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Sunday, December 19, 2010

Factors Governing the Selection of Compressed Air Filters

Compressed air filters are designed to remove air borne particles from a moving, pressurized air stream.

Compressed-air filter, 22 cfmCompressed air purification equipment is essential to all modern production facilities; at its best, the equipment should provide the optimum balance between air quality and low operating cost. There are numerous manufacturers offering products for the filtration and purification of air; compressed air filter costs cover a wide range - but initial purchase cost cannot always indicate the effectiveness of a piece of equipment. In assessing the suitability of the product, the purchaser will want to assess:
  • delivered air quality required by their application
  • environmental impact of use
  • overall cost of operation over the life of the equipment

One way to make these assessments is to compare the performance standards of the different manufacturers' products according to the standards that apply via ISO (the International Standards Organisation) under which there are a series of standards covering Compressed Air Quality. There are nine areas of quality classification for the main air contaminants as well as testing methods for them. The air purity classifications dictate how much contamination is allowable per cubic metre of compressed air. These classifications are used by manufacturers to rate the air delivered by their products. In this way, users can easily compare and contrast the performance of different products. The caveat to this is that the test methods were originally developed to verify air quality in the system rather than testing the purification equipment which means that not all products are tested in the same way.

The selection of the correct air filter for compressed air depends on specific parameters of use and location. Compressed air quality regulations are governed by the widespread and growing demands of industry. In manufacturing technology (for example, in food and beverage production, hospitals, electronics manufacturing or pharmaceuticals), quality of compressed air is relative to use and differs widely. Air filters therefore need to be selected for the properties that best match the air quality needed to prevent downtime, systems breakdown or low productivity. Where air impurities such as viruses, bacteria or possibly dust from insecticides present great danger, the selection of filter and filter material is of huge importance. The exact grade of air quality required differs therefore, according to the factors at play.

Delivering dry, contaminant-free air allows more efficient, effective and economical operations. Damage occurs to plant and equipment when water, oil, gases and dust enter into systems such as pipelines and fittings; compressed air filters and dryers can help eliminate the conditions for such damage/malfunction.

It is generally held that there are 10 major contaminants found in compressed air. Nine of these are removed using filtration technology. Filter design is based mostly on what works! In other words, development is largely empirical - the result of experiment and observation. Filter material design and specification needs to demonstrate better than adequate retention capacity, separating ability, a stable pressure build up and low pressure loss.

The type of material and its weight, the thickness of layer, loss of pressure at nominal volume flow, volume flow per unit of surface and permissible static pressure difference are all considered in the specification of filter material. However, due to the wide range of locations and conditions in which compressed air is used, these are only foundational specifications; there are other elements that need to be accounted for such as chemical and thermal resistance for example.

In conclusion, compressed air filters have a wide range of applications and selection of the most suitable will depend not only on cost (possibly this is the least important factor) but on the contaminants to be removed, the operating environment, the air quality delivered, environmental impact, and the overall cost of operation over the lifetime of the product.

Caron Rose writes for HP Pneumatics, an Aberdeen company of pneumatic engineering experts. HPP supply and fit pneumatic tools for industry, as well as repairing, servicing and installing pneumatic and compressor systems. The service offered to customers is of the highest priority - and is based on experience, competitive prices, extensive stock holding and speedy delivery.

For more information about our pneumatic air tools, services or products, call us for an informal chat on +44 (0) 1224 783371.

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