Fisher 3620J Electro-Pneumatic Valve Positioner 4-20mA for Rotary Valves with Aluminum Alloy Construction

Product Overview

The Fisher 3620J is an electro-pneumatic valve positioner designed for use with diaphragm or piston rotary actuators. It consists of a 3610J pneumatic positioner combined with a 3622 electro-pneumatic converter. The converter receives a 4-20 mA DC input signal and produces a proportional pneumatic output (0.2 to 1.0 bar / 3 to 15 psig) that drives the pneumatic positioner stage.

The 3620J is a single-acting positioner that mounts integrally to the actuator housing. The action can be switched between direct and reverse in the field without additional parts. Zero, span, and crossover adjustments are easily accessible with a screwdriver after removing the cover. A small adjustable loop gain allows fine-tuning for each specific actuator size and application to optimize dynamic response.

The positioner provides accurate, fast-responding operation and withstands vibrations found in most plant environments. Supply pressure changes have minimal effect on positioner operation. The case, components, and gasket materials are selected to withstand harsh environments, with low copper aluminum alloy die castings for corrosion resistance. Positioner bleed air purges internal parts and the actuator housing for additional protection.

Technical Specifications

Application Industry

The Fisher 3620J is used in chemical and petrochemical processing, power generation, water and wastewater treatment, and general industrial process control. It is suitable for older pneumatic control loops and applications where reliable rotary valve positioning is required. The positioner mounts integrally to the actuator housing for a compact installation.

Common Problems

• No output signal with input present: Check for clogged nozzle. Clean the nozzle. Check air supply pressure.

• Slow or abnormal output pressure: Check supply pressure is within specification. Check the pneumatic amplifier and nozzle/flapper assembly.

• Linear response poor: Check the zero spring adjustment. Check the range adjustment mechanism position.

• Positioner does not respond: Verify supply pressure and pneumatic connections. Check that the converter is receiving the 4-20 mA signal.

• Air leakage: Check O-rings, gaskets, and diaphragm for wear. Replace as needed.

Replacement Models

The Fisher 3620J is a mature electro-pneumatic positioner platform. For modern digital communication and advanced diagnostics, the Fisher DVC6200 or DVC2000 digital valve controllers are the current-generation alternatives. For legacy installations, the 3620J serves as a direct replacement for the 3610J pneumatic positioner when electrical input is required. The 3620JP adds a position transmitter, and the 3620JPR adds remote mount capability. For cross-vendor alternatives, verify actuator mounting, travel range, and input signal compatibility before ordering.