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Preferred Instruments

Preferred Instruments manufactures microprocessor based controllers, instruments, and electric actuators for combustion and process applications. Preferred Instruments also manufactures oil tank gauging and leak detection equipment. A major component of the Instrument group sales is from control systems integration and personal computer based Supervisory Control and Data Acquisition systems. Preferred Utilities' industrial factory is located in Danbury, CT

Model UM, Servo Actuator

The Model UM Servo Actuator provides directly connected and precise modulating control of fuel valves and combustion air & flue gas control dampers. The Model UM Actuator is used on boiler control applications that have a maximum of 720 ft-lbs torque required.

Model UM Servo Actuator Cutsheet

Application

The Model UM Servo Actuator is used on boiler control applications that have a maximum of 720 ft-lbs torque required.

Overview

The Model UM Servo Actuator provides directly connected and precise modulating control of fuel valves and combustion air & flue gas control dampers. The actuator opens, modulates, and closes the valves and/or dampers in accordance with the integrated combustion control and burner management system programs. An integral interlock switch provides proof of open or closed position for safe burner operation. In addition, the feedback potentiometer provides indication of the motor’s shaft position. The UM Actuator is used on boiler control applications that have a maximum of 720 ft-lbs torque required. For heavier-duty service – consult the factory.

Operation: The Model UM Actuator utilizes an instantly reversible motor to rotate a stainless steel output shaft through a reduction of precision worm gears. The output shaft actuates four adjustable cam operated switches: two (2) travel limit switches to stop motor operation at pre-selected positions and two (2) auxiliary switches to provide valve and damper position proving interlocks. The actuator incorporates ‘Built-in Motor Design’, by which the stator of motor is directly inserted into the body housing, which works as a heat sink – efficiently radiating motor heat to atmosphere therefore the actuator can be stopped, started, or instantly reversed at any time within its travel without overheating or loss of power. For maximum durability, all the major parts of the actuator are lubricated with long life di-sulphate molibdenem grease (MOS2) at assembly therefore re-lubrication is in principle not required.

Features

  • 90° Rotary Electric Actuator
  • 72, 140, 280, 430 or 720 ft-lb. Torque Output
  • Designed for Modulation Service
  • Self-locking Drive System to Hold in Last Position
  • Electrically Isolated Feedback Potentiometer Provides Indication of Shaft Position
  • Two (2) Auxiliary Limit Switch Position Output

Power: 120 VAC – 50 / 60 Hz

Ambient Temperature: -13° F to 131°F (-25° C to + 55° C)

Input: Switching SPDT or floating contacts

Torque: 72, 140, 280, 430 or 720 ft-lbs (depending on model selected)

Duty Cycle: 100%

Rotation: 90° in 30 seconds

Feedback Potentiometer: 1000 ohm

Auxiliary Switch: Two (2) Integral SPDT, adjustable

Installation Position: Any

Output Shaft: Stainless Steel (SUS303)

Motor: Reversible, split phase, capacitor type, oil submerged

Enclosure: UM-072, 140, 280, 430 & UM-720: NEMA 4/4X Watertight

Manual Operation: Detachable Crank Handle

Specifications

Provide a separate direct acting Servo Actuator for the fuel gas and fuel oil flow control valves and the combustion air damper. The servo actuator shall modulate the fuel valves without the use of linkage. The actuator shall be totally enclosed in a dust-tight, splash-proof housing, have two (2) integral, snap-action, travel limit proving switches, electrically isolated shaft position feedback potentiometer, 90° rotation in 30 seconds and maintenance-free motor and gear train. The actuator shall be capable of being stopped, started, or instantly reversed without loss of power or overloading. The actuator shall be a Preferred Instruments, Danbury, CT, Model UM-xxx [ ‘xxx’ = 072, 140, 280, 430 or 720 rated torque in ft-lbs].