During the quality guarantee period of the new car, the filter (filter element) should not be used as a substitute. Even after the quality guarantee period, the filter should be carefully selected. Diesel filter performance in accordance with ISO standards are graded code. In addition to the performance test according to SAE standard, the air filter element should also be tested on the bench to meet the requirements of the original intake resistance of rated air intake of the engine. The qualified oil filter must meet the original design of engine cylinder pressure, oil temperature, flow rate, viscosity and vehicle service conditions, and consider the comprehensive balance of core quality. The hydraulic oil filter element is marked on the product sample or nameplate of the manufacturer is the nominal filtration accuracy, rather than the absolute filtration accuracy. Only the β value measured by the test can represent the filtration capacity of the filter. The hydraulic oil filter element should also meet the requirements of pressure loss (the total pressure difference of the high pressure filter is less than 0.1pMA, and the total pressure difference of the return oil filter is less than 0.05mpa) to ensure the optimization of flow and filter element life.

In the selection of filter (filter element) can choose the original parts, can also choose the second brand. It should be noted that the selected filter element should be accepted to test whether it meets the performance indicators it should have.

1. The air filter element selected must match the power, economy and reliability of the original engine.

(1) The air chlorine flow in the technical parameters of the rated air intake filter element should be greater than the rated air intake of the engine.

(2) The filter material has requirements on the thickness, tension resistance, original intake resistance and filtration accuracy of the filter material. Imported diesel oil requires air filtration accuracy of 5μm, domestic diesel engine should also be less than 20μm. The filtration accuracy of high efficiency filter paper is 2μm, ordinary imported filter paper is 30μm, and domestic filter paper is only 80μm.

(3) Filter element performance test:

Flow-resistance (pressure drop) test to determine the air flow pressure loss (flow-resistance or flow-pressure adit curve).

② The original filtration efficiency test can calculate the dust collection efficiency of the filter element, and the dust removal rate of the normal filter element should be more than 99%.

③ Dust storage capacity test and cumulative efficiency test too much dust accumulation in the filter element will cause blockage and increase the intake resistance. When the engine power decreases by 5% or fuel consumption increases by 5%, the intake resistance is a limit. When this value is reached, the filter element must be cleaned or replaced. During the test, the dust accumulation weight when the intake resistance or pressure drop reaches 7-46kpa is the dust storage capacity of the filter element, and the filtration efficiency during this test is the cumulative efficiency.

(4) The original air intake resistance test air intake resistance 9 rated time air flow through the filter element at the inlet and outlet pressure difference) should not exceed 3.2kpa, but also the power will decrease, the engine will emit black smoke.

2, diesel filter diesel filter according to the ISO4020 standard (road vehicle-automobile diesel engine fuel filter test method) to carry out the following test.

(1) The clearance degree test of the new filter determines whether the inner side of the filter element has cleared the dust and impurities remaining in the production, storage and transportation.

(2) The bubble test is used to confirm whether there are pores in the filter element that are larger than the filtration accuracy.

(3) Filtration efficiency and life test Filtration efficiency refers to the percentage of specific particles that are filtered out, and filter life is expressed as the time when the plugging test pressure difference is greater than 0.07mpa.

(4) Water separation validity test to determine the percentage of water in the oil-water mixture separated by the oil filter.

(5) Filter element damage test to determine the anti-rupture pressure of the filter element.

(6) Oil filter assembly damage test to determine the ability of the assembly to bear internal pressure.

(7) The pulsating pressure fatigue test measures the mechanical strength of the oil filter assembly under pulsating pressure (simulated when the engine is started or stopped).

(8) Anti-vibration fatigue test to determine the anti-vibration mechanical strength of the oil filter under normal service conditions.

3, oil filter full-flow oil filter should be in accordance with ISO4548 standard for the following tests.

(1) Pressure drop – flow characteristic test Determine the pressure drop – flow curve of the oil filter assembly with oil of specified viscosity.

(2) Characteristic test of filter element bypass element to determine the filter element pressure drop – bypass flow curve. When the pressure drop through the filter element is low, in order to limit the amount of unfiltered oil, the bypass element is lower than the specified opening pressure drop, allowing a small amount of oil leakage; When the filter element is completely blocked, the full flow can be bypassed and not exceed the specified pressure drop.

(3) High pressure drop and high temperature characteristics test oil filter in the work (especially when the filter element is blocked) will undergo high pressure drop. In addition, the filter element is also affected by the high temperature of the oil. The ability of the filter element to withstand the high pressure drop without damage should be tested under the simulated high temperature condition.

(4) Filter element life and filtration efficiency test using particle counting method to determine the filter element under orders, the test draw pressure difference – test time or pressure difference – ash weight curve, in order to reach 75% bypass valve design open pressure test time or pollutant weight to express the filter element life.

(5) Cumulative efficiency test using gravimetric analysis method to determine the life of the filter element, to reach the end of the test when the pressure difference or the amount of pollutants captured to assess.

(6) The oil filter in the hydraulic pulse fatigue test should be affected by the fluctuating pressure in the cooling state of the engine. During the test, the specified pulsating oil pressure is used for 1000 cycles to determine the pressure resistance of the oil filter shell, seal ring and filter element under high pressure fluctuation.

(7) After installing the filter assembly, add the frequency and amplitude of resonance caused by the vibration surface of the model engine or installation structure, maintain the specified oil pressure, and cycle 10 million times to determine the performance of no small leakage oil trace or fatigue damage.

4. Hydraulic oil filter element

(1) Filtration accuracy First of all, according to the needs of the hydraulic system to determine the cleanliness level of the stain, and then according to the cleanliness level according to the table to select the filtration accuracy of the oil filter. The nominal filtration clarity of the most commonly used hydraulic oil filter element in construction machinery is 10μm. Because the nominal filtration accuracy can not truly reflect the filtration ability of the filter element, therefore, the maximum diameter of hard spherical particles that the filter can pass under the specified test conditions is often taken as its absolute filtration accuracy, which is used to directly reflect the filtration ability of the initial stage of the newly installed filter element. The main criterion for evaluating the hydraulic oil filter element is the β value measured by ISO4527-1981E(multi-pass test), that is, the oil mixed with the standard test powder repeatedly circulates through the oil filter, the ratio of the number of particles on both sides of the oil inlet and the oil outlet.

(2) Flow characteristics The flow rate and pressure drop of the filter element through the oil are important parameters of flow characteristics. The flow characteristics test should be carried out according to the ISO3968-91 standard to draw the flow-pressure drop characteristics curve. Under the rated oil supply pressure, the total pressure drop (the sum of the pressure drop of the filter shell and the filter element) should be below 0.2mpa.

(3) The strength of the filter element should be in accordance with ISO2941-83 standard for fracture – impact test. When the filter element is damaged, the pressure difference that drops sharply should be greater than the specified value.

(4) Flow fatigue characteristics shall be subjected to 100 000 cycles of fatigue test according to ISO3724-90 standard.

(5) The test of hydraulic oil stress should be carried out according to ISO2943-83 standard pressure flow tolerance test to verify the compatibility of filter material to hydraulic oil.