Download - API 2201 (Ed. 1995) Welding or Hot Tapping on Equipment in Service

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Procedures for Welding or HotTapping on Equipment in Service

API RECOMMENDED PRACTICE 2201FOURTH EDITION, SEPTEMBER 1995

STEP

One of the most significant long-term trends affecting the future vitality of the petroleumindustry is the publicÕs concerns about the environment. Recognizing this trend, APImember companies have developed a positive, forward looking strategy called STEP:Strategies for TodayÕs Environmental Partnership. This program aims to address publicconcerns by improving industryÕs environmental, health and safety performance; docu-menting performance improvements; and communicating them to the public. The founda-tion of STEP is the API Environmental Mission and Guiding Environmental Principles.API standards, by promoting the use of sound engineering and operational practices, are animportant means of implementing APIÕs STEP program.

API ENVIRONMENTAL MISSION AND GUIDINGENVIRONMENTAL PRINCIPLES

The members of the American Petroleum Institute are dedicated to continuous efforts toimprove the compatibility of our operations with the environment while economicallydeveloping energy resources and supplying high quality products and services toconsumers. The members recognize the importance of efficiently meeting societyÕs needsand our responsibility to work with the public, the government, and others to develop andto use natural resources in an environmentally sound manner while protecting the healthand safety of our employees and the public. To meet these responsibilities, API memberspledge to manage our businesses according to these principles:

● To recognize and to respond to community concerns about our raw materials, prod-ucts and operations.

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Procedures for Welding or Hot Tapping on Equipment in Service

Health and Environmental Affairs Department

API RECOMMENDED PRACTICE 2201FOURTH EDITION, SEPTEMBER 1995

ii

SPECIAL NOTES

1. API PUBLICATIONS NECESSARILY ADDRESS PROBLEMS OF A GENERALNATURE. WITH RESPECT TO PARTICULAR CIRCUMSTANCES, LOCAL, STATE,AND FEDERAL LAWS AND REGULATIONS SHOULD BE REVIEWED.

2. API IS NOT UNDERTAKING TO MEET THE DUTIES OF EMPLOYERS, MANU-FACTURERS, OR SUPPLIERS TO WARN AND PROPERLY TRAIN AND EQUIPTHEIR EMPLOYEES, AND OTHERS EXPOSED, CONCERNING HEALTH ANDSAFETY RISKS AND PRECAUTIONS, NOR UNDERTAKING THEIR OBLIGATIONSUNDER LOCAL, STATE, OR FEDERAL LAWS.

3. INFORMATION CONCERNING SAFETY AND HEALTH RISKS AND PROPERPRECAUTIONS WITH RESPECT TO PARTICULAR MATERIALS AND CONDI-TIONS SHOULD BE OBTAINED FROM THE EMPLOYER, THE MANUFACTUREROR SUPPLIER OF THAT MATERIAL, OR THE MATERIAL SAFETY DATA SHEET.

4. NOTHING CONTAINED IN ANY API PUBLICATION IS TO BE CONSTRUED ASGRANTING ANY RIGHT, BY IMPLICATION OR OTHERWISE, FOR THE MANU-FACTURE, SALE, OR USE OF ANY METHOD, APPARATUS, OR PRODUCTCOVERED BY LETTERS PATENT. NEITHER SHOULD ANYTHING CONTAINEDIN THE PUBLICATION BE CONSTRUED AS INSURING ANYONE AGAINSTLIABILITY FOR INFRINGEMENT OF LETTERS PATENT.

5. GENERALLY, API STANDARDS ARE REVIEWED AND REVISED, REAF-FIRMED, OR WITHDRAWN AT LEAST EVERY FIVE YEARS. SOMETIMES A ONE-TIME EXTENSION OF UP TO TWO YEARS WILL BE ADDED TO THIS REVIEWCYCLE. THIS PUBLICATION WILL NO LONGER BE IN EFFECT FIVE YEARSAFTER ITS PUBLICATION DATE AS AN OPERATIVE API STANDARD OR,WHERE AN EXTENSION HAS BEEN GRANTED, UPON REPUBLICATION. THESTATUS OF THE PUBLICATION CAN BE ASCERTAINED FROM THE APIAUTHORING DEPARTMENT [TELEPHONE (202) 682-8000]. A CATALOG OF APIPUBLICATIONS AND MATERIALS IS PUBLISHED ANNUALLY AND UPDATEDQUARTERLY BY API, 1220 L STREET, N.W., WASHINGTON, D.C. 20005.

Copyright © 1995 American Petroleum Institute

All rights reserved. No part of this work may be reproduced, stored in a retrieval system,or transmitted by any means, electronic, mechanical, photocopying, recording, or other-

wise, without prior written permission from the publisher. Contact API PublicationsManager,1220 L Street, N.W.,Washington, DC 20005.

iii

FOREWORD

This publication is designed to provide a better understanding of the problems andhazards encountered when welding or installing hot tap connections on piping, vessels ortanks containing flammable or combustible liquids or gases. The essential elements of thispublication are based on accumulated knowledge and experience of the petroleum industry,current industry safe operating practices, and existing consensus standards. The practicesdescribed in this publication are designed to protect the safety of personnel and the facilitiesfor the work involved. It shall be noted, however, that special problems beyond the scopeof this publication are possible. Also, federal, state and local regulations or laws maycontain additional requirements that must be taken into account when a hot tap program isdeveloped for a specific facility.

This publication was prepared under the direction of a support group comprised ofmembers of the API Safety and Fire Protection Subcommittee. This document wasproduced under API standardization procedures that ensure appropriate notification andparticipation in the developmental process and is designated as an API recommended prac-tice. Questions concerning the interpretation of the content of this recommended practiceor comments and questions concerning the procedures under which this recommendedpractice was developed should be directed in writing to the API Safety and Fire ProtectionSubcommittee.

API publications may be used by anyone desiring to do so. Every effort has been madeby the Institute to assure the accuracy and reliability of the data contained in them; however,the Institute makes no representation, warranty or guarantee in connection with this publi-cation and hereby expressly disclaims any liability or responsibility for loss or damageresulting from its use or for the violation of any federal, state, or municipal regulation withwhich this publication may conflict.

Suggested revisions are invited and should be submitted to the director of the Health andEnvironmental Affairs Department, American Petroleum Institute, 1220 L Street, N.W.,Washington, DC 20005.

v

CONTENTS

Page

SECTION 1ÑGENERAL ........................................................................ 11.1 Scope........................................................................................................................ 11.2 Referenced Publications........................................................................................... 11.3 Lockout/Tagout Requirements................................................................................. 1

SECTION 2ÑHOT TAPPING MACHINES............................................ 22.1 General..................................................................................................................... 22.2 Hot Tapping Machine Considerations ..................................................................... 2

SECTION 3ÑHOT TAP AND WELDING METALLURGY AND DESIGN................................................................... 2

3.1 General..................................................................................................................... 23.2 Burn-Through Prevention ........................................................................................ 23.3 Flow in Lines ........................................................................................................... 23.4 Metal Thickness ....................................................................................................... 43.5 Fittings ..................................................................................................................... 43.6 Post Weld Heat Treatment (PWHT) ........................................................................ 43.7 Metal Temperature ................................................................................................... 43.8 Hot Tap Connection and Welding Design................................................................ 43.9 Piping and Equipment Contents............................................................................... 4

SECTION 4ÑPREPARATIONS .............................................................. 54.1 Written Plans............................................................................................................ 54.2 Process Hazard Management................................................................................... 54.3 Personnel Qualifications .......................................................................................... 54.4 Toxicity Considerations ........................................................................................... 5

SECTION 5ÑSPECIAL CONDITIONS.................................................. 65.1 Hot Tapping or Welding on Tanks in Service .......................................................... 65.2 Hot Tapping or Welding on the Decks of Floating Roof Tanks............................... 65.3 Hot Tapping or Welding Above or Below Grade .................................................... 65.4 Hot Tapping or Welding on Lined Piping or Lined

Equipment or Cased Lines ....................................................................................... 65.5 Hot Tapping Upstream of Equipment and Valves.................................................... 6

SECTION 6ÑPROCEDURES ................................................................. 76.1 Preliminary Procedures............................................................................................ 76.2 Welding .................................................................................................................... 76.3 Inspecting the Weld.................................................................................................. 76.4 Installing the Hot Tapping Machine ........................................................................ 76.5 Testing the Weld and Hot Tapping Machine............................................................ 76.6 Completion............................................................................................................... 7

APPENDIX AÑSUGGESTED HOT TAP CHECKLIST............................................... 9

Figure1ÑHot Tapping Machine.............................................................................................. 3

1.1 ScopeThis publication covers the safety aspects to be considered

when hot tapping, or when welding without hot tapping onin-service piping or equipment. It is not a substitute for jobplanning. A detailed, written procedure for hot tapping andwelding should be prepared or reviewed before starting eachjob to ensure that all proper steps are taken. These proce-dures may need to be revised in response to unique problemsor situations that may arise concerning the safety ofpersonnel and facilities.

The hot tap and welding procedures described in thispublication apply to piping and equipment fabricated fromferritic and austenitic steel. Other materials, such asaluminum, copper, plastic, and cast iron may require specialhot tap or welding procedures.

Hot tapping is the technique of attaching a mechanical orwelded branch fitting to piping or equipment in service, andcreating an opening in that piping or equipment by drilling orcutting a portion of the piping or equipment within theattached fitting. Hot tapping is usually performed when it isnot feasible, or it is impractical, to take the equipment orpiping out of service, or to purge or clean it by conventionalmethods. A hot tap connection can often be safely madewithout interfering with the process operation.

1.2 Referenced PublicationsThe latest editions of the following documents are refer-

enced in this publication:

ACGIH1

Threshold Limit Values for Chemical Substances andPhysical Agents In the Work Environment andBiological Exposure Indices (and documentsreferenced therein)

ANSI2

Z.88.2 Practices for Respiratory Protection

APIStd 510 Pressure Vessel Inspection Code: Maintenance

Inspection, Rating, Repair, and AlterationStd 570 Piping Inspection Code: Inspection, Repair,

Alteration, and Rerating of In-Service PipingSystems

Std 598 Valve Inspection and Testing

Std 650 Welded Steel Tanks for Oil StorageStd 653 Tank Inspection, Repair, Alteration, and Recon-

structionPubl 941 Steels for Hydrogen Service at Elevated

Temperatures and Pressures in PetroleumRefineries and Petrochemical Plants

RP 1107 Pipeline Maintenance Welding PracticesPubl 2009 Safe Welding and Cutting Practices in

Refineries, Gasoline Plants, and PetrochemicalPlants

Battelle Institute3

Investigation and Prediction of Cooling Rates DuringPipeline Maintenance Welding and BattelleÕsHot Tap Thermal Analysis Models

ASME4

Boiler and Pressure Vessel Code; Section VIII, ÒPressureVesselsÓ and Section IX, ÒWelding QualificationsÓ

ASME/ANSI2

B31.3 Chemical Plant and Petroleum Refinery PipingB31.4 Liquid Transportation Systems for Hydrocar-

bons, LPG, etc.B31.8 Gas Transmission Pipelines

DOT5

49 Code of Federal Regulations Parts 190-199

OSHA6

29 Code of Federal Regulations Part 191029 Code of Federal Regulations Parts 1926.351 and 352,

(relative to welding on gas pipelines)

1.3 Lockout /Tagout RequirementsA decision to weld on equipment in service or to perform

a hot tap should be made only after careful consideration ofthe alternatives. The OSHA lockout/tagout regulation, 29CFR 1910.147 (a) (2) (iii) (B), establishes that the standarddoes not apply to hot taps when the employer demonstratesthat (1) continuity of service is essential, (2) shutdown of thesystem is impractical, (3) documented procedures arefollowed, and (4) special equipment is used which willprovide effective protection for employees.

Procedures for Welding or Hot Tapping on Equipment in Service

SECTION 1—GENERAL

1

3Available from the American Petroleum Institute, Order Desk, 1220 LStreet, N.W., Washington DC 20005 (Order No. D12750).4American Society of Mechanical Engineers, 345 E 47th Street, New York,New York 10018.5Department of Transportation, U.S. Government Printing Office, Wash-ington, DC 20402.6Occupational Safety and Health Administration, U.S. Government PrintingOffice, Washington, DC 20402.

1American Conference of Governmental Industrial Hygienists, Building D-5, 6500 Glenway Avenue, Cincinnati, Ohio 45211.2American National Standards Institute, 1430 Broadway, New York, NewYork 10018.

2 API RECOMMENDED PRACTICE 2201

2.1 GeneralAlthough commercial hot tapping machines are available,

some companies prefer to build their own. Hot tappingmachines may be powered by hand, air, hydraulic fluid, orelectricity. These machines must be able to retain andremove the blank or coupon. The seals and materials ofconstruction of the hot tapping machine must be compatiblewith the contents in the piping or vessel. The material of thedrill or cutter must be suitable for effective penetration of themetal of the piping or vessel being tapped. Hot tappingmachines must be designed and constructed to withstand thetemperatures, pressures, and mechanical stress which may beimposed during their operation.

cracking problems. Special welding considerations may beneeded for high tensile strength steels to avoid weld crackingand the need for post weld heat treatment (PWHT).

3.2 Burn-Through PreventionTo avoid overheating and burn-through, the welding

procedure specifications should be based on experience inperforming welding operations on similar piping or equip-ment, and/or be based on heat transfer analysis. To minimizeburn through, the first weld pass to equipment or piping lessthan 1Ú4 inch (6.4 millimeter) thick should be made with a 3Ú32

inch (2.4 millimeter) or smaller diameter welding electrodeto limit heat input. (Note: the use of low heat input levels canincrease the risk of cracking in high carbon equivalent mate-rials). Subsequent passes should be made with a 1Ú8 inch (3.2millimeter) diameter electrode, or smaller if the metal thick-ness does not exceed 1Ú2 inch (12.8 millimeter).

For equipment and piping wall thicknesses greater than 1Ú2 inch (12.7 millimeter), where burn-through is not aprimary concern, larger diameter electrodes may be used.Where burn-through is of concern, care should be taken byavoiding the use of excessive welding current. In many situ-ations, the use of low hydrogen rods may be preferable toreduce the possibility of burn-through.

3.3 Flow in LinesFor metal thickness less than 1Ú4 inch (6.4 millimeters),

some flow during hot tapping minimizes the potential ofseveral undesirable conditions. Overheating liquids, burnthrough caused by elevated metal temperatures, and fluidthermal expansion in closed systems are less likely whenflow is maintained. However, higher flow increases the weld

2.2 Hot Tapping MachineConsiderations

Before hot tapping is attempted, the machine, cutter, andpilot bit should be carefully inspected to ensure that they arein satisfactory condition and capable of being left in service,if necessary, in the event of mechanical problems or hot tapvalve leakage. All hot tapping machines have maximum andminimum working pressure, and high and low temperatureratings. During hot tapping, consideration must be given tothe possibility of operational upsets which may alter theprocess temperature or pressure. It must also be rememberedthat the hot tapping machine may have to remain in place foran extended period of time if removal of the machine is notsuccessful (see Figure 1).

3.1 GeneralThe two primary concerns when welding on in-service

piping and equipment are burn through and cracking. Burn-through will occur if the unmelted area beneath the weldpool can no longer contain the pressure within the pipe orequipment. Weld cracking results when fast weld coolingrates produce a hard, crack-susceptible weld microstructure.Fast cooling rates can be caused by flowing contents insidethe piping and equipment which remove heat quickly.

Consideration should be given to evaluating heat transferduring welding to determine the heat input and relatedwelding variables in order to prevent overheating and burnthrough of the in-service piping or equipment. Also, consid-eration should be given to evaluating the expected coolingrate of the weld to determine the heat inputs required toproduce welds (and heat affected zones) which are free ofcracking. API and Battelle documents (see Section 1.2)contain information regarding these evaluations.

An engineering evaluation should be conducted before in-service welding is performed on materials which containlaminations or other imperfections. Vessels or lines to bewelded or hot tapped must also be inspected for adequatewall thickness and absence of imperfections. To minimizethe risk of burn through, the metal thickness should beadequate for the pressure (vacuum) and temperatureinvolved so that the hot tapping machine, equipment, andpersonnel can be safely supported.

A determination shall be made of the metal chemistry. Themetallurgy of the weld materials, the hot tap fitting, and theweld rod must be compatible with the metallurgy of theequipment to be welded or hot tapped. For example, lowhydrogen electrodes are often advisable to minimize weld

SECTION 2—HOT TAPPING MACHINES

SECTION 3—HOT TAP AND WELDING METALLURGY AND DESIGN

PROCEDURES FOR WELDING OR HOT TAPPING ON EQUIPMENT IN SERVICE 3

Tapping machine

Boring bar

Cutter holder

Cutter

AdapterPilot

Valve

Tapping fitting

Valve

Branch nipple

TYPICAL HOT TAP CONNECTION

Figure 1—Hot Tapping Machine


cooling rate and the risk of cracking. Therefore, whenwelding, it is desirable to provide some minimum level offlow while avoiding high flow rates. The need for aminimum level of flow is a trade-off between the need tominimize the risks of burn-through and cracking (see Section1.2, reference to Battelle Institute report).

For metal thickness between 1Ú4 inch (6.4 millimeters) and1Ú2 inch (12.8 millimeters), flow also increases the weldcooling rate and risk of cracking. Minimizing the flow ratereduces the risk of cracking and keeps the risk of burnthrough low. For metal thickness greater than 1Ú2 inch (12.8millimeters), the effect of flow on both weld cooling ratesand the risk of burn through is negligible.

Under certain conditions, such as when hot tapping orwelding on a flare line, there may be insufficient or inter-rupted flow that results in a flammable mixture during thewelding operation. In these circumstances it may be neces-sary to purge or flood the line with steam, inert gas, or hydro-carbon gas to prevent the formation of flammable mixtures.

3.4 Metal ThicknessThe piping or equipment base metal thickness must

provide support for the new connection and the hot tappingmachine. Alternately, reinforcing pads or auxiliary supportof the hot tapping machine may be provided. The basemetal must be free of laminations, hydrogen attack, or stresscorrosion cracking. Imperfections which might prevent asound weld from being made must be evaluated by acompetent person.

Minimum base thickness requirements shall be stated inthe written documentation for the job. A minimum basemetal thickness of 3Ú16 inch (4.8 millimeters) is recommendedfor most applications of welding and hot tapping. The actualminimum thickness is a function of the thickness requiredfor strength, plus a safety factor, usually 3Ú32 inch (2.4millimeters), to prevent burn through. Exceptions to therecommended thickness may be permitted when metallur-gical requirements and pressure (vacuum) limitations speci-fied by a qualified company specialist are met.

3.5 FittingsMany types of mechanical and welded fittings are avail-

able, such as welded outlet fittings, weld-ends, split tees,saddles, and nozzles. A qualified person shall select theproper fitting for the connection. Fittings must be properlysized to accommodate the hot tapping machine, to allow forfull depth of cutter penetration within the travel limits of themachine, and to allow for uninterrupted tapping valveclosure when the cutter and cut out coupon are retrieved.

3.6 Post Weld Heat Treatment (PWHT)Some equipment and piping is unsuitable for welding in

service, because the metallurgy or thickness of the metal

and/or the contents require PWHT which normally cannot bedone while the equipment or piping is pressurized. In suchcases, mechanically attached fittings should be considered.

3.7 Metal TemperatureConsider heating the weld area before welding if the metal

temperature is low enough (below the atmospheric dewpoint) so that moisture forms on the metal surface. Gener-ally, welding should not be performed on lines or equipmentwhen atmospheric temperature is less than -50ûF (-45ûC)unless special precautions, such as providing temporaryshelter, space heaters, and so forth, are taken.

Preheating may be required by the welding procedure toavoid cracking whenever the base metal has high carbonequivalency or high tensile strength.

3.8 Hot Tap Connection and WeldingDesign

Unless determined by an engineering review to be otherwiseacceptable, welding or hot tapping closer than 18 inches (46centimeters) to a flange or threaded connection, or approxi-mately 3 inches (7 centimeters) to a welded seam (including alongitudinal seam of welded piping) should be avoided. Assurethe connection is positioned so as to allow for the installation,operation, and removal of the hot tapping machine.

Hot tap connections and welding repairs and alterationsmust be designed to the applicable code (see Section 1.2)such as the following:

a. For piping designed to ASME B31.3, refer to API 570.b. For piping designed to ASME B31.4 and B 31.8, refer toASME/ANSI B31.4.c. For oil storage tanks constructed in accordance with APIStandard 650, refer to the hot tapping requirements in Stan-dard API 653.d. For Pressure Vessels built to Section VIII and the ASMEBoiler and Pressure Vessel Code, refer to API 510.

The design shall cover the specification of gaskets, valves,and bolts. Reinforcing pads or saddles shall be included inthe design when required by the applicable code.

3.9 Piping and Equipment ContentsCAUTION: Welding or hot tapping should not be performedon piping or equipment under vacuum (i.e: operating at lessthan atmospheric pressure) unless an engineering evaluationis conducted to determine safe operating procedures (seeAPI Publication 2009, Section 6.4). CAUTION: Welding and hot tapping should not be performedon piping or equipment containing the following materials:

a. Vapor/air or vapor/oxygen mixtures near or within theirflammable explosive range. The heat of welding may causea vapor mixture to enter the flammable range. b. Hydrogen, unless an appropriate engineering review has


been performed by a competent person who approveswelding on such equipment. Carbon and ferritic alloy steel issusceptible to high-temperature hydrogen attack duringprocess operations. Therefore, a review must be conductedto ensure that the equipment has been operated within theNelson curve for the particular steel involved.c. Peroxides, chlorine, or other chemicals likely to violentlydecompose or become hazardous from the heat of welding.d. Caustics, amines, and acids (such as HF acid), if theconcentrations and temperatures are such that the fabricationspecifications require PWHT. These services may causecracking in the weld area or heat affected zone.

training program provided by the manufacturer of the hottapping machine.

4.4 Toxicity ConsiderationsTests have indicated that prolonged or repeated exposure to

some petroleum liquids or vapors may be harmful. Identifymaterials in the area and contained in the piping or equipmentto be hot tapped or welded upon. Information concerninghealth risks associated with a particular substance should beobtained from the employer or the supplier of the material,typically from a Material Safety Data Sheet (MSDS). Addi-tional information may be obtained from governmental health,safety, and environmental agencies.

Toxic fumes may be generated from welding, in particularfrom welding on metals containing alloys of lead, zinc,cadmium, beryllium, and certain other metals. Some paints,particularly those containing lead, may also produce toxicfumes when heated or burned. Toxicity depends on thecomposition and quantity of fumes, which depends on thecomposition and quantity of the materials being welded. Thecomposition of the welding consumables, any coatings orpaints, the process used, and the circumstances and conditionof use will also affect toxicity.

Additional information on welding toxicity and appropriateprotective measures such as respirators may be obtained fromthe employer or by referring to the following documents listedin Section 1.2 of ACGIH Threshold Limit Values for ChemicalSubstances and Physical Agents in the Work Environment;OSHA 29 CFR 1910 Subpart Q (ÒWelding, Cutting andBrazingÓ) and Subpart Z (ÒToxic and Hazardous SubstancesÓ);and OSHA 29 CFR 1926 Subpart J (ÒWelding and CuttingÓ).

If potential for exposure is possible, provide appropriatecontrol measures, including the following:

a. Determine the level of exposure through measurementand/or analysis.b. Minimize skin contact and breathing of vapors or fumes

e. Certain unsaturated hydrocarbons (such as ethylene).These may experience exothermic decomposition due tohigh temperatures caused by welding, creating localized hotspots on piping or equipment walls that could lead to failure.f. Oxygen or oxygen enriched atmosphere. (Note: do not sayÒ23.5 percentÓ or any percentage at all. The amount ofoxygen needed for an enriched atmosphere varies with eachproductÕs flammable limits). The oxygen may cause a vapormixture to enter the flammable range and may affect the basemetal being welded.

g. Compressed air, unless known to be free of flammablesand combustibles, such as lubricating oil residues.

4.1 Written PlansPrior to conducting hot tapping or welding on piping or

equipment in service, a written plan should be preparedwhich includes the following:

a. Connection design.b. Hot tap procedure.c. Detailed written welding procedure (qualified in accor-dance with the applicable code) documenting heat input, asappropriate.d. Health, safety, fire protection, emergency response, andother appropriate procedures and instructions, includingowner and user requirements.

Additional information when developing a written plan maybe obtained from Section IX of the ASME Boiler and Pres-sure Vessel Code for qualification of welders and the funda-mental ASME Code welding procedures to be employed.

Note: Section IX does not cover the conditions encountered while weldingon in-service piping and equipment containing flammable and combustibleliquids. Refer to API Recommended Practice 1107 for qualification ofwelders and the welding procedures to be employed when welding on in-service flammable and combustible liquid piping.

4.2 Process Hazard ManagementConsideration shall be given to hazards that may be intro-

duced to the process system as the result of planned use ofthe hot tap connection. For further information on processsafety management requirements, refer to OSHA 29 CFR1910.119 (l).

4.3 Personnel QualificationsWelders must be qualified in accordance with the appli-

cable codes and specifications. They should be thoroughlyfamiliar with the welding equipment and hot tap and weldingprocedures to be used. Only skilled personnel should mountand assemble the hot tapping machine. These skills may beachieved either through on-the-job training or by a formal

SECTION 4—PREPARATIONS


through engineering or administrative controls, or byproviding appropriate personal protective equipment.c. Keep work areas clean and well ventilated; clean up spillspromptly.

5.3 Hot Tapping or Welding Above orBelow Grade

For hot tapping and welding above or below grade, provi-sions shall be made for an easily accessible means of egress.To assure that the atmosphere in excavations and confinedspaces is safe for entry and hot work, tests shall beconducted for oxygen, flammable vapors and toxic aircontaminants, and permit(s) issued listing the requirementsand approving the entry into the confined space and hotwork therein.

If oxygen deficiency, flammable vapors, or hazardous aircontaminants are present, an air mover or other positivemeans of ventilation shall be provided. Respiratory equip-ment may also be required to provide protection fromhazardous contaminants, vapors, or fumes emitted as a resultof welding. Air monitoring may also be required duringwork activity to assure that air quality remains within thepermitted safe work levels.

Refer to OSHA 29 CFR 1910 Subpart Q and 29 CFR 1926Subpart J for specific guidance concerning safe work withinconfined spaces.

5.4 Hot Tapping or Welding on LinedPiping or Lined Equipment or CasedLines

Hot tapping or welding should not be permitted on in-service lines or equipment with cladding, or with glass, lead,refractory, plastic, or strip linings, unless specifically autho-rized by specialized procedures or following an engineeringevaluation.

When hot tapping or welding on underground lines whichrun through casings, care must be taken to assure that theannular space is gas free and that the work is performed onthe pipeline and not on the casing.

5.5 Hot Tapping Upstream of Equipmentand Valves

Avoid hot tapping upstream of rotating equipment or auto-matic control valves, unless such equipment is protectedfrom the cuttings by filters or traps.

d. Use soap and water or approved cleaner to remove materialswhich contact skin. Do not use gasoline or similar solvents.e. Promptly remove and wash oil-soaked clothing, and do notuse oil soaked leather gloves, aprons, or other materials.

5.1 Hot Tapping or Welding on Tanks inService

The hazards associated with tank operations during hottapping or welding include, but are not limited to thefollowing:

a. Tank venting, with vapors reaching the exterior areawhere welding is taking place.b. Product within the tank rising and overflowing.c. Inadvertently allowing the liquid level within the tank tofall below the point of welding, thereby losing the heat sinkprovided by the liquid and exposing the vapor space withinthe tank to an ignition source.

Welding on the exterior of tanks in service shall not beconducted unless controls are established and in place toprevent flammable vapors from reaching the area ofwelding. Work must be stopped immediately shouldflammable vapors be detected in the welding area.

When hot tapping or welding on a tank in service, main-tain liquid in the tank at a level at least 3 feet (1 meter) abovethe area where the work is being performed. No attemptshould be made to hot tap or weld above this liquid level inatmospheric pressure petroleum storage tanks because of thepotential danger of an explosive atmosphere inside the tankvapor space. Measurements of the tank level should be madeby a hand tape gauge to verify the accuracy of automatic orremote reading gauges.

5.2 Hot Tapping or Welding on theDecks of Floating Roof Tanks

Welding should not be permitted on the decks of floatingroof tanks in service. Floating roof tanks are subject to uniqueflammability hazards in the following specific locations:

a. Inside the pontoons.b. Between the deck and liquid surface near the tank roofgauge float compartment.c. Near the roof seal vent.d. Near the floating roof lift leg vent.e. Between the primary and secondary seal.f. Near the roof drain.

SECTION 5—SPECIAL CONDITIONS


6.1 Preliminary ProceduresBefore proceeding with hot tapping or welding, the

following conditions shall be satisfied (see API Publication2009):

a. A competent person shall be present during the hottapping.b. The area where the connection is to be made has beenidentified and physically marked.c. The metal thickness has been verified and any metalimperfections that might prevent a proper weld have beenevaluated and approved by a competent person.d. A plan has been prepared to monitor and control processvariables within their required limits while hot tapping orwelding is being performed.e. All necessary testing for flammable vapors, oxygen, andhazardous air contaminants has been conducted to ensure asafe environment.f. Potential safety and health hazards have been assessed,personnel protective equipment provided, and fire retardantclothing used as necessary.g. Confined space entry and hot work permits have beenissued if the area in which the hot tapping or welding is to bedone requires such permits.h. A fire watch has been established and equipped with asuitable dry-chemical fire extinguisher or pressurized firehose.i. Signs and barriers have been provided when warranted toisolate the job site from the public and unauthorizedpersonnel.j. Procedures have been prepared and are in place to isolatethe work area in the event of an emergency.k. Personnel are trained and familiar with the hot tap orwelding procedures and the use and location of applicableequipment.

6.2 WeldingThe following requirements are applicable to the welding

operation:

a. Select and use a welding procedure which is qualified forthe specific application.b. Assure that the welder is qualified for the specified proce-dure.c. Assure that the fitting is positioned and supported beforewelding, so that misalignment of the hot tapping machinewill not occur.d. Protect the weld area during cleaning, preparation,welding, and weld inspection if blowing dirt, snow, or rain is present.

6.3 Inspecting the WeldInspect all attachment welds after welding. Dye penetrant,

ultrasonic, or magnetic particle inspection is recommendedbefore the hot tapping machine is installed. If these tests areused after the first weld pass, the weld area must be thor-oughly cleaned of any foreign material or residues. Theseprocedures should not be relied upon to replace the need forhydrostatic or pneumatic testing.

Note: if reinforcing is specified, the operator may wish to pressure test thenozzle prior to installing the reinforcing pad.

6.4 Installing the Hot Tapping MachineWhen installing the hot tapping machine follow the manu-

facturerÕs instructions and the following items:

a. The hot tap valve to be used must be of adequate size andrating, be of proper metallurgy, and be a full opening valve.It should be tested for seat leakage prior to installation (seeAPI 598).b. During installation the valve should be centered on thenozzle flange.c. Run the boring bar through the valve opening to be surethe cutter does not jam or drag.d. Carefully calculate the travel distance of the cutter toensure that the tap can be completed within the dimensionallimits, that the cut will be stopped before the cutter or pilotdrill touches the opposite side of the tapped pipe or equip-ment, and that the retrieved cut-out coupon can be retractedfar enough to allow unimpeded closure of the tapping valve.e. Confirm that the bleed-off valve will hold pressure and isnot plugged.f. Ensure that precautions have been established for safebleed off and disposal of material collected in the machineabove the hot tap valve.

6.5 Testing the Weld and Hot TappingMachine

The welded attachment and hot tapping machine shouldbe tested to assure they are in accordance with applicablecodes before the cutting is started, as follows:

a. Check tightness of bolts, packing, packing nuts, and anybypass line to avoid possible leakage.b. If the current temperature of the line or vessel will permit,conduct a hydrostatic test in accordance with the applicablecode. The temperature of the metal should be considered toprevent brittle fracture. The test pressure should be at leastequal to the operating pressure of the line or vessel to betapped. But it should not exceed the present internal pressureby more than approximately 10 percent, in order to avoidpossible internal collapse of the pipe or vessel wall.However, if prevailing conditions could cause collapse of the

SECTION 6—PROCEDURES


pipe or vessel walls, the test pressure may be reduced (seeAPI Standard 510 for pressure testing precautions).c. If the temperature is such that a hydrostatic test cannot beconducted, air or nitrogen with soap solution on the weld canbe used. At elevated temperatures, air should be used onlyafter a careful evaluation is made in order to avoid a poten-tial flammable mixture.

6.6 CompletionOnce work has started it should proceed without interrup-

tion until the hot tap has been completed and the valve closed.

a. It is often possible to know when the cut is complete by

the reduced resistance to hand cranking or when the drivemotor speeds up. b. The manufacturerÕs instructions should be followed whenretracting the bore and closing the valve. If the blank orcoupon is lost, no attempt should be made to retrieve it withthe hot tapping machine. If recovery of the blank or couponis necessary, it may require shutting down the equipment anddepressuring and opening the line.c. Provisions should be made to assure that adequate contain-ment is available to control liquids and vapors trapped withinthe hot tapping machine which will be released upon removalof the machine after work is completed.

APPENDIX A—SUGGESTED HOT TAP CHECKLIST

This checklist is intended to be used as a reminder to accomplish the steps involved inhot tap operations in an orderly manner. Particular circumstances of jobs may dictate addi-tional preparatory steps. This checklist may be retained as a record of the job.

Location ________________________________________________________________

Date ___________________________________________________________________

Job ____________________________________________________________________

Prepared by _____________________________________________________________

BEFORE STARTING THE HOT TAP

Each of the following considerations should be satisfied before starting the hot tap:

1. Review/follow manufacturerÕs instructions.2. Have the contents of the line or vessel to be hot tapped or welded been assessed, andMSDSÕs reviewed for health hazards, to assure procedure is appropriate?3. Is the material in the line or vessel stable under heated conditions (see Section 3)?4. Has the connection been designed per Section 3 requirements?5. Do the flanges, bolts, gaskets, pipe, and valve to be installed meet the code for the lineor vessel to be hot tapped?6. Has the welding procedure specification been developed as covered in Section 3?7. Have approved work permits (Hot Work, Entry, and so forth) been obtained?8. Review manufacturerÕs instructions to ensure that the hot tapping machine has suitablepressure, temperature ratings, and adequate cutter travel for this job.9. Has the valve been pressure tested and the cover fitted to assure that it will work and fitproperly?10. Has the exact location of the hot tap been identified and marked on the line or equip-ment?11. Has the area to be welded been inspected for thickness and freedom from existingwelds, laminations, hydrogen attack, or other metallurgical imperfections? 12. If laminations or defects have been found, has a thorough engineering evaluation beenmade to determine if and how to proceed with the work?13. Has the metallurgy of the line or vessel been established, and is it compatible with theconnecting fitting?14. Can the area support the weight of the hot tapping machine, and is there adequatehoisting and support for the hot tapping machine and subsequent piping?15. If PWHT of the welded area is required, was an appropriate review conducted inaccordance with Section 3?16. Is there sufficient external clearance to install the hot tapping machine and extract thecutter through the valve?17. Is there sufficient internal clearance to retract the cutter and coupon through the valve? 18. Is the hot tap fitting of the proper length to accommodate operation of the hot tappingmachine?19. Have oxygen, combustible gas, and toxic atmosphere tests been conducted in the hot taparea?20. Has a fire watch been assigned and appropriate fire fighting equipment provided?21. Have all personnel in the area been provided with appropriate personal protective equip-ment?22. Is the area to be hot tapped located below the liquid level of the tank, or on a line orvessel in which flow has been established?23. Is there adequate storage area and room for operational and emergency access?


24. Has a procedure been prepared and in place to isolate the work area in the event of afailure? Are personnel trained to implement the procedure?25. Have the requirements been defined for weld inspection and for pressure testing, and isall of the testing equipment on hand and in good working condition?

BEFORE WELDING

Each of the following considerations should be satisfied before welding:

1. Are the welders qualified for the approved welding procedure (specification) to be used?2. Is a preheat of the weld area required?3. Is the fitting properly positioned so that misalignment of the hot tapping machine will notoccur?4. Have the pressure and temperature of the contained materials been reduced as much asthe process operation will allow?5. Have the flow, pressure, and level considerations of Sections 3, 4, and 5 been considered?

BEFORE CUTTING

Each of the following considerations should be satisfied before cutting:

1. Has the weld been inspected and tested?2. Has the hot tap fitting been pressure tested?3. Have the hot tap valve, packing, gasket, and bolts been checked for leakage?4. Have the packing or seals on the hot tapping machine been checked?5. Has the bleed off valve been checked to assure it will hold, is operable, and is not obstructed?6. Are all bolts on the pilot and cutter bit tight?7. Is the coupon catcher on the pilot bit?8. Is the valve centered on the flange?9. Has cutting depth been calculated to avoid cutting the opposite side of the pipe?10. Has the boring bar been run through the valve to assure free passage?11. Have the hot tapping machine and valve been purged, if recommended?

BEFORE REMOVING THE HOT TAPPING MACHINE

Each of the following considerations should be satisfied before removing the hot tappingmachine:

1. Have the manufacturerÕs instructions been followed to be sure that the boring bar is fullyretracted before closing the hot tap valve?2. Has the hot tap valve been closed?3. Has the bleeder valve been opened?4. Has all of the pressure been bled off of the hot tapping machine before removing thebolts from the flange?5. Have provisions been made to contain or control any liquid or gas in the hot tapping machine?

AFTER REMOVING THE HOT TAPPING MACHINE

1. The hot tap machine should be cleaned, removing the hydrocarbons/chemicals from theline or equipment.2 All rags, absorbent pads, and other cleaning materials must be disposed of properly.

8/00Ñ1.25C

Order No. K22014

Additional copies available from API Publications and Distribution:(202) 682-8375

Information about API Publications, Programs and Servicesis available on the World Wide Web at: http://www.api.org

Download - API 2201 (Ed. 1995) Welding or Hot Tapping on Equipment in Service

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