Hi Jose,
Strictly as per all design and construction codes as well as the various recommended practices, "PWHT" on grade 91 steel is must after welding.
Off late there had been thoughts to push " Temper bead repair technique in NBIC " by EPRI (Electric Power Research Institute).You may search in google under" temper bead welding on grade-91 steel or other suitable titles" to get more details.
In order to achieve those one has to have "PQR " qualified separately as well as the welding consumables may be different.Which may need some lead time and preparations.
I would think the trouble free option without any prior preparations would be to PWHT the welds.
Please see the link below, whether I' ad posted the link to NBIC document containing an EPRI presentation.
Thanks,
Pradip Goswami, P.Eng,IWE
Welding & Metallurgical Engineer/Specialist
Ontario, Canada
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of José Luís Ferreira
Sent: Friday, May 08, 2015 10:15 AM
To: materials-welding@googlegroups.com
Subject: [MW:23237] Welding P91 without PWHT
Is there an alternative to weld P91 to P91 (Cr-Mo-V) without performing PWHT? I need to weld (repair) small valves (socket welds) in field.
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