Lift Check Valve Lift Check Valve Isha90 (Mechanical) (OP) 29 Jan 18 13:48 Lift Check Valve spring loaded, consider during hydro test crack open pressure was 1 bar, will this pressure change with Air, Stem or other fluids RE: Lift Check Valve LittleInch (Petroleum) 29 Jan 18 14:02 It shouldn't. Liquids though have a greater "shock" value so they might open faster, but normally these types of valves are not good for accurate pressure control. Remember - More details = better answers Also: If you get a response it's polite to respond to it. RE: Lift Check Valve Isha90 (Mechanical) (OP) 29 Jan 18 15:40 So we can say crack open pressure will be same for all fluids, Why does a lift check valve[Metal seated] leak during air seat test when compared to hydro seat. Is there any relation between seat leak & crack open pressure RE: Lift Check Valve zdas04 (Mechanical) 30 Jan 18 16:51 Try to force ball bearings through a sieve. Now try it with flour. Think of your valve as the sieve. It is easier for a gas to find passages than for water to find passages. Pressure is pressure. If I build up enough overpressure upstream of a lift check to overcome spring pressure and the force of the downstream pressure, then the valve will open regardless of the upstream fluid. That is cracking pressure, fluid independent. On the other hand, the check valve staying open is a function of dynamic pressure (since flowing static dP over the distance of the valve seat is infinitesimal). Dynamic pressure has a density component, so fluid species matters in check valve chatter. David Simpson, PE MuleShoe Engineering In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist RE: Lift Check Valve LittleInch (Petroleum) 30 Jan 18 16:59 Good point. In a test the volume capacity of the test fluid can be limited. So to get to 1 bar with liquid it only takes a minute amount of liquid ( literally a few drops) for the pressure to go below 1 bar and the valve reseats. Air is much more compressible so the nuber of bubbles will be much higher.m Why are you so interested? Remember - More details = better answers Also: If you get a response it's polite to respond to it. RE: Lift Check Valve Isha90 (Mechanical) (OP) 31 Jan 18 17:15 Our 1"piston type spring loaded lift check valve with conical metal seat failed during Air seat test & other valve required 2 bar for crack open. How to pass API598 air seat & achieve 1 bar crack open.