The DB.K series pressure relief valves are pilot-operated hydraulic components designed for the regulation of system pressure in industrial and mobile applications. Engineered in accordance with ISO 5781 mounting patterns, these valves utilize a two-stage design comprising a main stage poppet and a pilot stage control element. The pilot stage regulates the pressure differential across the main spool, ensuring stable pressure maintenance and rapid response to transient pressure spikes. By integrating a pilot-operated architecture, the DB.K series minimizes the impact of flow-induced force variations on the main poppet, thereby providing a flat pressure-override curve and high volumetric efficiency across the rated flow range.
For complete selection guidelines and cross-reference documentation on this product line, please consult our Rexroth equivalent hydraulic valves guide.
For complete selection guidelines and cross-reference documentation on this product line, please consult our Rexroth equivalent hydraulic valves guide.
Technical Specifications and Performance Parameters
The following table outlines the critical operational parameters for the DB.K series. These values are predicated on a fluid viscosity of 46 cSt at 40°C.
| Parameter | Specification |
|---|---|
| Mounting Pattern | ISO 5781 / DIN 24340 |
| Max Operating Pressure | 350 bar |
| Max Flow Rate | Up to 400 L/min |
| Hysteresis | < 2% of max pressure |
| Fluid Temperature Range | -20°C to +80°C |
| Viscosity Range | 10 to 500 mm²/s |
Hydraulic Design and Operational Stability
The DB.K series employs a balanced spool design to mitigate the effects of Bernoulli forces. The pilot stage consists of a spring-loaded cone seated against a precision-machined orifice. When system pressure exceeds the spring force setting, the pilot cone unseats, creating a pressure drop across the main spool control orifice. This imbalance forces the main poppet to open, bypassing excess fluid to the tank port.
To ensure optimal performance, the pilot stage geometry is optimized to prevent oscillation—a common phenomenon in high-pressure relief applications. Users should verify that the pilot drain line is routed directly to the reservoir with minimal backpressure, as any pressure in the tank line is additive to the valve’s cracking pressure setting.
Contamination Control and Seal Integrity
Fluid Cleanliness Requirements
As with all pilot-operated hydraulic valves, the DB.K series is sensitive to particulate contamination. Spool silting can occur if the fluid cleanliness does not meet the required standards, leading to sluggish response times or valve sticking. It is recommended that systems utilizing DB.K valves maintain a cleanliness level of at least ISO 4406 19/17/14. Filtration should be placed upstream of the valve to protect the pilot orifice, which typically features a diameter of less than 0.8 mm.
Elastomer Compatibility
The standard configuration for DB.K valves utilizes NBR (Nitrile Butadiene Rubber) seals, which are suitable for mineral oil-based fluids. However, in applications involving phosphate ester fluids or high-temperature environments exceeding 80°C, FKM (Viton) seals are mandatory. FKM provides superior chemical resistance and thermal stability, preventing seal degradation and internal leakage that would otherwise compromise the valve’s pressure-holding capability. When retrofitting or performing maintenance, verify the seal material against the fluid safety data sheet (SDS) to prevent elastomer swelling or hardening.