I. Model Meaning (Detailed Analysis by Each Digit)

D631: 631 Series Two-Level Mechanical Feedback Servo Valve

K: Ex ia Explosion-proof (IIC T4/T6), Zone 0/1/2 Available from Moog Inc.

771: Flow Code → 25 L/min @ Δp=35 bar

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

K (Suffix): Key Customization = Explosion-proof Coil + Low Power Consumption Design + Reverse Polarity Protection + Explosion-proof Special Connector from Moog Inc.

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

Rated Flow: 25 L/min

Maximum Working Pressure: 315 bar

Frequency Response (−3 dB, 90°): 60–70 Hz

Step Response (100%): 20–25 ms

Hysteresis / Resolution: ≤ 0.3% / ≤ 0.1%

Zero Position Leakage: ≈ 0.6 L/min

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

Explosion-proof Rating: Ex ia IIC T4/T6 (Explosion-proof, Oil/Gas / Dust Explosion-proof Area) from Moog Inc.

Coil Characteristics (K Suffix):

Rated Current: ±40 mA (Explosion-proof Low Power Consumption)

Coil Resistance: High Resistance Type (Explosion-proof Energy Limitation)

Insulation Class: H Class (High Temperature Explosion-proof Safety)

Protection: Reverse Polarity, Surge Suppression, Explosion-proof Sealing Connector from Moog Inc.

Temperature Range: −20 ℃ ~ +80 ℃

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

III. Comparison of D631K771CK with K771C / K771CA Table

Model Explosion-proof Coil/Electrical Leakage Frequency Response Applicable Scenarios

D631K771CK Ex ia Intrinsically Safe Explosion-proof coil + reverse polarity protection + low power consumption 0.6 L/min 60–70 Hz Explosion-proof area + standard electrical + safety certification

D631K771C Ex ia Intrinsically Safe Standard coil 0.6 L/min 60–70 Hz General for explosion-proof area

D631K771CA Ex ia Intrinsically Safe Standard coil 0.45 L/min 65–75 Hz Explosion-proof area + low leakage + high dynamics

The difference in one sentence:

K771CK = K771C + Intrinsically Safe explosion-proof coil + reverse polarity protection + explosion-proof connector

It is not a performance upgrade (leakage/frequency response remain unchanged), but an enhancement of explosion-proof electrical safety, directly meeting the requirements for explosion-proof area intrinsically safe circuit certification.

Four. Features and Applications Characteristics

✅ Dual explosion-proof protection: Valve body K is intrinsically safe + Coil K is explosion-proof certified, in accordance with Ex ia IIC T4/T6 Moog Inc.

✅ Low-power explosion-proof coil: Compatible with intrinsically safe safety barriers, no need for additional explosion-proof relays

✅ Reverse polarity / surge protection: Fault-tolerant wiring in explosion-proof area, higher safety Moog Inc.

✅ 25 L/min medium flow + built-in pilot: System is simple and maintenance is convenient

✅ Standard leakage + standard dynamics: Cost-effective and highly versatile

Typical applications

Chemical explosion-proof areas: Reactor control, explosion-proof hydraulic station, hazardous area actuators

Oil and gas platforms: Wellhead hydraulic control, intrinsically safe circuits, Zone 0/1 equipment

Dust environment: Aluminum powder / flour / feed processing equipment (dust explosion-proof certification)

Metallurgical explosion-proof conditions: Steel mill explosion-proof area roll gap / tension control