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Soft Seats in Acid Gas service

Kabootarman

Mechanical
Jun 14, 2024
5
Hello, we are specifying a modulating pilot psv in acid gas service. H2S range 80%-95%, CO2 range 5%-15%.
I have following questions:

1.) What are the best soft seat materials to specify?
2.) Currently 2 options have been presented from different vendors:
a.) 316SS filled PTFE seats and Aflas seats for main valve and pilot
b.) PTFE seats and seals on main valve and FFKM seal on pilot
Any input for above materials for chemical compatibility and temperature limitations (process and ambient)?
3.) My understanding is that seats seal the ball in a ball valve to prevent leakage into process and seals are meant for sealing stem to prevent leakage to the surroundings, but not sure if its the same logic on pilot psvs, any clarification here will also be helpful.
 
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