D634-331C
May 25, 2026

D634-331C

D634-331C is a single-stage pilotless direct drive servo valve of MOOG D634 series complying with ISO 4401 Size 05 mounting standard. Permanent magnet linear force motor directly drives the spool without pilot oil supply. Built-in LVDT achieves closed-loop position control with excellent linearity and repeatability. Dynamic characteristics remain stable regardless of load pressure change. Spring centering structure realizes fail-safe neutral reset when power fails. This model features 60 L/min rated flow and improved dynamic response.

Description

1. General Description

D634-331C is a single-stage pilotless direct drive servo valve of MOOG D634 series complying with ISO 4401 Size 05 mounting standard. Permanent magnet linear force motor directly drives the spool without pilot oil supply. Built-in LVDT achieves closed-loop position control with excellent linearity and repeatability. Dynamic characteristics remain stable regardless of load pressure change. Spring centering structure realizes fail-safe neutral reset when power fails. This model features 60 L/min rated flow and improved dynamic response.

2. Model Definition

D634: Direct drive servo valve series
331: High response configuration with 60 L/min flow rating
C: Revision version C

3. Hydraulic Specifications

Mounting standard: ISO 4401 Size 05 (NG10)
Max working pressure(P,A,B): 350 bar
T port maximum pressure: 50 bar
Rated flow at 35 bar pressure drop: 60 L/min
Maximum flow rate: approx 110 L/min
Internal leakage: ≤1.0 L/min
Applicable fluid: ISO 11158 mineral oil
Fluid temperature range: -20 °C ~ +80 °C
Required fluid cleanliness: ISO 4406 17/14/11
Total weight: approx 6.3 kg

4. Dynamic Performance

Full stroke step response: ≤15 ms
-3dB frequency bandwidth: 60~70 Hz
Hysteresis: less than 0.2% full scale
Resolution: less than 0.1% full scale
Null drift under 55K temperature change: less than 1.5% full scale

5. Electrical Specifications

Supply voltage: 24 VDC, working range 18~32 VDC
Maximum operating current: 3.5 A
Standard control signal: ±10 V
Optional signal: ±10 mA, 4-20 mA
Spool position feedback output: 0-10 VDC
Connector type: M18, 6 pins with PE terminal, IP65 protection grade
Ambient working temperature: -20 °C ~ +60 °C
EMC certification: CE compliant

6. Key Features

Pilot oil free design for easy installation and maintenance
Fast response and high positioning precision
Pressure independent dynamic performance
Fail-safe protection by spring centering mechanism
Integrated compact electronic drive unit

7. Application Scope

High precision hydraulic press equipment
Dynamic fatigue testing machines
High speed industrial automatic control system
Closed-loop position, velocity and pressure control system

8. Pin Assignment

Pin 1: +24 VDC
Pin 2: Power ground
Pin 3: Command signal positive
Pin 4: Command signal negative
Pin 5: Position feedback output
Pin 6: Feedback ground
PE: Protective earth
Use shielded twisted pair cable for signal connection


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