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The Importance of Cooling Compressed Air

There’s a science to the safe operation of air compressors – some physics, some chemistry – and a basic understanding of that science, type of compressors and why cooling compressed air can be very important.

Now, perhaps you weren’t paying attention when your high school physics teacher was explaining the principles of thermodynamics and giving that speech about gases. The Ideal Gas Law, or General Gas Equation, “is the equation of state of a hypothetical ideal gas and provides a good approximation of the behavior of many gases under many conditions.” You may not have thought it important at the time, but this principal is important now, especially if you plan on operating an air compressor.

And it’s important for some very good reasons. The Ideal Gas Law tells us is that when the pressure on a constant volume of gas (air is a gas) is increased, the temperature of that gas will increase as well.

When operating an air compressor, and this is true of any piece of machinery, safety is, of course, of paramount importance. Compressed air can reach temperatures exceeding 300 degrees Fahrenheit. Without cooling discharged air at that temperature, serious damage can occur; to the equipment and to the user.

In addition, air discharged from a compressor at the above temperatures is typically not usable by air-operated equipment, as high temperatures are not good for lubricants and sealing materials. Hot air contains large quantities of moisture vapor that can condense and contribute to rust, scale build-up, washing out of lubricant and can lead to freezing issues when operated in cold weather.

Several factors can lead to overheating. Like any piece of machinery, an air compressor needs proper maintenance. When not properly maintained, you could face overheating due to dirty or broken filters, pipe blockage, or blocked interior components. In addition, as equipment ages, wear and tear on parts can also lead to problems, including overheating.

Two causes that are specific to air compressors are inadequate ventilation and ambient temperatures. A compressor needs ventilation in order to cool itself. It also needs to operate in an environment that provides ample access to air that is not overly warm. To reduce the chances of an overheat, make sure that your compressor has plenty of access to cool ambient air.

It does not require an expert to recognize some of the symptoms of an overheating mobile air compressor.  It is important, however, that diagnosing an overheating machine be done quickly when symptoms begin to show. What should you look for? Hard starting is one. If your compressor stalls during startup – or worse, won’t turn on at all – it may be overheating.

Another sign? If the machine is needing longer rest periods between cycles or is taking longer to reach peak operation. Another possible sign of overheating can be detected simply by listening. Creaking or grinding sounds could be indication that internal parts are not getting proper lubrication due to excessive heat. 

Usually accompanied by the odor of something burning – most often lubricant or perhaps, seals – this condition can do extreme damage to your machine. Should your compressor give off any hint of something burning, it should be cut off immediately to prevent serious damage.

The two most common mobile or portable air compressors are rotary screw air compressors and reciprocating (or piston) air compressors. 99% of portable diesel and electric compressors are rotary screw – which use a screw element to compress the air – and there are very good reasons why. Unlike piston compressors, screw compressors don’t rely on valves or pistons that can lead to unbalanced operation.

As a result, the rotary screw compressor can operate at extremely high speeds. In addition, this type of compressor is capable of a significant flow rate while occupying a relatively small footprint. Rotary screw compressors are ideal for continuous, workplace and industrial applications because of their energy efficiency, low noise output, small footprint, low oil carryover and zero capacity loss over time.

Along with the two types of compressors, there are two steps to cooling compressed air; the intercooler and the aftercooler. First, the intercooler removes heat from the air before engine intake. Functioning as a heat exchanger, the intercooler allows for a greater flow of air into the compressor and does so by increasing the air’s density. This in turn boosts the compressor’s overall efficiency and power output.

Then, the aftercooler cools the air discharged from the compressor while, at the same time, removing moisture that would otherwise condense and damage the pipe system. Intercoolers and aftercoolers, working together, cool the compressed air by removing the heat generated during compression.

Two methods of cooling can be utilized to facilitate this process: water cooling and air cooling. With the air-cooled aftercooler, the warmed compressed air travels through finned tubes or corrugated aluminum sheets. Cooler ambient air is then directed over those tubes or sheets by a motor-driven fan. The cooler, ambient air removes heat from the compressed air.

In the water-cooled version of cooling, the process is similar but with water being used. Cooling water is channeled through tubes running alongside the pipes containing hot compressed air, cooling it before it is discharged.

Operate your compressor safely and efficiently.

An air compressor overheat can cause costly equipment damage, downtime, and even personal injury on a job site. Regardless of the use, it is important that your air compressor be cooled to an appropriate temperature and to keep the air compressor from overheating.

As you can see, there is more than one way to cool a compressor. No matter which cooling method you choose, whether air cooled or water cooled, before operating a compressor it is always helpful to speak with an Atlas Apso professional. They can advise you on the type of cooler that makes the most sense based on your specific use. That way, you know that you’re operating the right equipment for the job, that you’re operating it safely, and that you’re operating it efficiently.

Portable Compressor - Size 1 - RockHill - Open view
Rob Johnston - VP and Business Line Manager Mobile Air Compressors, North America

Rob Johnston

VP and Business Line Manager Mobile Air Compressors, North America

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