In the hydraulic system, the filter is an important component to ensure the cleanliness of the system, prolong the service life of the equipment and improve the work efficiency. Impurities in hydraulic oil will cause wear, blockage or failure of components, so it is very important to choose a reasonable hydraulic filter for the normal operation of the whole hydraulic system.
First, clear the function and classification of filters
The main function of hydraulic filter is to filter out solid particles in hydraulic oil and prevent pollutants from damaging the system. According to different installation positions, hydraulic filters can be divided into oil absorption filters, pressure oil filters and oil return filters; According to the filter material, it can be divided into metal mesh type, paper type and chemical fiber type. According to the filtration accuracy, it can be divided into coarse filtration, ordinary filtration, fine filtration and ultra-fine filtration.
Second, the key factors of type selection
1. Working pressure and flow demand
The pressure of the hydraulic system determines the pressure-bearing capacity requirements of the filter. For example, in a high-pressure system (such as 31.5MPa), it is necessary to choose a high-pressure resistant filter housing and filter element structure. At the same time, the flow capacity of the filter must meet the flow demand of the system to avoid excessive pressure drop affecting the system efficiency.
2. Filtering accuracy requirements
Different hydraulic components have different requirements for oil cleanliness. For example, servo valves and proportional valves require extremely high cleanliness, and usually require a filtration accuracy of 10μm or even less than 5 μ m. When selecting the type, you should refer to the user manual of key components in the system to determine the required filtration level.
3. Working temperature and medium properties of the system
The viscosity, chemical properties and temperature range of working medium will affect the selection of filter media. Heat-resistant materials should be selected in high temperature environment, and corrosion-resistant filter elements should be considered for corrosive media.
4. Installation location and space constraints
According to the different installation positions of the filter (oil absorption, pressure oil or oil return circuit), the corresponding structural form is selected. At the same time, it is necessary to consider whether the installation space is allowed and whether it is convenient to replace the filter element or carry out maintenance.
5. Maintenance cycle and cost considerations
Some systems require long-term continuous operation. At this time, filters with bypass valves and clogging indicators can be selected to facilitate timely replacement of filter elements and avoid system downtime losses. At the same time, the frequency and cost of filter replacement should be considered to balance the initial investment and long-term operation cost.
III. Reference of Typical Application Cases
For example, in the hydraulic system of construction machinery, the coarse filter (100~125μm) is generally used for oil absorption filter to prevent large particles from entering the pump body and damaging the components; In the servo control system, in order to protect the precision valve core, the oil return filter often uses 3~5μm high precision filter element. In heavy industries such as metallurgy and injection molding, magnetic oil return filters with large flow rate, high temperature resistance and long life are often used to cope with harsh working conditions.
IV. Conclusion
Although the hydraulic filter is small, its selection directly affects the reliability and efficiency of the whole hydraulic system. System parameters, working environment, economy and maintenance convenience should be comprehensively considered in the process of type selection, so as to achieve “tailoring”. Only by choosing the appropriate filter can we truly realize the efficient and stable operation of the hydraulic system and ensure the long-term safe use of the equipment.