This completely new concept of the relief valve seal construction provides a pressure seal of the seat to the plunger. The sealing pressure increases as the inlet pressure builds up. This is accomplished by the lip on the inside diameter of the seat pressing against the side of the plunger. The seat pressure never goes into balance with the spring load as in conventional relief valves since it does not depend on the spring for the sealing pressure. The contact of the low friction TFE plunger with the TFE seat permits easy ejection of the plunger out of the seat at the preset pressure. Because of the increasing pressure, the valve seals against gases as well as liquids. Chem Flow relief valves are corrosion resistant to all liquids and gases except hydrofluoric acid and hot concentrated caustics. This safety valve is ideally suited for controlling pressures in reactors and vessels of all types where a valve is required to seal against both gases and/or liquids. A simple flange connection is provided for safe venting and after every operation the valve resets without the labor or material cost of a rupture disc replacement. Liquid lines that require excessive pressure protection are also excellent applications. Maximum Temperature: 300°F Thermal Shock: 200°F.