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Created on 09.16
Ensure your system stays dry and protected throughout the winter
A compressor user may think that their compressed air system is moisture-free but, when temperatures start to drop below 5˚C, this may no longer be the case.Older dryers can sometimes fail or lose their gas and then no longer provide the required 3 degrees dewpoint (Class 4 of the ISO 8573.1 quality standard).Such a failure may go unnoticed until the cold winter months when moisture drop-out leads to product spoilage.
Atmospheric air drawn into a compressor intake will contain particulate and water vapour. That is why the quality of compressed air is defined by the levels of different contaminants present in the airflow, which, to a large extent, dictate the air treatment needed to remove them. In particular, the presence of water in the air network when ambient temperatures plunge be can be a severe concern but a problem that, with the aid of appropriate water separators, filters, and dryers downstream, can be overcome.
The higher the air temperature, the more moisture the air is capable of holding - its relative humidity. Dew point is the temperature at which the water vapour in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. At temperatures below the dew point, the rate of condensation will be greater than that of evaporation, thus forming more liquid. But there is a significant difference between atmospheric dew point, the temperature at which the water vapour content of air reaches a saturation point without the influence of external pressure, and Pressure Dew Point (PDP). This is the fixed temperature of air and water vapour when subjected to a pressure exceeding the normal atmospheric pressure level. While one occurs naturally, the other is induced by an air compression system. Reducing the temperature of saturated compressed air by 10°C will reduce the moisture content of a compressed air supply by approximately 50 per cent.
Removing water vapour from the system will automatically lower the pressure dewpoint of the compressed air and significantly reduce the chance of damaging effects of accumulated moisture on sensitive equipment, the air distribution network, tools, and end products. This precaution is particularly necessary in the depths of winter when downstream freezing of any moisture content in the system could result in costly consequences. Even if the primary compressed air system is indoors, pipes may exit the heated space for some distance before re-entering another heated space. If condensate exists in the pipework, as it leaves a heated space, it will cool and potentially freeze when exposed to a colder ambient temperature. This is particularly true if the pipework has low points where liquid may be allowed to collect. Adding trace heating elements may overcome this hazard. Still, the best way to limit this likelihood and to prevent downstream freeze-ups is to reduce the PDP to a level below the lowest temperature point that the compressed air system could drop to. That is the role of the dryer. Dependent upon the application and the type of compressor system, there is a variety of different dryer technologies available to industry. The three main categories are Refrigerant, Desiccant or Membrane dryer, and each has different operating characteristics and degrees of dew point suppression. Dryer ratings usually are based on standard dryer inlet conditions. Deviations from these conditions, such as an increase in inlet temperature or a decrease in inlet pressure will reduce the dryer's rated capacity.
Now is the time to take steps to protect your compressor system and make certain it is still delivering air of optimum quality.If you have any demands,you can leave your information, and we will arrange for a professional service engineer to get in touch with you.
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