Worm gear actuators are typically used for quarter turn applications e.g., butterfly valves, ball valves, plug valves, dampers and generally incorporate adjustable end stops as well as having the ability to provide a self-locking mechanism.
Worm gear actuators can be used as a manual gearbox as well as being close coupled to multi-turn actuators (electric or pneumatic) for automated operation.
Worm gear actuators can also be used on Weir gate applications offering multi-turn operation, self-locking ability and high ratio.
Other types of applications are as a declutch-able manual override typically used for emergency operation when used with a 90 degree pneumatic actuator when there may be an absence of air supply and the requirement to operate the valve.
To correctly size a worm gear actuator there is some basic information that will be requested.
- Maximum torque the actuator will be required to produce (normally referred to as break torque)
- Valve stem configuration (dimensions such as diameter, drive type, position of keyways etc)
- Keyway position and/or drive orientation e.g., clockwise movement in produces clockwise or counter-clockwise output
- Mounting base configuration, bolt size etc.
- Actuator grade or construction
- Environmental considerations
- Maximum allowable rim pull
Industrial grade are generally for motorised applications, construction features include hardened worm gear for increased cycle life and a motorised flange on the input for Adaptation of an actuator.
Another consideration is for modulating duty which generally incorporates aluminium bronze worm gear. Other types of service are buried or submersible, high and low temperature applications.
Worm gear actuators have a multitude of optional equipment available such as Spur gear attachments, these are generally used to reduce the input torque required and can be used for manual and motorised applications, input stops are generally used on large buried service valves which provide for a positive stop at the input rather than the output or end stops, this protects the equipment from damage due to an over torque condition.
A relatively new addition to protection of equipment due to over torque is the Aunspach Overload protector, this device does not require any adjustment other than setting of torque levels does not require any maintenance and can be used directly onto valve stems.
The Aunspach Overload protector simply disengages and automatically re-engages once the input torque is within the operating limits of the equipment.
Worm gear actuator is available from Acrodyne .