Most manufacturers of rotary electric actuators offer a variety of options to make these work horses even more flexible and valuable in process applications. Here is a review of some of the most common.

Timer Board
A solid state device that allows you to program actuators to automatically instruct valves to operate in repetitive on/off cycles. Programmable to select the length of time the valve will remain "open" or "closed" before automatically cycling to the other position.

Cycle Time Rate Controller
A solid state device that allows you to set the opening and closing speeds of the actuator by setting the pulsing of power to the motor. As electric actuators are geared motors the only way to extend the speed of operation is to use this device.

Positioner
A solid state device that allows you to use an automated valve in throttling applications. Positioner responds to an external input control signal (milliamps (mA), voltage (VDC) or resistive (ohms) and directs the valve to that control position. The operation of the positioner is based on the comparison of two signals; one derived from the "control" input signal and the other from an internal potentiometer that "reads" and matches the valve position versus the input.

Three-Position Control
This option is used with three-position valves to provide an "OFF" position at a given point in rotation (mid-position). May be used with 180- and 90- degree three way ball or plug valves.

Re-Transmitter
Provides a 4-20 mA output signal based on the angular position (rotary) of the actuator. Signal may be connected to local or remote readout terminals.

Mechanical Brake
For secure and instantaneous stopping. Eliminates drifting of valve position due to high flow rates, seat "back-torque" and in modulating service. Should be used with all butterfly valves.

Auxiliary Limit Switches
Additional limit switches may be added to most actuators to provide additional or intermediate contact points for sequencing, isolation or multiple plant-wide indication. Most switches are SPDT 15 amps. See manufacturer for specs and maximum number of switches allowed.

Heater & Thermostat
Provides a controlled means of heating the inside of the actuator enclosure, motor and gear train to protect actuator when installed in extremely cold environments or where humidity is a problem.