Hydraulic actuator operated choke
Hydraulic actuators for choke valves are recommended when especially stiffness and high thrust, as well as fast stroking speeds, are required. Hydraulic supply required from external panel. If no external supply available at site, self-contained hydraulic actuator can be used. Hydraulic actuator assembled with positioner, solenoid valve, position transmitter, and other instruments is known as electro-hydraulic actuator.
The operating principle of a hydraulic actuator is the same as a pneumatic actuator. Both make use of the motive force to overcome spring force to move the valve. Hydraulic actuators can be designed to fail-open or fail-closed. Hydraulic piston-type actuator having two types, single acting spring return, and double-acting.
In single-acting actuator, with no hydraulic fluid pressure, the spring force holds the valve in the closed or open position. When the hydraulic force is greater than the spring force, the piston starts the movement. Spring compresses and the valve begins to open or close. On the other hand, as hydraulic oil is drained from the cylinder, the hydraulic force becomes less than the spring force, the piston moves and the valve close or open.
- Electronic positioners with communication protocols - Analog, HART and Foundation Fieldbus with diagnosis features for configuration.
- Fail conditions on the loss of signal failure, hydraulic supply, and power supply - Fail Close, Fail Open and Fail Last.
- Instruments used with hydraulic actuated chokes are certified for all Hazardous Area locations around the globe.