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Post Weld Heat Treatment

Post Weld Heat Treatment

Post Weld Heat Treatment

Using 16" sch 120 Carbon Steel pipe, to effect two  tie in points (welded) what PWHT and Test would be required BY B31.3 The existing line cannot be hydrotested as it would take about 3 weeks to fill and drain etc?


RE: Post Weld Heat Treatment

According to Table 331.1.1 1100-1200° F for 1 hr/in (assuming P-1 material).

Testing paragraph 345.1 - you can do a pneumatic test but if considered too dangerous (345.1 (c) (2) then paragraph 345.9 shall apply. (all the following)

1.100% radiography
2. Flexibility Analysis
3. Sensitive Leak Test (bubble leak)

At least that's how I interpret it.  Maybe others have a different view.

RE: Post Weld Heat Treatment

While i agree with PWHT requirements i would not leak test as ASME B31.3 1999 edition,Para 345.2.3 Special Provisions for Testing, Para 345.2.3 (C) Closure welds states the following,

"The FINAL weld CONNECTING piping systems or components that have been successfully tested in accordance with para 345 NEED NOT be leak tested PROVIDED the weld is examined in-process in accordance with para 344.7 AND passes with 100% radiographic examination in accordance with  para 344.5 OR 100% ultrasonic examination in accordance with para 344.6.

Para 344.7 In process examination

Para 344.7.1. lists requirements and para 344.7.2. lists method of examination (Visual). You should note that this para, 344.7.2 also references that visual shall be done in accordance with para 344.2 where it states that records of in process examination are required to be kept and Visual is to be done in accordance with BPV code section V article 9.

My intepretation is that provided you meet this criteria,and have it fully documented to provide evidence of compliance to requirements, leak testing of tie-in weld joint(s) would not be required.

For your further info,Para 345.1 also gives further exceptions with qualifications but it is related more to owners options.An example of these is 345.1.(A)
"At the owners option,a piping system in catergory D fluid service may be subjected to an initial service leak test in accordance with para 345.7 in lieu of the hydrostatic leak test"

If you are not owner then these are not relevant to you in that you would need to approach owner with justification to use these and seek owners approval.I work for the owner and have been approached on some case by case basis to utilise these but they have always been supported by relevant documentation substantiating and justying waiver of testing requirements.

In any case i would advise that whatever you do, it is formally submitted to owner,or if you are owner then ensure it is formally requested,along with all the relevant back up documentation substantiating your claim for waiver of test requirements and that this is endorsed by the relevant authorised engineer, this will keep you right if you ever get audited

Hope this has helped, john

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