ASME IX/VIII WPS - PWHT T&T Range Question 2

[MrGezus]

Good afternoon, everyone. So here is it. I'll lay out code requirements and information before getting to my question.
ASME IX
ASME VIII
NACE MR0175
ASME B31.3 (I am shooting to include this as a followed code in the WPS. Not required)

Base Material: P1 G1/2 (Dual Stamped LF1/LF2)

I tested both the as welded and PWHT part of the one coupon. It was cut in half. I had a customer request we do a carbon procedure using SA350 for the -50F impact properties however I figured I would redo one of our ASME VIII vessel procedures at the same time using the PWHT. I know the PWHT is not required but we do some very thick wall items we require it for. All tests were acceptable on both sets of coupons.

My question is about the PWHT time ranges for the WPS. The coupon was 1.5" thick. Table UCS-56-1 Section VIII BPVC states that for something up to 5.0" thick, it needs to be heat treated for 2 hours/in and an additional 15 minutes for each inch over 2. I made an assumption that we would never weld anything over 5".

I heat treated it for 8 hours in case our fantastic welders need to handle up on repairs. I have received conflicting information since then about the time that should be listed on the WPS. Some of our older WPS indicate that I would put 8-10 hours. Others make me lean towards pulling it directly from Section VIII. 1Hr/in 15 minutes minimum... and so on. What I was trying to accomplish was weld>cook>FAIL>reweld>cook>PASS/FAIL...and any way it turned out to be that the PWHT that I chose would be sufficient for that.

QW-407.2 (Section IX) is confusing a bit to me. Does it mean that I can PWHT to a maximum of my chosen PWHT (including the 80%) or does it require me to use my PQR as a minimum? Also, remember both the as welded and PWHT PQRs will fall under one WPS.

Any help would be appreciated.

 

[DVWE]

What you have done is not at all uncommon in the industry. Many fabricators choose to account for weld repairs encountered in production after the initial PWHT that would require an additional PWHT cycle or cycles. In some cases, the end user will also request an additional PWHT cycle for future or field repairs. All these cycles have to be accounted for in the PQR.

What you have established with the 8 hour hold time is your "maximum" time at temperature, and per QW-407.2, that time is 10 hours (10 * 80% = 8). So QW-407.2 accounts for the maximum, not the minimum.

Your WPS can be written to say, "One hour per inch of thickness, 15 minutes minimum for one PWHT cycle. Maximum time at temperature not to exceed 10 hours for any number of PWHT cycles."

It is also not uncommon as a good industry practice, although not required by code, to establish the "minimum" time at temperature. Doing a 1.5" thick coupon PWHT for 2 hours with all the testing is common for establishing the minimum time. This way you are accounting for everything and in between. However, if you choose to do this, your client may hold you to the 2 hrs minimum, regardless of thickness, which is not a bad thing.

 

[MrGezus]

What you have done is not at all uncommon in the industry. Many fabricators choose to account for weld repairs encountered in production after the initial PWHT that would require an additional PWHT cycle or cycles. In some cases, the end user will also request an additional PWHT cycle for future or field repairs. All these cycles have to be accounted for in the PQR.

What you have established with the 8 hour hold time is your "maximum" time at temperature, and per QW-407.2, that time is 10 hours (10 * 80% = 8). So QW-407.2 accounts for the maximum, not the minimum.

Your WPS can be written to say, "One hour per inch of thickness, 15 minutes minimum for one PWHT cycle. Maximum time at temperature not to exceed 10 hours for any number of PWHT cycles."

This is exactly what I thought! The wording could be a bit more precise in my opinion. That is how I have written one before but someone made me question myself. I really appreciate your help, DVWE!

 

[CWEng]

I agree with DVWE. We do the maximum PWHT time as you have done with impacts, then qualify the minimum PWHT time with hardness tests (usually 1 hour in our case, as some NACE and/or API codes require at least one hour anyway.