Compressed air filters vs ventilation air filters

Whether it is a ventilation air filter, or compressed air filter, routinely use physical barrier technology to separate other components of the medium, such as: solid particles, water droplets and aerosol impurities such as oil mist, so as to obtain clean air.

They have different working environments, filter objects and working pressure ranges. Ventilation air filter is mainly used to purify the air in the natural environment, in air conditioning, clean plant, workshop and other areas of application, its working pressure is in the vicinity of atmospheric pressure; compressed air filter is mainly used for compressed air that is pipeline air, its working pressure from a few atmospheres to several hundred atmospheres.

The usual categories and characteristics of ventilation air filters:

1. Coarse filter: mainly used to trap suspended particles of 5μm or more and settled particles of 10μm or more, as well as various foreign bodies, to prevent these impurities from entering the clean space. Mainly used for the first filtration of the air supply system, efficiency in 80% ≥ η ≥ 20%, efficiency to filter 5μm shall prevail.

　　2) Medium efficiency filter: mainly used to trap suspended particles of 1μm~10μm. Mainly used for air conditioning system filter, efficiency in 70% ≥ η ≥ 20%, efficiency to filter 1μm shall prevail.

　　3) High and high efficiency filters: mainly used to capture suspended particles of 1μm ~ 5μm. Mainly used for the end of the system of high degree of purification, efficiency in 99% ≥ η ≥ 70%, efficiency to filter 1μm shall prevail.

　　4) Sub-high efficiency filter: mainly used to trap sub-micron particles below 1μm. Efficiency in 99.999% ≥ η ≥ 99.9%, efficiency to filter 0.5μm shall prevail.

　　5) High efficiency filter: mainly used to capture ≤0.5μm or ≤0.1μm sub-micron particles. Efficiency in η ≥ 99.999%, efficiency to filter 0.3μm or 0.1μm whichever.

　　Among them, because of the high difficulty of filtration of tiny particles, for this reason high-efficiency filters are usually further divided into four categories A, B, C, D, to meet the requirements of different filtration precision, filtration efficiency.

　　6) Ventilation air filters are mostly made of fibre, glass fibre, meltblown fibre mesh, ePTFE film, etc.. Its structure form is also mostly frame type, which is usually placed outdoors, but also consider beautiful, reliable, smooth eye.

Characteristics of compressed air filters:

1)The main task of the compressed air filter is to filter out all contaminated impurities in addition to water vapour in a targeted manner.

　　2) Because the physical properties of the compressed air have obvious changes, such as temperature, pressure, density, enthalpy, etc., with the pressure increase and the corresponding increase, than the volume is inversely proportional to the pressure decline, while the compression of the unit gas volume in the concentration of impurities greatly increased, such as oil mist, oil vapour, etc., and the saturated state of liquid water. Therefore, the compressed air filter has to withstand high temperature, high pressure, high humidity and load amount of pressure. The temperature may be above 80°C and the pressure to tens of atmospheres of instant impact.

　　3) Based on the principle of different surface areas inside and outside the filter element to make changes in the flow rate of incoming and outgoing gas, compressed air filter knots are mostly cylindrical, one can apply a variety of filtration mechanisms to improve the filtration efficiency; the other is considered from the pressure-bearing point of view.

　　4) Due to the different purposes of the use of compressed air in various industries and processes, the filtration accuracy of compressed air and impurity content requirements are different. For this reason, the filter material used for compressed filter cartridge is also richer, such as: fiber, ceramic, filter paper, non-woven fabric, sintered metal, etc.

　　5) In the compressed air filter work, the intercepted water (in addition to water vapour) and impurities mixed with water will flow down together with gravity and accumulate in the filter cartridge, but can not be discharged directly out immediately, for this reason, it is usually also equipped with a manual or automatic water drainage device, monitoring the level of the view window.

　　6) As the compressed air is sealed in the filter cartridge with pressure, in order to keep track of the use of the filter cartridge in the cartridge, it is usually also equipped with a differential pressure indicator of the pressure drop of the import and export air to indicate the extent to which the filter cartridge is blocked, which also represents the service life of the filter cartridge.

　　In conclusion, compressed air filters and ordinary air filters have their own areas of application and demand, and their structural design and filter mechanism design are also different.

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