How to detect leaks in filters - Clean Room Engineering

Filter leak detection I believe that many companies will have questions about how to detect leaks in filters. Guangdong Saite purification generally adopts the following methods. According to the 'Clean Room Construction and Acceptance Specifications', the leak detection of the high-efficiency filter can have the following methods: 1. The leak detector method to scan the leaked filter must have measured the air volume, which is between 80% and 120% of the designed air volume. conduct. When there are multiple filters on the same air supply surface, the method of exposing only one filter at a time should be used for measurement if the structure allows. When several or all filters must be exposed to aerosol at the same time, in order to uniformly mix all filters, it is advisable to introduce aerosol for leak detection at the suction end of the fan or the branch pipe in front of these filters, and immediately check the The concentration on the windward side is measured directly in front of the filter. 2. Leak detection by particle counter method The air volume of the leak-detected filter must have been measured, and the air volume should be between 80% and 120% of the design air volume. The instrument is a light-scattering particle counter with a sampling volume of 1-3L/min that can measure 0.5 microns. For leak detection, bulk particle counters are not suitable. Now it should be explained that it is not easy, unnecessary, and even less intuitive to use the DOP method for leak detection on site, because it reflects the relative value of the concentration rather than the amount of particles. In addition, DOP brings pollution to the filter, whether it has carcinogenic effect is still a question. It turns out that both leak detection methods require a certain upstream concentration, which is based on the minimum scale of the instrument, the efficiency of the high-efficiency filter is defined as 99.97%, and the minimum reading of the particle counter is 1 particle. However, the latest research and measurement practice show that the upstream concentration is not necessary to be so large, and it should be enough to bring danger to the work area, and it does not matter if it cannot be measured. According to experiments, the upstream concentration of the high-efficiency filter may be about 3000 grains/L. The calculation shows that for a leak as small as 0.2mm, at a distance of 25mm from the filter surface (this is the common requirement of relevant standards at home and abroad), when sampling at a flow rate of 2.83L/min, a concentration of about 25 grains/L will be obtained. , which is completely measurable. 3. The construction acceptance specification stipulates that the number of particles detected by the particle counter during leak detection is not greater than 3 times or 2 times the theoretical number of particles that can pass through (the latter is for ultra-high efficiency filters). The basis for this is the calculations presented by the authors. However, according to the latest research above, for an ordinary 0.5-micron high-efficiency filter with class 100 as the highest object, if the number of particles measured at a distance of 25mm from the filter surface does not exceed 3 particles/L, it will not bring the work area. The danger of exceeding the standard, so this can be used as a leak detection standard for ordinary high-efficiency filters. 4. For the 100-level sites, there must be a comprehensive leak inspection report of high-efficiency filters on the site before installation (it is allowed to include the qualified report after repair), and there must also be a frame-by-frame scanning qualification report after installation (it is allowed to include after repair. compliance report). For places lower than 100 grades, there must be a qualified report for frame scanning and sampling inspection of high-efficiency filters after installation (including repair and plugging) (no less than one tuyere for each room, and when there are many tuyere, the sampling ratio should not be less than 20 %) Guangdong Saite Purification has many years of experience in the decoration and transformation of clean workshops, as well as supporting filtration pharma machinery and cleaning equipment. If necessary, please call to discuss.

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