Want to know whether the filter is qualified, we must first know that the filter test has the factory testing and on-site testing, in the two testing process, the filter is not qualified for the following reasons:
Visual and simple test can be found
Rupture or minor damage the surface of the filter. The naked eye is easy to observe the filter material is damaged, a small amount of damage repair is relatively easy, this kind of repair is best in the filter production plant. Some minor damage to the naked eye is not easy to observe, only after the test bench test can detect.
In the manufacturing process of filter filter pressure is overweight or some man-made factors will damage the filter. If only a few local damage and not serious, it may be repaired into a qualified product, but the quality of the repair to meet the requirements of the standard.
Seal defects, filter and filter frame joint leakage. Production inspection, most unqualified efficiency is this caused by air leakage. This situation most can be repaired, but the appearance of the repair can not have obvious defects.
Filter sealant joint leakage. A sealing strip is on the frame of the high efficiency filter. Sometimes, the interface processing is not good, will cause the leakage phenomenon. Some manufacturers use polyurethane foaming seal, no seams, no air leakage problem. If you use a rubber joint, the joint is the best way to make a maze.
Raw material itself
The filter media is low efficiency. If the efficiency of the filter media is not up to the requirement (definition: efficient filter detection in 5.3cm/s wind speed of 0.3 m dust filtration efficiency is larger than 99.97%), will not be able to produce qualified filters. This truth who all understand, but the market is indeed some marked is efficient, practical reach efficient filter.
Material dust. The traditional HEPA filter, if the paper partition, and strict control of raw materials, there is a risk of dust separator paper. Filter material production environment is poor, with a large number of possible dust filter itself off, make the filter may also be dust. It is worth noting that some of the test methods can not test this kind of hair.
Detection of their own problems
Factory inspection, if the use of scanning detection method, the filter out of the wind surface may have a vortex, the surrounding dust with the eddy into the scanning area. If the vortex exists, scanning dust certainly appear at this time, you will not be able to exceed the standard, determine the dust from the leak or vortex, the lack of experience of the operator may be sentenced to filter waste. Some foreign manufacturers, in order to eliminate the error caused by the eddy current, the filter test bench in the clean room. Domestic manufacturers are not so luxurious, we have to think of ways to exclude eddy.
In the summer of 2005, I met a case in Beijing. The end customer is a famous key laboratory, the laboratory requires engineering contractor to install the former test filter. The contractor made a simple scan test bench, the filter does not pass the test. After we explained, they also suspect that the vortex, they will filter out the wind surface with a long pipe cover up, the pipeline to add to the 1m long, there is still a vortex.
Filter installed, and sometimes in the field to scan the test, it is the company or the user to install their own things, but the filter manufacturers are often asked to participate. At this point, the eddy is also a headache problem, a little careless, it may also be a good judge of the filter.
In many cases, the filter is installed, people used to judge whether the filter dust concentration downstream qualified, at this time, if the upstream concentration is too high, even if the filter efficiency is qualified, may also be due to the lower concentration high and was mistaken for unqualified.
High efficiency filter sealing problem
Sometimes, the high efficiency filter and the outer structure of the contact part of the seal is not strict, resulting in leakage. This is not the quality of the filter itself, but the external structure or installation problems.
The site installation staff at the high efficiency filter, I do not like the glue, because practice shows that, once the contact part of the seal is not good, the more the glue it leaks, you may never block. Filter should be sealed by the seal structure itself, the structure is not good, should go to deal with structural defects. If the defective structure is provided by the filter plant, such as efficient filter outlet, it is also a structural problem rather than the filter element.
Efficient filter, due to the strict use of premises, the filter must be passed before the factory inspection, qualified before you can put into use.
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