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PAO-DOP high efficiency filter leak detection method process
PAO-DOP high efficiency filter leak detection method processThe filtration efficiency of the liquid tank-type high-efficiency filter itself is generally tested by the manufacturer and is accompanied by a filter filtration efficiency report sheet and a certificate of conformity when it leaves the factory.For users, the leak detection of liquid tank-type high-efficiency filters refers to the on-site leak detection after the installation of high-efficiency filters, which is mainly to check the small pinholes and other damages in the filter material, such as the frame seal, gasket seal, and the leakage seam on the filter frame. The purpose of leak detection is to check the sealing of the high-efficiency filter and its connection parts with the installation frame, to discover the defects in the high-efficiency filter itself and in the installation in time, and to take corresponding remedial measures to ensure the cleanliness of the area. The method of leak detection of the HEPA filter. The DOP liquid tank type high-efficiency air supply is itself a liquid tank type high-efficiency filter, the leak test of this high-efficiency filter is basically to apply the challenge particles upstream of the high-efficiency air filter, and then use the particle detection instrument to search for leaks on the surface and frame of the high-efficiency air filter. There are several different ways to test for leaks and they are suitable for different applications. HEPA filters are tested by 1. gas-gel photometric testing 2. Particle counter test 3. Full efficiency test 4. External gas test method The details are described below. PAO or DOP leak detection is an aerosol photometer test method Aerosol photometry: The aerosol photometer method was the earliest form of testing but is still used today because it is so effective. The Aerosol Photometer is a type of particle counter that also uses laser technology, but after scanning the air sample for particles, it gives the overall intensity of the particles, not the number of particles. used to simulate clean room particles and is therefore used as a verification particle. Leakage is defined as leakage out of the upstream concentration by parts per million, and because the gas-gel photometer can directly display the ratio of upstream and downstream particle concentrations, it is very easy to scan HEPA filters. Because of its accuracy and reliability, the US Food and Drug Administration (FDA) has mandated the use of DOPs and aerogel photometers for all HEPA filter leak tests within its jurisdiction (food processing and medical-pharmaceutical sites). For some time now, due to suspected carcinogenic effects on humans, DOS (Dioctylsebaeate sebacate), also known as DEHS [di(2-ethyl hexyl)sebacate] and PAO or DOP (polyaphaolefin) has often been used instead, but the test method is still called "DOP method". Atmospheric dust is not generally used for leak detection as its concentration varies with location and time etc. Sometimes it is larger and sometimes it is lower. the FDA states that when conducting leak detection, the aerosol chosen should meet certain physicochemical requirements and should not use aerosols that will cause microbial contamination and result in microbial breeding. The DOP generator can be divided into hot and cold generators, the hot generator uses the principle of evaporation and condensation, and the atomized aerosol particles evaporated with a heater, and condensed into tiny droplets under specific conditions, to remove too large and too small droplets, leaving about 0.3um of fog DOP into the duct, particle size distribution in 0.1 ~ 0.3um. the cold generator is the use of compressed air in the liquid drum bubble, through the Laskin nozzle splash to produce the material state of the polydisperse phase DOP aerosol, the maximum distribution of particle size in the 0.65um or so. Currently, more hot DOP is commonly used, so the efficiency of the filter should be guaranteed. PAO-DOP high-efficiency filter leak detection test apparatus: The instruments used are an Aerosol Photometer and an Aerosol Generator. The Aerosol Photometer has both analog and digital display versions and must be calibrated once a year. There are two types of Aerosol Generators, the normal Aerosol Generator, which requires only high-pressure air, and the heated Aerosol Generator, which requires high-pressure air and a power supply. Leak testing procedure for PAO-DOP high-efficiency filters. 1. Record the number of HEPA filters on the drawing and number them. 2. Make sure that the air conditioning system is operational and ready for testing and that the air speed and air volume have been adjusted and balanced. 3. Apply challenge particles upstream using an air-gel generator to inject PAO or DOP upstream of the HEPA filter at a concentration of approximately 10 to 20 micrograms of PAO or DOP per liter of air. The more particles there are the easier it is to identify leaks, but above 50 micrograms there is little difference and below 10 it is difficult to use. Particle concentrations can be roughly calculated using air volume and then confirmed using an air-gel photometer. 4. Once the upstream particle concentration has been confirmed, the surface of the HEPA filter can be scanned for leaks, if necessary the HEPA filter can be covered with a plastic curtain to ensure accurate testing. 5. The surface of the HEPA filter is scanned, either from the outside in or along the long/short side in a circuitous manner as follows a. Each HEPA filter and its frame are tested. b. For the surface of the HEPA filter, position the leak detector as shown in Figure (b) and proceed in the direction of the short side, covering the entire HEPA filter. c. When scanning the frame of the HEPA filter, especially where the HEPA filter is sealed to the FFU, the leak detector can be positioned as shown in (a) or (b) above, covering the entire joint. d. A square cone (10mm*60mm) sampler with a particle counter is placed approximately 25mm below the HEPA filter and moved at a speed of 50mm/sec. e. The reading on the air gel photometer is the upstream and downstream percentage value, so if the value is greater than 0.01, you can suspect a leak and can return about 100mm and measure again repeatedly, if there is no continuous high reading, then you can continue to test, otherwise it means there is a leak and needs to be recorded and repaired or replaced later. 6. If the high-efficiency air filter is damaged, it should be repaired or renewed and then tested again. 7. If there is any leakage in the frame, it should be re-installed and adjusted until there is no leakage. 8. Records must be kept of the results of the scan, the condition of the leak, and how it was treated. Note: For HEPA filters in HVAC systems, to achieve a uniform concentration of aerosols when they reach the HEPA, aerosols can be introduced directly from the negative pressure side of the system fan or, if introduced through the duct, at least 10 times the diameter of the duct from the HEPA, with minimal cornering (American Society for Environmental Science and Technology). In general, it is sufficient to keep the upstream aerosol at the required concentration and to keep the concentration fluctuating within a certain range. For HEPA on laminar flow hoods and ultraclean tables, aerosols are introduced directly from the negative pressure side of the system fan. PAO-DOP high-efficiency filter leak detection and acceptance criteria 1. Any continuity reading of more than 0.01% is considered as leakage, each HEPA filter must not have leakage after testing and repair, nor must the frame have leakage. 2. The repair area of each HEPA filter shall not be greater than 3% of the HEPA filter area. 3. The length of any repair shall not be greater than 38mm. HEPA filter leak detection intervals Leak testing is recommended by the FDA in its guidelines for the manufacture of sterile pharmaceuticals every six months for aseptic manufacturing plants and by China in its GMP inspection guidelines, usually once a year. Leak detection can be carried out as part of a deviation investigation when environmental monitoring shows deterioration in air quality, when a product fails a sterility test, or when a simulated filling test of the culture media fails. Filters subject to leak testing also include the HEPA used in drying tunnels and dry ovens. |
