The hydraulic oil filter element is marked on the product sample or nameplate of the manufacturer as the nominal filtration accuracy, not the absolute filtration accuracy. Only the β value measured by the test can indicate the filtration capacity of the filter. The hydraulic oil filter element should also meet the pressure loss requirements (the total pressure difference of the high-pressure filter is less than 0.1PMa, and the total pressure difference of the oil return filter is less than 0.05MPa), so as to ensure the optimization of the flow rate and the life of the filter element. So how do we choose the hydraulic oil filter correctly?
You need to consider the following aspects:
1. Filtration accuracy
First, determine the cleanliness level of the stains according to the needs of the hydraulic system, and then select the filtration accuracy of the oil filter according to the cleanliness level according to the symbol table. The nominal filtration clarity of the most commonly used hydraulic oil filter element on construction machinery is 10 μm. Hydraulic oil cleanliness (ISO4406) Nominal filtration accuracy of the filter element (μm) Application range 13/103 Hydraulic servo valve (with 3μm filter element) 16/135 Hydraulic proportional valve (with 5μm filter element) 18/1510 General hydraulic components ( >10MPa) (use 10μm filter element) 19/1620 general hydraulic components (<10MPa) (use 20μm filter element)
Since the nominal filtration accuracy cannot truly reflect the filtration capacity of the filter element, the diameter of the largest hard spherical particle that the filter can pass through under the specified test conditions is often used as its absolute filtration accuracy to directly reflect the initial filtration of the newly installed filter element. The most important criterion for the ability to evaluate the hydraulic oil filter element is the β value measured according to ISO4572-1981E (multi-pass test), that is, the oil mixed with the standard test powder is circulated through the oil filter for many times, and the oil inlet and outlet on both sides The ratio of the number of particles to .
2. Flow characteristics
The flow and pressure drop of the filter element through the oil are important parameters of the flow characteristics. The flow characteristic test should be carried out according to the ISO3968-91 standard to draw the flow-pressure drop characteristic curve. Under the rated oil supply pressure, the total pressure drop (the sum of the filter housing pressure drop and the filter element pressure drop) should generally be below 0.2MPa. Maximum flow: 400lt/min Oil viscosity test: 60to20Cst Minimum flow turbine: 0℃60lt/min Maximum flow turbine: 0℃400lt/min
3. Filter element strength
The rupture-impact test shall be carried out according to the ISO2941-83 standard. When the filter element is damaged, the pressure difference that drops sharply should be greater than the specified value.
4. Flow fatigue characteristics
The fatigue test shall be carried out according to the ISO3724-90 standard. Filter elements must undergo a fatigue test of 100,000 cycles.
5. Test of adaptability to hydraulic oil
The pressure flow withstand test should be carried out according to the ISO2943-83 standard to verify the compatibility of the filter material to the hydraulic oil.
The filtration ratio b ratio refers to the ratio of the number of particles larger than a given size in the fluid before filtration to the number of particles larger than a given size in the filtered fluid. Nb = number of particles before filtration Na = number of particles after filtration X = particle size.
