Design principle of HEPA filter and ULPA filter

10/08/2020

    We often use HEPA filters, but what is the principle of why the HEPA filters adopt this shape? Today, the editor will introduce the design history of the HEPA filter.

    The high-efficiency filter is the last barrier of the air purification room. The design must consider the surrounding environment, purification efficiency requirements, physical space constraints, structural requirements, system volume flow requirements, system operating pressure, existing air treatment equipment, and its Function, as well as maintenance, ergonomics, cost, and manufacturing. Most HEPA filters are constructed with a pleated paper fan arranged randomly between special glass fiber sheets and corrugated aluminum partitions, like a "V" pattern pleated pad. This is connected to a sturdy base and forms the core of the filter.

    HEPA and ULPA filters are usually made of filter paper. HEPA filters can be made into HEPA filters with or without partitions, while ULPA ultra-high efficiency filters can only be made into HEPA filters without partitions. The main design principle of the filter is to discount the filter paper in a W shape so that in a limited space, its filtering area is enlarged. The filtering area is controlled according to the depth of pleats and the spacing between pleats. The general pleat depth can vary, from 2.5 cm (CC) (1 inch) to 40 cm (16 inches). The pleat spacing is generally 12 to 16 pleats. Under certain conditions, fewer pleats are required, between 4 to 8 pleats per inch (EPA, 1998)/per inch.

    Because the filtration accuracy of the HEPA filter is very high, this type of HEPA filter is not reusable because of the high cost of the filter material. Considering the cost factor, the HEPA filter is not recommended to be used alone. It is generally necessary to install a junior high school Effective pretreatment and to protect the use of high-level filters and ensure the safe operation of clean rooms, it is recommended that the owner replace the initial effect every month, and replace the intermediate and sub-efficient (or the last section of the airing cabinet mentioned above) every 3 months. Use high-efficiency as a protection filter), which can guarantee the service life of the high-efficiency filter for more than 5 years (or even 10 years), and because the resistance of the new filter after the replacement is small, the air-conditioning load is greatly reduced, and the cost of filter replacement is much less The electricity cost required for the operation of the air conditioner. Frequent replacement of the pre-filter actually makes the air conditioner operate under low resistance load, saving a lot of electricity costs;