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Up Topic Welding Industry / Technical Discussions / PWHT as per ASME B31.3
- - By JCaprarulo (**) Date 12-31-2005 12:48
Table 331.1.1 states mandatory PWHT for "nominal thickness" > 19 mm.
Is PWHT mandatory in the case of pipe 12" Sch.80, nominal thickness = 17.47 mm, but which actual measured thickness is 20 mm.
My question is about if thickness fabrication tolerances (plus and minus), -12.5 % / + 15 % for this case are included in this "nominal thickness" value.
Thanks in advance for your responses.
Parent - - By jon20013 (*****) Date 01-01-2006 16:15
No. The thickness stated is for nominal size. No PWHT required for 17.47mm nominal. I posed the same question to ASME regarding PQR thicknesses and got the response above, but if you actually measure the thickness on your PQR thats what your stuck with.
Parent - - By JCaprarulo (**) Date 01-01-2006 22:52
It means : if my PQR was qualified with thickness > 19 mm. shall be PW Heat Treated ??
Parent - - By jon20013 (*****) Date 01-02-2006 05:08
It means if your constructing material is > 19mm (nominal) it shall be PWHT. I asked the question to ASME about recording nominal sizes versus actual sizes and was told I should record the nominal but, if measured precisely then the actual would be recorded.

I'm sorry, the PQR was simply an example. ASME IX will not mention when PWHT must be done, that is a factor of the implementing (fabrication / construction) code.

The real answer is the nominal thickness is what you go by in fabrication / construction.
Parent - - By JCaprarulo (**) Date 01-02-2006 11:00
OK , thanks a lot for clarification.
Parent - - By Bill M (***) Date 01-03-2006 13:57
Just a comment-
You did not mention the process, but PWHT is typically an essential variable. Did you PWHT your PQR coupon?

Like Jon mentioned above, if the Code of construction requires PWHT, and your PQR coupon was not PWHT'ed, you have to re-qualify the PQR to include the heat treat in order to implement PWHT on the job.
Parent - - By jon20013 (*****) Date 01-03-2006 14:53
Thanks for clarifying that point Bill.
Parent - - By Shane Feder (****) Date 01-04-2006 03:36
Hello Jon,
Happy New Year to you and the family.
I am currently in NZ on holidays and have no access to my codes so you can probably help me out.
I always thought that the addition of PWHT was non essential but the deletion of PWHT was an essential variable.
If you qualify a PQR without PWHT and it passes all the required mechanical tests then by adding PWHT in production you would only be improving/enhancing the mechanical properties of that weld ( Only talking P1 material).
Have I got it wrong?
Regards,
Shane Feder
Parent - - By jon20013 (*****) Date 01-04-2006 11:22
Happy New Year to you too Shane! Glad to hear your home for the holidays! It must be nice!

Shane, either the addition or deletion of PWHT, change of time or temperatures is an essential under ASME IX rules, this includes the P1's. See QW-407.1 when you have a chance. Hope this doesn't cause you any grief back on your project!
Parent - By Shane Feder (****) Date 01-04-2006 22:01
Thanks Jon,
No it was only a hypothetical,
Regards,
Shane Feder
Parent - By GANESAN NALLATH (*) Date 03-16-2006 15:11
Dear Friends
Pls advise on RT Examination Stage
When RT shall be done?
Is it must be done after PWHT?
Back in my Shop I carry out RT prior to PWHT and
Hardness Test and MPT/LPT after PWHT
Is it acceptable to Code
Parent - - By G.S.Crisi (****) Date 01-04-2006 18:42
If I were the erection contractor or the piping pre-fabricator my attitude would be the following:
1st. I've received a pice of pipe duly identified with a stencil mark from the manufacturer saying that it's a 12 inches Sch 80 pipe. OK, that's taken for granted.
2nd. Any pipe size table says that the nominal thickness of the 12 inches, Sch. 80 pipe is 17.47 mm. So, the nominal thickness of the pipe I've received at site (or in my shop) is 17.47 mm.
3rd. I'm not supposed to measure with a caliper or a micrometer the actual thickness of every piece of pipe I receive at the job site or the pre-fabrication shop. That, as Americans say, is a hell of a job and I'm not going to do it.
4th. So, I'm not going to carry out the PWHT.
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By jon20013 (*****) Date 01-04-2006 19:46
Very good assessment, Giovanni! Happy New Year to you, my friend! I might only add the following to your assessment; likely your QA or QC staff would check all of the documentation and randomly measure these pipes for conformity, depending on one's industry and practices.
Parent - By Fredspoppy (**) Date 01-05-2006 06:54
One thing that I think has been overlooked, is the correlation between the material thickness used during welding of the PQR and what will be qualified for the WPS. Use of 12" Sch80 (17.47mm wall) for the PQR would qualify a material thickness range of 10mm to 34.94mm (2T) for ASME Section IX qualifications (Table QW-451.1). For B31.3 applications, any production welding over 19mm would require PWHT. Therefore, w/o PWHT of the PQR the WPS could only be written for 10-19mm. With PWHT of the PQR the WPS could be written for 10-34.94mm, but PWHT would be required for all production welds made to this WPS.
Parent - - By G.S.Crisi (****) Date 01-05-2006 21:21
Jon,
I don`t know in the USA, but down here in Brazil the inspection firm would send her inspector(s) to the pipe manufacturing plant to check the documentation and make a random measuring of the pipes.
As erection contractor or piping pre-fabricator, what I`d receive is a report signed by the inspector stating that the pipes are in conformity to the purchase order. The documentation remains in possess of the inspection firm.
Of course, if the pipe thickness is within the minimum and maximum tolerances, the inspector will sign the conformity, so, as I`ve said before, I`m not supposed to check again the thickness.
I thank you for your kind words on my person. Happy New Year for you too.
Giovanni S. Crisi
Parent - - By jon20013 (*****) Date 01-06-2006 12:57
Giovanni; in some cases we operate in similar manner in the USA but in many industries an additional verification is performed. In some cases, such as my industry (nuclear) that verification is 100%, in commercial industries it may range from simply accepting the MTR or CMTR to some percentage of verification.
Parent - - By G.S.Crisi (****) Date 01-07-2006 15:31
Jon,
English being not my mother language, I feel free to ask what do MTR and CMTR mean.
Giovanni
Parent - By jon20013 (*****) Date 01-08-2006 10:51
No problem, sorry Giovanni!

CMTR = Certified Material Test Report (typically from producer or supplier for a specific heat or lot of material).

MTR = Material Test Report (typically from supplier or producer for a "standard" mill analysis of a material).
Up Topic Welding Industry / Technical Discussions / PWHT as per ASME B31.3

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