Varistroke I solves steam turbine users #1 reliability problem...dirty oil!
The patented dirt tolerant and self-cleaning technology of Woodward's VariStroke servovalves ensure greater overall reliability of your steam turbine. The VariStroke line of linear electro-hydraulic valve servovalves operate mechanical-drive or generator-drive steam turbines. These linear servovalves utilize a low-pressure, hydraulic oil source (typically turbine lube oil) to provide output shaft force. Their superb accuracy and resolution make them ideal for steam valve control and related turbine speed and load control, where turbine up-time and availability is essential.
The VariStroke line is configurable via a simple user-friendly, computer-based PC service tool, allowing users to easily configure, calibrate, and adjust all internal functions and response settings. Its integrated driver includes a 4-20 mA output channel to indicate output shaft (control valve) position, as well as unit alarm and shutdown relay outputs for use as unit health and status indications. The 4-20 mA demand inputs and dual-redundant shaft position sensors allow it to continue to operate even with demand input or feedback sensor failures, ensuring extended run-times between forced outages and on-line system repair.
The total installed cost for this fully-integrated actuator is low because it is completely assembled and tested at the factory, greatly reducing OEM and end-user fabrication, testing, and site assembly time. In retrofit applications, the VariStroke actuator can be used to directly replace the existing servo system. This saves costly repairs to existing and aging servos, eliminates the difficulty of obtaining spare parts for obsolete equipment, and reduces calibration time and difficulty.
Two moving parts
50 lb chip shear force
Self-cleaning valve design
Variable / configurable shaft stroke lengths
Fast slew rates/times:
Slew rate up to 762 mm/s (30 inches/second) @ 500 psi supply pressure no load
Precise position control
Triple seal technology
Included valve flow linearization table
Redundant MLDT position sensors
Certified for Hazardous Locations