What is a hydraulic filter

The filter is to filter out the pollutants in the water to purify the water, and the hydraulic filter is in the hydraulic system, which collects the pollutant particles in the fluid and is collectively referred to as the hydraulic filter. Next, let's take a look at the specific role of hydraulic filters.

The specific function of hydraulic filter

It is to filter various impurities in the hydraulic system. The main sources are mechanical impurities remaining in the hydraulic system after cleaning, such as rust, casting sand, welding slag, iron filings, paint, paint skin and cotton yarn scraps, etc., and impurities entering the hydraulic system from outside, such as through the oil filler and anti-corrosion. The dust entering the dust ring, etc.; the impurities generated during the working process, such as the debris formed by the hydraulic action of the seal, the metal powder generated by the relative wear of the movement, the colloid, asphaltene, and carbon residue generated by the oil due to oxidation and deterioration.

There are many ways to collect pollutants in fluids. Devices made of filter materials to capture pollutants are called filters. Magnetic filters that use magnetic materials to adsorb magnetic pollutants are called magnetic filters. In addition, there are electrostatic filters, separation filters and so on. In the hydraulic system, any collection of pollutant particles in the fluid is collectively referred to as a hydraulic filter. In addition to the method of using porous materials or wound fine gaps to intercept pollutants, the widely used hydraulic filters also include magnetic filters and electrostatic filters used in hydraulic systems.

After the above impurities are mixed into the hydraulic oil, with the circulation of the hydraulic oil, it will play a destructive role everywhere, seriously affecting the normal operation of the hydraulic system, such as making small gaps (measured in μm) and joints between the relatively moving parts in the hydraulic components. The flow holes and gaps are stuck or blocked; the oil film between the relatively moving parts is destroyed, the surface of the gap is scratched, the internal leakage is increased, the efficiency is reduced, the heat is increased, the chemical action of the oil is aggravated, and the oil is deteriorated. According to production statistics, more than 75% of the failures in the hydraulic system are caused by impurities mixed in the hydraulic oil. Therefore, it is very important for the hydraulic system to maintain the cleanliness of the oil and prevent the pollution of the oil.

General hydraulic filter is mainly composed of filter element (or filter screen) and shell (or skeleton). The flow area of the oil is composed of numerous tiny gaps or pores on the filter element. Therefore, when the size of impurities mixed into the oil is larger than these tiny gaps or pores, they are blocked and filtered out of the oil. Since different hydraulic systems have different requirements, it is impossible to completely filter the impurities mixed into the oil, and sometimes it is not necessary.

Technical requirements for hydraulic filters

1) The filter material should have a certain mechanical strength to ensure that it will not be damaged by the action of hydraulic pressure under a certain working pressure. (2) Under a certain working temperature, the performance should be kept stable; it should have sufficient durability. (3) It has good anti-corrosion ability. (4) The structure is as simple as possible and the size is compact. (5) Easy to clean and maintain, easy to replace the filter element. (6) Low cost. The working principle of the hydraulic filter: as shown in the figure, the working principle of the filter is simplified. The hydraulic oil enters the pipeline from the left to the filter, flows from the outer filter element to the inner core, and then flows from the outlet to the filter.

When the outer filter element is blocked, the pressure increases, and when the opening pressure of the overflow valve is reached, the oil passes through the overflow valve, reaches the inner core, and then flows out from the outlet. The outer filter element has higher precision than the inner filter element, and the inner filter element belongs to Coarse filtration. Hydraulic filter experimental method: At present, the international standard ISO4572 has been widely adopted in various countries in the world to evaluate the "multiple-pass method of hydraulic filter element filtration performance". properties and nugget capacity. The multiple-pass method simulates the actual working conditions of the filter in the hydraulic system. The pollutants continuously invade the system oil and are continuously filtered out by the filter, while the particles that cannot be filtered out return to the fuel tank and pass the filter again. device. In order to meet the needs of high-precision filter performance evaluation, and due to the change of test dust and the adoption of new calibration methods for automatic particle counters, ISO4572 has been revised and improved in recent years. ISO16889.