Model Code Explanation (D661-4551)

• D661: Series (ISO 4401‑05 mounting, integrated 24 VDC electronics)

• 4: 4‑way, zero‑lap, linear flow characteristic

• 55: Rated flow ≈ 250 L/min (Δp = 35 bar per land, max standard flow in D661 series)

• 1: Standard‑dynamic response, single LVDT feedback, basic null stability

• (no letter): Standard performance, non‑explosion‑proof (equivalent to “C” in earlier models)

Technical Specifications

Part Number: D661-4551

Mounting

Control Function

Hydraulic Parameters

• Rated Flow (Δp = 35 bar): 250 L/min (±8%, max for ISO 4401‑05)

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

• Pilot Pressure (X): 21–280 bar (internal P or external X)Moog Inc.

• T Port Pressure (Y internal): 210 bar; (Y external): 350 barMoog Inc.

• Fluid: Mineral oil (DIN 51524), viscosity 15–45 mm²/sMoog Inc.

• Temperature: Ambient −20°C to +60°C; Fluid −20°C to +80°CMoog Inc.

• Weight: Approx. 6.2–6.4 kg

Electrical Parameters

• Supply: 24 VDC (18–32 VDC), quiescent 230 mA, dynamic ~500 mAMoog Inc.

• Command Signal: ±10 VDC (differential, 10 kΩ impedance) or 4–20 mAMoog Inc.

• Feedback Signal: 4–20 mA (single LVDT spool position, ±0.02% FS accuracy)Moog Inc.

• Connector: 6+PE (EN 175201‑804, IP65)Moog Inc.

• Step Response (0→100%): 10–14 ms @ 210 bar (standard dynamics for 250 L/min)

• Hysteresis: <0.30% (closed‑loop)Moog Inc.

• Linearity: <±0.35%

• Resolution: <0.10%Moog Inc.

Interface & Communication Configuration

• Electrical: 6+PE connector; ±10 V command, 24 VDC power, 4–20 mA LVDT feedbackMoog Inc.

• Feedback: Single integrated LVDT (full‑stroke closed‑loop, high accuracy)Moog Inc.

• Ports: P, A, B, T; optional external X (pilot) and Y (return)Moog Inc.

• Seal Material: NBR (standard) or FKM (optional, high‑temperature)Moog Inc.

Core Functions

1. 250 L/min Max Flow: Highest standard flow in D661 series, for large‑capacity hydraulic systems

2. Standard‑Dynamic Response: 10–14 ms step response, optimized for high flow + cost efficiency

3. Closed‑Loop Spool Control: Integrated LVDT ensures real‑time position feedback and consistent precisionMoog Inc.

4. ServoJet® Pilot: Jet‑pipe design reduces energy use, improves contamination resistance, and lowers hysteresisMoog Inc.

5. Integrated Digital Amplifier: On‑board PID, ramp generator, fault diagnostics, and EMC protection

Applicable Scenarios

• Ultra‑Large Metal Forming: Extra‑large injection molding, heavy die‑casting, massive stamping presses (max flow priority)

• Heavy‑Duty Industrial Presses: Steel mill rolling mills, large hydraulic forging presses, high‑flow material handlingMoog Inc.

• High‑Flow Test Systems: Industrial component testing, large‑scale vibration simulation, fatigue test rigs (max flow capacity)Moog Inc.

• Hydraulic Power Units (HPUs): High‑flow closed‑loop control systems requiring stability at maximum flow rates

Compatibility & Installation Notes

• Mechanical: Interchangeable with D661 (G/C/A), D662/D663 (ISO 4401‑05)Moog Inc.

• Upgrade: Drop‑in replacement for lower‑flow D661‑4536C/4538C/4539C/4546C when max flow is needed

• System Requirements: 24 VDC supply, analog controller (±10 V in / 4–20 mA out), ISO 4401‑05 manifoldMoog Inc.

Usage & Maintenance Instructions

1. Installation: Mount on flat surface (flatness ≤0.02 mm/100 mm; Ra <1 μm) with M6×55/60 bolts (13 Nm, diagonal)Moog Inc.

2. Fluid: ISO VG 32–46, NAS 1638 cleanliness class ≤8Moog Inc.

3. Maintenance: Replace internal filter every 5,000 hours; inspect leaks/connectors periodicallyMoog Inc.

4. Precautions: Avoid voltage spikes/reverse polarity; do not open standard models in field