CW6 PART 2

CW6: Part 2

TECHNICAL SPECIFICATION FOR

THE EXTERNAL PROTECTION OF STEEL LINE PIPEAND FITTINGS USING FUSION BONDED POWDERAND ASSOCIATED COATING SYSTEMS

PART 2 - FACTORY APPLIED COATINGS

JANUARY 1993

J230 (Rev 08/98 )

.

CW6 : Part 2

J230 (Rev 08/98 ) - i -

CONTENTS

Page

FOREWORD v

BRIEF HISTORY vi

SECTION ONE - GENERAL REOUIREMENTS

1. SCOPE 1

2. REFERENCES 1

3. DEFINITIONS 2

4. COATING MATERIALS 2

4.1 Selection of coating materials 2

4.2 Storage of coating materials 2

4.3 Toxicity and handling 2

5. COMPONENTS OR WORK PIECES 2

5.1 Component inspection 2

5.2 Component identification 2

5.3 Protection of weld end preparations 3

5.4 Surface preparation 3

5.5 Chemical pretreatment and primers 4

5.6 Extent of approvals 4

6. INSPECTION AND TESTING 4

7. VARIANTS 4

SECTION TWO - FUSION BONDED POWDER COATINGS ON PIPE

8. PROCEDURE QUALIFICATION 7

8.1 General 7

8.2 Coating procedure specification 7

8.3 Coating procedure approval tests 7

9. PRODUCTION COATING PROCEDURE 9


9.2 Coating process 9


10. VISUAL INSPECTION 9

CW6 : Part 2

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Page

11. TESTING OF CURED COATINGS 9

11.1 General requirements 9

11.2 Thickness test 9

11.3 Holiday detection test 9

11.4 Impact resistance test 10

11.5 Adhesion test 10

11.6 Coating cure test 10

11.7 Defect rate 10

11.8 Check procedure 10

12. REPAIRS 11

13. HANDLING OF COATED PIPES 11

14. STRIPPING OF COATING 11

15. IDENTIFICATION 11

SECTION THREE - FUSION BONDED POWDER COATINGS ON FITTINGS


16.1 General 13









19.1 Testing of coated fittings 16





19.6 Coating cure test 17

19.7 Defect rate 17

CW6 : Part 2

J230 (Rev 08/98 ) - iii -

Page


20. REPAIRS 18

21. HANDLING OF COATED FITTINGS 18



SECTION FOUR - MULTI-COMPONENT LIQUID COATINGS ON PIPES AND FITTINGS


24.1 General 19









27.1 Testing of coated pipes and fittings 22



27.4 Hardness and cure of coating test 23



27.7 Heat blister test 23

27.8 Defect rate 23


28. REPAIR OF DEFECTS 24

29. HANDLING OF COATED PIPES AND FITTINGS 24



CW6 : Part 2

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Page

TABLES

1 Minimum quality control requirements 5

2 Component diameter ranges, permissible holidays and repairs 6

APPENDIX

A CALIBRATION PROCEDURES FOR THICKNESS MEASUREMENT OF FUSIONBONDED EPOXY POWDER AND MULTI-COMPONENT LIQUID COATINGS 25

CW6 : Part 2

J230 (Rev 08/98 ) - v -

FOREWORD

This specification has been adopted by Transco and is an editorial revision of the former British Gas TransCospecification GBE/CW6 Part 2. It reflects the identity and organizational structure of Transco - a part of BGplc.

This Transco specification has been approved for use throughout Transco.

Comments and queries regarding the technical content of this Transco specification should be directed to:

Lead EngineerTranscoNorgas HousePO Box 1GBKillingworthNewcastle upon TyneNE99 1GB

Further copies of this Transco specification can be obtained from Dataform Print Management using the printrequisition form G004 quoting the Form Number of this Transco engineering document (not the designation)and your cost code.

Transco engineering documents are revised, when necessary, by the issue of new editions. Users shouldensure that they are in possession of the latest edition by referring to the Transco Register of EngineeringDocuments available on the Transco Information Library.

Compliance with this engineering document does not confer immunity from prosecution for breach of statutoryor other legal obligations.

Contractors and other users external to Transco should direct their requests for further copies of Transcoengineering documents to the department or group responsible for the initial issue of their contractdocumentation.

DISCLAIMER

This engineering document is provided for use by Transco and such of its contractors as are obliged by the termsof their contracts to comply with this engineering document. Where this engineering document is used by anyother party, it is the responsibility of that party to ensure that the engineering document is correctly applied.

CW6 : Part 2

- vi - J230 (Rev 08/98 )

BRIEF HISTORY

First published as BGC/PS/CW6: Part 2Re-issued as GBE/CW6: Part 2

October 1984January 1993

© BG plc 1993

This Transco specification is copyright and must not be reproduced in whole or in part by any means withoutthe approval in writing of BG plc.

CW6: PART 2 SECTION 1

J230 ( Rev 15/07/97 ) - 1 -

TECHNICAL SPECIFICATION FOR

THE EXTERNAL PROTECTION OF STEEL LINE PIPEAND FITTINGS USING FUSION BONDED POWDERAND ASSOCIATED COATING SYSTEMS:PART 2 - FACTORY APPLIED COATINGS

SECTION ONE - GENERAL REQUIREMENTS

1. SCOPEThis Part 2 of Transco Technical Specification* CW6 specifies the operations and requirements for thefactory application to pipes and fittings of materials identified in CW6: Part 1. These coatings may be appliedto components used for the transmission and distribution of natural or manufactured gas. There is norestriction on pressure or nominal size of the components provided they are not operated continuously attemperatures higher than C500 .

Section One covers general requirements and is applicable to all coatings specified in this specification inaddition to the requirements specified in Sections Two, Three or Four.

Section Two deals with the application of fusion bonded powder as an anti-corrosion coating on steel pipe.Section Three deals with the application of fusion bonded powder as an anti-corrosion coating on fittings andSection Four deals with the application of multi-component liquid coating as an anti-corrosion coating on pipeand fittings.

* Hereinafter referred to as 'this specification'.

2. REFERENCESThis Specification makes reference to the documents listed below. Unless otherwise specified the latesteditions of these documents, including all addenda and revisions, shall apply.

Statutes and Regulations

- Control Of Substances Hazardous to Health (COSHH) Regulations

- The Health and Safety at Work etc. Act 1974

British Standards

BS 5750 - Quality systems

BS 7079 - Preparation of steel substrates before application of paints and relatedproducts

Transco specifications

CW6 - Technical specification for the external protection of steel line pipeand fittings using fusion bonded powder and associated coatingsystems:Part 1 - Requirements for coating materials and methods of test

DAT35 - Specification for separator straps for use with resin coated pipe


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L3 - Code of practice for handling, transport and storage of steel pipes,bends and tees.

3. DEFINITIONSFor the purposes of this specification the following definitions shall apply:

Transco: Transco - a part of BG plc.

Transco representative: the person appointed from time to time by Transco and notified in writing to theContractor to act as Transco representative for the purposes of the Contract.

Contractor: the person, firm or company with whom Transco enters into a contract to which thisspecification applies, including the Contractor's personal representatives, successors and permitted assigns.

Manufacturer: the producer of the coating material or his appointed agents or assigns.

4. COATING MATERIALS

4.1 Selection of coating materials4.1.1 Before production coating is permitted, the coating system and the application process shall bedefined and qualified in accordance with the coating procedure approval specified in the appropriate Sectionof this specification.

4.1.2 Only coating systems which comply with CW6: Part 1 shall be used.

4.1.3 The coating material supplied shall be certified by the Manufacturer in accordance with therequirements of CW6: Part 1. The Contractor shall obtain and retain all certificates (see 4.2) andmanufacturers' data sheets. Certificates shall be made available on request.

4.2 Storage of coating materialsTo ensure that the properties of all coating materials are maintained in compliance with the relevant Section ofCW6: Part 1, all coating materials consigned to the coating plant shall be properly stored in accordance withthe Manufacturers' safety requirements and recommendations, at all times, to prevent damage anddeterioration prior to use. Materials shall be used in date order in which they are manufactured.

4.3 Toxicity and handlingAny hazard, (e.g. toxic, corrosive, fire risks) associated with coating materials offered for use to meet therequirements of this specification shall be specified by the Manufacturer, together with his recommendationsfor safe handling in accordance with the requirements of the Health and Safety at Work etc. Act 1974 and theCOSHH Regulations.

5. COMPONENTS OR WORK PIECES

5.1 Component inspectionThe Contractor shall inspect all components on receipt for damage to external surface and weld endpreparations. This shall be recorded for each affected component.

5.2 Component identification5.2.1 All identification markings, whether internal or external to the component, shall be carefullyrecorded before surface preparation begins.

5.2.2 When applicable, identification plates shall be carefully removed and, after the coating has beenaccepted, replaced using an adhesive compatible with the coating. Special care shall be taken to ensure thatthe original data is re-affixed to the correct component.


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5.2.3 The Contractor shall provide a documentary procedure for compliance with these requirements (seealso Table 1, item t).

5.3 Protection of weld end preparations5.3.1 Weld end preparations shall be protected from mechanical damage during handling, storage, surfacepreparation and the coating processes. The methods used shall also ensure that no damage occurs to theinternal surface of the components.

5.3.2 Protection during handling and storage shall be in accordance with L3.

5.3.3 Weld end preparations shall be protected from coating during the process by a method which shallnot be detrimental to the coating process.

The coating shall not be applied within 40 ±15 mm of the component ends for fusion bonded powder coatingapplication, and 150 ±15 mm in the case of multi-component liquid coatings.

5.4 Surface preparation

5.4.1 GeneralThe method of surface cleaning and surface preparation shall be specified by the Contractor as part of thecoating procedure qualification and shall take into account the requirements specified in 5.4.2 to 5.4.7inclusive plus any special requirements specified by Transco.

5.4.2 Contaminant removalWhere oil, grease or other contaminants are present, they shall be removed, without spreading them over thesurface, with a suitable solvent. For components which have been subjected to contamination, the contaminantshall be removed by washing either with potable water or a chemical cleaner. If a chemical cleaner is used,subsequent washing with potable water will be necessary. The component shall be dried before blast cleaning.

5.4.3 Component cleaningComponents shall be blast cleaned in accordance with 9.1 and 17.1 for fusion bonded powder coatings,and 25.1 for multi-component liquid coatings.

5.4.4 Surface inspectionThe metal surface shall be inspected immediately after blast cleaning and all slivers, scabs, etc., made visibleby blast cleaning and detrimental to the coating process shall be removed by grinding. After the removal ofdefects, the remaining wall thickness shall comply with the relevant component specification. Any rectifiedareas shall be blast cleaned to meet the requirements of 5.4.3.

5.4.5 DefectsAny component found to have defects which exceed the levels permitted in the relevant componentspecification shall be set aside for examination.

5.4.6 Pre-coating cleaningDirectly before coating, any dust, grit or other contaminants shall be removed from the component surface bya method established as acceptable by the relevant coating procedure trial and recorded in the relevant coatingprocedure.

5.4.7 Rust blooming or further surface contaminationWhere rust blooming or further surface contamination (see 5.4.2) has occurred, the component shall becleaned again in accordance with 5.4.2 if applicable and again blast cleaned in accordance with 5.4.3.Coating shall take place before any further contamination or rust blooming occurs.


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5.5 Chemical pretreatment and primersChemical pretreatment or primers shall be specified by the Contractor as part of the coating procedurequalification.

5.6 Extent of approvalsThe coating process shall comply with the procedure established in the relevant coating procedurequalification (see clauses 8, 16 and 24). This qualification will be valid for three years and will cover thecomponent size range and the coating material tested.

The component size for the coating procedure trial shall be selected from one of the ranges in Table 2, andapproval will qualify all other sizes within that range.

For fusion bonded powder coatings of line pipe, approval should extend to thickness of ±50% of the wallthickness of the pipe tested.

In order to demonstrate continuing product quality, the Contractor may be required to undertake duplicatecathodic disbondment and watersoak tests on the pipe or fitting test piece from any contract and size rangewithin the contract. Additionally, for pipe only, flexibility testing shall be carried out in duplicate.

Failure of any of the results of these tests to meet the requirements of this specification shall necessitate a newcoating procedure trial.

Any changes in coating materials, component size range, coating process, plant, or quality history shallnecessitate a new coating procedure trial.

6. INSPECTION AND TESTINGThe quality control system shall include each of the requirements listed in Table 1. The actual quality controlrequirements may differ depending on the type of coating being used or whether it is being applied to a pipe orfitting. Table 1 has been prepared to identify these differences.

If, after examination or test, any component has not been cleaned or coated in accordance with thisspecification, the Contractor shall be required to remove the coating which is defective or inadequate and toreclean and recoat the component

7. VARIANTSA contractor shall only propose variants to this specification where the text indicates that variants would beconsidered by Transco.


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TABLE 1 - Minimum quality control requirements


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TABLE 1 - (concluded)

TABLE 2 - Component diameter ranges, permissible holidays and repairs


J230 ( Rev 15/07/97 ) - 7 -

SECTION TWO - FUSION BONDED POWDER COATINGSON PIPE

8. PROCEDURE QUALIFICATION

8.1 GeneralBefore bulk coating of pipe commences, the requirements of 8.2 shall be met and a detailed sequence ofoperations to be followed on the coating of pipe shall be demonstrated.

8.2 Coating procedure specificationThe coating procedure specification shall incorporate full details of the following:

a) Quality plan.

b) Powder system to be used together with appropriate data sheets as defined in clause 4.

c) Pipe dimensions.

d) Process temperature profile.

e) Pipe cleaning.

f) Blast cleaning medium and technique.

g) Blast cleaning finish, surface profile, surface cleaning and metal defect removal.

h) Dust removal.

i) Provision of coating cut-back.

j) Line speed.

k) Preheat method, time and temperature.

l) Powder application including use of recycled material.

m) Curing and quenching time and temperature.

n) Post cure time and temperature.

o) Repair technique.

p) Coating stripping technique.

q) Handling procedures.

8.3 Coating procedure approval tests

8.3.1 GeneralA batch representing a normal production run (typically 15 to 20 pipes) shall be coated in accordance with thecoating procedure (see 8.2), the coating operations being witnessed.

Three pipes from the batch shall be selected for coating procedure approval tests and shall be subjected to thecomplete set of tests specified in 8.3.2 to 8.3.10 inclusive.

The Contractor shall ensure that the tests specified in 8.3.2 to 8.3.10 inclusive are carried out in duplicate andthe results of the tests, demonstrating compliance, made available.

Testing shall be witnessed and a full set of test results shall be recorded. No coated pipe shall be dispatcheduntil the procedure has passed the approval tests.


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8.3.2 Thickness testThe coating thickness shall be a minimum of 350µm and a maximum of 500µm , unless specified otherwise.

A survey of the coated pipe selected for test shall be carried out by measuring, as a minimum, at 1 m intervalsat the cardinal points, in such a manner as to establish the degree and extent of any thickness variation.

A destructive film thickness test shall be carried out to verify the accuracy of the coating thicknessmeasurement technique employed.

8.3.3 Holiday detection testEach pipe shall be checked over 100% of the coated surfaces in accordance with CW6: Part 1, Appendix Cand shall meet the requirements of Table 2.

8.3.4 Impact resistance testWhen tested at ambient temperature in accordance with CW6: Part 1, Appendix D, the cured coating shallwithstand an impact of not less than 1.5 J without a holiday being caused.

8.3.5 Adhesion testThe adhesion of the coating, shall be tested and shall meet the pass requirements in accordance withCW6: Part 1 Appendix E.

8.3.6 Coating cure testThe degree of cure of the coating shall be determined by differential scanning calorimetry (DSC) analysis of asample of the coating taken from a location 1

3 of the pipe length from the trailing end in accordance withCW6: Part 1, Appendix A, clause A.3. The acceptance criterion shall be based on the difference between themeasured Tg2 and Tg1 (as detailed in CW6: Part 1, Appendix A, clause A.3). This difference is termed∆Tg .

The acceptance range of ∆Tg will depend on the type of powder used (see also 11.6).

8.3.7 Flexibility testThe coated pipe shall be sectioned and subjected to a flexibility test in accordance with CW6: Part 1,Appendix B. The coating shall not exhibit signs of cracking, disbondment or pinholes and shall pass a holidaydetection test in accordance with CW6: Part 1, Appendix C.

8.3.8 Cathodic disbonding testThe test sections shall be tested by the procedure detailed in CW6: Part 1, Appendix F. The disbondment shallnot extend more than 5 mm radially from the edge of the damaged coating after the test period of 28 days.

8.3.9 Strain/polarization cracking testThe test sections shall be bent and then polarized and tested as detailed in CW6: Part 1, Appendix G. Thearea of coating exposed to the electrolyte shall not exhibit signs of cracks, disbondment or pinholes and shallpass a holiday detection test as specified in CW6: Part 1, Appendix C.

8.3.10 Water immersion testThe test sections shall be prepared and subjected to a water immersion test as detailed in CW6: Part 1,Appendix E. The coating shall show no loss of adhesion greater than 3 mm after 28 days.


J230 ( Rev 15/07/97 ) - 9 -

9. PRODUCTION COATING PROCEDURE

9.1 Surface preparationThe surface of the pipe to be coated shall be prepared as specified in 5.4.

Components shall be blast cleaned to a minimum standard of BS 7079 Sa 2 12 quality. The surface profile

shall be between 50µm and 100µm peak to trough height, and shall be angular in nature.

9.2 Coating processThe production coating process shall be carried out using the procedure that fulfils the requirements of 8.3.

The nominal thickness of the cured coating shall be 400µm . The actual coating thickness shall be in therange 350µm to 500µm .

Where pipe is to be concrete coated, the correct thickness (normally 650µm to 800µm ) of anti-corrosioncoatings shall be applied, which depends upon the particular concrete coating process.

9.3 Protection of weld end preparationsWeld end preparations shall be protected as specified in 5.3.

10. VISUAL INSPECTIONThe coating colour and appearance shall be uniform and free from runs, sags, blistering, roughness, foamingand general film defects.

11. TESTING OF CURED COATINGS

11.1 General requirementsCured coatings on pipes shall comply with the requirements of 11.2 to 11.8 inclusive and, where indicated.methods of test described in CW6: Part 1 shall be used.

The Contractor shall ensure that the tests specified in 11.4, 11.5 and 11.6 are carried out and the results of thetests, demonstrating compliance, made available.

11.2 ThIckness testThe coating thickness on each pipe shall be checked for compliance with 8.3.2 at not less than five equidistantlocations spread over the total surface of the pipe. The thickness measuring gauge used shall be suitablycalibrated hourly for the specified thickness range (see Appendix A).

11.3 Holiday detection testThe coated pipes shall be subjected to a holiday detection test over 100% of the coated surface as detailed inCW6: Part 1, Appendix C.

The number of holidays detected shall comply with Table 2. If, on any two consecutive pipes, the number ofholidays detected is greater than the normally acceptable level but less than the maximum permissible level,the cause shall be immediately investigated.

If four further consecutive pipes are detected as having holidays between the normally acceptable level andthe maximum permissible level given in Table 2, all production to that point shall be quarantined until thereason for the high frequency of holidays is determined and rectified. A total of 5% of daily production will beaccepted with up to the maximum permissible number of holidays provided that the 5% are not consecutive.

Pipes with more holidays than permitted by Table 2 shall be rejected for subsequent stripping (see clause 14)and recoating.


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All holidays shall be repaired in accordance with clause 12 and satisfactorily retested before dispatch of thepipe.

Defects detected immediately before dispatch shall not be repaired but shall be conspicuously andpermanently marked on the pipe and recorded on the relevant inspection documentation.

11.4 Impact resistance testThe coated pipe shall be subjected to an impact resistance test as detailed in CW6: Part 1, Appendix D, atfrequencies of once every hour or 20 pipes, whichever is the more frequent. This initial frequency maysubsequently be varied, the revised frequency being based on quality history.

The curedcoating shall meet the requirements specified in 8.3.4.

11.5 Adhesion testThe coated pipe shall be subjected to an adhesion test of the cured coating as detailed in CW6: Part 1,Appendix E. The test shall be carried out at three locations on the pipe (one metre from each end and at a midpoint) and initially at frequencies of once every hour or 20 pipes, whichever is the more frequent. This initialfrequency may subsequently be varied, the revised frequency being based on quality history.

The cured coating shall meet the initial test procedures, investigation procedures and result reportingrequirements of CW6: Part 1, Appendix E.

11.6 Coating cure testThe cure of the coating shall be checked for compliance with 8.3.6 by DSC analysis at frequencies of onceevery hour or 20 pipes, whichever is the more frequent. This initial frequency may subsequently be varied, therevised frequency being based on quality history.

To confirm the requirements of 8.3.6, the test procedure detailed in CW6: Part 1, Appendix A, clause A.3shall be carried out.

If a test does not result in a value of ∆Tg within the acceptable range, the following retest procedure shall beused:

For a measured ∆Tg within + 2o C of the upper acceptable limit, a further sample from the pipe shall be tested. If the value of ∆Tg obtained lies within the acceptable range, the pipe shall be accepted. If it does not, the pipe shall be rejected and adjacent pipes in the production run shall be successively sampled and tested until acceptable coating is identified.

11.7 Defect rateShould tests in any production batch (typically the production from a seven hour shift) show a rejection rate ofmore than 10% defective pipe for any one test, every pipe in that batch shall be individually subjected to thattest. In such cases, the Contractor shall simultaneously conduct an investigation to establish the cause of thedefects.

The cost of retrieval of any pipes dispatched from the coating premises and/or any additional expensesincurred as a result of additional examination shall be borne by the Contractor.

11.8 Check procedureIf any individual pipe fails to meet the requirements of 11.2 to 11.7 inclusive, a check procedure shall beinitiated. This shall involve checking all pipe back to the preceding acceptable pipe. The pipe numbers shallbe available from the final inspection batch. These pipes shall be subjected to an examination similar to thatcarried out on the failed pipe. If the number of defects detected is significant, the entire production for that dayshall be quarantined and investigated.


J230 ( Rev 15/07/97 ) - 11 -

12. REPAIRSAll holidays and other coating defects shall be repaired with multi-component materials to ensurecompatibility with the applied coating. Repair methods shall include adequate surface preparation techniques,suitable overlaps, coating thicknesses and a demonstration of satisfactory adhesion and cure. All repairs shallbe retested for holidays in accordance with the requirements detailed in CW6: Part 1, Appendix C.

The maximum areas of repair for any pipe shall not exceed, in total, the areas given in Table 2. Repairs shallnot be carried out within 200 mm of the end of the coating, but all areas of damage shall be recorded andmarked.

13. HANDLING OF COATED PIPES13.1 All coated pipes shall be handled and stored in accordance with L3 to prevent damage to the pipeand coating.

Where the use of pipe separators is required to prevent damage to the cured coating, these shall be asspecified in DAT35.

13.2 Protection from damage and corrosion of the weld end preparations may be required prior tostacking and load out. The type of protection and the method of application shall be specified by Transco.(see L3).

14. STRIPPING OF COATINGRejected coating shall be removed only by a procedure which shall not cause any mechanical damage to thepipe and shall not cause the steel temperature to exceed 250 0C.

15. IDENTIFICATIONThe Contractor shall be responsible for ensuring that all internal or external identification markings are notedin accordance with 5.2 before surface preparation begins, and are replaced after the coating process.


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J230 ( Rev 15/07/97 ) - 13 -

SECTION THREE - FUSION BONDED POWDER COATINGSON FITTINGS


16.1 GeneralBefore bulk coating of fittings commences, the requirements of 16.2 shall be met and a detailed sequence ofoperations to be followed for the coating of fittings shall be demonstrated.

16.2 CoatIng procedure specification16.2.1 The coating procedure specification shall incorporate full details of the following:

a) Quality plan.

b) Powder system to be used together with appropriate data sheets as defined in clause 4.

c) Fitting dimensions.


e) Fitting cleaning.



h) Dust removal.


j) Preheat method, time and temperature.

k) Powder application.

l) Curing and quenching time and temperature.

m) Post cure time and temperature.

n) Repair technique.

o) Coating stripping technique.

p) Handling procedures.

16.2.2 Recycled powder shall not be used to coat pipeline fittings.

16.2.3 Where fluidized bed dipping is to be used, the applicator shall provide written evidence that thepowder in the fluidized bed at the time of the procedure qualification test complies with CW6: Part 1.


16.3.1 General requirementsA batch of fittings shall be coated in accordance with the approved coating procedure (see 16.2), the coatingoperations being witnessed. Pipe pups of equivalent dimensions may be used instead of fittings.

Three coated fittings or pipe pups from the batch shall be selected for coating procedure approval tests andshall be subjected to the complete set of tests specified in 16.3.2 to 16.3.8 inclusive.

The Contractor shall ensure that the tests specified in 16.3.2 to 16.3.8 inclusive are carried out in duplicateand the results of the tests, demonstrating compliance, made available.


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Testing shall be witnessed and a full set of test results shall be recorded. No coated fittings shall be dispatcheduntil the procedure has passed the approval tests.

16.3.2 Thickness testThe coated fittings shall be subjected to a thickness test of the cured coating as specified in 19.2. Thethickness shall be not less than 350µm and not greater than 1500µm .

16.3.3 Holiday detection testThe coated fittings shall be subjected to a holiday detection test over 100% of the coated surface as detailed inCW6: Part 1, Appendix C. The number of holidays detected shall meet the requirements of Table 2.

16.3.4 Impact resistance testThe coated fittings shall be subjected to an impact resistance test at ambient temperature as specified in 19.4and as detailed in CW6: Part 1, Appendix D. The coating shall withstand an impact of 1.5 J without a holidaybeing caused.

16.3.5 Adhesion testThe coated fittings shall be subjected to an adhesion test as specified in 19.5 and as detailed in CW6: Part 1,Appendix E.

16.3.6 Coating cure testThe degree of cure of the coating shall be determined by DSC analysis of a sample of the coating taken fromthe area of thickest coating and any identified 'cool spots', and tested in accordance with CW6: Part 1,Appendix A. The acceptance criterion shall be based on the difference between the measured Tg2 and Tg1

(as defined in CW6: Part 1, Appendix A). This difference is termed ∆Tg .

The acceptance range of ∆Tg will depend on the type of powder used (see also 19.6).

16.3.7 Cathodic disbonding testThe test sections shall be subjected to a cathodic disbonding test as detailed in CW6: Part 1, Appendix F. Thedisbondment shall not extend more than 5 mm radially from the edge of the damaged coating after the testperiod of 28 days.

16.3.8 Water immersion testThe test sections shall be prepared and subjected to a water immersion test as detailed in CW6: Part 1,Appendix E. The coating shall show no loss of adhesion greater than 3 mm after 28 days.


17.1 Surface preparationThe surface of the fitting to be coated shall be prepared as specified in 5.4.

Components shall be blast cleaned to a minimum standard of BS 7079 Sa 2 12 quality. The surface profile

shall be between 50µm and 100µm peak to trough height and shall be angular in nature.

17.2 Coating process

17.2.1 GeneralThe production coating process shall be carried out using a procedure that fulfills the requirements of 16.3.

The thickness of the coating shall be not less than 350µm , and not greater than 1500µm .


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17.2.2 Spray applied coating

17.2.2.1 Operator qualificationsWhen required, the individual operators carrying out the powder spraying application shall be subjected to aqualification test in which they will be required to demonstrate proficiency in the spraying process as laiddown in the relevant section of the procedures.

17.2.2.2 PreheatingPreheating shall be carried out using suitable heating equipment and its duration shall not be extended formore than 30 min beyond the time at which the required surface temperature is reached. The surfacetemperature shall be continuously monitored at a selected point by means of a surface pyrometer, or any othermethod which may be proposed as a variant for consideration by Transco, which shall be calibrated against astandard method of surface temperature measurement. If the appearance of the fitting after preheating isunsuitable, it shall be blast cleaned (see 5.4) before continuing the coating procedure.

17.2.2.3 Spraying equipmentThe spraying equipment shall be adequate for applying the powder in accordance with the powdermanufacturer's instructions and the qualification procedure. The equipment shall be maintained in good orderby the Contractor and/or the equipment supplier. All air lines shall be provided with filters and vapour traps toensure that the air is free from oil and moisture. All critical parameters shall be monitored.

17.2.2.4 Spraying procedureThe spraying procedure shall be in accordance with the qualification procedure which shall include a totaltime allowed for coating. Individual operators shall be experienced in the use of equipment and shall besuitably qualified (see 17.2.2.1). The temperature of the fitting shall be checked at selected points on thesurface, in such a manner as to ensure that the surface temperature does not fall below that recommended bythe powder supplier. If the limits of time and temperature are exceeded, the fitting shall be cleaned andrecoated.

17.2.2.5 Post cureIf post curing is required by the qualification procedure, the component shall be moved within a definedperiod into the post curing oven. The time and temperature shall be monitored as in 17.2.2.2.

17.2.3 Dip applied coatings

17.2.3.1 PreheatingThe duration of preheating shall not be extended for more than 30 min beyond the time at which the requiredsurface temperature is reached. The surface temperature shall be monitored at a selected point by means of asurface pyrometer or any other method, which may be proposed as a variant for consideration by Transco,which shall be calibrated against a method of a standard surface temperature measurement. If the appearanceof the fitting after preheating is unsuitable, it shall be blast cleaned (see 5.4) before continuing the coatingprocedure.

17.2.3.2 Dipping bathThe dipping bath shall meet the following requirements:

a) The dipping bath shall be of dimensions which enable a fitting of the maximum stated size tobe freely dipped.

b) The method of fluidization shall promote even fluidization and control of powder densitywithin the bed.

c) The bed shall be renewed completely if the powder ceases to comply with CW6: Part 1 or ifthe condition of the powder results in unacceptable deterioration of the finished product.


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17.2.3.3 Dipping procedureThe dipping procedure shall be as follows:

a) When the powder is fluidized to the required density, the fluidized bed shall be made up to adepth adequate for dipping the fittings.

b) Prior to dipping, the temperature of the fitting shall be checked at selected points on thesurface to ensure that the surface temperature does not fall below that recommended by thepowder supplier.

c) The coating time shall be specified for each type and size of fitting.

d) If limits of time and temperature are not achieved, the fitting shall be cleaned and recoated.

17.2.3.4 Post cureIf post curing is required by the qualification procedure, the fitting shall be moved with the minimum delayinto the post curing oven. The time and temperature shall be monitored as specified in 17.2.3.1.




19.1 Testing of coated fittingsCured coatings on fittings shall comply with the requirements of 19.2 to 19.7 inclusive and, where indicated,methods of test described in CW6: Part 1 shall be used.

The Contractor shall ensure that the tests specified in 19.2 to 19.7 inclusive are carried out in duplicate andthe results of the tests, demonstrating compliance, made available.

19.2 Thickness testThe coated fittings shall be subjected to a thickness test of the cured coating at not less than 20 locationsspaced evenly to represent the total area of the coated fitting. The thickness measuring gauge used shall becalibrated hourly for the specified thickness range (see Appendix A).

The coated fittings shall meet the thickness requirements specified in 16.3.2.

19.3 Holiday detection testThe coated fittings shall be subjected to a holiday detection test over 100% of the coated surface as detailed inCW6: Part 1, Appendix C.

The number of holidays detected shall comply with Table 2. If, on any two consecutive fittings, the number ofholidays detected is greater than the normally acceptable level but less than the maximum permissible level,the cause shall be immediately investigated.

If four further consecutive fittings are detected as having holidays between the normally acceptable level andthe maximum permissible level given in Table 2, all production to that point shall be quarantined until thereason for the high frequency of holidays is determined. A total of 5% of daily production will be acceptedwith up to the maximum permissible number of holidays provided that the 5% are not consecutive.

Fittings with more holidays than permitted by Table 2 shall be rejected for subsequent stripping(see clause 14) and recoating.


J230 ( Rev 15/07/97 ) - 17 -

All holidays shall be repaired in accordance with clause 12 and satisfactorily retested before dispatch of thefitting.

Defects detected immediately before dispatch shall not be repaired but shall be conspicuously andpermanently marked on the fitting and recorded on the relevant inspection documentation.

19.4 Impact resistance testInitially, the impact resistance of the coating shall be checked for compliance with 16.3.4 determined at fivelocations chosen to represent the area coated, as detailed in CW6: Part 1, Appendix D.

The frequency of testing shall, initially, be once every two hours or five fittings. whichever is the morefrequent. Subsequently, this test frequency may be varied based on quality history.

19.5 Adhesion testThe coated fittings shall be subjected to an adhesion test of the cured coating, at one location on the fitting, asdetailed in CW6: Part 1, Appendix E.

The frequency of testing shall, initially, be once every two hours or five fittings, whichever is the morefrequent. Subsequently, this frequency may be varied based on quality history.

19.6 Coating cure testIn order to meet the acceptance requirements of 16.3.6, the DSC test procedure detailed in CW6: Part 1,Appendix A, shall, initially, be carried out on each fitting. Subsequently, this rate of testing may be variedbased on quality history.

If a test does not result in a value of ∆Tg within the acceptable range, the following retest procedure shall beused:

a) For a measured ∆Tg within +2 0C of the upper acceptable limit, a further two samples fromthe test section shall be tested. All glass transition temperature values shall be expressed ascorrected temperatures.

b) If the value of ∆Tg obtained lies within the acceptable range, the fitting shall be accepted.

c) If the value of ∆Tg obtained does not lie within the acceptable range, the fitting shall berejected and adjacent fittings in the production run shall be successively sampled and testeduntil acceptable coating is identified.

19.7 Defect rateShould tests in any production batch (typically the production from a seven hour shift) show a rejection rate ofmore than 20% defective fittings for any one test, every fitting in that batch shall be individually subjected tothat test. In such cases, the Contractor shall simultaneously conduct an investigation to establish the cause ofthe defects.

The cost of retrieval of any fittings with defective coatings dispatched from the coating premises and/or anyadditional expenses incurred as a result of additional examination shall be borne by the Contractor.

19.8 Check procedureIf any fitting fails the requirements of 19.2 to 19.6 inclusive, a check procedure shall be initiated. This willinvolve checking all fittings back to the preceding acceptable fitting. The fitting numbers shall be availablefrom the final inspection batch. These fittings shall be subjected to an examination similar to that carried outon the failed fitting. If the number of defects detected is significant, the entire coating production for that dayshall be quarantined and investigated.


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20. REPAIRSAll holidays and other coating defects shall be repaired with multi-component materials to ensurecompatibility with the applied coating. All repairs shall be retested for holidays in accordance withCW6: Part 1, Appendix C.

The maximum repair area shall be in accordance with Table 2.

Repairs shall not be carried out within 200 mm of the end of the coating, but all areas of damage shall berecorded and marked.

21. HANDLING OF COATED FITTINGSAll coated fittings shall be handled and stored in accordance with the relevant fitting standard and L3 toprevent damage to the fitting and coating.

The fitting ends may be required to be protected from damage and corrosion. The type of protection and themethod of application shall be specified by Transco (see L3).

22. STRIPPING OF COATINGRejected coating shall be removed by a procedure which shall not cause mechanical damage to the fitting andshall not cause the steel temperature to exceed 2500 C .

23. IDENTIFICATIONThe Contractor shall be responsible for ensuring that all internal or external identification markings are notedbefore surface preparation begins, and are replaced after the coating process in accordance with 5.2.


J230 ( Rev 15/07/97 ) - 19 -

SECTION FOUR - MULTI-COMPONENT LIQUID COATINGSON PIPES AND FITTINGS


24.1 GeneralBefore bulk coating of pipes and fittings commences, the requirements of 24.2 shall be met and a detailedsequence of operations to be followed for the coating of pipes and fittings shall be demonstrated.

24.2 Coating procedure specificationThe coating procedure specification shall incorporate full details of the following:

a) Quality plan.

b) Multi-component liquid coating to be used together with appropriate data sheets as defined inclause 4.

c) Pipe or fitting dimensions.


e) Pipe or fitting cleaning.



h) Dust removal.


j) Preheat method time and temperature (if specified).

k) Residual surface contamination.

l) Multi-component liquid and primer (if used) mixing and application.

m) Curing regime.

n) Repair technique.

o) Coating stripping technique.

p) Handling procedures.


24.3.1 General requirementsThree test pieces for the coating procedure approval tests shall be selected from pipe or fittings coated inaccordance with the curing regime (see 24.2). Test pieces shall be subjected to the complete set of testsspecified in 24.3.2 to 24.3.10 inclusive after curing in accordance with the Manufacturer's recommendations.Testing shall be witnessed and a full set of test results recorded. No coated pipe or fittings shall be dispatcheduntil the procedure has passed the approval tests.

The Contractor shall ensure that the tests specified in 24.3.2 to 24.3.10 inclusive are carried out and theresults of the tests, demonstrating compliance, made available.

24.3.2 Thickness testThe coated test pieces shall be subjected to a thickness test of the cured coating as specified in 27.2. Thecured coating thickness shall be not less than 1.5 mm and uniform for all tests.


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24.3.3 Holiday detection testThe coated test pieces shall be subjected to a holiday detection test over 100% of the coated surface asdetailed in CW6: Part 1, Appendix C. The number of holidays detected shall not exceed those specified inTable 2.

24.3.4 Hardness and cure testThe coated test pieces shall be subjected to a hardness and cure test as specified in 27.4.

24.3.5 Impact resistance testThe coated test pieces shall be subjected to an impact resistance test at ambient temperature as detailed inCW6: Part 1, Appendix D. The cured coating shall withstand an impact of 5 J without a holiday being caused.

24.3.6 Adhesion testThe coated test pieces shall be subjected to an adhesion test as detailed in CW6: Part 1, Appendix E.

24.3.7 Flexibility test (for pipe only)The coated test pieces shall be sectioned and subjected to a flexibility test as detailed in CW6: Part 1,Appendix B. The coating shall not exhibit signs of cracking, disbondment or pinholes and the test pieces shallalso pass a holiday detection test as detailed in CW6: Part 1, Appendix C.

24.3.8 Cathodic disbonding testThe coated test pieces shall be subjected to a cathodic disbonding test as detailed in CW6: Part 1,Appendix F. The disbondment shall not extend more than 5 mm radially from the edge of the damaged coatingafter the test period of 28 days.

24.3.9 Strain/polarization cracking test (for pipe only)The coated test pieces shall be bent and then polarized as detailed in CW6: Part 1, Appendix G. After 28 dayspolarization, the test pieces shall show no visible cracking or pinholing of the coating and the test pieces shallalso pass a holiday detection test as detailed in CW6: Part 1, Appendix C.

24.3.10 Water immersion testThe coated test pieces shall be prepared and subjected to a water immersion test as detailed in CW6: Part 1,Appendix E. The coating shall show no loss of adhesion greater than 3 mm after 28 days.


25.1 Surface preparationThe surface of the pipe or fitting to be coated shall be prepared as specified in 5.4, except that the qualityrequired shall be to BS 7079 Sa 2 1

2 and the profile shall be within the range 75µm to 100µm peak totrough height and angular in nature.

25.2 Coating process

25.2.1 GeneralThe production coating process shall be carried out using a procedure approved in accordance with clauses4.5.4 and 24. This shall normally be a spray coating process, but brush application may be used on smallareas.

The thickness of the coating shall be not less than 1.5 mm.


J230 ( Rev 15/07/97 ) - 21 -

25.2.2 Pre-mix agitationEach coating component shall, when necessary, be mixed to a homogeneous state before any part of thecomponent is withdrawn from its container.

25.2.3 Mixing for useThe components (e.g. base and curing agent) of a coating material are normally supplied separately packed.They shall be mixed in accordance with the Manufacturer's instructions.

If preheating of one or more of the coating material components is required prior to mixing and application,the procedure shall be monitored and controlled to avoid excessive heating which might affect application orthe integrity of the coating.

Material cure time is dependent on ambient temperature. Should it be necessary to shorten the cure time, thismay be achieved by the application of heat to the prepared surface before coating commences.

Thinners shall not be used unless recommended by the Manufacturer.

25.2.4 Spraying equipmentThe spraying equipment shall be adequate for applying the coating in accordance with the coatingmanufacturer's instructions and the qualification procedure. The equipment shall be maintained in good orderby the Contractor and/or the equipment supplier. All air lines shall be provided with filters and vapour traps toensure that the air is free from oil and moisture. All critical parameters shall be monitored.

Tools and equipment shall be cleaned using only such solvents as are recommended by the coating materialmanufacturer.

25.2.5 Operator qualificationsWhen required, the individual operators carrying out the multi-component liquid spraying application shall besubjected to a qualification test in which they will be required to demonstrate proficiency in the sprayingprocess as laid down in the relevant section of the procedures.

25.2.6 Spraying procedure25.2.6.1 The spraying procedure shall be in accordance with the qualification procedure which shall includea total time allowed for coating. Individual operators shall be experienced in the use of equipment and shall besuitably qualified (see 25.2.5).

25.2.6.2 Solvent flushing of spray equipment used for rapid cure materials is normally employed to preventcoating material gelling in the gun when spray operations cease for significant periods of time. It is essentialthat, on recommencement of spraying, the operator ensures that solvent-free material only is applied to thework to avoid ensuing problems caused by solvent blistering of the coating. Additionally, all solvent flushingoperations shall be carried out by discharging the solvent into a suitable container. Solvent shall not bedischarged at random on to the surrounding work area.

25.2.6.3 Coating material filters shall be installed as part of the spray equipment to ensure that particleswhich would be detrimental to the coating application are not deposited on to the surfaces being coated.Regular inspection and maintenance of the filters is recommended.

25.2.6.4 The coating component feed lines to the spray-gun shall be equipped with a pressure gauge fittedwith a pulsation damper, to facilitate pressure readings. The location of this gauge shall be downstream of allpressure drop devices and as near to the gun tip as is reasonably practicable.

25.2.6.5 The coating contractor shall monitor and record all relevant ambient conditions during applicationand cure.


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25.2.6.6 The temperature of the metal surface at the time of application shall be not lower than C100 .Ideally, for optimum results, the metal surface temperature should be between C250 and C350 , but, it isessential that care be taken to avoid contaminating the surface. The relative humidity shall be 80% or lessduring application and the ensuing first hour of cure time.

25.2.6.7 Coating operations shall be stopped when the conditions are such that an inferior coating will result.Such conditions include inadequate surface preparation, unsatisfactory application procedure, poor coatingmaterial performance and when the steel temperature at any stage of the process falls to within 3 0C of thedew point measured in the work area.




27.1 Testing of coated pipes and fittingsCured coatings on pipe and fittings shall comply with the requirements of 27.2 to 27.8 inclusive and, whereindicated, methods of test described in CW6: Part 1 shall be used.

The Contractor shall ensure that the tests specified in 27.2 to 27.8 inclusive are carried out and the results ofthe tests, demonstrating compliance, made available.

27.2 Thickness testThe coating thickness on each pipe shall be checked at not less than five equidistant locations spread over thecoated surface of the pipe and the coating thickness of each fitting shall be tested in 20 locations spacedevenly to represent the total area of the fittings coated. All readings of the dry film thickness shall meet therequirements specified in 24.3.2. The thickness measuring gauge used shall be calibrated hourly for thespecified thickness range (see Appendix A). Values less than those specified in 24.3.2 shall constitute causefor rejection.

27.3 Holiday detection testEvery pipe and fitting shall be subjected to a holiday detection test over 100% of their coated surfaces asdetailed in CW6: Part 1, Appendix C.

The number of holidays detected shall comply with Table 2. If, on any two consecutive pipes or fittings, thenumber of holidays detected is greater than the normally acceptable level, but less than the maximumpermissible level, the cause shall be immediately investigated.

If four further consecutive pipes or fittings are detected having holidays between the normally acceptable leveland the maximum permissible level given in Table 2, all production to that point shall be quarantined until thereason for the high frequency of holidays is determined. A total of 5% of daily production will be acceptedwith up to the maximum permissible number of holidays provided that the 5% are not consecutive.

Pipes or fittings with more holidays than permitted by Table 2 shall be rejected for subsequent stripping (seeclause 14) and recoating.

All holidays shall be repaired in accordance with clause 12 and satisfactorily retested before dispatch of thepipes or fittings.

Defects detected immediately before dispatch shall not be repaired but shall be conspicuously andpermanently marked on the pipe or fitting and recorded on the relevant inspection documentation.


J230 ( Rev 15/07/97 ) - 23 -

27.4 Hardness and cure of coating testThe hardness and cure of the coating on every pipe and fitting shall be determined.

The value of the hardness obtained shall be within the range specified by the Manufacturer of the material toindicate the correct degree of cure of the coating.

27.5 Impact resistance testThe coated pipes and fittings shall be subjected to an impact resistance test of the cured coating as detailed inCW6: Part 1, Appendix D.

The frequency of testing shall be, for pipes, initially once every two hours or 20 pipes and, for fittings,initially once every two hours or five fittings, whichever is more frequent.

The cured coating shall withstand a minimum impact of 5 J without resulting in a breakdown or loss ofadhesion of the coating.

27.6 Adhesion testThe coated pipes and fittings shall be subjected to an adhesion test of the cured coating as detailed inCW6: Part 1, Appendix E.

The frequency of testing shall be, for pipes, initially once every two hours or 20 pipes and, for fittings,initially (at one location on the fitting) once every two hours or five fittings, whichever is the more frequent.

This initial test frequency may subsequently be varied, the revised test frequency being based on qualityhistory.

27.7 Heat blister testAfter initial cure, a test plate of representative wall thickness, coated at the same time as the batch of pipe andfittings with multi-component liquid systems, shall be subjected to a heat blister test by heating the steel to atemperature in the range 500 C to 600 C and holding the temperature within that range for one hour.

After heating, the test plate shall be inspected for blisters. In the event of blistering being observed, aninvestigation into the cause of the defect shall be immediately undertaken. Samples of coating may have to beremoved for nitrogen analysis or other appropriate tests and the coating operations may have to cease duringthe period of the investigation. When the cause of the defect has been established, components in the coatingsequence during which the plate has been coated, shall be tested until an acceptable coating is identified.

For pipes, testing shall normally be carried out at a frequency of once every two hours or 20 pipes, whicheveris the more frequent. For fittings, testing shall normally be carried out at a frequency of once every two hoursor five fittings, whichever is the more frequent. These test frequencies may be varied, and the applicator mayalso have to vary the test frequency.

Localized blisters shall be repaired.

27.8 Defect rateShould tests in any coating production batch (typically the production from a seven hour shift) show arejection rate of more than 10% defective pipes or fittings for any one test, then every component in that batchshall be individually subjected to that test. In such cases the Contractor shall simultaneously conduct aninvestigation to establish the cause of the defects.

The cost of retrieval of any pipes and fittings dispatched from the coating premises and/or any additionalexpenses incurred as a result of additional examination shall be borne by the Contractor.


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27.9 Check procedureIf any pipe or fitting has defects in excess of the requirements of 27.2 to 27.8 inclusive, a check procedureshall be initiated. This shall involve checking all pipes or fittings back to the preceding acceptable one. Thepipe or fitting numbers shall be available from the final inspection batch. These pipes or fittings shall besubjected to an examination similar to that carried out on the failed pipe or fitting. If the number of defects issignificant, the entire coating production for that day shall be quarantined and investigated.

28. REPAIR OF DEFECTSAll repairs to holidays and other coating defects shall be with multi-component liquid materials to ensurecompatibility with the applied coating. Repair methods shall include adequate surface preparation techniques,agreed overlaps, coating thicknesses and a demonstration of satisfactory adhesion and cure. All repairs shallbe retested for holidays as detailed in CW6: Part 1, Appendix C.

Maximum areas of repair shall be not greater than those given in Table 2.

The area to be overlapped shall extend to at least 75 mm from the periphery of the defect. The repair materialshall be applied to the prepared surfaces using a scraper, palette knife or paint brush.

Care shall be taken to ensure that the thickness over the repair area is not less than 1.5 mm when cured.

29. HANDLING OF COATED PIPES AND FITTINGSAll coated pipes and fittings shall be handled and stored in accordance with L3 and the relevant fittingstandard where appropriate to prevent damage to the component and coating.

The weld end preparations and fitting ends may be required to be protected from damage and corrosion. Thetype of protection and the method of application shall be specified by Transco.

30. STRIPPING OF COATINGRejected coatings shall be removed by a procedure which shall not cause mechanical damage to the pipe orfitting and shall not cause the steel temperature to exceed 2500 C .

It should be noted that multi-component liquids give off toxic fumes when heated and due care shall be takennot to inhale any combustion products.

31. IDENTIFICATIONThe Contractor shall be responsible for ensuring that all internal and external identification markings arenoted before the surface preparation begins, and are replaced after the coating process in accordance with 5.2.

CW6: PART 2

J230 ( Rev 15/07/97 ) - 25 -

APPENDIX A

CALIBRATION PROCEDURES FOR THICKNESS MEASUREMENT OF FUSIONBONDED EPOXY POWDER AND MULTI-COMPONENT LIQUID COATINGS

A.1 GENERALThe following calibration procedures for inferential thickness measurement gauges shall be used asappropriate. Calibration of gauges using standard shims on a flat steel substrate will produce a higher readingthan when calibrating on a surface with a grit-blasted profile. The difference in reading is proportional to theprofile height. With coatings in excess of one millimetre thickness, the calibration 'profile factor' is notsignificant. In cases of dispute, the thickness shall be measured by a direct method, typically using a pipelineinspector's gauge (PIG).

A.2 CALIBRATION USING PLASTICS FOIL SHIMS OF KNOWN THICKNESS ON GRIT-BLASTED STEEL

This method shall be used when it is possible to calibrate the instrument on a clean dry grit-blasted area of thepipe or fitting which is representative of the steel cleanliness and surface roughness at the time of coating. Toobtain accurate thickness readings using magnetic 'pull-off' and eddy current instruments the followingprecautions shall be taken during calibration:

a) Non-metallic shims of known thickness with certification traceable to national standards shallbe used.

b) The shims shall be examined before use to ensure that they are in good condition with no signof roughness or wear.

c) The shims selected for calibration shall be close to the expected thickness of the coating beingevaluated.

d) The steel substrate being used for calibration shall be a representative area of the pipe orfitting and shall be free of oil, dirt, rust, adhesive, pre-treatment or other contaminant.

e) The surface profile and steel cleanliness when calibration is being carried out shall be typicalof the steel condition at time of coating.

f) The steel substrate shall be at ambient temperature.

g) The probe on the thickness gauge shall be clean and free from contaminants.

h) Where repeated thickness measurements are being made, the instrument shall be re-calibratedat hourly intervals.

A.3 CALIBRATION USING PLASTICS FOIL SHIMS ON A FLAT STEEL SURFACEWhere it is not possible to obtain a representative area of the pipe or fitting, calibration shall be carried out onflat steel plates of at least 1 mm thickness using plastics foil shims of known thickness. As an alternative,American National Bureau of Standards (NBS) or Deutscher Institut fur Normalisierung (DIN) coated testplates may be used. Plastics foil shims or test plates shall be accompanied by thickness certification traceableto national standards.

The following precautions shall be taken to ensure accurate measurements:

a) Test certificates for plastics foil shims or coated test plates shall be available.

b) The shims or test plates shall be in good condition with no sign of wear or roughness.

c) The shim or coated test plate selected for calibration shall be close to the expected thickness ofthe coating being evaluated.

CW6: PART 2

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d) The steel substrate shall be dry, clean and free from rust or any contaminant.

e) The test plate shall be flat and at least one millimetre thick.

f) Where repeated thickness measurements are being taken, the instrument shall be re-calibratedat two-hourly intervals.

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