Cooling is a crucial step in the compressed air process. The ideal gas law tells us when the pressure on any constant volume of gas increases, the temperature also increases. Compressed air is no exception; it can become as hot as 300 degrees F. Without cooling, this level of heat can damage equipment, hurt employees and compromise products.
There are two main steps for cooling compressed air. The intercooler removes heat from the air between compressor stages while the aftercooler is used for cooling air discharged from a compressor. Two methods can be implemented in each of these stages: water cooling and air cooling.
Most rotary screw compressors that are smaller than 150 hp use air coolers. Other small reciprocating compressors also use air coolers, specifically those with finned or ribbed cast cylinders. Multistage models incorporate a finned tube intercooler with a fan-type flywheel. These coolers must have an adequate supply of cool, clean air, particularly in hot summer months. Whether mounted in a boiler room or outdoors, these coolers should be kept in conditions below 100 degrees F during operation.
Unlike air coolers, water coolers are not as affected by the summer heat since they are not drawing from ambient air. However, there are specific considerations to keep in mind with a water cooler. Generally, a water cooled aftercooler produces compressed air temperatures of about 10-25 degrees F above the inlet water temperature. These systems also require, unsurprisingly, a reliable source of water on which to operate. Whether it is municipal, river or well water, it is important to consider what treatment will be necessary to ensure safety standards are met during use and disposal of the water. During cooling, some water coolers (specifically the evaporative cooling tower) scrub the air of potentially harmful contaminants, which in turn must be properly disposed of through approved methods.
Consider a Trim Cooler
Despite the significant cooling that occurs during and after the compression process, the compressed air may still be too hot for necessary operations. This is especially true in the summer months when air coolers are drawing from ambient air and water coolers are only able to reach approximately 10 degrees F above ambient temperatures. Trim coolers serve as supplemental coolers that can better achieve desired cooling when temperatures are still above the required limit.
Regardless of end use, it is important that compressed air be cooled to an appropriate temperature to prevent unnecessary equipment destruction, personnel injury or product damage. Hot air can allow your system to overheat, damaging equipment and resulting in costly repairs and downtime. Before choosing a cooler, ask yourself some questions. What is my end-use? What is a safe temperature? What type of cooler works best with my compressed air system? Am I using the right cooler to save money long-term? Knowing your needs and the ins-and-outs of different coolers can help lead you to the right cooling system for your compressed air. Check out Atlas Copco’s range of aftercoolers here.
What type of coolers do you use in your system? Let us know in the comments below.