Applications: Used in Systems to Maintain a Desired Vacuum Level, Relief Valves are Proportional - Not “Pop” Type Safety Valves Not Preset - Field Adjustable, Knurled Adjustment Screw and Locked with Jam Nut, Pressure Range: 0-27” Hg, Temperature Range: -65°F to 250°F Construction: C360 Machined Brass Body, Stainless Steel Spring, Piston and Seal, Ever seal 483 Sealant Standard.