- Electric
- The actuator operates the valve using an electric motor driving a gear train
- Electrically driven actuator contain an internal spring to close the valve on loss of electricity
- Motor operated valves
- Rotor, Bettis, Limitorque
- Spring - diaphragm actuators
- Actuation through a diaphragm by low pressure
- Light weight
- Wide range of control applications (on/off and modulating)
- Bettis, Biffi, Limitorque
- Piston - spring return actuators
- Pneumatic actuators with springs oppose the movement of a piston or diaphragm. When the air supply is discontinued or exhausted, the spring extends and drives the piston diaphragm in the opposite direction.
- Commonly used for fail to open and fail to close applications
- Bettis, Limitorque, Biffi
- Piston - springless actuators
- Air or nitrogen is used to pressurize a double acting cylinder. A solenoid valve is used to switch pressure between the cylinders
- Commonly used for fail last position
- Biffi, Limitorque, Bettis
Accesories
- Air Filter Regulator
- Air filter regulators are used to filter and regulate the supply pressure to actuators and positioners (removal of dust particles and water content)
- Booster
- The booster is used in conjunction with a positioner on a throttling control valve to increase stroking speed
- Handwheel
- The handwheel is utilized when pneumatic / electric power is not available for the actuators.
- It utilizes a system of gear multipliers to develop necessary torque to close/open the control valve.
- Limit Switch
- Limit Switches are devices to indicate that the valve cycle has been completed or to indicate the actual valve position
- These signals are also used as interlocks in a control system (For example, locking out a pump until its supply valve has been opened)
- Lock-up relay
- Air Lockup device holds the air in locked condition when the supply air pressure falls below the set value; thereby keeping the control valve in stay-put condition.
- I/P Positioner
- A device attached to the pneumatic actuator, providing automatic modulating control of between the open and closed positions by balancing the air supply to the actuator through the input signal
- The pneumatic positioner is designed to receive a 3 to 15 PSI signal, while the electro-pneumatic is designed to receive a 4 to 20 milliamp signal
- Solenoid Valve
- An electro-magnetically operated valve which enables electrical control of the air supply to a pneumatic actuator
- Travel Stop
- A mechanical device to limit the travel in both direction
- To prevent accidental actuation while the valve is in the open or close position
- Volume Tank
- The volume tank provides the loading pressure for the actuator when supply pressure falls