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Minimum Preheat

Minimum Preheat

Minimum Preheat

ASME SA335 F11 (P4) material was welded using 150'F Preheat as per their WPS. However, Code of Construction being ASME B31.3 states a minimum preheat temperature of 250'F shall be applied. There are 700 socket welds completed like this. I recommended Heat Treatment for the welds and Hardness testing to prove the material won't be brittle, but Client isn't buying it. What other options can be done in regards to testing to ensure the integrity of these welds? They are 1-1/4" STD SA335 pipe into Couplings. Are there any exemptions from these minimum preheat temperatures in ASME B31.3, Metallurgists or Wielding Engineers out there, please advise?


RE: Minimum Preheat

Try the ASME section, you will get a better response.
Just make sure you delete this one as people don't like multiple postings.
I will have a look for you now,

RE: Minimum Preheat

Unfortunately JLB it seems you have a rather large problem.
If the 250F was a client requirement and the 150F was a code requirement you may have an escape clause by performing a mock up (new WPS) to satisfy the client but it is highly unlikely the client will accept 700 welds that do not comply with the code.
Did the client review and approve the WPS prior to fabrication ?
Good luck,

RE: Minimum Preheat


The WPS stated a minimum preheat of 150'F Note (6), Note 6 says: "The 150'F minimum specified preheat is the lowest temperature at which this WPS can be used to perform welding. The minimum specified temperature does not imply that the use of minimum permissible preheat is acceptable for all welds on all base material thickness. This WPS is to be used in conjunction with governing codes."

ASME B31.3 Para 330.1.1 states "Unless specified otherwise in the engineering design, the minimum preheat temperatures for materials of various P-numbers are given in table 330.1.1"

Could we not perform the PQR for how it was welded with the 150'F, and prove integrity? Make THIS the engineered design as per para 330.1.1, if it passes?

I am actually a third party trying to help a situation.


RE: Minimum Preheat

That clause "engineering design" relates to requirements over and above the code requirements.
The project specifications and/or engineering design can be as stringent as they want but cannot be less than code requirements.
Bottom line is 250F minimum preheat - anything less and the welds do not comply with the code,

Is there any evidence of what the "actual" preheat was ?

RE: Minimum Preheat

yes. The AI and QA Manager signed off the Data Report at 150F. So the QC. QA Manager. And the Authorized National Board Inspector all missed it. Trying to find a way around cutting out 700 welds. PWHT was my only idea other than the As welded PQR.

Thanks for your help. Let the cutting begin

RE: Minimum Preheat

Blame the welders and fire the engineer responsible for writing the WPS.

The client is in the drivers seat with this. They accept all liability if they accept them as welded. I think you will agree they would be silly to accept them.

Any subsequent post weld heat treatment would violate the WPS if it wasn't qualified using the same PWHT being proposed.

Qualifying the WPS after the fact isn't generally acceptable because it is doubtful anyone can state with any certainty how the sockets were originally welded.

Are there notch toughness requirements invoked for the thickness that was welded? Another fly in the ointment.

I think someone just bought themselves some expensive scrap.

Best regards - Al

RE: Minimum Preheat

I agree with Al - the person who wrote the WPS needs a good kick in the a.. !
The whole reason we give a welder a WPS is to provide guidelines to the welder.

Note 6 says: "The 150'F minimum specified preheat is the lowest temperature at which this WPS can be used to perform welding. The minimum specified temperature does not imply that the use of minimum permissible preheat is acceptable for all welds on all base material thickness. This WPS is to be used in conjunction with governing codes."

How does the welder know what the governing codes require ?

I realise you are a third party and only trying to help - this is not a shot at you.
Just get frustrated with people who write WPS's that look beautiful in a folder in their office but are basically worthless to the welder in the shop / field,

RE: Minimum Preheat

Final disposition was cut and replace. Was worth a shot but after speaking with metalurgists. There's no way of properly determining hardness and toughness inside the joint without destructive testing of 10% or more. Not worth the effort. Thanks for the feedback though.

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