By: Anina Diener

Air includes water, so moisture is always present in your compressed air to varying degrees depending on humidity and temperature. An accumulation of water can cause moisture to get pulled back into the compressed air stream. This can be especially problematic when you are using a compressor to spray paint because water can cause negative visual and texture effects on the finish sheen. Other uses where moisture is a real nuisance include sand and other material blasting, pneumatic tools, CNC machining centers, robotics, air cylinders, valves, and many other applications.

When a compressor draws in air, the air is compressed about 12 times normal atmospheric pressure. Moisture that is present as a vapor in air begins to condense. More condensation occurs as the compressed air moves through the system and cools. The effect is more pronounced in summer because of higher humidity.

While it’s impossible to prevent moisture from entering your air compressor, you can get rid of most of it. This is done in stages using different components throughout your system.

The first place of attack is in the receiver tanks. When compressed air emerges from the pump, it’s hot which temporarily keeps the water in its vapor state. But when it gets to the tank it will become liquid again and collects.

So dependable draining of the tank is crucial to getting rid of moisture in your air compressor system. This can be accomplished most simply with a manual drain but timer-based drains and pneumatic drains are other very useful options.

Another solution is a mechanical separator, which looks like an in-line air filter (air compressor oil separator). This filter, also known as a filtration water separator, removes large amounts of moisture from the air supply with centrifugal force. It can get rid of 40 to 60 percent of the water, and the air may be dry enough for your application at this point.

If further moisture removal is needed, look next to refrigerated air dryers. Temperature, pressure and moisture content are correlated, and by chilling the air this step take out more water. Refrigerated air dryers typically get you between a 34 and 40 degree dew-point which is sufficient for most applications.

Desiccant air dryers can be another step that gets air very dry and are helpful in painting, printing and instrument applications, or when compressed air meets ambient temperatures of less than 34 degrees. Desiccant dryers range from -40 degrees to -100 degrees in dewpoint based off of the selected model.
Contact one of our staff for more info on moisture removal for your application!