Appendix -2 calculation of flange joint

[Bmechz]

Dear all,

Do we have to check the non std. flange in hydrotest condition as per appendix -2 of ASME Sec VIII Div -1? If so PV elite software is taking care of it or not ?

As per my understanding PV elite is taking care of the Shell and Head part during hydrotest. If we model a body flange in PV Elite with Design condition and user defined hydro test pressure design is passed, but in the result no hydro test pressure check is performed.

If we model the same body flange with hydrotest pressure at Atm. temperature as design condition and no hydrotest pressure(allowable stress consider for all parts are 90% of yield stress) , then the flange is failing.

Is it mandatory as per code to check the non std. body flange with hydrotest pressure?


Bmechz

 

[C2it]

Perhaps you should post this question on Intergraph / Coade's website. There is a whole forum for PV Elite there.

 

[TGS4]

Is it mandatory as per code to check the non std. body flange with hydrotest pressure?

In ASME Section VIII, Division 1, there are no requirements for any checks at the hydrostatic test condition. Provided that the design meets the requirements at the design conditions, then it is deemed acceptable at the test condition.

 

[Bmechz]

Dear TGS4

Thanks for your feedback..

In some cases we can found that the bottom head or shell are overstressed due to hydrotest pressure, that is because of the high hydrotest pressure as per client specification(MAP in lieu of MAWP) in div-1.

In general, induced stress during hydro shall not be more than 90% of yield strength of material..

In our design of non std flange, we have used user defined hydrotest pressure which is more than the code requirement and while running flange failed..


Bmechz

 

[TGS4]

In general, induced stress during hydro shall not be more than 90% of yield strength of material..

Such a requirement does not exist in ASME Section VIII, Division 1.

Similar restrictions DO exist in ASME Section VIII, Division 2, but the limit is on the PRIMARY MEMBRANE stress only, not some undefined quantity as "induced stress". In fact, for head, or flanges, the allowable stress basis exceeds the allowable by up to 1.5 times under the design conditions only. This alone would be sufficient, in some materials, to have an allowable for some stress classifications that equals yield.

The sole consideration during the hydrostatic test condition for a flange is that it not leak. There is no consideration provided for stress levels, nor should there be, except insofar as it affects leakage. Furthermore, follow the recommendations in Appendix S. And the guidance in ASME PCC-1.