PWHT

Date 01-30-2011 22:01

I'm an API guy so maybe you can help me out here. According to ASME B31.3 what would be the PWHT requirements for Welds on SCH 40 SA 106 carbon pipe welded with GTAW Root and hot pass SMAW 7018 balanced out. Sprinkler piping 60 psi max operating pressure. My research points to no preheat required since it is less than 3/4" (20mm) in thickness, and that is what I put on my wps and pqr paper work. I got called out on it by the customer's engineer and he wants a separate wps for PWHT and wanted to remind me that PWHT temperatures shall be held for not less than 1 hour. The only thing I can think of is he is using the thickness of a slip-on flange in his calculations or something else screwy. Am I wrong here, it wouldn’t be the first time nor will it be the last. Thanks for any help.

By ctacker (****)

Date 01-31-2011 00:33

Are you confusing PWHT (Post weld heat treat) with Preheat?

By ccbrown (*)

Date 01-31-2011 01:13

Nope, he is talking about post heat.

By Shane Feder (****)

Date 01-31-2011 03:52

ccbrown,
Read B31.3 Clause 331.1.3 (b).
For slip on flanges it is the thickness through the weld in any plane that governs PWHT requirements - not material thickness.
If your weld throat thickness is equal to or less than 16 mm (5/8") PWHT is not required for P1 materials.
Regards,
Shane

By ccbrown (*)

Date 01-31-2011 13:32

Thanks Shane, they are buying me b31.1 and b31.3 this morning.

By joe pirie (***)

Date 01-31-2011 15:13

Just wondering why they would run sa 106 sch 40 on a sprinkler line . usually A53 sch 10
Gtaw on a sprinkler line never seen that neither
Is this a sprinkler system for some kind of special application other than just the normal fire protection in an office building
B31.3 would be a lot of overkill i believe this pipeing is normally B31.9

By ccbrown (*)

Date 01-31-2011 16:39

Lpg off loading station in Canada, we have done a lot of work for this customer in the past and everything they want is always over killed. Good for me the inspector I guess, sometimes

By Joey

Date 02-07-2011 05:03

Hi ccbrown

I agree with Shane that PWHT may not be required as per B31.3. But you may also consider that if this job requires the use of Piping Inspection Code (API570), then you may allow the customer's engineer (or Piping Engineer) to enjoy his privilage :)

Just to remind, API 570 states "Piping Engineer definition - One or more persons or organizations acceptable to the owner or user who are knowledgeable and experienced in the engineering disciplines associated with evaluating mechanical and material characteristics affecting the integrity and reliability of piping components and systems.
The piping engineer, by consulting with appropriate specialists, should be regarded as a composite of all entities necessary to properly address a technical requirement.

Joey