When air is compressed, it is heated to a point that causes the water or moisture to turn to vapor. As the air begins to cool, the vapors turn to condensation, which can cause performance issues in a compressed air system. Many times this condensation forms in the basic components in the system like a receiver tank, dryer or filter.
It’s important to remove this condensation from the system before it causes any issues. There are four basic types of condensate drains that can be used to limit or prevent loss of air in the system.
The first method would be to have an operator manually drain the condensation through a drain port or valve. This is the least reliable method though as now it’s the operator’s responsibility to make sure they close the valve so the system doesn’t allow any air to escape which can lead to pressure drops and poor end-use device performance.
Secondly, a float or inverted bucket trap system can be used in plants with regular monitoring and maintenance programs in place to ensure proper performance.. These types of drain traps typically require a higher level of maintenance and have the potential to lose air if not operating properly.
An electrically actuated drain valve can be used to automatically drain the condensate at a preset time or interval. Typically these incorporate a solenoid valve or motorized ball valve with some type of timing control. These types of systems can be unreliable though as the valve may open without any moisture being present in the line, which can result in air loss or it may not be actuated open long enough for acceptable drain off. With these types of drains, it’s best to use some type of strainer to remove any particulate that could cause adverse performance.
Lastly, zero air-loss traps utilize a reservoir and a float or level sensor to drain the condensate and maintain a satisfactory level. This type of setup is very reliable but does require the reservoir be drained frequently to keep the system clean and free of debris or contaminants.
If you have any questions or would like to discuss a particular process, contact an application engineer for assistance.
We’ve seen in recent blogs that Compressed Air Dryers are an important part of a compressed air system, to remove water and moisture to prevent condensation further downstream in the system. Moisture laden compressed air can cause issues such as increased wear of moving parts due to lubrication removal, formation of rust in piping and equipment, quality defects in painting processes, and frozen pipes in colder climates. The three main types of dryers are – Refrigerant, Desiccant, and Membrane. For this blog, we will review the basics of the Refrigerant type of dryer.
All atmospheric air that a compressed air system takes in contains water vapor, which is naturally present in the air. At 75°F and 75% relative humidity, 20 gallons of water will enter a typical 25 hp compressor in a 24 hour period of operation. When the the air is compressed, the water becomes concentrated and because the air is heated due to the compression, the water remains in vapor form. Warmer air is able to hold more water vapor, and generally an increase in temperature of 20°F results in a doubling of amount of moisture the air can hold. The problem is that further downstream in the system, the air cools, and the vapor begins to condense into water droplets. To avoid this issue, a dryer is used.
Refrigerant Type dryers cool the air to remove the condensed moisture and then the air is reheated and discharged. When the air leaves the compressor aftercooler and moisture separator (which removes the initial condensed moisture) the air is typically saturated, meaning it cannot hold anymore water vapor. Any further cooling of the air will cause the moisture to condense and drop out. The Refrigerant drying process is to cool the air to 35-40°F and then remove the condensed moisture. The air is then reheated via an air to air heat exchanger (which utilizes the heat of the incoming compressed air) and then discharged. The dewpoint of the air is 35-40°F which is sufficient for most general industrial plant air applications. As long as the compressed air stays above the 35-40°F temperature, no further condensation will occur.
The typical advantages of Refrigerated Dryers are-
– Low initial capital cost
– Relatively low operating cost
– Low maintenance costs
If you have questions about getting the most from your compressed air system, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
EXAIR Cabinet Cooler Systems are able to cool your electrical panels using only clean, dry compressed air. Other systems such as cooling fans or heat exchangers use ambient air full of dust and humidity. The temperature of ambient air also fluctuates with the seasons and will be very warm in the summer months, which degrades their ability to cool as the temperature rises. One of the myths about compressed air cooling is that humidity from the compressed air source will enter the cabinet. A water/dirt filter separator will prevent condensate from entering the cabinet and since relative humidity is carried away with the hot air exhaust, relative humidity will stabilize to 45%. This video shows how quickly EXAIR’s Cabinet Cooler Systems will have an effect on relative humidity.