The leak detection after installation of the high-efficiency air filter is to confirm the installation quality, to detect the entire surface of the high-efficiency air filter air supply port, the periphery of the filter, and the seal between the filter outer frame and the mounting frame. For leak detection, the test aerosol is introduced from the upwind side of the filter and immediately scanned on its leeward side. This test is generally carried out in the "empty state" or "static" of the clean room (area).
The leak detection methods after installation of the high efficiency air filter include a photometer method and a particle counter method. The photometer method is generally used in a clean room with a small air treatment system or a piping system equipped with an aerosol injection point to achieve a specified high concentration test aerosol; due to the sensitivity of the particle counter method and less pollution, generally The particle counter method is used for leak detection after installation of the high efficiency air filter.
When the scanning leak detection is performed by the photometer method, the transmittance of the highest penetration particle diameter of the filter to be tested is equal to or greater than 0.005%. The test aerosol used should not affect the product or process facility within the clean room (area).
Before the photometric leak detection, the tested filter should run between 80% and 120% of the rated wind speed and confirm the uniformity of the air supply.
The concentration of aerosol introduced into the upwind of the tested filter should be from 10 mg/m3 to 100 mg/m3. When the concentration is lower than 20 mg/m3, the sensitivity of the leak detection will be reduced. When the concentration is higher than 80 mg/m3, if the test is long, the filter will be fouled. The concentration and uniformity of the aerosol should be confirmed before the filter is leak tested.
For leak detection scanning, if a 3cm×3cm square probe is used, the scanning speed shall not exceed 5cm/s, and the maximum area scanning rate of the rectangular probe shall not exceed 15Cm2/s. During the scan, if a leak equal to or greater than the limit is displayed, the probe should be left at the leak. The leak limit for a high-efficiency air filter is a leak that exceeds the upwind test aerosol concentration 10-4 or is determined by negotiation with the owner.
When the particle counter method is used for scanning leak detection, the penetration rate of the highest penetration particle diameter of the tested air filter is greater than or equal to 0.00005%. Test aerosols that may deposit volatile oil dust on filters or pipes are not permitted.
Before the particle counter is leak tested, the tested filter should be operated between 70% and 130% of the rated wind speed and the uniformity of the air supply is confirmed.
The upwind side of the tested filter should be introduced with a uniform concentration of atmospheric dust or with additional aerosol-containing air to achieve the desired test aerosol concentration. When the particles are larger than or equal to 0.5 μm, the concentration of the test aerosol should be 3.5×105 C/m 3 or more; for particles larger than or equal to 0.1 μm, the concentration should be 3.5×109 PC/m 3 or more.
For leak detection scanning, the sampling port should be less than 5.0cm away from the measured part and move at a speed of 0.05m/s. The transmittance of the leak concentration converted from the downwind test of the air high efficiency filter shall not exceed 3 times the qualified transmission rate of the filter.
The leak detection of a high-efficiency air filter installed in a pipe or an air handler can be performed by a photometer method or a particle counter method. Leak detection of high efficiency air filters with a penetration rate of more than 0.005% for the most easily penetrated particle size installed in a pipe or air handler.
When leak detection, the tested filter runs between 70% and 130% of the design wind speed and confirms the uniformity of air supply. The concentration of atmospheric dust or aerosol introduced in the upwind direction should be sufficient to obtain statistically significant readings in the downwind test.
During the test, the sampling port should be 30cm to 100cm away from the measured part, and 2.5cm away from the pipe wall in the pipeline, and the measured dust concentration should be recorded.
The limit of leak detection for high-efficiency air filters shall not exceed 10-4 (0.01%) when using the photometer method, and shall not exceed 3 times the qualified transmission rate of the factory when using the particle counter method.
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