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Moog Servo Proportional Valves

MOOG Servo Valves G631 Series

MOOG G631, MOOG Servo Valve G631
MOOG Servo Valves G631 Series
MOOG Servo Valves G631 Series




Data sheet of MOOG Servo Valve G631 Series


MOOG Direct-Operated Servo Valves G631 Series Description

MOOG G631 Series flow control servo valves are throttle valves for 3 and preferably 4-way applications. They are a high performance, 2-stage design that covers the range of rated flows from 5 to 75 l/min (1.3 to 20 gpm) at 35 bar (500 psi) valve drop per spool land. The output stage is a closed center, four-way sliding spool. The pilot stage is a symmetrical double-nozzle and flapper, driven by a double air gap, dry torque motor.

Mechanical feedback of spool position is provided by a cantilever spring. The valve design is simple and rugged for dependable, long life operation. MOOG G631 valves are suitable for electro-hydraulic position, speed, pressure or force control systems with high dynamic response requirements. 


Welcome inquiry HEASH TECH for MOOG 076 series servo valves! We provide MOOG servo valves to meet with your demand for MOOG hydraulic servo valve and piston pumps. Like as 760, G761, G771, G772, G773, G631, 072, 078, 730, D661, D633, D634, D636, D637, D638, D639,D670, D660, DD791, D792, D680. HEASH TECH meet with your demand for MOOG electro-hydraulic servo valve and MOOG radial piston pump RKP-II, RPK-D, as D951, D952, D953, D954, D955, D956, D957, D958...

MOOG Direct-Operated Servo Valves G631 Series Technical Data


MOOG G631 General Technical Data

Valve design

2-stage, with spool and busing and dry torque motor

Pilot stage

Nozzle Flapper

Mounting pattern

ISO 4401-05-05-0-94

Installation postion

Any orientation, fixed or movable


2.2 kg (4.9 lb)

Storage temperature range

-40 to +60 °C (-40 to +140 °F)

Ambient temperature range

-40 to +135 °C (-40 to +275 °F)

Vibration resistance

30 g, 3 axis, 10 Hz to 2 kHz

Shock resistance

30 g, 3 axis

Seal material

Fluorocarbon (FKM) 85 Shore A
Others upon request

MOOG G631 Hydraulic Data

Maximum operating pressure to ports P, A, B, X

315 bar (4,500 psi)

Maximum operating pressure to port T

20% of pilot pressure, max 100 bar (1,450 psi)

Rated flow at pN 35 bar/spool land (500 psi/spool land)

5, 10, 20, 40, 60, 75

Null adjust authority

Greater than 10% of rated flow

Hydraulic fluid

Hydraulic oil as per DIN 51524 parts 1 to 3 and ISO 11158
Other fluids on request.

Temperature range

-40 to +60 °C (-40 to +140 °F)

Recommended viscosity range

10 to 85 mm2/s (cSt)

Maximum permissible viscosity range

5 to 1,250 mm2/s (cSt)

Recommended cleanliness class as per ISO 4406


For functional safety


For longer life


Recommended filter rating


For functional safety

ß10≤ 75 (10 µm absolute)

For longer life

ß5 ≤ 75 (5 µm absolute)


MOOG G631 Static and Dynamic Data

Deviation of rated flow

± 10% of rated flow

Step response time for 0 to 100% stroke

18 ms


1.0% of rated signal


< 3% of rated signal

Null shift at ∆ T = 38 °C (100 °F)

< 4% of rated signal



MOOG Direct-Operated Servo Valves G631 Series Feature

- 2-stage design with low friction double nozzle pilot stage offers high resolution and low hysteresis in a compact size.

- Rugged, small body size design with a wide range of options is ideal for a wide range of machines

- Integrated fail-safe options enables machine builders to reduce componentry

- Field-configurable 5th port for separate pilot supply offers greater flexibility

- Field-replaceable first stage disc filter for ease of maintenance.


MOOG G631 Series is proven technology that performs reliably in machines where high performance, stability and accuracy are required. Moog Mechanical Feedback Valves are designed to provide high reliability and long service life.



100% factory tested to ensure critical specification performance

Ensures smooth and easy startup, reduces downtime and
insures long life in critical industrial applications

2-stage design

Enables high machine performance, faster cycle times
and greater accuracy - all resulting in higher productivity

Dual Coil torque motor

Redundancy for high reliability

Dual Precision Nozzles in Torque Motor

Precision flow control and predictability

Dry torque motor design

Eliminates potential contamination issues in the air gaps
of the torque motor that could cause machine downtime

Hardened 440C Bushing and Spool

Provides for high life, wear resistance when used in the
harsh environments; provides for low sliding friction
during use

Emergency failsafe positioning

Most valves are set up to return to a failsafe position
when the command signal is interrupted or eliminated

Field replaceable pilot stage filter

Enables preventive maintenance in the field, saving
precious machine downtime and service costs

External null bias adjustment

Enables technicians to manually adjust the null bias of the
valve to adapt to the conditions of the machine (see
section on null flow adjustment – Page 11). This feature
provides a simple adjustment to machine performance
without the need to adjust a controller.


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