Hydrotest cap evaluation 1

[GRoberts]

We are manufacturing fittings which have to be hydrotested. On previous projects, our customer has specified to use A234 WPB weld on pipe caps with a 40 ksi min yield. The fitting we were manufacturing had either a 36 or 50 ksi yeild, but on the most recent project, the yield strength of the fitting was increased to 60 ksi. So now the fitting has a 14" O.D., and a 12.75" I.D. Will a WPB 14" Sch 80 weld cap machined down to match the 12.75 ID of the fitting be safe under a 3350 PSI hydrotest? What is the formula used to figure the stress on a pipe cap?

Thanks in advance.

 

[MJCronin]

Groberts,

I believe that you can use the "test to failure" rules of the ANSI B16.X ? rules. ( I think it is B16.9...)

Using the same acceptance criteria used by the manufacturers of piping "tees", "elbows" and other components, you are allowed to claim that your component is acceptable if it can be hydrotested to the criteria in B16.9.

Without a testing/qualification program, I suggest that you look at the rules contained within ASME VIII, Divison I for qualification of ellipsoidal pressure vessel heads.

I believe that your "pipe cap" geometry is identical to this type of head ( but you must verify this...)


Hope that this helps


MJC