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How Air Dryers work

7/10/2012 12:48:58 PM | by Anonymous


Having unwanted particles in air such as water droplets and gaseous contaminants can slow down the manufacturing process in industries that require the use of compressed air. These particles can contaminate the air and cause machinery to wear out, thus increasing cost and decreasing productivity with more down time due to maintenance of spoilt parts. Therefore, it is very important to have such particles removed from the air before using compressed air. This is done through the aid of air dryers. These devices are important as they compress the air and remove contaminants such as water vapor, making the air more useable and efficient. Their application is most common in industrial and commercial facilities.


These dryers reduce the amount of liquid water (water vapor), hydrocarbon and hydrocarbon vapor from the compressed air. There are several ways that these contaminants can cause the mechanism that the compressed air would be used in to malfunction. Some examples of how moisture and contaminants can harm the system are through erosion, corrosion, microbial contamination and freezing. Valves, piping and other system components can be easily eroded by the moisture or water vapor trapped in the compressed air to be used. This is similar to corrosion where the water vapor or mist reacts with the salts or acids present within the system to form very corrosive solution that can harm the system or anyone who comes in contact with it. The moisture or contaminants can also provide for an ideal place for bacteria and mold to grow, producing harmful acidic waste. This is referred to as microbial contamination. Also, if used in countries or applications that have low temperatures in the surrounding, the water vapor or moisture could freeze within the system, therefore causing the system to malfunction. It is due to such causes that drying the compressed air is important to minimize damage to the mechanical instruments and increase efficiency.


The moisture or other contaminants in the compressed air are removed by cooling the air and collecting the moisture that condenses during the process and finally heating the air back to atmospheric temperatures. Of course, to remove contaminants, particularly water, the dryers do make use of tools such as refrigeration, desiccant absorption and membrane filtration. Some of these dryers may dry the air through different stages to prevent damages to the tools.


Different compressed air dryers have different specifications to serve the different needs of people; such as varying drying capacity, pressure, dew point operating temperature and motor power. The maximum volume of air that an air dryer can hold is referred to as drying capacity, similar to the highest pressure that the dryer can contain. Dew point tells a user of how cold the air can get before the air turns into water by measuring the amount of water vapor present in the air. Motor power refers in general to the pressure, dew point, dryer size and pressure that it can hold. Operating temperature, as the name would suggest, refers to the range of ambient operating temperatures that the dryer can function in.


How they function:

Dryers are generally categorized into three types: refrigerant dryers, deliquescent desiccant dryers and regenerative desiccant dryers. Refrigerant dryers work in a very simple way which is by cooling the incoming air to a dew point of 1-3 degree Celsius, which causes the water vapor in the air to condense and collect at the bottom of the separator, resulting in dryer air. In the deliquescent dryers, the temperature drops to about 10 degrees Celsius below the temperature of the air that enters the dryer. The desiccant present in these dryers dissolves with the water and collects at the bottom of the separator. In regenerative desiccant dryers, silica gel or other types of desiccants are used to attract the moisture out of the air allowing for lower temperature within the dryer without freezing.


These various types of dryers have their own advantages and disadvantages depending on the situation. No matter which dryer is used, drying of the air is a crucial stage in applications that make use of compressed air such as bus doors that use pneumatic systems.

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