Last week, we shared an educational video about how rotary vane actuators work. Another great video was also just recently released, Electro Hydraulic Operator Bettis EHO Schematic Overview (runtime 2:54).
Like the rotary vane actuator video, this video provides an overview of the principle of operation for Bettis Electro-Hydraulic Operator (EHO). These self-contained actuators are designed to actuate quarter-turn valves to provide fail-safe actuation for Emergency Shut Down (ESD) valves. The Bettis Smart EHO has advanced diagnostic capability and can be connected to DCMlink for remote monitoring.
These actuators are designed as an emergency shutdown actuation solution to stop process flow upon the detection of a command signal or loss of power, protecting personnel, equipment, and the environment.
The video shows an animation of the theory behind 4 modes of operation:
- Valve opening sequence
- Valve closing sequence
- Manual hand pump sequence
- Emergency Shutdown (ESD)
I’ll describe the actions in the opening sequence and invite you to watch the video for the other sequences. In this valve opening sequence, the opening solenoid valve is energized which opens a path to the hydraulic cylinder of the Bettis G-series hydraulic valve actuator and the thermal compensating accumulator.
The accumulator pushes hydraulic fluid through the manifold into the actuator. As this fluid fills the actuator, the pressure in the system drops. When the pressure falls below the pressure switch setpoint, a motor starts operating a gear pump to continue pumping hydraulic fluid.
When the actuator reaches the end of the stroke, the opening solenoid valve de-energizes. The motor continues to operate the gear pump until the accumulator is refilled with hydraulic fluid causing the pressure in the system to rise. When this pressure reaches the pressure switch setpoint, the accumulator is filled, and the motor shuts off. This completes the opening sequence.
Watch the video to see the theory of operation for the other sequences and the components involved in making them happen.
Visit the Hydraulic Actuators section on Emerson.com for more on these and other actuator technologies for emergency shutdown valves to help with continual protection of your personnel, facility, and the environment.
