Im trying to determine what seat class would be the best to use on a non slam check valve. The service is CO2 on the discharge of a compressor. The design conditions for this valve are 270 F / 1113 psig and will have a max flow rate of 38190 lbs/hr.
API 598 is a common classification making differences between soft sealing and metal-to-metal sealing check valves.
EN 12266 gives different leackage classes.
A metal-to-metal sealing non-slam (nozzle) check valve should guarantee class C in acc. with EN 12266
What style of compressor are you using (reciprocating, centrifugal, etc.)? Gustorf is right on with the API 598 seat leakage classifications for check valves. What size of valve are you looking at using?