Electrohydraulic Power Cylinder

The EHPC is a linear integrating actuator typically used for steam turbine control-valve or valve-rack positioning. This actuator uses a low-pressure (80–250 psi / 552–1724 kPa) hydraulic oil source and then uses three amplification stages to create the required output shaft force. As a custom (made to order) actuator, the EHPC is an actuator that is configured / designed and manufactured specifically for the application.

The EHPC has the flexibility to be ordered with the following configuration options:

  • Single or double acting cylinder action
  • Stroke & cylinder bore options
  • Extend or retract current to position direction
  • Top or bottom mounting attachment
  • Single or dual coil input actuator torque motor
  • With or without return spring
  • 4–20 mA or 0–10 Vdc cylinder feedback signal
  • Optional 1st & 2nd stage oil supply
  • 2nd stage spring bias option
  • 3rd stage spring bias option

This actuator accepts a 0–200 mA (100 mA null, with an optional 15 mA null) input control signal, to position its output cylinder shaft, and outputs a 4–20 mA or 0–10 Vdc servo position indication feedback signal. An integrating actuator driver (such as a MicroNet™ actuator controller module) or an external servo position driver (such as the Woodward SPC servo position controller) is required to drive and position the EHPC.

The EHPC includes electrical position sensing on the output of the large power cylinder—a combination that, when used with a compatible electronic or digital control, results in powerful steam valve movement with pinpoint accuracy. The EHPC is driven by oil pressure supplied by either the turbine’s lubricating-oil supply or from an external independent oil supply and can be operated in any attitude.