VariStroke Linear Electro-Hydraulic Actuators for Steam Turbines

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 –

Woodward Vertex Compressor Control

Woodward Vertex Compressor Control

Woodward‘s Vertex Compressor Control product line

The Vertex control product line is designed to control and protect industrial sized axial or centrifugal compressors. This controller includes specifically designed algorithms and logic to start, stop, control, and protect industrial compressors driven by a stationary speed motors, variable frequency drive motors, or turbines. OEM qualified algorithms are used within the Vertex control for straight-through, iso-cooled, double flow, stand alone, and back-to-back compressor applications.

The Vertex controller is field configurable allowing users to configure/select the specific control algorithm required for the specific compressor loop and application. The control’s special stage-to-stage and performance controller decoupling logic allows stable control during normal compressor operation as well as during plant upsets, minimizing process over or undershoot conditions.

Refer to product specification for more information – 03437b Vertex Product Specification

This purpose-built controller has the control, protection, and decoupling logic
required for one or two recycle loop compressor applications. OEM qualified
algorithms are used to ensure that proper start sequences are followed, proper and
accurate compressor load calculations are used, and proper protection and recovery
actions are performed.
Basic functionality includes:

 Motor or Turbine Drive Interface Logic
 Inlet Throttle Valve Control
 Inlet Guide Vane Control
 Recycle Valve(s) Control
 Anti-Surge Control (1 or 2 Recycle Loops)
 Performance Control (suction or discharge pressure or process flow)
 Surge Anticipation Logic
 Surge Protection Logic
 Surge Recovery Logic
 Load Sharing (Parallel compressors, up to five Trains)

Designed to function as a plant DCS node the Vertex controller can be configured to
interface with the plant DCS via hardwired inputs/output signals or serial or Ethernet
communications. With the capability to monitor and control all compressor based
functions (i.e. bearing temperatures, vibration levels, control oil levels, etc.) the
Vertex controller is ideal for use as a cost-effective compressor control/protection as
well as a plant DCS monitoring node.
Designed to replace old obsolete anti-surge controllers, the Vertex can be configured
to function like these controllers but uses faster scan rates, improved surge
anticipation logic, and one integrated package for all control functions (anti-surge
control loop 1, anti-surge control loop 2, and performance control). Also, for load
sharing function, no need for additional Master controller hardware.


The Vertex control is packaged in an industrial hardened enclosure designed to be mounted within a system control panel located in a plant control room or next to the compressor. The control’s user-friendly front panel serves as both a programming station and operator control panel (OCP). This user-friendly front panel allows engineers to access and program the unit to the specific plant’s requirements, and plant operators to easily start/stop the compressor and enable/disable any control mode. The controller’s 8” graphical display allows operators to view actual and setpoint values from the same screen, simplifying compressor operation.
The control’s front panel serves as both a programming station and operator control panel (OCP). Password security is used to protect all unit program mode settings. The controller’s 8” graphical display allows operators to view actual and setpoint values from the same screen, simplifying turbine operation.
Ethernet and serial communications allow users to easily connect the Vertex in to plant or process control system. All controller inputs, outputs, and statuses can be monitored and all start/stop or enable/disable commands can be given through industry standard Modbus TCP or OPC protocols. The Vertex control uses SNTP (synchronized network time protocol) over Ethernet to allow users to synchronize the control’s real-time clock to the plant distributed control system.
Compressor and motor interface input and output-wiring access is located on the controller’s lower back panel. Un-pluggable terminal blocks allow for easy system installation, troubleshooting, and replacement. Optionally users can increase the number of inputs and outputs signals to/from the Vertex control by connecting RTCNet distributed I/O nodes to the controller’s CAN communication ports and configuring the control to use the connected distribute inputs and outputs. The following additional I/O signals can be connected to the Vertex control via CAN communications:

 (16) 4-20mA input channels and (4) 4-20mA output channels (via 2 RTCNet AIO module)
 (8) RTD signals (via 1 RTCNet RTD module)
 (16) Discrete Inputs (via 1 RTCNet DI module)
 (16) Relay output drivers (via 1 RTCNet DO module)
The Vertex controller includes the following PID control & protection functions:
 Performance Control PID
 Performance Limiter PID
 Anti-Surge PID Control
 Rate PID Control
 Boost (open-loop backup line response)
 Surge Recovery
 Surge Minimum Position
 Start, Purge, Stop, Shutdown, & Zero Speed Sequencing Positions
 Alarm & Shutdown Logic
 Load sharing among 5 trains with no additional hardware for Master Controller.
 Easy Load sharing setup. (Plug and Play configuration).

Optionally users can utilize Woodward’s RemoteView software program with the Vertex control to function as a remote operator control panel and or engineering station. This software program once loaded onto a remote computer or touch panel, allows the user to perform all of the Vertex control’s front panel display functions (monitor, operate, tune, and configure) on the respective computer or touch panel. Password based login level security is utilized with this software program to allow users to manage what functions they want the remote panel user to have.

The Vertex controller includes a suite of service tools to allow users to perform the following functions:

 Upload configuration settings files from the Vertex to save on another device
 Download configuration settings files to the Vertex
 Download and view DataLog files
 View real-time or saved trend files