I. Model Breakdown (D633-304B)

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

304:

3: Flow code → 20 L/min (Δp = 35 bar)

0: Electronic / Frequency response → Standard frequency response (60–90 Hz), analog input, position closed-loop, Moog Inc.

4: Y port / Seal → No Y port (backflow), NBR seal, -20 to +80°C, Moog Inc.

B: Standard type, no special coating, standard voltage version

In one sentence: D633-304B = NG6 + 20 L/min@35bar + 350bar high pressure + direct actuation without pilot valve + 60–90Hz standard frequency response + no Y port (backflow) + NBR seal

II. Core Parameters (Δp = 35 bar)

Rated flow: 20 L/min

Maximum pressure: 350 bar (P/A/B); T port (no Y): 50 bar, Moog Inc.

Hysteresis: <0.2%

Resolution: <0.1%

Frequency response (±100%): 60–90 Hz (standard gear), Moog Inc.

Step response: ≈12–15 ms, Moog Inc.

Zero leakage: ≈0.2 L/min (210 bar)

Seal / Temperature: NBR (-20 to +80°C), Moog Inc.

Drive: 24VDC, ±10V or 4–20mA, Moog Inc.

Filter: ISO 4406 15/12

Features: No pilot hole, strong anti-pollution, independent of dynamic and pressure, spring return to center when power is off, internal leakage design (T port low pressure)

III. Comparison of D633-304B with 302B/303B (Key Differences) Table

Project D633-303B (5L) D633-302B (10L) D633-304B (20L)

Flow rate 5 L/min 10 L/min 20 L/min

Frequency response 60–90 Hz 60–90 Hz 60–90 Hz

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

Sealing NBR NBR NBR

Zero leakage ≈0.05 L/min ≈0.1 L/min ≈0.2 L/min

Positioning Ultra-low flow micro-control Small flow basic type Middle-small flow main type

Sentence: 304B is the "double flow rate" version of 302B, the largest flow rate model in the D633 without Y port series.

Four. Application scenarios

NG6 installation surface, requiring 20 L/min medium-low flow + 350bar high pressure

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

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

Medium-low power precision control: medium-sized presses, injection molding machines small cylinders, testing machines, robot joints, metallurgical actuators

High anti-pollution requirements, simple maintenance