I. Model Breakdown (D633-303B)

D633: D633 Series Direct Acting Servo Valve (DDV), NG6 (03) Installation Surface

303:

3: Flow Code → 5 L/min (Δp=35 bar) (Minimum Flow Setting of D633)

0: Electronic / Frequency Response → Standard Frequency Response (60–90 Hz), Analog Input, Position Closed Loop

3: Y Port / Seal → No Y Port (Backflow), NBR (Nitrile Rubber) Seal, -20 to +80°C

B: Standard Type, No Special Coating, Standard Voltage Version

In one sentence: D633-303B = NG6 + 5 L/min@35bar + 350bar High Pressure + Direct Acting without Pilot + 60–90Hz Standard Frequency Response + No Y Port (Backflow) + NBR Seal

II. Core Parameters (Δp=35 bar)

Rated Flow: 5 L/min (Minimum of D633 Series)

Maximum Pressure: 350 bar (P/A/B); T Port (No Y): 50 bar

Hysteresis: <0.2%

Resolution: <0.1%

Frequency Response (±100%): 60–90 Hz (Standard Setting)

Step Response: ≈15 ms

Zero Position Leakage: ≈0.05 L/min (210 bar) (Minimal Leakage)

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

Drive: 24VDC, ±10V or 4–20mA

Filter: ISO 4406 15/12

Features: No Pilot Hole, Extremely Strong Anti-Pollution, Independent of Dynamic and Pressure, Spring Retention after Power Off, Ultra-Low Leakage, Compatible with Low Pressure Return Oil

III. D633-303B vs 302B (Core Differences) Table

Project D633-303B (5L standard / without Y) D633-302B (10L standard / without Y)

Flow rate 5 L/min (minimum setting) 10 L/min

Frequency response 60–90 Hz (standard) 60–90 Hz (standard)

Y port No Y port (T ≤ 50bar) No Y port (T ≤ 50bar)

Sealing NBR (-20 to +80℃) NBR (-20 to +80℃)

Zero position leakage ≈ 0.05 L/min (smaller) ≈ 0.1 L/min

Positioning Ultra-low flow, extremely low leakage, precise micro-control Small flow, basic precision control

Sentence: 303B is the "halved flow rate + halved leakage" version of 302B, a minimum flow and lowest leakage model in the D633 series.

Four. Application scenarios

NG6 installation surface, requiring 5L/min ultra-low flow + 350bar high pressure

Low return oil pressure at T port (≤50bar), no Y port leakage required

Standard dynamics (60–90Hz), normal temperature (≤80℃) environment

Ultra-precise micro-control: small test machines, micro feed, precise pressure control, robot micro joints, hydraulic servo micro drives

Highly demanding zero position leakage requirements (<0.1L/min) for low-power systems