How to select the right compressed air dryer system

In Australia, hot weather is a fact of life; and in many areas the hot weather will last for long periods of time. When temperatures and humidity rise, compressed air dryers may feel the heat and start to sweat, especially if they were originally designed for cooler annual average temperatures only. Since the saturation capacity of air rises the hotter it gets, insufficient drying can result in water infiltrating the compressed air network during such periods. 

Over a 24-hour period, an average compressed air system incurs an enormous quantity of condensate - 140 litres to be precise. If the compressed air is not dried following the compression process, water can condense when the compressed air cools. It can then accumulate in the downstream compressed air distribution network or even within the realms of the production process itself – which can have even more serious consequences, as water can then damage not only the compressed air system, but also downstream equipment that uses compressed air and the products being produced. 

So it’s extremely important to exercise due care in selecting the appropriate degree of compressed air drying for the specific process in mind.

The first step is to ensure the dryer design is correct. Determine the dimensions and equipment of the upstream compressor as well as the specifications and performance delivered by the aftercooler. Optimally, the compressed air inlet temperature at the refrigeration dryer should be as low as possible, to enable significant reduction of the downstream dryer’s power requirement.
The second step is to determine the potential maximum temperatures that occur during the year. In general terms, dryers should be dimensioned for the additional capacity to operate reliably during peak temperatures. It is therefore preferable to plan for slightly higher temperatures. 

The third step concerns fresh air supply and how it’s implemented; and the fourth step follows on from this one: determining the highest ambient temperature in the immediate vicinity of the dryer. 

Finally, it is crucial that the compressor’s aftercooler and the refrigeration dryer’s condenser be kept as clean as possible. Once all the above parameters have been specified, it is possible to determine the best design for achieving reliable dryer performance and delivery of compressed air at the required dryness level, even under extreme conditions.

Over the course of a working day, compressed air systems often experience considerable fluctuations in compressed air demand. Similar also occurs over the course of a year as a result of large fluctuations in temperature. Therefore, compressed air dryers should be designed to handle the least favourable operating conditions that may occur, for example: lowest pressure, maximum compressed air consumption, as well as maximum ambient and compressed air inlet temperatures.
This requirement used to be solved simply by continuous dryer operation, which – especially in partial load operation – led to considerable energy wastage. 

Modern refrigeration dryers with efficient cycling control, on the other hand….