Maximum hydrotest pressure on convex side of head

[jtseng123]

Dear all,

I have an internal elliptical head separating two independent vessels. Hydrotest will be done separately.

Diameter 4000 mm, internal head thk 50 mm

To determine the maximum hydrotest pressure on the convex side, I believe the allowable compressive stress has to be determined first.

Can 2B x 90% from UG-28 (c)(2) Step 3(b) be used as the maximum allowable compressive stress (the same concept for tension during hydrotest: 90% of the yield), and then plug into UG-33(d) to determine the maximum hydrotest pressure on convex side ?

UG-28 (c)(2) Step 3(b) saying yield stress is twice the B value and with D/t<10 cylindrical shell. It does not say it can be applied to head. If it can not be used, what is the right approach to determine the maximum hydrotest pressure on convex side ?

 

[r6155]

How did you established 50 mm?
Read UG-99 (e.
Regards
r6155

 

[TGS4]

In order to calculate the head thickness in the first place, as asked by r6155, you needed to wind your way from UG-33 to UG-28(d). UG-28(c) is not going to be appropriate.

Unfortunately, you can't use the same concept as tension in hydrotest, because the failure mode is not plastic collapse, but buckling. The question is really, what is the design margin required during the hydrotest against buckling failure. With UG-99(d) telling you that there is no criteria in VIII-1 for maximum hydrotest pressure, that means that there is no criteria on the buckling account.

So, either ask you client or test at the bare minimum per UG-99(e).