The ZDR 6 DPO is a pilot-operated, sandwich-plate pressure reducing valve designed for use in hydraulic systems conforming to ISO 4401-03-02-0-05 mounting patterns. Engineered to maintain a constant secondary pressure regardless of fluctuations in the primary circuit, this component utilizes a direct-acting pilot stage to control the position of the main spool. The valve is specifically configured to reduce pressure in port A, B, or P, depending on the specific model variant, and features an integrated pressure relief function to protect the secondary circuit from pressure spikes caused by external loads or thermal expansion. Its compact design and adherence to DIN 24340 standards make it a critical component for modular stack assemblies where space constraints and precise pressure regulation are primary engineering requirements.
For complete selection guidelines and cross-reference documentation on this product line, please consult our Rexroth equivalent hydraulic valves guide.
Technical Specifications and Operational Parameters
The performance of the ZDR 6 DPO is contingent upon maintaining the fluid within the specified viscosity range and adhering to rigorous filtration standards. The following table outlines the critical technical parameters for the valve.
| Parameter | Specification |
|---|---|
| Interface | ISO 4401-03-02-0-05 |
| Max Operating Pressure (Primary) | 315 bar |
| Max Secondary Pressure | Up to 210 bar (spring dependent) |
| Max Flow Rate | 50 L/min |
| Fluid Temperature Range | -30°C to +80°C |
| Viscosity Range | 10 to 800 mm²/s |
Contamination Control and Fluid Cleanliness
Hydraulic systems utilizing the ZDR 6 DPO are sensitive to particulate contamination, which can lead to spool silting or erratic pressure regulation. To ensure the longevity of the pilot poppet and the main spool, the system must maintain a fluid cleanliness level of at least 20/18/15 according to ISO 4406. High concentrations of metallic wear particles or environmental contaminants can cause the spool to stick in the bore, leading to a loss of pressure control or total valve failure. Implementing a beta-rated return line filter and ensuring proper reservoir breathers are essential to mitigating these risks.
Seal Elastomer Compatibility
The ZDR 6 DPO is available with various seal materials to ensure chemical compatibility with different hydraulic media. Standard Nitrile Butadiene Rubber (NBR) seals are suitable for mineral oil-based fluids (HLP/HLPD) within standard operating temperature ranges. However, for applications involving phosphate ester-based fire-resistant fluids (HFD) or high-temperature environments exceeding 80°C, Fluorocarbon Rubber (FKM/Viton) seals are mandatory. Engineers must verify the compatibility of the seal material with the specific fluid additive package to prevent seal degradation, swelling, or hardening, which would compromise the valve’s internal leakage specifications.
Installation and Maintenance Considerations
When integrating the ZDR 6 DPO into a manifold stack, ensure that the mounting surface flatness meets the requirements of ISO 4401 to prevent internal cross-port leakage. The valve should be oriented to allow for the adjustment of the pressure setting screw, which is typically locked via a hex nut. During maintenance, inspect the pilot seat for signs of erosion or cavitation. If the valve fails to maintain the secondary pressure setpoint, the pilot stage should be inspected for debris, and the spring tension should be verified against the manufacturer’s pressure-stage charts.