Samson 3730-3 Electropneumatic Valve Positioner HART 4-20mA for Control Valves

Product Overview

The Samson 3730-3 is an electropneumatic valve positioner with HART® communication, designed for attachment to pneumatic control valves. It is a single-acting or double-acting positioner that compares the input control signal from the control system with the actual valve travel or rotation angle, then outputs a corresponding pneumatic signal to the actuator.

The positioner is self-calibrating and automatically adapts to the control valve and pneumatic actuator. It features a calibrated travel sensor without susceptible gears, so it is not affected by mechanical transmission wear. The unit offers four different initialization modes for automatic start-up, including a "Sub" (substitution) mode that allows the positioner to be started up in an emergency while the plant is running without moving the valve.

All parameters are stored in non-volatile EEPROM memory, protected against power failure. The two-wire system has a small electrical load of 410 Ω. The LCD display can be read in any mounting position thanks to a rotatable reading direction. Configuration is handled through a simple one-knob, menu-driven operation, or via PC using TROVIS-VIEW software over the SSP serial interface.

Technical Specifications

Application Industry

The Samson 3730-3 is used in chemical and petrochemical processing, power generation, pulp and paper, and general industrial automation. It is suitable for challenging transit times, challenging ambient conditions, throttling service, and applications requiring an external travel sensor. The integrated EXPERTplus diagnostics enable predictive maintenance for control valves.

Common Problems

• Initialization error: Check supply pressure is within 1.4~7 bar. Verify the travel sensor is properly connected and the valve is not stuck.

• Zero calibration error: The zero point is out of range. Check mounting and re-initialize the positioner.

• Communication status error: Check HART communication wiring. Verify the load resistance is within specification (410 Ω). Inspect for overrun, framing, or parity errors in the communication buffer.

• Positioner does not respond to input signal: Check supply pressure and pneumatic connections. Verify that the device is in the correct operating mode.

• Valve does not reach end position: Verify that the output pressure limitation setting is not too low. Check for air leaks in tubing and actuator.

• Temperature sensor failure: Temperature measurement failed. Accuracy of diagnostics may be reduced. Contact service for replacement.

Replacement Models

The Samson 3730-3 will be discontinued in the near future. The direct replacement is the TROVIS 3730-3, which is the next-generation smart positioner with HART® 7 communication and optimized EXPERTplus valve diagnostics. The TROVIS 3730-3 features a contactless internal position sensor, half the air consumption of previous versions, and uses the same mounting parts as the 373x series. Other models in the series include the 3730-4 (Profibus) and 3730-5 (FOUNDATION Fieldbus). For cross-vendor alternatives, the Neles ND9000 series and Masoneilan SVI-II series are frequently cited as direct competitors.