Model Definition

D661 = Series (integrated electronics, 24 VDC, NG10)

4821 = Spool/sleeve assembly; rated flow 120 L/min @ ΔP=35 bar

Typical full config example: P120HDAM6NSF2‑A

P120 = Medium flow & high frequency response version

HDAM = Standard hydraulic layout, 24 VDC, ±10 V/±10 mA command, centered null

6 = 6+PE connector, IP65

NSF2 = NBR seals, wide temperature range, LVDT feedback 4–20 mA

A = Standard ServoJet® pilot stage

Technical Specifications

Hydraulic Parameters

Rated flow: 120 L/min (ΔP=35 bar)

Max working pressure: 350 bar (P/A/B); 210 bar (internal drain T) / 350 bar (external drain T)Moog Inc.

Step response: 6.5–10 ms (0→100%, 210 bar)Moog Inc.

Hysteresis: <0.2%

Resolution: <0.1%

Null drift: <1.2% (ΔT=55 K)

Null leakage: <18 mL/min

Fluid cleanliness: NAS 1638 Class 6 / ISO 4406 18/15

Electrical Parameters

Power supply: 24 VDC (18–32 VDC)Moog Inc.

Control signal: ±10 V (differential) or ±10 mAMoog Inc.

Feedback signal: 4–20 mA (LVDT spool position)Moog Inc.

Connector: 6+PE, IP65Moog Inc.

Current draw: ≤680 mA

Physical & Environmental

Operating temperature: −40 ℃ to +85 ℃

Weight: approx. 9.2 kg

Interface & Communication Configuration

Hydraulic interface: P/A/B/T, ISO 4401‑05 (NG10)

Electrical interface:

Power: 24 VDC, GND, PE

Command: ±10 V / ±10 mAMoog Inc.

Feedback: 4–20 mA (spool position)Moog Inc.

Status: Fault alarm output

Core Functions

ServoJet® pilot stage: Superior contamination resistance, low null drift, extended service lifeMoog Inc.

Integrated high‑response amplifier: Built‑in PID, dead‑zone compensation, overload protection

LVDT closed‑loop feedback: High linearity and precision across full strokeMoog Inc.

Fail‑Safe centering: Spool returns to neutral on power lossMoog Inc.

Medium‑flow dynamics: Optimized for 120 L/min with fast response for precision applications

Application Scenarios

Metallurgy: Medium‑flow AGC roll gap control, tension control for light‑medium plate mills

Test equipment: High‑precision dynamic material testers, medium‑scale vibration tables

Industrial automation: Medium‑sized CNC machine tools, hydraulic presses, standard injection molding machines

Energy & heavy industry: Wind turbine pitch control, small shield machine main control, marine auxiliary hydraulic systems

Usage & Maintenance

Installation: Horizontal/vertical mounting; avoid severe vibration

Fluid: ISO VG46 mineral oil; maintain cleanliness per NAS 1638 Class 6

Commissioning: Apply 24 VDC power; connect ±10 V/±10 mA command; calibrate zero and gain via 4–20 mA feedbackMoog Inc.

Maintenance: Inspect fluid contamination regularly; calibrate zero/gain every 6 months; avoid long idle periods at high pressure