D634‑1005 is a high‑performance direct‑drive servo valve (DDV) from the MOOG D634 series, intended for closed‑loop electro‑hydraulic control. It uses a permanent magnet linear force motor to directly drive the spool, with integrated LVDT closed‑loop position feedback and built‑in 24 VDC PWM electronics. The valve meets ISO 4401 Size 05 (NG10) mounting standards and is designed for precision flow, pressure, and force control in demanding industrial applicationsMoog Inc..

D634 stands for the series: ISO 4401 Size 05, direct‑drive, integrated 24 VDC electronics, analog interface. The suffix 1005 defines coil parameters, LVDT range, seal material, electronic gain and offset settings specific to this configuration.

Single‑stage direct drive eliminates the need for pilot supply and improves contamination tolerance. Pressure‑independent dynamics ensure consistent speed and response regardless of system pressure. Integrated EMC‑compliant 24 VDC electronics simplify installation and reduce external components. Spring‑centered fail‑safe design returns the spool to neutral when power is removed, stopping the actuator. Low hysteresis, high resolution, and good repeatability support precise closed‑loop controlMoog Inc..

Suitable for injection molding, blow molding, die casting, hydraulic presses, metal forming, fatigue test systems, and general industrial servo‑hydraulic installations requiring high dynamic performance and reliabilityMoog Inc..

Mounting pattern complies with ISO 4401 Size 05 (NG10). Maximum operating pressure for ports P, A, and B is 350 bar (5,000 psi). Port T pressure is limited to 50 bar (725 psi) without the external drain port Y, or 350 bar (5,000 psi) when port Y is connected. Rated flow at Δp = 35 bar per land is 60 to 100 L/min (15.9 to 26.4 gpm). Maximum flow is approximately 185 L/min (48.8 gpm). Internal leakage is ≤ 0.8 L/min. Operating fluid is mineral oil per ISO 11158 or DIN 51524 parts 1–3. Recommended viscosity is 15 to 100 mm²/s; allowable range is 5 to 400 mm²/s. Fluid temperature ranges from −20 °C to +80 °C. Minimum fluid cleanliness is ISO 4406 18/15/12; 17/14/11 is recommended for longer service lifeMoog Inc..

Step response time for 0–100% stroke is typically 20 ms. Hysteresis is less than 0.5% of full scale. Threshold (resolution) is better than 0.1% of full scale. Null shift over ΔT = 55 K is less than 2%. Frequency response at −3 dB is 80 Hz or higher (typical)Moog Inc..

Supply voltage is 24 VDC, operating range 18 to 32 VDC. Maximum current consumption is 2.2 A. A 2.5 A slow‑blow external fuse is recommended. Command signal options are ±10 V, ±10 mA, or 4–20 mA, selectable via internal jumper. Input impedance is >100 kΩ for voltage signals and 50 Ω for current signals. A spool position monitor output is provided as standard. Connector is 6+PE (M18) with IP65 protection. Ambient temperature ranges from −20 °C to +60 °CMoog Inc..

An analog command signal (±10 V, ±10 mA, or 4–20 mA) is sent to the valve’s integrated electronics. The electronics drive a permanent magnet linear force motor to move the spool away from its spring‑centered position. An LVDT sensor measures the spool position and feeds the signal back to the control electronics. The electronics compare the command with the feedback and adjust the motor drive to achieve precise spool positioning. Spool displacement regulates flow direction (A→B or B→A) and magnitude to the hydraulic actuatorMoog Inc..

Mount the valve on a clean, flat surface according to ISO 4401 Size 05. Use the supplied O‑rings for port sealing. Tighten M8 mounting bolts to 8–10 Nm. Avoid mechanical stress, misalignment, or impact loads during installationMoog Inc..

Port P is pressure supply, port T is tank return, ports A and B are work ports, and port Y is an optional external drain. Flush the hydraulic system to ISO 4406 17/14/11 cleanliness before installing the valve. If used, route port Y directly to tank without backpressureMoog Inc..

Pin 1 is +24 VDC, pin 2 is 0 VDC (GND), pin 3 is command signal (+), pin 4 is command signal (−), pin 5 is enable (optional), pin 6 is spool position monitor, and PE is protective earth. Use shielded twisted pair cables for signals; connect the shield to 0 V at the power supply side and to the connector housingMoog Inc..

Before power‑up, verify all mechanical, hydraulic, and electrical connections. Confirm fluid level and supply voltage within 18–32 VDC. Apply 24 VDC power; the valve initializes and performs an LVDT self‑test. Select the desired command signal type (±10 V, ±10 mA, or 4–20 mA) using the internal jumper. With zero command applied, adjust the null potentiometer for minimum internal leakage. Apply step commands at 10%, 50%, and 100% of full scale to verify smooth response, correct direction, and stable operationMoog Inc..

A 0 V, 0 mA, or 12 mA command centers the spool with no flow. A +10 V, +10 mA, or 20 mA command delivers full flow from A to B. A −10 V, −10 mA, or 4 mA command delivers full flow from B to A. The monitor pin outputs a 0–10 V signal proportional to spool stroke for diagnosticsMoog Inc..

Inspect monthly for external leakage and loose connections. Replace system filters regularly to maintain ISO 4406 18/15/12 cleanliness. Use genuine MOOG O‑rings if leakage occurs. Do not disassemble internal components; contact MOOG or an authorized service center for repairMoog Inc..

No response may result from missing 24 VDC power, faulty wiring, or absent command signal; check power supply, connections, and signal source. Slow response can be caused by low system pressure, high fluid viscosity, or contaminated fluid; verify pressure settings, use recommended viscosity fluid, and check filtration. Oscillation or instability may come from electrical noise, incorrect controller gain, or poor grounding; improve shielding, adjust loop gains, and verify grounding. External leakage is usually due to worn O‑rings; replace with genuine MOOG sealsMoog Inc..

Model number is D634‑1005. Series is D634 (Direct Drive Servo Valve). Mounting size is ISO 4401 Size 05 (NG10). Integrated electronics are 24 VDC with analog interface. Feedback is LVDT closed‑loop spool position controlMoog Inc..