I am a little confused when PWHT of clad tubesheets is required or not. We clad P4 tubesheet (~ 100mm) with austenitic steel overlay (SAW)just for welding of tube-to-tubesheet connection (tubes TP 321). There is no service on the clad side of tubesheet!
Q.:Is part UCL (VIII/1)to be considered and PWHT to be done --> UCL-34 with governing thickness --> thickness of base material ~100mm?
Q.: Is it possible that UCL is applicable only if you assume the thickness of weld overlay on the clad tubesheet is considered in your design calculation?

To me it seems over the top. But we bear in mind that we will do that heat treatment for stress-relieving (heat input of the 12mm overlay and residual stress) anyway. So the question is basically a code question only.

Thanks a lot.

I am confused at your questions....but let me try to answer as nobody has responded...you want to know if PWHT is required? and are you looking for the governing thickness used to determine PWHT time?

According to UCL-34(a) and UCS-56, welding to P-No. 4 Gr. Nos. 1 and 2 materials requires PWHT unless exempt per the appropriate note(s) within Table UCS-56.

As to the question regarding PWHT temperature....according to paragraph UCS-56(c) ....When nonpressure parts are welded to pressure parts, the postweld heat treatment temperature of the pressure part shall control.

As for determining the time at temperature, use the overlay weld deposit thickness in determining PWHT time instead of the base material (if that is your question) because the PWHT time is based upon the nominal thickness as defined in UW-40(f) ....[this is stated at the top of the Tables in UCS-56]....this is your weld deposit (clad) thickness...Also, please consult with your Authorized Inspector and/or ASME and consult a metallurgical expert if any disagreement persists.

Also, read the following: http://www.eng-tips.com/viewthread.cfm?qid=134150

My $0.02

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