I. Meaning of Model Numbers

D631: 631 Series Two-stage Mechanical Feedback Servo Valve

Z: Non-explosion-proof, standard industrial environment

794: Flow Code → 79 L/min @ Δp=35 bar; Last digit 4 = High Response / High Performance Valve Core

C: External Pilot Supply + Special Sealing (High Performance / Wide Temperature) + Low Leakage

In one sentence: Z794C = Non-explosion-proof + 79 L/min Ultra-Large Flow + High Response + External Supply + High Performance Sealing + Low Leakage

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

Rated Flow: 79 L/min (Upper limit of 631 Series Flow, 40% larger than 55L)

Maximum Working Pressure: 315 bar

Frequency Response (−3 dB, 90°): ≈ 65–75 Hz (High Response, 20–30% higher than standard model of 55L)

Step Response (100%): ≈ 18–22 ms

Hysteresis: ≤ 0.25%

Resolution: ≤ 0.08%

Zero-Position Leakage: ≈ 0.35 L/min (Low Leakage, Energy Saving)

Pilot Supply: External (X Port)

Explosion-proof Grade: None (Z = Non-explosion-proof)

Sealing Material: Special High-Performance Sealing (C Type), Temperature -30 ℃ ~ +130 ℃

Filter Requirements: NAS 6 / ISO 4406 <13/10

III. Comparison with 55L Series (556/557/558) (79L Flagship vs 55L Mainstream) Table

Project D631Z794C (79L High Response Elite) D631Z557A (55L High Response Main Model) D631Z558B (55L Standard Economy)

Rated Flow Rate 79 L/min 55 L/min 55 L/min

Frequency Response 65–75 Hz (Ultra High) 55–65 Hz (High) 45–55 Hz (Standard)

Step Response 18–22 ms 25–30 ms 30–35 ms

Hysteresis / Resolution 0.25% / 0.08% 0.25% / 0.08% 0.3% / 0.1%

Zero Position Leakage ≈0.35 L/min (Low) ≈0.40 L/min (Medium) ≈0.50 L/min (Standard)

Sealing / Temperature High Performance (-30~+130℃) FPM (-20~+120℃) NBR (-20~+80℃)

Price Baseline + 50% (Elite) Baseline + 35% (High Configuration) Baseline + 30% (Standard)

In one sentence: Z794C = The highest flow rate + the fastest response + the lowest leakage + the widest temperature range, it is the top flagship model of the 631 series non-explosion-proof servo valve.

Four. Features and Applications Characteristics

✅ 79 L/min ultra-high flow rate: The largest in the 631 series, suitable for ultra-heavy actuators

✅ High response (4): Frequency response of 65–75 Hz, 18–22 ms step, extremely dynamic

✅ External pilot (C): Independent pilot oil supply, flexible system design

✅ High-performance seals (C): Wide temperature range of -30℃ ~ +130℃, resistant to extreme conditions

✅ Low leakage valve core: Zero leakage of 0.35 L/min, significant energy saving during long-term operation

✅ Non-explosion-proof Z-type: Ordinary industrial environment, cost lower than explosion-proof K-type

Typical applications

Ultra-heavy press machines, large forging machines, large-tonnage injection molding machines

Metallurgical hot rolling / cold rolling lines, large rolling mill lowering, thick plate leveling

High-speed dynamic testing equipment, vibration table, high-frequency fatigue test machine

Extreme temperature conditions (low temperature -30℃ / high temperature + 130℃)

High-precision synchronous control, multi-cylinder collaboration, large platform high-speed positioning