MOOG G771K208A Two-Stage Electro-Hydraulic Flow Control Servo Valve

Parameter Name	Parameter Value
Product Model	G771K208A
Manufacturer	MOOG
Product Type	Two-Stage Electro-Hydraulic Flow Control Servo Valve
Actuator Type	Typically torque motor with flapper-nozzle or jet pipe first stage, sliding spool second stage
Rated Flow	Specific to variant (e.g., 5, 10, 20 GPM at 1000 psi drop)
Maximum Operating Pressure	3000 psi (210 bar) or 5000 psi (350 bar), depending on series
Input Signal	±10 mA, ±40 mA, or ±10 V DC (specific to the “K208A” configuration)
Linearity	< ±3% typical
Hysteresis	< 3% typical
Frequency Response (-3 dB, 100% stroke)	50 Hz to 150 Hz+ (depends on specific dynamics)
Null Shift (with pressure & temperature)	< ±2%
Operating Fluid	Mineral oil per MIL-PRF-5606, Skydrol, or other specified fluids
Fluid Temperature Range	-40°C to 135°C (with appropriate fluid)
Electrical Connector	Environmentally sealed connector (type defined by suffix)
Weight	Approximately 1.5 – 3 kg

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Categories: MOOG, TSI

Description

Product Overview

The MOOG G771K208A is a high-performance, two-stage electro-hydraulic servo valve engineered for precise and dynamic control of hydraulic actuators in demanding motion control applications. This specific model represents a sophisticated flow control device that converts a low-power electrical input signal into a high-power hydraulic output, providing accurate modulation of flow rate and direction to hydraulic cylinders or motors. The MOOG G771K208A is designed to deliver exceptional response characteristics, high reliability, and stable operation across a wide range of operating conditions, making it suitable for closed-loop position, velocity, or force control systems. Its implementation is critical in applications where precise motion, fast response times, and high force output are paramount. As a component within Moog’s extensive portfolio of motion control solutions, the MOOG G771K208A exemplifies the company’s legacy of innovation in servo technology, providing the critical interface between electronic controllers and hydraulic power for complex industrial automation, test equipment, and specialized machinery.

Technical Specifications

Parameter Name	Parameter Value
Product Model	G771K208A
Manufacturer	MOOG
Product Type	Two-Stage Electro-Hydraulic Flow Control Servo Valve
Actuator Type	Typically torque motor with flapper-nozzle or jet pipe first stage, sliding spool second stage
Rated Flow	Specific to variant (e.g., 5, 10, 20 GPM at 1000 psi drop)
Maximum Operating Pressure	3000 psi (210 bar) or 5000 psi (350 bar), depending on series
Input Signal	±10 mA, ±40 mA, or ±10 V DC (specific to the “K208A” configuration)
Linearity	< ±3% typical
Hysteresis	< 3% typical
Frequency Response (-3 dB, 100% stroke)	50 Hz to 150 Hz+ (depends on specific dynamics)
Null Shift (with pressure & temperature)	< ±2%
Operating Fluid	Mineral oil per MIL-PRF-5606, Skydrol, or other specified fluids
Fluid Temperature Range	-40°C to 135°C (with appropriate fluid)
Electrical Connector	Environmentally sealed connector (type defined by suffix)
Weight	Approximately 1.5 – 3 kg

G771K201A

Main Function Description

The MOOG G771K208A is engineered to provide precise, proportional control of hydraulic flow. Its operation involves two stages: a first-stage pilot section and a main second-stage spool. A low-power electrical signal energizes a torque motor in the pilot stage. This mechanical motion is converted into a hydraulic pressure differential (via a flapper-nozzle or jet pipe mechanism) that acts on the ends of the main spool. The pressure imbalance moves the spool, which opens precise metering orifices between the pressure (P), tank (T), and control (A, B) ports, allowing high-pressure fluid to flow to the actuator. The spool’s position is proportional to the input current, enabling precise control of both flow rate and direction.

High Performance and Robustness: Designed for demanding duty cycles, the valve offers excellent dynamic response, allowing for rapid acceleration and deceleration of heavy loads. It features low hysteresis and high linearity for accurate positioning. The MOOG G771K208A is built with materials and tolerances that ensure reliable operation in the presence of contamination levels typical of industrial hydraulic systems. Its design often incorporates feedback mechanisms (mechanical or electrical) to enhance stability and performance. The specific “K208A” suffix details its exact electrical characteristics, connector style, and possibly filtration requirements or internal feedback options.

Application Fields

The MOOG G771K208A servo valve is deployed in high-performance motion control systems across various industries. In industrial automation, it is used for precise control of injection molding machines, steel rolling mills, and large robotic manipulators requiring high force and accuracy. For flight simulation and testing, it controls the hydraulic actuators of motion platforms and structural test rigs. In the aerospace sector, it can be found in component test stands and in the control surfaces of large aircraft (though specific aerospace models differ).

The valve is also critical in material testing machines for applying precise, dynamic loads, and in energy applications such as turbine governor controls or wave simulator systems. Essentially, the MOOG G771K208A is suited for any closed-loop hydraulic system where precise control of position, speed, or force with high bandwidth and reliability is required.