D634-1001
May 25, 2026

D634-1001

D634‑1001 is a direct‑drive servo valve (DDV) from MOOG D634 series, featuring integrated closed‑loop spool position control, permanent magnet linear force motor, and LVDT feedback. Designed for high‑precision flow control in industrial electro‑hydraulic systems.

Description

1. General Information

1.1 Description

D634‑1001 is a direct‑drive servo valve (DDV) from MOOG D634 series, featuring integrated closed‑loop spool position control, permanent magnet linear force motor, and LVDT feedback. Designed for high‑precision flow control in industrial electro‑hydraulic systems.

1.2 Model Definition

  • D634: Series (ISO 4401 Size 05 / NG10)

  • 1001: Specific configuration (coil, feedback, seals, electronics)

1.3 Key Features

  • No pilot stage: Direct spool drive, high contamination tolerance

  • Pressure‑independent dynamics: Fast, consistent response

  • Integrated 24 VDC PWM electronics: EMC‑compliant

  • Spring‑centered fail‑safe: Spool returns to neutral on power lossMoog Inc.

  • Low hysteresis & high resolution: Precise, repeatable control

1.4 Intended Applications

Injection molding, blow molding, die casting, hydraulic presses, metal forming, fatigue test rigs, and general industrial servo‑hydraulic systems.

2. Technical Specifications

2.1 Hydraulic Data


ParameterValue
Mounting PatternISO 4401 Size 05 (NG10)
Max Operating Pressure (P/A/B)350 bar (5,000 psi)Moog Inc.
Max Pressure (T, without Y)50 bar (725 psi)Moog Inc.
Max Pressure (T, with Y)350 bar (5,000 psi)Moog Inc.
Rated Flow (Δp = 35 bar/land)60–100 L/min (15.9–26.4 gpm)
Maximum Flow~185 L/min (48.8 gpm)Moog Inc.
Internal Leakage0.8 L/min
Fluid TypeMineral oil (ISO 11158)
Viscosity Range5–400 mm²/s (recommended: 15–100 mm²/s)
Fluid Temperature−20 °C to +80 °C
Fluid CleanlinessISO 4406 18/15/12 min (17/14/11 recommended)

2.2 Performance Data

ParameterValue
Step Response (0→100%)20 ms (typical)Moog Inc.
Hysteresis< 0.5% of full scale
Threshold (Resolution)< 0.1% of full scale
Null Shift (ΔT = 55 K)< 2%
Frequency Response (−3 dB)≥ 80 Hz (typical)

2.3 Electrical Data

ParameterValue
Supply Voltage24 VDC (range: 18–32 VDC)Moog Inc.
Current Consumption2.2 A max
External Fuse2.5 A (slow‑blow)
Command Signal (selectable)±10 V, ±10 mA, 4–20 mAMoog Inc.
Input ImpedanceVoltage: >100 kΩ; Current: 50 Ω
Feedback SignalSpool position monitor (standard)
Connector6+PE (M18)Moog Inc.
Protection ClassIP65
Ambient Temperature−20 °C to +60 °C

3. Functional Principle

  1. Command Input: Analog signal (±10 V / ±10 mA / 4–20 mA) is sent to the valve’s integrated electronics.

  2. Force Motor Drive: Electronics drive a permanent magnet linear force motor to move the spool from spring center.

  3. LVDT Feedback: An LVDT measures spool position and feeds it back to the controller.

  4. Closed‑Loop Control: Electronics compare command vs. feedback and adjust motor drive for precise positioning.

  5. Flow Control: Spool displacement regulates flow direction (A→B / B→A) and magnitude to the actuator.


4. Installation & Wiring

4.1 Mechanical Mounting

  • Mount on clean, flat surface per ISO 4401 Size 05.

  • Use supplied O‑rings for port sealing.

  • Torque mounting bolts (M8) to 8–10 Nm.

  • Avoid mechanical stress or misalignment.

4.2 Hydraulic Connections

  • P = Pressure, T = Tank, A/B = Work ports, Y = External drain (optional)Moog Inc..

  • Flush system to achieve ISO 4406 17/14/11 before valve installation.

4.3 Electrical Wiring (6+PE Connector)

PinDescription
1+24 VDC
20 VDC (GND)
3Command Signal (+)
4Command Signal (−)
5Enable (optional)
6Monitor (spool position feedback)
PEProtective Earth
  • Use shielded twisted pair for signals; connect shield to 0 V (power supply side) and connector housing.


5. Commissioning

  1. Pre‑Check: Verify all connections, fluid level, and supply voltage (18–32 VDC)Moog Inc..

  2. Power‑Up: Apply 24 VDC; valve initializes and performs LVDT self‑test.

  3. Signal Selection: Set command signal type (±10 V / ±10 mA / 4–20 mA) via internal jumperMoog Inc..

  4. Null Adjustment: With zero command, adjust null potentiometer for minimum leakage.

  5. Performance Test: Apply step commands (10% / 50% / 100%); confirm smooth response and correct direction.


6. Operation

  • 0 V / 0 mA / 12 mA: Spool centered (no flow)Moog Inc..

  • +10 V / +10 mA / 20 mA: Full flow A→BMoog Inc..

  • −10 V / −10 mA / 4 mA: Full flow B→AMoog Inc..

  • Monitor Pin: Reads spool position feedback (0–10 V proportional to stroke).


7. Maintenance & Troubleshooting

7.1 Maintenance

  • Inspect for external leakage and loose connections monthly.

  • Replace system filters to maintain ISO 4406 18/15/12 cleanliness.

  • Replace O‑rings with genuine MOOG parts if leakage occurs.

7.2 Troubleshooting

SymptomPossible CauseRemedy
No responseNo 24 VDC power / faulty wiringCheck supply and connectionsMoog Inc.

No command signalVerify signal source and wiringMoog Inc.
Slow responseLow system pressureIncrease pressure to rated levelMoog Inc.

High fluid viscosityUse recommended viscosity fluid
OscillationElectrical noiseImprove shielding/grounding

Incorrect loop gainAdjust controller gains
LeakageWorn O‑ringsReplace sealsMoog Inc.

8. Ordering Information

  • Model: D634‑1001

  • Series: D634 (Direct Drive Servo Valve)Moog Inc.

  • Size: ISO 4401 Size 05 (NG10)

  • Electronics: Integrated 24 VDC, analog interfaceMoog Inc.

  • Feedback: LVDT closed‑loop spool position control


© 2026 MOOG Inc. All rights reserved.
Specifications subject to change without notice.


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