1. Product Overview

2. Basic Information

• Brand: MOOG

• Model: D634-521

• Type: Pilotless electro‑hydraulic direct‑drive servo valve

• Mounting: ISO 4401‑05 (NG10)

• Drive: Permanent magnet linear force motor (no pilot oil)

• Power Supply: 24 VDC (18–32 VDC), max 2.2 AMoog Inc.

• Feedback: Integrated LVDT spool position closed‑loop

• Reset: Spring‑centered; fail‑safe neutral on power lossMoog Inc.

• Protection: IP65

• Weight: ~6.3 kg

• Connector: M18 6‑pin + PEMoog Inc.

3. Function & Positioning

• Function: Precise flow/direction control via analog signals; closed‑loop control of position/velocity/pressure/force with low hysteresis, high repeatability, pressure‑stable response.

• Positioning: Medium‑flow model in D634 series, for medium‑to‑heavy duty, high‑dynamic industrial hydraulics.

4. Core Performance Parameters

Hydraulic Parameters

• Max working pressure (P/A/B): 350 barMoog Inc.

• Max T‑port pressure: ≤50 bar (no Y‑port); ≤350 bar (with Y‑port)Moog Inc.

• Rated flow (Δp=35 bar): 60 L/min

• Peak flow: ~110 L/min

• Null leakage: 0.25–1.8 L/min

• Fluid: ISO 11158 mineral oil

• Fluid temp: –20 °C to 80 °C

• Cleanliness: ISO 4406 17/14/11

Dynamic Parameters

• Full‑stroke step response: ≤16 msMoog Inc.

• –3 dB bandwidth: 60–80 Hz

• Hysteresis: <0.15% full scaleMoog Inc.

• Resolution: <0.06% full scale

• Temp drift: <1.0% full scale

Electrical Parameters

• Standard control signal: ±10 VDCMoog Inc.

• Optional signals: ±10 mA, 4–20 mAMoog Inc.

• Spool feedback: 0–10 VDC

• Ambient temp: –20 °C to 60 °C

• Certification: CE compliant

5. Matching Accessories

• Shielded twisted cable, M18 waterproof connector

• ISO 4401‑05 standard manifold

• High‑precision hydraulic filter

• 24 VDC low‑ripple power supply

• Servo controller, displacement/pressure sensors

6. Application Fields

• Medium‑tonnage hydraulic presses & forging machines

• Injection molding & die‑casting equipment

• Vibration test benches & material fatigue testing

• General industrial high‑response hydraulic systems

• Automation machinery requiring accurate flow control