The Rexroth R900404754 (Model: ZDR 6 DP2-4X/150YM/12) is a direct-operated, high-performance pressure-reducing valve designed for sandwich plate mounting. It is used in hydraulic systems to maintain a constant, reduced secondary pressure regardless of fluctuations in the primary system pressure. This valve is part of the ZDR 6 series, known for its reliability in managing pressure in specific branch circuits.

Product Technical Specifications

• Series: ZDR 6 (Size 6 / D03)
• Part Number: R900404754
• Adjustment Type: Mechanical (Internal hexagon with protective cap)
• Maximum Operating Pressure: 350 bar (Input)
• Pressure Adjustment Range: 5 – 150 bar
• Maximum Flow: 50 l/min
• Weight: 1.44 kg
• 原产地 (Country of Origin): Germany / United States
• Seal Material: NBR (Nitrile Butadiene Rubber)
• Hydraulic Fluid: HL, HLP, HLPD, HVLP, HVLPD, HFC

 

Mechanical Installation Requirements

• 固定方式 (Mounting): Designed for sandwich plate mounting (ISO 4401-03-02-0-05 / NFPA T3.5.1 D03 pattern). Ensure the mating surface is clean and flat to prevent leakage.
• 空间距离 (Clearance): Allow at least 50mm of clearance around the adjustment mechanism for the use of a wrench or screwdriver.
• 散热间距 (Thermal Spacing): While hydraulic valves generally do not require specific thermal spacing, ensure the installation area is free from excessive external heat sources to maintain seal integrity (within –30°C to +80°C range).

 

Electrical Wiring & Grounding

• 端子定义 (Terminal Definitions): This is a mechanical hydraulic valve; it does not require electrical connections or solenoid wiring.
• Pressure Gauge Connection: A G1/4 port is provided for secondary pressure monitoring. Use a compatible hydraulic pressure gauge to verify the setting.
• 接地规范 (Grounding Norms): Not applicable for this purely mechanical model. Ensure the entire hydraulic power unit (HPU) is properly bonded to a site ground to prevent static buildup.

 

Configuration & Setup

• Pressure Setting: To adjust the secondary pressure, loosen the lock nut (SW24) and turn the adjustment screw (SW10) clockwise to increase pressure or counter-clockwise to decrease it. Retighten the lock nut after reaching the desired value.
• Internal Pilot: This model uses internal pilot oil supply and external pilot oil return through Port T (Y).

 

Frequently Asked Questions (Q&A)

Q: What does the “150” in the model number signify?

A: It indicates the maximum pressure setting range of the valve, which in this case is 150 bar.

Q: Can I mount this valve in any orientation?

A: Yes, the valve can be installed in any position without affecting its operational performance.

Q: Does this valve include a check valve?

A: This specific model (version “M”) is a standard pressure-reducing valve; ensure you check your system diagram to see if a version with an integrated check valve (version “A”) is required for your specific flow requirements.

Q: What should I do if the pressure is unstable?

A: Instability is often caused by trapped air in the pilot chamber or contamination in the fluid. Bleed the air from the system and ensure the hydraulic fluid meets the ISO 4406 cleanliness class 20/18/15.