1. Basic Identification

• Model: D633-631

• Brand: MOOG (USA)

• Category: Direct‑Drive Electro‑Hydraulic Servo Valve (DDV)

• Alias: Direct‑Operated Servo Valve, Integrated Electronic Servo Proportional Valve, D633 Series High‑Pressure Servo Valve

• Model Code Definition:

  • D633: Series (ISO 4401 Size 03/NG6, direct drive)

  • 631: Flow/pressure/configuration code (nominal flow ≈ 30 L/min)

  • (No suffix): Standard seal (NBR), M12 connector

2. Basic Information

• Structure: Permanent magnet linear force motor directly drives the spool, no pilot oil, integrated electronic closed‑loop controlMoog Inc.

• Mounting Standard: ISO 4401‑03‑03‑0‑94 (NG6)Moog Inc.

• Weight: Approx. 2.5 kg

• Protection Class: IP67 (connector), IP65 (valve body)

• Temperature Range: Ambient −20 ℃～+60 ℃; Fluid −20 ℃～+70 ℃

• Fluid Compatibility: Mineral hydraulic oil (ISO 4406 18/15/12)

3. Function & Positioning

• Core Function: 4/3‑way direction, speed, pressure, force closed‑loop control; throttling flow control

• Positioning: High‑dynamic, mid‑flow, high‑precision core control component for industrial electro‑hydraulic systems; suitable for high‑response, medium‑force applications

• Key Features:

  • Pressure‑independent dynamic performance, fast responseMoog Inc.

  • Spring‑centered on power failure, high safety redundancyMoog Inc.

  • Low null current, low hysteresis (≤0.2%)

  • Excellent contamination resistance (no pilot stage)

4. Core Performance Parameters

Hydraulic Parameters

• Rated Flow: 30 L/min (at Δp = 35 bar per edge)

• Max Working Pressure: 350 bar (P/A/B ports); 50 bar (T port)Moog Inc.

• Fluid Viscosity: 15–100 mm²/s (operational); 5–400 mm²/s (allowable)

Electrical Parameters

• Power Supply: 24 VDC (18–32 VDC)Moog Inc.

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

• Feedback Signal: 4–20 mA

• Max Current Consumption: ≤1.2 A

• Electrical Connector: M12 (6+PE pins)Moog Inc.

Performance

• Step Response (0–100%): ≤12 msMoog Inc.

• Hysteresis: ≤0.2%

• Linearity: ≤0.1%

• Resolution: ≤0.05%

5. General Matching Accessories

• M5 Grade 10.9 mounting bolts

• OEM NBR/FPM sealing kits

• 5‑core shielded cable (M12 compatible)

• 10 μm high‑pressure hydraulic filter

• M12 waterproof connector (male/female)

6. Applicable Industries & Equipment

• Precision metal forming (medium presses, stamping lines)

• High‑precision injection molding & die‑casting machines

• Metallurgical rolling & continuous casting equipment

• Aerospace test benches & simulators

• Industrial robot hydraulic units

• Vibration & fatigue testing systems (medium‑high force)

• Heavy‑duty automation hydraulic control systems (mid‑flow, high‑accuracy)