VariStroke Linear Electro-Hydraulic Actuators for Steam Turbines

Woodward solves steam turbine users’ #1 reliability problem . . . dirty oil!

The patented dirt tolerant and self-cleaning technology of Woodward's VariStroke actuators ensure greater overall reliability of your steam turbine. The VariStroke line of linear electro-hydraulic valve actuators operate mechanical-drive or generator-drive steam turbines. These linear actuators 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.

Woodward's quality of design sets a new benchmark in actuator reliability and performance. With its robust shaft and bearing design, the VariStroke actuator surpasses traditional actuators in reliability by eliminating leaks common with base mounted steam valve racks and the associated arc- induced continuous side load on the output shaft. After being tested to over 1 million shaft cycles, with over 1,000 lbs of side force continuously applied to the output shaft, the VariStroke was leak free.

VariStroke's versatile design provides the flexibility to integrate the best solution to fit your turbine application. The actuator design enables users to adjust output shaft stroke range to fit their specific needs. Turbine manufacturers and owners now can easily set maximum stroke position from 50 - 100% of factory listed maximum stroke range, saving time and the cost of modifying expensive valve racks and related linkages.

Solve your reliability problems by putting VariStroke actuators
to work on your steam and hydro turbines........

VariStroke I - Product specification
VariStroke II - Product specification

Contact our Sales Department for more information - pjdiesel@pjdiesel.dk

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