Efficient maintenance of hydraulic units

Why the right filtration is crucial!
May 30, 2025 by
Efficient maintenance of hydraulic units
Carmen Steiner

How does clean oil protect your machine tools and hydraulic power units?

Hydraulic systems are an integral part of modern production facilities - especially in the field of machine tools, where precision, repeat accuracy and availability are crucial. Whether CNC milling machines, lathes or grinding centers: the associated hydraulic units perform central tasks such as clamping hydraulics, feed drives or tool changers..

But how efficient a machine really is also depends on how clean your hydraulic oil is. For maintenance teams, this means that filtration is not a side issue - it is an elementary component of system maintenance and fault prevention.

1. Why is hydraulic filtration so important for machine tools in particular?

Machine tools work with tight tolerances and high demands on precision and repeatability. Even the smallest particles in the oil can:

  • Jamming of switching valves
  • Proportional valves malfunction
  • Make clamping units and pressure accumulators unreliable
  • Falsify or abort positioning
  • Components overheat

Hydraulic power units, which act as a central supply unit, distribute hydraulic oil to several consumers. If the oil is contaminated, the damage affects the entire system, e.g. the main spindle, tool changer, tailstock adjustment or clamping system.

The result:

A seemingly small fault in the unit filter can lead to a complete machine standstill - or to expensive axle and valve repairs.

2. What is the significance of using hydraulic filters on the hydraulic power unit?

Hydraulic power units typically consist of a tank, pump, valve block, control unit - and several filter points. Relevant filter types here are:

Especially for machine tools, where long downtimes are expensive, filter manufacturers such as Filtration Group Industrial or Hengst Filtration often recommend finer filtration (< 6µm) and frequent maintenance intervals - especially for older machines or heavily used units.

3. Error patterns from practise - and how to prevent them with correct filtration

Fault pattern: Tool changer jams sporadically

Cause: Solenoid valve blocked by fine particles

 Solution: Finer pressure filter, regular oil condition analysis

Fault pattern: Clamping cylinder loses holding force

 Cause: Internal leaks due to particle wear

 Solution: Off-line filter, targeted particle counting (ISO 4406)

Fault pattern: CNC axes lose positioning

 Cause: Valve inertia due to deposits

Solution: Proactive filter change before differential pressure alarm


4. Conclusion: Filtration is the protective shield for your hydraulic units & machine availability

In the maintenance of machine tools and hydraulic units, it is not a question of whether to filter - but how consistently. Contaminated oil acts like an abrasive in the system: it destroys slowly but steadily. Those who react early with intelligent filtration, oil monitoring and standardized maintenance plans win:

  • Longer downtimes
  • Planned maintenance instead of unplanned downtimes
  • More stable machine processes
  • Lower spare parts and repair costs

The FILCOM GmbH team recommends the following for maintenance staff in practice:

Create a filter and oil maintenance log for each hydraulic unit with specific inspection intervals, differential pressure limit values and a documented filter change schedule. Use sensor technology where available and train your employees regularly in the subject of hydraulic maintenance.

Rely consistently on high-quality hydraulic filters from our two partners Filtration Group and Hengst Filtration. Both manufacturers stand for reliable industrial quality, high oil purity and long service life. Avoid replicas or no-name filters, as they are often significantly inferior in terms of performance and material quality. If possible, use original manufacturer filter elements from Filtration Group and Hengst Filtration to ensure functionality and warranty.