2024-03-11

Compressed air quality

It is essential for the user that the quality of the compressed air is correct. If air containing pollutants comes into contact with the final product, the cost of waste can quickly become unacceptably high, and the cheapest solution can quickly become the most expensive. It is important to choose the compressed air quality according to the company's quality policy, and even try to judge future requirements.
Why is Air Quality Important?
 
Compressed air may contain harmful substances, such as water in the form of droplets or vapors, oil in the form of droplets or aerosols, and dust. Depending on the field of application of the compressed air, these substances can impair production results and even increase costs. The purpose of air treatment is to produce a user-specified compressed air quality. If the role of compressed air in the process is clearly defined, it is simple to find the most profitable and effective system in a specific situation. One of the problems is to determine whether the compressed air will come into direct contact with the product, or whether oil mist is acceptable in the working environment, for example. A systematic approach is needed to select the right device.
 
How can filters help?
 
 
The filter essentially separates air particles from pollutant particles. The particle separation capacity of the filter is a result of the combined sub-capacities (for different particle sizes) described above. In fact, each filter is a compromise, because no filter is effective in the entire particle size range. Even the influence of the flow rate on the separation capacity of different particle sizes is not a decisive factor.
 
Typically, the most difficult particles to separate are between 0.1 μm and 0.2 μm (maximum penetration particle size). 2.35.png As mentioned above, the overall capture efficiency of the coalescing filter can be attributed to the combination of all occurrence mechanisms. Obviously, the importance of each mechanism, the particle size it produces, and the value of overall efficiency depend to a large extent on the particle size distribution of the aerosol, the air velocity and the fiber diameter distribution of the filter media.
 
Oil and water in the form of aerosols behave similarly to other particles and can also be separated using coalescing filters. In the filter, these liquid aerosols converge into larger droplets, which sink to the bottom of the filter due to gravity. The filter can separate the aerosol and the oil in liquid form. However, due to the inherent high concentration, oil in liquid form will cause high pressure drop and oil residue. If the oil is to be separated in vapor form, the filter must contain a suitable adsorbent material, usually activated carbon.
 
All filtration will inevitably lead to pressure drop, which is an energy loss in the compressed air system. A finer filter with a more compact structure will result in a higher pressure drop and may be blocked more quickly, which requires more frequent filter replacement and therefore higher maintenance costs.
 
 
The air quality regarding the number of particles and the presence of water and oil is defined in ISO 8573-1 (industry standard for air purity). In order to eliminate the risk of air pollution in critical processes, it is recommended to use only compressed air classified as class 0. In addition, the filter must be sized to not only correctly handle the nominal flow, but also have a larger capacity threshold in order to handle some of the pressure drop due to a certain degree of clogging.

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