A131 C - What material group?

[treemkr]

We are making modifications to an existing API storage tank and would like to hot tap 4"-10" nozzles. Drawing indicate material as SA 131 Gr C, but I do not see that listed in the material group tables of API-650. Can someone tell me what group this material would fall into?

Any help would be appreciated.

 

[weldstan]

A-131 is Structural Steel for Ships and is not an "SA" specification. Grade C no longer exists. The A,B grades are low carbon steels and are in Group 1 and II, repectively. Grade C most likely would have been in II.

 

[IFRs]

Back in the 5th edition of API 650, A131-C is listed for a thickness and temperature range that suggests it would be current group III. In the 6th edition A131-C does not appear and A131-CS takes it's place. Your goal is to (1) ensure weldability and (2) determine if the material meets current toughness requirements. Both can be done from a coupon but if you are hot tapping, coupons are not possible. If you decide to go ahead, take the cutout from the first hot tap, get it Charpy tested, analyzed for chemical makeup and weldability so you can develop a proper weld procedure. From the outside, you can do non-destructive Positive Material Identification to get chemistry. How thick is the steel and how old is the tank. Do you have name plate information that tells what API code version it was built to?