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, classic general-purpose industrial servo valve

II. Core Parameters (Typical Values)

Rated flow： ≈75 L/min (Δp=35 bar / each side)

Maximum working pressure： 315 bar (4，500 psi)

Frequency response (-3 dB， 90° phase angle)： ≈75 Hz

Step response (100%)： ≈18 ms

Hysteresis： ≤3% (mechanical feedback)

Resolution： ≤0.5%

Repeatability： ≤0.5%

Internal leakage (zero position)： <3 L/min (315 bar)

Temperature range： ambient -20 ℃ ~ +60 ℃； oil -20 ℃ ~ +80 ℃

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

Weight： 2.2 kg

III. Model Meaning

D631： 631 series two-stage mechanical feedback servo valve

195： Flow specification code (corresponding to 75 L/min @35 bar)

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

IV. Key Features

Classic two-stage mechanical feedback (MFB)： Simple structure， reliable， long lifespan， low cost， industrial general-purpose main product

Double nozzle baffle pilot： High resolution， low hysteresis， dynamic stability

Dry torque motor： Not affected by oil contamination， good insulation， high reliability

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

V. Typical Applications

General industrial hydraulics： Position / speed / force control system

Material testing machines， fatigue test benches (medium load)

Injection molding machines， blow molding machine wall thickness control

Metallurgy： Small and medium-sized rolling mills， tension control

Machine tools： Hydraulic profiling， precision feed

Aerospace / ground testing equipment