Basic Information

• Brand: MOOG

• Model: D634‑559

• Series: D634 (Direct Drive Valve, DDV)

• Type: Single‑stage, pilotless, direct‑operated servo valve

• Mounting: ISO 4401‑05 (NG10)

• Drive: High‑thrust permanent magnet linear force motor (higher than 558)

• Feedback: Built‑in LVDT spool position closed loop

• Electronics: Integrated 24 VDC PWM drive

• Protection: IP65

• Weight: Approx. 6.3 kg (13.9 lb)

Hydraulic Specifications

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

• Max T‑port pressure (no Y port): ≤50 bar (725 psi)Moog Inc.

• Max T‑port pressure (with Y port): 350 bar (5,000 psi)Moog Inc.

• Rated flow (Δp = 35 bar): 210 L/min (55.5 gpm)

• Peak flow: ≈280 L/min (74.0 gpm)

• Null leakage: 5–12 L/min

• Fluid: ISO 11158 mineral hydraulic oil

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

• Fluid temperature: −20 °C to +80 °C

Electrical Specifications

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

• Max current: 3.5 A (higher than 558)

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

• Connector: 6‑core + PE, IP65Moog Inc.

• Electronics: SMD technology, PWM current output, EMC certified

Dynamic Performance (Typical)

• Full‑stroke step response: ≤40 ms

• −3 dB bandwidth: 6–12 Hz

• Hysteresis: <0.40% of full scale

• Resolution: <0.25% of full scale

• Temperature drift (ΔT = 55 K): <2.2% of full scale

Key Features

• Pilotless direct drive: No pilot oil required; simpler installation, lower leakage。

• Ultra‑high‑flow design: Highest flow in D634‑55x series; optimized for large‑scale hydraulic systems。

• High‑thrust motor: Delivers higher force than 558; suitable for high‑load, high‑flow applications。

• LVDT closed‑loop feedback: Ensures accurate and repeatable spool positioningMoog Inc.。

• Spring centering: Fail‑safe return to neutral on power loss。

• Pressure‑independent dynamics: Stable performance under varying loads。

Applications

• Ultra‑large hydraulic presses and heavy forging equipment

• High‑tonnage injection molding and die‑casting machines

• High‑force & ultra‑high‑flow vibration test benches

• Heavy‑duty industrial hydraulic systems requiring maximum flow

• Precision position, force & speed closed‑loop control

D634‑55x Series Flow Ranking (L/min @ Δp=35 bar)

• 551: 60

• 552: 80

• 553A: 100

• 554A: 120

• 555: 135

• 557: 150

• 558: 180

• 559: 210 ← Current model

• 560: 240