I. Basic Information

Series: 631 (两级， mechanical feedback MFB， nozzle baffle pilot)

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 system)

Electrical： Analog current control (±100 mA standard), no built-in amplifier

Installation： ISO 4401-05 (size 05， large installation surface)

Status： In service， main servo valve for heavy industry

II. Core Parameters (Typical Values)

Rated Flow： ≈100 L/min (Δp=35 bar / each side)

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

Frequency Response (-3 dB， 90° phase angle)： ≈65 Hz

Step Response (100%)： ≈22 ms

Hysteresis： ≤3% (mechanical feedback)

Resolution： ≤0.5%

Repeatability： ≤0.5%

Internal Leakage (zero position): <4 L/min (315 bar)

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

Anti-pollution： Medium (pilot small holes， recommended NAS 6–7 level)

Weight： 2.4 kg

III. Model Meaning

D631： 631 Series Two-stage Mechanical Feedback Servo Valve

266： Flow Specification Code (corresponding to 100 L/min @35 bar)

C： Electrical / Sealing / Material Configuration (standard type， FKM Sealing)

IV. Key Features

Two-stage Mechanical Feedback (MFB)： Robust structure， long lifespan， good heavy-load stability

Large Flow Design： 100 L/min， suitable for heavy hydraulic systems

Dry Torque Motor： Good insulation， resistant to oil interference， high reliability

Exterior Amplifier Drive： Standard ±100 mA， compatible with MOOG 100 points or third-party amplifiers

V. Typical Applications

Heavy-duty material testing machines， large fatigue test benches

Metallurgy： Large rolling mills， roll gap control， tension control

Injection / Blow molding： Large machine wall thickness， mold clamping force control

Construction Machinery： Large servo actuators， synchronous lifting

Aerospace / Ground： Large structural testing， loading system