Selecting the right dryer and receiver for a rotary screw compressor is key to ensuring efficient, reliable and cost-effective operation of the entire compressed air system. Improperly selected components can lead to air quality problems, increased energy consumption and even damage to pneumatic equipment.
The first step in the selection process is to accurately determine the need for compressed air and the required air purity class, in accordance with ISO 8573-1:2010. This standard classifies air in terms of its solids, water and oil content, and the required class depends directly on the compressed air application. For paint applications or in the electronics industry, air of significantly higher purity will be required than for simple pneumatic tools.
In the context of selection air dryer for compressors, a key parameter is its capacity, which must be at least equal to that of the compressor, and preferably slightly higher, to provide a reserve and cover any demand peaks. The operating pressure of the system must also be considered, as the dryer must be designed for the maximum pressure generated by the compressor. The temperature of the compressed air at the inlet to the dryer and the ambient temperature at the site also have a significant impact on its efficiency. Higher air inlet temperatures and higher ambient temperatures can reduce the efficiency of the dryer, so these parameters should be taken into account during selection.
There are different types of dehumidifiers available on the market, the most popular being refrigeration and adsorption dehumidifiers. Refrigerated dehumidifiers are widely used and economical to operate, offering a pressure dew point (PDP) of +2°C to +10°C, which is sufficient for most industrial applications. They are available in fixed or cyclic operation, with the cyclic versions being more energy efficient with variable air demand. Adsorption dehumidifiers, on the other hand, are essential for applications requiring very dry air, reaching PDPs as low as -70°C. They use hygroscopic materials to capture moisture and require periodic regeneration, which can be done cold (using a portion of the dried air) or hot (using electric heaters or hot air from the compressor). The choice of the appropriate type of dehumidifier depends on the required air purity class, specifically the allowable water content.
Compressed air receiver selection also plays an important role in optimising system performance. It is assumed that the capacity of the compressor tank should be about 1/3 to 1/10 of the compressor capacity expressed in litres per minute. A larger receiver is generally more advantageous as it helps to stabilise system pressure, reduces the frequency of compressor cycles (which can prolong compressor life and reduce energy consumption, especially for fixed-speed compressors) and acts as a buffer in the case of short-term but intensive air consumption. In addition, the tank enables condensate pre-separation, which reduces the load on the dryer. However, it is important to remember to drain the condensate drain valve regularly. When selecting the receiver, it is also worth considering the potential future increase in compressed air demand. The maximum allowable pressure of the receiver must be higher than the maximum operating pressure of the compressor to ensure safe operation.
In summary, the choice of dehumidifier and tank for compressor requires a number of factors to be taken into account, such as the required air purity class, compressor performance, operating pressure and temperature, air receiver characteristics and potential future demand. It is advisable to consult with compressor and dryer suppliers who, based on a detailed analysis of needs and operating conditions, will help to select the optimum solutions to ensure efficient and trouble-free operation of the compressed air system. The importance of selecting these components correctly should not be underestimated, as it has a direct impact on operating costs, equipment life and the quality of the final product or process in which compressed air is used.
