A soft seat safety relief valve typically uses an elastomer material, such as Silicone, FKM (Viton™), EPDM (Teflon™), Nitrile (Buna-N) or PTFE as the sealing material in the internals of the valve depending on the compatibility of media flowing through the valve.
Use soft seat valves for superior seat tightness in applications which fall within the soft seat material temperature limitations. Although soft seat valves will typically provide a higher degree of seat tightness than metal seats, Factory Standard does not ensure bubble-tight seats, regardless of seat material.