing equipment.

Stainless Steel Cleaning—Since stainless steel and glassare common substrates cleaned, it is worth taking a closerlook at some of their surface properties and how that effectscleaning and how to optimize thermodynamics of cleaning bycontrolling the pH of the cleaning solution.

In aqueous critical cleaning there are numerous well-understood factors in detergency affected by pH. Far less wellknown, however, is the role pH can play in harnessing electro-static affects to improve cleaning efficiency. Since like chargesrepel, choosing a cleaner of appropriate pH relative to the iso-electric point of the surface and the pKa (inverse log of theacid dissociation constant, see table 1) of the residue makescleaning far more efficient—especially when cleaning residuessuch as acids, bases, and amphoteric proteins, all of which canhave their electrical charges manipulated by pH.

The isoelectric point of a surface is the pH at which thesurface’s electric charge is neutral with regard to its acid/baseand electron donor-acceptor reactions. Moving to a higher orlower in pH will shift the effective surface charge or electrondensity in a negative or positive direction. Examples:

• Steel—typically has an isoelectric point of 8.5 associatedwith the reactivity of the oxygen in the oxides Fe2O3,Fe3O4, and Cr2O3 on the surface of the metal and thehydrates and hydroxides formed in aqueous solutions.

• Intermediates—Aqueous cleaners are ideal for cleaningglass-lined chemical reactors used in processing pharma-ceutical intermediates such as powders, fillers, bindingagents, and other chemicals.

TABLE 6B DETERGENT SELECTION GUIDE FOR PHARMACEUTICAL CLEANING

In research and development, aqueous cleaners have longbeen used in cleaning metal, glass, plastic, and polymer com-ponents for benchtop labware as well as for difficult-to-cleanpilot processing equipment such as bioreactors and fermenta-tion systems.

Controlling Pyrogens—One of the considerations in phar-maceutical process equipment for parenteral product cleaningis controlling pyrogens. Pyrogens are endotoxins or cellulardebris that can cause fevers if people are internally exposed.

Pyrogens are often controlled using heat. The cleanerLiqui-nox (Alconox, Inc. catalog number 1201) and Alconox(Alconox, Inc. catalog number 1104) are used to depyrogenateheat sensitive surfaces (as well as those treated by standardheat treatment). As standard cleaning with 1% 120 deg F (50deg C) Liqui-nox by manual, soak, or ultrasonic agitation fol-lowed by a thorough rinse with WFI (pyrogen free water—water for injection) and post cleaning handling in a pyrogencontrolled environment or packaging can give adequate pyro-gen control. Stoppers for injectables are cleaned using Alconoxpowdered detergent solutions.

A recent article (Hallie Forcinio, Pyrogen Control, March2001 Pharmaceutical Technology p38) made reference to con-trolling pyrogens with the following:

PharmaceuticalPassing cleaningvalidation for FDAgood manufactur-ing practices.

Product-contact surfaces.

Inorganic residues, salts, metallics,pigments.Protein/ferment residues. R/O, U/Fmembranes.

Manual, Ultrasonic, Soak, C-I-P*Machine washer, power washManual, Ultrasonic, Soak, C-I-P*Manual, Ultrasonic, Soak, C-I-P*

Mild alkaline

Low-foam alkaline

Mild acid

Enzyme



1 W.A. Jenkins and K R Osborn, Packaging Drugs and Pharmaceuticals, Technomic PublishingCo, Lancaster PA, 1993, p 28.


reversed to be below the pH at the pKa and the isoelectric point ofthe surface being cleaned in order to achieve a positive-positiverepulsion, or at least a neutral residue and a positive-character sur-face without attraction.

TABLE 2 OPTIMIZING THERMODYNAMIC CLEANING CONDITIONS FOR SURFACE/RESIDUE ELECTROSTATIC REPULSION

Acidic residues pH > pKa and isoelectric point of surface

Akaline or basic residues pH < pKa and isoelectric point of surface

For any cleaning, however, it is important to also consider thecorrosive effect of pH on the surface being cleaned. Typically, it isdesirable to choose a cleaner with a pH that will not etch or cor-rode the surface—for stainless steel, within the limits of passiva-tion, and for glass, within the limits of etching. (It is important tonote that the addition of corrosion inhibitors can also extend theacceptable pH range.)

Clean-in-place (CIP) Cleaning—As pharmaceutical processesgo from R&D to pilot scale to manufacturing, the cleaning tech-niques and equipment can change to fit the needs of the scale ofmanufacturing. A bench scale system can often be adequatelycleaned by manual and soak cleaning procedures. As systemsbecome larger it can be worthwhile to install clean-in-place (CIP)systems. Parts of the following discussion on CIP cleaning is para-phrased from the website operated by Dale Seiberling—the selfproclaimed CIP Evangelist (www.seiberling4cip.com).

CIP cleaning can be accomplished by the action of a cleaningsolutions with spray or recirculation under pressure of the initialflush, wash, and rinse solutions by controlling time, temperatureand cleaner concentration.

• Piping Systems can be effectively cleaned via recirculationof flush, wash, and rinse solutions at flow rates which willproduce a velocity of 5 feet per second or more in the largestdiameter piping in the CIP circuit.

• Mixers, tanks and blenders can be effectively cleaned bydistributing flush, wash and rinse solutions on the upperssurfaces at pumping rates equivalent to 2.0-2.5 Gpm per footof circumference for vertical vessels, or at 0.2-0.3 Gpm persquare foot of internal surface for horizontal and rectangulartanks.

• Glass—has an isoelectric point of 2.5 associated with theSiO2.

Raising the cleaner solution pH (past the isoelectric point),causes the surface takes on a more negatively charged charac-ter. If the residue to be remove also has a negative charge atthat pH, then the negative surface will repel the negativelycharged residue.

In addition to material surfaces, many residues can alsoundergo a change in electrical charge due to a simple changein their pH. For most acids, the pKa indicates the pH at whichthe hydronium ions and conjugate base are present in equalconcentrations. Moving higher in pH shifts the equilibriumtoward the right, thereby increasing the concentration of thenegative conjugate base. Thus, when cleaning acids it is desir-able to use a cleaning solution with a pH above the isoelectricpoint and the pKa of the acid. This results in an increase inthe concentration of the negative conjugate base, with a pHabove the isoelectric point of the surface where the surfacewill take on a repelling negative character.

TABLE 1 RELATIONSHIP OF pKA, CONJUGATE BASE AND HYDRONIUM ION CONCENTRATION

HA + H2O ➔ H3O+ + A-

[HA] = acid concentration H2O = water H3O+] = hydronium [A-] = conjugate base concentration concentration

pKa = –log [H3O+ ][A-]/[HA]

For example, with stearic acid (C17H35COOH), the conjugatebase is the negatively charged stearate ion (C17H35COO-). The pKais about 5. This means that at a pH of 5 and above, we begin todrive the reaction toward the right, thereby converting stearic acidto negatively charged stearate ion.

If the stearate ion is a residue on steel and the pH is as high as8.5 and above, then not only do we have negatively chargedstearate ions due to being above the pH of 5, but also steel surfacesthat are negative in character by virtue of their being at a pH abovethe isoelectric point. The steel and the stearate ions repel eachother, facilitating cleaning.

As in table 2, for basic residues, these condition would be


ance. The overall scope of the design criteria is to follow FDA’srationale that cleaning equipment should “prevent contamina-tion or adulteration of drug products.”

Structural Flexibility—The design of the GMP washerhas evolved over the past 10 years from a modified laboratorywasher manufactured in a common production line, to a spe-cific product division within the most up to date manufactur-ers. Complete separation of tooling and superior welder quali-fications are requirements for this range of products as qualitycontrol and documentation of the entire construction processis closely recorded and provided as a deliverable in the finaldocuments. The washer/dryer must be able to perform a multi-use task while taking into consideration effective utility andfloor plan consumption. Effective use of the chassis mustallow for service and technician access as well.

For the outer shell of the washer, materials of constructionshould be 316L so as to allow for integration into the cleansuite arena and be able to withstand the cleaning chemicalsused in this arena. Service panels should be able to bedesigned to allow for access to the critical componentsthrough mechanical chases or locations that the design of thefacility allows. Many times, the washer must adapt to the par-ticular features of the room that requires the positioning ofthe internal components to be accessed by the facilities or vali-dation teams during and after the installation and calibrationprocess. Temperature and monitoring instrumentation shouldbe able to be removed from their ports via tri-clamped connec-tion and have enough coil length to be able to be placed on ametrology cart outside of the structure of the washer. This willallow for easy calibration and verification during validation.

Freestanding or recessed models must be available to givethe facility the product flow characteristics required for theirprocess.

Chamber Flexibility—for faster cycle times, effective useof the chamber will allow for a minimization of cycles and ahigher throughput of the washer/dryer during the productionday.

Chamber design should allow for minimal water retention.Chamber corners should carry a minimum of 1” radius and allsurfaces should be sloped to the drain. Internal structures of

• Integrated CIP Design may be applied to combine the clean-ing of vessels and piping in one pass in which flush, washand rinse solutions to the sprays, and providing for solutionreturn to the CIP system. This concept can accomplish CIP atthe minimal capital cost and is highly effective in reducingthe post CIP recontamination that often follows conventionalcleaning of lines and vessels in separate circuits.

A CIP monitoring and control system can be installed to ensurethat the CIP system works reliably, rendering the process vesselsand piping molecularly spotless after every product run—or alarmloudly if it fails. The CIP monitoring and control system can docu-ment the system’s operation and history, and archive this informa-tion for regulatory compliance. One way to set up a monitoringsystem is to first circulate and flush water through the CIP systemwith the control system monitoring the valves and pressure toassure and record proper operation; proceed to the wash cycle,possibly using conductivity control to measure and record properaddition of cleaner solution; flush out the cleaner solutions andproceed to neutralization and rinsing steps. Final rinses can be cir-culated to equilibration for rinse water sampling if desired.

GMP Washing Machines—Equipment that is disassem-bled for cleaning, manufacturing tools, and bench scale pro-duction equipment that can be loaded into racks can often bebest cleaned in a washer that can do validated cleaning.

GMP Washer/dryer design—within the pharmaceuticalindustry there has been, and continues to be, a struggle for aclear definition of mechanical washer/dryer to properlyaddress the requirements of GMP applications. Within theGMP regs there exists several specifications (Part 133.4, 1963,and part 211.67, 1978) that attempt to bring some clarity tothe design concept. Unfortunately, these regulations leavemany areas open for interpretation with respect to specificconstruction criteria for a GMP Washer. With no clear defini-tion, many variations of “lab style” washers have been adaptedfor this arena with their limitations not evident until long afterthe purchase and installation.

There are inherent design criteria required for washer/dry-ers that will clean parts, glassware, plasticware and toolingused in pharmaceutical production adhering to GMP compli-


ulate migration into or out of the chamber. The door inthe down position provides an effective loading table forthe operators to easily access three sides of the rack toplace components to be cleaned. Heavy parts can beplaced on the door without having to reach into thechamber of the washer. Teflon wheels on the racks canprovide for a smooth transition into the chamber.

Component Selection—Internal components must becompliant to GMP requirements. Sanitary diaphragm valvesshould be available for all areas that come into contact withprocess fluid. Plumbing should utilize orbital welds whereverpossible and be finished to a minimum of 25 Ra. Dead legsshould be kept to a minimum of 6 pipe diameters. 316L stain-less steel should be the material of choice for all metallicareas. Cold rolled steel, copper, and other forms of stainless(except 304L for the frame) should be avoided at all times.

Special attention should be placed with the chemical deliv-ery system. This has been an overlooked area of GMP washerdesign due to the difficulty and expense of providing for aneffective solution. Delivery systems must allow for the additionof precise amounts of additives (caustic detergents and acidbased products) and must withstand to the harsh nature of theingredients that is being delivered. Many times, a commerciallaundry chemical system is used only to be the source of fail-ure months after qualification, resulting in costly down timeof the production facility.

Drying systems should provide complete coverage to allaspects of the load. Additionally, the washer itself should bedried entirely and prepared for the next validated cycle. Non-shedding materials should be used throughout the drying cir-cuit. High temperature rated HEPA filters should be the finalpoint for the air entering the basin or accessories so as to pro-vide for a clean, particulate free drying process. DOP challengeports should be provided so that the integrity of the HEPA’scan be challenged on a regular interval. Separate circuits forthe basin and the hydraulic circuit (including the internalparts for the loading accessories) will provide for the fastestand most effective cycles. This design is inherently moreexpensive but can be justified quickly.

the chamber should feature rounded edges with no threads orentrapment areas. 316L stainless steel finished to a uniform 25Ra should be a baseline for these washers.

Care should be taken with respect to the mating of theinventory systems to the hydraulic circuit. There should be nomechanical attachment required for the accessory racks.Spray headers should be positioned at the top and the bottomof the basin to aid in the cleaning of the parts positioned Inkeeping with design criteria of utility savings and GMP con-struction, the chamber volume should be sized to match theload configuration required for a specific facility.

Care should also be taken to match the items to be cleanedso that an effective load and unload pattern can be establishedthat minimizes operator errors. Multiple level loading configu-rations will allow for maximum utilization of the chamber vol-ume while minimizing the consumption of WFI.

Effective use of Teflon and stainless will allow racks andbaskets to mate to the chamber of the washer. (Threaded con-nections are to be avoided as they are entrapment areas forwater and particulate that could lead to cross contaminationof the products being cleaned.)

Since loads for GMP cleaning can range from glass to plas-tic to stainless parts, the design of a loading surface shouldallow for the weight associated with these components. Twotypes of doors are typically available for this application:

• Vertical doors—These allow for easy access to the itemsto be cleaned but make it difficult to provide for a seal tothe chamber and require the use of loading trolleys, thusadding to the number of accessories in the clean suite.Vertical doors typically have a window built in that hasbecome popular with lab-style washers but have no func-tionality in GMP. (Internal lights required for their useneed gaskets that have maintenance issues and the doorsare prone to leakage and service maintenance that maynot be possible during a production run. )

• Horizontal drop-down doors—These provide for aneffective loading table that also serve as an effective con-tainment structure for the chamber. Gaskets can bematched to GMP requirements that will allow for com-plete sealing of the chamber thus allowing for no partic-


glassware or parts for the lab or research function. Additionalchallenges such as materials of construction, soiling of activepharmaceuticals, load configurations, and regulatory con-straints add to the difficulty of this operation. However, whenproperly managed, this task can be easily transitioned andimplemented. A typical procedure for the understanding andevaluation of a wash protocol would include the following:

A. A clear understanding of the items to be cleaned. Thisdefinition is paramount to the success of a validatedsystem in that the operator must load and unload inspecific steps so as to maintain the validation of thecycle. Ergonomics of the load and rack must beaddressed at this point so as to make the additionaldesign and steelwork feasible.

B. An understanding of the soiling that will be on the partsto be cleaned. Any active pharmaceuticals must beaddressed and evaluated as to their abilities to becleaned within the limits of time/temperature/chemi-cal/agitation.

C. Load patterns must then be addressed. In many applica-tions specific components must be kept together duringthe cleaning phase so as to maintain their validated sta-tus in the scope of the process. This challenge requiresthat the design function of the inventory systems for theGMP washer have a full understanding of the materialsthat will be cleaned as well as their dimensional aspects.Parts can then be arranged on a CAD drawing to illus-trate the functionality of the rack and determine if thereare going to be any load/unload problems to overcome.It is this point that a clear definition of the cleaningcycle parameters can begin to come into focus.

D. Programming aspects of the PLC or microprocessor canthen take into account the requirements of the washerto perform the task to clean the items in the chamber.System monitoring and data transfer to other monitor-ing locations will occur at this point and will play a partin the design.

With these considerations, it is possible to successfully usea GMP washer to clean pharmaceutical equipment.

Inventory Systems—As important as the construction ofthe chamber, chassis, and internal components are to the over-all performance of the washer, the inventory is often the mostoverlooked aspect part of the project. Most often, manufactur-ers are criticized for the mating of the inventory system to thechamber and to the parts to be cleaned. This aspect of the pro-ject involves a complete inventory of the components to becleaned, their dimensional information, weight and specificcleaning requirements. Once this information is assembled theparts need to be grouped together in the loads that arerequired by the facility to be cleaned and an idea can then beformulated as to the chamber volume required to complete thetask. Ergonomics should be reviewed so as to not overload theoperator and to maximize the parts/run in order to minimizethe utility consumption of the facility.

Documentation Requirements—The final part of thepackage for a GMP washer is the associated documentationthat will give the validation teams the information whereby acomplete qualification of all aspects of the system can beimplemented.

The documentation package should contain (as a mini-mum) the following components:

• User’s manual

• Maintenance manual

• Instrument list

• Electrical diagram

• Piping and instrumentation diagram

• Spare parts list

• Exploded view

• Welding report and welder certificate

• Source codes are provided in the form of a written copy,a floppy disc, and a spare E-prom

• Passivation report

• As built drawings

• IQ/OQ documentation

Cleaning of components utilized in a GMP environmentpresents obstacles that are not found in generic washing of


processes—or small particulates that are present in the rela-tively clean manufacturing environment—requires selectingextremely free-rinsing detergents suitable for immersioncleaning.

For parenteral medical devices designed to be implantedinside the body, a key consideration is that there be no endo-toxins or pyrogens present on the surface. Endotoxins or pyro-gens are fever-causing cell debris or cell-waste products widelypresent in the environment. Cleaning these pyrogens or endo-toxins requires the use of a high-emulsifying cleaner combinedwith heat, followed by rinsing with pyrogen-free or endotoxin-free water. This type of water is often called water for injection(WFI). WFI is very high purity water derived from high-puritywater filtration systems.

LABORATORY CLEANINGDespite the increasing use of disposable plastics in the laboratory,reusable glass labware is still widely employed. This is due to envi-ronmental concerns (recycling issues and disposal problems asso-ciated with plastics), and because the vast majority of proceduresrequire glass. In addition, there are instruments and equipment,which for scientific or economic reasons, must be reused.

The principal concern for any scientist or technician workingwith laboratory glassware, instruments, and equipment is that theybe free of interfering residues. These often unseen residues cancause invalid analytical results. For example, they can erroneouslyaccelerate or decelerate rate dependent experiments by causinglocalized high concentrations of reactants inside micelles. They caninhibit culture growth, cross-contaminate batches, and cause non-reproducible results.

To solve these problems, equipment must be cleaned thorough-ly and any interfering residues removed. This requires that anappropriate laboratory detergent be selected and an effective clean-ing method used (Table 6C).

BIOTECHNOLOGYWhen biotechnology goes into production for biopharmaceuti-cals and gene-therapy products, the cleaning requirements canbe very similar to pharmaceutical needs. The residues thatneed to be cleaned are often complex mixtures resulting fromfermentation and cell culture. The cleaners used must notleave interfering residues that inhibit culture growth or unac-ceptable levels of batch-to-batch contamination. As in pharma-ceutical process equipment cleaning, disposable single useitems may be used for piping, seals, and filters. When pharma-ceuticals are manufactured, even at R&D pilot scale for trials,GMP procedures must be followed. The GMP washersdescribed in the preceding section are often used for biophar-maceutical cleaning. See chapter 8 on cleaning validation andChapter 7 on standard operating procedures, particularly theexample given on cleaning fermentation equipment.

MEDICAL DEVICE MANUFACTURINGThe cleaning done during medical device manufacturing isperformed in preparation for sterilizing and sterile packagingof medical devices. When selecting a detergent, careful consid-eration must be given to the materials from which thesedevices are composed. Usually medical devices are made offairly robust materials that can withstand corrosive blood andbody fluids. In some instances, one portion of the device isintended to come into contact with skin, blood, or body fluids.Other parts of the device are exterior to the human body andmay be made of less sturdy plastics or aluminum. If these lesssturdy materials are present, a milder detergent should beselected.

Medical devices are usually assembled under fairly cleanconditions. As a result, a light-duty cleaner is usually selectedto remove light quantities and types of soils.

Good medical device design entails creating devices thatdo not have small crevices, cracks, and difficult-to-clean orreach places. Often, medical devices are manufactured inmodest quantities, lending themselves to batch-cleaning oper-ations. Ultrasonic cleaning is a common cleaning method inmedical device manufacturing. This, coupled with the fact thatcleaning operations typically remove only light oils from


3. Ultrasonic cleaning is used for larger numbers and repeti-tive batches of labware cleaning. To clean in an ultrasonictank, a solution is made up in a separate container, the ultra-sonic tank filled, and the machine run for several minutes todegas the solution and allow the heater to reach the correcttemperature. Small articles should be placed in racks or bas-kets; irregularly shaped articles aligned so that the long axisfaces the ultrasonic transducer (usually the bottom); and thema-chine should run 2–10 minutes until parts are clean. Athorough rinse follows.

4. Automatic syphon washing is an effective way to cleanreusable pipets. The pipets should be placed completely cov-ered in a detergent soak solution as soon as is practical afteruse. This prevents soils from drying onto the pipes. Whenready to clean, the pipets are placed in a holder; an efferves-cent tablet cleaner is dropped into the washer; the pipets areplaced in a holder over the tablet; and the cold or warmwater is turned on at a rate that will fill the washer to coverall of the pipets and allow them to drain thoroughly. Thismay take as long as an hour. For analytical use, a final rinsein deionized or distilled water may be required.

5. Machine washing is used in laboratories for cleaninglarge quantities of reusable labware. The machine’s direc-tions should be consulted for details on its proper use. Ingeneral, the labware is loaded on racks with open ends fac-ing the spray nozzles. Narrownecked flasks should be placedin the center of the racks, preferably on specially designedspindles with spray nozzles directed into the necks.Handling of the labware in the racks should be kept to aminimum. Small articles should be grouped in baskets toprevent dislodging by spray. Only low-foaming detergentsdesigned for these machines should be used. Typically, 10mL of detergent per liter of hot, wash-cycle water (approxi-mately 60˚C) is used.

6. Rinsing is an often overlooked and very important part oflaboratory cleaning. A thorough running water rinse thatcontacts all surfaces of an article for at least ten seconds persurface may be required. Filling and emptying small vesselswith rinse water at least three times is a good rinse proce-dure. For machine cleaning, there should be at least three

TABLE 6C DETERGENT SELECTION GUIDE FOR LABORATORY CLEANING

The following are common laboratory-cleaning procedures,along with guidelines for eliminating interfering residues.

1. Soaking is used to clean small items and the insides oflarger vessels. It should be used as a pretreatment to preventsoils from drying onto labware. A soak tank should be keptat the laboratory bench for immersing used labware untilsuch time that it can be washed. Soaking is also effective toclean or pretreat very difficult, dried-on residues. To cleanby soaking, a detergent recommended for soaking should beused, and a detergent soak solution made up according tothe directions. The article should be completely submergedto prevent any deposits or etching at the air/solution inter-face. Soils should be soaked until they are removed; thismay take several hours. Some soils may require additionalagitation or wiping in order to remove them. A thoroughrinse follows.

2. Manual cleaning is used to clean small batches of labwareequipment and benches. It is the most commonly used labo-ratory cleaning method. To clean manually, the article to becleaned should be wet either by immersing it in the deter-gent solution, or by using a soaked cloth or sponge. Fornonabrasive scouring, un-diluted detergent should bepoured onto a wet cloth or sponge for scrubbing. A cloth,sponge, brush, or pad can be used for cleaning. A thoroughrinse follows. Protective gloves and eye protection should beworn if recommended or required.

LaboratoryReproducibleresults, no interfer-ing residues,extending equip-ment life. Keep lab-oratory accredita-tion. Laboratorysafety.

Glass, metal, plastic labware, ceramics, tis-sue culture, porcelain, clean rooms, animalcages, bioreactors, tubing, benches, safetyequipment.

Tubes, reusable pipets.Water and environmental sampling.Phosphate-sensitive labware. EPA procedures.

Radioactive equipment/contaminants.Stopcock grease.

Trace metals, metal oxides, scale.Proteinaceous soils, bio-wastes, tissue, bloodand other body fluids, fermentation residues

Manual, Ultrasonic, Soak, C-I-P*Machine, powerspray, labwarewasher, washer-sterilizer, cage-washersSiphon-type washer-rinsersManual, Ultrasonic, Soak, C-I-P*Machine washer, labware washerManual, Ultrasonic, Soak, C-I-P*Machine washer, warewasher

Manual, Ultrasonic, Soak, C-I-P*Manual, Ultrasonic, Soak, C-I-P*Glassware washer

Mild alkalineLow-foaming alkaline

TabletMild alkalinePhosphate-free, low foamHigh emulsifying, mild alkalineLow-foaming alkaline, high emulsifying, alkalineMild acidEnzyme CleanerLow-foaming alkaline




should follow to assure that there is no such cross-contamination:

1. Use a laboratory-grade cleaner that does not contain any of thetypes of ingredients that can be analyzed to eliminate the pos-sibility of any detergent residue that can cause cross-contami-nation.

2. Perform equipment “blanks” by cleaning glassware or handlingand sampling equipment and then performing an analysis onthe glassware or equipment to determine whether it has anycontaminants. For example, a U.S. Environmental ProtectionAgency protocol calls for the use of phosphate-free laboratorygrade detergents such as Alconox or Liqui-Nox. Phosphate-freecleaners are specified because in water analysis, where one isoften testing for the presence of phosphates, this procedureeliminates the potential risk of cross-contamination from phos-phates. (Note: Alconox is a phosphate-containing detergent. Ithas been used for cleaning phosphate analysis labware formany years. When rinsed thoroughly, it will not leave phos-phate residues.)

FOOD AND BEVERAGE PROCESSINGIn food and beverage processing one is faced with hard surfaces thatare fairly robust and can stand up to the corrosive environments typi-cal of this industry. Even meat that contains blood can be fairly cor-rosive, orange juice is fairly acidic, while other foods have their owntendencies to attack hard surfaces.

TABLE 6E DETERGENT SELECTION GUIDE FOR FOOD AND BEVERAGE CLEANING

Good process design should eliminate the cracks andcrevices and difficult-to-clean places in a properly designedfood or beverage processing plant. In food-and-beverage pro-cessing, manual cleaning is often employed for benches, coun-

rinse cycles after cleaning. Final or all rinses in water ofsuitable purity should be used for analytical labware toremove any tap water residues. For tissue culture and gener-al analytical ware, a deionized or distilled water final rinseshould be used. Trace organic analytical ware should berinsed in distilled or organic-free water. Trace inorganic ana-lytical ware should be rinsed in deionized water.Pharmaceutical and clinical research labware may requiresterile, pyrogen-free, or injectable water rinsing, dependingon the work being done.

Following these procedures diligently may help to ensure thatone’s research is not fraught with the problems associated with inter-fering residues on the surfaces of reusable labware, instruments, orequipment.

ENVIRONMENTAL AND WATER TESTINGTypically trace analyses—usually for trace organics—are conductedfor pesticides, known carcinogens, and known toxic organic com-pounds. (The EPA can provide a list of types of organic compoundswhich might reasonably be testing for.) Other trace analyses focus oninorganic compounds—typically trace metals due to their toxicityincluding metals such as mercury, cadmium, and zinc.

TABLE 6D DETERGENT SELECTION GUIDE FOR ENVIRONMENTAL CLEANING

In some instances, such as with soil or water testing the purposeof the test is to determine general water quality. In such cases,trace analysis is often performed for toxins. Quantitativeanalysis is used for drinking water as well as in determiningsoil quality for farming or gardening.

The key consideration for cleaning is to make sure all samplingand handling equipment as well as glassware that comes into contactwith the soil or water does not have any cross-contamination fromthe any previous soil or water tests. There are two procedures one

EnvironmentalNo interferingresidues.Phosphate free.

Bailers, samplers, augers, containers, tubing, teflon, glass,rubber, stainless steel.

Manual, Ultrasonic, Soak, C-I-P*Machine wash, pressure spray

Phosphate free, mildalkalineLow-foam, phos-phate free, alkaline


*Clean-in-Place by circulating, for spray clean-in-place see machine washer detergents.Food & BeverageAvoid interferingresidues on food-contact equipment.

Stainless steel, food-contact equipment.

Oxides, scale, trace metals, salts,milkstone.Filter membranes. Proteinaceoussoils.

Manual, Ultrasonic, Soak, C-I-P*Machine wash, pressurewashersManual, Ultrasonic, Soak, C-I-P*Manual, Ultrasonic, Soak, C-I-P*

Mild alkaline

Low-foam alkaline

Mild acid

Enzyme




degrading it and the performance of the vacuum part. This type ofcleaning requires a thorough understanding of the soils present onthe part in order to choose a detergent that will be effective.

TABLE 6F DETERGENT SELECTION GUIDE FOR ELECTRONICS CLEANING

Additional types of soils encountered in electronics cleaning aresolder flux residues, mold release agents, as well as metal oxidesformed on vacuum components. For example, metal oxides may befound on frame holders.

While organic residues usually require some type of emulsifierfor their removal, metal oxides are frequently better removed by anacid cleaner with high chelating or sequestering capacities.

PC BOARDSA wide variety of contaminants can remain on the completed assem-bly surface if they are not properly cleaned. These contaminants canbe:

• Ionic—those with an ionic charge, typically salts such as sodi-um, potassium, and chlorides. These are of particular concernbecause they are potentially conductive, mobile residues.

• Polar—having a dipole moment (a molecule with partiallycharged, positive or negative ends or poles), in the sense that“like dissolves like,” which tend to solvate ionic residues lead-ing to the concerns previously discussed.

• Nonpolar—having no dipole moment, typically an organicfilm with insulating and adhesion interfering properties forbonding or marking.

• Nonionic—organic compounds that have no ionic charge andare not salts. They may be either polar or nonpolar (as dis-cussed previously).

Salts such as plating salts, etching salts, and activators are typi-

ters, mixers, extruders, and processing equipment. This callsfor cleaners that are effective in immersion cleaning. To cleanthese, you need high-emulsifying cleaners where there is a signifi-cant amount of organic food residue.

In meat or poultry processing plants where proteins are present itis advisable to use an enzyme cleaner. The types of hard surfacesfound in these environments are typically stainless steel or robustplastics such as high density polyethylene, or even ceramic surfaces.

One of the unique surfaces found in food or beverage processingplants are filtration membranes used to filter various process streamsof food or beverage products. Examples include juice and decaffeinat-ed coffee processing as well as cheese manufacturing. Such processesoften result in highly fouled, difficult-to-clean filter membraneswhich are often very expensive filters with high value. Effective clean-ing maximizes their useful life and returns their performance to highrates of throughput.

Since the foods being filtered are by definition foods or nutrients,these membranes are also frequently fouled by biocontamination thatgrows on the nutrient value of the food, causing a condition knownas bio-fouling or bio-film. This type of fouling is often effectivelyremoved by an enzyme-based cleaner. Enzyme-based cleaners arealso desirable because they often can be made with a neutral or near-neutral pH that won’t damage the membranes.

It is important to note that since some membranes are delicateand cannot face harsh alkaline or acid cleaners, it is crucial to selecta detergent which will not cause membrane damage.

GENERAL ELECTRONICS CLEANINGElectronic components are usually made of metal due to their con-ductive nature and their ability to be bonded by soldering. Solderinginvolves the use of flux, an undesirable contaminant since it is notonly unsightly but acidic, thus causing corrosion of electronic com-ponents.

Other types of electronic components are glass or ceramic insula-tors. It is important to clean the surface completely in order to pre-serve their insulating properties. Oils or other conductive residues orparticulates must often be removed.

A special consideration in electronics cleaning involves compo-nents that rely on a vacuum to create an insulator. These include lightbulbs and vacuum tubes where residue can “outgas” into the vacuum,

ElectronicsAvoid conductiveresidues, avoidCFCs, pass cleaningcriteria.

Circuit boards, assemblies,screens, parts, conductiveresidues, resins, rosins, fluxes,particulates, salts.


Manual, Ultrasonic, Soak, Machine wash, power spray,board and screen washers

Manual, Ultrasonic, SoakParts washers

Ion-freeIon-free, Low-foam

Mild alkalineLow-foam alkaline



residue is not always white. It can be gray, tan, beige, or amber incolor. There are several possible causes. In some instances the assem-bly butter coat is removed, thus revealing the glass weave intersec-tions. This is known as measling. This can result if too harsh a sol-vent is used for cleaning. Another instance of white residue is whenactivator materials are left behind on the assembly surface. This cancome about if the solvent used for defluxing has become depleted ofalcohol (this is especially true of solvents based on trichlorotribluo-roethane or CFC-113).

Another cause of white residue is solder paste. Solder paste con-tains materials known as thickening agents (thixotropic agents orrheological modifiers). These materials are difficult to remove duringthe defluxing operation, especially without the expenditure ofmechanical energy, e.g., sprays. These thickening agent residues areprone to form a white residue, especially if exposed to alcohol.Exposure to alcohol can come about either from alcohol in thedefluxing solvent or alcohol in an ionic contamination tester.

However, the principal cause of white residue is due to thermaldegradation of rosin. Rosin readily undergoes degradation and poly-merization (the molecules bond together to form a much larger mole-cule). This is especially true when it is heated around 260˚C (500° F)or higher. The rosin also interacts with tin and lead salts formed dur-ing the fluxing operation by the activator action on the solder oxides.The rosin interaction products are termed tin and lead abietates. Thepolymerized rosin and/or tin and lead abietates are much more diffi-cult to remove by a defluxing solvent because of their more insolublenature. Typically, the white residue appears after the defluxing opera-tion after the defluxing solvent has flashed off. Both rosin fluxes androsin pastes are prone to form this type of white residue.

If this type of white residue appears, what can be done? First, itis necessary to ascertain that the flux (or paste) is truly the source ofthe white residue and to verify that the white residue does not haveanother cause.

PRECISION ELECTRONICSAqueous cleaning technology is used to meet the high level cleaningrequirements in precision electronics manufacturing of disk drives,semiconductors, and electrooptics. These industries use high purityaqueous cleaners in controlled environment manufacturing settings.These cleaners are made from high purity ingredients with filtration

cally ionic. Many of the organic species are nonionic. However,organic acids such as the rosin acids and organic acids used as acti-vators are ionic. An organic molecule by definition is one based onthe element carbon.

The most detrimental type of contaminant is the ionic type. If notcleaned away, ionic species of contaminants can cause serious prob-lems including leakage currents between traces on a board as well assevere corrosion. The presence of moisture greatly accelerates theactivity of ionic species since water solvates the ions and enablesthem to become mobile. In the presence of an applied voltage acrosscircuit traces and moisture, dendritic growth can occur. This occurswhen atoms of the circuit trace migrate outward across the bare lam-inate until they bridge the circuit width, causing an electrical short.

Mobile ionic species speed up this form of growth. Mobile ionicspecies are also responsible for corrosion products being formed onthe assembly surface. Military contractors are required to apply aconformal coating to protect the assembly surface from moisture. Aconformal coating is, of course, a polymeric material such as anepoxy, polyurethane, or acrylic designed to protect the assembly sur-face from moisture. In addition, conformal coatings also isolate cont-aminants and prevent them from migrating or being dislodged duringtemperature-moisture cycling, high vibration, shock environments,etc.

Nonionic contaminants remaining on the assembly surface canalso lead to performance problems. These contaminants can interferewith electrical bed-of-nails testing by creating electrical “opens.” Theycan also lead to adhesion problems if a conformal coating is beingapplied.

Ionic materials and some hygroscopic nonionic materials underconformal coatings can also lead to blistering duringtemperature/humidity cycling. This phenomenon is also called meal-ing or vesication, and it takes place because no conformal coating is100% effective against moisture penetration. In fact, the presence ofionic material or hygroscopic material on the surface under the con-formal coating actually acts to promote water penetration since suchcontamination attracts water. Once the contaminant becomes hydrat-ed, it builds up osmotic pressure which causes a lifting of the confor-mal coating thus leading to the blister or vesicle. This type of phe-nomenon must be considered detrimental to the finished assembly.

Finally, there is the phenomenon of white residue (WR). White


short contact times, rapid rinsing, and rapid drying to minimize thechance for corrosion to occur. It is also critical to be careful usingextremely high purity deionized rinse water that can be so “ion hun-gry” that it is corrosive to the metal substrate being rinsed.

PLASTICSPlastics cleaning involves the selection of a mild nondamaging clean-er that is strong enough to remove the soils you are cleaning. Asyou can see in the table below, many plastics are resistant toattack by typical mild alkaline aqueous cleaners. For delicateplastics consult the plastic manufacturer regarding their rec-ommendations for cleaner compatibility or use one of the spe-cially formulated plastic cleaners.

PLASTICS COMPATIBILITY WITH CLEANERSGenerally acceptable with mild aqueous cleaners

Polyethylene (LLDPE, LDPE, PE)Polypropylene (PP)Polyallomer (PA)Polymethylpentene (PMP, TPX)Fluoroethylenes (FEP, TFE, PFA, ECTFA, ETFE, TEFLON®)Polysulfones (PSF)Polyvinylchloride (PVC)Polystyrene (PS)Polyvinyl fluorides (PVDF)Polyeurethane Ethylene Propylene (EPM)Buna N rubberNordel®

Viton®

Noryl®

Ryton®

EpoxyClean with caution even with mild aqueous cleaners

Polycarbonates (PC)Acetal polyoxymethylene (ACL)Nylon®

Polymethylmethacrylate (PMC)

and purification steps in their manufacture. The end-user manufac-turers may further filter the cleaners at the point of use. It is notunusual for a high-purity cleaner to be made in a clean environmentwhere it is filtered to 5 microns and then have further filtration tolevels such as 0.2 microns at the point of use. Delivery of finishedcleaner that is filtered to 0.2 microns or better requires manufactur-ing, filtering and packaging in a cleanroom environment.

PRECISION MANUFACTURINGIn many of today’s high-tech metalworking applications, surfacesmust be prepared by the removal of debris, oxides, scale, and salts toachieve extraordinary levels of cleanliness. Cosmetic factors can alsoenhance buyer perceptions—with a bright, oxide-free finish servingas visual indicator of product quality.

Numerous metalworking and metal finishing businesses are find-ing that aqueous detergents perform as well as or better than solventcleaners in removing residues but without their harmful environmen-tal side effects.

Among new, high-tech applications for aqueous cleaners are:

• Anodized parts—An anodizing shop which produces anodiccoatings on aluminum substrate caps for mounting personalcomputer IC chips with no conductive tail-end residues and nointroduction of toxicity or flammability.

• Computer parts—A major manufacturer of thermocouplesand wafers used in computers and medical devices must cleanceramics and copper paste in heated (150˚F) ultrasonic bathsprior to nickel plating.

• Aluminum—A manufacturer of heat sinks for cooling com-puter chips in NASA space shuttles uses aqueous detergents toremove oil and organic debris to eliminate any chance of non-condensable gas formation.

In general, precision manufacturing with metals involves prepar-ing the surface for bonding, coating, or exposure to an environmentsuch as a vacuum or a semiconductor that cannot tolerate interfer-ence from residues. Thus it is important to make sure that the metalwill not be attacked by the cleaning, rinsing, or drying process.Unfortunately, corrosion inhibitors that leave deposits often cannotbe used for precision cleaning, so it is important to use mild cleaners,


TABLE 6G DETERGENT SELECTION GUIDE FOR PRECISION MANUFACTURING

OPTICS Aqueous detergents have also found application in the manu-facturing of scientific as well as consumer optics such as con-tact lenses. For example, one manufacturer uses machiningoils and heavy waxes to grind and polish its scientific optics toexacting tolerances. These must be removed from the surfaceof the finished product. The company’s technicians have foundthat an alkaline detergent—normally used in lab washers andultrasonic cleaning systems—was ideal for removing suchwax. (They use a separate, pH-neutral cleaner to brighten thecopper and copper alloys that surround these optics.)

On the consumer-product side, contact lens manufacturingalso employs pH-neutral aqueous cleaners to remove the waxused to secure silicon/acrylic copolymer lenses to collets forCNC machine forming of the all-important base curve layerwhich ensure proper fit and wearer comfort. The detergenthas also found application in removing the compounds usedin grinding rigid gas permeable (RGP) contact lenses.

Aqueous cleaners have been widely adopted in solvent-reduction programs by metalworking and parts-washing oper-ations. Often, the level of cleanliness required is either forappearance only or for suitability for painting, bonding orcoating. It is critical to choose a detergent that is compatiblewith the type of parts washer being used.

For more delicate plastics, a mild alkaline cleaner canoften be used at modest temperatures, low concentration, andshort contact times. The most challenging plastic to cleanwithout damage is stressed polycarbonate which is prone tostress cracking on exposure to low surface tension solutionssuch as solvents and aqueous cleaners. Very dilute cleanersolutions may be needed to clean stressed polycarbonate.

Most plastics are organic in character which makes themattractive to organic film residues. A high emulsifying cleaneris often required to remove organic films from cleaners.

GLASS AND CERAMICSGlass and ceramic have excellent insulating, transparency, anddimensional characteristics that make them a desirable mater-ial for many high-tech manufacturing applications.

Since these are inorganic matrix materials, they oftenattract and hold inorganic soils such as salts and ions.Aqueous cleaners having good chelating properties or acidicpH are often effective at removing such inorganic soils.Examples of the use of aqueous cleaners in glass and ceramicprecision manufacturing include:

• Ceramic crucibles—used in semiconductor-grade labsand in manufacturing need to be cleaned of any mobileion residues prior to sales to semiconductor customers.Aggressive immersion cleaning using heated ultrasonicswith high wetting, high emulsifying cleaners has beensuccessful in providing suitable surfaces.

Metalworking and PrecisionManufacturingClean parts, avoidvolatile solvents,strong acids, andother hazardouschemicals.

Glass, ceramic, porcelain, stainlesssteel, plastic, rubber. Oils, chemicals, particulates.

Aluminum, brass, copper, andother soft metal parts. Oils, chemi-cals, particulates.

Inorganics, metallic complexes,trace metals and oxides, scale,salts, buffing compounds.

Silicone oils, mold-release agents,buffing compounds.

Metal oxides, scale, salts. Metalbrightening.

Manual, Ultrasonic, Soak, C-I-P*Machine washer, power washManual, Ultrasonic, Soak, C-I-P*Parts washer, power wash

Manual, Ultrasonic, Soak, C-I-P*Parts washer, power washManual, Ultrasonic, Soak, C-I-P*Parts washer, pressure sprayManual, Ultrasonic, Soak, C-I-P*

Mild alkaline

Low-foam alkalineMild alkaline

Inhibited low-foamalkaline or neutralMild acid

Low-foam alkalineHigh-emulsifying,mild alkalineLow-foam alkalineMild acid




NUCLEAR Few industries use more exotic alloys, nor have more stringentquality-control requirements in manufacturing, than precisionmanufacturing of nuclear equipment. Components such asguide tubes, end fittings, coil springs, grids, and fasteners usedin fuel assemblies for reactor cavities must be absolutely freeof oils or other contaminants.

One major manufacturer of nuclear fuel assemblies hasfound that large parts such as 12-foot guide tubes can be effec-tively cleaned through manual soaking in a 1:100 dilution of apH-neutral aqueous detergent and hot tapwater.

In reactor cavity cleaning, a specialty chelate-free aqueouscleaner brand has been successfully used during outage proce-dures at commercial nuclear-power plants and auxiliary build-ings for radiological decontamination of floors, walls, tools,personal safety equipment, and components made of metaland plastic—permitting release of cleaned items from con-trolled areas.

The key consideration with on-site cleaning is that thedetergent contain no chelating agents which can bond chemi-cally to radioisotopes, It should also contain no fluorides,chlorides, or sulfur ingredients which might cause surface cor-rosion or intergranular stress corrosion of stainless compo-nents.

TABLE 6J DETERGENT SELECTION GUIDE FOR NUCLEAR CLEANING

CHEMICAL AND OTHER FLUID PROCESSINGThe three main areas of concern in chemical and fluid pro-cessing cleaning are:

• Cleaning chemical process equipment—most notablywater or other high-purity chemical delivery systems

• Oxygen/gas delivery systems—where pipes and tanksneed to be kept extremely clean

For example, high-agitation cleaning solution machinessuch as bubble/air agitated immersion, spray wand, spraybooth, and conveyorized spray machines require the use oflow-foaming cleaners. Circulated, static, and ultrasonicimmersion cleaning can be accomplished with high emulsify-ing, high foaming cleaners. Less rigorous rinsing is oftenacceptable. Tap water may be a sufficient rinse and the tracesof water spots may be acceptable.

For appearance cleaning, however, a “no-rinse” processinvolving merely wiping the parts or air blowing them may bebetter when highly dilute cleaner solutions are employed.

TABLE 6H DETERGENT SELECTION GUIDE FOR OPTICS CLEANING

COSMETICSCosmetic manufacturing involves many oils, pigments, emol-lients, and “waterproof” ingredients. Some of the most diffi-cult to clean are titanium dioxide cremes and silicon oil emol-lients. Aqueous cleaning detergents are ideal cleaners for sili-con, titanium dioxide, and other hard-to-clean residues gener-ated in cosmetics processing. As with pharmaceutical process-ing, there can be absolutely no residues that could contami-nate products and cause eye or skin irritation problems.Silicon emollients can be removed using very high tempera-tures above 75˚C (170˚F) and double-strength solutions of ahigh emulsifying cleaner used in a total immersion cleaningsystem. Titanium dioxide cremes also often require very hightemperatures and a cleaner with good emulsifying and excel-lent dispersants.

TABLE 6I DETERGENT SELECTION GUIDE FOR COSMETICS CLEANING

OpticsAvoid optical interface

Lenses, substrates, mirrors, reflec-tors, fibers

Manual, Ultrasonic, Soak Parts washers, machinewashers

Mild alkalineLow-foam alkaline


CosmeticsAvoid cross-contamination

Product contact surfaces. Manual, Ultrasonic, Soak, C-I-P*Parts washers, power spray

Mild alkaline

Low-foam alkaline


NuclearNo isotopic exchange.Chelation interference.

Cavities, floors, tools. Manual, Soak

Spray machine

Chelate free, mildalkalineChelate free, low-foam alkaline


Industrial Cleaning Application 9594 The Aqueous Cleaning Handbook

REFERENCESAdams, D. G. and Agaarwal, D. (1990). “CIP System Design and

Installation,” Pharmaceutical Engineering, Vol. 10, No. 6, pp. 9-15. Alconox Inc. Guide to Critical Cleaning, Detergent Selection Guide, p. 12.Cleaning Printed Wiring Assemblies in Today’s Environment, edited by

Les Hymes, published by Van Nostrand Reinhold.Alconox Cleaning Solutions newsletter, Vol. 1, Number 1, “Drug compa-

nies find aqueous cleaners a sure cure for cross-contamination” andVol. 1, Number 2, “How Clean Is Clean?”

American Laboratory News edition, June 1992 article “Stopping residueinterference on labware and equipment.”

Grimes, T. L., Fonner, D. E., Griffin, J. C., Pauli, W. A. and Schadewald,F. H. (1977). “An Automated System for Cleaning Tanks and Partsused in the Processing of Pharmaceuticals,” Bulletin of the ParenteralDrug Association, 31, No. 4, pp. 179-186.

Mahmood, T and John Chu “Cleaning Solutions in the SemiconductorWafer Manufacturing Process” in Ch 5.4 Handbook for CriticalCleaning, Kanegsberg, B. Ed., CRC Press Publishers, Boca Raton,2001, 542-561

Weitzel, Steven “Strategies for Simplifying Cleaning Validation” referringDr. M. E. Labib, presented at Cleaning Validation and CleaningProcesses, Jan 14-15, Philadelphia, PA USA (2002)

RESOURCES www.alconox.comcleantechcentral.com www.metalfinising.comwww.seiberling4cip.com

• Waste treatment systems—particularly those involvingthe use of filter membranes

In piping systems, clean-in-place cleaning is usuallyemployed where a cleaning solution is circulated through thepipes and then rinsed thoroughly to the desired level of clean-liness with an appropriate rinsewater.

This is quite similar to the kinds of cleaning done withoxygen delivery piping systems. In an oxygen delivery pipingsystem it is crucial to have no residues that would be poten-tially oxidizable as this could cause a flammable or explosivecondition.

In waste-treatment filtration, one is often working withsmall to medium sized, in-plant systems where fats, oils,greases, or process oils from manufacturing processes need tobe separated from waste water in order to have an acceptableplant discharge. If this separation is done by a filtration sys-tem, the filter membranes need to be cleaned with a high-emulsifying and or high-dispersing cleaner to rejuvenate themembranes. Often a high-emulsifying cleaner is used first toremove the oils and greases, followed by the use of an acidcleaner to remove particulates such as organic soils and silt.

TABLE 6K DETERGENT SELECTION GUIDE FOR CHEMICAL AND FLUID PROCESSING

Chemical andFluid ProcessingNo interferingresidues.

Pipes, tanks.

Filters, membranes, proteins, bio-fouling.Filters, membranes, silicate.

Filters, membranes, grease, oil.

Manual, Soak, Spray, C-I-P*Circulate, Soak, C-I-P*

Circulate, Soak, C-I-P*

Circulate, Soak, C-I-P*

Mild alkalineLow-foam alkalineEnzyme cleaner

Mild acid

Mild alkaline



Standard Operating Procedures 97

CHAPTER SEVEN

Standard OperatingProceduresA large part of successful cleaning relies on having a sound,reproducible procedure. This, of course, aids in making it easi-er to train operators so that cleaning is consistent. The follow-ing are sample standard operating procedures for manualcleaning, ultrasonic cleaning, machine washer cleaning, andlarge-tank cleaning.

In some cases, these standard operating procedures werewritten for specific detergents and temperatures for specificsoils. As a result, they may need to be adapted to meet specificapplications. However, they provide examples of what shouldbe included in a standard operating procedure.

The following are lists of the items to consider, includingin different types of standard operating procedures (SOPs),that can be adapted to the needs of people writing cleaningprocedures.

In general a good SOP should present a list of materialsand people involved, the surface being cleaned should be iden-tified, and the eight key variables for cleaning effectivenessshould be defined:


1) precleaning handling2) cleaning chemistry/

concentration3) time4) temperature

5) type of agitation 6) rinsing conditions 7) drying conditions 8) postcleaning handling

Where cleaning solutions are re-used in baths or sumps,the control parameters and equipment used should be defined(such as conductivity or pH) the limits should be defined, the

Standard Operating Procedures 9998 The Aqueous Cleaning Handbook

c. Do not remove parts from shipping containers prior tobeing ready to clean them promptly—if you know thatunpacking the parts increases the risk of new contami-nants, or

d. Handle all parts with finger cots to avoid adding finger-prints to surfaces – if you do not want to add any newfingerprints to a surface where you are using a cleaningprocess that is only designed to remove particulates

e. Presoak the parts in a defined detergent solution at adefined temperature and time prior to cleaning – forexample presoak parts completely immersed in 1% Terg-a-zyme detergent (1.25 ounces Terg-a-zyme in 1 gallonof water) at 120 deg F for 20 minutes prior to cleaning—if you know your parts have dried on protein soils thatare difficult to clean without presoaking

4. Directions for making up the detergent solution: Makeup detergent solution diluted in water of suitable purityaccording to directions in a container of suitable size at agiven temperature.a. For example: Mix 1.25 ounces of Alconox powdered

detergent in 1 gallon of 120 deg F hot tap water in a 2.5gallon bucket. Use cleaning solution within 15 minutesbefore the temperature drops below 120 deg F.

5. Manual cleaning description:a. Wet part or surface with solution by

i. Dunking the part in the solution, orii. Wiping the part with a solution soaked brush,

absorbent cloth or spongeb. Clean by scrubbing with the brush, absorbent cloth or

sponge – i. define any particular cleaning or scrubbing actions

required such as: brush all surfaces vigorously, butparticularly be sure to use brush vigorously on theinside of the port for at least 30 seconds

6. Rinse Procedure: a. For example: place parts in basket and run them under

running tap water for 20 seconds while moving basket toassure all parts are exposed to running water, or

person responsible for monitoring the baths should bedefined, the type of report or logbook entry should be defined,the trigger points and alert levels should be defined, actionstaken in response to these levels and finally the conditionsunder which the bath is dumped should be defined.

ITEMS FOR A MANUAL PARTS OR MANUAL SURFACE CLEANING SOP1. List of parts or surfaces being cleaned. Define the scope

of the SOP, the maximum number of parts or surface areathis process is designed to clean. Define any level of trainingor certification required to perform this cleaning operation

2. List of Materialsa. Detergent—define full name, manufacturer, manufactur-

er part number, distributor/supplier, and internal partnumber as appropriate

b. Water of suitable purity—define tap water, deionizedwater, distilled water or water-for-injection as is appro-priate

c. Brush, absorbent cloth or sponge—whatever is usedd. Container of suitable size for the detergent solution—

define containere. Any baskets for handling small parts, if usedf. Any rinsing containers, if usedg. Any drying equipment, if usedh. Any required protective equipment, gloves, eye protec-

tion, clothing etc.3. List any requirements for handling prior to cleaning.

The type of things you could optionally list as they applywould be:a. Parts to be cleaned within 4 hours of being processed to

remove grime—if you knew that the grime had a tenden-cy to dry onto the parts and become more difficult toclean, or

b. Tank to be cleaned within 3 days of last use—if you hadvalidated that the tank could be successfully allowed tosit dirty for 3 days and still be cleaned by this manualprocedure, or


g. spongeh. non-abrassive pad

3. Precleaning requirements and procedures:a. When the fermentation run is complete, it is necessary

to carefully shut the process down. First all operatingparameters (agitation, temperature, dissolved oxygen(D.O.) level, pH, and gas feed) must be set from theircurrent control modes (such as “PID”, “D.O.”, “Base”) tothe “Off” mode. Note that the manual air valve on theside of the unit should also be closed as well.Additionally, if a supplemental oxygen feed was used, itwill be necessary to close the gas tank valve and thelines leading from it to the unit. If a recirculating chilleris in use, it should be shut off when the temperaturecontrol is shut off. Feed lines from any addition bottleswhich have been used should be clamped off prior todetaching them from the vessel, and should then beremoved.

i. The next step is to disconnect the vessel from theunit. The temperature probe needs to be removedfrom the thermowell. Remove the motor and placethe protective cap over the agitation shaft. Alwaysdisconnect the water lines by disconnecting theincoming lines prior to the outgoing lines. The airline must be disconnected from the sparger.Disconnect the pH and D.O. probes from the unitand replace their protective caps. The D.O. probepresents an easy removal as you simply unscrewthe thread and gently pull it out. It should beimmediately rinsed off and then wiped dry gently,always remembering to avoid touching the mem-brane at the tip. Some runs will result in an accu-mulation of biomaterial on the probe and it may benecessary to wipe the probe down more vigorouslybut in no case should the tip be touched. Aftercleaning the D.O. probe the tip can be visuallyinspected for damage. The probe should then bestored in a clean area in such a way as to protectthe sensitive tip. Removing the pH probe is usuallynot as difficult a process as inserting it because the

b. Hose down all surfaces with running water assuring thatall parts of surface are rinsed for at least 10 seconds, or

c. Dip part in bucket of rinse water for initial rinse, dip insecond bucket of rinse water for second rinse, and thenplace under running water at the sink for 10 seconds asa final rinse.

7. Drying procedurea. Such as, place parts on rack and allow to air dry, orb. Place parts on tray and place in 210 deg F drying oven

for 40 minutes, orc. Open all ports in tank and allow tank to air dry

8. Any post cleaning handling procedures, such as:a. Define any inspection actions such as: take 10 parts

from the batch and inspect for particulates and visiblesmudges with a 10X magnifying glass. Record results inbatch record. Reject entire lot if there are any failures.Or,

b. Mark tank with “clean tags” recording time, date, andoperator who performed cleaning. The next day after thetank has dried, close the ports to keep out dust. Or,

c. Dispose of used detergent solution down the drain.

An example of a manual cleaning SOP written for manualcleaning of a bench top fermentation reactor adapted from“Fundamentals of Fermentation: Techniques For BenchtopFermentors Part I - E. coli” which was prepared by the R & DLab, New Brunswick Scientific Co., Inc. is:1. Scope

a. For cleaning bench top fermentation reactorsb. Operator training a qualification required

2. Materialsa. Liqui-nox Detergent (Alconox, Inc. Catalog Number

1201)b. Waterc. Kimwipes®d. pH 7 buffere. chemical resistant glovesf. glycerine


the liquid level, as is the case with a side harvest line).The headplate should be detached by loosening andthen removing the clamps that hold it to the rest of thevessel. Those clamps may require rinsing. The remain-ing culture broth should be sterilized or emptied into abucket and disinfected by using bleach or other accept-ed disinfectant prior to disposal. Note that some mediamay be incompatible with this procedure, in which casethe media can be placed into another container for ster-ilization prior to disposal. The headplate should bewashed thoroughly with warm water and then de-ion-ized (DI) water. It may be necessary to scrub accumula-tions of biomaterial off. A pad that won't scratch thesteel is required for this. The agitation shaft, the ther-mowell, harvest and sparger tubes and the short beveledtips of the interior portion of the base-type additionports will often require special attention. All tubes andshafts must be cleaned. Note that there may be someresidual base or acid left in those lines, so extreme cau-tion and the use of chemically-resistant gloves is recom-mended for this procedure. It is often necessary to handwipe surfaces with a paper towel in order to fullyremove residual traces of small particulate debris.

b. The washing of the bottom portion of the vesselrequires the same procedures as the headplate. Notethat the sides of the vessel, particularly where the bafflewas adjacent to it, and side ports (plugged orunplugged) may require special attention.

c. The vessel can now be cleaned by washing with deter-gent, or by using a cleaning solution. If the vessel is tobe sterilized, all standard precautions must be taken.Note that for this purpose, the vessel does not need to besealed except for those previously cited valves and tub-ing which run under the liquid level. It will be necessaryto use water in the vessel. We recommend the use of DIwater, and the fill should be at least as high as your stan-dard level for a run. Unless you have already specificallywiped the residual grease off the top of the glass cylin-der, there should be enough so that the headplate can beclamped to the lower portion of the vessel. Note that it is

shaft will be wet and thus should be relatively easyto remove. However the danger of probe breakageis still very real and extreme care must be takenwhen removing it. It is still necessary to use twohands with one hand at the top of the port acting asa guide to ensure proper removal. A gentle pace forthis is required. If at any point in this process theprobe jams, it is essential to avoid trying to force it.It may be necessary to reinsert it part way andapply a lubricant such as glycerin to the shaft andport in order to effect the probes' removal. Inextreme cases it may be necessary to remove theheadplate with the probe still inside so that you canapproach the problem from both ends. In this case,it is critical to remove the headplate very carefully.(We recommend that you have a spare probe avail-able at all times, in case of breakage.) Once the pHprobe has been removed, it should be immediatelywashed off with warm water. If biomaterial hasaccumulated on the probe, using a sponge (or anequivalent that will not scratch glass) and gentlepressure to clean the surface. The very tip of theprobe should be handled with extreme care and aKimwipe® should be used to gently dry it off afterwashing. The probe should be stored with the tipimmersed in either electrolyte or pH 7 buffer. Thiselectrolyte/buffer can be reused, but it shouldalways be inspected prior to each use for precipita-tion or contamination.

4. Manual cleaning, rinsing and drying descriptiona. Now that the vessel is detached from the unit, it can be

cleaned. To do this it will be necessary to remove anyremaining cotton and foil covering the ports. The rub-ber bulb on the sampler should be removed and rinsedseparately. The glass wool can be removed at this pointas well. The sampling tube is detached and washed sep-arately. The valve on the sampling port and all clampson all tubing connected to ports will need to be open forproper washing. (Note that the media will need to beremoved prior to unclamping any tubing that is below


d. Baskets for handling small parts, if usede. Any rinsing containers or equipmentf. Any drying equipment, if usedg. Any required protective equipment, gloves, eye protec-

tion, clothing etc.3. List any requirements for handling prior to cleaning.

The type of things you could optionally list as they applywould be:a. Degas solution for 10 minutes to remove dissolved

gasses that will dissipate cavitation energy and decreasecleaning performance

b. Turn on heaters and preheat the tank to 120 deg F (50deg C)

c. Parts to be cleaned within 4 hours of being processed toremove grime – if you knew that the grime had a tenden-cy to dry onto the parts and become more difficult toclean, or

d. Do not remove parts from shipping containers prior tobeing ready to clean them promptly – if you know thatunpacking the parts increases the risk of new contami-nants, or

e. Handle all parts with finger cots to avoid adding finger-prints to surfaces – if you do not want to add any newfingerprints to a surface where you are using a cleaningprocess that is only designed to remove particulates

f. Presoak the parts in a defined detergent solution at adefined temperature and time prior to cleaning – forexample presoak parts completely immersed in 1% Terg-a-zyme detergent (1.25 ounces Terg-a-zyme in 1 gallon ofwater) at 120 deg F for 20 minutes prior to cleaning – ifyou know your parts have dried on protein soils that aredifficult to clean without presoaking

4. Directions for making up the detergent solution: Make updetergent solution diluted in water of suitable purity accordingto directions in a container of suitable size at a given tempera-ture.

a. For example: Mix 1.25 ounces of Alconox powdered deter-gent in 1 gallon of 120 deg F (50 deg C) hot tap water whichwill fill to tank to within 1 inch of the top of the tank

neither necessary nor desirable to fasten these clampswith the same force used for attaching the headplateprior to a run, as this could lead to vessel damage.Instead, the lightest possible pressure should be used.The advantage to sterilization is that not only are resid-ual viable organisms killed, but residual debris willloosen and become removable by washing after the ves-sel has cooled. If a cleaning solution is required, use a1% dilution of Liqui-nox cleaning solution (Alconox, Inc.catalog number 1201). Alternatively, if you are using thevessel for consecutive runs with the same media, a rins-ing of it with warm tap water and the DI water may suf-fice. Note that if water will run over a vessel surface thathas grease on it, the grease should be removed by wipingit off with a wet paper towel.

d. In cases where the vessel must be decontaminated priorto cleaning, add water so that the liquid level reachesthe maximum working volume of the vessel. This willhelp prevent biological materials from adhering.

e. Allow vessel to air dry after thorough rinsing5. Post cleaning procedure

a. Store vessel in a clean area. b. Inspect visually prior rinsing and sterilization for next

use.

ITEMS FOR A ULTRASONIC CLEANING SOP1. List of parts the process is intended to clean. Define the

maximum number of parts to put into a batch to becleaned. Define any level of training or certificationrequired to perform this cleaning operation.

2. List of Materialsa. Detergent—define full name, manufacturer, manufactur-

er part number, distributor/supplier, and internal partnumber as appropriate

b. Water of suitable purity—define tap water, deionizedwater, distilled water or water-for-injection as is appro-priate

c. Ultrasonic cleaning tank—define size, frequency, config-uration, manufacturer, and identifying specifications


deionized water – change rinse water when it reaches 50Kohms resistance.

7. Drying procedurea. Place parts on rack and allow to air dry, orb. Place parts on tray and place in 210 deg F drying oven

for 40 minutes, or8. Any post cleaning handling procedures, such as:

a. Define any inspection actions such as: take 10 partsfrom the batch and inspect for particulates and visiblesmudges with a 10X magnifying glass. Record results inbatch record. Reject entire lot for recleaning if there areany failures. Or,

b. Dispose of used detergent solution down the drain.

An example of an ultrasonic cleaning procedure adaptedfrom a manufacturer of small stainless steel and aluminumparts is:

1. Scopea. For the cleaning of small stainless steel and aluminum

partsb. To be carried out by trained and qualified operators

2. List of Materialsa. Alcojet powdered detergent (Alconox, Inc. catalog num-

ber 1450)b. Drain rack with mounting pins to mount connectors on

for cleaning operationc. Ultrasonic cleaning tanksd. Ultrasonic rinsing tankse. Air knife, filtered hot air dryersf. Deionized waterg. Drying ovensh. 10X magnifying glass

i. alkaline resistant rubber gloves3. Flow chart showing handling, cleaning, rinsing, drying,

control and post cleaning handlinga. (see chart on pages 107-108)

b. For another example: Fill the tank within 1 inch of topand turn on heaters. Make up 1% Alconox solution in abeaker (20 g Alconox in 200 ml water in a 250 mlbeaker). Place beaker of Alconox solution in a beakertray with the beaker immersed in the heated water. Fill 3other beakers with deionized water for rinsing and placethem in the beaker tray.

c. Degas solution for 10 minutes to remove dissolvedgasses that will dissipate cavitation energy and decreasecleaning performance. This is particularly important forfreshly made up solutions.

d. Turn on heaters and preheat the tank to 120 deg F (50deg C)

5. Ultrasonic cleaning steps:a. Never place parts or receptacles directly on the bottom

of the unit. It can cause the unit to fail because the partswill reflect the ultrasonic energy back into the transduc-er. Always allow at least one inch between the tank bot-tom and the beaker or receptacle for adequate cavita-tion. Keep solution within one inch of the top of the unitwhen a beaker or tray is in place.

b. If using a tray or basket to lower the parts into the solu-tion, it is better to use a holder that is of open construc-tion, either an open mesh basket or an insert tray, that isadequately perforated for drainage. This also permitsfree access of the sound waves to the parts.

c. Clean the parts to be cleaned in the solution byi. Placing them in basket and immersing them in the

ultrasonic tank for 10 minutesii. After 10 minutes lift basket and allow it to drip off

for 1 minute to reduce dragoutiii. Cover ultrasonic tank after removing and draining

basket6. Rinse Procedure:

a. For example: take basket and run them under runningtap water for 20 seconds while moving basket to assureall parts are exposed to running water, do a final rinseby immersing in a second ultrasonic tank filled with

CLEANING PROCESS FLOW FOR PARTSSpecified Temperature Check Control Check/ Trigger Alert TriggerLimits (Degree C) Frequency By Chart Equipment Points Level Actions

>2 Megohms R/ T Once/Day Technician Trend Cond meter <5Megohms 1 Change DI column

5.5-8.0 Once/Day Technician Trend pH meter Out of spec 1

As required All IQC tech Insp report 10 x Glass 1% failure 1 InformCustomer

500pcs/holder

1% R/ T

R/ T

3% 60-70 Control Box 65±5 Concentration

10.4-11.4 Once/Day Technician log bk pH meter Out of spec 1 Increase/Dilute

2-4kg/c R/ T

3% 60-70 Control Box 64±5 Concentration

10.4-11.4 Once/Day Technician log bk pH meter Out of spec 1 Increase/Dilute

2-4kg/c R/ T

>2 Megohms R/ T

>2 Megohms R/ T

> 2 Megohms

55+5 Once/Day Technician Control Box 50-60

Technician Spin Machine 1

90±10_ Technician Control Box 95±5 1 Check tempprobe

150±10_ Technician Control Box 150±5 1 Check temp probe

0.1% fail QC tech Insp report Microscope10 1 Sorting 100

Corrosion 95+5_ 3pcs/lot Technician Insp report Visual No Corrosion 1 Rework

Standard Operating Procedures 109

CLEANING PROCESS FLOW FOR PARTSSTEP STEP CHEMICAL WATER BATH CHANGE CONTROLS/NUMBER DESCRIPTION USED USED AGITATION TIME (MIN.) NO PARTS. PARAMETERS

Incoming DI water Resistivity

pH

Incoming Inspect Visual

Material input Qty/load

1 Initial Presoak Alcojet Manually 3 min 100K Concentration

Rinse(water jet) Water Manually 1min

2 1st Ultrasonic Clean Alcojet DI water Ultrasonic 5±1min 100k Concentration

(40KHZ) pH

Rinse(water jet) DI Water Manually 1 min Pressure

3 2nd Ultrasonic Clean Alcojet DI water Ultrasonic 5±1min 100k Concentration

(40KHZ) pH

Rinse(water jet) DI Water Manually 1 min Pressure

Rinse(DI water jet) DI Water Manually 1min Resistivity

8 DI rinse (immersion) DI water Air 5min Resistivity

9 Final DI rinse DI water Ultrasonic 2min Resistivity(immersion)

(40KHZ)

11 Spin initial dry Machine 2 min

12 Dryer Hot air 10min

13 Oven Dry Hot air 45min Every Lot

Outgoing inspect Visual

Performance test DI water 4 h Every Lot Visual

Packing Plastic tray/bag As Required

Storage As Required

ALERT LEVEL: 1. INFORM SUPERVISOR OR QC/ENGINEERING/PRODUCT MANAGER



effect), over the entire surface. If areas greater than _ inchsquare show no pebbling, there may be a problem with theunit. Retest with new foil to substantiate the failure. Theunit, along with its latest foil record, should be returned toyour service center for service, if both samples fail. Foilsamples may be retained for future comparison. If futuretests show marked changes over time you may need to ser-vice your unit. Foil samples may be sent with units returnedto the manufacturer for service.

CLEAN-OUT-OF-PLACE IN RACK LOADED SPRAY-IN-AIR WASHER

Standard Operating Procedures for the wash cycle in amachine washer, which does not include the scope and list ofmaterials is:1. Precleaning is only required to remove bulk ingredients

from the items to be washed and should be accomplished bya thorough rinsing. Handling of the items to be washedmust be done according to manufacturers recommenda-tions. All safety regulations of your company should be fol-lowed in handling and transporting the items to be washed.

2. Cleaning chemistry and concentrations of the cleaningchemicals is specific to the soiling on the items to bewashed. The GMP Washer should utilize precise dosingpumps to deliver chemicals to the wash chamber. The dos-ing time will determine the amount of chemical delivered tothe fixed volume of water in the wash chamber.

3. Temperatures in the GMP washer should be user program-mable up to 95 degrees Centigrade.

4. Exposure time of the cleaning chemistry at setpoint temper-ature will account for proper cleaning. GMP Washers vali-date exposure time through continual monitoring of allparameters.

5. Purified Water rinsing (i.e. WFI, USP) is performed toensure removal of all cleaning chemicals at the end of thewash cycle. Conductivity measurement of final rinse watercan be taken to validate rinsing efficiency.

ALUMINUM FOILULTRASONIC CLEANER TEST PROCEDUREIn working with ultrasonics, it is sometimes useful to be ableto test the performance of your ultrasonic washer. The follow-ing aluminum foil test adapted from a Brooks Airforce Baseprocedure (http://www.brooks.af.mil/dis/ic guidelines/attach2.htm) can be useful. 1. Prepare an aluminum foil sample. Obtain a roll of standard

lightweight household aluminum foil. Unroll a piece of foilmeasuring approximately one (1) inch greater than thedepth of the tank by approximately the width (long dimen-sion) of the tank. For example: A tank with dimensions of 9inches long by 5 inches wide by 4 inches deep would requirea foil sample measuring 9 inches by 5 inches. Use scissors tocut the foil. Do not tear.

2. Prepare a fresh solution of ultrasonic cleaning solutionaccording to the manufacturer’s instructions and fill theultrasonic tank to one inch of the brim.

3. If heaters are supplied with the cleaner, turn them off forthe remainder of the test. Also, if the unit is supplied with aHI/LO switch, or intensity, it should be set in the highestposition.

4. Before placing the foil in the tank, turn the ultrasonic clean-er on for five (5) minutes using the timer located on thecleaner. Be sure to turn the timer to 20 minutes, then backto the 5 minutes setting for maximum time accuracy if it isan analog timer. Digital timers can be set directly.

5. Place foil sample which was prepared in Step 1 into thetank in a vertical position. The foil long dimension shouldbe positioned with the long tank dimension. The foil shouldextend downward, but should not touch the tank bottom.

6. Hold the foil, approximately centered front to back, assteady as possible. Turn the ultrasonic cleaner on for exactly20 seconds.

7. Turn the cleaner off and remove the foil sample. Shake thefoil sample dry of any water droplets. Allow foil to air dry,being careful not to wrinkle the foil.

8. Properly functioning units will result in foil surfaces thatare uniformly “peppered” (covered with a tiny pebbling


Function Possibility Prog. 11

COLD W.F.I RINSE 1 0 to 30 minCOLD W.F.I RINSE 2 0 to 30 minCOLD W.F.I RINSE 3 0 to 30 minCOLD W.F.I RINSE 4 0 to 30 min

HOT W.F.I RINSE 0 to 30 minHOT W.F.I TEMPERATURE up to to 95° C

During the inspection and qualification of the GMPWasher, verification of the effectiveness of the inventory sys-tem as described above must be demonstrated. Testing proto-cols must be established. An example is as follows:

One test protocol for establishing cGMP washer operationthat can be used can be done by the riboflavin U.V test:

Soil the parts with a Riboflavin solution. Let them dry for 2 hours and then soil them again.Let them dry overnight.Perform the cycle 11 as follows (this cycle must have nodrying).

After cycle, the wet parts are checked with an U.V lamp.Does Riboflavin remain?

Test 1 Yes / NoTest 2 Yes / No

Glassware: Test 1:Test 2:Test 3:

After all of the preparation of the cycle description, loadpatterns and testing of the spray coverage is completed, theoperators must be trained to load/unload the racks is an ef-ficient manner.

6. On Drying models, a drying step with temperatures up to110 degrees Centigrade can be performed. All drying air isHEPA filtered.

7. Postcleaning handling of the washed items must be per-formed in compliance with internal company proceduresthat assure cGMP compliance.

POSSIBLE SETTINGS FOR WASHER CYCLESFunction Possibility Prog. 11

PREWASH 1 PERIOD 0 to 30 minPREWASH 1 TEMPERATURE up to to 95° CPREWASH 1 DETERGENT 0 to 6 min



WASH PERIOD 0 to 30 minWASH TEMPERATURE up to to 95° CWASH DETERGENT 0 to 6 min

W.F.I RINSE 1 0 to 9

ACID RINSE PERIOD 0 to 30 minACID INTAKE 0 to 6 min

W.F.I RINSE 2 0 to 9


at 4.5 gallons/min at 345-1035 Kpa pressure for a 4 inchsystem. Use the chiller to maintain the temperaturebelow 35 deg C.

f. The cleaning progress can be monitored by observing thecolor of the effluent. Circulate continuously or by alter-nately circulate/soak for 15 minute intervals. Circulatefor at least 2 hours for a 4 inch system. Continue untilthe return effluent is no longer badly discolored.

g. When cleaning is completed, stop recirculation, drainmix tank to waste. Flush residual cleaner with feedwater at 4.5 gallons per minute (for 4 inch systems) at345-518 Kpa pressure (for 4 inch systems) sending bothbrine and product side to drain. Collect sample of efflu-ent in a small jar, cover, shake and observe foam indicat-ing the presence of detergent. Rinse jar between uses.Continue flushing until no foam is observed in the shak-en sample jar.

5. Posta. Perform post treatment procedures and return block to

normal operations. Observe pressure and performanceto determine if further treatment with a citric cleanersuch as Citranox (Alconox, White Plains NY USA cat no1815) may need to be performed to reduce particulateand inorganic scale buildup.

CLEAN-IN-PLACE LARGE TANK FILL, SOAK AND AGITATE CLEANING 1. Scope

a. To clean a large stainless steel tank to remove a blendedmaterial that contains a thick high melting wax.

b. Operators must be trained and qualified2. Materials

a. Detergentb. Brushc. Bucketd. Recirculation pumpe. Hot water hose

3. Precleaning conditionsa. Tank with waxy residue shall be cleaned within 24 hours.

CLEAN-IN-PLACE ULTRAFILTRATION BRINE WATER FILTER SYSTEM CLEANING1. Scope

a. To clean a large ultrafiltration brine water filter system

b. Operators must be trained and qualified2. Materials

a. Good quality chlorine-free tap water (total dissolvedsolids less than 5,000 mg/l)

b. 316 stainless steel mix tank sized appropriately to thesystem (minimum of 3 minute retention time during cir-culation) with an exhaust fan, mixer, cooling coil, andtemperature indicator

c. 316 stainless steel centrifuge pump sized for appropriateflow rates

d. 10 micron cartridge prefilter

e. Flow meters

f. Suitable flexible piping, sampling ports and port connec-tors

g. Terg-a-zyme (Alconox cat no 1350) enzyme cleaner3. Pre cleaning conditions

a. Filter system suffering from biofouling and/or inorganicparticulate build-up

4. Cleaning, rinsing and drying descriptiona. In large systems, isolate the 1 block of filter elements to

be cleaned, allowing the rest of the blocks to operatenormally.

b. Flush filter element block with water once through (10gallons for a typical 4 inch diameter filter element unit –different sized units would take proportionally more orless water)

c. In the mix tank, dissolve enough Terg-a-zyme to make a0.5% solution taking into account the volume of thetanks and filter element blocks (2.5 gallons for a 4 inchsystem).

d. Turn on mixer to dissolve detergente. Circulate the cleaning solution through the filter block.

Send the first 20% of the solution to drain via the brinereturn valve. Circulate the rest of the cleaning solution


Note, adjustment of the recommended 4 hour clean-ing time may need to be done as experience is gainedwith specific soils and tanks. This cleaning regimen isdesigned for a wax, which melts around 200 deg F inmind. Many soils may not require heating to an excess of200 deg F. Many waxes are melted by 170 deg F and thisprocedure could be adapted to use a lower temperaturefor lower melting waxes of for residues that did notrequire such high temperatures.

The previous sections in this chapter give examples ofstandard operating procedures. The types of considerationsand procedures could be adapted to many other kinds ofcleaning. There are many types of cleaning machines, eachwould have its own machine specific standard operating pro-cedure. You could have procedures for a range of machinessuch as vibratory washers, oscillating washers, reel-to-reelwashers, spray cabinet washers, and a range of other industri-al washers. As long as the general topics outlined here are cov-ered a successful SOP can be written. The machine manufac-turer should be able to help you understand the proper use ofthe machine. You can add your own understanding of your sit-uation to adapt this to a successful SOP.

REFERENCESDuPont Company Bulletin 507 “Cleaning Procedures” p 1-4 (1982)Durkee, JB, The Parts Cleaning Handbook, Gardner Publications,

Cincinnati, 1994Dollard, R M Keeping Validation Current: Elements of an Effective

Change Control Program, Philadelphia. presented at CleaningValidation and Cleaning Processes Jan 14-15 Philadelphia, PA (2002)

James Fry, Private communication regarding Lancer Washers May 2002

RESOURCESwww.alconox.comwww.lancer.comhttp://www.brooks.af.mil/dis/icguidelines/attach2.htm

b. Tank ports should be kept closed while in holding4. Cleaning, rinsing and drying description:

a. Fill tank full with hot plant water

b. Add detergent recommended for the type of residue inthe tank (see note)

c. Turn on mixer wipers to agitate

d. Turn on tank heaters to raise temperature above 200 degF (see note)

e. Turn on pumps and connect pipes to recirculate throughany lines that need to be cleaned. Note pumps should beoperated with sufficient head or at a slow enough speedto avoid cavitation due to foam formation.

f. Run for 4 hours. Depending on how well sealed the tankis, you may need to top up the solution to compensatefor evaporation

g. Open top and manually scrub with a brush dipped in thehot solution the unexposed top sections of the tank thatwere not immersed by the cleaner

h. Drain the tank

i. Fill the tank with hot plant water that had been heated to200 deg F with the agitation and any recirculation pumpturned on for 10 minutes.

j. Use a hose with hot water to rinse the top part of thetank above the immersion line

k. Drain the tank

l. Visually inspect the interior of the tank and clean anyknown problem areas with a hot bucket of detergentsolution and a brush.

m. Rinse the tank thoroughly with hose of hot plant wateror a spray ball apparatus with hot plant water.

n. Drain the tank.o. Allow tank to air dry with ports open

5. Postcleaning conditionsa. Tag the tank as clean with a date to allow control for

clean hold times

b. Record cleaning in equipment log, recording date, time,and operator

CHAPTER EIGHT

Cleaning ValidationCleaning validation is typically performed for pharmaceuticaland other GMP manufacturing processes. These include phar-maceutical, bio-pharmaceutical, bulk-pharmaceutical, med-ical-device, cosmeceutical and clinical-diagnostic manufactur-ers. The validation is specific to the detergent and methodused for cleaning.

To perform a cleaning validation one needs a validationmaster plan. The validation is best done during InstallationQualification (IQ), Operational Qualification (OQ), andPerformance Qualification (PQ) of manufacturing equipmentand operations. The validation provides documentation andevidence of reproducible successful cleaning. The validationconsists of a final report and a set of procedures to maintain avalidated state.

The master validation plan would typical dictate that thefinal report will have sections such as the following:

• Objective

• Responsibilities

• Equipment/products/ procedures

• Tests Acceptance limits

• Analytical Methods

• Sampling procedures and recovery

• Cleaning process design

• Data analysis

• Assumptions

• Change control/maintenance

• References

The objective of the validation might be to ensure product,

Cleaning Validation 119118 The Aqueous Cleaning Handbook

• Sampling method selection,

• Setting residue acceptance criteria,

• Methods validation and recovery studies, and finally

• Writing a procedure and training operators.

This procedure is used to document acceptable residuesthree or more times and then a rational monitoring programto maintain a validated state is put in place. If changing anypart of the procedure or cleaner, first clean the new way, col-lect data and then clean the old way before using any equip-ment while in the process of validating the new procedure.

Residue identification—in a pharmaceutical manufactur-ing environment this involves: the cleaner, primary ingredi-ents, excipients, decomposition products, and preservatives.This document is intended to help with the cleaner residueidentification.

Residue detection method selection—for cleaners caninvolve specific methods for specific cleaner ingredients suchas: high-performance liquid chromatography (HPLC), ionselective electrodes, flame photometry, derivative UV spec-troscopy, enzymatic detection and titration. It can also involvenon-specific methods that detect the presence of a blend ofingredients such as: total organic carbon, pH, and conductivi-ty. The FDA prefers specific methods, but will accept non-spe-cific methods with adequate rationales for their use. For inves-tigations of failures or action levels, a specific method is usual-ly preferable. (A later section of this chapter lists references toseveral methods for each cleaner brand.)

Sampling method selection—for cleaners involves choos-ing between rinse water sampling, swabbing surfaces, couponsampling, or placebo sampling.

Rinse water sampling involves taking a sample of an equi-librated post-final rinse that has been recirculated over all sur-faces. Rinse samples should be correlated to a direct measur-ing technique such as swabbing.

Swabbing involves using wipe or swab that is moistenedwith high purity water (WFI) that is typically wiped over adefined area in a systematic multi-pass way always going fromclean to dirty areas to avoid recontamination – i.e. 10 side byside strokes vertically, 10 horizontally and 10 each with the

Cleaning Validation 121

worker, and environmental safety while controlling the risk ofcross contamination. The people or departments involved incarrying out the validation with defined responsibilities wouldinclude:

• Validation Specialist—writes, coordinates validation

• Manufacturing—write SOPs, do training

• Quality Assure/Control—approve and do analyticalmethods

• Engineering—inform of changes, provide equipmentdata

• R&D—recovery, validate methods, transfer methods,new cleaners

In the course of the validation one can simplify things byassembling an equipment matrix that defines all shared anddedicated equipment. Work can be done to justify whichequipment represents worst case hardest to clean equipmentthat in turn must have a full validation done to represent thedocumented easier to clean equipment.

By the same token, a matrix of residues can be assembledto classify into residue groups of types that are cleaned by agiven set of conditions and then determine which is hardest toclean. In this way, a worst-case residue or worst-case for aresidue class can be confirmed. A matrix of cleaning proce-dures can then be assembled in order to standardize on as fewprocedures as is practical to improve execution and trainingfor these procedures.

It is important to validate a worst case scenario and to jus-tify the choice of “worst-case.” The worst case is typically cho-sen based on product solubility in cleaner or detergent, thetoxicity of the products or degredants being cleaned, dosesizes and size normal therapeutic dose (smaller may be morecritical to validate), hardest to clean equipment/residue, andworst interactions with the next batch to be cleaned.

The cleaning validation for a specific cleaner involves test-ing for acceptable residues on pharmaceutical manufacturingor medical device surfaces. The validation involves:

• Residue identification,

• Residue detection method selection,


Limit (mg/cm2 or L) = ADI carryover – see below (mg) X Smallest Next Batch (kg) Size of Shared Equipment (cm2 or L) X Biggest Daily Dose or of Next Batch (kg)

ADI carryover (mg) = LD50 by administration route (mg/kg) X body weight (kg) X (1/ 10,000 or 1/1000*)

Comparison calculation of limit based on no more than 10ppm carryover:

Limit (mg/cm2) = 10 mg residue on just cleaned surface X Next Batch Size (kg or L)

1 kg of L of next product X Size (cm2 or L) shared equipment

Note that for many residues one can validate a visualdetection limit on the order of 1-4 ug/cm2. It is possible thatthe visually clean criteria will be the most stringent criteria.

Example with a cleaner that has an rat oral LD50 of over 5g/kg, the ADI calculation using a 70 kg person and a safety fac-tor of 1000 gives a result of 350mg (5 g/kg X 70 kg / 1000 ).The calculated residual acceptance limit for a 2000 kg mixerand line where there might be a next smallest batch of 1000kg, and the area of the mixer and filling equipment which isall used in the next batch is 100,000 m2 and the daily dose ofthe next product is 0.005 kg results in a calculated residualacceptance criteria of 700 mg/cm2 (350 mg X1000 kg/(100,000cm2 X 0.005 kg). By comparison, the 10 ppm in next batchlimit gives an acceptance criteria of 100 ug /cm2 (10 mg X1000 kg/(1 kg X 100,000 cm2) X 1000ug/mg. In this case, it islikely that you will be able to show that you can visually detectdown to 4 ug/cm2 and since you need to have a visually cleansurface, your most stringent acceptance criteria will be thevisual limit.

Note that in this example you are trying to avoid gettingmore than 350 mg of residue in a daily dose of the next prod-uct. In the case of small final filling equipment such as fillingneedles for vials or tablet punches and dies, you might need todo separate residue studies on the filling needles or punches tobe sure that there was not enough residue just on that equip-ment to contaminate the first few bottles or tablets of the nextbatch with a residue of 350 mg/daily dose.

If the safety based limit in this example is set at 100ug/cm2. Then this limit can be expressed as a rinse water con-


flip side of the swab in each diagonal direction. For TOCanalysis very clean low background swabs or wipes and sam-ple vials such should be used. The Texwipe large Alpha Swab714A or 761 have been used, these are available in kits withclean sample containers.

Quartz glass fiber filter papers have been used successfully.Coupon sampling involves the use of a coupons or an actualremovable piece of pipe that is dipped into high purity waterto extract residues for analysis.

Placebo testing involves using placebo product and analyz-ing for residues from the previous batch.

Setting residue acceptance criteria—in pharmaceuticaland medical device manufacturing requires setting residueacceptance levels for potential residues such as the activedrug, excipients, degradation products, cleaning agents,bioburden and endotoxins. These levels are determined basedon potential pharmacological, safety, toxicity, stability, andcontamination effects on the next product using that surfaceor equipment. Limits are typically set for visual, chemical, andmicrobiological residues.

The cleaning agent limits are generally covered underchemical criteria. Chemical limits can be expressed as a maxi-mum concentration in the next product (ug/ml), amount persurface area (ug/cm2), amount in a swab sample (ug or ug/ml),maximum carryover in a train (mg or g), or concentration inequilabrated rinse water (ug/ml). You should have a calculatedsafety based acceptance limit, and you can have a lower inter-nal action level, and a lower process control level based onactual manufacturing and measuring experience.

Cleaning agent safety based limits are typically calculatedfrom a safety factor of an acceptable daily intake (ADI), a(1/1000 or more) reduction of an LD50 preferably by the sameroute of administration, or reproductive hazard levels. If thecalculated limit is found to be higher than a less than 10 ppmcarryover to the next batch, then the limit can be set to themore stringent 10 ppm carryover level for the safety basedlimit.

Calculated safety based limit in mg/cm2 or mg/ml of clean-er residue on a just cleaned equipment:


DIRECTORY OF CLEANER RESIDUE DETECTION METHODS FOR EACH ALCONOX DETERGENT

There are some things that are unique to the cleaner beingtested. As and example, the following is excerpts from theAlconox Cleaning Validation References for cleaners made byAlconox, Inc. show a variety of residue detection methods forthese cleaners (see the directory table). As discussed undermethods validation, different analytical methods will requiredifferent procedures for validation. The FDA, the InternationalConference on Harmonization (ICH), and European Union(EU) have all defined validation requirements for analyticalmethods used in manufacturing pharmaceuticals. The UnitedStates Pharmocopeia (USP) gives method validation guide-lines in Chapter 1225. Residue detection methods can varyfrom non-specific methods such as total organic carbon (TOC)to selective methods that have been shown to be specific at a95% confidence level in the conditions of use without signifi-cant bias or interference from impurities, degredants, excipi-ents, and other ingredients. The FDA often prefers the use of


centration of 100 mg/L in a post final rinse using 100 L ofrecirculated to equilibrium rinse water (0.1 mg/cm2 X 100,000cm2/100 L). This same limit could be expressed as 6.25 ug/mlor ppm total organic carbon (TOC) in a sample for a residuethat is 10% TOC by weight in a 20 ml swab sample from a 25cm2 swab area where 50% recovery has been established ((25cm2 X 100 ug/cm2) X 50% recovery) X 10% TOC/20 ml. Thesame safety limit can be expressed several different ways.

The methods validation and recovery study—is the use ofthe sampling and detection method on known spiked surfacesat representative levels, typically spiked at 50%, 100% and150% of the acceptable limit and at lower expected actual lev-els to show linearity with documented % recovery as analyzedand to determine the limit of detection and limit of quantita-tion. Ideally the expected values and limits should be multiplesof the limits of quantitation. The % recovery is used to corre-late amount detected with amount assumed to be on the sur-face as an acceptable residue. This is a good time to considerwipe or rinse sample storage conditions and time limits to getthe sample analyzed. Rinseability profiles showing the com-plete rinsing of the individual detergent ingredients should beundertaken if the solubility of any detergent ingredients or therinseability after drying is in doubt. In some casesbioburden/endotoxin levels may need to be validated. It is rec-ommended that this process be done separately from thecleaning process so that the cleaning validation can be com-pleted while the lengthier biobuden/endotoxin evaluation isdone.

The written procedure and training of operators—involveswriting out assigned responsibilities, protective clothingneeds, equipment disassembly needs, monitoring procedures,documentation needs, labeling of in process and cleanedequipment with cleaning expiration date, post cleaning inspec-tion procedures, storage conditions, and inspection requiredbefore next use. The operators then need to be trained and cer-tified in the procedures.


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ALCONOX® • • • • •

LIQUI-NOX® • • • • • •

TERG-A-ZYME® • • • • • •

ALCOJET® • • •

ALCOTABS® • • • •

DET-O-JET® • • • •

DETERGENT 8® • •

CITRANOX® • • • • • •

LUMINOX® • •

CITRAJET® • •

the new process with monitoring to prove that the newprocess gives the same validated results as the old process.

The final section of the final validation report would havethe references to any standard methods, journal articles, orgovernment documents.

In selecting an aqueous cleaner for cGMP manufacturingwhere a cleaning validation is required, consider both the effi-cacy of the cleaner and the ability of the cleaner manufacturerto support validation efforts.

Things one should look for from a cleaner supplierinclude:

• Lot traceability of the cleaners

• Certificates of Analysis for the cleaners

• Consistent manufacturing

• Ingredient disclosures under confidentiality

• Cooperation with audits and quality questionnaires

• Ingredient toxicity data

• Ingredient reactivity information to help determinedegredations and interactions

• Cleaner shelf life information

• Residue detection method information

• Residue sampling information

• Acceptance limits information

• Recovery information

• Residue detection methods validation information

• Assistance with written cleaning procedures

To discuss the specifics of these validations with the exam-ples given with Alconox detergents, contact MalcolmMcLaughlin at 914-948-4040, ext. 160, or write [email protected]


selective methods that have been shown to be specific, particu-larly for investigations.

Non-specific methods such as TOC are commonly usedwhere the limits of detection and quantitation are well belowresidue acceptance limits. TOC also detects virtually all organ-ic residues, in ways making it superior at showing overallcleanliness. The following table reviews method validationrequirements:

TABLE: ANALYTICAL METHODS VALIDATION CONDITIONSMethod Accuracy Precision Linearity Reproducibility Selectivity Specificity LOD LOQ Ruggedness

(Repeatability)

HPLC X X X X X X X X X

GC X X X X X X X X X

TLCX X X X X X X X X

IC X X X X X X X X

Wet Methods X X X X X X X X X

UV-vis X X X X X X X X X

TOC X X X X X X

HPLC- high performance liquid chromatography, GC – gas chromatography, TLC – thin layer chromatography, IC ion chro-matography, UV-vis – ultraviolet visible spectroscopy, TOC- total organic carbon, Wet methods- titrations/assays

In the final report the next section would deal with clean-ing process design with references to standard operating pro-cedures and how they were evaluated. This would be followedby a section of data analysis with statistical justification forthe conclusions reached. A defined procedure for changingvalidated processes is needed. This should address the level ofapproval and review needed for specific changes. Provisionsfor emergency changes should be considered. There should bea list of assumptions made that would need to be reviewedwhenever anything is changed.

It also makes sense to include a review of validatedprocesses during the annual product review (APR) to see thatthe interim period of small changes has not cumulativelymade large changes that exceed the assumptions made (ie.hardest to clean, or most toxic) that would require revalida-tion. Typically changing a cleaner would require revalidation.For some kinds of changes it is appropriate to continue opera-tions the old way while simultaneously and sequentially doing


CHAPTER NINE

Wastewater Treatmentand Cleaner RecyclingWastewater treatment is imperative for reducing the level ofcontamination present in the water from a cleaning system,which may include insoluble oils, emulsified oils, other dis-solved organics, suspended solids, and dissolved inorganicsolids such as chlorides, nitrates, phosphates, and metals.

Treatment requirements before discharge to the localsewer vary from state to state, and municipality to municipali-ty. Most local governing authorities enforce acceptable criteriafor pH, biological oxygen demand (BOD), and chemical oxy-gen demand (COD). Specific discharge criteria will be notedon your discharge permit.

A typical wastewater treatment system involves a few com-mon operations, including pretreatment, which is designed toreduce the volume of solids and wastewater.

TYPES OF CONTAMINANTS• Solids—Acid conditions are used to enhance breakup of

the oil-water emulsion. The water layer is pumped to achamber, where a polymer flocculent is added. Thewastewater is then pumped to a clarifier, where much ofthe oil condenses into a floc, which settles to the bottomof the chamber.

Flocculated solids are transferred to a filter press,where they are dried in preparation for disposal. Thesupernatant liquid is pumped to a process tank wherethe pH is raised in order to promote precipitate metals.Flocculation of the metals is achieved upon addition of apolymer.

Wastewater Treatment and Cleaner Recycling 129

REFERENCES 21 CFR 211 and Proposed RevisionsBrewer, Rebecca Designing and Documenting Your Cleaning Validation

Program to Meet FDA Requirements, Washington GroupInternational , Philadelphia. presented at Cleaning Validation andCleaning Processes Feb 1-2 Philadelphia, PA (2001)

Cooper, “Using Swabs for Cleaning Validation: A Review” CleaningValidation, IVT, p 74-89 (1996)

FDA “Biotechnology Inspection Guide” (1991)FDA “Guide to Inspection of Bulk Pharmaceuticals Chemicals” (1991)FDA “Guide to Inspection of Cleaning Validation” (1993)ourman and Mullen, “Determining Cleaning Validation Acceptance

Limits for Pharmaceutical Manufacturing” Pharm Technol. 17 (4), 54-60 (1993)

Leblanc, “Establishing Scientifically Justified Acceptance Criteria forCleaning Validation of Finished Drug Products,” Pharm Technol 22(10), 136-148 (1998)

Mowafak, Nassani, PhD, “Qualification of Quality Control inLaboratories,” Journal of Validation Technology, Vol 8, No 3, 260-272(May 2002)

RESOURCESwww.alconox.comwww.ivthome.comwww.cleaningvalidation.comwww.fda.gov.comwww.fdainfo.com


an activated carbon filter, capable of absorbing materialmany times its own weight within its extensive pore net-work.

However, activated carbon is used for organic materi-als only. Metal contaminants and other inorganic materi-als will remain dissolved or suspended in the wastewater.An activated carbon filter can be used as one of the laststages before discharge or recycling, in order to assurecleanliness. Filters can be arranged in series or parallel.A parallel arrangement allows for change-out of one fil-ter while the others remain operational.

• UV Systems—Ultraviolet (UV) light is an effective meansto destroy biological organisms. A UV-oxidation systemcan be employed, as necessary, to reduce the BOD of thewastewater.

SELECTION CONSIDERATIONSThe following are basic guidelines for selection of a waste-water treatment system:

• Treatment options should be studied by an engineer toassess process alternatives. The system should be opti-mized for proper flow rates, filter capacities, through-puts, etc.

• Design, maintenance, and operations should have con-tingencies for downtime.

• Capital and operating costs may justify the recycling ofwastewater in a closed-loop system.

CLEANER RECYCLINGAs numerous ozone-depleting compounds became legislatedout of use, a large number of companies chose aqueous clean-ing solutions as replacement alternatives to solvent degreasing.

In the early transitional days, many process and manufac-turing engineers were concerned that aqueous processeswould reduce part quality and throughput while creating addi-tional waste and wastewater treatment problems and costs.

Some alternatives to aqueous cleaning systems include“drop-in” semi-aqueous or solvent-based cleaning systems.However, these are not without their own problems, namely


• Oils—Capability to remove trace quantities of floating oilin a cleaning bath not only improves cleaner perfor-mance, but extends bath life. Further, upon filtering outany particulates or fines, oils collected may be evaluatedfor reuse, rather than destined for disposal.

Traditional mechanical separation of oil from waste-water involves the use of skimmers, tank overflow, anddecanting methods. Such out-of-process, post-produc-tion, end-of-pipe wastewater treatment approaches tendto perform less efficiently in a continuous manufactur-ing operation and contribute to disposal problems.

EQUIPMENT OPTIONS• Evaporators—Evaporation is commonly used to reduce

the volume of water for further treatment. The contami-nants then become concentrated within the bottomsludge and the water is transferred to a holding tank,where it is allowed to cool to room temperature. Thewater is either discharged to drain (with the necessarypermits and approvals in place), or undergoes furthertreatment.

• Separators—Gravity separation of nonemulsified oil inwastewater can occur in the clarification tank. The influ-ent and effluent flow rates are optimized to allow effi-cient separation of the lighter oil layer from the water.An inclined plate can be used to direct the flow of the oillayer away from the wastewater.

A current method of oil-water separation appliesBernoulli’s principle, whereby the wastewater is splitinto two laminar flows. Oil is continuously collected andconcentrated in a second chamber, which is separated bya baffle from the primary chamber and a reduced-pres-sure area below. The reduced pressure directs the flow ofwater down, away from the second chamber.

The oil is recovered from the top of the concentratedlayer, when the layer reaches a designed thickness. Higher-quality oil is recovered this way, and is able to be reused.

• Activated carbon—Suspended organic materials can beremoved from the waste stream with the application of


very fine suspensions of particulates).

• Physical separation—such as cooling and skimming,settling, and emulsion breakup. Cooling solutions allowemulsions and suspensions to break. Settling allowswater-insoluble materials to separate by density; heavysludge will generally settle to the bottom when a suspen-sion breaks. In emulsion breakup, light oils will general-ly rise to the surface and the overflow can be physicallyskimmed off with oleophilic wicks or cycling bands ofoleophilic material, leaving reusable cleaning solution.

• Solution recharge—is when a detergent solution life canbe extended by using the detergent to exhaustion, andthen adding some amount of additional detergent (forexample, 50 percent of the original dose). The concentra-tion of useable detergent will then be sufficiently raisedto a level where effective cleaning will occur.

• Ultrafiltration—is when multiplex membrane filters arepackaged into a variety of cartridge configurations andintegrated into the cleaning process. A feed solution ispumped through the filters’ cartridge and split into apermeate or filtrate (material retained by the membrane)and retentate (fluid retained by the membrane). The soil-free permeate stream is then recycled back to the partswasher.

FILTER SELECTIONToday, many kinds of filters are available for ultrafiltrationdue to advances in membrane types and the continued evolu-tion of systems with better temperature and chemical stability.For example, extremely hydrophilic (water-absorbing and oil-repellent) polymeric membranes have been developed to resistfouling by free oils, emulsions, and other hydrophobic solutesin order to achieve efficient filtration rates over extended peri-ods.

Filters can be either symmetric, with fairly uniform porediameters throughout the membrane, or asymmetric, consist-ing of a thin “selective” layer over a thick, porous substructure.

Membrane selection is critical to the effectiveness of anyrecycling system. Before deciding on a system, users shouldask the following questions:


employee health concerns, flash points (flammability), andpossible worker discomfort due to odors.

One public lab where solvent replacement work has beendone is The University of Massachusetts at Lowell’s Toxics UseReduction Institute. The Institute has shown the viability ofaqueous cleaning in industrial settings. Aqueous cleaning hasprovided a sound alternative to vapor degreasing in as manyas four out of five applications that the Institute reviews on alaboratory scale for industry clients.

Modern closed-loop aqueous cleaning systems removecontaminants from both the cleaning bath and rinse water,and compared to solvent cleaning systems, may be relativelyinexpensive to install.

Recycling can help reduce or eliminate liquid waste bytrading dilute liquid waste for more easily disposed solidwaste in the form of spent filters or concentrated sludge.Recycling can also help reduce detergent consumption inorder to get more parts clean per pound or gallon. It may alsosave time and increase throughput while reducing system set-up requirements.

The first place to install recycling equipment is in the rinsewater portion of the cleaning system. In sequential tank clean-ing this is accomplished by using a series of countercurrentcascading rinse tanks with each tank’s water being progres-sively reused. This type of system minimizes water usage whileensuring that the final rinse stages contain the cleanest water.(Because less water is used, recycling is also easier and lessexpensive to install.)

In addition, it is easier to recycle the detergent solutionseparately from the rinse water because the equipment used ismerely separating soils, not trying to create high-purity water,for which you need activated carbon, deionizing resins orreverse-osmosis. Treating cleaning solutions can be accom-plished through one or more of the following procedures:

• Physical filtration—uses gravity or low-pressure pumpcartridges at one to 100 micron levels of filtration toremove suspended particulates.

• Microfiltration—uses low-pressure pumps, dead-end, orcross-flow filter membranes to realize 0.1 to 1.0 micronlevels of particulate filtration (used to break and remove


content of both the recycled bath and the rinse water used. In a separate system, rinse water must be purified. The

rinsing recycle systems can be designed to deliver water to alevel that leaves parts able to meet required cleanliness stan-dards.

In addition to particle, micro- and ultrafiltration, theserecycling systems may also use reverse osmosis (RO) in con-junction with microfiltration in order to protect the filtermembrane. Activated carbon may be used for the removal ofthe majority of organic contaminants. Ion exchange is anothertype of system that uses specially designed resins to capturecations and anions such as chlorine, heavy metals, calcium,and magnesium. Since these types of cations and anions maybe considered hazardous waste, they must be shipped back tosuppliers for regeneration.

MONITORING AND CONTROLLING CLEANING BATHSIn order to extend bath life or recycle solutions, the cleaningbath should be monitored to determine when the solution canbe recharged with detergent and when it is spent, mandating afresh batch. There are numerous sophisticated analyticalchemistry techniques, such as FTIR (Fourier TransformInfrared Spectroscopy), HPLC (high pressure liquid chro-matography), COD (chemical oxygen demand) and TOC (totalorganic carbon), for analyzing recycled cleaner. FreeAlkalinity, a process which measures unreacted builder in thecleaner, can also be used, as well as Total Alkalinity, whichmeasures total alkalinity as well as the alkalinity consumed inthe cleaning process due to sludge formation or hydrolysis ofanimal or vegetable-based oils. Neither Free Alkalinity norTotal Alkalinity, however, measure the level of surfactants, ren-dering them inappropriate in procedures which depend on theremoval of soil.

Some very simple, yet effective, techniques can be used tomonitor bath life, including:

• Conductivity—The measurement of ionic content of thecleaning solution using electrodes connected to a con-ductivity meter. This is a useful technique for figuringout when to add more detergent to a cleaning solutionwith high ionic content, such as those based on salts


• Surface chemistry—Has the membrane been engi-neered for easy cleaning or to resist fouling by free-float-ing and emulsified oils?

• Stability—Is it physically and chemically stable toward abroad range of pH and aggressive chemicals?

• Pore size—Has it been designed to ensure complete pas-sage of all cleaner components while sufficiently retain-ing the oils?

• Temperature tolerance—What is the membrane’s tem-perature tolerance?

While not all aqueous cleaning applications require the useof membrane-based filtration, their use can be especially help-ful in achieving steady conditions, desirable for maintainingquality control in high-production applications. Detergentsmust be selected for their compatibility with the specific mem-brane employed, and vice versa.

CLOSING THE LOOP ON AQUEOUS CLEANING AND RINSINGThere are a number of methods for removing contaminantsfrom aqueous-cleaner solutions. These are selected for particu-lar applications based on the size of the contaminants.Particulates may be removed using settling tanks, chip bas-kets, media filtration, or canister filters. Oils are collectedusing skimmers and coalescers. Most of the remaining conta-minants can be removed using micro- and ultrafiltration.Usually you have separate rinse water recycling and cleanersolution recycling. Cleaners are recycled using physical filters,oil separators, ultrafiltration, and microfiltration.

Microfiltration uses a membrane with pore sizes from 0.1to 1.0 microns, while ultrafiltration pore sizes range from0.0005 to 0.1 microns.

Ultrafiltration membrane pore sizes are also specified bymolecular weight cutoffs (MWCOs). Contaminants with adiameter greater than the membrane’s MWCO are thus filteredout.

It is important to keep in mind that both micro- and ultra-filtration are pressure-driven processes. Neither will rejectsalts, which can adversely affect its performance and make dis-posal necessary. It is therefore important to monitor the salt


fying or dispersing detergent to remove oils or particulate typesof soils, refractometry can be an effective means of measure-ment and control. Foam height is most applicable to cleanersbased on foaming surfactants that rely on emulsification ofoily soils for their removal. When cleaning with an alkalinedetergent and the soil is either acidic or neutralizing in charac-ter (as most soils are), pH can be used as a control measure.

TABLE 7A BASIC MONITORING AND CONTROL TECHNIQUE SELECTION BASED ON TYPE OF DETERGENT USEDConductivity Ionic cleaner removing nonionic soil such as a high

alkaline cleaner used for degreasingRefractometry High emulsifying and dispersing cleaner used on

mixed particulate and oily soilFoam height High-foaming cleaner used to clean oily soilspH decrease Alkaline cleaner used to clean acidic or hydrolyzable

soils that react with the cleaner (most soils are acidic or hydrolyzable)

pH increase Acidic cleaner used to clean an alkaline or neutral soil

ECONOMIC FACTORSOne must keep in mind that where detergent recycling is con-cerned, it is possible to be penny-wise and pound-foolish. Itmay not be worth risking inadequate, or even uncontrolled,cleaning simply to get every last penny of performance from adetergent solution.

The cost of installing recycling and reuse equipment andprocedures must be weighed against the cost of disposal andsolution use. The value of the parts being cleaned, theincreased risk of cleaning failure with each new part cleanedand the chance of cleaner exhaustion or soil redeposition mustall be considered.

One question that needs to be asked and answered is:

Is it cheaper and better to send partially used cleaner to drain and make up a fresh batch of cleaner?

With nonhazardous detergents and wastes, probablycheaper and better to send to drain and make fresh solution.With easily treated hazardous wastes, perhaps not. Where reg-


(potassium hydroxide or sodium metasilicate, for exam-ple). Conductivity will drop as soils react with the salts.This is not a useful technique for monitoring high emul-sifying cleaners that rely on surfactants for a significantpart of the cleaning mechanism.

• Refractometry—The indirect measure of the concentra-tion of dissolved components which influence the refrac-tive index of a sample of solution using a simple hand-held refractometer. It can be used to monitor the buildup of soils and concentration of a solution due to waterevaporation. Empirical observations of cleaning solu-tions in use compared with recorded measurements canbe used to derive appropriate times to recharge or dis-card solutions.

• Foam Height—Observation of the foam height of a vol-ume sample of cleaning solution in a vigorously-agitated,stoppered test tube will show a decrease in foam heightand foam stability with the build up of oils. As foamheight decreases, cleaning solution should be rechargedor discarded. Observations must be made at the sametemperatures.

• pH—Measurement of the acidity or alkalinity of a solu-tion on a scale of 0–14, expressed as the negative log ofthe hydrogen ion concentration, which is measuredusing electrodes dipped in the solution connected to apH meter. Note that pH paper should not be used withsurfactant-containing cleaners, because they commonlyinterfere with accurate readings. A given brand of deter-gent will have a typical pH. If the soils are acidic, inor-ganic, or saponifiable natural oils, the pH will drop asthe cleaning solution is used up. Typically, as pH drops0.5 pH units, the detergent should be recharged. Thenthe solution can be used to exhaustion as it drops onefull pH unit.

Each of the above methods has its application, based onthe type of detergent used and the soils that need to beremoved. When using an ionic cleaner to remove nonionicsoils, for example, conductivity can be used to monitor dilu-tion, dragout, and loss of detergent. When using a high-emulsi-


It is important to note, however, that manufacturersalready using aqueous-cleaning solutions don’t need a closed-loop system to begin recycling today. In fact, recycling can beas simple as making up a large soak tank for continuous usethroughout the manufacturing process, saving time andmoney merely by recycling wash-tank water through a skim-mer, then recharging with detergent at midweek intervals. Thiswill allow you to avoid downtime during draining, refilling,recharging with detergent, and reheating the tank.

REFERENCESAlkaline Cleaner Recycle Handbook, Membrex, Inc., Fairfield, NJ 1994, p.

5.Precision Cleaning, June 1997, article “Closed-Loop Cleaner Recycling by

Malcolm McLaughlin, p. 17–24.Personal interview, University of Massachusetts at Lowell, Toxics Use

Reduction Institute.Alkaline Cleaner Recycle Handbook, Membrex, Inc., Fairfield, NJ 1994, p.

5.Ibid., pp. 4–5.Ibid., pp. 3–5.Closed-Loop Aqueous Cleaning, University of Massachusetts, Toxics Use

Reduction Institute, Lowell, MA, 1995, p. 6.Ibid, p. 10.Precision Cleaning, December 1997 issue, article “Wastewater

Treatment,” p. 50.Precision Cleaning, December 1997 issue, article “Filtration Systems,” p.

38.Precision Cleaning, November 1996, article “Aqueous Cleaning System

Design: Recycling, p. 36–42.Precision Cleaning, December 1997, article “Sifting Through Filtration

Options,” p. 16–23.Precision Cleaning, October 1996, article “Aqueous Cleaning Technology:

How long is a Cleaning Bath Really Effective?”, p. 21–27.

RESOURCESwww.alconox.com


ulatory compliance costs are prohibitive or no drain is avail-able, the answer is, in all probability, better to recycle.

Another factor to consider is the volume of your cleaningsystem. In high-volume, high-performance cleaning applica-tions with quality control inspection or low fault-toleranceparts such as electronic components and optical parts, recy-cling may well be worth it. But in low-volume, extreme-clean-ing performance applications such as pharmaceutical processequipment, medical devices and high-priced, soil-sensitiveequipment, recycling the detergent may not be.

Also, before considering recycling as an option, an evalua-tion and determination must be undertaken as to whether theEPA needs to be involved, including the completion of a SARAreport of discharge quantities of any listed chemical that iseither in the soil or detergent discharge.

The following additional parameters must also be fullyreviewed:

• Toxicity—by TCLP (Toxicity Characteristic LeachingProcedure)

• Corrosivity—pH below 2 or higher than 12.5

• Ignitability—flash point below 60˚C (140˚F) ignitable

In addition, compressed gases and oxidizers as well asreactivity of the waste stream should be reviewed to determineif RCRA regulations apply as covered in 40 CFR 261.21-.24, aswell as any applicable state and local discharge regulations.

PROVEN TECHNOLOGIESThere are numerous suppliers of closed-loop aqueous-cleaningsystems designed to increase process efficiency by decreasingthe generation of waste. Implementing such systems shouldnot be based solely on short-term economic evaluation, butmust also include a careful review of environmental and regu-latory considerations. The benefits of sophisticated closed-loop systems must be weighed against the costs of maintainingthose systems (for example, membrane systems need periodiccleaning or may need to be replaced).

In the long run, recycling may be more economically bene-ficial than constantly playing catch-up with the evolving regu-lations surrounding industrial parts cleaning.


CHAPTER 10

Measuring Cleanliness Measuring cleanliness can be done at different levels depend-ing on the technique employed. Processes which detect clean-liness at levels as low as 0.01 grams per square centimeter in-clude:

• Visual inspection

• Low power microscope inspection

• Wiping and visual inspecting

• Water break tests

• Atomizer tests

• Nonvolatile residue inspection

• Surface UV Fluorescence detection

• Tape test.

The next level of cleanliness measurements detects soils atthe 0.01 to .001 gram per sq. cm level—a level of detection issuitable for aerospace, electrical, automotive and many sur-face preparation applications. This level of detection can beachieved through Millipore filter measurement techniques

• Optical microscopy

• Extraction

• Oil evaporation

• Oil soluble fluorescence

• Gravimetric analysis

• Surface Energy tests

• Contact angle measurement

• Particle counting

Measuring Cleanliness 141140 The Aqueous Cleaning Handbook

prints. It will not readily detect non-hydrophobicresidues. This test is often used for parts washing; it maynot always be suitable for precision cleaning applica-tions.

• Atomizer test—A variation of the water-break test, thisrequires observing whether a gently sprayed water mistdeposits uniformly or whether water repulsion occurs(usually due to a hydrophobic soil). The atomizer test isslightly more sensitive to hydrophobic soils than thewater break test. In the water break test the kinetic ener-gy of the flowing water may overcome a hydrophobicresidue where in the atomizer test you may be able tosee the results of a little droplet of water being repelledby a hydrophobic contaminant.

• Nonvolatile Residue Inspection (NVR)—The NVR testinvolves extraction of soil from a dirty surface into a sol-vent, just as is done with the extraction method above.The solvent is then evaporated onto a coupon of knownweight and after the solvent is evaporated off any residueis deposited on the coupon. When the coupon is re-weighed, any increase in weight is recorded as the non-volatile residue. Many solvents can be used for this pur-pose. It is important to use a solvent that can dissolvethe soil being detected. (Isopropyl alcohol, methalynechloride, acetone and other solvents have been used forthis purpose.)

• Surface Ultraviolet Florescence (UV)—Many organicand some inorganic contaminants will fluoresce underUV light. Shining a UV light on the surface will cause theresidues to easily be seen, particularly in a slightly dark-ened or dark room. The higher the intensity of the lightused, the lower the level of contaminants which can beeasily detected. Note, however, that the typical blacklight found in novelty or specialty gift stores may not bestrong enough to cause much residue to fluoresce. Morepowerful UV lights available from scientific supply hous-es or industrial suppliers will give far higher levels ofdetection. The test is performed by shining the light onthe surface and observing a fluorescent, typically a yel-low, orange or green, sometimes red, color which glows

Measuring Cleanliness 143

The highest level of cleanliness measurement—where lev-els below 1 microgram per sq. cm. can be detected—are suit-able for use in semiconductor, disk drive, and medical deviceapplications. The kinds of techniques that are used for thislevel of precise cleanliness measurement are:

• Carbon coulometry

• Electron spectroscopy for chemical analysis (ESCA)

• Fourier transform infrared (FTIR)

• Gas chromatography/mass spectrophotometry (GC/MS)

• Ion chromatography (IC)

• Optically stimulated electronic emissions (OSEE)

• Particle counting, scanning electron microscopy (SEM)

• Secondary ion mass spectroscopy (SIMS)

The following are summaries of these various cleanlinessmeasuring techniques as appropriate to each of the three lev-els of cleanliness required.

CLEANLINESS DETECTION AT 0.01 GRAMS PER SQ. CM• Visual inspection—is best used to detect residues of

contrasting color or texture. Good lighting can enhancevisual inspection, fiber optic lights providing light acrossa surface improve detection, and magnification of courseimproves detection.

• Low-power microscope inspection—This is an excel-lent way to quickly and efficiently verify cleanliness ofresidual oils and greases, flux residues, particles and sur-faces.

• Wiping and visual inspecting—Wiping a surface with awhite wipe will provide a contrasting surface with whichto detect dark residues (the white glove test).

• Water-break test—Use running water and let it sheetacross the surface. Observe if any breaks in the wateroccur due to hydrophobic (water-fearing) residues. (See“The Hydrophobic Surface Film by the Water BreakTest,” ASTM Method F 22-65—found at www.astm.org.)The water break test is a fairly crude test which is suit-able for detecting films of process oils and heavy finger-


analysis for detergent residues it is advisable to usewater as the solvent. (The sensitivity of an extraction testdepends on the method of trace analysis.)

The types of trace analyses most often used are UVvisible spectrophotometry, total organic carbon (TOC)analysis, high performance liquid chromatography(HPLC), atomic absorption (AA) or inorganic residues,and liquid chromatography (LC). (These techniques arediscussed separately in this chapter under “Detectionbelow 1 microgram per sq. cm.”)

• Oil Evaporation—For filmy residues, a few drops oforganic solvent can be deposited on the surface and thenremoved via pipette and placed on a watch glass. If anyfilmy residues are present, one should observe a charac-teristic ring of organic-material deposits.

• Oil Soluble Fluorescence—Involves immersing a partin a fluorescent oil soluble penetrant dye and thenobserving under fluorescent light to see if any dye pene-trates or adheres indicating the presence of oil. Thismethod is outlined in ASTM F601-98 “Standard Practicefor Fluorescent Penetrant Inspection of Metallic SurgicalImplants.” Of course cleaning procedures need to beestablished to remove the dye after testing.

• Gravimetric Analysis—With small parts of knownweight, the amount of excess weight indicated theamount of soil present.

After cleaning if the part returns to it’s clean weightone can conclude that the part is clean. Gravimetricanalysis is also very useful as a screening tool in labcleaning situations where a coupon is weighed beforesoiling, after soiling with an artificial soil, and thenweighed again after cleaning to derive percent of soilremoved.

• Surface energy—Any hard, flat material has a character-istic surface energy. As a result, a deposit of a known vol-ume of pure liquid (typically deionized water) will forma droplet of predictable size based on the amount of thatenergy. Measuring droplet size will determine surfacecleanliness. Generally, hydrophobic soils create smaller


under the light and is easily seen.

• Tape Test—The Tape Test is a simple method for aidingvisual inspection and is well suited to determining thecleanliness of smooth metal and plastic parts. It involvesattaching transparent adhesive tape to the surface beingmeasured, firmly pressing it down, carefully removing itand then placing it on a sheet of clean white paper.Comparing the sample with an adjacent piece of whitepaper provides a fast, easy way to visually monitor par-ticulates and sometimes even film residues.

CLEANLINESS DETECTION AT 0.01 TO .001 GRAMS PER SQ. CM

• Millipore Filter Measurement—The Millipore Test—also known as the “patch” test—involves spraying sam-ples of parts with filtered hexane, isopropyl alcohol, ortrichlorethylene at pressures of 60 to 80 psi through a1.2-micron filter membrane inside a jet nozzle. Thespray is collected, vacuum-filtered onto a clean filtermembrane followed by microscope inspection for anyparticle-per-micron contaminants. (The membrane canalso be weighed to determine total contaminants in mil-ligrams.)

• Optical Microscopy—High-power compound micro-scopes can also be used (typically on circuit boards),however, these are more delicate and more expensivethan simple, low-power microscopes and generallyrequire greater operator skill and training.

• Extraction—a particularly useful method for detectingdetergent residues, this measurement technique employsa solvent-soaked glass filter paper, or high purity swabsto wipe surfaces. The filter paper or swab is then extract-ed or digested and trace analysis performed on theextract. This procedure can be quantitative if one wipesa known area.

Extraction methods can be highly sensitive to a widerange of possible soils and residues. The limitations onthis method, however, is that an appropriate solventmust be used to extract any soils. When performing trace


now employ ultrasonic cleaning baths as well.In-situ particle monitoring (ISPM) provides a tool to

observe particle removal behavior in the ultrasonic cleaningbath process at work and in real time, thus providing the abili-ty to quickly select, adjust, and optimize the cleaning process.Once the process is optimized, ISPM can be used to monitorbath performance, and monitor filtration recycle performance.ISPM measures particle counts directly during the cleaningprocess in both ultrasonic rinse and wash baths.

AN EXAMPLE OF HOW IN SITU PARTICLE MONITORING WORKSIn work done by John Hunt (Pacific Scientific Instruments,Grants Pass, OR) to optimize a choice or concentration ofcleaning agent, a known amount/type of particle contamina-tion was deposited on glass slide test coupons. Several clean-ing agents were tested for their effectiveness in removing thecontamination by monitoring the rate of particle removal inthe bath by recycling the bath through a filtration loop anddetecting particles just before filtration.. For each concentra-tion and each detergent, various particle sizes were observedin the bath at the addition of increased concentration of deter-gent, and then again when the soiled glass plate is added tothe bath. When the soiled plate is added, a number of parti-cles per ml per minute is determined by integrating the areaunder the particle size counting curves for a given length oftime for each particle size monitored at each concentration ofeach detergent. If you are trying to optimize detergent con-centrations, be sure to allow any bubble interference to reachbaseline after addition of increased concentration of detergentprior to placing the soiled plate in the bath. By observing theshape of the particle counting curve, you will typically see aninitial spike of particles coming off the plate when you add thesoiled plate and then see particles continue to come off overtime. Typically after 10 or 15 minutes no more particles areobserved. This information can be used to optimize cleaningtimes in addition to cleaner concentrations. By the sametoken, during cleaning, real-time particle counting could beused to determine when to take the parts out of the bath byobserving when the particle counts had dropped back to base-line.


droplets; hydrophilic soils, larger ones. The surface-ener-gy test is far more sensitive than the atomizer or water-break test and has the advantage of being able to detectboth hydrophilic and hydrophobic soils. The problemwith the surface energy test is it only tests the surfacedirectly underneath the droplet where you are measur-ing. If you have a broad, large surface where measuringone little area of it would be representative of the level ofthe cleaning that went on the entire surface, this can bean excellent and highly sensitive method. If you have apart that has lots of cracks and crevices and holes, thesurfaces that are accessible for you to place a droplet ofliquid to measure surface energy may not be representa-tive of the types of soils that may be hidden in anycracks, crevices, or blind holes. (For a fuller descriptionof this measurement technique see “More on water-dropsurface energy test,” which follows this section.)

• Contact angle measurement—A variation of surfaceenergy testing is contact-angle, defined simply as therelationship of certain forces when a liquid stabilizes ona part’s surface. This method can be used to determinecleanliness since the properties of various contaminatedsurfaces are reflected by different contact angles.Contact-angle measurement is especially suited to manu-facturing operations such as wire bonding on PCBs orthe application of thin films on quartz glass whichrequire a cleanliness test that is nondestructive. Vaporsfrom the process itself, such as vacuum or diffusionpump oils, various process chemicals, or even humanperspiration, are all contaminants whose presence canbe detected by changes in the contact angle. (For a fullerdescription of this measurement technique see “More onContact Angle Measurement Methods,” which followsthis section.)

• In-situ Particle Counting (ISPM)—Part cleanlinessbecomes critically important as mechanical, optical, andelectronic parts shrink in size and formerly inconsequen-tial particles grow in comparison. High-technologycleaning techniques, such as ultrasonic bath cleaning arewidely used. Today’s precision industrial applications


droplet and its measurement.

• Use medical-grade, ultra-purified deionized water from alaboratory supply house in order to have a consistentmeasuring liquid. This will limit the number of measure-ment variables.

• Use test liquids of larger surface tension than the solid’ssurface energy in order to obtain easy-to-read results.

• Neutralize the effects of static charges on substrates.Substrates that are electrostatically charged can skewcontact angle readings up to 5 degrees.

• Accurately control liquid droplets so that they are repeat-edly deposited onto the sample. Gently move the sampleto the liquid droplet formed at the end of the syringe/dis-penser in order to minimize gravitational effects.

• In the case of very high contact angles, you may find itdifficult to adhere the droplet from the needle to thesolid sample. Use a Teflon-coated needle of a highergauge (smaller inner diameter).

• In case of very low contact angles, use the highest possi-ble needle gauge (smallest inner diameter needle) forcontrolling very small droplet volumes onto the sample.

MORE ON CONTACT-ANGLE MEASURING METHODSAccepted methods of measuring contact angles to determinesurface characteristics include the inverted bubble, WilhelmyPlate, and sessile drop techniques. The latter is the most wide-ly practiced quality control technique, as it is relatively quickand requires minimal investment in time and financialresources.

In the sessile drop technique, the specimen to be measuredis loaded onto a specimen holder. A liquid droplet 3 to 4 mmin diameter is carefully deposited onto the substrate surface. Atangent line is drawn at the three-phase interface point inorder to determine the contact angle. Alternately, a line isdrawn from the three-phase interface point through the apex.This angle turns out to be equal to 1/2 of the tangent angle andis reproducible by different operators.

Several “real world” examples will help illustrate what canbe learned from the use of the contact angle measuring tech-


MORE ON WATER DROP SURFACE ENERGY TEST Surface energy can be indirectly detected by measuring thesize of a droplet of known volume sitting on a surface. Using avolumetric pipette a drop of typically 0.2 ml of water is placedcarefully onto a surface being investigated. The droplet size ismeasured with a micrometer. If the droplet is circular the areais determined by the pi r squared method. Note that anymachining or scoring will distort droplets, it may be easier touse a length times width method of estimating droplets – donot vary area calculations within a set of measurements.Typically a surface with a hydrophobic oily residue film willrepel the water and cause the droplets to be smaller than areobserved on the clean surface.

This method works well on glass and metal surfaces. It isbetter at detecting films on smooth surfaces rather than par-ticulates. If the surface is scratched during cleaning, thedroplet size will become smaller causing false readings if thetest is used as a before and after test. If a volumentric pipetteis not available, then using an eyedropper to deposit drops andusing a scale sensitive to 0.001 grams, the ratio of dropletweight to area can be used to detect changes in surface energy.Again, a rise in this ratio indicated going from a dirty to aclean surface. It is useful to work with some known cleanedsurface to observe droplet size behavior and known soiled sur-faces to confirm that the residue will give the observedchanges.

As with other cleanliness verification techniques, specialtips for contact angle measurement, if practiced, will increasethe repeatability and validity of the measurement results. Thefollowing tips from Precision Cleaning magazine, (Oct. 97 p.23) were helpfully compiled:

• Use gloves when handling the samples to be measured.Organics, such as finger oils, cosmetics, and other conta-minants, will skew the contact angle results.

• Note the nature of the droplet after applying it to the sur-face. Wait until the droplet has ceased its advancementand no more change in lateral movement has occurred.Measure this time interval, making sure that you waitthis period of time after every measurement. Retain con-sistent time intervals between the placement of the


• Fourier Transform Infrared Spectroscopy (FTIR)—FTIR spectroscopy is used for structural characterizationof organic and inorganic molecules in solids, liquids,gases, and on surfaces. Spectrometers record the interac-tion of light energy in the form of infrared radiation withan experimental sample, measuring the frequencies atwhich the sample absorbs the radiation and the intensi-ties of the absorption. After using an extraction methodor by using a surface scanning machine, by comparingthe unknown spectra to the standard frequency at whichspecific molecules are known to absorb light, the sam-ple’s chemical makeup as well as it’s concentration canbe determined.

• Gas Chromatography/Mass Spectrophotometry(GC/MS)—GC/MS is used to identify surface contamina-tion by extracting contaminants into a solvent and ana-lyzing them. Organic compounds are then separated viaGC and are then identified, based on molecular weight,by MS.

• Ion Chromatography (IC)—Ion Chromotography is aform of liquid chromatography of aqueous samples usedto determine ionic contamination on critical compo-nents. Columns containing ion- exchange resins areused to separate the atomic or molecular sample ionsbased on their partition ratios as they pass through thecolumns. It is the only technique that can provide quan-titative analysis of anions at the ppb level of an extractthat has been swabbed or wiped from a surface andextracted into solution for analysis.

• Optically Stimulated Electronic Emissions—Whenhigh-energy UV light hits a surface, electrons are emit-ted, and the reflected current can be measured. A cleansurface will give the highest return current, so any dropin current represents contamination. This method isgood for determining low levels of contamination (bothionic and nonionic). However, while optically stimulatedelectronic emissions can detect contamination, it cannotidentify it.


nique to determine the existence of impurities on a surface.LCD (Liquid Crystal Display) panel surfaces contaminated

with organic matter will be less accepting of a variety of films,such as metals and protective layers, resulting in poor manu-facturing yields. Sources of such contaminants include thevapor of process materials, chemicals, and human perspira-tion. Very thin organic contaminants several monolayers inthickness (greater than 10 angstroms) can be evaluated usingthe contact angle technique.

In fact, it is generally agreed that the wetting behaviorinvolves only the last layer or two atoms on either side of asolid’s interface. The water contact angle correlates the “clean-liness” of the surface to the adhesion of the copper depositedonto the surface of the LCD.

Water contact angles can be used in various processes todetermine contamination levels, predict cleanliness and adhe-sive bond strengths, and monitor cleaning operations.Whether you are checking the moisture effects on siliconwafers or LCD quartz panel glass metal adhesion, all that isneeded is an understanding of the basic theory involved andproper measurement techniques.

DETECTION BELOW 1 MICROGRAM PER SQ. CM • Carbon Coulometry—The technique employs in-situ

direct oxidation of surface carbon to carbon dioxide(CO2), followed by automatic CO2 coulometric detec-tion. (For a fuller description of additional in-situ moni-toring techniques, see the “In-Situ ParticulateMonitoring” section of this chapter.)

• Electron Spectroscopy for Chemical Analysis(ESCA)—ESCA is an extremely surface-sensitive tech-nique, which employs the photoelectric effect, for thedetection of elements and determination of elementalcomposition. Electrons are ejected from a solid surfaceby irradiating the surface with an x-ray monobeam. Theemitted photoelectrons have a kinetic energy equal tothe x-ray less the binding energy of the electron. Themeasured kinetic energy of the electrons can thereforebe converted to binding energies, enabling element iden-tification.


• Scanning Electron Microscopy (SEM)—By scanninghigh energy electrons across a specimen, SEM allows thestudy of both morphology and composition of biologicaland physical materials. When high energy primary elec-trons impact the specimen they are deflected or scat-tered. Those that are deflected at an angle greater than90o can reenter the vacuum above the specimen andmake up the backscatter signal. The proportion of pri-mary electrons collected as backscatter electrons (bse)increases as a function of the atomic number of the sam-ple specimen, thereby portraying its chemistry. Forwardscattering primary electrons, those that are deflected atan angle of 90o or less, travel through the specimenwhile loosing energy. The atomic electrons gain this lostenergy, allowing them to escape from their atoms. Thosethat are very close to the surface (within the escapedepth) may have sufficient energy to escape from thesample surface back into the vacuum as secondary elec-trons (SE). Because an incline surface exposes a largerarea to the electron beam, thereby impacting more elec-trons within the escape depth, production of secondaryelectrons is attributable to the specimen being at highincident angles with the electron probe. The resultant seimage thus reflects the surface topography of the speci-men.

• Secondary Ion Mass Spectroscopy (SIMS)—SIMS isan extremely sensitive surface analytical technique usedfor chemical determination of surface constituents, bothelemental and molecular, as well as ppb concentrationsof impurities in semiconductors and metals. The materi-al under investigation is bombarded with primary ionswhich, upon impact, cause secondary ions to be ejectedfrom the sample’s surface. These secondary ions can beidentified by their mass, which is determined by measur-ing their travel time from surface to analyzer.


REFERENCESAlconox Cleaning Solutions newsletter, Vol. 1, Number 1 article “How

Clean is Clean?”ASTM. F-2265, The American Society of Testing Materials.Carol LeBlanc; Turi, Massachusetts, Toxics Use Reduction Program for

The 22nd Mr. Clean Conference, Oct. 96.Carrasco, Armando, “Moisture Induced Stress Sensitivity Reduction of

FSRAM 52 Lead PLCC’s,” 1996 Surface Mount InternationalConference, p. 607–611.

Cleaning Printed Wiring Assemblies in Today’s Environment, p. 94“Testing for cleanliness,” and p. 197 “Cleanliness Verification”

Cleantech “Cleanliness Verification,” CleanTech Vol 3, No. 3, S1-S12(March 2001)

Djennas, Frank, Prack, Edward, and Matsuda, Yushi, , “Investigation ofPlasma Effects on Plastic Packages Delamination and Cracking.”IEEE Trans. CHMT, 16. 1993, p. 91–924, edited by Les Hymes.

G. Gould and E.A. Irene, “An Inside Study of Aqueous HF Treatment ofSilicon by Contact Angle Measurement and Ellipsometry,” Journal ofThe Electrochemical Society, 135 (1988), p. 1535–39.

Geosling, C and Koran, J “Contamination Control and AnalyticalTechniques,” in Ch 3.2 Handbook for Critical Cleaning, Kanegsberg, B.Ed., CRC Press Publishers, Boca Raton, 2001, 431-448

Good, R.J. and Stromberg. R.R., Ed., “Colloid and Surface Science,”Plenum, Volume 11, New York, 1979.

Hawkins, George, Ganesan. Gans, Lewis, Gary and Berg, Howard. “ThePBGA: A Systematic Study of Moisture Resistance,” The ISHMJournal of Microcircuits & Electronic Packaging, 18, No. 2, 122–132,1995.

Herard, Laurent, “Surface Treatment for Plastic Ball Grid ArrayAssembly and Its Effect on Package Reliability,” ISHM Workshop onFlip Chip and Ball Grid Arrays, Berlin, Germany, November 13–15,1995, p. 1.

Japan, Kuman- Gypta, “Comparative Studies of the Contact Angle as aMeasure of Adherence for Photoresist,” Thin Solid Films, 75 (1981), p.319–329.

Mittal, K.L., Ed., “Contact Angle, Wettability and Adhesion,” VSP,Volume 1, the Netherlands. 1993.

Precision Cleaning, October 1997 article “Contact Angles MeasureComponent Cleanliness,” p. 21–24.

Toshiaki Matsunaga, J., “Relationship Between Surface Energy andSurface Contamination,” Physical Chemistry, 71 (1967), p. 4176.

Trent Thompson, “Moisture Absorption and Autoclave PerformanceOptimization of Glob Top Ball Grid Array,” 1996 Surface MountInternational Conference, p. 587–592.

Williams, Richard and Goodman, Alvin M., “Wetting of Thin Layers ofSiO2 by Water,” Applied Physics Letters, Volume 25, November 1974,p. 531–532.


Environmental Health and Safety Considerations 155

CHAPTER 11

Environmental Health and SafetyConsiderations The key environmental health and safety advantages and dis-advantages of aqueous cleaners both derive from the fact thatthey use water for cleaning and rinsing. Water is inherentlyenvironmentally sound and a substantially safe chemical towork with. Water is a recyclable natural resource. Yet, as pop-ulations grow, clean surface water will become increasinglyscarce. Water can also be a transport medium for various pol-luting or hazardous chemicals that may derive from the use ofaqueous cleaning in specific instances.

One way to look at the environmental health and safety ofa cleaning process is to consider:

• How hazardous is the cleaning process?

• How hazardous is the effluent resulting from the clean-ing process?

• How sustainable—in terms of energy and resources—isthe process?

All critical cleaning is a spectrum that ranges from pollut-ing hazardous processes to clean and safe processes; clean,safe, and reduced waste processes; and clean, safe, and sus-tainable processes. Aqueous cleaning can, in fact, play a roleall along this spectrum.

It is, of course, possible to use aqueous cleaners with haz-ardous ingredients that are used to clean hazardous soils that

RESOURCESwww.alconox.comwww.astp.comwww.photoemission.comwww.pmeasuring.com


Environmental Health and Safety Considerations 157156 The Aqueous Cleaning Handbook

these cycles are relevant to aqueous-cleaning ingredients.However, all of these cycles involve far more chemical trans-formations and slower processes with longer residence timesin various long-term forms. For example, one step in the car-bon cycle involves extensive time spent as geological carbon-ates—in the same way nitrogen stays for extensive periods asnitrogen in the air. Oxygen is also tied as geological carbon-ates. These elements simply do not cycle as rapidly, in a puri-fying sense, as does water.

ENVIRONMENTAL ISSUES IN AQUEOUS CLEANINGThe environmental issues involved in aqueous cleaning aremostly associated with the ingredients and their ultimate dis-charge into the environment. Taking a larger view of the envi-ronmental issues concerning aqueous-cleaning processes it isreasonable to consider the energy and resources used in mak-ing the cleaner, and the energy and resources consumed inusing the cleaner.

There are several important factors concerning dischargeof spent cleaning solutions into the environment: biodegrad-ability, aquatic toxicity, and eutrophication potential.Historically, early detergent formulations contained poorlybiodegradable surfactants that were capable of causing foam-ing in surface lakes and rivers when the spent solutions weredischarged to drain. Today, all modern detergent formulationsuse biodegradable surfactants that do no buildup and persistin the environment and cause surface water-foaming prob-lems.

Aquatic toxicity can come from very high or very low pHor the toxicity of the ingredients. Where extreme pH cleaningis required, it is advisable to neutralize or discharge spentsolutions in small enough quantities to avoid problems. Thesur-factants in aqueous cleaners can have aquatic toxicityassociated with them. The use of biodegradable surfactantsand the discharge of limited quantities of cleaning solutionsgenerally results in no toxic concentration of surfactants insurface water. Older more highly toxic surfactants are nolonger widely used in aqueous-cleaner formulations.

Eutrophication involves cleaners that contain phosphates.Phosphorus is an essential nutrient for algae. When significant

are then dumped in the environment—resulting in a haz-ardous, polluting process. But by the same token, industrialcleaning can also involve the use of an aqueous cleaner thathas no hazardous ingredients used to clean the same haz-ardous soils whereby the cleaning solutions are treated priorto discharge—resulting in a clean and relatively safer process.

Improvement in safety can be achieved by eliminating thesource of the hazardous soil in the process. Taking this a stepfurther one can effect a reduced waste process by incorporat-ing some degree of soil recycling, cleaning solution recycling,and rinse water recycling. It is possible to design a so-called“zero-discharge” system with no fluid effluent, limited volatileeffluent and reduced solid waste by recycling cleaning andrinsing solutions with filters. In order to move toward a clean,safe and sustainable process, however, one would need toeliminate the use of whatever caused the hazardous soil andreplace it with a nonhazardous biodegradable soil. Then, afterthe water used in the cleaning and rinsing process has beenrecycled sufficiently to create sustainable energy consumptionrates, the now nonhazardous soil in the effluent would not cre-ate a hazard in the environment. Any water released couldsafely be incorporated into the natural water cycle (surfacewater to evaporated water to clouds to rain, and finally, onceagain returning to surface water).

Most nonaqueous chemical cleaning methods generallyhave much greater difficulty in achieving clean, safe, sustain-able processes. Many nonaqueous cleaners are themselveshealth hazards, water pollutants, or air pollutants. Certainlynot all nonaqueous cleaners are hazardous and/or pollutants,but most do not have a basic natural process such as thewater-cycle to purify and recycle key ingredients. (Of course,this is an oversimplification; viewed from the standpoint of along enough time scale, almost anything can be considered tohave a sustainable natural cycle of synthesis and decay. We areconsidering here natural processes that can contribute to sus-tainable processes achievable in the course of human life-times.)

One might argue that the carbon cycle, the nitrogen cycle,the oxygen cycle and many other elemental cycles also becomeinvolved in nonaqueous cleaning processes. In fact, many of

Environmental Health and Safety Considerations 159158 The Aqueous Cleaning Handbook

cleaners may contain volatile solvents that require special ven-tilation and possibly even flammability controls.

While it is relatively unusual for an aqueous cleaner tocontain any carcinogenic ingredients, a review of the cleaner’smaterial safety data sheet should disclose any long-termchronic exposure concerns relating to carcinogenicity.

Physical safety issues with aqueous cleaners are generallyconcern storage and handling to avoid any hazardous reac-tions with other industrial chemicals. Good industrial practiceusually involves storing acid and alkaline chemicals separatelyto avoid any reactions between them and aqueous cleaners inthe event of accidental spills. Some aqueous cleaners containbleaches or other oxidizing agents that should be stored awayfrom reactive chemicals that might undergo hazardous oxida-tion reactions. As previously mentioned, most completelyaqueous cleaners are usually not flammable. However, someaqueous cleaners can contain ingredients that can create haz-ardous chemicals when burned. (It is considered good practiceto wear respiratory protection when fighting any fire involvingindustrial chemicals.)

PRACTICAL REGULATORY REVIEWIn today’s manufacturing environments, it is realistic to try toachieve safe, clean, and reduced waste cleaning processes—and to continually strive toward achieving ultimately sustain-able processes. At the very least, processes that comply withcurrent environmental and health safety regulations should beused.

The first step in evaluating the environmental health andsafety of an aqueous cleaner is to secure the material safetydata sheet and technical bulletins for the cleaners you plan totest or use, and to assemble as much information as you canabout the soils you will be removing. A review of this informa-tion should disclose important environmental and health haz-ards and regulatory issues.

When performing an initial review of regulatory issues foran aqueous cleaner, it is important to consider OSHA(Occupational Safety and Health Administration) regulations,NPDES (National Pollutant Discharge Elimination System)discharge permits, DEP (Department of Environmental

amounts of phosphorus are discharged into surface water, itcan result in vigorously growing algae blooms. The algae dieand settle to the bottom of the water causing more rapid thannormal filling in of lakes and ponds with silt and organic mat-ter. Although eutrophication is a normal, natural process, theacceleration of this process by phosphates is undesirable. Themain source of phosphorous to surface waters is agriculturalrun-off from farming. There are no national regulationsrestricting the use of phosphates in cleaners, however manystates and municipalities have enacted legislation that restrictsthe use of phosphates in household cleaners. There are cur-rently no restrictions on the use of phosphate containingcleaners in industrial cleaning applications.

SAFETY ISSUES IN AQUEOUS CLEANINGWorker safety issues with aqueous cleaners can involve skinexposure, eye exposure, ingestion, inhalation, and chronic sys-temic exposure. Consult the label and material safety datasheet on the cleaner for warnings and safety precautions.

When cleaning by hand, it is always good practice to wearprotective gloves. Even the mildest cleaners can sometimescause “dishpan-hand” skin irritation. Gloves also afford adegree of comfort when working manually with hot solutions.In fact, many highly acidic or alkaline cleaners require the useof chemical-resistant gloves for worker safety.

Eye exposure is also a concern with many aqueous clean-ers. Eye tissue is particularly prone to attack by chemicallyactive aqueous solutions. Accordingly, it is also consideredgood industrial practice to wear safety glasses or other eyeprotection when working with aqueous-cleaning solutions.Particularly hazardous aqueous cleaners should have warn-ings and recommended eye protection on the label.

In addition, inhalation hazards can exist with some aque-ous cleaners. Because aqueous cleaners generally do not havevolatile solvent ingredients, it is somewhat unusual to find theneed for respiratory protection with such cleaners. However, itis considered good industrial practice to have some respirato-ry protection when working with sprays and mists in open-spray cleaning. Any special ventilation required should benoted on the material safety data sheet. Some semiaqueous

Appendix 161160 The Aqueous Cleaning Handbook

AppendixI List of Abbreviations

II Cleaner Types from Alconox, Inc.

III Detergent Selection Guide

IV Glossary of Essential Terms

V Application Case Histories

VI Index

Protection) sewer connection/extension permits, and anyRCRA (Resource Conservation and Reclamation Act) haz-ardous waste class or Clean Water Act regulations. State andlocal environmental regulations should also be considered.

In the long run, it may be wise to conduct a full scale envi-ronmental audit no matter what type of cleaning system youare using. Such an audit may result in changes in the way youcurrently manufacture and clean. In fact, after conducting afull-scale environmental audit many companies turn to aque-ous cleaning as a means to more easily and safely achieve reg-ulatory compliance. (A program of regular re-auditing canassure continued regulatory compliance.)

When compared with many of the hazards of nonaqueousand semiaqueous cleaners—such as those containing ozone-depleting fluorocarbon solvents, carcinogenic organic sol-vents, and flammable components—aqueous cleaners are asound choice for safe, environmentally sound cleaning. Bychoosing the safest, most environmentally sound aqueouscleaner that will perform to your cleaning requirements, themajority of cleaning problems can be solved with more thanacceptable levels of worker safety and environmental impact.

ADDITIONAL READINGPrecision Cleaning, December 1995, article “Environmental Auditing:

Learning from Common Pitfalls and Issues”, p. 13–18.Journal of Surfactants and Detergents, Vol. 1, No. 1, January 1998, article

“Surfactants and the Environment,” by Larry N. Britton.

RESOURCESwww.alconox.comwww.epa.govwww.osha.gov


APPENDIX II

CLEANER TYPES FROM ALCONOX, INC.30 Glenn St., White Plains, NY 10603, ph 877-877-2526, email [email protected], www.alconox.com

Cleaner Type Cleaning Methods Used BrandHigh emulsifying, manual, soak, ALCONOX® powdermild alkaline ultrasonic, circulate CIP LIQUI-NOX® liquidAcid cleaner manual, soak, ultrasonic, CITRANOX® liquid

circulate CIPLow-foaming, alkaline machine washer, pressure ALCOJET® powder

spray, spray CIPLow-foaming, machine washer, DET-O-JET® liquidhigh alkaline pressure spray, spray CIPIon-free, low-foaming machine washer, DETERGENT 8® liquid

pressure spray, spray CIP, manual, soak, ultrasonic, circulate CIP

Mild alkaline tablet siphon tube and pipete washer ALCOTABS® tabletNeutral, low-foaming machine washer, LUMINOX® liquid

pressure spray, spray CIP, manual, soak, ultrasonic, circulate CIP

Enzyme cleaner manual, soak, TERG-A-ZYME® powderultrasonic, circulate CIP

Low-foaming, acidic machine washer, pressure CITRAJET® liquidspray, spray

APPENDIX I

LIST OF ABBREVIATIONSBOD Biological Oxygen DemandCFC Choloro Fluoro CarbonCIP Clean in PlaceCOD Chemical Oxygen DemandDEP Department of Environmental ProtectionEH&S Environmental Health & SafetyEPA Environmental Protection AgencyFT-IR Fourrier Transform Infra RedGWP Global Warming PotentialLAS Linear Alkylbenzene SulfonateLCD Liquid Crystal DisplayMSDS Material Safety Data SheetNPDES National Pollution Discharge Elimination SystemsODP Ozone Depleting PotentialODS Ozone Depleting SubstanceOSHA Occupational Safety and Health AdministrationRCRA Resource Conversation and Reclamation ActSARA Superfund Authorization and Reauthorization ActSNAP Significant New Alternatives PolicyTCVLP Toxic Chemical Leaching PropertiesUV Ultra VioletVOC Volatile Organic Compound


APPENDIX IV

Glossary of Essential Terms483—the warning letter threaten close from FDA.Acid cleaner—an aqueous cleaner that has a pH significantly below

7, typically below a pH of 5.5. Acid cleaners contain acids and oftenother cleaning ingredients such as surfactants. Acid cleaners areable to clean using the cleaning mechanism of acid solubalization(see other definitions) where an acid reacts with a soil molecule tocreate a water soluble molecule, and acid hydrolysis (see other defi-nitions) where an acid reacts with a soil molecule and breaks it intoa smaller water soluble soil.

Alkaline cleaner—a water based cleaner that contains alkalineingredients that cause the cleaner to have a significantly high pH. Acleaner with a pH of 8.5–11 can be considered to be a mild alkalinecleaner. A cleaner with a pH of 11–12.5 is at least an unqualifiedalkaline cleaner. A cleaner with a pH above 12.5 would be a highalkaline and corrosive cleaner. Alkalinity helps promote saponify-ing(see other definitions), solubilizing (see other definitions) alka-line soluble soils, and hydrolysis (see other definitions).

Anionic surfactant—a cleaner ingredient that is a surface activeagent(see other definitions) that has a negative charge on theorganic portion of the molecule. The charge on the surfactantdetermines the charge of the cleaner or detergent. An anionic deter-gent contains anionic surfactants. Anionic surfactants can be andusually are emulsifiers (see other definitions) and dispersants(seeother definitions). Typical anionic surfactants include organic sul-fates, sulfonates and carboxylates. The most common anionic sur-factant is sodium dodecylbenzene sulfonate.

API—active pharmaceutical ingredient.Aqueous cleaner—a blend of water soluble chemicals designed to

remove soils into a water based solution with a water continuousphase during cleaning.

ARP—annual product review.Bioburden—microbes on the surface.Builder—a cleaner ingredient that enhances the cleaning ability of

the surfactants in at least one, and usually a combination of the fol-lowing ways: softens water to prevent water hardness ions fromreacting with the surfactants or soils by chelation, sequestration or

APPENDIX III

DETERGENT SELECTION GUIDE

HealthcareEffective preparation forsterilization, longer instru-ment life. Minimize cross-contamination. Reducewaste.

PharmaceuticalPassing cleaning validationfor FDA good manufactur-ing practices.

LaboratoryReproducible results, nointerfering residues,extending equipment life.Keep laboratory accredita-tion. Laboratory safety.

Metalworking and PrecisionManufacturingClean parts, avoid volatilesolvents, strong acids, and other hazardouschemicals.

EnvironmentalNo interfering residues.Phosphate free.

ElectronicsAvoid conductive residues,avoid CFCs, pass cleaningcriteria.

Food and DairyAvoid interfering residueson food-contact equip-ment.

CosmeticsAvoid cross-contamination.

OpticsAvoid optical interference.

NuclearAvoid waste interference.

Surgical, anaesthetic, and examining instrumentsand equipment. Catheters and tubes.

Difficult proteinaceous soils, blood and otherbody fluids, tissue on instruments.

Product-contact surfaces.

Inorganic residues, salts, metallics, pigments

Protein/ferment residues. R/O, U/F membranes.

Glass, metal, plastic labware, ceramics, tissueculture, porcelain, clean rooms, animal cages,bioreactors, tubing, benches, safety equipment.

Tubes, reusable pipets.Water and environmental sampling. Phosphate-sensitive labware. EPA procedures.

Radioactive equipment/contaminants.Stopcock grease.

Trace metals, metal oxides, scale.

Proteinaceous soils, bio-wastes, tissue, bloodand other body fluids, fermentation residues.

Glass, ceramic, porcelain, stainless steel, plastic,rubber. Oils, chemicals, particulates.

Aluminum, brass, copper, and other soft metalparts. Oils, chemicals, particulates.

Inorganics, metallic complexes, trace metals andoxides, scale, salts, buffing compounds.

Silicone oils, mold-release agents, buffing compounds.

Metal oxides, scale, salts. Metal brightening.

Bailers, samplers, augers, containers, tubing,teflon, glass, rubber, stainless steel.

Circuit boards, assemblies, screens, parts, conductive residues, resins, rosins, fluxes, particulates, salts.


Stainless steel, food-contact equipment.

Oxides, scale, trace metals, salts, milkstone.

Filter membranes. Proteinaceous soils.

Product contact surfaces.

Lenses, substrates, mirrors, reflectors, fibers.

Reactor cavities, pipes, tools, protective equip-ment.

Manual, Ultrasonic, SoakMachine washer, sani-sterilizerManual, Ultrasonic, SoakMachine washer, sani-sterilizer

Manual, Ultrasonic, Soak, C-I-P*Machine washer, power wash

Manual, Ultrasonic, Soak, C-I-P*Machine washer, power washManual, Ultrasonic, Soak, C-I-P*Manual, Ultrasonic, Soak, C-I-P*Machine, power spray, labware washer,washer-sterilizer, cage-washersSiphon-type washer-rinsersManual, Ultrasonic, Soak, C-I-P*Machine washer, labware washer

Manual, Ultrasonic, Soak, C-I-P*Machine washer, warewasherManual, Ultrasonic, Soak, C-I-P*Machine washer, ware washer

Manual, Ultrasonic, Soak, C-I-P*Glassware washer

Manual, Ultrasonic, Soak, C-I-P*Machine washer, power washManual, Ultrasonic, Soak, C-I-P*Parts washer, power wash

Manual, Ultrasonic, Soak, C-I-P*Parts washer, power washManual, Ultrasonic, Soak, C-I-P*Parts washer, pressure sprayManual, Ultrasonic, Soak, C-I-P*

Parts washer, pressure sprayManual, Ultrasonic, Soak, C-I-P*Machine wash, pressure spray

Manual, Ultrasonic, SoakMachine washer, power sprayboard and screen washersManual, Ultrasonic, Soak

Parts washers

Manual, Ultrasonic, Soak, C-I-P*Machine wash, pressure washersManual, Ultrasonic, Soak, C-I-P*Machine wash, pressure washersManual, Ultrasonic, Soak, C-I-P*


Parts washers, power spray


Parts washers, machine washers

Manual, Soak, Spray

ALCONOX, LIQUI-NOX

ALCOJET, LUMINOX, CITRAJET

TERG-A-ZYME

ALCOJET, LUMINOX

ALCONOX, LIQUI-NOX

ALCOJET, DET-O-JETLUMINOX, CITRAJET

CITRANOX

CITRAJET

TERG-A-ZYME

ALCONOX, LIQUI-NOX

ALCOJET, LUMINOXDET-O-JET, CITRAJET

ALCOTABS

LIQUI-NOX, CITRANOX

DETERGENT 8,, CITRAJET

ALCONOX

ALCOJET

CITRANOX

CITRAJET

TERG-A-ZYME

ALCOJET, DET-O-JET

ALCONOX, LIQUI-NOX

ALCOJET, DET-O-JET

ALCONOX, LIQUI-NOX

ALCOJET, LUMINOX

CITRANOX

ALCOJET, DET-O-JET, CITRAJET

ALCONOX

ALCOJET, DET-O-JET

CITRANOX

CITRAJET

LIQUI-NOX, DETERGENT 8

DETERGENT 8, LUMINOX



ALCONOX, LIQUI-NOX


ALCONOX, LIQUI-NOX


CITRANOX

CITRAJET

TERG-A-ZYME

ALCONOX, LIQUI-NOXCITRANOX, LUMINOX

ALCOJET, DET-O-JET,LUMINOX, CITRAJET

ALCONOX, LIQUI-NOXCITRANOX, LUMINOX

ALCOJET, DET-O-JET,LUMINOX

DETERGENT 8, LUMINOX,ALCONOX




HPLC—high performance liquid chromatography. Hydrolyze—to break a molecule apart using acid (H+) and hydroxyl

ions (OH-) from water (H2O). This occurs when a fat or oil ishydrolyzed to make soap as in saponification (see other definitions)or when an enzyme breaks down a protein.

IC—ion chromatography.ICH—International Conference on Harmonization.Ion-free cleaner—a cleaner that has no metal ion ingredients.

Typically an ion-free cleaner will contain nonionic surfactants andother ingredients that are not metallic salts. An ion-free cleanerdoes not contain sodium or other metal salts.

IQ—installation qualification.LOD—limit of detection (signal to noise S/N = 3)LOQ—limit of quantitation (signal to noise S/N = 10)Micelle—is a sub-microscopic aggregate of molecules. In the context

of cleaners these molecules are surfactants usually arranged insphere or rod shapes with the hydrophilic end of the surfactantsfacing outwards into the water solution with the hydrophobic endsof the molecules facing toward the inside of the aggregate. Micellesare able to hold hydrophobic oil molecules inside them and createstable emulsions.

Neutral cleaner—a cleaner that has a pH near 7, typically in therange of 5.5 to 8.5. These cleaners tend to rely more on emulsifyingand dissolving rather than aggressive chemical attack on soils thatare possible with acid or alkaline cleaners.

Nonionic cleaner—a cleaner that contains nonionic surfactants. Theterm does not mean an ion-free cleaner. A nonionic cleaner mayeasily contain nonionic surfactants blended with many ionicbuilders that are sodium salts or other metal ion salts. (see ion-freecleaner).

Nonionic surfactant—a cleaner ingredient that is a surface activeagent(see other definitions) that has a no charge on the organicportion of the molecule. The charge on the surfactant determinesthe charge of the cleaner or detergent. An nonionic detergent con-tains nonionic surfactants. A nonionic detergent is not necessarilyion free (see other definitions). A nonionic detergent may containmany ionic salts, just the surfactant is not ionic and does not havean electrical charge. Nonionic surfactants can be and usually areemulsifiers (see other definitions) and dispersants (see other defini-tions). Typical nonionic surfactants include organic ethoxylates.The most common anionic surfactants are alcohol ethoxylates andalkylphenol ethoxylates.

OQ—operational qualification.pH—a measure of how acidic or basic a solution is defined as the

inverse log of the hydrogen ion concentration in water. In practicalterms, pH 7 is neutral, below 7 is acidic and above 7 is basic oralkaline.

ppb—parts per billion (ug/liter, microgram/liter).ppm—parts per million (mg/liter, milligram/liter).

binding; enhances surface tension lowering of surfactants; addsalkalinity; buffers a cleaner to maintain alkalinity; emulsifies oils;disperses particulates; inhibits redeposition of soils; breaks upclumps of particles by deflocculation; saponifies soils; provides cor-rosion inhibition; and improve the handling, flowing, and storagecharacteristics of the cleaner. A typical builder is sodium polyphos-phate.

CFR—code of Federal regulations.cGMP—current good manufacturing practice.Chelating Agent—a cleaner ingredient that is an chemical with at

least 2 available sites on the molecule to bind with metal ions in awater based solution to form a ring compound with metal. Typicalexamples of chelating agents include sodium polyphosphates andethylene diamine tetra acetic acid (EDTA). Many chelating agentsare also sequestering agents (see other definitions).

CIP—clean in place.Cleaner—a chemical or blend of chemicals designed to clean. These

may be solvents, acids, bases, detergents, and/or water basedblends.

Degreaser—a cleaner that is designed to remove oils and greases.These are typically heavy duty cleaners that are designed to removegross amounts of oil and grease leaving a visually clean surfacerather than light duty fine cleaners that are designed to removelower or trace levels of oils that leave a measurably or analyticallyclean surface. Most degreasers are either high alkaline aqueouscleaners or solvent based cleaners.

Detergent—a blend of ingredients intended for cleaning that includeat least a surfactant (see other definitions) to give at least emulsify-ing or dispersing and a builder (see other definitions) to inhibitwater hardness precipitation from calcium and magnesium salts. Insome industry usage, the word detergent is used when the wordsurfactant is meant.

Dispersant—a cleaner ingredient that reacts with water insolubleparticulates to overcome electrostatic attraction by the particulateto a hard surface to create a liquid solid mixture in the form of asuspension. A typical dispersant is sodium polyphosphate.

Dissolve—a cleaning mechanism that relies on a cleaning fluid to beable to form a stable mixture with individual soil molecules. Inaqueous cleaners, one of the cleaning mechanisms is for the waterto dissolve water soluble soils.

Emulsifier—a cleaner ingredient that lowers the interfacial tensionbetween immiscible liquids such as oil and water thereby allowingthem to mix. A typical mechanism for emulsifying is for the emulsi-fier to form a micelle, which in the case of oil and water involves asmall droplet of oil surrounded by emulsifier such that the emulsi-fier is in contact with the water and the entire surrounded dropletor micelle is dissolved in the water. Emulsifiers are surfactants (seeother definitions).

Excipients—fillers, non-active pharmaceutical ingredients.GC—gas chromatography


end of the molecule that is hydrophilic (“water loving”). Thehydrophilic end of the molecule is stable in water and thehydrophobic end of the molecule is more stable out of the waternext to the air, particulate, oil or surface away from the water solu-tion. This means that a surface active agent can act as a wettingagent to allow a cleaner to wet a surface or penetrate into smallcracks and crevices to perform cleaning. A surface active agentreact with a particle to act as a dispersant. A surface active agentcan act as an emulsifier with oil. Surface active agents are eitheranionic, nonionic, cationic, or amphoteric (see other definitions).

Surfactant—see surface active agent.Titrate—wet chemistry test to detect an amount of something.TOC—total organic carbon analysis.UV-vis—ultraviolet or visible spectroscopy.

PQ—performance qualification.RAL—residue acceptance limits.Saponifier—a cleaner ingredient that reacts with a natural oil ester,

or resin ester such as rosin to split the poorly water soluble esterinto a more water soluble salt (or soap) of an acid. In the case ofmany compounds this converts a water insoluble oil or resin into awater soluble soap that in turn acts as an emulsifier to emulsify anyunreacted oil or resin and assist with cleaning. Typical saponifiersare potassium hydroxide and sodium hydroxide.

Semiaqueous cleaner—a chemical or blend of chemicals or solventsthat are used to clean that rely on a water rinse. These are usuallyeither a solvent or blend of water soluble solvents that are usedstraight without water as a cleaner followed by a water rinse, orthey may be blended with water during use.

Sequestering agent—a cleaner ingredient that is a chelating agent(see other definitions) that reacts with metal ions in a water basedcleaner to hold them in solution and bind with them tightly enoughto stop the metal ions from reacting with other chemicals or soils.A typical sequestering agent is sodium polyphosphate.

Soap—the salt of an acid. A typical example is the sodium salt ofstearic acid (sodium stearate) formed from sodium hydroxide (asaponifier—see other definitions) and glycerol tristearate (naturalanimal fat). Soap is a surfactant (see other definitions) that usuallyhas good emulsifying properties for the oils or fats from which it isderived. One issue with soap is that it can react with calcium ormagnesium hardness ions in tap water to form water insoluble cal-cium or magnesium salts that precipitate out as a soap scum film.

Solubilizing—a cleaning mechanism that involves dissolving a soilinto a single aqueous phase that relies on a “like dissolves like”principle. In an aqueous cleaner the water acts as a polar solvent tohelp solubilize polar soils. The main cleaning mechanism of sol-vent based cleaners is solubilizing or dissolving.

Solvent cleaner—a cleaner that is made up of one or more organicchemicals that have some ability to dissolve soils. Typically solventcleaners contain volatile organic compounds. Fluorocarbon basedfreon cleaners are solvent cleaners. Solvent cleaners do not have awater continuous phase present during cleaning, in fact there isusually no water present in their formulations.

SOP—standard operating procedure.Surface tension—a force that runs parallel to a surface that results

from the attraction of the surface molecules towards the moleculesthat are below the surface. This tension acts to minimize surfaceareas of a solution.

Surface active agent—or surfactants are an ingredient in mostaqueous cleaners that are chemicals that are active at solution sur-face interfaces. In the context of cleaners this means chemicals thatlower the surface tension or interfacial tension at liquid-gas, liquid-liquid, and liquid-solid interfaces. The structure of surface activeagents used in aqueous cleaners are usually oblong with one end ofthe molecule that is hydrophobic (“water hating” ) and the other


APPENDIX V

Application Case Histories1. OPTICAL WAXMORE HEAT FOR FASTER CLEANINGAn optical lens manufacturer had been using ALCONOX pow-dered detergent in a heated ultrasonic bath for years to remove awax from the lens during manufacturing. As production grew,this system was not able to clean fast enough. By increasing thetemperature, adequate cleaning performance and speed wereachieved.

Initial Problem SolutionTime 10 min 5 minTemp 60 deg C 70 deg CAgitation ultrasonic ultrasonicChemistry 1% ALCONOX 1% ALCONOX Rinse deionized water deionized waterDry air airProblem cleans to slow


3. PHARMACEUTICAL TABLET COATING EQUIPMENTSOIL CHANGE CAN REQUIRE CLEANER CHANGEA pharmaceutical company had been using a typical high alkalinecleaner for manual cleaning of tablet coating equipment. Thisworked fine with their standard tablet coatings. When the compa-ny started to make tablets with enteric coatings, they observedthat their standard cleaner could not even get their coating equip-ment visually clean. By changing to an acid cleaner that waseffective on the water insoluble inorganic salts used in the entericcoating they were able to get their equipment clean.

Initial Problem SolutionTime 10 min 10 minTemp 50 deg C 50 deg CAgitation manual manualChemistry 1% High Alkaline 2% CITRANOXRinse deionized water deionized waterDry air airProblem system could not clean enteric coating

on tablet coating equipment

2. PRECISION MANUFACTURING PROCESS OILSHIGHER CONCENTRATION INCREASES BATH LIFEFor years, a metal valve manufacturer had been using LIQUI-NOX liquid detergent in an immersion tank that was made upand depleted in one shift to remove process oils from metalvalves. As production grew, the number valves and quantity ofoils to be removed increased. The valve manufacturer observedthat toward the end of the day the tank did not clean as well as atthe beginning of the day. By increasing the concentration ofdetergent, the manufacturer was able to increase the soil capacityof the solution and thereby extend the bath life to meet his needs.

Initial Problem SolutionTime 20 min 20 minTemp 50 deg C 50 deg CAgitation soak soakChemistry 1% LIQUI-NOX 1.5% LIQUI-NOXRinse deionized water deionized waterDry air airProblem tank did not last long enough


5. WASTE TREATMENT FILTERSENZYME CLEANER CURES BIOFOULED FILTERSA small scale in-house waste treatment filtration plant was beingused to remove oils from a waste stream at a manufacturingplant. The filter membranes were typically cleaned with a highalkaline cleaner at high heat. Finally bio-fouling began to occur inthe filter and the resulting proteinaceous soils would crosslinkand become tenacious when exposed to the hot alkaline cleaningsolution. The filter flow rates and pressures would not recoverafter cleaning. The solution was to treat with TERG-A-ZYMEenzyme cleaner at moderate temperatures to restore the filters totheir normal flow rates and pressures.

Initial Problem SolutionTime 1 hour 1 hourTemp 55 deg C 55 deg CAgitation circulate circulateChemistry high alkaline 1/2% TERG-A-ZYMERinse tap water tap waterDry none needed none neededProblem fouled filter membranes

4. ARCHITECTURAL GLASS MANUFACTURER SEES SPOTS WHEN SETTING UP MANUFACTURING IN A SITE WITH HARD WATERDEIONIZED WATER STOPS WATER SPOTSAn architectural glass manufacturer had one plant where theyused DET-O-JET cleaner to clean glass prior to coating. In theirexisting plant the tap water was soft without much dissolved cal-cium or magnesium in it. The manufacturer was able to cleanand rinse sheets of glass in a conveyor spray system using tapwater to rinse prior to air knife drying. When they set up anotherplant in another part of the country they kept getting water spotsbecause the local water at the new plant site was hard water witha lot of dissolved calcium and magnesium in the water. Byswitching to a deionized water rinse at the new plant and by beef-ing up the air knives, spot free drying was achieved.

Initial Problem SolutionTime 10 s/ft 10 s/ftTemp 55 deg C 55 deg CAgitation spray sprayChemistry 1/2% DET-O-JET 1/2% DET-O-JETRinse hard tap water deionized waterDry air knife airProblem water spots

7. LABORATORY PIPETS FAIL TO DELIVERINCREASED AGITATION IMPROVES CLEANINGAn analytical laboratory had been using volumetric pipets to pre-cisely measure volumes of analytical reagents. When they cali-brated their pipets they found that their old pipets were not asreliable as brand new ones. The problem was traced to incom-plete cleaning. The old cleaning process involved soaking thepipets in a static soak bath and then rinsing them in a siphonpipet rinser before air drying. By adding ALCOTABS tablets tothe siphon pipet rinser, a concentration of detergent becameavailable for cleaning during the higher agitation rinse process tocomplete the removal of residues that had been loosened duringsoaking. After the ALCOTAB had completely dissolved in thesiphon rinser, rinse water continues to flow and rinsing is completed.

Initial Problem SolutionTime 8 hours 8 hoursTemp ambient ambientAgitation soak soak followed by circulateChemistry lab detergent lab detergent plus ALCOTABSRinse DI water DI waterDry air airProblem soaking alone could not remove all

reagent residues in pipets


6. WINE TASTING GLASSESELIMINATING DETERGENT FRAGRANCE RESIDUES The world renowned wine critic Robert Parker observed in hisbook BORDEAUX, “I can’t begin to tell you how many dinnerparties I have attended where the wonderful, cedary, blackcurrantbouquet of 15- or 20-year-old Pauillac was flawed by the smell ofdishwater detergents...” In fact the human palate is very sensitiveto fragrances found in many detergents. A major supplier of winetasting glasses found that he was able to satisfy the needs of hisdiscerning clientele by suggesting they use free-rinsing, fragrance-free LIQUI-NOX cleaner instead of the depositing fragrance con-taining household dishwashing detergents they had been using.

Initial Problem SolutionTime 30 sec 30 secTemp 50 deg C 50 deg CAgitation manual manualChemistry dish detergent 1% LIQUI-NOXRinse tap water tap waterDry air airProblem Fragrance residues on wineglasses

interfered with wine bouquet

178 The Aqueous Cleaning Handbook Appendix 179

APPENDIX VI

IndexAAbsorption, 25, 27, 145, 151, 153Acid cleaners, 44, 46, 84, 165Acrylic, 86, 91Activated carbon, 130-132, 135Additives, 9, 12, 15-16, 75ADI carryover, 123Aggressive, 22-23, 38-39, 42, 46-

47, 56, 90, 134-135, 167Agitation, 13, 17, 19-20, 22, 23,

28, 30-31, 34, 38, 39, 43, 52, 54,55, 56, 57, 62, 68, 77, 80, 92,97, 101, 103, 108, 116, 171-177

Air knife, 26, 59, 107, 174Air pollution, 52Air/solution interface, 20, 28, 80Alkaline, vii, 11-13, 14, 16-18, 37,

44-46, 56, 66, 68-69, 80, 82-85,89, 90-94, 107, 137, 139, 158,159, 163, 165-167, 173, 175

Alkaline cleaner, 17, 46, 165Alkaline salt builders, 11Aluminum, 34, 39, 42, 44, 60, 66,

78, 88, 91, 107, 110, 164Aluminum foil, 110Amphoteric surfactant, 10Analytical method, 119-120, 125-

126Anion, 135, 151Anionic surfactant, 9-10, 125,

165, 167Anodized part, 88Anti-redeposition, 9, 15, 20Aquatic toxicity, 157Aqueous, iii, vii-x, 1-2, 4-9, 13-

16, 18-20, 23-25, 27, 31, 39, 41-44, 46, 48-49, 51, 61-62, 65, 67-

69, 87-93, 95, 127, 131-132,134, 138-139, 151, 153, 155-160, 165-166, 168

Aqueous cleaner, iii, vii, ix-x, 1-2,4, 6-9, 13-16, 19-20, 27, 41, 46,48-49 51, 61-62, 67-68, 87-91,93, 95, 127, 155-160, 165-166,168

ASTM, 142, 145, 153Atomic absorption (AA), 145Atomizer, 141, 143, 146Automatic syphon washing, 81

BBatch cleaning, 35, 78Bath dumping, 46Bath life, 14, 34, 37, 130, 135,

172Bench-scale, 54, 57-60, 63Bench-scale testing, 57-60Bioburden, 122, 124, 165Biodegradable, 14, 45, 48, 156-

157Biotechnology, 78, 128Blender, 71Blood, 65-66, 78, 80, 83, 164Blood-born pathogens, 66Blow-drying, 26BOD, 129, 131, 162Body fluids, 65-66, 78, 80, 164Builder, vii, 1, 9, 11-12, 14, 135,

165-167

CCalcium, 6, 11-13, 15, 24, 32,

135, 166, 168, 174Carbon, 3-4, 86, 121, 124-126,


DDeflocculation, 13-14, 166Defluxing, 87Deionized water, 23-24, 30, 32,

54, 58, 82, 98, 104, 106-107,145, 149, 171-174

Detection limit, 123Detergency, 2, 15-17, 44, 52, 69Detergent concentration, 21, 34,

37, 38, 61, 147Detergent solution, 13, 28, 37-38,

68, 80, 98-100, 105, 107, 116,132-133, 137

Dipole moment, 6-7, 85Disinfectant, 10, 103Dispersant, 9-10, 43, 92, 165-167,

169Dispersing, 13-14, 17, 33, 35, 42,

56, 94, 137, 166Displacement, 25, 58Disposable, 45, 48, 67, 78, 79Disposal, 15, 41, 52, 79, 103, 129-

130, 134, 137Dissolved inorganic solids, 129Dissolved organics, 129Dissolving, 1, 6, 15, 17, 22, 55,

167-168Distilled water, 6, 23-24, 32, 81-

82, 98, 104Drying, vi, 19, 24-29, 31, 33, 39,

51-52, 54, 58-59, 61, 75, 80-81,88-89, 97-98, 100, 102, 105,107, 112-114, 116, 124, 174,177

Drying method, 19, 24, 33, 51,54, 58, 59

EEconomic factors, 137Economy, 21, 45EDTA, 12, 15, 166Electron spectroscopy, 142, 150Electronic component, ix, 24, 32,

84, 138Electronic solder flux cleaning,

20

Electronics, 24, 39, 44, 84-85, 87,164

Electrostatic repulsion, 71Emulsification, 13, 137Emulsified oils, 15, 129, 134Emulsifier, vii, 1, 9, 11, 13-14,

85, 165-169Endoscopes, 66Endotoxin, 68, 79, 122, 124Environmental and water test-

ing, 82Environmental considerations,

43, 48Enzymatic detection, 121Enzymatic hydrolyzing, 55Enzyme, 15, 44, 65-66, 68, 80,

84, 94, 114, 125, 163, 167, 175EPA Priority Pollutants, 45, 48Equipment "blanks", 83EU, 67, 125Eutrophication, 157, 158Evaluation method, 51, 54Evaporation, 3, 24, 25, 33, 116,

130, 136, 141, 145Evaporators, 130Extenders, 16Extraction, 141, 143-145, 151

FFDA, 67-68, 73, 121, 125, 128,

164-165Ferrous, 42Filler, 16, 45, 46, 68, 166Filter, iv, 26, 36, 67, 75, 78, 84,

88, 94, 114, 122, 129, 131-135,141, 144, 156, 164, 175

Flammable, 45, 94, 159, 160Flash point, 47, 132, 138Flocculent, 129Flow-through clean-in-place, 22Fluid processing, 93-94Foam height, 136-137Foam suppressing capabilities,

21Foaming agents, 15, 20

130-132, 135, 142, 150Carbon coulometry, 142, 150Carcinogens, 82Cationic surfactants, 10Cavitation, 56-57, 105-106, 116Centrifugal drying, 26Ceramic, 44, 60, 80, 84-85, 88,

90-91, 164Certificates of Analysis, 21, 127CFC(s), v, vii, 2-5, 8, 44, 85, 87,

162Chamber flexibility, 73Change control/maintenance,

119Chelating, 9, 11-12, 15, 42, 85,

90, 93, 166, 168Chelating agent, 9, 11-12, 15, 42,

85, 90, 93, 166, 168Chemical drying, 25Chlorocarbon, 3Chlorofluorocarbon, v, 3-4Circuit board cleaning, 24Circulation system, 36Clean Air Act Amendment, iv, v,

8, 45, 48Cleaner concentration, 12, 34,

71, 147Cleaner recycling, iv, 129, 131,

139Cleaner type, iv, 33, 161, 163Cleaning efficiency, 43, 69Cleaning method, 20, 22-23, 27,

31-35, 41, 45, 51, 54, 57, 59, 61,63, 78-80, 156, 163

Cleaning performance, ix-x, 8,31, 34, 38, 47, 54, 62, 105-106,138, 171

Cleaning process, iii, ix, 17, 19,27, 44, 52, 54, 62, 95, 99, 105,117, 119, 124, 126, 128, 133,135, 147, 155, 156, 157, 159,177

Cleaning process design, 119,126

Cleaning time, 19, 22-23, 34, 39,52, 55, 63, 117, 147

Cleaning validation, iv, 67, 78,95, 117, 119, 120, 124-125, 127-128

Clean-in-place, 22, 28-29, 36, 44,57, 67-68, 71, 80, 81-82, 91-92,94, 114-115, 164

Cleanroom, 24, 88Closed-loop, 18, 131, 132, 138,

139COD, 129, 135, 162Computer parts, 88Concentrated cleaner, 16Concentration, vi, ix, 12-14, 16,

21, 31, 33-34, 37-39, 42, 46, 58,61-62, 70-71, 79, 90, 97, 108-109, 111, 122, 133, 136, 147,151-152, 157, 167, 172, 177

Concentration gradient dissolv-ing, 58

Conductive residue, 24, 84Conductivity, 37-38, 72, 97, 111,

121, 125, 135-137Contact-angle, 54, 146, 149Contaminant, 6, 15, 23, 52, 83,

84, 85, 86, 93, 99, 105, 129,130, 131, 132, 134, 135, 143,144, 146, 148, 150, 151

Contaminant dispersants, 15Controlled foaming, 56Corrosion, 9, 15, 17, 23, 24, 33,

35, 38, 39, 60, 65, 71, 84, 86,88-89, 93, 109, 166

Corrosion inhibiting agents, 15Corrosion inhibition, 9, 38, 166Corrosion inhibitor, 15, 24, 39,

71, 88Corrosivity, 47, 52, 138Cosmetic, ix, 88, 92, 148, 164Counterflow-cascade, 23, 58Counterflow-cascade rinse, 23Coupling agent, 16Coupon sampling, 121, 122Cross-contamination, 24, 65-67,

82-83, 95Cycle time, 56, 73


Low-foaming detergent, 20, 30,81

Low-power microscope inspec-tion, 142

MMachine cleaning, 20, 81Machine washing, 20, 29, 81Magnesium, 6, 11, 13, 15, 24, 32,

42, 135, 166, 168, 174Manual, 20, 22-23, 28, 34-36, 44,

47, 57, 63, 55-67, 68, 71, 76,80, 82-83, 85, 91-94, 97, 98-102,163-164, 173, 176

Manual cleaning, 20, 23, 28, 34,35, 36, 47, 57, 63, 80, 83, 99-100, 102, 173

Manual surface cleaning, 98Mass displacement, 58Mass spectrophotometry, 142Master validation plan, 119Material Safety Data Sheet, vi,

45, 47, 158-159, 162Measuring cleanliness, iv, 141Mechanical action, 5, 12, 13Mechanical agitation, 20Medical device manufacturing,

78, 122Metal finishing, 88Micelle, 11-12, 79, 166-167Microfiltration, 132, 134-135Millipore filter measurement,

141, 144Minimal system, 63Mixer, 71, 84, 114, 116, 123Montreal Protocol on Substances

that Deplete the Ozone Layer, 5

NNeutral, 14, 16-17, 37, 65, 69, 71,

84, 91, 93, 137, 163, 167Nonferrous, 42Nonionic, 9-10, 14, 20, 85-86,

136, 137, 151, 167, 169Nonionic contaminant, 86Nonionic surfactant, 10, 14, 125,

167Nonpolar, 85Nonvolatile Residue Inspection

(NVR), 141, 143Nuclear, 93, 164

OOil evaporation, 141, 145Oil viscosities, 61Oleophilic, 9, 11, 133Operating cost, 46, 131Operational Qualification (OQ),

119, 167Optical microscopy, 141, 144Optically stimulated electronic

emission, 142, 151Optics, 91-92, 164Organic, v, vi, ix, 1, 3, 4, 5, 6, 8,

9, 10, 11, 13, 15, 32, 41, 42, 44,45, 48, 60, 82, 84, 85, 86, 88,90, 94, 121, 124, 125, 126, 129,130, 131, 135, 143, 145, 150,151, 158, 160, 162, 165, 167,168, 169

Organic-free, 82OSEE, 54, 142OSHA, 45, 47, 159-160, 162Outgas, 84Overkill system, 63Ozone depletion, 3, 45

PParenteral medical device, 79Particulate, 11, 17, 22, 42-44 56,

61, 74, 75, 85, 91, 103, 114,115, 132, 137, 150, 164, 166,169

Parts washer, 30, 32, 44, 85, 91-92, 133, 164

Pathogens, 66PC board, 30-31, 85PC board washer, 30, 31Performance Qualification (PQ),

119Permeate, 133pH, 10, 14-17, 37, 39, 65, 69-71,

Food and beverage processing,83

Forced-air, 26, 39, 59Forced-air drying, 39Free alkalinity, 37, 135Free-rinsing, 41, 44, 58, 79, 176FTIR, 54, 135, 142, 151

GGas chromatography, 126, 142,

151, 166Glass, iv, ix, 42, 44, 59, 61, 65,

67-69, 70-71, 74, 79-80, 82-84,87, 90-91, 100, 102-103, 107,122, 144-148, 150, 164, 174

Glassware washer, 30Global warming, v, 3-5, 162GMP, 66, 72-78, 111, 113, 119GMP washing machines, 72Gravimetric, 54, 141, 145

HHazardous, vi, vii, 3, 8, 44-45, 47,

91, 135, 137, 155-156, 158-160,164

Hazardous chemicals, vi, 8, 155,159

Hazardous substance list, 45, 47HCFC, v, vii, 2-5, 8Healthcare, 65-66, 164HEPA filter, 75High emulsifying, 20, 42, 55, 90,

92, 136High volume/low pressure, 56-57High-agitation spraying, 55High-foaming cleaners, 56HPLC, 121, 126, 135, 145, 167Hydrochlorofluorocarbon, v, 3-5Hydrogen bonding, 7, 10Hydrolysis, 13, 16, 17, 56, 135,

165Hydrolyzed, 17, 167Hydrophilic, 9, 11, 14, 133, 146,

167, 169Hydrophobic, 9, 11, 45, 133, 142-

143, 145-146, 148, 167-169Hydrotropes, 16Hydroxide, 2, 14, 16, 69, 136, 168

IICH, 67, 125, 167Ignitability, 138Immersion, 5, 12-14, 28, 30-32,

34-36, 55-57, 63, 79, 84, 90, 92,116, 172

Immersion cleaning, 13-14, 32,34, 36, 55-57, 79, 84, 90, 92

Ingredients, 1, 7, 9, 11, 14-16, 21,37, 42, 45-47, 67, 75, 83, 87, 92-3, 111, 121, 124-125, 155-159,165-167

Inhibitor, 15, 24, 39, 46, 71, 88Inorganic, 6, 9, 11, 14, 17, 42, 44,

60, 82, 90-91, 114-115, 129,131, 136, 143, 145, 151, 164,173

Inorganic soil, 9, 42, 44, 60, 90In-situ particle counting (ISPM),

146Insoluble oils, 1, 11, 129Insoluble particles, 14Installation Qualification (IQ),

119Interfering detergent residue, 44Ion chromatography (IC), 142,

151Ionic, 10, 85, 86, 87, 135-137,

151, 167Irritants, 47

LLaboratory cleaning, 30, 79-81LD50, 122-123Limonene, 5Lipophilic, 14Liquids, ix, 5, 15, 46, 149, 151,

166Lot number tracking, 21Low volume/high pressure, 56-57Low-foaming, 20, 29-30, 56,81,

92, 163

Scanning Electron Microscopy(SEM), 142, 152

Secondary Ion MassSpectroscopy (SIMS), 142, 152

Semiaqueous cleaner, 5, 14, 17,160, 168

Separator, 130, 134Sequestering agent, 11-12, 15,

44, 166, 168Sequestration, 13, 165Sessile drop technique, 149Silicates, 14Skimmer, 130, 134, 139Soak, 19-20, 22-24, 28, 30, 32,

35-36, 44, 58-59, 62, 66-68, 71,80-83, 85, 91-93-94, 99, 105,115, 139, 163-164, 172, 177

Soak cleaning, 22, 35, 36, 71Soaking, 22, 23, 28, 35-36, 55,

65, 80, 93, 99, 105, 177Soap, 1-2, 6, 10, 12-16, 20, 167-

168Soil, 1-3, 5-7, 9, 11-17, 19-23, 28,

32-34, 37, 41-46, 51-52, 54-55,57-61, 65-66, 68, 78, 80-83, 85,89-90, 91-94, 97, 99, 105, 113,117, 132-133, 135-138, 141,143-146, 155-156, 159, 166-168,172-173, 175

Solder paste, 87Solubilization, 13, 25, 42Solution recharge, 133Solvent, v, vi, vii, ix, 1-8, 13, 15,

25, 27, 39, 41, 44-45, 46-48, 52,59, 61, 87-88, 90-91, 131-132,143-145, 151, 158-160, 164,166, 168

Spray, 12-13, 20, 22-23, 28-36,44, 47, 55-57, 63, 67-68, 71, 74,80-83, 85, 91-94, 111, 113, 116-117, 144, 158, 163-164, 174

Spray agitation, 30, 55Spray cleaning, 13, 22-23, 34-36,

47, 55-57, 158Spray clean-in-place, 28-29, 36,

44, 68, 80, 82-83, 91, 94, 164Stabilizers, 15

Stainless steel, 15, 42, 44, 59, 65,67, 69, 71, 74, 75, 82-84, 91,107, 114, 115, 164

Stainless steel cleaning, 69Standard operating procedure,

iv, 67, 78, 97, 111, 117, 126, 168Steel, 15, 39, 42, 44, 59, 65, 67-

71, 74, 75, 77, 82-84, 91, 103,107, 114-115, 164

Sterilization, 65-66, 103-104Sterilizing, 65, 78Substrate, iv, 1, 3, 12-15, 17, 19-

20, 23-26, 28, 32-34, 42, 44, 51-52, 54-56, 59-61, 69, 88-89, 92,149, 164

Surface active agent, 1, 2, 9, 165,167-169

Surface contact-angle, 54Surface energy, 141, 145-146,

148-149, 153Surface tension, 11, 12, 14, 21,

43, 90, 149, 166, 168Surfactant, vii, 1, 5-6, 9-14, 16,

20, 21, 25, 39, 44, 48, 125, 135,136, 137, 157, 160, 165-169

Surfactant-free cleaner, 20Suspended solid, 129Suspension, 11, 43, 67, 133, 166Swabbing surface, 121Synthetic solvent, 2-3

TTank, 22-24, 26, 28-31, 36, 46,

55, 57-59, 67, 71, 80-81, 93-95,97-98, 100-101, 104-107, 110,114-117, 129-130, 132, 134,139, 172

Tap water, 11, 23, 24, 58, 82, 92,98, 99, 104, 105, 106, 114, 168,174, 175, 176

Tape test, 141, 144Temperature, 12-15, 17, 19-23,

29-31, 33-34, 38-39, 42-43, 52,54-55, 61-63, 71, 73, 75, 77, 81,86, 90, 92, 97, 99, 101, 105,111-117, 130, 133-134, 136,171, 175

Appendix 185

84, 90-91, 93, 97, 100-102, 109,121, 129, 134, 136-138, 157,165, 167

Pharmaceutical, iv, 24, 32, 66-69,71-72, 77, 78, 82, 92, 95, 119-122, 128, 138, 164-166, 173

Phosphate, 83, 125, 158, 164Physical drying, 24-26Physical filtration, 37, 132Physical separation, 133Pilot scale, 63, 71, 78Piping system, 71, 94pKa, 69, 70, 71Placebo sampling, 121Plastic, ix, 34, 39, 42, 59, 65-66,

68, 74, 78-79, 84, 89-90, 93,144, 153

Plastics compatibility, 89Polar, 6-7, 10, 85, 168Polar soil, 6-7, 168Polar solvent, 6, 168Polymerized rosin, 87Porous surface, 60Postcleaning handling, 19, 27,

34, 97, 112Powder, 15-16, 46, 163Power spray wand, 29Power washer, 29Precleaning handling, 19, 31, 97Presoaking, 21-22, 99, 105Pressurized spray, 30Protein, 17, 34, 69, 84, 99, 105,

167Proteinaceous soil, 44, 65-66, 80,

83, 164, 175

QQuality control, 21, 52, 73, 93,

128, 134, 138, 149

RRCRA, 45, 48, 138, 160, 162RCRA Hazard Classification, 45Reactivity, 45, 47, 69, 127, 138Recycling, iv, 13, 18, 43, 46, 79,

129, 131-135, 137-139, 147, 156Refractometry, 136-137Regulatory review, 159Residue, ix, 6, 17, 21, 23-26, 28,

30, 32, 39, 41, 44-45, 67-71, 78-80, 82-90, 92, 94-95, 115-117,120-127, 141-145, 148, 164,168, 176-177

Residue acceptance criteria, 121-122

Residue detection method selec-tion, 120-121

Residue identification, 120-121Residue-free, 45Retentate, 133Rinse, 13, 19, 21, 23-24, 28-33,

39, 44-45, 51, 58-59, 68, 71-72,80-82, 89, 92, 99-100, 106-108,111-113, 115-116, 121-124, 132,134-135, 147, 156, 168, 171-177

Rinse aid, 44-45Rinse procedure, 32, 81, 99, 106Rinse water sampling, 72, 121Rinsing, vi, 5, 9, 13, 21, 23-25,

29, 31-32, 39, 41, 44, 52, 54, 58-59, 61, 72, 79, 81-82, 88-89, 92,98, 102-107, 111, 114, 116, 124,134-135, 155-156, 176-177

Rosin, 44, 85-87, 164, 168Rubber, 4, 42, 47, 82-83, 89, 91,

102, 107, 164

SSafety based limit, 122, 123Salt, 1, 11, 14, 15, 17, 24, 33, 37,

60, 68, 83, 85, 87, 88, 90-91, 94,134, 135, 136, 164, 166, 167,168, 173

Sampling method, 120-121Sampling procedures and recov-

ery, 119Sanitizer, 30Saponification, 9, 13-14, 167Saponifier, 2,15, 20, 168Scale, 16-17, 44, 80, 83, 88, 91,

115, 164Scale-up, 55, 57-60


Terpene, 3, 5Test, 51, 54, 59-61, 119, 141, 144,

148Test acceptance limit, 119Test cleaning, 51, 54, 61Test soil, 51, 60Test substrate, 51, 59Testing, 19, 54-55, 57-62, 68, 82-

83, 86, 113, 120, 122, 145-146Testing, iii, vi, 51, 113, 153Time, vii, x, 12, 17, 19, 22-23, 25,

28, 31, 34-35, 38-39, 43, 46-47,52, 54-57, 61-63, 71, 73, 75, 77,80, 89, 97, 99-100, 105, 110-111, 114, 116-117, 124, 132,139, 147-149, 152, 156-157,171-177

Titration, 27, 37, 121, 125-126Total alkalinity, 135Toxicity, 47, 52, 82, 88, 120, 122,

127, 138, 157Trace analysis, 82, 144-145Trace metals, 80, 82, 164

UUltrafiltration, 18, 114, 133-135Ultrasonic, 12-13, 20, 22, 29-32,

34-36, 44, 57, 66-68, 78, 80-83,85, 88, 90-92, 97, 104, 106-108,110, 146-147, 163-164, 171

Ultrasonic cleaning, 20, 22, 29,35, 57, 67, 78, 81, 91, 97, 104,106-107, 110, 147

Ultrasonically agitated rinsing,23

USP, 111, 125UV, v, 121, 126, 131, 141, 143,

145, 151, 162, 169UV spectroscopy, 121

VVacuum drying, 25, 33, 39Vapor degreasers, 5Vesication, 86Visual inspection, 54, 61, 141-

142, 144VOC, v, 4, 8, 45, 162VOCs, 3-4, 41Volatile, v, ix, 2-4, 8, 41, 44-45,

48, 52, 59, 61, 91, 156, 158-159,162, 164, 168

WWash cycle, 29, 72, 81, 111Waste treatment, 52, 94,175Waste-treatment filtration, 94Wastewater treatment, iv, 129,

130, 131Water break, 141-143, 146Water drop surface energy test,

148Water testing, 82Wax melting points, 61Waxy or oily soils, 22Wetting, 1, 9, 11, 13-14, 20, 43,

56, 90, 150, 153, 169Wetting agent, 1, 9, 11, 169WFI, 68, 74, 79, 111, 121White residue, 86-87Wiping and visual inspecting,

141, 142Worker safety, 41, 52, 158, 160

ZZero-discharge, 156


cleaning validation book

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