KOSO EP800 Analog Valve Positioner with 4-20mA Input for Pneumatic Control Actuators

Product Overview

The KOSO EP800 is a pneumatically driven valve positioner that accepts a 4-20mA DC command signal and produces a proportional air output to operate a control valve actuator. It continuously monitors actuator displacement and feeds the position back to the control loop, ensuring the valve opening matches the input signal. The EP800 family covers both single-acting and double-acting actuator types. Three configurations are offered: EPA800 for single acting, EPC800 for double acting, and EPB800 for the 5200LA actuator. A non-bleeding pilot valve minimizes steady-state air use. Conversion between single-acting and double-acting operation, as well as between direct and reverse action, is straightforward. Split-range control is available through span and zero adjustment, with ranges of 4-12 mA and 12-20 mA DC. The aluminum alloy housing comes in weatherproof, explosion-proof, or intrinsically safe versions. Popular configurations are stocked for immediate shipment.

Technical Specifications

Application Industry

The KOSO EP800 serves power generation, petrochemical, chemical processing, and general industrial automation. It is used to position pneumatic actuator-operated control valves within process control loops. Both straight-stroke and angular-stroke actuators are compatible.

Common Problems

• Positioner does not respond to input signal: Check supply pressure is within 140~700 kPa. Verify pneumatic connections are secure. Check the pilot valve for blockage.

• Valve position does not match input signal: Check zero and span calibration. Verify that the action direction (direct or reverse) is correctly set. Check that the feedback linkage is properly connected.

• Erratic operation or oscillation: Inspect for air leaks in tubing and fittings. Check for excessive friction in valve packing or actuator. Verify the air supply is clean and dry.

• Split range not working: Verify span and zero adjustment for the desired split range (4-12 mA or 12-20 mA DC).

• Air leakage from positioner: Check the pilot valve and diaphragm for wear. Inspect the O-rings and seals.

Replacement Models

The KOSO EP800 is a mature electro-pneumatic positioner platform. The KGP5000 series is the smart valve positioner alternative from the same product line, offering digital communication and advanced diagnostics. For cross-vendor alternatives, verify actuator mounting, travel range, and input signal compatibility before ordering.