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P91 Pipe Temporary Weld Question

P91 Pipe Temporary Weld Question

(OP)
Hello All,
We are missing a component that welds in-line on a VPR (vertical pipe rack) module being constructed in the fabrication shop. The component will not available until after the pipe rack is up-ended at site. It is now horizontal and will be shipped that way. ASME B31.1

We want to weld a temporary CS pipe to secure the P91 pipe (24" approx. 1.00" WT) during the up-ending process. Perhaps 4 tacks 4" long @90 degrees. It will be supported otherwise with the permanent support/hangers. After the module is up-ended the spool will be removed and 3" of the P91 pipe will be removed also. After removal of the 3" long pieces we will perform PT on 2-3 inches. That being said:

Is it necessary to preheat per normal WPS?
Is it necessary to do hydrogen elimination (bake)?
Is it necessary to do PWHT?
Is it necessary to do UT?

Personally, I think the 3" will be more than enough to remove the risk of crack migration but with P91 you can't be too cautious. It is quite finicky :)

RE: P91 Pipe Temporary Weld Question

Here is what I would suggest;

Quote:

Is it necessary to preheat per normal WPS?
Yes, per P-No 15E Gr1 WPS

Quote:

Is it necessary to do hydrogen elimination (bake)?
No

Quote:

Is it necessary to do PWHT?
Yes

Quote:

Is it necessary to do UT?
No, but a surface examination like wet MT or PT should be done.

RE: P91 Pipe Temporary Weld Question

Agree with metengr. We once received a similar pipe spool where the attachment weld, not PWHT'd, fractured during shipment within a shipping container.

RE: P91 Pipe Temporary Weld Question

(OP)
metengr and weldstan,

I appreciate the replies.

It's one of those questions that can't be found specifically in the codes (at least I don't think it can) but relies on experience, best practices and common sense...of which you both have plenty.
Thanks again.

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