Knowledge Center

How to choose filter in hydraulic system?

hydraulic filters

Filter in hydraulic system plays a vital role. It can effectively remove solid pollutants in the working medium and ensure the cleanliness of the working medium, thereby extending the service life of system components and ensuring the reliable operation of hydraulic components. According to statistics, about 75% of hydraulic system failures are caused by contamination of the working medium. Therefore, filter in hydraulic system is an indispensable key auxiliary component.

With the widespread application of hydraulic technology, the maintenance and operation costs of hydraulic systems have also increased accordingly. In order to reduce costs, designers and maintenance personnel need to carefully weigh various parameters when selecting filters. The performance of filters is different, and their filtration mechanisms have their own characteristics. When selecting a filter, attention should be paid to considering the main parameters such as filter material compatibility, filtration accuracy, flow pressure difference characteristics, and filter element strength.

filter in hydraulic system

Compatibility of filter element materials

In order to ensure the service life of the filter element, the filter element material must have good compatibility with the working medium of the hydraulic system. Good compatibility means that the filter element material cannot soften or melt due to the heat of the working medium. In addition, under the influence of acids, alkalis and other chemicals, the function of the filter element material should not quickly become brittle or brittle. Swelling, softening, decomposition and other phenomena.

Choice of filter precision for filter in hydraulic system

The selection of filtration precision should comprehensively consider various factors such as the working pressure of the hydraulic system, load characteristics, working environment, component pollution sensitivity, component replacement costs, system life requirements, safety requirements and downtime costs. For systems with high working pressure, harsh working environment, high sensitivity to component contamination, high component costs, high system service life index, high safety, and high downtime costs, filters with high filtration accuracy should be used.

Determination of filter size for filter in hydraulic system

There is a corresponding relationship between the size of the filter and the flow rate. Generally, determine the filter’s flow rate based on the system’s requirements, and then establish the filter size. In order to extend the service life of the filter element and avoid frequent replacement of the filter element, when actually selecting the filter size, its rated flow rate should be greater than the system flow rate. The flow rate increase multiple determines this coefficient. The selection steps are as follows:

(1) Classify environmental levels according to environmental pollution conditions and the degree of control of pollutant intrusion.

(2) After determining the environmental level, determine the flow increase multiple based on the maximum allowable pressure difference of the selected filter and the installation position of the filter in the hydraulic system. The greater the number of environmental levels, the greater the required flow rate increase.

Application example: The area ratio of the hydraulic cylinder of a certain hydraulic machine is 4:1 and is supplied by a pump station with a flow rate of 70L/min. The filter can be installed in the oil inlet or return line. The size of the filter is selected according to these conditions.

Flow pressure differential characteristics

Consider the filter’s pressure difference characteristics thoroughly during the selection process. Filters with different filtration precision have different pressure difference characteristics. When the flow rate is constant, the higher the precision of the filter, the higher the pressure difference. The pressure difference of the selected filter cannot exceed the allowable value of the corresponding pipeline.

The viscosity-temperature characteristics of the system’s working medium will affect the filter’s flow and pressure differential characteristics. As the temperature changes, the viscosity of the working medium will change. And the flow and pressure difference characteristics of the filter will also change. Follow these principles for filter selection:

(1) Hydraulic systems with high working medium viscosity, low temperature, and high filtration accuracy requirements should choose non-metallic depth filter elements. Hydraulic systems with low system filtration accuracy requirements mostly choose filter elements made of metal surface filter materials.

(2) Hydraulic systems with high medium temperature, slightly larger viscosity, and high filtration accuracy requirements mostly use metal depth filters, such as metal wire sintered mesh filters, metal powder sintered filters, etc.

(3) Select metal surface filters like plain square hole mesh for high-temperature, high-viscosity hydraulic systems with low filtration accuracy requirements.

(4)Select non-metallic depth filters (e.g., wood pulp, chemical fiber, glass fiber) for low-temperature, low-viscosity systems with high filtration precision.


In summary, proper selection of filters is essential to maximize their functionality, control hydraulic system contamination. And improving the reliability and working life of the system and components. We recommend Btlas hydraulic filters to ensure hydraulic system operates efficiently, maximize contamination control, and improve system reliability and lifespan. In hydraulic system design and maintenance, meticulous filter selection ensures the system’s robust and healthy operation.

Reference blog: Hydraulic Filter Elements.Oil filter elements : improve hydraulic system performance!Donaldson Hydraulic Filters VS Btlas Hydraulic Filters.What is the difference between hydraulic oil filters and oil filter elements?Selection and location of hydraulic filter.Hydraulic Filters: A Basic Guide.How to Clean and Change Hydraulic Filter in 3 Easy Steps.Demystifying Hydraulic Filters: Your Comprehensive Guide to Functionality and Maintenance.

Related Posts

Leave a Reply