Model Code Decoding

• D635: Core series, NG06 mounting pressure control valve

• Z: Enhanced special version, extended temperature, upgraded EMC protection, factory performance tuning

• 681: 40 L/min rated flow, 350 bar maximum operating pressure, standard linear 3-way spool

• E: Revision E, FPM (Viton) seals, 24 VDC power supply, improved electronic circuit

Technical Specifications

• Part Number: D635-Z681E

• Valve Size: NG06 (Cetop 3 / ISO 4401-03)

• Control Function: 3-way pressure control, spring centered

• Rated Flow (Δp=35 bar per land): 40 L/min, tolerance ±10%

• Max Flow: 50 L/min

• Operating Pressure: P/A/B ports 350 bar; Standard T port 50 bar; Optional Y drain port up to 350 bar

• Step Response Time (0 to 100%): ≤12 ms

• Hysteresis: <0.1%

• Linearity: <0.3%

• Null Shift (ΔT=55 K): <0.8%

• Electrical Data: Power supply 24 VDC (19 VDC ~ 32 VDC), maximum current 1.2 A; Command signal ±10 VDC; Pressure feedback 4-20 mA; Connector 6+PE, protection class IP67 when mated

• Hydraulic Fluid: Mineral oil per DIN 51524, kinematic viscosity 5 ~ 400 mm²/s

• Ambient Temperature Range: -20 °C to +65 °C

• Fluid Temperature Range: -20 °C to +85 °C

• Weight: Approximately 2.6 kg

• Seal Material: FPM (Viton)

Interface & Communication Configuration

• Electrical Interface: ±10 V analog command signal plus 24 VDC power supply; 4-20 mA pressure feedback output

• Feedback System: Integrated high-precision pressure sensor, built-in closed-loop control, no external transducer required

• Mounting Pattern: 4-hole NG06 standard mounting, M5 bolts, tightening torque 8 ~ 10 Nm

• Port Configuration: P, A, B, T main ports; Y drain port available as option for high backpressure application

Core Functions

1. High pressure resistance up to 350 bar, suitable for extreme working conditions

2. 40 L/min high flow capacity for medium and large hydraulic actuators

3. Direct-drive linear motor structure, no pilot oil required, stable dynamic performance

4. Integrated pressure sensor and control electronics, simplified system design

5. Ultra-low hysteresis and excellent linearity for precise pressure regulation

6. Extended temperature range and IP67 protection for harsh industrial environments

7. Spring centered fail-safe design to ensure system safety upon power loss

Application Scenarios

• Heavy-duty hydraulic presses, forging and stamping equipment

• High-pressure industrial test benches and component durability test systems

• Large injection molding machines for high-pressure clamping control

• Hydraulic power units for oil, gas and marine industry

• Aerospace hydraulic simulation and ground test facilities

Compatibility Note

• Mechanical interchangeable with all standard D635 NG06 series valves including D635-640E, D635-671E

• Difference from standard D635-681E: D635-Z681E features extended temperature range, IP67 protection, enhanced EMC and better overall stability

• Can be used as a direct performance upgrade for conventional D635 pressure servo valves