3 Factors Affecting The Filtration Efficiency of HEPA Filters

• Filter material: The selection and application of filter bag material is the core technology of bag-type dust collectors, which affects the performance and lifespan of HEPA filters. Different filter materials should be chosen according to the environment, nature, temperature, and technical requirements of the dust collection point, and corresponding technical protection measures should be taken. Filter bag materials should have the following technical properties: suitable for different temperatures, good peeling, easy to clean, good air permeability, low resistance, high filtration efficiency, high strength, able to withstand high-intensity cleaning, long service life, and reasonable price.

• Air leakage: Air leakage directly affects the dust collection effect and lifespan of the dust collector, and the air leakage rate should be less than 3%. Bag-type dust collectors usually operate under negative pressure, and air leakage can cause small circuit short-circuits. The dust collection system cannot handle enough air volume, resulting in positive pressure dust. Air leakage can also reduce the system temperature, causing moisture to stick to the bag, increasing the dust collection resistance, and reducing the filtration effect of HEPA filters.

• Filtration air velocity: Filtration air velocity is a very important parameter that determines the performance of the dust collector, and is also an important parameter to measure the bag-type dust collector. Filtration air velocity is closely related to the dust concentration, particle size, application, viscosity, gas temperature, moisture content, and cleaning method of the dust gas. When the dust particle size is fine, the temperature and humidity are high, the concentration is large, and the viscosity is high, the filtration air velocity should be lower, and vice versa. High filtration air velocity will increase the filter bag load, increase the filtration resistance, and result in short filter bag life and low efficiency.

HEPA filter frames are usually made of metal or plastic, to provide enough strength and rigidity. The design and manufacture of the frames must ensure the tightness of the filter under all operating conditions, and prevent unfiltered air from bypassing the filter medium. Knife cutouts and sealing strips on the frames can provide additional tightness and prevent air leakage.

In addition, HEPA filter frames can also be designed as single flange or double flange, to adapt to different installation requirements. Different thicknesses of HEPA filters have different resistances at the same air velocity. The thicker the filter, the larger the filtration area, which can reduce the filtration air velocity and the resistance.

The operating environment of HEPA filters also affects their performance and lifespan. For example, the maximum temperature and humidity that the filter can withstand, and whether it needs to be resistant to high temperature or corrosion. For special applications, special separator materials and designs may be required.