Technical Specifications / Parameters Parameter Specification for P163A & P164 Model Fisher P163A (Atmospheric Vent), Fisher P164 (Vented) Type Direct-Acting, Spring-Loaded, Backpressure Pilot Function Controls the upstream pressure of a main pilot-operated backpressure regulator or relief valve. Sensed Pressure Upstream (Inlet) Pressure of the main regulator. Vent Configuration P163A: Vents to Atmosphere. P164: Vents to a separate, lower-pressure vent line. Maximum Inlet Pressure (to Pilot) Up to 400 psig (27.6 bar) for standard models. Set Pressure Range Varies with spring. Common ranges are available from very low pressures (inches of water) up to 400 psig. Supply Pressure Connection 1/4" NPT (This is the loading pressure from the main valve's relay). Sense Pressure Connection 1/4" NPT (Connected to the upstream process pressure). Vent Connection P163A: Typically has a vent screen or open port. P164: 1/4" NPT for connection to a vent header. Diaphragm Material Butyl (standard for natural gas), EPDM, Nitrile. Body Material Aluminum Spring Material Music Wire (standard, with corrosion-resistant coating). Temperature Range -20°F to +150°F (-29°C to +66°C) - standard elastomers.