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Verification method of filtration efficiency

by:GESTER Instruments     2021-03-30
Air filtration efficiency generally refers to the air filter's 'filtration efficiency is the ratio of the amount of dust captured to the original air dust content. The actual meaning and specific value of the filter efficiency are very different due to different test methods. General ventilation filtration Mechanical test method The counting method test bench is similar to the gravimetric method and the colorimetric method. The high-concentration test dust used for dust generation is also similar to the gravimetric method and colorimetric method. The 'quantity' of the dust is the size of the particles in the small particle size. Number. The instrument for measuring dust is a laser particle counter. During the test, before and after each dust generation test, count and measure, and calculate the filter efficiency of the filter for various particle sizes. When the test is terminated The test is stopped when the conditions are met. The typical efficiency value of the filter is within the specified particle size range, and the instantaneous efficiency of each stage is based on the weighted average of the amount of dust. European standards stipulate that the specific polydisperse phase droplets used in the counting measurement, such as Use the DEHS spray blown out by the Laskin nozzle, or use the Latex latex ball that is the same as the standard particles used in the calibration counter. The United States stipulates that the counting measurement uses bleach. The counting efficiency is no longer a single value, but a filtration efficiency curve along different particle diameters The European test shows that when the final resistance of the test is 450Pa, the counting efficiency value at 0.4?m is close to the efficiency value of the traditional colorimetric method. The American standard stipulates that the efficiency value of different particle size ranges is measured for different grades of filters. , The final resistance of the test is still '2 times the initial resistance or higher'. The complete counting efficiency test is a destructive test and cannot be used for daily product inspection. The dust source for the gravimetric method test is large particle size, high concentration standard dust The main component of the dust is the selected floating dust in the specified area, and then mixed with the specified amount of fine carbon black and short fiber. Most countries stipulate the use of 'road dust' in the desert zone of Arizona in the United States, and the Chinese standard once stipulated the use of the Loess Plateau. For the dust of a certain village, the Japanese standard stipulates the use of “Kanto Asian clay” originating from Japan. The measured “quantity” is the weight of the dust. The filter is installed in the standard test wind tunnel, and the dust is continuously emitted at the upper wind. Measurements are made at regular intervals. The weight of dust passing through the filter or the amount of dust collected on the filter, thereby obtaining the filter efficiency calculated by the weight of the dust at this stage. The final weighting efficiency is the weight of the efficiency of each test stage according to the amount of dust Average value. The conditions for the termination of the gravimetric test are: the agreed final resistance value, or when the efficiency is significantly reduced. The so-called 'agreement' here refers to the agreement between the customer and the tester, or the tester's own regulations. Obviously The weighting efficiency value is different when the conditions of the agreed termination test are different. When the test is terminated, the weight of the test dust contained in the filter is called the 'dust holding capacity'. The gravimetric method is used to measure low-efficiency filters, and those filters are generally used Pre-filtration in the central air-conditioning system. The gravimetric method test is a destructive test and cannot be used for the daily product performance inspection of the manufacturer. The atmospheric dust counting method dust source is the 'atmospheric dust' in the natural atmosphere. The 'quantity' of dust It is the total number of particles greater than or equal to a certain particle size. The instrument for measuring dust is an ordinary optical or laser dust particle counter. The efficiency value is the initial efficiency of the new filter. Atmospheric dust The counting method is used to measure general ventilation filters. Its efficiency value only represents the performance of the new filter. China's efficiency classification is based on the atmospheric dust counting method. The colorimetric test bench and test dust are the same as those used in the gravimetric method. The 'quantity' of dust is the amount of light passing through the high-efficiency filter paper at the sampling point. Sampling before and after the filter, there is a high-efficiency filter paper on the sampling head. Obviously, the pollution degree of the high-efficiency filter paper at the sampling point before and after the filter will be different. In the test, after a period of dust generation test, measure the light transmission of the high-efficiency filter paper before and after the filter in the non-dust state, compare the difference in the light transmission of the filter paper, and use the prescribed calculation method to obtain the so-called 'filtration efficiency'. The final colorimetric efficiency is the weighted average of the efficiency values u200bu200bof each stage of the whole test process according to the amount of dust generated. The conditions for terminating the test are similar to those for the weight method: the agreed final resistance value, or when the efficiency drops significantly. The colorimetric method is used to measure high-efficiency general ventilation filters. Most of the filters in the air-conditioning system belong to this kind of filters. The colorimetric method used to be a common test method abroad, and this method is gradually replaced by the counting method. Strict colorimetry is a destructive test. More about filter efficiency tester: http://www.standard-groups.com/FilterMaterial/
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