Description
1. Overview
Moog G771K201 is a two-stage mechanical feedback electro-hydraulic flow control servo valve of MOOG G771 series. Adopting a nozzle-flapper pilot stage plus main spool configuration, it is a high-performance analog electro-hydraulic servo control component.
The servo valve precisely converts weak electrical control signals into adjustable hydraulic flow to realize closed-loop position, velocity, pressure and force control of hydraulic cylinders or hydraulic motors. It serves as the core actuator for high-end electro-hydraulic control systems.
It conforms to ISO 10372 standard mounting dimensions and is suitable for 4-way hydraulic circuits. Featuring high dynamic response, low hysteresis and high resolution, it can withstand long-term high-pressure and high-frequency cyclic operating conditions. Widely applied to material fatigue test machines, hydraulic servo presses, flight simulation equipment, metallurgical rolling mills and precision test platforms. It is used for spare parts replacement of legacy servo systems, equipment overhaul, construction of high-precision hydraulic production lines and control system upgrades.
Two-Stage Nozzle-Flapper Structure with Excellent Dynamic Response
Equipped with dry torque motor and double nozzle-flapper pilot control, matched with precision lapped main spool. It delivers sufficient output thrust, fast step response and wide frequency bandwidth. It can rapidly follow control commands, effectively reduce system phase lag, guarantee dynamic accuracy of closed-loop control systems and meet the demands of high-speed alternating load conditions.
High Control Accuracy and Superior Linear Characteristics
The precision-lapped spool offers good flow linearity, low hysteresis, high resolution and controllable null drift. An adjustable null offset mechanism is integrated inside the valve for on-site null calibration. Upon power failure, the spool automatically centers with fail-safe characteristics to prevent uncontrolled motion and greatly improve overall equipment safety.
Strong Condition Adaptability and Robust Durable Structure
Modular reinforced overall structure with outstanding vibration and shock resistance, permitting mounting in any orientation. Compatible with various qualified working media including mineral hydraulic oil and phosphate ester. Sealing components feature wide temperature resistance and corrosion resistance, adapting to wide temperature range and continuous cyclic operation with slow performance degradation over long-term service.
Standardized Mounting with Strong Replacement Compatibility
The mounting surface complies with ISO 10372-02-02-0-92 specification with unified port layout and mounting hole positions. The electrical interface adopts a standard aviation connector, directly compatible with mainstream servo amplifiers and motion controllers. New and old models of the same specification are directly interchangeable without modification to integrated manifolds and control programs, facilitating maintenance and retrofitting.
Low Internal Leakage and Stable Flow Gain
Symmetrical port design delivers consistent forward and reverse flow characteristics with controllable steady-state internal leakage. The flow gain remains stable and less affected by supply pressure fluctuation, ensuring process repeatability during long-duration testing and mass production and reducing system control drift.
Comprehensive Application Envelope and Diverse Customized Versions
Optional derivatives include intrinsically safe explosion-proof type, magnetic null adjustment and vented motor caps for hazardous areas, special media and low/high temperature special conditions. Multiple electrical wiring modes including single coil and parallel coil are supported to match different driver amplifier output specifications.
3. Technical Specifications
1. Basic Parameters
Model: G771K201
Brand: MOOG (Original, USA)
Series: G771 Series Two-Stage Electro-Hydraulic Servo Valve
Valve Size: Size 02 (ISO 10372-02 standard mounting)
Valve Configuration: Two-stage, nozzle-flapper pilot, mechanical feedback 4-way flow control servo valve
Core Functions: Electrical signal – hydraulic flow conversion; closed-loop position / velocity / force / pressure control
Applicable Circuits: 4-way hydraulic circuit preferred, also available for 3-way control
Net Weight: Approx. 0.86 kg
Application Scenarios: Material test equipment, servo hydraulic presses, aerospace simulation testing, metallurgical servo systems, precision automated hydraulic platforms, spare parts maintenance & replacement
2. Hydraulic Performance Parameters
Maximum Supply Pressure: 210 bar (3000 psi)
Maximum Return Line Pressure: 210 bar
Recommended Fluid: Industrial hydraulic oil complying with ISO 11158; recommended fluid cleanliness ≥ NAS 1638 Class 6
Kinematic Viscosity of Fluid: 10～97 mm²/s
Fluid Temperature Range: -40℃～+135℃ (with corresponding sealing materials)
Rated Flow: Standard flow rating for G771K201 (calibrated at 35 bar pressure drop across single metering edge)
Null Adjustment: External screw adjustable null offset
3. Electrical Performance Parameters
Drive Mode: Analog current signal drive (single coil)
Standard Input Signal Range: 8～200mA (subject to coil configuration)
Wiring Interface: Standard multi-pin aviation connector
Protection Features: Auto centering upon de-energization; reverse polarity protection available as option
4. System Compatibility Parameters
Mounting Method: Manifold subplate mounting, any mounting orientation permitted
Manifold Requirements: Flatness of mounting plane ≤0.05mm/100mm, surface roughness Ra≤0.8μm
Operation Mode: Supports long-term continuous operation and high-frequency reciprocating alternating conditions
Compatible Equipment: MOOG servo amplifiers and mainstream third-party analog servo controllers
5. Environmental Parameters
Operating Ambient Temperature: -40℃～+135℃
Storage & Transportation Temperature: -40℃～+85℃
Operating Humidity: 5%～95% RH, non-condensing, no corrosive gas
Vibration Resistance: 3-axis 10Hz～2kHz, withstand 30g vibration; Shock resistance: 30g
Protection: Standard protection for electrical connector; avoid long-term direct water spray
The Moog G771K201 servo valve realizes precise control following the sequence: Torque Motor Electro-Conversion → Nozzle-Flapper Pilot Regulation → Mechanical Feedback Closed Loop → Main Spool Flow Regulation.
Current output from the control amplifier drives the torque motor and deflects the flapper, changing differential pressure between the two nozzles to displace the main spool via pilot control. Spool displacement is fed back to the flapper through a mechanical feedback rod to form an internal closed loop until the spool position matches the input signal.
Spool displacement determines the flow area of each working port, outputting hydraulic flow proportional to the control signal to drive the actuator. When the input signal returns to zero, the spool automatically centers by the feedback mechanism to cut off load oil passages. Continuous flow regulation enables high-precision motion control of the actuator with adjustable null position, ensuring steady-state accuracy of the closed-loop system.
Supporting Equipment for Material Mechanics Testing
Deployed on fatigue test machines, tensile testers and impact test benches to realize high-precision closed-loop force and displacement control, guarantee repeatability of test curves. It is a mainstream servo control component in material inspection industry.
Precision Servo Hydraulic Forming Equipment
Used for servo hydraulic presses, injection molding hydraulic units and sheet forming equipment to accurately regulate pressure and motion speed, improve forming consistency and reduce reject rate.
Aerospace Simulation & Test Platforms
Actuator systems of flight simulators and component environmental test benches rely on superior dynamic response to reproduce actual load conditions and satisfy stringent control indicators of high-end test equipment.
Servo Control Systems for Metallurgical Rolling Mills
Applied for automatic gauge control (AGC) and deviation correction hydraulic circuits of rolling mills to continuously and steadily adjust roll gap and tension, adapting to non-stop production of continuous production lines.
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