DOCUMENT RESUME

ED 327 716 CE 056 778

AUTHOR Engelbrecht, Nancy; And OthersTITLE Pneumatics.INSTITUTION Central Community Coll., Grand Island, NE.SPONS AGENCY Office of Vocational and Adult Education (ED),

Washington, DC.PUB DATE 90

CONTRACT V199A90067NOTE 61p.; For related documents, see CE 056 774-777.PUB TYPE Guides - Classroom Use - Materials (For Learner)

(051)

EDRS PRICE MF01/PC03 Plus Postage.DESCRIPTORS *Behavioral Objectives; Community Colleges;

Construction (Process); *Course Content; *LearningActivities; Lesson Plans; Measurement Equipment;Occupational Safety and Health; Plumbing; *Pressure(Physics); Repair; Test Items; Two Year Colleges;Units of Study

IDENTIFIERS *Pneumatics

ABSTRACTThis unit on pneumatics, for use in postsecondary

programs, is organized in eight sections. Each section consists ofinformation sheets with line drawings and multiple-choice questionsfor each topic in the sections. Answers are provided at the back ofthe book. The following topics are covered: (1)introduction--pressure, principles of gases, uses of pneumatics; (2)safety; (3) compressors; (4) air treatment; (5) pneumatic pipingsystems; (6) pneumatic valves; (7) cylinders; and (8) miscellaneousvalves/air logic and diagrams. Knowledge-based competency objectivesare provided for each topic. (KC)

***************%V.****************************************************** Reproductions supplied by EDRS are the best that can be made *

* from the original document. *

***********************************************************************

Project DirectorRon Vorderstrasse

Pro lict SecretaryJan Wisialowski

Technical ConsonantJay Tallmon

Technical WritersNancy Engelbrecht

Lynne GrafStacey Oakes

0 Copyright, Central Community College

NOTICE TO READERCentral Community College makes no representation or wammties of any kind regardirr, the contents of these instructional materials.However, efforts ha% e been included to verily the information contained herein. The college shal not be liable to anyone with respectto any liability, !oss, or damage caused or alleged to be caused directly or indirectly by these instructional materials.

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PNEUMATICS

Knowledge-Based Competency Objectives

Section 1: Introduction

1. Distinguish between a gas, liquid, and fluid.

2. Identify the three areas of pressure evident inpneumatic systems.

3. Identify the three basic principles of

4. Know the applications and advantages of pneumatics.

Section 2: Safety.

1. Know both personal and equipment safety measures regardingpneumatics.

2. Know the safety color coding for pneumatics.

Section 3: Symbols and Formulas

1. Be familiar with pneumatic symbols and formulas.

Section 4: Compressors

1. Know the various compressor groups, types, and operations.

2. Know the unloading methods for output control.

Section 5: Air Treatment

1. Know the types of driers used in pneumatics.

2. Be famtliar with the types of filters used tc removecontaminants from air.

3. Know the process of refrigeration.

Section 6: Piping Systems

1. Know the pneumatic piping systems, how to check for air leaksand join pipes.

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Section 7: Valves

1. Know the two main categories of valves and the valves thatfall into those categories.

2. Know valve functions and operations.

Section 8: Cylinders

1. Know the types of cylinders and their functions.

2. Kaow the various mounting styles of cylinders.

t--c.)

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PNEUMATICS OUTLINE

I. IntroductionA. PressureB. Principles of GasesC. Uses of PneumaticsD Advantages and Disadvantages of Using Pneumatics

II. SafetyA. Personal SafetyB. Equipment SafetyC. 0.S.H.A.D. SolventsE. Electrical ShockF. General SafetyG. Sobey Color Code for Pneumatic Systems

III. CompressorsA. Types of Compressors

1. Positive displacemenca. reciprocating pistonb. vanec. helical

1. dry2. oil-flooded

d. diaphragme. lobed-rotorf., single and double acting

2. Dynamica. radialb. axial flow

B. Control of Compressor Capacity1. Common unloading methods for output control

a. bypassb. start-stopc. inlet valve regulationd. inlet throttlinge. inlet closure

C. Noise LevelsD. Compressor VentilationE. Compresso:7 Installation

IV. Air TreatmentA. Driers

1. absorption2. adsorption3. low temperature

B. AftercoolingC. Filters

1. air filters2. dry filters

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D. Receiver Tank

V. Pneumatic Piping SystemsA. Types of Pipe

1. plastic2. copper

B. Pipe Systems1. TrAd2. decentralized3. loop

C. Joint Types1. joining plastic pipe2. joining copper pipe

a. compression jointb. flared jointc. soldered joint

D. Installation RequirementsE. Air Leaks

VI Pneumatic ValvesA. Pressure Control Valves

1. Relief Valves2. Reducing Valves

a. constant reduced pressure valveb. fixed-amount reduction valve

B. Directional Control Valves1. check valve2. rotary valve3. spool valve4. two-way directional valve5. three-way directional valve6. four-way direcitonal valve7. valve operation and control8. manually operated valves9. automatically operated valves

10. solenoid valves11. pilot actuated valves

VII. CylindersA. Types

1. single-acting cyliLdersa. diaphragm cylinderb. rolling diaphragm

2. dauble-acting cylinderso. vane cylinder

B. Cylinder Mounting Styles1. fixed centerline mounting2. fixed noncenterline mountingO. pivoted rylinder mountings

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VIII. Miscellaneous Valves/Air Logic and DiagramsA. Quick Exhaust ValvesB. Silencers or MufflersC. Air BoostersD. Air Logic SymbolsE. Actuating Devices SymbolsF. Schematic Diagrams

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PNEUMATICS

I. INTRODUCTION TO PNEUMATICS

Pneumatics is d?.rived from the Greek word pneumatikos, whichmeans air or wind. The word has evolved to include any gasunder pressure used to perform work. Pneumatics, along withhydraulics, are commonly combined into a larger family ofpower systems, and referred to as fluid power system. Fluidpower systems use gases, liquids, and fluids to tzansferenergy.

A fluid is a substance that flows easily and tends totake on the shape of its container. A fluid can either be agas (such as compressed air, nitrogen, or carbon dioxide) or aliquid (such as oil or water). A liquid is a substance thatis capable of being poured. An important distinction toremember is that all gases are fluids, but not all fluids aregases. Further, a fluid system that uses gas is a pneumaticsystem. Pneumatic systems use compressed air to transmitforce from one point to another.

A. PRESSURE

Pressure is defined as force divided by the area overwhich the force is exerted. Pressure can be meastrzed byeither pounds per-square-inch gage (PSIG) or pounds per-square-inch absolute (PSIA).

Pressure = force = lbs. = PS1Garea sq. in.

Atmospheric pressure is measured in pounds per-square-inch(PSI), and at sea level is 14.7 PSI. Atmospheric pressuredecreases as altitude increases. Therefore, the pressureof the atmosphere on a 10,000 ft. mountain top will beless than on a beach at sea level.Pneumatic system pressure is the pressure of thecompressed gas working within the system measured in PSI.PSIG readings are the norm and are commonly referred to asPSI. PSIA is primar;ly used in theoretical applicationssuch as for design criteria.

B. PRINCIPLES OF GASES

Since pneumatic systems refer to tools using gases tocreate force, it is important to know three basicprinciples of gases. The first principle is that gaseshave no shape. Gases take the shape of their container.This makes them easy tc pipe anywhere. The secondprinciple is that gases are highly compressible. Thethird principle is that gas transmits pressure equally in

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all directions when force is applied. Regardless of acontainer's shape o size, the amount of pressuretransmitted remains the same provided the amount of forceis constant.

C. USES OF PNEUMATICS

Some uses of pneumatics can be found listed below.

Air Brake Drilling PressurizingAir Cylinder Elevating Process ControlAir Motor Forming ReamingChipping Grinding RivetingClamping Hoisting Screw DrivingConveying Painting Stapling

D. ADVANTAGES AND DISADVANTAGES OF USING PNEUMATICS

There are both advantages and disadvantages of usingpneumatics.

Some advantages include:

1. Air is readily available and easy to transport.

2. Air is a stable, and therefore safe, gas.

3. Speeds and forces of pneumatic systems varyindefinitely.

4. Pneumatic tools and equipment can handle an overload ofpressure without damaging the equipment.

Some disadvantages of pneumatics include:

1. It is difficult to deliver constant compressed air tosystem tooling.

2. The overall cost of systems and tooling is expensive.

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oUESTIONS -- INTRODUCTION

Choose the best answer for the following:

1. means any gas under pressure used to performwork.

a. Compressionb. Reciprocationc. Pneumaticsd. Adsorption

2. A has no distinct shape or volume.

a. Liquidb. Gasc. Fluidd. All of the above

3. A substance that flows easily and takes the shape of itscontainer is a:

a. Iceb. FluidC. Plasticd. Solid

4. Two pressures in a pneumatic system are:

a. Pneumatic and atmosphericb. Atmospheric and vacuumc. Pneumatic and atomicd. Atmospheric and phosphoric

5. The three principles of gases are:

a. Gases are highly compressibleb. Gases have no shapec. Gases transmit pressure equallyd. All of the abovee. a and b only

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In working with pneumatic systems, safety consciouspersonnel and safe operating equipment result in a smoothrunning, productive operation. Personnel must always readand understand safety rules and regulations before workingon sper4fic equipment and before routine maintenance occurs.The following are safety rules workers must be concernedwith when working on or around pneumatic systems orcompressed air.

A. PERSONAL SAFETY

1. When working on or cleaning compressed air systems, eyeprotection (i.e. safety goggles or glasses) should beworn.

2. Hearing protection should be worn if long exposures tonoise al:. encountered.

3. Never check for leaks, and never block air in acompressed air system with hands, arms, feet,

4. Never direct compressed air towards or near co-workersor passers-by, as highly pressurized air can passthrough skin and cause a great deal of injury or evendeath.

5. Loose clothing and loose articles of jewelry should notbe worn around rotating or energized equipment.

6. Long hair should be tied back so that it does notbecome caught in equipment.

7. Keep bare skin away from hot equipment to avoid severeskin burns.

8. Make sure appropriate personnel are advised oflocations of workers performing maintenance.

9. Workers should avoid working on energized equipment.

B. EQUIPMENT SAFETY

1. Compressed air systems must be deenergized and drainedof system pressure before maintenance can be attempted.If necessary, tag,out circuit breakers and valves.

2. The condition of pneumatic system hoses, pipes, wiring,and other equipment must be continuously checked forsigns of deterioration and wear. Replace equipment ifrequired.

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3. Yseep all work areas and machinery clean of dirt and oilcontaminants.

4. Always use properly sized tanks, valves, and systempiping to ensure that equipment will handle systemoperation pressures properly.

5. Compressed air equipment must be secured or held downwhile it is being energized, so any possible whippingaction r:oncerning flexible hosing can be controlled.

6. New or replacement components should be inspected forflaws or possible defects before installation.

7. For proper and safe operation of pneumatic systems,follow manufacturers installation and repairprocedures.

8. Strictly adhere to a regular Laintenance schedule andkeep all prior records of previously performedmaintenance.

9. The correct tools should always be used for theperformance of operations regarding pneumatic systems.Substitution and use of improper tools can damage thesystem.

C. 0.S.H.A.

0.S.H.A. stands for the Occupational Safety and Health ActthaL was established in 1970 within the Federal Departmentof Labor. This act establishes guidelines and rules thatmust be followed by employees to ensure the safety andhealth of workers in all phases of industry. Productionshould never be an excuse for personnel safety violations.Potential or suspected hazards should be reported to theproper safety officials within your company for furtherevaluation.

D. SOLVENTS

Even though pneumatic systems do not employ th's use ofchemical solvents, maintenance or cleaning operations mayrequire their use. Always be aware of manufacturers'directions and safety requirements regarding solvents.Smoking should not be permitted during solvent use as thesolvents may be flammable and/or explos:.

E. ELECTRICAL SHOCK

To prevent electrical shock when working with pneumaticsystems, make sure the correct breakers are turned off and

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tagged to prevent inadvertent energization of electricalcircuits.

F. GENERAL SAFETY

It is the employers' responsibility to ensure that safetyguidelines are followed. Safety regulations should beposted and made available to all employees. It is theemployees' responsibility to read, understand, and followthese regulations. The list of safety rules in thissection is not all-encompassing. Federal, state, andlocal rules and regulations must be taken intoconsideration along with manufacturers' guidelines andcompany rlles regarding safety.

G. SOBEY COLOR CODE FOR PNEUMATIC SYSTEMS

These colors for safety are universally standard forpneumatic systems,

Red = Supply pressure

Orange = Working pressure

Yellow = Metered flow

Blue = Exhaust

Violet = Intensified pressure

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QUESTIONS -- SAFETY

Complete the following statements by selecting the best answer.

1. 0.S.H.A. stands for:

a. Occupied Safe Hoasing Authorityb. Occupational Safe and Healthy Actionsc. Occupational Safety and Health Actd. Organized Safety Health Activity

2. Although pneumatic systems do not use in theiroperations, they may be used for maintenance and cleaning.

a. Alcoholb. Gasolinec. Cementd. Solvents

3. should be posted and made available to allemployees.

a. All safety rules and regulationsb. State rules and regulationsc. Federal guidelinesd. State safety practices

4. Working pressure is designated by the co'.or:

a. Yellowb. Orangec. Redd. Green

5. Supply pressure is designated by the color:

a. Violetb. Blackc. Yel'owd. Red

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III. COMPRESSORS

Compressors are devices that convert air at atmosphericpressure into pressurized air. The pressurized air is thenused to accomplish work.

A partial vacuum at an inlet filter iscreated by the compressor. This partial vacuumallows the air at atmospheric pressure to flowthrough an inlet filter into the compressor. Thecompressor reduces the volume of the air whileincreasing the air's pressure. Once the air hasbeen compressed, it travels to a storage tankthrough compressor discharge valves. Only whenthe tank pressure is low does the compressoroperate. When the compressor is running, airflows into the storage tank. The maximum Fig. 1 Campressor Logic Symbol

storage tank pressure is preset by a controlwhich shuts the compressor off when the desired pressure isreache(1. Discharge valves prevent the flow of air back to thecompressor.

A. COMPRESSOR TYPES

Compressors can be classified into two groups, positivedisplacement and dynamic. In positive displacementcompressors, pressu,-e increases because of a decrease inthe volume of trapped air. In dynamic compressors,pressure increases due to energy added to a moving gasthrough acceleration. These two groups of compressors canbe further classified into types of compressors

1. Positive Displacement Conpressor TypesPositive displacement compressors compiess air to highpressures for use in pneumatic power systems. Thesetypes of compressors include reciprocating piston,vane, helical, diaphragm, lobed, single and double-acting compressors.

a. Reciprocating Piston CompressorThe reciprocating piston compressor is the mostcommon type of positive displacement compressor.These compressors may be lubricated or non-lubricated, depending upon the application. Definedas a cylinder located within a bore, the cylinder is

attached to a motor. The reciprocating pistoncompressor is a single stage compressor, generallyused for systems which require 40 - 100 PSIG ofcompressed air, and in some cases can operate up to250 PSIG.Operation of this compressor occurs as thepiston moves down in the bore.

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The intake valve is opened: thusbringing in new air. As the pistonbegins its upward travel in thebore, the intake valve is closedand the pressure is increased asthe piston moves upward. As thepressure within the bore reachesthe desired level, the output valveis opened to release the pressurizedair.

Exhaustto airstoragetank

1.

Intakeffomatmosphere

Figure 3 - Compressor, ExhaustStroke

Exhaustto airstoragetank

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Intakefromatmosphere

Figure 2 - Compressor, IntakeStroke

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b. Vane Compressor

The vane compressorsare classified as themost effective of therotary positivedisplacementcompressors. Thepumping action of thecompressor is createdby vanes trackingalong the cirularhousing of thecompressor.

Fig. 4 - Vane Compressor

As illustrated above, these compressors utilize vanes thatare free floating within a rotor that is offset within acircular housing. Vanes are typically made of carbon orcloth embedded in daelonic resin to provide low friction.Vane compressors have low operating costs and may generatepressures up to 150 PSIG. Operation of this compressoroccurs as the motor turns the rotor, pulling in non-pressurized air from the intake side of the compressor. Thecentrifugal force of the rotor rotation keeps an air-tightseal with the vanes touching only the circular housing. Therotor is positioned off center to create both increasing anddecreasing volumes of air in the housing as the vanesrotate. As the rotor turns, the vanes create negative airpressrre, causing air to be drawn into the compressor. Asthe rotor continues turning, the vanes limit the air tosmaller and smaller spaces. The chamber reduces in size,forcing air out the exhaust and towards the storage tank.Thus the air is compressed and converted into a pressurizedform of output. Vane compressors are compact and runquietly, with a smooth and steady delivery of air.

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c. Helical compressorsThe helical compressor is also referred to as the screwcompressor because of the way its two rotors meshtogether, resembling two screws.

Fig. 5 Helical Screw

Helical compressorsoperate by running twomeshed rotors togetherto generate compressed%ir by drawing air inone end of thecompressor and exitingit from the other end.There are two basictypes of helicalcompressors, dry or oilflooded. Both typesmay deliver up to 125PSI.

1. Dry helical compressors usually do not requirelubrication, because of their machined clearance. Timinggears are used to turn the two screws. Dry helicalcompressors run at high rpm and are very efficient.

2. Oil flooded helical comprassors do not have timing gears,but lubrication is needed because the screws run on eachother and the oil provides an airtight seal. Oilseparators must be utilized to keep downstream air cleanof oil residue in the compressor.

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d. Diaphragm compressorsThe diaphragm compressors received their name from thediaphragm part used to intake and export air from thecompressor chamber. The diaphragm separates thecompressor piston from the air chamber, and its purposeis to prevent air contamination by the lubricating oilsof the compressor.

i

Intake

from atmosphere

t--..../---

Exhaust toStorage Tank

AIR CHAMBER

Diaphragm

_Piston

I/'

I%

.%

I

'..)

Figure 6 - Diaphragm Compressor

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The compressorfirst lifts thediaphragm todraw air intothe compressorchamber. As thediaphragm platereverses itsstroke, theintake valve isclosed and theexhaust valve isopened. Thevolume of theair is reduced,and the air ispiped into thestorage tank.As the pistonmoves downward,the diaphragmalso movesdownward, thusincreasing thevolume in theair chamber.Thesecompressors havemany light dutyapplications,and operate atroughly 30 to 40PSIG.

Irst-stage

haust to second-age intake

Iagtake fromirst-st

tmospher(s

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Second-stage intakefrom first sta e

Figure 8 - Two-Stage Compressor

Second-Stageexhaust to airstorage tank

The large piston performs the first compression. As thelarge piston moves downward in the bore, the intake valve isopened and air is brought into the cylinder at the bottom ofthe stroke. The inlet valve then closes as the piston movesupward, and the compression begins. The air is compresseduntil a specific pressure is reached, at which time theoutlet valve opens and the pressurized air is directedthrough the intercooler to the second stage piston. As thesmall piston reaches the bottom of its stroke, the inlet isclosed and the second stage of compression begins. As thesmall piston moves upward and the appropriate pressure isreused, the valve opens to exhaust the second stagepressurized air.

2. Dynamic Compressor TypesDynamic compressors deliver large yantities of air up to125 PSIG. These compressors are used mainly at a highvolume of low pressure air. The two main types ofdynamic compressors are radial and axial flow.

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a. Radial CompressorsThe radial compressor is used at very high speeds tocreate pressures, but they have a minimum flowcapacity. A radial flow compressor, also known as acentrifugal air compressor, is made up of severalchambers labeled as stages. Eact stage has animpeller located in it. As air enters a stage, therotating impeller directs the air out of the stage.The air then followb the chamber, and is routed backto the center to proceed to the next stage. Thus,as the air passes through each stage its pressureincreases. In the final stage, the air is routedeither to a storage tank or to the working part ofthe pneumatic system.

Bearing

Housing

Impeller

Shaft

Air Intake

A \tN.

Figure 9 - Radial Flow Compressor

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Coupling

Air Exhaust

b. Axial Flow CompressorsThese compressors are used for high volumes of air, andoperate at high speeds. The air flows axially throughthe compressor. Axial flow compressors have impellerswith vanes that rotate at high speeds within the housingof the compressor. As air enters the housing near thecenter of the impeller it is directed outward bycentrifugal force. The housing, due to its shape,funnels the air and creates the pressure of the air.

Air

Intake

Housing Air Exhaust

Power Shaft

Ircçeller

Figure 10 - Axial Flow Compressor

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B. CONTROL OF COMPRESSOR CAPACITY

Compressors must be regulated to meet the demands of thepneumatic system. The means by which this is controlledis through the unloading of the compressor by manual orautomatic methods. A pressure control sensor is normallyused to contro: output pressure.

There are five common unloading meth'xis for outputcontrol:

1. Bypass--This method consists of bleeding highlypressurized excess air into the atmosphere, causing thecompressor to continuously run.

2. Start-Stop--This method consists of starting andstopping the compressor as its minimum and maximumpressures are reached. This can be achieved bystarting and stopping the motor, but this may causeearly motor failure due to the frequency of the start-stop procedures.

3. Inlet valve regulationIn this method, the inlet valveis held open when no demand for air exists. Thus airis allowed to enter and exit in the same locationwithout undergoing compression.

4. Inlet throttlingThis method regulates the airadmitted into the cylinder by increasing or decreasingthe air flow at the inlet port of the compressor. Thismethod requires higher horsepower demand as thecompression increases.

5. Inlet closure--In,this method, the inlet valve isclosed during unloading, which creates an internalvacuum. This method is seldom used in modern compressorsystems.

C. NOISE LEVELS

Air Compressors generate noise. Impaired hearing is aconcern of every industrial worker and prolonged exposureto certain levels of noise may cause permanent damage.The Occupational Safety and Health Act (0.S.H.A.)

identifies permissible noise levels in the chart below.

PERMISSIBLE NOISE EXPOSUREDuration per Sound level

Dav, Hours8

6

4

3

2

1 1/21

1/21 4

dBA90929597100102105110115

IIIMIIMMMON11

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Compressed air system sound may have many differentsources. The following are factors which may increase thenoise levels near compressors: the position of thecompressor in the room (i.e. against a wall), the soundcharacteristics of the room, items in the room that mayabsorb or reflect sound, and the location of thecompressor inlet.

D. COMPRESSOR VENTILATION

The amount of ventilation needed will depend on the typeof compressor installed. The compressor or housing areashould be well ventilated to prevent overheating ofcomponents and to prolong the life of the compressor.Good ventilation will also curb excess energy consumption.For proper ventilation, air should be pulled from lowpoints and exhausted at opposing high pointc. This willprevent interference with compressor operation andworkers.

E. COMPRESSOR INSTALLATION

Compressors should be placed close to where they will beused, so that pressure drops are lower and versatility ofthe compressor is increased. When installing acompressor, intake air should be cool, dry, and drawn froma clean external source. The intake duct should have aflow area that is larger than the piston area. This willallow smooth air flow to the compressor. Additionally,the intake air should be filtered to help preventcontaminants from being introduced into the system. Airfilters should be serviced regularly so they maintaintheir qualities to prevent dirt and other particulatematter from entering the compressor.

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oUESTIONS -- COMPRESSORS

Select the best answer for the following:

1. Redial and axial are the two basic groups of compressors.

T or F

2. The following are types of positive displacement compressors:

a. Centrifugal air compressorb. Reciprocating piston compressorc. Vane compressord. Both a and be. All of the above

3. The helical compressor is also referred to as a screwcompressor, and operates by the meshing of two rotors.

T or F

4. Impellers are:

a. Vanes on motorb. Housing partsc. Lobes of rotorsd. Pistons

5. The two types of dynamic compressors are:

a. Axle and vaneb. Radial and axialc. Axial and inletd. Helical and radial

6. Which of the following are methods of output control(unloading):

a. Inlet valve regulationb. Bypassc. Inlet throttlingd. Start-stop1. All of the above

7. Intake air should not be filtered to preverl contaminants fromentering the system with regards to installation.

T or F

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IV. AIR TREATMENT

In a pneumatic system, moisture presents the greatestthreat. Moisture is introduced to the system simultaneouslywith the air. The amount of moisture varies depending on theamount ot the relative humiditl 'n the air. As the air iscompressed, the moisture in the condenses. As theamount of air in the system incr es, so does the moisture.An after cooler is placed next to the system since warm airholds more mo1sture than cool air. The cooler air flowsthrough a separator, condensing and removing most of themoisture. In-line dryers and filters are then used tofurther remove moisture before the air enters the system.The air may also contain particulate matter that was notpicked up by the intake filter, and this must also beremoved. Complete treatment of compressed air includesdrying, refrigerating, aftercsJling, and filtering.

A. DRIERS

Three types of driers are used to remove moisture;absorption driers, adsorption driers, and low-temperaturedriers.

1

Outlet

.---

--...64............./...A.,0%...._,...,--" -

Inlet

..............-....^....^...."""4"""..,.......

............,..."

,..__,....

=0. Drain

1. Absorption dryingAbsorption drying is achemical process in whichair flows through acontainer which contains adrying agent. The airflows in at the bottomthrough a hemical agent inthe middle, and outthrough the top.

Figure 11 AbsorptionDrier

ndensedMoisture

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The drying agent will also filter out oils and oil vapors.Therefore, an intake oil filter must be installed on theintake to the absorption dryer to extend the life of thechemical.

2. Adsorption dryingAdsorption drying is a physical process in which a dryingagent collects or adsorbs water on its surfaces, Thedrying agent eventually becomes saturated with water.Hot air can be pumped through the dryer and vented to theroom atmosphere. This process then removes the moisturefrom the drying agent and the agent may be used again.

Figure 12 - Adsorption Drier

ConpressedAir Outlet

CanpressedAir Inlet

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3. Low temperature dryingLow temperature drying is a mechanical method of removingmoisture. First the air is moved through an air/air heatexchanger and through a separator to remove water. The

-- air is then passed through a refrigeration process tocool the air to its dew point. More moisture iscondensed and run through a second separator where morewater is removed. Finally, the compressed air is runback through the air/air heat exchanger and out to thesystem.

Air Outlet

Air

Inlet

di' ,, /pill

Dry Compressed Air

/

.1.1

1// ////,/////

ilI

4:r/air heat exchanger

1_

RefrigeratingMachine

Cooling agent/airheat exchanger

/

Cooling Agent

1.---:ti_Figure 13 - Low-temperature Drier

B. AFTERCOOLING

Aftercoolers are used frequently to cool air which hasbeen heated by the compression process. The aftercoolingprocess may be accomplished by passing coo2 water or air

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over an aftercooling chamber. Dirt and oil vapor fall outof suspension in this chamber and are removed with aseparator or filter.

C. FILTERS

1. Air Filt.rsAir filters removeairborne particulateand may also removewater from the air.Air flows downwardover a bafflesection which startsa swirling motion inthe bowl and throwsthe particles out ofthe air. A secondbaffle collects theparticulate under itwhile deflecting airupwards towards aporous type filteron its way out. Adraw plug at thebottom of the filtermay be used tomanually removewater or it may alsobe removedautomatically.Another type of airfilter contains afilter bowl andporous filter. Inthis type, the airis driven throughthe walls of thefilter and to theoutlet of the filterhousing.

Filter

BafflePlate

Drain

Figure 14 Manual drain air filter2. Dry Filters

Dry filters are made in many different shapes and sizes.Most of these filters have e cotton or felt insert packedinto a wire screen or other open container. The packedmaterials can be cleaned with a recommended solvent anddried with compressed air. Most can be cleaned bycompressed air, or can be washed with a mild detergentand dried. Many are simply replaced with new elements.

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D. RECEIVER TANK

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After the air has gone through the aftercooler and/ordryer, it is piped to a receiver or storage tank. Thereceiver tank stores the clean and compresed air. Thereceiver tank must have a drain at its lowest point sothat contaminants can be expelled periodically.

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QUESTIONS -- AIR TREATMENT

Select the best answer for the following:

1. What presents the greatest threat in a pneumatic system?

a. Heatb. Moisturec. Cold aird. None of the above

2. The three types of driers used to remove moisture are:

a. Absorption, adsorption, high temperatureb. Low temperature, porous, hand-heldc. After cooler, high temperature, in-lined. Adsorption, absorption, low temperature

3. is a physical process in which a drying agent_collects water on the surface.

a. High temperature dryingb. Low temperature dryingc. Adsorption dryingd. Absorption drying

4. cools air to its dew poi.nt, causing water vaporto condense.

a. Filteringb. Freezingc. Aftercoolingd. Refrigeration

5. A/an is designed to remove particulate matterand also water from air.

a. Adsorption filterb. Air filterc. Refrigeration coild. Oil filter

31

V. PNEUMATIC PIPING SYSTEMS

After air is compressed, conditioned, and stored in areceiver tank, it is then ready for the piping system.

A. TYPES OF PIPE

There are several types of pipe available for use inpneumatic systems. The two types to be discussed areplastic and copper pipe.

1. Plastic PipePlastic pipe is also known as PVC (polyvinyl chloride)This is a rigid pipe which is noncorrosive, possesseshigh tensile and impact strength, has good weatheringcharacteristics, is lightweight with low flow-resistance Its joints can be made quickly and easily,often becoming stronger than the pipe itself, and itdoes not support combustion. Plastic pipe is alsoinexpensive to install.

2. Copper PipeCopper pipe possesses the same design and installationrequirements as PVC piping systems. The differencelies in the way the pipes are joined, as well as thecost compared to plastic pipe.

B. PIPE SYSTEMS

1. Grid systemThis is also known as the dead end system, and is thesimplest of the piping systems. Its construction issimple, consisting of small feeder lines running off ofa central main. This allows only one flow path to beavailable, which may result in work stations near theend of the system receiving a deficient air supply whenthe demand of previous work stations is high.

11

Figure 15-Dead EndPiping System

32

2. Decentralized systemThis is also known as the unit system, and consistsof two or more grid systems with their own compressors.Individual grid units can be connected to provide amore centralized air flow. Additionally, decentralizedsystems can easily aclapt to changing systemrequirements.

-11-11-61

J 1

Figure 16 - Decentralized Piping System

3. Loop systemThis system allows for optimum conductor pipe size andensures equal air distribution throughout the system.This system also provides a narallel path to systemcomponents. The loop system is recommended over othersystems.

Figure 17 -Loop PipingSystem

33

C. JOINT TYPES

The procedures for joining pipes will differ depending onwhether plastic o/ copper pipes are to be joined.Solvents, cements, and compounds must be compatible withthe type of pipe being used. Plastic pipe requiressolvent for assembly of joints, while copper pipe doesnot.

1. Joining Plastic PipeTo join plastic pipe to a fitting, the pipe should becut square and ridges smoothed with the end of the pipeslightly rounded. Pipe and fittings should be free ofdirt, oil, grease, and other contaminants before theyare joined. Solvent cement must then be applied to thesurfaces of the pipe and the fitting to be joined.When the surfaces are softened, the pipe is insertedinto tise fitting. Once joined, the surfaces hardenagain and are welded into one piece. The jointbecomes stronger than the pipe or the fitting.

2. Joining Copper PipeThe methods of joining copper pipe are different fromthose of joining plastic pipe. These are three methodsused to join copper pipe:

a. Compression jointThis is the simplest of the three methods of joiningccpper pipe. The tubing is cut and rough edges areremoved using a pipe reamer and file. Acompression nut is placed over the end of the tubingso that the threads face the juint. Then acompression ring is installed over the tubing,placed into the fitting and tightened snugly. Do notovertighten, as this promotes leaks and restrictsair flow.

b. Flared jointThe tubing is cut and burrs are removed in the samemanner as the compression joint. A special flaringtool is used to flare the pipe end so that it willfit the joint and hold the pipe in place. Thetubing nut must be tightened securely.

c. Soldered jointSoldering is a method of joining pipe through theuse of an intermetallic bonding (soldering). Thepipe is cut and all burrs removed. All surfacesmust then be thoroughly cleaned to accomplishsoldering properly. Cleaning may be accomplishedeasily Wth steel wool, fine grit emery paper, or a

3E,

34

steel brush. After the pipe and joint are cleaned, aflux is used on both the fitting and the pipe beforethey are joined. The use of a flux achieves twopurposes: it removes oxidation and aids in the flowof molten solder. Once the tubing and fitting isassembled, heat is applied with solder to the joint.Lastly, solder is applied to the joint until a ringof solder appears at the and of the fitting. Excesssolder should be wiped off with a wet cloth orsponge before it cools.

D. INSTALLATION REQUIREMENTS

Attention should be paid to minimize the number offittings in a system, and also hold bending of pipe to aminimum. Smooth tubing is preferred over pipe as itprovides a constant flow and minimizes decreases inpressure. Pipe fittings cause several times the pressureloss as an equivalent 90 degree bend in tu5ing. The tubingalso gives greater flexibility and the reduction in thenumber of fittings required, thus reducing the number ofleaks possible. Distribution lines should be at a slightslope (up to 1/4" per foot) so that water will sweep intodrains throughout the system. Drop lines should come fromthe top of the main. This minimizes the travel of dirtand water down the drop line. At the bottom of the droplines drains should be provided fur water removal.

E. AIR LEAKS

Checking the piping system for air leaks is important on aconstant maintenance routine. The fewer the leaks, thebetter the performance of tools and equipment. Air leaksalso waste compressor energy and increase electrical costsdue to the running of the compressor to make up for theloss of air. Both air flow and pressure that are availableto tools are lowered when there ar,..: leaks in the airsystem.

The following is a list of procedures used to check for airleaks:

1. Most air leaks are audible and can be heard while thesystem is in operation. One should check for air leakswhen noise from operating machinery is at a minimum,such as during scheduled shift changes or other timeswhen plant machinery is not operating.

2. blapy solutions or leak detection fluids can beutilized by applying the Eluid to the connection andwatching for bubbles of air.

37

35

3. An air leak may be detected by pressuring the system tosee how long it holds its pressure before thecompressor turns on to compensate for its loss. Oneshould shut the system down completely to determine howlong it will take for the system to drop to a minimumpressure.

38

36

QUESTIONS -- PIPING

Select the best answer for the following:

1. Which of the following pneumatic piping systems is thesimplest?

a. Decentralized systemb. Grid systemc. Unit systemd. Loop system

2. Which of the following pneumatic piping systems is recommendedover the others?

a. Unit systemb. Dead end systemc. Loop systemd. Centralized system

3. Which of the following are methods to check for air leaks?

a. Using leak detection fluidsb. Listening for leaksc. Pressurize the system and monitor system pressured. All of the above

4. Which of the following are copper joint types?

a. Squared jointb. Flared jointc. Compression jointd. Soldered jointe. b, c, and d

5. The use of removes oxidation and aids in theflow of molten solder when joining pipes.

a. Compression ringb. Fluoridec. Fluxd. Coolant

3 9

1

37

VI. PNEUMATIC VALVES

Valves regulate the operation of pneumatic systems. Theyregulate pressure throughout the system, direct air to itsproper circuits, and moderate the volume of air each circuitreceives and uses. There are two main categories ofpneumatic valves: pressure control valves and directionalcontrol valves. These two categories have many types ofvalves in them. Their functions and operations follow.

A. PRESSURE CONTROL VALVES

These types of valves limit pressure within the pneumaticsystem, unload excess pressure when required, and controlthe pressure at which air enters circuits. The followingare types of pressure control valves:

1. Relief valvesThese valves are used to protect the pneumatic systemwhen extreme amounts of pressure develop. Relief valveseach possess a valve body, a valve seat, and a springwith calibrated tension.

While the system remainsunder the calibrated tensionof the spring, the valvewill not open. Once thepressure increases over thetension of the spring, thespring will compress and thevalve will open, ventingthe amount of air into theatmosphere until thepressure is relieved to asafe operating level. Oncethis occurs, the spring willreset itself and the valvewill close. Mechanicaladjustment screws can alsobe utilized to obtain properpressure relief settings onrelief valves. When largevolumes of air are beingutilized, a pilot-operatedrelief valve maybe used toregulate the amount of pressurethat affects the relief valve.The pilot valve opens andcloses at different pressuresproviding a set range ofpressure that is furtherregulated by the relief valva.

4 0

38

2. Reducina valvesReducing valves are required when the system delivershigh or fluctuating pressures.

From

MainCircuit \

/

\ \Figure 19 Pressure Reducing Valve

a. Constant Reduced Pressure ValveA constant reduced pressure valve always has thesame amount of pressure in the secondary circuit nomatter what the pressure reading is in the primarycircuit.

To SecondaryCircuit

39

b. Fixed Amount Reduction ValveA fixed-amount reduction valve operates bymaintaining a balance between the pressures of themain and secondary systems.

Figure 20 Fixed Amount Reduction Valve

Although the amount of pressure reduction from primarycircuit to secondary circuit will stay the same, when themain system pressure fluctuates, so will the secondarysystem pressure.

3. Directional Control ValvesThese types of valves are used to direct compressed airflow from one circuit or branch to another within apneuml:ic system. There are three types of directionalcontrol valves: check valves, rotary valves, and spoolvalves.

4 2

a. Check valvesCheck valves only allow air flow in one direction.Air flowing in one direction opens the valve andallows it to free flow through the valve. Airflowing in the opposite direction closes the valveand prevents airflow.

Body

Outlet

Or

40

InletPort

ZSpring

Figure 21 - Check Valve

b. Rotary valvesRotary valves are finelymatched cylinders that fitinto housing ports so thatwork can be accomplished.Cylinder holes are alignedso that air is transferred "to and from the actuator.This procedure may becontrolled mechanicallyor manually.

Figure 22 - Rotary Valve

43

41

c. Spool valvesSpool valves are frequently used to regulate allaspects of the system. These valves are easilyadaptable and compact, wh1.7.h make them moredesirable for use in pneumatic systems than other ttypes of valves. Spool valves can be adapted fordifferent functions by adding ports and lands.Directional valves may be classified by means oftheir flow paths utilized to operate the pneumaticsystem. Items to be considered in this type ofclassification include the number of individualports, the number of flow paths the valves aredesigned for, and the internal connection of theports with the movable part. Valves included inthis type of classification are two-way, three-way,and four-way directional valves.

d.Two-way directional valveA two-way directional valve consists of two portsdirectly connected to one another internally that canbe both connected and disconnected.

\ Passage

Figure 23 Two-Way Valve (Open)

,1 4

42

A two-way directional valve may function as an on-off

valve, bscause of its ability to restrict the flow path

between the two ports.

Figure 24 - Two-way valve (closed)

e. Three-way directional valve

A three-way directional valve consists of three

ports connected to each other internally.

Actuator Spool

Passage

Pressure PassageFigure 25 3-way valve

\ TankExhaust Passage

This valve functions to both pressurize and exhaust

one actuator port. The valve will connect and

disconnect both the air flow and the exhaust from

the actuator being utilized.

43

Figure 26 - 3-Way Valve - Exhaust Position

SchcmaricSymbol

f. Four-way directional valveA four-way directional valve consists of onepressure port, two actuator ports, and one ormore exhaust ports.

Figure 27 - 4-Ported, 4-Way ValveRm3sage A j Passage B

schematic symbols

These valves have four flow paths within the valveitself, and are perhaps the most common of thedirectional valves.

44

g. Valve 0 eration and ControlPneumatic valves may be constructed to operatemanually, mechanically, or automatically.

h. Manually Operated ValvesManually operated valves are usually two-way valves.Manual operation may be achieved using a variety ofmanually operated dwces including push buttons,levers, and foot pedals.

Figure 28 - Manually operated Valve Symbols

i. Automatically Operated ValvesThese valves can be of several types, with the mostcommon being electrically operated by the use of asolenoid. These valves may also be operated eitherpneumatically or hydraulically. In addition, avacuum operated valve may be used in some instances.

1

Figure 29 - Automatically Operated Valve Symbols

4 '7

45

j. Solenoid valvesDirect-acting solenoid valves possess a plungerwhich is held against the valve seat, thusrestricting the air flow, when the solenoid coil isdeenergized. When the coil is energized, theplunger shifts the valve spool activating thepneumatic circuit.

Figure 30 - Solenoid Activated Valve

48

I

46

k. Pilot actuated valvesPilot actuated valves may use air pressure tocontrol the movement of the valve spool. Speed ofthe shift in spool position may be controlled by theamount of pressure in the pilot circuit. The pilotcircuit may receive its air supply from within thevalve itself (internally piloted valve) or from anexternal air circuit. A simple externally pilotedvalve is shown in Figure 34.

Figure 31 - Externally Piloted Valve

4 9

QUESTIONS VALVES

Select the best answer for the following:

1. The purposes of valves are:

a. Direct air to proper circuitsb. Moderate volume of air for circuitsc. Regulate pressure throughout the systemd. All of the abovee. None of the above

2. Types of pressura control valves include:

a. Spool valvesb. Constant reduced pressure valvesc. Relief valvesd. Both b and ce. All of the above

3. What type of valve only allcws air flow in one direction?

a. Rotary valveb. Reduction valvec. Check valved. Main valvee. Czech valve

4. ValveL may be activated by various methods including:

a. Manualb. Electrical solenoidc. Pneumatic pilot circuitd. All of the above

50

47

AL Intakeand

Discharge

49

There are two types of single-acting cylindertypes.

a. Diaphragm cylinderin this cylinder, a diaphragm replaces the shaft andseal of the single-acting cylinder. PressureunAerneath the diaphragm will cause the diaphragmand the piston to rise and descend. This cylinderis ideal for use when only small piston movement isrequired.

Figure 33 - Diaphragm Cylinder

b. Rolling diaphragm zylinderThis cylinder uses the same technique as in thediaphragm, but the diaphragm is rolled up and islocated between the piston and the air chamber. Asthe piston moves outward, the diaphragm unrolls,thus giving the cylinder a larger stroke than thetypical single-acting cylinder.

Figure 34 - Rolling Diaphragm Cylinder

52

Air Intakeand

Discharge

50

2. Double-acting cylindersThese cylinders can apply force in two directions. Airpressure is supplied into one side and extends thepiston. The air flows outward and expends itself from theport on the opposite end into the atmosphere. Once thestroke has been completed, the direction of movement maybe reversed by applying air pressure to the opposite endand reversing the process.

PoAir Intake

Air rtPiston

and PistoDischarge Seals Pisban

AWAWWIEIIIRod

C/1 \

IL11101WWM110111

Figure 35 - Double-Acting Cylinder

There is one type of double-acting cylinder.

Rod Seal

a. Vane cylindersThese types of cylinders possess vanes which rotatefrom side to side, rather than in a back and forthmotion as the pistons previously mentioned.

Within the vane cylinder thereare two vanes. A fixed vane onthe cylinder wall forms a sealwith the rotating shaft, while asecond vane is attached to thecylinder shaft and forms a sealwith the inner cylinder surfaces.Air is admitted or dischargedthrough ports on each side of thecylinder. An arm may be attachedto the rotating vane when thecylinder is in operation toproduce either a clockwise orcounterclockwise motion.

Figure 36 - Vane in Vane Cylinder

5 3

51

B. CYLINDER MOUNTING STYLES

Cylinders are mounted in numerous and varied ways. Thereare three primary mounting techniques.

1. Fixed centerline mountingWith this type of mounting, the centerline of thecylinder absorbs force. Flanges and tie rods mounted onthe end of the cylinder or centerline lug mounts areused to mount the cylinder. Fixed centerline mountingprevents bending stress from developing in both themounting framework and the cylinder. This type ofmounting is recommended for cylinders with long strokesand heavy-duty applications.

2. Fixed noncenterline mountingThis type of mounting does not provide for absorption offorce on the centerline of the cylinder, instead theforce is transmitted through the cylinder in anoffcenter manner. To mount the cylinder, side lugs orfeet, and side-tapped holes are utilized.

3. Pivoted cylinder mountingsThese mountings can effectively absorb force on thecenterline of the cylinder. A pivot type of mountingis utilized when the cylinder must be free to rotateand maintain accurate alignment between the cylinderand the connecting component. The rod-end connectionmust be mounted to a pivot to prevent the piston rod'-om binding or bending. The pivoted cylinder mountingsare ',ossified as trunnion or clevis mountings, andmust be lubricated to work effectively and efficiently.

54

1

1

1

1

1

1

I

1111

52

QUESTIONS CYLINDERS

Select the best answer for the following:

1. The three cylinder mounting styles are:

a. Fixed noncenterline mountingb. Pilot mountingc. Fixed centerline mountingd. Pivot mountinge. a, b, and d

2. Which of the following utilizes a single port to both receiveand discharge air from the cylinder?

a. Single-acting protb. Double-acting cylinderc. SingleIcting cylinderd. None o. the above

3. Vane cylinders can apply force in two directions.

T or F

4. Amotion.

cylinder does not have a back and forth

a. Double-actingb. Diaphragmc. Single-actingd. Vane

5. The (lower/higher) the pressure, the greater the force appliedto an object.

55

53

VIII. MISCELLANEOUS VALVES/AIR LOGIC AND DIAGRAMS

A. QUICK EXHAUST VALVES

These valves are used with three or four wav controlvalves to increase exhaust to control cyiinder speed.

B. SILENCERS OR MUFFLERS

Due to exhausting air and the noise factors involved withpncumatic systems, silencers or mufflers are used to meet

OSHA noise requirements.

C. AIR BOOSTERS

There are two types of air boosters, air to air andair to oil. Both will increase pressure to desired

level above system pressure.

r>

I--

Figure 37 - Air to Oil Booster

56

D. AIR LOGIC SYMBOLS

1. Compressor

2. Electric Motor

r-N\

54

8. Pilot Line

9. Crossed Lines

H X

10. Joining Lines

3. Filter

1

4. Flow Control Valve 11. Check Valve

5. Pressure Gage

6. Air Receiver

12. Bidirectional Motor

13. Unidirectional Motor

7. Pressura Switch 14. Silencer

57

ACTUATING DEVICES SYMBOLS

1. Hand Lever

2. Solenoid

TIL

5. Push Button

6. Foot Pedal - Trottle

3. Pilot Pressure-Remote Supply 7. Manual

4. Pilot Pressure-Internal Supply 8. Spring

5 8

M M

55

CT)117.)

MI ION UM I= NM WM IMIII I= INI OM IMIONOMMI MN MI

F. SCHEMATIC DIAGRAMS

Schematic Diagrams for Air Logic are drawn to helpdesigners and technicians to change, locate and identifyaspects of a working pneumatic system.

AdvanceA/0 Tarik

(Closed)Balancing Valve

11

57

Intensifier

Figure 38 Schematic Diagram

60

WbrkCylinder

ReturnA/0 Tank

58

ANSWERS TO QUESTIONS-PNEUMATICS

INTRODUCTION CYLINDERS

1. C 1. E

2. B 2. C

3. B 3. FALSE4. A 4. D

5. D 5. HIGHER

SAFETY

1. C2. D3. A4. B5. D

COMPRESSORS

1. FALSE2. B3. TRUE4. C5. B6. E7. FALSE

AIR TREATMENT

1. B2. D3. C4. D5. B

PIPING SYSTEMS

1. B2. C3. D4. E5. C

VALVES

1. D2. E3. C4. A

ENDU.S. Dept. of Education

0;fice of EducationalResearch and Improvement (OERO

ERICDate Filmed

July 24, 1991