What are the three common technical causes of excessive differential pressure of HYDAC filter elements?

Excessively high differential pressure of HYDAC filter elements, excluding normal clogging from accumulated contaminants, mainly stems from three technical factors: improper filter selection, abnormal hydraulic oil properties and unreasonable installation & operating conditions. These three items shall be prioritized during on-site troubleshooting.

First, improper parameter selection of filter elements. If the rated flow is not specified to be at least 1.2 times the system peak flow during selection, the filter will feature insufficient flow area. Actual flow exceeding design specifications raises fluid velocity and baseline differential pressure directly. In some applications, over-fine 3 μm or 5 μm filter media are unnecessarily adopted, whose dense pores drastically increase flow resistance. Without viscosity compensation for low-temperature service, rising oil viscosity further reduces available flow capacity. Even brand-new unused filters show abnormally high idle differential pressure, which accelerates sharply once contaminants build up later.

Second, deteriorated hydraulic oil leads to pore blockage. HYDAC performance ratings are referenced to hydraulic oil at standard viscosity of 32 mm²/s. Cold startup with overly low oil temperature boosts fluid viscosity and flow resistance, triggering temporary pressure rise. Water ingression causes oil emulsification while oil oxidation generates sticky sludge, which adheres tightly to filter surfaces and blocks pores far faster than solid particles, pushing differential pressure close to bypass opening pressure rapidly. Besides, contaminants such as rubber fragments and flaked paint get trapped inside filter pores, continuously reducing effective filtration area and resulting in persistently elevated differential pressure.

Third, structural defects in filter installation and piping. Inverted filter installation or deformed sealing rings restrict oil passage and create localized throttling with abnormal pressure drop. Undersized inlet/outlet piping and excessive elbows add extra pipeline pressure loss superimposed on element differential pressure and backpressure. Frequent start-stop cycles and variable-frequency load shocks produce instantaneous peak flow beyond rated capacity, leading to chronically excessive dynamic differential pressure. In individual cases, rusted and stuck bypass springs fail to open for pressure relief; trapped pressure after filter clogging cannot be diverted and may rupture filter media under extreme compression.

Routine maintenance shall check selection, oil quality and installation sequentially to quickly pinpoint root causes of high differential pressure.