Post Weld Heat Treatment of 4130 Material Casing Spool Body

[KnaT]

We have a Casing Spool Body of Material AISI 4130 on which we are to conduct welding repairs followed by PWHT.

Our Client just restricted our Welding Procedure for carrying out the repair because it was approved for only 1 cycle PWHT.

The PQR coupon was Post weld heat treated at 630 deg. C for 4 hours and 45 Minutes.

For pressure vessels we used to decide the PWHT Soak times based on ASME Section VIII Div. 1 or 2 (e.g. 1 hour for upto 25mm thk. and additional time as the thickness increased.) For Soak time mentioned on the PQR we referred to QW 407 and made sure that our soak time of the coupon covered 80% of intended soak time of production welding.

The part under discussion is being governed by API 6A which is just mentioning that the PWHT variables shall be governed by the WPS.

Q: If I am using a WPS with 6 hours of PWHT soak time then am I supposed to PWHT that part for 6 hours regardless of its thickness?

or

Is there a way similar to ASME Sec. VIII Div. 1 for calculating PWHT time required of a specific thickness of API 6A components?

Any guidance in this regard will be more than appreciated.

 

[metengr]

No, the 6 hour soak time is maximum qualified for the WPS. This means you can perform 6, 1 hour PWHT cycles, or 3, 2 hour PWHT cycles, ...you get the idea. The PWHT time is governed by nominal thickness, typically 1 hour per inch of thickness and this is how this should be stated in the WPS.

 

[KnaT]

I'm sorry for the duplicate post. I wasn't sure which forum to post on.

Thank you for the prompt response.

I know that it is roughly 1 hour per inch but I am looking for a specific Code reference for Casing Spool Body of Material AISI 4130 being manufactured as per API 6A.

I've been reading API 6A since morning but couldn't find a thickness to soak time relation anywhere.

I'll really appreciate it if you refer a specific Code or Standard Clause for my guidance.

 

[metengr]

The manufacturer of the equipment supplied under API 6A should provide requirements for PWHT.

 

[KnaT]

I agree that manufacturer has to provide the PWHT requirements but there should be some standard or reference for the manufacturers to follow. Don't you think so?

 

[metengr]

No. The Manufacturer can decide to use either ASME Codes and Standards, EN Standards, ISO or other. My original point was that the manufacturer has the responsibility to ensure PWHT is performed and to their requirements.

 

[KnaT]

Does that mean that we can omit the PWHT altogether if are able to Qualify a welding procedure without it?

 

[metengr]

No.