1. General Description

2. Model Code

• D634: Series, ISO 4401‑05 (NG10)

• 531: High‑flow rating; standard analog (±10 V / ±10 mA / 4–20 mA)Moog Inc.

3. Mechanical & Electrical Data

• Brand: MOOG

• Model: D634‑531

• Type: Electro‑hydraulic direct‑drive servo valve (DDV)

• Mounting: ISO 4401‑05 (NG10)

• Actuation: 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

• Centering: Spring‑centered; fail‑safe neutral on power loss

• Protection Class: IP65

• Weight: ≈ 6.8 kg

• Connector: M18 6‑pin + PEMoog Inc.

4. Hydraulic Specifications

• Max Working Pressure (P, A, B): 350 bar (5,000 psi)

• Max T‑Port Pressure (internal drain): ≤ 50 bar; Y‑port option up to 350 barMoog Inc.

• Rated Flow (Δp = 35 bar per land): 100 L/min (26.4 gpm)

• Peak Flow: ≈ 180 L/min (47.5 gpm)

• Null Leakage: 0.7–4.0 L/min

• Fluid: ISO 11158 mineral oil

• Fluid Temperature: –20 °C to +80 °C

• Fluid Cleanliness: ISO 4406 17/14/11

5. Dynamic Performance

• Full‑Stroke Step Response: ≤ 20 ms (typical)Moog Inc.

• –3 dB Frequency Bandwidth: 40–60 Hz

• Hysteresis: ＜0.25% full scale

• Resolution: ＜0.10% full scale

• Temperature Drift: ＜1.5% full scale

6. Electrical Interface

• Standard Control Signal: ±10 VDCMoog Inc.

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

• Spool Feedback Signal: 0–10 VDC

• Ambient Temperature: –20 °C to +60 °C

• Certification: CE compliant

7. Key Features

• Pilotless design enhances reliability and eliminates pilot oil supply needs

• LVDT closed‑loop feedback ensures high precision and repeatability

• Pressure‑independent dynamics maintain consistent performance under varying loads

• Low power consumption with 24 VDC PWM drive

• Spring fail‑safe centering protects machinery on power loss

8. Applications

• Heavy‑duty hydraulic presses & forging equipment

• Large injection molding & die‑casting machines

• High‑displacement vibration test benches

• Industrial hydraulic systems requiring high flow & high response

• Precision closed‑loop control of position, speed, pressure