What functions does the built-in bypass valve of a HYDAC filter element perform?

The built-in bypass valve of HYDAC filter elements serves as a safety protection component for filters and fulfills three core functions by opening at preset differential pressure.

Firstly, the valve opens when contaminant buildup clogs the filter and differential pressure hits the set point, allowing hydraulic oil to bypass the filter medium directly. This prevents full flow blockage that would overload the oil pump and spike system backpressure, enabling non-stop equipment operation, which is critical for metallurgical and construction machinery where mid-operation shutdown for maintenance is impractical.

Secondly, it protects filter media against high-pressure damage. Without a bypass valve, full clogging pressure would bear entirely on glass fiber media and inner support cages, leading to medium collapse or rupture. Detached fiber fragments carried by oil would scratch valve spools and plungers; the bypass relieves pressure and confines the element load within a safe range.

Thirdly, it optimizes cold startup performance. Hydraulic oil viscosity rises sharply at low ambient temperatures, resulting in elevated idle differential pressure even with brand-new filters. Partial bypass opening assists fluid circulation and avoids pump cavitation and abnormal noise from insufficient oil intake.

Conventional return filter bypass cracking pressure is approximately 0.3 MPa, lower than the differential pressure alarm threshold. Replacement should be carried out upon alarm alerts, with bypass activation only as a fallback for delayed maintenance. A notable drawback is unfiltered contaminated oil flowing straight into the tank once the bypass opens, so prolonged operation relying on open bypass is prohibited.