WOODWARD VariStroke GI single acting electro-hydraulic actuator

The core positioning is a high reliability single acting electro-hydraulic actuator designed specifically for steam turbine valve control, supporting redundant configuration and on-site customization

Application scenarios and core values

（1） Main applications

Control objects: steam turbine control valves, valve racks, trip throttle valves (T&TV)

Adaptation equipment: Mechanical or generator driven steam turbine

Additional scenario: retrofit replacement of old servo systems/manual valves to solve the problems of difficult spare parts and complex calibration

（2） Core values

Safety guarantee: single acting design+built-in reset spring, automatically closes the valve in case of failure, meeting the safety requirements for failure

Convenient operation and maintenance: Factory pre assembly testing, on-site configuration through service tools, reducing installation and calibration time

Environmental adaptation: Anti fouling design is suitable for harsh oil environments, and the ability to withstand lateral loads solves the problem of shaft seal leakage

Flexible adaptation: supports multiple stroke and aperture selections, optional discharge valve configuration, adapts to different valve control requirements

​Product Core Features

（1） Structure and redundancy design

Core structure: Single acting power cylinder (optional internal/external reset spring)+integrated electronic drive module+rotary servo valve+dual redundant MLDT position feedback sensor

Redundancy function: dual 4-20mA demand input (supports single channel/dual channel average/high/low mode), dual MLDT position feedback, can still operate normally even if a single component fails

Configuration method: Connect the computer service tool through the RS-232 interface to configure functions such as travel, linearization parameters, and soft stop on site

（2） Key functional highlights

Anti fouling design: using corrosion-resistant materials, single movement rotary valve, 50 pound chip shear force, and self-cleaning port design, suitable for turbine lubricating oil environments containing impurities and sludge

Side load tolerance: Supports continuous side load up to 10% of the actuator output force, reducing shaft seal wear and oil leakage through high-precision bearings and special sealing technology

Soft stop function: The deceleration point above the valve seat can be configured to slow down the valve closing speed and extend the service life of the valve and valve seat

Quick release valve option: optional integrated Simplex quick release valve (or only reserved port), supporting direct drive of turbine shutdown system to achieve quick pressure relief

T&TV specific configuration: supports lifting commands, partial stroke testing, suitable for trip throttle valve applications, can provide valve position feedback through analog/discrete signals

（3） Product configuration type

Configuration Type Core Features Applicable Scenarios

Single acting integrated power cylinder with compact structure and built-in reset spring for conventional turbine control valve

Single acting remote power cylinder and servo separation installation space limited scenario

Single acting integrated power cylinder with quick release valve and Simplex release valve, regulating valve/T&TV that requires high-speed switching for quick pressure relief

Single acting integrated power cylinder with exhaust valve port reserved exhaust valve interface, supporting high critical applications (requiring dual/triple redundant tripping) with user provided redundant tripping components

Key specification parameters

（1） Performance parameters

Parameter values

Positioning accuracy ± 2% of full range

Positioning repeatability accuracy ± 1% of full range

Temperature drift 0.04%/℃

The built-in reset spring of the fail safe servo valve forces the valve to close

The speed of opening/closing the sled can be configured, with a maximum of 1140mm/s (without discharge valve)

Partial itinerary testing support (T&TV application)

Linearization function supports valve flow linearization table configuration

（2） Physical parameters

Parameter details

Travel range 50.8mm (2 inches), 76.2mm (3 inches), 101.6mm (4 inches), 152.4mm (6 inches), 203.2mm (8 inches), 254mm (10 inches), 304.8mm (12 inches)

Aperture specifications 101.4mm (4 inches), 127mm (5 inches), 152.4mm (6 inches), 203.2mm (8 inches), 254mm (10 inches)

Maximum stall force retraction direction: 2300-14200kgf@34.5bar （ 5080-31300lbs@500psig ）； Extension direction: 2850-17800kgf@34.5bar （ 6280-39200lbs@500psig ）

Installation method at any angle (bolt style and size depend on the model)

Protection level IP66 (IEC/EN 60529)

（3） Environmental and electrical parameters

Category parameter values

Environmental parameters Working environment temperature -40 ℃~+85 ℃ (-40 ℉~+185 ℉)

Working oil temperature+15 ℃~+70 ℃ (+59 ℉~+158 ℉)

The impact resistance performance complies with US MIL-STD-810C method 516.2 (10G peak, 11 millisecond duration)

Anti vibration performance meets US MIL-STD-810F M514.5A (0.015 G ²/Hz, 10-500Hz)

Electrical parameters: Supply voltage 18-32Vdc (steady-state current 2.3A, peak 10A/100ms)

Analog input isolation 4-20mA (input impedance 200 Ω), dual redundancy

Analog output 4-20mA (maximum external load 500 Ω)

Discrete input optical isolation (requires 24Vdc wetting voltage)

Discrete output 0.5A@24Vdc

Service tool port RS-232 communication

（4） Hydraulic parameters

Parameter requirements

Working pressure range: 3.45 bar~34.5 bar (50 psi~500 psi)

Oil type: mineral oil, synthetic oil, or Fyrquel EHC base oil

Recommended maximum oil cleanliness ISO 4406 code 20/18/16 level (nominal 24-40 μ m, β 75)

Recommended oil viscosity is 20-100 centixtles

Interface standard hydraulic ports comply with SAE J518 Code 61

Steady state oil consumption maximum 10.8L/ min@34.5bar (2.8 US gallons per minute @ 500pg)

358L/min at a maximum flow rate of 5.5 bar (95 US gallons per minute at 80 PSI); 929L/min at 34.5 bar (245 US gallons per minute at 500 sig)

Compliance certification

Regional/Standard Certification Content

European (CE) EMC Directive 2014/30/EU; ATEX Directive 2014/34/EU (Zone2: II 3 G Ex nA IIC T4 Gc IP66)

Other European Standard Machinery Directive 2006/42/EC (partially completed machinery); Pressure Equipment Directive 2014/68/EU (SEP category)

International IECEx certification (certificate IECEx 13.0041X, Zone 2: II 3 G Ex nA IIC T4 Gc IP66)

North American CSA certification (Class I, Div.1 Groups C&D T4; Class I, Div.2 Groups A-D T4), applicable to the United States and Canada