3661 Electro-Pneumatic Valve Positioner 4-20mA Input for Control Valves

Product Overview

The  3661 is an electro-pneumatic single-acting valve positioner designed for use with various actuators on sliding-stem valves for throttling applications. It provides a valve position proportional to a standard milliampere DC input signal received from a control device.

The positioner design provides accurate, fast-responding instrumentation able to withstand the vibrations of most plant environments. Low steady-state air consumption contributes to efficient operation. Easily adjustable gain and damping adjustments fine tune the positioner stability to specific application requirements.

The 3661 accepts a standard milliampere DC input signal from a control device and provides split range capabilities and adjustable zero and span. Most parts for 3661 positioners are interchangeable, requiring fewer spare parts to support these positioners. The case and cover are designed to withstand mechanical vibration and rough handling. Zero and span adjustments can be made with the cover in place.

The positioner is used with  657, 667, 1250, 1250R, 3024S, and GX actuators. It can also be mounted on Baumann actuators.

Technical Specifications

Application Industry

The 3661 is used in petrochemicals, power generation, water treatment, paper, and food and beverage industries. It is suitable for throttling applications on sliding-stem valves.

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.

• Poor linear response: 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  3661 is a mature electro-pneumatic positioner platform. For modern digital communication and advanced diagnostics, the  DVC6200 or DVC2000 digital valve controllers are the current-generation alternatives. For legacy installations, the 3661 serves as the electro-pneumatic counterpart to the 3660 pneumatic positioner. For cross-vendor alternatives, verify actuator mounting, travel range, and input signal compatibility before ordering.