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High-efficiency leak detection operation steps
High-efficiency leak detection operation stepsHigh-efficiency filter leak detection methodHigh-efficiency filter leak detection usually uses a PAO generator to generate dust upstream of the filter. It uses a photometer to detect the aerosol concentration upstream and downstream of the filter to determine whether the filter leaks. PAO generators can be divided into hot generation and cold generation. The hot generator uses the principle of evaporation and condensation. The atomized aerosol particles are evaporated by a heater and condensed into tiny droplets under specific conditions. After removing the oversized and undersized droplets, a mist-like DOP of about 0.3μm is left to enter the air duct, and the particle size distribution is 0.1~0.3μm. Cold generator refers to using compressed air to bubble in the liquid, and the splashing through the laskin nozzle produces a physical multi-dispersed phase DOP aerosol, with a maximum distribution particle size of about 0.65μm. Use cold DOP when scanning the filter for leak detection. High-efficiency leak detection operation steps To determine whether there is obvious leakage in the high-efficiency filter itself and its installation, the following places must be tested on site: the filter material of the filter; the connection between the filter material and the inside of its frame; between the gasket of the filter frame and the filter group support frame; between the support frame and the wall or ceiling. 1. Introduce PAO aerosol on the upstream side of the HEPA to be tested For HEPA in the HVAC system, to make the concentration of aerosol uniform when it reaches the HEPA, the aerosol can be introduced directly from the negative pressure side of the system fan. If it is to be introduced from the air duct, it should be introduced at least 10 times the diameter of the air duct from the HEPA, and the turning should be minimized (IEST American Institute of Environmental Science and Technology). In general, it is sufficient to keep the upstream aerosol at the required concentration and the concentration fluctuation within a certain range. For HEPA on laminar flow hoods and clean benches, the aerosol is introduced directly from the negative pressure side of the system fan. 2. Initialize the aerosol photometer and set the reference standard value Initialize and set the alarm value according to the operating requirements of the aerosol photometer. Connect the sampling tube to the upstream sampling port and measure the concentration of upstream aerosol. Adjust the generated aerosol concentration according to the operating requirements of the aerosol generator so that the upstream aerosol concentration reaches 20~80μg/L. 3. Scanning for leak detection Remove the HEPA diffuser and scan the entire filter surface, the seal between the filter and the frame, between the frame and the frame, and between the frame and the static pressure box. During the scan, the sampling head is about 2.54cm from the filter surface, and the scanning speed does not exceed 5cm/s. The scan is carried out back and forth in a straight line, and the lines should overlap. During the test, if there is an alarm (that is, the leakage rate exceeds 0.01%), it indicates a leak. The leak is plugged with silicone or tightened before scanning and inspection. It takes about 5~10 minutes to check a filter. During the test, the concentration of upstream aerosol should be confirmed frequently. Note that a protective mask and protective goggles should be worn during the test. 4. Result determination and processing The leakage rate of the high-efficiency filter should be less than or equal to 0.01%. If the leakage rate of all points of the HEPA during the test does not exceed 0.01%, the HEPA is judged to be qualified. If one point exceeds 0.01%, it is judged to be unqualified and the point is marked and needs to be repaired or replaced. The leakage of the high-efficiency filter material can be repaired with special glue, but the area of a single leakage point cannot be greater than 1% of the total area, and the area of all leakage points cannot be greater than 5% of the total area, otherwise, it must be replaced. Warm Tips High-efficiency filter leak detection cycle FDA recommends that the sterile preparation production workshop be leaked once every six months in the sterile drug production guide, and my country recommends that it is usually once a year in the GMP inspection guide. ISO 14644-3:2005 recommends a maximum time interval of 24 months for leak detection of installed HEPA. DOP leak detection should be performed after the HEPA is installed or replaced. When environmental monitoring shows that the air quality has deteriorated, or when the product sterility test fails or the culture medium simulation filling test fails, leak detection can be performed as part of the deviation investigation. Filters that need to be leak tested also include HEPA used in drying tunnels and dry ovens. |
