I. Explanation of Model Number

D633: D633 series direct-acting (DDV) servo valve, NG6 (03) mounting surface

183:

1: Flow code → 25 L/min (Δp = 35 bar)

8: Electronic / Feedback version → Standard frequency response (60–90 Hz), analog input, position closed-loop

3: Y port configuration → No Y port (leak back to T), standard seal

B: NBR (nitrile rubber) seal, -20 to +80°C

Sentence: D633-183B = NG6 mounting surface + 25L/min@35bar + 350bar high pressure + direct actuation without pilot + analog control + NBR seal

II. Core Parameters (Δp = 35 bar / throttling edge)

Rated flow: 25 L/min

Maximum pressure (P/A/B): 350 bar

Hysteresis: <0.2% (extremely high precision)

Resolution: <0.1%

Frequency response (±100% signal): 60–90 Hz

Step response (0→100%): ≈15 ms

Zero leakage: ≈0.3 L/min (210 bar)

Drive: 24VDC, ±10V or 4–20mA

Seal / Temperature: NBR (-20 to +80°C)

Filter: ISO 4406 15/12 (NAS 7)

Features: No pilot stage, strong anti-pollution, independent of dynamic and pressure, spring alignment in case of power failure

III. Key Differences between D633-183B and D632 Series Table

Comparison item: D633-183B (Direct-acting Servo)  vs. D632 Series (Two-stage Proportional)

Drive method: Direct-acting linear force motor (without pilot)  vs. Two-stage nozzle baffle (internal / external pilot)

Installation surface: NG6 (03, small size)  vs. NG10 (05, large size)

Flow rate: 25 L/min (35 bar)  vs. 38 L/min (10 bar)

Pressure rating: 350 bar (higher)  vs. 280 bar

Accuracy: Hysteresis < 0.2%, Resolution < 0.1%  vs. Hysteresis 3–5%, Resolution 0.8–1%

Anti-pollution: Extremely strong (no small holes)  vs. General (pilot holes prone to clogging)

Dynamic: 60–90 Hz, 15 ms  vs. 40–60 Hz

Price: Servo level (higher)  vs. Proportional level (lower)

In one sentence: D633-183B is a small-sized, high-precision, high-pressure, and highly anti-pollution direct-acting servo valve; D632 is a large-sized, medium-high precision, medium-high pressure two-stage proportional valve.

IV. Application scenarios (D633-183B)

High-precision position / speed / force control: Precision injection molding, die-casting, testing machines, robots

High pressure (≤350 bar) + medium-small flow rate (25 L/min)

General oil contamination control, not requiring frequent maintenance (no pilot small holes)

High dynamic requirements (>50 Hz), fast response (≈15 ms)

Power-off safety alignment, preventing runaway

NG6 installation surface, compact space