Introduction

The VariStroke-I is a linear electro-hydraulic actuator that utilizes a double-acting

or spring-assist power cylinder with integrated electronic driver module, servo

valve, and redundant MLDTs (Magnetostrictive Linear Displacement Transducer)

– based position feedback sensors to precisely control steam turbine valves. The

actuator’s driver module accepts one or two (redundant) 4–20 mA demand

setpoints and compares these setpoints to the sensed actuator shaft position to

accurately control output shaft position.

The VariStroke-I is factory and/or field configurable via a computer-based service

tool. The actuator’s PCI Service Tool uses a simple user-friendly format to allow

users to easily configure, calibrate, and adjust all internal functions and response

settings. The VariStroke-I also includes a 4–20 mA output channel to indicate

output shaft (control valve) position, and unit alarm and shut down relay outputs

for use as unit health and status indications.

The total installed cost for this fully integrated actuator is low because it has been

completely assembled and tested at the factory. This greatly reduces OEM and

end-user fabrication time, testing time, and site assembly time.