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Discussion on the reasons why high-efficiency filters fail to meet the standards
Discussion on the reasons why high-efficiency filters fail to meet the standardsThe main function of high-efficiency filters is to capture particulate dust and various suspended solids and serve as the end treatment of various filter ends, that is, the last link in the filtration. Due to the strict requirements of the use site, high-efficiency filters must be tested one by one before leaving the factory, and can only be put into use after passing the test. The filter test includes a factory test and an on-site test. During these two test processes, the reasons why the filter does not meet the standards may be as follows:I. Reasons that can be found by visual inspection and simple tests Visual inspection: (1) The surface of the filter material is broken or slightly damaged. It is easy to observe the damage to the filter material with the naked eye, and it is relatively easy to repair a small amount of damage. This repair is carried out by the filter manufacturer. Some minor damage is not easy to observe with the naked eye and can only be found through testing on the test bench. (2) During the production process, the filter material is overloaded or some human factors may damage the filter material. If only a few places are damaged and not serious, it is possible to repair it into a qualified product, but the quality of the repair must meet the standard requirements. (3) Sealing defects, and air leakage at the junction of the filter material and the filter frame. In production inspection, most efficiency failures are caused by this kind of air leakage. Most of these situations can be repaired, but the appearance after repair should not have obvious defects. Air leaks at the joints of the filter sealant strips. Many high-efficiency filters have sealant strips on the frame. Sometimes, poor interface processing will cause air leakage. Some manufacturers use on-site foamed polyurethane sealant strips, which have no seams and no air leakage problems. If a sealant strip with a joint is used, the joint should be made into a maze shape. 2. Reasons from the raw materials themselves (1) The filter material itself is inefficient. If the efficiency of the filter material itself does not meet the requirements (the definition of high-efficiency filter material: the filtration efficiency of 0.3μm dust is ≥99.97% when tested at a wind speed of 5.3cm/s), it is impossible to manufacture a qualified filter. (2) Dust generation from the material. For traditional high-efficiency filters with partitions, if the partitions are made of paper and the raw materials are not strictly controlled, there is a risk of dust generation from the paper partitions. If the filter material production environment is poor, the filter material itself carries a large amount of dust that may fall off, and the filter produced may also generate dust. It is worth noting that some inspection methods cannot detect this type of dust generation. 3. Problems with the test itself (1) During factory inspection, if the scanning test method is used, there may be eddies on the air outlet of the filter, and the surrounding dust will enter the scanning area with the eddies. If eddies exist, dust will exceed the standard during scanning. At this time, it is impossible to determine whether the dust comes from the filter leak or the eddies. Inexperienced operators may judge a good filter as waste. Some foreign manufacturers place the filter inspection table in a clean room to eliminate misjudgment caused by eddies. Domestic manufacturers are not so extravagant and have to find ways to eliminate eddies. (2) In many cases, after the filter is installed, people use the downstream dust concentration to judge whether the filter is qualified. At this time, even if the filter efficiency is qualified, it may be misjudged as unqualified due to the high downstream concentration. |
