• D633: Series, ISO 4401 Size 03 / NG6 direct‑drive servo valve (DDV)

• R: 2×2‑way (4/2) configuration

• 16: Rated flow 16 L/min (Δp=35 bar per edge)

• K: Max working pressure 350 bar

• O: Standard spool/bushing

• 1: Linear force motor size

• M: Failsafe (spring centering on power‑off)

• O: No Y‑port

• V: Seal material FPM (fluoro rubber)

• S: Electrical connector M12

• S2: Signal/feedback (4–20 mA command + 4–20 mA position feedback)

Basic Identification

• Model: D633‑R16KO1MOVSS2

• Brand: MOOG

• Type: Single‑stage, pilotless direct‑drive electro‑hydraulic servo valve (DDV)

• Mounting: ISO 4401‑03‑03‑0‑94 (NG6)

• Weight: ≈2.5 kg

• Protection: Connector IP67, body IP65

Hydraulic Specifications

• Rated Flow: 16 L/min (Δp=35 bar/edge)

• Max Flow: ≈75 L/min

• Max Working Pressure: P/A/B 350 bar; T (no Y) 50 barMoog Inc.

• Null Leakage: ≤0.5 L/min (typical)

• Fluid: Mineral hydraulic oil, ISO 4406 18/15/12; viscosity 15–100 mm²/s

• Fluid Temp: −20 °C to +80 °C

Mechanical & Environmental

• Configuration: 4/2‑way, permanent magnet linear force motor, integrated closed‑loop electronics

• Ambient Temp: −20 °C to +60 °C

Electrical Specifications

• Supply: 24 VDC (18–32 VDC)Moog Inc.

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

• Position Feedback: 4–20 mAMoog Inc.

• Max Current: ≤1.2 A

• Connector: M12 (6+PE)

Performance

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

• Hysteresis: ≤0.2%

• Linearity: ≤0.1%

• Resolution: ≤0.05%

• Features: Pressure‑independent dynamics, spring centering on power‑off, high contamination resistance

Applications

• High‑flow precision control, 2‑axis synchronisation

• Material testing, fatigue rigs

• High‑precision positioning, hydraulic robots

• Injection moulding, die‑casting closed‑loop control