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ISO 14644-1 Cleanroom Air Purification Technology

Popularity:10 Release time:2022-07-23 09:18:01

The study of ISO 14644-1 clean room air filtration theory began in the 20th century. In 1936, Kaufmann first applied the concepts of Brownian motion and inertial precipitation to the fiber filtration theory, and deduced the mathematical formula for filtration. Subsequently, Langmuir and Davies developed the filtration theory, and finally formed a classic theory mainly based on the "single fiber model". ISO 14644-1 clean room believes that the filtration efficiency is determined by three mechanisms: inertial effect, retention effect and diffusion effect. The trapping of particles is a combination of multiple effects.

Modern filtration theory proves the correctness of inertial precipitation and the existence of particles with maximum penetrating force. It is believed that filtration efficiency is a collection of retention efficiency, Brownian diffusion effect, major effect, precipitation effect and pressure effect. In 1992, Payet et al. considered the sliding of gas on a single fiber, and introduced a correction coefficient to the classical theory to make the theory and experimental data better match. In 1995, Rosnert proposed that the particles dispersed on the surface of a single fiber are characterized by an irregular distribution and often form a dendritic structure, and established the latest improved theory and the spatial distribution of particles on a single fiber. In 2001, ISO 14644-1 clean room and others conducted theoretical and experimental research on air filtration in the case of filter blockage, and proposed a calculation model for filter efficiency and pressure loss in the presence of filter cake.

ISO 14644-1 cleanroom capture efficiency and pressure loss are the two most important indicators for evaluating filtration effectiveness. Therefore, in the research process of filtration theory, it is necessary to express both pressure loss and filtration efficiency as a function of particle characteristics, dispersion medium and filter parameters, study the relationship between pressure loss and filtration efficiency and other parameters, and strive to improve filter filtration efficiency And reducing filter pressure loss is the core task of filtration theory and experimental research.

IISO 14644-1 Cleanroom Fiber Filtration Materials

While controlling the particle size of dust in the air, attention should also be paid to the air flow. Therefore, the selection of filter materials is based on the ability to effectively intercept dust particles without causing excessive resistance to the airflow. The commonly used filter materials are various non-woven fabrics (non-woven fabrics). The fibers of the ISO 14644-1 clean room form numerous barriers to dust, and the wide space between the fibers allows the airflow to pass smoothly. In order to achieve good filtration efficiency, the number of fibers in the filter medium should be as large as possible; in order to reduce airflow resistance, the fibers should be as thin as possible. In addition, the fibrous media used as filter materials should be safe, not easy to age, and low in cost. Currently widely used materials are glass fiber, polypropylene fiber, polyester fiber, plant fiber and so on. The experimental study also shows that the filtration performance of the fiber material is closely related to its production process, and the charged fiber filter material has the characteristics of low resistance and high filtration efficiency. The filtration efficiency of the uncharged fiber filter material is relatively low, and the filtration efficiency of the melt-blown filter material is relatively high, but the resistance of the filter material is also relatively large, especially when the filtration wind speed increases, the resistance increases significantly.

Generally, ISO 14644-1 clean room air conditioning system needs to be equipped with 3 fiber filters, namely coarse-efficiency, medium-efficiency and high-efficiency filters. Coarse-efficiency filters are mostly made of glass fiber, PP, PET, wire mesh and other materials, which can filter out dust above 5 μm; medium-efficiency filters are similar to coarse-effect filters except for wire mesh, but their fiber diameter is smaller. , can remove dust particles above 1μm; high efficiency filter (HEPA) is mainly made of ultra-fine glass fiber and PP material.

The basic process of ISO 14644-1 air purification

The air purification process of the clean space of pharmaceutical production is shown in Figure 1. That is to say, the clean air from the air supply pipeline system after purification is sent to the clean room by the air supply port (with high-efficiency filter), and the dust and bacteria generated in the room are diluted by the clean air and forced to enter the return air pipe system from the return air port. In the mixing section of the air-conditioning unit, it is mixed with the fresh air that has been initially filtered from the outside, and then sent to the clean room after being filtered at the primary, middle and high efficiency levels of the air-conditioning unit and the high-efficiency air outlet. After such repeated circulation of ISO 14644-1 clean room air, pollution can be controlled at a stable level for a considerable period of time and a suitable cleanliness level can be maintained. In the process of clean space purification design and implementation, it is also necessary to consider the influence of factors such as indoor airflow direction, ventilation times and airflow speed.

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