When it comes to compressed-air systems, equipment performance is only as good as the quality of the air itself. Unfortunately, the high-pressure air that these systems produce is wet and dirty. Air dryers and filters keep a compressed-air system operating efficiently, but only if they are properly maintained.
All atmospheric air contains some moisture and dirt. No matter how small the amount of contaminants initially, they are concentrated when the air is compressed. As the air heats up, its ability to hold water vapor increases. When the air begins to cool as it travels downstream, the vapor condenses into liquid.
Possible consequences of that condensation include, among other things, leaking seals, rusty or scaling pipelines, premature wear of moving components, and similar problems that can lead to subpar operation, equipment failure, and even damaged finished product. Plant personnel can prevent many of these headaches by selecting the right types of air dryers and filters to remove the liquid and particles and by performing regular maintenance on these
Compressed-air experts at Mazeppa, MN-based La-Man Corp. (laman.com) offer several tips regarding air dryers and filters. Keep them in mind.
—Jane Alexander, Managing Editor
Types of dryers
Most compressors incorporate an aftercooler to reduce the temperature of the compressed air. Air dryers are often installed to further reduce the moisture content. There are four major types of air dryers:
• chemical or deliquescent
• regenerative or desiccant
• membrane or mechanical.
The simplest, most economical dryer is the membrane or mechanical type. It uses a textile filter made up of thousands of individual fibers to trap large particles and cause moisture to form large droplets (coalesce). These particles and droplets collect at the filter’s base and are drained off. Water vapor passes through the filter to a sweep chamber, where it is vented.
Mechanical systems are typically installed at the point of use (unlike desiccant-type dryers that are placed near the air compressor to capture water vapor). At this point, air temperature has cooled sufficiently to permit water droplets to form and be captured by the system.
Impact of air filters
Mechanical filters work with compressed-air dryers to remove water and other contaminants from the compressed air and prevent component contamination. Three types of filters are typically used:
Particulate filters are typically made of a fine mesh glass fiber, plastic fiber, or woven wire cloth. They remove large particles using centrifugal force, while smaller particles are strained out. The filter is rated by the largest-size particle it will allow to pass. These types of filters work hand in hand with coalescing filters.
Coalescing filters are high-efficiency filters that use a fine stainless-steel mesh or woven fiber cloth (such as a cotton co-knit) to remove water and lubricants from the compressed air. They are often installed downstream of a particulate filter.
Adsorption filters use activated carbon to remove gaseous contaminants from compressed air. They adsorb the oil vapor into the pores of the carbon granules and must be replaced once saturated with collected oil. They are point-of-use filters, which should be supported upstream by a coalescing filter. Typical uses for adsorption filters include sanitary environments, such as paint spray booths, clean rooms, and food and beverage manufacturing.
Bottom line: Using—and maintaining—filters dramatically improves the performance and extends the life of compressed air systems. MT
For more information on solutions that remove water, oil, and contaminates from compressed air systems, visit La-Man Corp. at laman.com.