The Pressure Shut-off Valve DA functions as a pilot-operated, seat-type hydraulic component designed to isolate pressure lines or provide a positive shut-off in high-pressure circuits. By utilizing a poppet-seat geometry, the DA series ensures zero-leakage performance, which is critical for maintaining load holding and preventing pressure decay in accumulators or clamping circuits. Unlike spool-type valves, which are susceptible to internal leakage due to diametrical clearances, the DA valve relies on a hardened, ground poppet sealing against a precision-machined seat, adhering to the functional requirements defined in ISO 1219. This design is particularly effective in systems where volumetric efficiency is paramount and where the thermal degradation of hydraulic fluid must be mitigated by eliminating bypass flow during standby conditions.
For complete selection guidelines and cross-reference documentation on this product line, please consult our industrial hydraulic valves catalog.
For complete selection guidelines and cross-reference documentation on this product line, please consult our industrial hydraulic valves catalog.
Technical Specifications and Operational Parameters
The following table outlines the standard performance metrics for the Pressure Shut-off Valve DA. These values are based on nominal flow rates and standard mineral-based hydraulic fluids.
| Parameter | Specification |
|---|---|
| Mounting Pattern | ISO 4401 / DIN 24340 |
| Max Operating Pressure | 350 bar (5076 PSI) |
| Max Flow Rate | Up to 120 L/min |
| Fluid Temperature Range | -20°C to +80°C |
| Viscosity Range | 10 to 800 mm²/s |
| Seal Material | NBR (Standard) / FKM (Optional) |
Contamination Control and ISO 4406 Compliance
The precision of the poppet-seat interface in a Pressure Shut-off Valve DA necessitates strict adherence to fluid cleanliness protocols. Particulate contamination can cause “seat indentation” or prevent the poppet from achieving a full seal, leading to unintended pressure drops. To ensure operational longevity and prevent premature wear, the hydraulic system must maintain an ISO 4406 cleanliness class of at least 19/17/14.
Failure to maintain these levels can result in siltation, where fine particles accumulate in the pilot passages, potentially causing the valve to stick in the open or closed position. Filtration should be placed upstream of the valve, utilizing a beta-rated filter element (βx ≥ 75) to mitigate the risk of abrasive wear on the hardened seat surfaces.
Seal Elastomer Selection: NBR vs. FKM
Selecting the appropriate seal material is critical for the chemical compatibility and thermal stability of the valve assembly. The standard Nitrile Butadiene Rubber (NBR) seals are suitable for most mineral-oil-based hydraulic fluids operating within standard temperature ranges. However, in applications involving fire-resistant fluids (such as phosphate esters) or high-temperature environments exceeding 80°C, Fluorocarbon (FKM/Viton) seals are mandatory.
FKM provides superior resistance to chemical degradation and prevents the hardening or swelling that can occur with NBR when exposed to synthetic fluids or elevated thermal loads. When replacing seals, ensure the housing grooves are free of debris to prevent damage to the new elastomer, as any surface irregularity can compromise the static seal integrity of the valve body.
Mounting and Installation Standards
The DA valve series is designed for modular integration, typically conforming to ISO 4401 mounting patterns. When installing, it is imperative to ensure the mounting surface flatness meets the requirements of DIN 24340 to prevent body distortion. Excessive torque on mounting bolts can induce mechanical stress, potentially misaligning the poppet seat and causing internal leakage. Always utilize a calibrated torque wrench and follow the manufacturer-specified bolt tightening sequence to ensure uniform pressure distribution across the interface O-rings.