Digital guide
You are here:
Woodward 9902-450
Product Name: Remote Servo & Ram
Product Introduction: The 9902-450 is classified as a Remote Servo & Ram within the Woodward VariStroke electro-hydraulic actuator family. It provides remote-mounted hydraulic cylinder actuation for precise linear control of turbine valves and associated equipment.
Detailed content
Technical Specifications:
-
Component Classification: Remote Servo & Ram
-
Product Family: VariStroke electro-hydraulic actuator series
-
Linearity: ±1.0% of full range
-
Repeatability: ±0.5% of full range
-
Temperature Drift: 0.04%/°C
-
Open Slew Rate: >200 mm/s (8 in/s)
-
Close/Trip Slew Rate: Up to 254 mm/s (10 in/s)
-
Stroke Lengths: 50–457 mm (2–18 inches), configurable
-
Available Bore Sizes: 102, 152, 254, 305 mm (4, 6, 10, 12 inches)
-
Max Stall Force: 450–18,000 kg @ 35 bar (1000–40,000 lb @ 500 psi)
-
Cylinder Type: Double-acting
-
Failsafe: Internal return spring on servo valve
-
Visual: Integrated stroke gauge
-
Mounting: Any attitude (bolt patterns model-dependent)
Functional Features:
-
Closed-loop position control with LVDT feedback
-
Computer-based service tool configuration via RS-232
-
Linearization table for valve flow characterization
-
Double-acting cylinder with model-dependent failsafe direction
-
Integrated stroke gauge for visual position indication
Application Scenarios: Steam turbine main steam valve and control valve linear positioning, turbine bypass valve control, compressor anti-surge valve control, and legacy servo system retrofits.
Structure & Materials: The actuator integrates a hydraulic power cylinder, servo valve, and electronic driver in a unified package. The servo valve features an aluminum case with through-hardened stainless steel internal parts.
Working Principle: A hydraulic pump provides pressure to the servo valve. The electronic driver receives a position command and compares it with LVDT feedback, driving the servo valve to direct hydraulic flow into the cylinder and achieve the target piston position in a closed loop.
Installation Requirements: Install per Woodward VariStroke manual. Hydraulic ports marked “ROD” and “HEAD” connect to corresponding actuator ports. Use kit 8924-874 when mounting servovalve directly over pump. Filters and screens must be in place to prevent contamination.
Usage Notes: The actuator must be totally independent of the prime mover control system for overspeed protection. Wear appropriate PPE. Follow ESD awareness procedures when handling electronic components.
