Model Code Explanation (D661-4187)

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

4: High‑flow platform

18: 180 L/min nominal flow rating

7: Ultra‑high‑dynamic, single‑feedback, maximum‑response base (faster than 4186)

(No suffix): Standard electronics, premium null stability

Technical Specifications

Part Number: D661-4187

Mounting: ISO 4401‑05 (NG10), 4‑hole, M5 screws (torque 8 Nm)Moog Inc.

Control Function: 4‑way/3‑position, spring‑centered, zero‑lap, closed‑loop controlMoog Inc.

Hydraulic

Nominal Flow (Δp = 35 bar): 180 L/min (±8%)Moog Inc.

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. 5.8–6.0 kg

Electrical

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

Command Signal: ±10 V differential (10 kΩ impedance); optional ±10 mAMoog Inc.

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

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

Step Response (0→100%): ≤7 ms @ 210 bar (faster than 4186/4178)

Hysteresis: <0.18% (closed‑loop)

Linearity: <±0.20%

Resolution: <0.07%

Interface & Communication

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

Feedback: Single integrated LVDT (full‑stroke closed‑loop, high‑accuracy for 180 L/min flow)Moog Inc.

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

Key Features

180 L/min Nominal Flow: Matches 4186; higher than 4157B/4158B/4168; lower than 4178

Maximum‑Dynamic Response: 7 ms step response (fastest in 41xx high‑flow group)

High‑Pressure Rated: 350 bar max working pressure for severe‑duty applicationsMoog Inc.

Premium Null Stability: Superior null shift performance for long‑term precision

Single‑LVDT Precision: Reliable closed‑loop feedback for consistent accuracy at high flow

Applications

Ultra‑high‑dynamic test benches (aerospace/defense, high‑frequency fatigue)

Heavy‑duty industrial automation (high‑speed forging presses, steel rolling mills)

Metallurgy (high‑precision roll gap control, high‑tension systems)

Heavy machinery (mining excavators, high‑tonnage die‑casting)

Energy (high‑flow hydraulic control, turbine governing systems)

Compatibility

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

Drop‑in upgrade for D661‑4186 (faster response) and 4178/4168/4158B/4157BMoog Inc.

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