I. Basic Information

Structure: Dry torque motor + double nozzle baffle pilot + four-way main valve core + mechanical feedback rod

Function: 4-way, zero opening, flow control (position / force / pressure closed loop)

Electrical Interface: MS3106 aviation plug, single coil ±100 mA

Weight: Approximately 2.4 kg

Material: Aluminum alloy valve body, corrosion-resistant alloy valve core

II. Core Parameters (Δp = 35 bar / each side)

Rated Flow: 120 L/min (maximum flow specification in 631 series)

Maximum Working Pressure: 315 bar (4,500 psi)

Frequency Response (−3 dB, 90° phase angle): ≈ 60 Hz

Step Response (100%): ≈ 25 ms

Hysteresis: ≤ 3% (mechanical feedback)

Resolution: ≤ 0.5%

Internal Leakage (zero position): < 4.2 L/min @ 315 bar

Temperature Range: Ambient -20 ℃ ~ +60 ℃; Oil -20 ℃ ~ +80 ℃

Filter Requirements: NAS 6–7 grade (pilot small hole, moderate anti-pollution)

III. Model Meaning D631-333C

D631: 631 Series Two-stage Mechanical Feedback Servo Valve

333: Flow Code → 120 L/min @ 35 bar (maximum for this series)

C: Standard configuration, FKM seal, industrial / power generation general use

Four. Key Features

Super large flow (120 L/min): The 631 series has the largest flow capacity, covering heavy-duty / ultra-large power hydraulic systems

Heavy-duty mechanical feedback (MFB): Robust structure, 24-hour continuous operation, long lifespan, good stability under heavy load

High-pressure tolerance (315 bar): Commonly used in metallurgy, power generation, and heavy-load testing machines

Dry torque motor: Good insulation, resistant to oil interference, high reliability

External amplifier drive: Standard ±100 mA, compatible with MOOG 100 points or third-party amplifiers

Five. Typical Applications

Power generation / turbine: DEH electro-hydraulic control, main steam valve / regulating valve (large flow demand)

Metallurgy: Large rolling mills, thick plate rolling mills, roll gap / tension control (large flow + high pressure)

Heavy-load material testing machine: Fatigue tests for 200–500 ton levels, structural loading

Large injection molding / blow molding: Super large machine lock-in force, wall thickness control

Construction machinery: Large servo actuators, synchronous lifting, hydraulic lifting system