Technical Parameters Parameter Specification Model Fisher 3661 (Various suffixes denote specific types, e.g., 3661L for large displacer) Type Pneumatic Displacer Level Controller Measurement Principle Buoyancy (Torque Tube) Output Signal 3 to 15 psig (0.2 to 1.0 bar) pneumatic, proportional to level Supply Air Pressure 20 psig (1.4 bar) minimum, typically 20-35 psig (1.4-2.4 bar) is supplied. Air Consumption Very low at steady state; typically < 0.1 SCFM (0.17 m³/hr). Mounting Top-mounted (suspended from the top of the vessel). Displacer Length Available in various standard lengths to match the required level measurement span. Process Connections Typically 2-inch NPT or 150# / 300# Flange. Body Materials Cast Steel, Stainless Steel, Alloy Steel Displacer & Torque Tube Stainless Steel (standard), other alloys available for corrosive services. Temperature Limits Standard: -20°F to 450°F (-29°C to 232°C). High-Temp versions available up to 850°F (454°C). Pressure Rating Up to 3000 psig (207 bar) depending on model and torque tube rating.
