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Key indicators affecting air filters
Key indicators affecting air filtersThe air filter is an air filtration device, the main function is to filter the dust in the air so that the gas entering the room can be purified, generally used in clean plants, clean rooms and laboratories, and other places.At present, the air filter is the most important means of air purification, and it's good or bad can be said to determine whether indoor cleanliness is up to standard. The performance of air filters is mainly air volume, filtration efficiency, air resistance, and dust capacity, which are also the four main indicators affecting the filter. Air filters are mainly divided into primary filters, medium-efficiency filters, sub-high-efficiency filters, high-efficiency filters, and ultra-high-efficiency filters. Here is a brief introduction to the role of each of these filters. 1. The primary filter mainly filters dust particles above 5.0μm and is generally used as a pre-filter to protect the service life of the medium- and high-efficiency filters. 2. Medium efficiency filter filters dust particles above 1.0μm, generally placed before the high-efficiency filter, after the fan, to reduce the load of the high-efficiency filter and extend the service life of the high-efficiency and air conditioning box accessories. 3. Sub-high efficiency filters can filter out dust particles above 0.5μm and can be used as terminal filters in purification systems with low requirements in general. 4. High-efficiency filters are mainly used to filter out dust particles above 0.3μm, are the terminal filters in air conditioning purification systems, and must be used as terminal purification equipment in high-grade clean rooms (0.3μm clean rooms). 5. Ultra high-efficiency filter to remove dust particles greater than 0.1μm, installed at the end of the purification air conditioning ventilation system, that is, high-efficiency air supply, is a high-level clean room (0.1μm clean room) must be used in the terminal purification equipment. Four main indicators affect the air filter. Airflow, filtration efficiency, air resistance, and dust-holding capacity are the four main indicators that affect air filters. In addition to this, air flow and filter life are also very important parameters. 1. Air volume: air volume through the filter = filter cross-sectional air velocity x filter cross-sectional area (m²) x 3600m³ 2. Filtration efficiency: at the rated air volume, the percentage of the difference between the dust concentration N1 and N2 in the air before and after the filter and the dust concentration in the air before the filter is called filtration power A. It is often more intuitive to use the penetration rate to evaluate the final effect of the filter. The penetration rate K is the percentage of dust concentration in the air after the filter and before the filter. 3. Air resistance: The resistance encountered by the air flowing through the filter is an integral part of the total system resistance. The resistance increases with the increase in filter speed. The resistance of the filter must be evaluated on the premise of the rated air volume, and the resistance of the filter rises with the increase of the dust content; the resistance of the new filter when it is used is called the initial resistance, and the resistance when the dust content reaches its maximum value is called the final resistance. Generally, the final resistance of medium and high-efficiency filters is about 2 times the initial resistance. 4. Dust capacity: the amount of dust accumulated inside the filter when the final resistance is reached under the rated air volume. The main source of clean room dust is the flow of people, according to statistics, about 80% of the total ratio or more. Apart from this, it is from the building, which is probably between 10% and 15%. Overall, the dust brought in by the clean air supply system should be minimal. It is worth noting that the function of the air filter is to filter out dust particles, but it is also the main measure for germ removal. This is because dust particles often act as carriers of bacteria, and if there are more dust particles in the air, bacteria can easily attach to them, so filtering dust particles is equivalent to filtering out a large number of bacteria as well. In addition, the HEPA filter should be replaced in any of the following situations. 1. The airflow speed is reduced to a minimum, even after replacing the primary and secondary air filters, the airflow speed still cannot be increased. 2. The resistance of the high-efficiency air filter reaches 1.5 to 2 times the initial resistance. 3. The high-efficiency air filter has a leak that cannot be repaired. |
