I. Model Meaning (Detailed Analysis by Each Digit)

D631: 631 Series Two-stage Mechanical Feedback Servo Valve

K: Ex ia IIC T4/T6 Explosion-proof (Zone 0/1/2 Available)

780: Flow Code → 40 L/min @ Δp=35 bar (Greater than 771's 25 L/min)

C: Built-in Pilot Supply Oil, NBR Seal, Standard Zero Position

In one sentence: K780C = Explosion-proof + 40 L/min High Flow + Built-in Pilot + Standard Performance

II. Core Parameters (Δp=35 bar / Each Side)

Rated Flow: 40 L/min

Maximum Working Pressure: 315 bar

Frequency Response (−3 dB, 90°): ≈ 55–65 Hz (Higher flow, slightly lower than 771)

Step Response (100%): ≈ 22–28 ms

Hysteresis: ≤ 0.3%

Resolution: ≤ 0.1%

Zero Position Leakage: ≈ 0.7–0.8 L/min (Higher flow, slightly higher leakage)

Pilot Supply Oil: Built-in (Oil is taken from Port P)

Explosion-proof Grade: Ex ia IIC T4/T6 (Explosion-proof) Moog Inc.

Temperature Range: −20 ℃ ~ +80 ℃

Filter Requirements: NAS 6–7 / ISO 4406 <14/11

III. Comparison of D631K780C and K771C (Most Common Reference) Table

Project D631K780C D631K771C Effect

Rated Flow Rate 40 L/min 25 L/min 780C is suitable for larger actuators / faster speed

Frequency Response 55–65 Hz 60–70 Hz 780C has slightly slower dynamics, trade-off for high flow rate

Zero Position Leakage 0.7–0.8 L/min 0.6 L/min 780C has slightly higher leakage

Hysteresis / Resolution 0.3% / 0.1% 0.3% / 0.1% Accuracy is comparable

Explosion-proof / Pilot Explosion-proof + Built-in Explosion-proof + Built-in Same

Typical Applications High-flow closed-loop in explosion-proof areas High-flow precise closed-loop in explosion-proof areas 780C is more "for high flow and general dynamics" Characteristics

✅ 40 L/min explosion-proof high-flow rate: The flow rate in the explosion-proof area is 60% higher than that of 771

✅ Built-in pilot: No need to connect the X port externally. The system is simple and easy to install

✅ Standard dynamic + standard leakage: Cost-effective, reliable and durable

✅ Explosion-proof K: Directly meets Ex ia IIC T4/T6, suitable for Zone 0/1/2 Moog Inc.

Typical applications

Chemical explosion-proof hydraulic station: Medium-large flow actuators, closed-loop control in explosion-proof area

Oil and gas platform / wellhead control: Explosion-proof circuit, large-flow hydraulic actuator

Dust explosion-proof environment: Aluminum powder / flour / feed equipment, 40 L/min precision control

Metallurgical explosion-proof conditions: Roll gap / tension control, explosion-proof hydraulic system requiring larger flow rate