Hi,
I am looking for the allowables for the Flange Leakage case for a Blast Case scenario. I have been using 1.5 * MAWP as allowable for the Blast case to be verified against Pd+Peq. for the normal design conditions the allowable the allowables i use is 1*MAWP. Please correct me if my understanding is wrong.

You are very conservative indeed, but not wrong. A far higher stress can be used for blast than would result from 1.0 x MAWP.

Have a look at Norsok L-002 and DNV-RP-D101.

Hi,
Thanks for the reply . I just picked up this 1.5 * MAWP based on some of the extracts from the peng's paper for flange leakage Evaluation.

' API 605 Clearly states that a bending moment capable of producing a longitudinal pipe stress equal to one half of the basic allowable stress is included in the pressure rating at rated temperature '

1.5 * MAWP for blast case sounds quite reasonable for me (atleast for the blast case).

But my next question is .
can i use the same allowable (1.5*MAWP insted of 1.0*MAWP) for Design case Considering the fact that there is sufficient reserve strength in the Flange left to take the moments.

The reason for me trying to find more on Eq Pr method is that its very simple to use in comparison with other methods especially if i want to check more number of flanges.

I am currently having a Pipe spec whose Design pressure is slightly more than the MAWP's for the Flanges. That means every thing fails for 1*MAWP. We can use other methods to qualify but i am checking whats the maximum i can do with Pr Eq method.

If you think 1.5*MAWP is ok, why did you ask the question ?

Use sensible allowable stress values and check your flanges out with ASME VIII Div 2.

It is common to allow at least yield stress and often higher for blast. Some temporary leakage is expected to occur, but the bolts must not break.

The equivalent pressure method is far too simplistic as you are trying to apply it.