What is Dew Point?

April 23, 2019
When using air compressors, there are many variables that are integral to the quality and effectiveness of your compressed air. When dryer air is necessary, being able to constantly and accurately monitor dew points can be a critical factor to your operation.

Dew point is the temperature in which water vapor in your compressed air is no longer vapor, and changes to a liquid form (condensation). As your compressor is compressing air, the stored air can become very warm, meaning that it contains a lot of water vapor. As the air cools down, that vapor will turn to condensation. If enough condensation forms, you now have free-flowing water through your air lines. Having water in your compressed air is never a good thing, but depending on the application, it can become catastrophic.

Large amounts of water in your compressor and/or compressor air lines can cause bacteria or mold to form, as well as pushing moisture into your compressed air. This renders the compressed air useless in most applications. Food & beverage companies cannot use this air to package or enhance food products. Pharmaceutical or medical companies cannot use contaminated air or humid air in hospitals or for any medicinal applications. Body shops can’t use air that contains water to paint vehicles because it ruins the final product. Because condensation typically ruins compressed air for most applications, it is important to make sure you monitor your unit’s dew point as it is in operation.

How Do I Prevent My Compressed Air From Reaching Its’ Dew Point?

In order to monitor your compressor’s dew point and keep the air dry, an air dryer is often used for most compressed air applications. Dryers can be integrated (built-in) to the compressor, or they can be standalone units. Air dryers will lower the dew point of your compressed air, making it more difficult for the air to condense vapor into water. This keeps your air dry and your piping and hoses free of any moisture and potential for bacteria. There are 2 main types of air dryers you can use, depending on the dew point needed.

Refrigerated air dryers use the same cooling principal as typical air conditioning units in homes across the world. Using the refrigeration system and passing compressed air through a heat exchanger, the air is cooled to approximately 40 °F. As the air cools, water droplets begin to form in the air due to condensation much like the water droplets that form on the outside of a cold drink. The moisture laden air then undergoes a mechanical separation process where the liquid or “condensate” is separated from the air stream. The air is then rewarmed using the incoming air which lowers the relative humidity of the air and traps any remaining moisture in a vapor form.

A desiccant or adsorption dryer uses desiccant material to adsorb and remove the humidity from compressed air. With this method, a pressure dew point as low as -100 °F can be reached. A desiccant dryer should be used when the ambient temperature goes below freezing point, to avoid ice forming in pipes and applications.

For most compressed air applications, monitoring the dew point and making sure your compressed air doesn’t reach its’ dew point is critical to keeping your business running efficiently and effectively. Dryers are essential in keeping your compressed air cool and free of moisture and contaminants. To learn more about Pneumatech dryers, click HERE.