What are the main causes for the rapid rise in operating differential pressure of Mahle filter elements?

Excessive system contaminants cause rapid surface blockage of filter media.

Mahle’s multi-layer graded glass fiber media stores contaminants layer by layer under normal conditions; ordinary impurities penetrate into the inner media and build up slowly with a steady rise in differential pressure. However, massive inflows of fine dust, rusted iron filings and rubber seal debris lodge directly in surface pores instead of penetrating deep into the medium, quickly blocking the effective flow area. Abrupt surges of contaminants commonly occur during new equipment commissioning, due to residual pickling waste left inside pipelines or dust and water ingress via defective tank seals, pushing differential pressure past the alarm threshold within only a few days. Besides, flaky impurities from peeling inner tank paint and corroded pipeline linings can blanket the outer filter surface and trigger sharp pressure spikes.

Degraded hydraulic oil forms sticky sludge adhering to filter pores.

Mahle filter media is designed for standard mineral-based hydraulic oil. Water ingress leading to emulsification or high-temperature oxidation generates viscous sludge and zinc soap deposits featuring strong adhesion, which stick firmly inside glass fiber pores and resist flushing by flowing oil. At low temperatures, water-contaminated oil gains higher viscosity and poorer fluidity, accelerating sludge buildup and pore clogging. Using inferior off-spec hydraulic oil or incompatible mixed oil grades speeds up fluid deterioration. Unlike particulate fouling, sludge can drive differential pressure close to bypass opening pressure after merely hundreds of operating hours, ranking as the most frequent on-site failure cause for abrupt pressure rise.

Improper filter sizing and fluctuating operating conditions exceed rated design parameters.

If the filter’s rated flow is less than 1.2 times the system peak flow during selection, excessive flow velocity accelerates clogging dramatically under identical contamination levels. Unnecessary specification of ultra-fine 3 μm media with dense pores also cuts down dirt holding capacity drastically. During cold startup, oil viscosity far exceeds the calibrated 32 mm²/s, producing instant high flow resistance and temporary differential pressure surge. Frequent machine start-stop cycles and hydraulic shocks create transient overflows that compact accumulated contaminants faster. In rare cases, misaligned or reversely installed filters force reverse oil flow against the media, speeding up contaminant accumulation and resulting in abnormally rapid differential pressure climb.