Product Detail

D638 & D639

Quick Overview


Mounting Surface: ISO 4401 Size 03 (D638)
          ISO 4401 Suze 05 (D639)

Max Pressure: 363 to 5076 PSI (25 to 350 bar)
Rated Flow Rate: 0.5 to 11 gpm (2 to 40 l/min)

The Moog Digital Control Servo Valves (DCV) are closed-loop hydraulic products that are used in industrial machinery to precisely control fluid flow, pressure, position or force using advanced digital fieldbuses for communication (e.g. EtherCAT , PROFIBUS-DP, CANopen) or analog interfaces. The D638 and D639 series are equipped with an integrated pressure sensor in the A-channel as well as a digital pressure controller and are thus a compact pressure control unit.

For maximum flexibility, customers can choose to have an analog interface, fieldbus interface (e.g., EtherCAT, PROFIBUS DP, CANopen) or both combined in the same valve. Whether you need pressure (p) or flow and pressure limiting (pQ) control, this valve series has world-class, proven technology that makes it the performance leader in providing advanced functionality such as higher dynamics, easy parameter tuning and adaptation of flow characteristics.

With a robust design that offers proven reliability in some of the world’s most demanding environments such as oil rigs, offshore wind turbines and steel mills, these valves can be tailored to your exact performance requirements. With proven hydraulic motion control and application expertise, Moog can help you select the version that best meets your needs.

This series also has a version certified for use in potentially hazardous environments (e.g., Explosion-Proof) with hot-swappable connectors and proven ability to withstand vibration and heavy use. Equipment protection with flameproof enclosures “d” and increased safety “e” with marking: II 2G Ex de IIC T5/T4/T3 Gb.

The D638 and D639 Series Valves, sizes 03 and 05 are Direct Drive Servo Valves. The valves are control valves for 2-, 2x2-, 3- and 4-way applications and are suitable for electrohydraulic control of pressure and flow even under high dynamic requirements.

A permanent magnet linear force motor is used to drive the spool. In contrast to proportional solenoid drives, the linear force motor drives the spool in both working directions from the spring-centered middle position. The strong actuating force of the spool, provides Moog Servo Valves with excellent static and dynamic characteristics.

The valves provide full pressure (p) and flow with pressure limiting (pQ) functionality. By using the pQ option of the D638 and D639 series, the control of flow and pressure is possible with just one valve instead of using 2 valves as in the past. The selection of p or pQ control mode can be made via the fieldbus interface.

A built-in fieldbus interface (e.g. CANopen, PROFIBUS-DP or EtherCAT ) enables operating parameters to be set, activates the valve and monitors its performance. To reduce wiring, the fieldbus interface is provided with 2 connectors. DCV's may be integrated into the bus without any external T-joints. In addition, up to 2 analog input commands and up to 2 analog actual value outputs are available. The valves are also available without a fieldbus interface. In this case, the valve is controlled using analog inputs. Valve parameters are set using the integrated M8 service connector X10.

Axis Control functionality can also be added to the valve enabling closing of the external control loop and decentralized control in an automation system, all within the valve device. Data from external sensors can be evaluated by up to 3 analog inputs (V/A), SSI or Wheatstone Bridge.

The pressure control function can be modified by adjusting parameters in the valve software (i.e. linearization, ramping, etc.). Moog Valve and Pump Configuration Software parameters can be saved in different sets for specific tunings.

D368 D639
Rated Flow (Δ 75 psi/5 bar per land) 0.5 gpm 2 l/min 6 gpm 24 l/min
1 gpm 4 l/min 11 gpm 40 l/min
2 gpm 8 l/min - -
4 gpm 16 l/min - -
Max Operating Pressure W 363 psi 25 bar
V 1450 psi 100 bar
U 2320 psi 160 bar
T 3625 psi 250 bar
K 5076 psi 350 bar
Viscosity Range 42 to 1853 SSU at 100 °F 5  to 400 cSt
Temperature Range -4 to +176 °F -20 to +80 °C

Product Specifications