I. Explanation of Model Numbers

D631: 631 series two-stage mechanical feedback servo valve, Moog Inc.

Z: Non-explosion-proof, standard industrial environment

803: Flow code → 80 L/min @ Δp=35 bar; Last digit 3 = Low leakage valve core

C: Internal pilot supply oil, FPM (fluorine rubber) seal

Sentence: Z803C = Non-explosion-proof + 80 L/min ultra-large flow + Internal pilot + FPM high-temperature seal + Low leakage energy-saving type

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

Rated flow: 80 L/min (top flow of 631 series)

Maximum working pressure: 315 bar

Frequency response (−3 dB, 90°): ≈ 40–50 Hz (standard response for large flow)

Step response (100%): ≈ 35–40 ms

Hysteresis: ≤ 0.3%

Resolution: ≤ 0.1%

Zero position leakage: ≈ 0.30 L/min (low leakage, type 3)

Pilot supply oil: Internal (no external X port required)

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

Sealing material: FPM (fluorine rubber), -20 ℃ ~ +120 ℃

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

III. Comparison of 803C with 55L Series (Flow Upgrade) Table

Project D631Z803C (80L Internal Direct Flow Low Leakage FPM) D631Z558A (55L External Direct Flow Standard FPM)

Rated Flow Rate 80 L/min 55 L/min

Frequency Response 40–50 Hz (High Flow Standard) 45–55 Hz (Standard)

Pilot Mode Internal (No External Connection Required) External (Requires X Port Connection)

Zero-Position Leakage ≈0.30 L/min (Low Leakage) ≈0.50 L/min (Standard)

Sealing / Temperature FPM (-20~+120℃) FPM (-20~+120℃)

Price Baseline + 40% (High-End High Flow Configuration) Baseline + 30% (Standard)

In one sentence: 803C = Full Flow Capacity (80L) + Internal Pilot without External Wiring + Lower Leakage for Energy Savings + High Temperature FPM Sealing

Four. Features and Applications Characteristics

✅ 80 L/min ultra-high flow rate: 631 series flow ceiling, compatible with ultra-heavy-duty actuators

✅ Internal pilot (C): No need for external pilot oil circuit, simplifying the system and reducing costs

✅ Low leakage valve core (3): Zero leakage is only 0.30 L/min, saving electricity and energy during long-term operation

✅ FPM seal (C): Resistant to high temperatures and corrosion, reliable in harsh conditions of -20 to +120℃

✅ Non-explosion-proof Z-type: Suitable for ordinary industrial environments, with lower cost than explosion-proof K-type

Typical applications

Ultra-heavy-duty presses, large forging machines, giant injection molding machines for mold locking / injection

Metallurgical thick plate rolling, large hydraulic cylinder synchronous drive, heavy platform positioning

High-temperature conditions (+100℃) + Long waiting time (low leakage and energy-saving requirements)

Internal pilot system (simplified design, fewer leakage points)