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Why do high-efficiency filters need to be leak-checked?
Why do high-efficiency filters need to be leak-checked?In purification projects, sometimes it is found that the leak in the gap between the high-efficiency filter and the high-efficiency air outlet box exceeds the standard, but the reason has not been found. So what is the appropriate value of the surface wind speed of the high-efficiency filter when leaking? After the high-efficiency filter is installed, the particles of the installed high-efficiency filter leak very badly. What are the reasons?The use of air volume of the high-efficiency filter The rated air volume of the high-efficiency filter refers to the airflow rate when the filter is under the specified pressure difference. It involves factors such as the filtration efficiency, material, and structure of the filter itself. When using a high-efficiency filter, it is necessary to ensure that its rated air volume is not lower than the air volume under the use conditions, otherwise, it will seriously affect the filtering effect and even make the filter unable to work normally. Under all normal circumstances, it is generally reasonable to take 80% of the rated air volume as the use air volume. For example, if the rated air volume of the equipment is 1000, it is more economical and reasonable to set the use air volume of no more than 800. When the filter is leak-checked, the effect may be better when the wind speed is low. If the filter is deemed intact during the leak detection process, but the side seam test fails, there are two main reasons. One is the quality of the box, which makes it difficult to seal during installation. The other reason is the impact of the environment, which can be identified by doing enclosure detection on the air outlet. The filtration efficiency of a high-efficiency filter refers to the ability of the filter to remove particulate matter in the air within a certain period. It usually refers to the ratio of the weight or number of particles captured by the filter to the weight or number of particles contained in the air before filtration, expressed as a percentage. Filtration efficiency = dust captured by the filter/dust content in the upstream air = 1 dust content in the downstream air/dust content in the upstream air. Among the factors determining filtration efficiency, the meaning of dust "amount" varies, and the filter efficiency values calculated and measured are also different. In practice, there are the total weight of dust and the number of dust particles; sometimes it is the amount of dust of a typical particle size, it is the amount of all dust; there is also the light flux (colorimetry) and fluorescence (fluorescence method) that indirectly reflect the concentration by specific methods; there is the instantaneous amount of a certain state, and there is also the weighted average amount of the efficiency value of the whole dust generation process. If different methods are used to test the same high-efficiency filter, the measured efficiency values will differ. The surface velocity and filtration rate of the high-efficiency filter are important parameters reflecting its ability to pass air volume. Surface velocity refers to the airflow velocity on the cross-section of the high-efficiency filter, usually expressed in m/s. The calculation formula is V=Q/F∗3600, where V represents the surface velocity, Q represents the airflow through the filter, and F represents the cross-sectional area of the filter. Filtration rate refers to the speed of the airflow through the filter area, usually expressed in L/cm2.min or cm/s. The filtration rate reflects the passing capacity of the filter material, that is, the filtering performance of the filter material. When the filtration rate is low, generally speaking, a higher filtration efficiency can be obtained. When the filtration rate allowed to pass is low, the resistance of the filter material is large. |
