What seat material can be used for cryogenic ball valve in sour service? The temperature range is -198C-32C. Pressure ratings are 150#, 300# ,600# and 900# line. Cryogenic Ball valves are predominantly soft seated, but can be metal. You say sour service but at these temperatures I really don't think it is an issue unless you expect to operate at elevated temperatures for any extended time even at -32C. However that said you obviously want to design for any sour liquids which drop out at the temps and have the body made to suit i.e. Inconel/duplex etc For Low Temp Filled PTFE seats with glass fibre and carbon work well but don't go over 15% glass or you will produce leak paths.For full Cryo Kel-F is by far the best material but increases torque dramatically. Cryo ball valves can expect to be 100-150% more torque than a standard valve so look at the valve stem material as well.You really do not want wind up(as you have an extension fitted)on these shafts/stems or the ball operation is compromised, especially if actuated. A valve actuator could open and close within a very short time and yet the ball will only move a percentage of that operation.Seat design is critical as the material shrinks into the ball, this is true for either metal or soft seated technology. But Soft seated valves for 600 and 900 are only likely to be of small sizes, say 6" and 4" respectively. For larger look at other technology such as triple offset or butterfly.

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