Most safety-related applications are simple and straightforward, but require the utmost reliability and surety of closure. An actuator must have the ability to remain open for long periods without binding and then move quickly to the closed position. Although no device is 100% foolproof, a spring is the most desirable closure mechanism.

Mpac: A special version of the Mpac is available for ESD operation. A solid state relay and limit switch replace all controls and electronics. Operating the closure circuit is a spring and normally open hydraulic solenoid. When power is applied, the hydraulic solenoid closes and the motor moves the actuator to the open position. The limit switch cuts power to the relay shutting off the motor. The integral hydraulic valving holds the actuator in place without operating the motor. Removal of the electric power bypasses the valving by opening the solenoid and the spring moves the stem to the failure position.

Complete specifications are listed in the product bulletins:
Mpac, Linear, Rotary & Drive

Additional information on the Mpac:

• STROKING SPEED- Xpac, Mpac
  The tortoise or the hare, both are winners with REXA/koso america inc
• SPRING FAILURE
  Security in the event of a power outage (also see PM21)