A516-70N MDMT without impact test in ASME BPVC VIII UCS-66 vs API-650 1

[billbusy]

I have a question, that ASTM A516-70N (Curve D) is good without impact test for 1.25" thick @-30oC per ASME BPVC VIII UCS-66.

But per API-650, ASTM A516-70N belongs to group V and only good for 1.25" @ -11oC without impact test.

It seems API 650 is more strict than ASME BPVC VIII.

Did I have any misunderstanding or can anybody explain the philosophy why API650 seems more strict?

Thanks.

3 years industry experience;
Oil & Gas industry in Canada.

 

[metengr]

According to my Figure UCS-66 ,at 1.25" of thickness, a MDMT below -25 deg F requires impact testing for Curve D steel.

My API-650 2008 edition "Welded Oil Storage Tanks Standard" for A 516 Gr 70, Group V steel, at 1.25" thickness must be impact tested below 12 deg F.

Yes, there is a difference and the reason is because API 650 requires higher threshold impact energy for Group V steels - 30 ft-lbs for 1.5" thick or less versus Section VIII, which requires only 15 ft-lbs at the MDMT.

Each Code or Standard uses different design approaches and conservatisms based on application in service and experience. The user or designer is cautioned for each and the above are minimum requirements.