Loading UG 22 2

[pravin143]

Hello Experts
for U-Stamp vessel design calculation i come across when UG 22(j)ASME Sec VIII-1 loading applicable means for hydro-static test loading, how to satisfy this condition.
Why normally designer check stresses during hydro should not exceed 90% of yield at test temp.

 

[TGS4]

UG-22(j) means that supports (particularly for vessel normally in vapour service) need to be able to withstand thew weight of the test medium.

The reason that designers normally check that stresses are less than a certain amount during the pressure test is that they have a requirement from the purchaser that requires it. Otherwise, there are no limits on stresses in ASME Section VIII, Division 1 during the pressure test.

 

[IdanPV]

ASME Section VIII-1 not fully address this issue.
I think that limit of 90% of yield, which a lot of designers use, came from ASME Section I PG-99.1.

Another option is to use the limits as per ASME Section VIII-2, 4.1.6.2.
Which allows you 95% of yield.
This is appliacble when using ASME Section VIII-1, U-2(g) in conjection with Mandatory Appendix 46.

Since the code does not adress all aspect of design, my opinion is that the 90% yield limit is a good engineering judgment.

 

[pravin143]

Dear IdanPV and TGS4
Thanks for your reply.
i do agree with you but can we go up to 99% if code do not restrict same?

 

[Geoff13]

Since the 90% value is not a Code limit it is up to each Manufacturer to determine what risk they are willing to take.

If you go to 99%, and anything causes the pressure to rise a bit more, there is the possibility of yielding the vessel. As noted in UG-99(d) "... the vessel is subjected to visible permanent distortion, the Inspector shall reserve the right to reject the vessel."

You must determine what risk you are willing to be responsible for. We can't do that for you.