Due to the strict requirements of the high-efficiency filter, the filter must be tested one by one before leaving the factory. The filter test has factory inspection and on-site inspection. During these two tests, the filter may not meet the standard. The reasons may be as follows.
First, the reasons for visual inspection and simple test can be found
Visual inspection:
(1) The surface of the filter material is broken or slightly damaged. It is easy for the naked eye to observe the damage of the filter material, and it is easier to repair a small amount of damage. This repair is best carried out at the filter manufacturer. Some minor damage is not easy to observe with the naked eye, and can only be detected after testing by the test bench.
(2) The filter material is too heavy or some human factors may damage the filter material during the production process. If it is only damaged and not serious in some places, it may be repaired into a qualified product, but the quality of the repair should meet the standard requirements.
(3) Sealing defects, air leakage from the filter material and the outer frame of the filter. In production inspection, most of the inefficiencies are caused by such air leakage. Most of this can be fixed, but the appearance after repair cannot be obviously flawed.
(4) Air leakage at the seam of the filter sealant strip. Many high efficiency filters have a strip of seal on the bezel. Sometimes the interface is not handled well, which will cause air leakage. Some manufacturers use on-site foamed polyurethane sealing strips, without seams, there is no air leakage problem. If a strip with a joint is used, the joint is preferably in the form of a labyrinth.
Second, the raw material itself
(1) The filter material itself is inefficient. If the efficiency of the filter material itself is not met (the definition of high-efficiency filter material: detection at 5.3cm/s wind speed, 0.3μm dust filtration efficiency ≥99.97%), it is impossible to manufacture a qualified filter.
(2) The material is dusty. Traditionally, there is a separator high-efficiency filter. If it is a paper separator, and the material control is not strict, the paper separator has the risk of dusting. The filter material production environment is poor, the filter material itself has a large amount of dust that may fall off, and the filter made may also generate dust. It is worth noting that some inspection methods cannot detect such dusting.
Third, the detection of its own problems
(1) When the factory detects, if the scanning detection method is used, there may be eddy currents on the air outlet surface of the filter, and the surrounding dust enters the scanning area along with the eddy current. If eddy currents exist, there must be dust exceeding the standard when scanning. At this time, you cannot judge whether the dust is from the filter leak or eddy current. The inexperienced operator may judge the good filter as waste. In order to eliminate the misjudgment caused by eddy currents, some foreign manufacturers put the filter inspection station in the clean room. Domestic manufacturers are not so extravagant, we have to find ways to eliminate eddy currents.
(2) In many cases, after the filter is installed, people use the downstream dust concentration to judge whether the filter is qualified. Even if the filter efficiency is qualified, it may be misjudged as unqualified due to the high downstream concentration.
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