ASME B16.34 vs API 598

[megero]

Hello!

I am a little confused with ASME B16.34 vs API 598 test procedures. So far I had the idea that the tests specified in ASME B16.34 were OK for 150# lug type butterfly valves. Can anyone tell me what makes a 150# lug type butterfly valve inappropriate for ASME B16.34 procedures (shell test etc) and only suitable for API 598 tests (similar with ASME but longer duration in different sizes)? Is it a metal-to-metal feature or something like that?

Thanks!

 

[terje61]

Hello Megero,

Not completely my field of knowledge, but if I understood correct: ASME B16.34 has no different leakage classes for soft sealed valves and metal-to-metal sealed valves. This often makes it difficult to buy metal-to-metal sealed valves according to ASME B16.34, because they must comply with the more strict rules of soft seal valve leakage. API 598 on the other hand makes a difference and allows more leakage in metal-to-metal sealed valves.

In the end it normally does not make a difference because the metal-to-metal sealed valves will leak anyway.

Additionally it might also be a design issue. ASME B16.34 prescribes minimum wallthicknesses. When selecting a strong material and a thin wallthickness the valve might comply with the API specifications and not with ASME B16.34.

I hope this helps.

M.v.h.
Terje