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Detailed explanation of the steps for leak detection of high efficiency filters
Detailed explanation of the steps for leak detection of high efficiency filtersIn the first step, record the number of high-efficiency air filters and number them on the drawing.In the second step, ensure that the air conditioning system is operating properly and is ready for testing. The air speed and air volume must be adjusted and balanced. Use an aerosol generator to release challenging particles upstream and drive the PAO upstream of the HEPA filter. The concentration of particles is approximately 10 to 20 micrograms of PAO per liter of air. The more particles there are, the easier it is to detect leaks, but beyond 50 micrograms the difference is small and it is difficult to use less than 10. The particle concentration can be roughly calculated from the air volume and then confirmed with an aerosol photometer. Once the upstream particle concentration has been confirmed, you can scan the surface of the HEPA filter to look for leaks. If necessary, a plastic curtain can be placed over the HEPA filter to ensure the accuracy of the test. The surface of the HEPA filter is scanned, either from the outside to the inside or along the long/short side to detect the scan path. The test scanning method is as follows: 1. Each HEPA filter and its frame needs to be tested. 2. When using the surface of the HEPA filter, the leak detector should be correctly placed and moved forward in the direction of the short side to cover the entire HEPA filter. 3. When scanning the frame of the HEPA filter, especially between the HEPA filter and the ceiling grille, the leak detector should cover all joints. 4. Use a particle counter with a square cone (10mm * 60mm) sampler placed approximately 25mm below the HEPA filter and move the instrument at a speed of 50 mm/sec. 5. The readings on the aerosol photometer are upstream and downstream percentage values, so if the value is greater than 0.01 then a leak may be suspected and the test can be repeated by returning it to approximately 100mm. If there is no continuous high reading then the test can be continued, otherwise, it means that a leak will need to be recorded and repaired or replaced in the future. |
