ASME and DNV supplemental charpy test requirement

[Texan2]

Help! We have almost passed our welding procedure to satisfy DNV and ASME requirements at -50F... but I have to redo the charpy testing. A couple of questions for the welding/ASME/DNV savvy out there:

1. We have a weld procedure that passed most areas: Vickers Hardness, Tensiles, Bends. The problem is that it failed in Charpy testing - in the base metal..*sigh*. Further testing of the base metal revealed it is a poor choice for -50F testing (9/10/10 ft lbs at -50). Funny, the MTR shows 65,68,75 at -50F.. As a result we are getting a new test coupon sent to the lab to confirm its properties BEFORE welding... The question is, can I just do a charpy test on the new coupon, to supplement the original test? Or, do I have to do the entire process over to requalify the PQR and subsequent WPS? It has to satisfy ASME and DNV... The original plate is 2.75" thick. If I can do a supplemental, does it have to be a 2.75" thick plate as well or can I use a 2.5" plate?

2. I used SA-516 Grade 70 (P1 Group2) to SA-516 Grade 70 for the coupons. Can I use SA-537 class1, 2.75" thick, instead - which has bettere impact properties? If I can do a supplemental, does it have to be the same material, or just the same P number and Group number?

3. Finally, I used a 2.75" thick coupon because all 3 welding folks I have talked to cannot agree that a 1.5" thick coupon will qualify up to 8". The production weld is 5" thick, using SA516 Grade 70. Impacts are required (15/12).. Can I do it with a 1.5" thick coupon, or am I limited to 2t?

Thanks in advance!

 

[weldtek]

I can answer your questions relative to ASME Requirements but you'll need to consult the applivable DNV Code.
1. You do not need to re do all of the tests. You may run a supplementary plate and perform charpy tests only. Remember, per ASME the minimum thickness of the test coupon is important. In other words if you run a 1/4" thick test plate and combine the two tests, your qualified range is 1/4" through 8". If you run the test on 5/8" thick or greater your qualified range will be 5/8" through 8". This assumes you don't violate other essential variables ie heat input, and consider certain limitations which pertain to certain processes.
2. P # and Group # are both essential variables for impact tested procedures. You could run a test on P1 Gr 1 to P1 Gr 2 and test both HAZ's & therby qualify both group #'s.
3. I'm assuming you are qualified to 8". Review QW 451 and read al the referenced paragraphs to determine this.