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Leak detection method and standard for high-efficiency filters
Leak detection method and standard for high-efficiency filtersHigh-efficiency filters are highly efficient air and liquid purification equipment, widely used in various places that require a highly clean environment, such as clean rooms, biopharmaceuticals, laboratories, etc., to ensure the purity and quality of air and liquid.High-efficiency filter leak detection is a key step to ensure air circulation efficiency in clean room facilities. The main purpose is to verify whether the filter has bypass leakage or defects, such as small holes on the filter media and sealing frame, other damage, and frame leakage, etc., to ensure that the terminal high-efficiency filter is well installed. High-efficiency filter leak detection method 1) DOP method The DOP method heats the DOP liquid into vapor, and the vapor condenses into tiny droplets under specific conditions to form monodisperse aerosol particles. The filtration efficiency of the filter is calculated by measuring the turbidity ratio of the gas sample before and after the filter with a light scattering photometer. 2) Particle counting method The particle counting method uses a particle counter as a detection instrument to generate polydisperse aerosols through the spray method (cold generation). Compared with thermally generated DOP particles, they have the same material but different dispersion and detection methods. 3) Most Penetrating Particle Size (MPPS) Method This is a mainstream test method for high-efficiency filters in the world. By scanning and testing the entire air outlet surface of the filter with a large-flow laser particle counter or a condensation nucleus counter, the average efficiency of the filter can be measured, and the local efficiency of each point can be compared (leakage test). 4) Sodium flame method The sodium flame method uses a sodium chloride aqueous solution to spray and dry to form a sodium chloride aerosol with a mass median diameter of about 0.4μm as the test dust. The dust-containing air is sampled before and after the filter and introduced into a sodium flame photometer. The photocurrent value related to the dust concentration is measured to calculate the transmittance of the filter material. 5) Counting scanning method The counting scanning method uses a large-flow laser particle counter or a condensation nucleus counter to scan and test the entire air outlet surface of the filter. It can not only measure the average efficiency of the filter but also compare the local efficiency of each point (leakage test). 6) Leakage observation method The leakage observation method is to seal one end and connect the other end to a vacuum pump, fully inhale and cover the suction pipe mouth, and observe the light leakage to determine the location of the leak. 7) Bubble method The bubble method identifies the bubbles that may appear on the filter under the action of pressurized gas. 8) Smoke method The smoke method introduces low-flow smoke into the filter inlet and determines the leak location by observing the diffusion of the smoke. |
