There is a ring of sealing gasket with good elasticity on the frame of HEPA filter, which closely fits with the high-efficiency air supply outlet. In the process of use, some maintenance and construction personnel will stand on the air outlet. If they are not careful, or the structural strength of the high-efficiency air supply outlet is poor, the air outlet may be deformed, and there will be gaps between the filter and the sealing structure.
The air not filtered by HEPA filter enters the cleanroom from the gap, which will affect the cleanliness. This phenomenon should not be detected in a short time. We thought it was the problem of HEPA filter, but after a long time, dust stacked around the gap. When it is found that the cleanliness exceeds the standard, we will first open the flow equalizing orifice at the air supply outlet, and use test instrument to check whether there is air leakage. In addition, the gaskets on some HEPA filters are of good elasticity and continuous semi circular section without joints, which are in line contact with the filter mounting face, while the gaskets on other HEPA filters are four flat gaskets, which are in face contact. Line contact sealing is better than surface contact.
When the pre-filters and fine filters in the air conditioning box operate without gaskets, it is difficult to detect even if there is air leakage around them. If there is too much air leakage, the differential pressure resistance may increase abnormally, but the HEPA filter at the end of the clean room protected by these pre-filters cannot be effectively protected, and the service life will be shortened.
Sometimes, the efficiency of the pre-filter is not low, but the life of the protected HEPA filter is still short. The problem often lies in the sealing of the pre-filter in the air conditioning box. Although it is not as strict as the HEPA filter, it must be sealed. The air conditioning box shall provide a reliable sealing structure for the filter. There should be a sealing gasket with good performance and a convenient and reliable clamping mechanism. If there is no clamping mechanism or those mechanisms are not in normal use, air return may blow down the filter when the air conditioner is shut down, and the filter is not in place, which means there is no filtering section. On site, sealing and clamping faults of pre-filter often occur, affect by equipment problems, filter problems or operation problems.
