The Basics of Air Treatment
Take control of your Air Quality
Compressed Air is a utility, similar to Electricity and Natural Gas, except that it is produced On-Site. Air is treated to remove 10 contaminants, from 4 different sources. Some of these are oil, water, particulate, dirt, micro-organisms, rust, and pipe scale. These contaminants come from air drawn into the compressor, the compression process, the air distribution system, and micro-organism growth from improper moisture or temperature control.
Air Treatment is crucial to prevent blockages, contamination, freezing, and system damage. This will boost efficiency and longevity. Some applications are required to meet Air Quality Standards or codes, such as in the food and beverage industry. Other applications, such as paint spraying, require air treatment to remove moisture that would otherwise damage the adhesion and finish of paint.
Oil can be present in condensate, which is a bi-product that must be drained during the compression process. This oil creates significant Hazardous Waste if not properly separated. You could be in violation of Laws or Regulations, and not even know it!
No matter the task, Air Treatment is key to increasing efficiency and system longevity, saving on energy costs, and minimizing down time and maintenance.
Compressed Air Dryers
Air Dryers control the moisture content in compressed air. Incoming air has a High Dewpoint, or high moisture content. Air Dryers lower the temperature of the air, causing water vapor to condense, and separate that water from the compressed air.
Air dryers use different processes to cool and dry air – Refrigeration Cycle or Desiccant.
Initial Cost is directly related to a dryer’s Efficiency:
More Efficient Equipment = Higher Initial Cost.
The high initial cost is earned back over time by energy savings and reduced air loss.
Refrigerated Air Dryers
Refrigerated air dyers are the most common, they use a refrigeration process and heat exchanger to cool incoming air. The cooler air causes moisture in the air to condense, and due to its higher density it will fall to the bottom where it can be drained off. Refrigerated air dryers are available in Non-Cycling and Cycling models.
Non-Cycling Dryers run constantly, while Cycling Dryers cycle on and off based on set points and system demand.
Desiccant Air Dryers
Desiccant Dryers use special resin media, usually desiccant beads, to constantly dry incoming air by absorbing moisture. They also mechanically Filter and Separate particulate and contaminants. Over time the desiccant must be replaced as the media reaches its absorbing capacity.
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Refrigerant Dryers |
Refrigerant (Non-Cycling) |
Refrigerant (Cycling) |
Desiccant Dryers |
| Advantages |
- Low initial cost
- Low maintenance
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- Minimal dew point swings
- Low initial cost
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- Energy efficiency at low air flow or low moisture
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- Low dew points achieved
- Cost effective
- Portability options
- Also acts as filter and separator
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| Disadvantages |
- Limited dew point capability
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- Continuous operation = less energy efficient
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- Dew point swings
- High initial cost
- Larger/heavier machine
- Shorter equipment life, cycling on and off
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- High initial cost
- Desiccant replacement (required 3-5 years)
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Compressed Air Filters
Coalescing, or Adsorption Filters, remove solid particulate, oil, and water vapor by use of media fibers. Filtered moisture falls to the bottom and is drained off, usually by a float type drain valve. Typically, filters are installed in pairs – one general purpose filter, one high efficiency filter, which experience up to 99.9% efficiency.
Dry Particulate or Dust Filters remove solid particulate and micro-organisms.
Line filters are rated by their flow capacity, and level of filtration. Filtration ratings are typically by particulate size measured in microns, and oil content measured in ppm (parts per million).
Water Separators
Water Separators, or Water Traps, are simple and cost-effective at bulk condensate removal in air lines by use of a special filter media or by a special internal mechanism. Inside some water traps, there is a device that spins or changes the direction of flow. The purpose is to separate water from moving air, either by centrifugal force or change in direction. Due to the difference in densities of air and water, the water will fall to the bottom and easily drain out. They can be installed upstream, downstream, or at the point of use in a system.
Oil/Water Separators
Air discharged during the compression cycle has oil and condensate present, which must be drained. The condensate comes from the humidity or moisture in incoming air. The oil comes from lubricating system in the compressor pump. Further separation of oil from condensate is crucial to eliminate producing hazardous waste. Improper control of hazardous waste results in a violation of laws and regulations, and damage to the environment! There are very simple and cost-effective ways to operate equipment more efficiently, and while properly controlling biproducts. Oil/Water Separators trap oil using special media material, allowing oil-free and non-hazardous waste to safely drain.
