PWHT -PARTIAL PWHT FOR OLD USED VESSEL

Even though you do not require an "R" stamp for this alteration, the National Board Inspection Code (NBIC) has useful guidance. The NBIC is the code that governs the application of the "R" stamp.

1 - RC-2051 states that the test pressure shall be the minimum required to verify the leak tightness integrity of the repair, but not more than 150% of the MAWP on the nameplate. As your repair is virtually a full fabrication of a vessel part, I would recommend the original test pressure per UG-99.

2 - PWHT does have effects on the original part. You can get a sense of what they might be by reviewing the WPS/PQR of the original construction. Every weld procedure qualified to ASME Section IX with PWHT has the weld coupon subjected to the PWHT temperature for a certain time. The actual PWHT time must be less than the qualified time. This qualified time in the WPS/PQR probably will have time enough for 2 or 3 cycles. For a 75 mm vessel, 2-1/4 hours per cycle is the minimum per Table UCS-56, so if the WPS/PQR is qualified for 5 hours of PWHT, your final properties will be OK.

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