Technical Parameters Parameter Specification Model Fisher 644 (Reducing) Fisher 645 (Backpressure/Relief) Type Pilot-Operated Pressure Controller Function Pressure Reducing Backpressure Relief Body Materials Ductile Iron (Standard), Cast Iron, Carbon Steel End Connections Flanged (ANSI Class 150, 300, 600); Butt-Weld Size Range (Main Valve) 1" to 8" (DN 25 to DN 200) Maximum Inlet Pressure (P1) Up to 1440 psig (99 bar) for ANSI 600 models. Outlet Pressure Range (P2) Wide range available via interchangeable pilot springs. Temperature Range -20°F to 150°F (-29°C to 66°C) with standard elastomers. Flow Capacity (Cv) Very high. Example (2" 644): Cv ~ 45
