Category: Woodward

Features and Benefits

• Special seal design in the main piston valve allows long life and prevents leakage.

• Stainless steel construction ensures valve availability despite corrosive service conditions.

• ANSI Class VI shut-off capability in the reserve flow direction with a pressure differential of 500 psi (3449

kPa).

• Designed for several fuel sources: natural gas, propane, ethane, or methane.

• Closes in <0.100 seconds at 900 psig (6200 kPa).

• Rated at <10 psig (69 kPa) pressure drop at flow of 25.000 lb/h (11.340kg/h)

• Safety Integrity Level: Systematic Capability SC 3 (SIL 3 Capable)

• Up to 50% Hydrogen Compatible.

• Formerly known as the GSOV25-HT

Product Variants

• 24 VDC or 125 VDC Input Voltage Options

• Internal or External Pilot Pressure Options

• Proximity Switch with Normally Open or Closed Contacts

Description

The GSOV50 fuel isolation valve provides shutdown on a gas turbine by rapidly

halting the flow of gaseous fuel. The supply pressure is used to move a spring

loaded piston in the valve. When the valve is energized, gas pressure drives the

spring-loaded piston open, admitting fuel to the turbine. When the current signal to

the electrical solenoid is interrupted, the spring loaded second-stage piston changes

states to vent off primary control pressure. The main spring then forces the primary

piston to the seal, stopping all flow.

Product Variants

• 24 VDC or 125 VDC Input Voltage Options

• Internal or External Pilot Pressure Options

• Proximity Switch with Normally Open or Closed Contacts

Product Specifications

• Gas Supply Pressure: 100-900 psig (690-6200 kPA)

• Fuel Temperature: -4 to +350 degrees Fahrenheit (-20 to +177 degrees Celsius)

• Ambient Temperature: -4 to +250 degrees Fahrenheit (-20 to +121 degrees Celsius)

• Main Seat Forward Leakage: ANSI/FCI 70-2. Class VI

• Main Seat Reverse Leakage: ANSI/FCI 70-2. Class VI, up to 500 psid (3.448kPA) reverse pressure

differential

• Flange: ANSI 600# RF Flange

Applications

The Woodward GSOV50 fuel isolation valve is designed to provide extremely fast

shutoff of gaseous fuel flow to an industrial gas turbine engine. Gas flow is stopped

when the valve is closed, with zero leakage from inlet to outlet. The HT version can

withstand higher fuel temperatures and higher back pressures than the standard version.

It is suitable for operation with gas temperatures between –4 and +350 °F (–20 and +177 °C).

The valve can achieve ANSI Class VI shut-off capability in the reverse flow direction with

a pressure differential of 500 psi (3448 kPa).

The normally-closed valve may be used for emergency and normal shutdown

operations. The special seal design in the main piston valve allows long life and

prevents leakage. Stainless steel construction ensures valve availability despite

corrosive service conditions.

This product is suitable for use on industrial turbines in the 10 to 50 MW power

output range with single or multiple combustion fuel manifold systems.

VariStroke is Woodward’s line of linear electro-hydraulic valve actuators for operation

of steam or hydro turbine control valves. These linear actuators utilize a low-pressure,

hydraulic oil source (typically turbine lube oil) to provide its output shaft force.

Its superb accuracy and resolution make it ideal for steam valve control and related

turbine speed and load control, where turbine up-time and availability is essential.

Features & Benefits

• Precise and stable control for responsive performance

• Variable/configurable shaft lengths for various application requirements

• Patented dirt tolerant and self-cleaning technology for increased reliability

• High-torque valve and motor design (50 lbs chip shear)

• Fast slew rates/times (up to 10”/sec)

• Side-load tolerant for reducing potential oil leaks

• Integrated driver (4-20 mA) and 11-point linearization table

• Self-tuning adaptive control algorithm

Product Variants

• Cylinder Bore Sizes:

100mm (4 in)

150mm (6 in)

200mm (8 in)

250mm (10 in)

300mm (12 in)

• Configuration

Integrated

Remote

Servo Valve Only

• Cylinder – Max. Stroke

100mm (4 in)

150mm (6 in)

200mm (8 in)

250mm (10 in)

300mm (12 in)

• Action:

Double Acting

Single Acting

No Hydraulic Cylinder

• Rod End

Male Thread

Female Thread

No Hydraulic Cylinder

• Fail-Safe Direction:

Extend

Retract

No Hydraulic Cylinder

• Compliance:

ATEX Zone 1

ATEX Zone 2

Side Load Capability

A common problem with turbine actuators is oil leaking from their output shaft due to connection to

valve

rack linkages which have an arc-type of motion. This motion results in side loading of the actuator shaft,

and after long periods may result in shaft-seal wear and resultant oil leakage. Designed for a continuous

side load of up to 10% of actuator output, the VariStroke-II actuator incorporates a high-force precision

bearing and triple-seal technology on its output shaft to solve this typical application problem.

Silt Buster A patented self-cleaning feature that flushes silt and debris from the servo valve. At the interval

and amplitude selected by the user, this function  provides a very rapid motion of the servo valve spool,

allowing any silt to be flushed to the drain passage. This motion is followed immediately by a step of

equal amplitude in the opposite direction. The opposing symmetry of the impulse results in no net

change in fluid volume to the hydraulic power cylinder, and thus does not interrupt the control of the

turbine. This unique feature provides a high degree of stability, reliability, and silt resistance.

Silt Buster

A patented self-cleaning feature that flushes silt and debris from the servo valve. At the interval and

amplitude selected by the user, this function  provides a very rapid motion of the servo valve spool,

allowing any silt to be flushed to the drain passage. This motion is followed immediately by a step of

equal amplitude in the opposite direction. The opposing symmetry of the impulse results in no net

change in fluid volume to the hydraulic power cylinder, and thus does not interrupt the control of the

turbine. This unique feature provides a high degree of stability, reliability, and silt resistance.

Valve Rack Linearization (not currently available)

Because steam flow through single and staged inlet steam valves tends to be non-linear throughout their

flow range, turbine controls must be de-tuned to compensate for instability or sluggish control points

throughout this range. As a way of allowing turbine control optimization without detuning, the

VariStroke-II includes an 11-point linearization table to allow turbine OEMs or users to compensate for

poor valvelinea rization by digitally linearizing the control-to-valve flow relationship.

Side Load Capability

A common problem with turbine actuators is oil leaking from their output shaft due to connection to

valve rack linkages which have an arc-type of motion. This motion results in side loading of the actuator

shaft, and after long periods may result in shaft-seal wear and resultant oil leakage. Designed for a

continuous side load of up to 10% of actuator output, the VariStroke-II actuator incorporates a high-force

precision bearing and triple-seal technology on its output shaft to solve this typical application problem.

The VariStroke-II Actuator offers the following benefits to the user in comparison to other electro-

hydraulic actuators:

Dirt Tolerance

The VariStroke-II actuator is specifically designed for steam turbine applications where turbine lube oil is

also used to power the hydraulic turbine control valve actuator(s). Steam turbine applications can be

extremely challenging for hydraulic control valve actuators as dirt, metal shavings, water, and other

contaminants (Babbitt, ammonia, etc.) are common in such oil systems. Also due to the high

temperatures at which steam turbines operate, turbine oil breakdown is common, resulting in the creation

of a sludge-type substance and the varnishing of internal system components. However, the VariStroke-II

actuator is designed to operate reliably within such challenging applications. Its corrosion-resistant

materials, single moving rotary valve, 610 N (137 lbf) of chip shear force, and self-cleaning port design

allow it to operate in such applications without experiencing undesirable sticking or dragging.

The VariStroke-II actuator is part of a product family with many different models available for purchase

depending on the force, stroke, and redundancy needs. This actuator is available with standard bore

diameters and standard stroke ranges. The VariStroke-II’s unique “variable stroke” capability also allows

users to customize/set the actuator’s exact stroke length in the field to meet their requirement.

The VariStroke-II 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-II also includes a 4–20 mA output

channel to indicate output shaft position, and unit alarm and shutdown relay outputs for use as unit

health and status indications.

The total installed cost for the VariStroke-II is low because it is a fully integrated actuator that has been

completely assembled and tested at the factory. This greatly reduces OEM and end-user fabrication time,

testing time, and site assembly time.

Introduction

The VariStroke-II is a linear electro-hydraulic actuator that utilizes a double-acting power cylinder with

integrated electronic driver module, servo valve, and redundant LVDT (Linear Variable Differential

Transformer) position feedback sensors to precisely control steam turbine valves. The actuator’s driver

module accepts one 4–20 mA position demand and compares it to the sensed actuator shaft position to

accurately control output shaft position.

The actuator’s output shaft position is controlled by a digital controller combined with an integrated

rotary

servo valve that ports supply oil to and from its power cylinder. The actuator digital controller architecture

allows it to perform stable position control during normal conditions, and also respond quickly to desired

valve step changes during system or plant transients. As a means of protecting the turbine, an internal

servo valve return spring forces the actuator to a failsafe position upon any internal unit failure (electrical

input power failure, position sensor failure, processor failure, etc.).

Hydraulic Power Cylinder

The VariStroke Remote Servo can be connected to any hydraulic cylinder,

however; proper operation requires that the VariStroke Stability Equation be

satisfied (see Chapter 2. Stability Specifications). In order to control cylinder

position, the Cylinder must be equipped with a position feedback sensor. The

position sensor must meet the following specifications:

 Output Signal: 4–20 mA

 Input voltage (provided by the VariStroke Circuit Board): 15 Vdc

 Update Rate: ≤1 ms

 Linearity: ±0.04% Full Stroke

 Current Drain: < 100 mA

 Sensor Length must not exceed 2 times the Cylinder Stroke Length

Cylinder Position Control

The cylinder position controller adjusts the hydraulic power cylinder position to

match the feedback signal to the demand.

Both the servo position controller and cylinder position controller are monitored to

ensure accurate tracking.

The position controller regulates a pulse width modulated (PWM) drive signal to

the actuator. The drive current to the actuator is regulated, transiently allowing up

to 10 A to be provided to move the actuator at its maximum speed and torque. A

steady-state current limit becomes active after a period of a few seconds to

protect the actuator and electronics.