Working Principle:​ The Hydraulic Amplifier is a linear, pilot-operated, servo actuator. In pressure-input configurations, it works in conjunction with a modified Woodward PG governor. The governor’s hydraulic pressure output (proportional to prime mover load) controls a pilot valve plunger. The pilot valve directs high-pressure oil (from the turbine lube system or external pump) to a servo cylinder, producing the output shaft force. Single-acting or double-acting servo cylinders are available, with return springs providing decrease-fuel forces.

Application Scenarios:​ Mechanical-drive and generator-drive steam turbines, steam turbine control valves, valve rack positioning, turbine speed and load control.