What is Pressure Dew Point?

Pressure dew point (DTP) refers to the temperature at which the water vapor in the compressed air begins to condense into water. As air compressors compress air, temperatures within your compressor will rise. As the temperatures rise, the water vapor within the air also rises. This means that when the air cools down, this water vapor can turn to condensation.

Pressure Dew Point vs. Atmospheric Dew Point

While pressure dew point refers to the temperature at which water vapor within the compressed air condenses, atmospheric dew point refers to the temperature at which the water vapor within the air around the compressor condenses without the influence of pressure. When dealing with air compressors, we focus on pressure dew point (DTP).

Atmospheric Dew Point vs. Relative Humidity

Atmospheric dew point is directly related to relative humidity; however, they are not the same thing. Both terms are referring to the moisture content of the air but dew point deals with the specific temperature that condensation occurs, while relative humidity displays how close the air is to saturation compared to the maximum amount of moisture it can hold at a given temperature. Relative humidity is represented as a percentage.

How Are Atmospheric Dew Point, Pressure Dew Point, & Relative Humidity All Related?

The atmospheric dew point and relative humidity of the environment that the compressor is pulling air from can have an impact on the inside of the compressor as the external air flows through the system. This can ultimately affect the pressure dew point of the system. While other components may play a larger role in changing your system’s pressure dew point, being aware of environmental conditions like atmospheric dew point and relative humidity are also important to running a successful compressed air system.

Why Pressure Dew Point Matters

Too much condensation built up in your compressor can cause major issues within your operations from damaging your air lines to contaminating the end product. Because large amounts of moisture in your compressor and/or its airlines can cause contamination and complications, it is important to prevent your air compressor from reaching its dew point, thus it is important to understand and know your unique compressor’s DTP. Maintaining a low-pressure dew point both reduces the maintenance time and costs your system may need, as well as reduces downtown of your system that would otherwise be needed to inspect and repair piping or other components that may have become damaged from moisture.

How To Measure Pressure Dew Point

Properly measuring air compressor dew point requires utilizing a special dew point sensor. These sensors, like a Hygrometer, can be worked into the entire air compressor system for ease of use and accuracy in measurement. Many modern air dryers also have built-in sensors that can provide continuous data on the moisture levels of the pressurized air flowing through the dryer. Ideally, when installed properly and maintained correctly, these sensors will function year-round requiring minimal adjustments and a once-yearly calibration review.

How to Maintain Low Pressure Dew Point & the Necessary Equipment

Keeping your air dry is the best way to ensure the air does not reach its pressure dew point. Air dryers are an essential piece of equipment to ensure your pressure dew point stays at proper levels. Air dryers are made to remove moisture from the process air and cool the temperature down. There are many different kinds and configurations of air dryers. If you want to learn more about the specifics of air dryers, read our blog post, “Everything Air Dryers,” in our Resource Center. Other pieces of equipment such as filters, after-coolers, and air storage tanks can also help to reduce the dew point of your air by separating moisture from the air. 

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