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B31.1 -- Evolution of PWHT Temperature and Thickness Exemption for P-no. 5A Cr-Mo steels

B31.1 -- Evolution of PWHT Temperature and Thickness Exemption for P-no. 5A Cr-Mo steels

B31.1 -- Evolution of PWHT Temperature and Thickness Exemption for P-no. 5A Cr-Mo steels

(OP)
I've just compared the 1977, 2007 and 2014 editions of B31.1, and found changes to the hold temperature and the thickness exemption for P-no. 5A Cr-Mo steel, specifically WP22 (2¼Cr-1Mo).

For those who may be in the know, how did the increase in thickness exemption from 0.500" to 0.625" between 2007 and 2014 come about? Was it a natural evolution, the outcome of accumulated data, or did someone bring their urgent problem to the ASME committee?

BACKGROUND: We plan to weld new fittings into existing 10"Ø 2¼Cr-1Mo piping (in the field; built 1977) that is just under the thickness limit, and as a metallurgist I have reservations about this, especially considering the actual elbow thickness at the weld joint (nominal 0.500") could be closer to the 0.625" limit. PWHT is feasible but awkward in the space we have, as well as adding 3-4 days to the project. All this assumes the original fittings meet the other criterion of 0.15% maximum carbon, which will be confirmed by sampling and testing. On that note, I'd like to know what carbon content a WP22 fitting or P22 pipe typically has these days.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: B31.1 -- Evolution of PWHT Temperature and Thickness Exemption for P-no. 5A Cr-Mo steels

Mostly work performed by EPRI and changes to committee personnel.

RE: B31.1 -- Evolution of PWHT Temperature and Thickness Exemption for P-no. 5A Cr-Mo steels

ironic metallurgist;
Sorry, I did not see the second part of your post. There was a study done for ASME regarding elimination of PWHT for socket welded fittings, which would fit your situation. If I can locate this report, I will send it to you if you can contact me directly. Regarding carbon content, most I have seen has been 0.12%.

Second comment, if one uses elevated preheat, and stringer bead deposition techniques, you can avoid PWHT in P-No 5A base material.

RE: B31.1 -- Evolution of PWHT Temperature and Thickness Exemption for P-no. 5A Cr-Mo steels

(OP)
Thanks metengr,

That this change was due to EPRI work gives me the highest level of comfort.

Still, P22 can be a dangerous material if not handled carefully. The precautions you recommend are already being considered, in addition to a strict moisture control protocol. I also want L grade filler metal used (-B3L).
(Would -B2L filler for the P1 to P5A side of the new fitting be suitable? Creep strength is NOT a criterion at any location.)

A mockup of the joint is planned, simulating the physical space and using the same base and filler metals as used for the job. We will do a postmortem on the resulting weld, including a hardness survey.

I ask about carbon content because I see restricting that as a useful mitigation avenue. Would specifying 0.09% C maximum be unreasonably low?

If the report you mention is by EPRI, I have access and I just need the report number. If not, how would I contact you while maintaining your anonymity?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: B31.1 -- Evolution of PWHT Temperature and Thickness Exemption for P-no. 5A Cr-Mo steels

ironic metallurgist;
There are several EPRI reports and a report attached published by Phil Flenner on relaxation of exemptions for PWHT for P-No 5A base material.

EPRI Report 1019171 Very good summary and test results.

Should you need to talk more or bounce ideas contact me galmetpeatgmaildotcom


RE: B31.1 -- Evolution of PWHT Temperature and Thickness Exemption for P-no. 5A Cr-Mo steels

(OP)
metengr,
Thank you for this excellent information; it's exactly what I was hoping to find. I will be fully armed when discussing this with our contractor.
In our obsession with carbon equivalent, EPRI Report 1019171 is a reminder that hardenability and maximum hardness are not the same thing!

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

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