The compressed air that is discharged from an air compressor is in a raw form as it cannot be used. It is stuffed with impurities and contaminants like dirt, oil, water and heat. It is very obvious that the raw compressed air with such contaminants is of absolutely no use to the modern industry. The modern industry today uses very sophisticated machinery, which are to provide a high level of quality and high speeds of production. It is to achieve these high standards, that machine manufacturers are making accurate and highly sensitive machinery. These machines have very small orifices for the flow of compressed air, and also very small clearances and tolerances. In order to manufacture compressed air that is suitable to be used in modern machinery, the air needs to be processed. After processing, the air will no longer be raw. It will now be clean, cool, pure and dry. For this the raw air needs to be filtered.
What is Filtration?
Filtration is an important process, which is often neglected. Filtration is the process of removal of dirt and oil from the compressed air. In many cases, these contaminants pass off unnoticed and when they destroy the machine parts, the damage stands out and is realised. Sometimes, due to lack of awareness in the users of compressed air, these glaring damages are often over-looked and explained as normal wear and tear of the equipment. But, in reality, it is not as normal as it is made out to be. And it should be remembered that the difference between filtered air and unfiltered air usually translates to a huge sum of money.
Contaminants in the air
Dirt is one of the contaminants that the filters trap. It is a very harmful contaminant in the compressed air and acts like the weapons would do in the army. The dirt particles, getting momentum from the compressed air, act like missiles or bullets and they continuously bombard the internals of the compressed air system. This continuous bombarding of the internals by the dirt particles will create pock marks on metallic, glass or any hard surface and eat away the softer metal. This reduces the life of the machinery, pipeline, seals, moving parts etc. This increases the expenditure necessary on maintenance activities and the replacement costs become more. Further, when this dirt comes in contact with moisture or any other liquid, then the dirt particles stick to the walls and the internal parts of the machinery. It also coagulates with each other to form larger lumps. This in turn chokes orifices and openings restricting the air flow. This will call for cleaning and maintenance and cause sluggish movement of the machinery, thereby drastically reducing production speeds.
The internal damage normally remains undetected till the time the whole system collapses and the system has to be opened for repairs. At such a time, the worn-out parts are replaced but the problem still continues. Users can look forward to unplanned and unexpected breakdown of their instruments and machinery when they least want it. The process is like a blind man walking through a thorny bush, getting hurt each time and then bandaging the wounds. This is just a cure for the wounds, but main problem still remain the same. Tackling the problem at the roots would entail preventing the dirt from flowing along with the compressed air. If one can prevent dirt from attacking the system, one need not worry about repairing the machinery. Further, when one talks of the food, pharmaceutical and glass industries, where the air comes directly in contact with the end product, the damages that the dirt particle can inflict on the products should be considered.
Oil is another major contaminant in the compressed air, and a little more difficult to remove from the system. It has to be understood very clearly that the oil that is in the compressed air system is in a disintegrated condition and has lost its capacity to lubricate. The oil has passed through the compression chambers of the compressor where the temperatures are as high as 200°C. The oil cannot sustain such high temperatures and most of it will disintegrate to form carbon. This carbon and oil mixture will carry over into the compressed air system and it is no more a lubricant now. It is sludge! The sludge will scour the moving part and choke small orifices and any openings. This will further mix with the dust particles and the sludge will get thicker. As the air flows through the system, the problem increases and the general result will be a slow and sluggish movement of the machinery and lower production levels.
Principle of filtration
The compressed air will flow from the inside of the element to the outside. There are multiple layers of the Borosilicate Glass Microfibre cloth, wrapped precisely with decreasing micron rating. Hence, the first layer of the filtering media will trap the larger dirt particles and the subsequent layers will trap the decreasing particle sizes. This would result in the protection of the finer layers of the filtering media from being damaged or choked by larger particles. Oil will coalesce as the air passes through the filtering media, and will form large droplets by the time it reaches the final layer. These large droplets then fall free from the element and collect at the bottom of the filter housing., which can be drained.
Clean air for trouble free operation
Clean air is very essential for trouble-free operation of the pneumatic machine tool that it is meant to drive. Filters are of course small elements in the pneumatic circuit, but they do mean a lot to the user, in terms of money and overall efficiency of the operation of the machine tool.
Filters are available with elements that are suited to filter the compressed air to different levels. The best efficiency of dirt filtration would be particles down to a size of 0.01 micron and oil removal down to 0.003 mg/m3.