COMPRESSED air provides power to some of the most demanding applications, such as braking and suspension systems, pantographs, and pneumatic doors, but it can easily become contaminated with atmospheric dirt and water. If further contamination induced by the power source, the lubricated compressor, is added, oil and wear particles will mix with the dirt and water to produce a cocktail of contamination in the form of a gritty paste resembling mayonnaise, which is devoid of lubricating properties.
If these contaminants are not removed, and are allowed to pass into the compressed air system, the result should come as no surprise: system malfunctions and breakdowns. Unplanned and unbudgeted maintenance will be required, affecting the single most important objective each operator is striving to attain: a punctual and reliable service.
It therefore makes sense to provide high efficiency compressed air purification immediately downstream of the compressor. This can vary from a water separator and filtration to a complete compressed air desiccant drying package fitted with pre and after filtration. Only a compressed air desiccant dryer can remove the damaging water vapour to the levels required, but will always require high efficiency water separation and filtration to protect against oil, water and dirt contamination which otherwise will seriously impair prolonged operation.
By removing these contaminants, the best air quality will guarantee sustainable performance in any climate to the dependent applications.
Consequently, increasing awareness of the value of compressed air treatment in rail vehicles demands a higher quality of compressed air in terms of oil, water and dirt contamination removal. With the introduction of advanced pneumatic control systems and the ever increasing drive for economy and energy efficiency relative to operating and maintenance costs, the effective treatment of compressed air is a very attractive proposition.
There has been much conjecture recently about the application of oil-free compressed air on rolling stock which is important for the long-term operation and reliability of components. However, it can be achieved much more cost-effectively than by simply installing an expensive oil-free compressor.
The statement that oil-free compressors alone can provide oil-free air to critical applications without the need for any downstream air treatment equipment is a complete fallacy. In fact, an oil-free compressor is only "oil-less" in the sense that it does not use or permeate oil at the point of air generation. In other words, oil cannot be carried over by the compressor and into the compressed air system, and it does not refer to the "delivered air quality".
As all air compressors use the same ambient air irrespective of whether they are oil-free or oil-lubricated, they will all compress and carry over hydrocarbons, water vapour and dirt particles (mainly pollen and dust) into the compressed air system.
This will lead to liquid oil, water and dirt contamination. Atmospheric hydrocarbons can originate from industrial effluent and exhaust fumes, even from the locomotive itself, which, when compressed and condensed, will appear as liquid oil. Therefore, both types of compressors are prone to compressed air contamination which must be removed.
The concept of using oil-flooded or lubricated compressors together with effective air treatment has been well established, with the pharmaceutical and electronics industries examples of several critical industries requiring high-quality oil-free air.
Air treatment units
We offer such protection, with a range of air treatment units designed to combat the problems experienced with modern rolling stock which can be used in new vehicles or for refurbishment projects. By combining water separation and coalescing filtration technologies with desiccant drying, the compressed air can be purified to meet the requirements of the NF F11 100 standards for rolling stock as well as ISO8573-1:2010 air-quality standards.
The patented design enables the air treatment to be installed both internally and externally, using the smallest space envelope available for installation whilst also having the ability to withstand the rigours of shocks and vibration in arduous and extreme operating conditions and climates.
Addressing the cause rather than the symptom has enabled many operators to provide a long-term solution to contamination problems, rather than applying short-term fixes in the hope that the symptoms will disappear. This has resulted in longevity of operation, with significantly lower maintenance and operating costs with the added benefit of minimal downtime resulting in a more reliable service.
