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Enertech Electro-Hydraulic Operator (EHO)

Developed in 1976, the Enertech Electro-Hydraulic Operator (EHO) supports the needs of emergency and safety systems found in commercial nuclear power plants. These actuators are especially suited for applications requiring quick closing or opening valves where the torque/thrust exceeds the capabilities of typical pneumatic and motor actuators. Enertech EHO’s are commonly used in critical applications such as Main Steam and Feedwater Isolation.

Compact, yet robust in design, the Enertech Electro-Hydraulic Operator eliminates the need for backup power. The linear and rotary actuators have been IEEE qualified to 323, 344, 382 for inside and outside containments. With over 500 installations worldwide the Enertech EHO has been the solution to some of the nuclear power industry’s most demanding applications.


    Key Features and Benefits

    Optimum Deadband Less than 2% of input
    Ideal Input Linearity Less than 2% of ideal total input span
    Adjustable Stroking Speed Up to 10 in/sec or adjustable

    Principles of Operation

    The Enertech Electro-Hydraulic Operator (EHO) uses pressurized hydraulic fluid, directed by electrically actuated solenoid valves, to extend or retract pistons which operate linear or rotary valves.

    A hydraulic pump maintains high-pressure fluid in accumulators which is then used to open, close or modulate valves by directing that fluid to the pistons which are coupled to the actuator which strokes the valve.

    In the event of an accident or loss of power, the stored energy in the accumulator can be used to return the valve to its safe or normal position, or even provide limited operation. The Enertech EHO provides maximum thrust or torque for critical safety applications.

    General Specifications

    • Type: Self-contained Electro-Hydraulic Operator or Gas-Hydraulic upon request
    • Material of Construction: Steel cylinder, stainless steel rod and chrome plated internals, viton elastomeres
    Environmental Ratings:
    • IEEE 382-1980
    • IEEE 344-1975
    • IEEE 232-1974
    Radiation: Total of 192 Mega Rads (100 Mega Rads Normal and 92 Mega Rads Accident)
    Cycle Life: 5,000 (linear) and 10,000 (modulating)
    Normal Accident Temperature: 130° F & 100% relative humidity
    Accident Temperature: 425° F, 66 psig, 100% relative humidity and chemical coolant spray
    Oil: Fyrquel® EHC, Electro Hydraulic Control Fluid
    Control Signal: 4-20 mA (250 ohms resistant) increasing signal open valve
    Power Supply: 460 VAC, 3 PH, 60Hz

    Typical Plant Applications

    Curtiss-Wright Electro-Hydraulic Operators (EHO) support PWR, BWR, and CANDU reactors. Our EHOs are commonly used in:

    • Main Steam Isolation
    • Containment Isolation
    • Feedwater Isolation
    • HVAC Isolation
    • Service Water