How to judge whether the high efficiency filter is qualified?

The high-efficiency filter is mainly used to capture particulate dust and various suspended solids below 0.5um, as the end filter of various filtration systems. The ultra-fine glass fiber paper is used as the filter material, and the plastic paper, aluminum foil board and other materials are folded as the dividing plate, sealed with a new type of polyurethane sealant, and the outer frame is made of galvanized sheet, stainless steel sheet and aluminum alloy profile. High-efficiency air filters can be widely used in the air-conditioning end air supply of clean rooms in optical electronics, biomedicine, precision instruments, beverages and food industries. Therefore, the filter must be tested one by one before leaving the factory, and it can be put into use only after it is qualified.

So, how should we judge whether the high efficiency filter is qualified?

1. Check the raw materials

1) The efficiency of the filter material itself is low. If the efficiency of the filter material itself does not meet the requirements (definition of high-efficiency filter material: detected at a wind speed of 5.3cm/s, the filtration efficiency of 0.3μm dust is ≥99.97%), it is impossible to manufacture a qualified filter.

2) The material is dusty. The traditional high-efficiency filter with partitions, if the partitions are made of paper, and the raw materials are not strictly controlled, the paper partitions have the risk of dust generation. The production environment of the filter material 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 this type of dust emission.

2. Visual estimation

1) The surface of the filter material is cracked or slightly damaged. It is easy to observe the damage of the filter material with the naked eye, and it is easier to repair a small amount of damage. This repair should be carried out in the filter manufacturer. Some minor damages are not easy to observe with the naked eye, and can only be detected by testing on the test bench.

2) During the production process of the filter, the filter material is too heavy or some human factors will damage the filter material. If only a few places are damaged and not serious, it may be repaired into a qualified product, but the repair quality should meet the standard requirements.

3) Sealing defects, air leakage at the joint between the filter material and the filter frame. In the production inspection, most of the unqualified efficiency is caused by this kind of air leakage. Most of these cases can be repaired, but the appearance after repair should not have obvious defects.

4) Air leakage at the seam of the filter sealant strip. Many HEPA filters have sealant strips on the frame. Sometimes the interface is not handled well, which will cause air leakage. Some manufacturers use in-situ foamed polyurethane sealing strips, which have no seams and no air leakage problems. If a strip with joints is used, the joints should be made into a labyrinth.

3. Simple test

In many cases, after the filter is installed, the downstream dust concentration can be used to judge whether the filter is qualified or not.