1. Model Code Breakdown

• D634: Series, direct‑drive servo valve (DDV), ISO 4401‑05 (NG10) mountingMoog Inc.

• K: Explosion‑proof version (Ex de IIB+H2 T4/T3), Zone 1/2 hazardous areas

• 2005: Flow rating & revision (2000 series, 5th ultra‑high‑precision revision)

• C: Design revision level

2. Basic Data

• Brand: MOOG

• Type: Single‑stage, pilotless direct‑drive servo valve (DDV)Moog Inc.

• Mounting: ISO 4401‑05 (NG10)Moog Inc.

• Drive: Permanent magnet linear force motor (bidirectional direct drive)Moog Inc.

• Feedback: Integrated LVDT spool position closed‑loop

• Electronics: Integrated 24 VDC PWM drive, “de” explosion‑proof

• Protection: IP65

• Weight: ~6.3 kg

• Certifications: ATEX II 2G Ex de IIB+H2 T4/T3; IECEx BVS 13.0126X

3. Hydraulic Specifications

• Max working pressure (P/A/B): 350 bar (5,000 psi)

• Max T‑port pressure: ≤50 bar (standard); 350 bar optional (with Y‑port)Moog Inc.

• Rated flow (Δp = 35 bar): 100 L/min (26.4 gpm)

• Peak flow: 180 L/min

• Null leakage: 2.5–7 L/min

• Fluid: ISO 11158 mineral hydraulic oil

• Fluid temp: −20 °C to +80 °C (−4 °F to +176 °F)

• Viscosity: 15–100 mm²/s (recommended); 5–400 mm²/s (allowed)

4. Electrical Specifications

• Supply voltage: 24 VDC (operating range 18–32 VDC)Moog Inc.

• Max operating current: 2.5 A

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

• Connector: 6‑core + PE groundMoog Inc.

• EMC: Compliant with EC directives (EN 55011 Class B, EN 50082‑2)

5. Dynamic Performance (2005C Upgraded)

• Full‑stroke step response: ≤18 ms (faster than 2004C)

• −3 dB bandwidth: 22–35 Hz (widest in 2000 sub‑series)

• Hysteresis: <0.15% full scale (lowest in 2000 sub‑series)

• Resolution: <0.05% full scale (ultra‑high precision)

• Temperature drift: <1.0% full scale (best thermal stability)

6. Key Features

• ✅ Pilotless design: No pilot oil; simpler piping, lower internal leakageMoog Inc.

• ✅ Pressure‑independent dynamics: Stable regardless of system pressure swingsMoog Inc.

• ✅ LVDT closed‑loop: Real‑time spool feedback for unmatched positioning accuracy

• ✅ Spring centering: Fail‑safe (spool returns to neutral on power loss)Moog Inc.

• ✅ 2005C Ultra‑precision: Optimized spool geometry; best‑in‑class flow linearity and repeatability

• ✅ Explosion‑proof: ATEX/IECEx certified for flammable/hazardous environments

• ✅ Standard mounting: NG10 (ISO 4401‑05) drop‑in replacementMoog Inc.

7. Typical Applications

• Offshore oil & gas, chemical, petrochemical hydraulic systems

• Mining machinery and hazardous‑area electro‑hydraulic controls

• High‑precision closed‑loop control (position/velocity/pressure/force) in explosive zones

• Combustible media processing equipment

• Critical energy & process industries requiring ATEX/IECEx compliance

8. Revision Comparison (2001C → 2005C)

• 2001C: Base version, standard linearity

• 2002C: Enhanced low‑frequency stability

• 2003C: High precision, better linearity, lower hysteresis

• 2004C: Top‑tier performance, wider bandwidth

• 2005C: Ultimate performance; highest linearity, lowest hysteresis/drift, fastest response for critical applications