I. Model Breakdown Explanation (D633-308B)

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

308:

3: Flow code → 40 L/min (Δp=35 bar)

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

8: Y port / Seal → No Y port (backflow), NBR seal, -20 to +80℃

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

In one sentence: D633-308B = NG6 + 40 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: 40 L/min (maximum for D633 without Y port)

Maximum pressure: 350 bar (P/A/B); T port (without Y): 50 bar

Hysteresis: <0.2%

Resolution: <0.1%

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

Step response: ≈12 ms (Moog Inc.)

Zero leakage: ≈0.4 L/min (210 bar)

Seal / Temperature: NBR (-20 to +80℃)

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

Filter: ISO 4406 15/12

Features: Small pilot hole, extremely anti-pollution, independent of dynamic and pressure, spring alignment in case of power failure, no Y port low-pressure return oil, maximum flow for D633 with small mounting surface

III. Comparison of D633-308B with 302B/303B/304B Table

Project 303B (5L) 302B (10L) 304B (20L) 308B (40L)

Flow rate 5 L/min 10 L/min 20 L/min 40 L/min

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

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

Zero position leakage ≈0.05 L/min ≈0.1 L/min ≈0.2 L/min ≈0.4 L/min

Positioning Ultra-low flow micro-control Small flow basic type Middle-small flow main type NG6 maximum flow type

One sentence: 308B is the "double flow rate" version of 304B. The D633 without Y port series has an upper flow limit.

Four. Application scenarios

NG6 small installation surface, requiring 40 L/min large flow + 350bar high pressure

T port return oil pressure low (≤50bar), no need for Y port leakage

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

Medium and small power high-pressure precision control: medium-sized presses, injection molding machines, bending machines, pipe bending machines, wood presses, metallurgical actuators, testing machines

Installation space limited but requires large flow in high-pressure systems