Compressed Air Dryers & Compressed Air Treatment
Water in a compressed air system, if not removed, can damage production machinery, rust and clog pipes, shorten component life, and reduce air flow. This can result in costly downtime and quite possibly, defective products.
Proper compressed air treatment can remove water vapor and liquids from the compressed air system. Although installing an after-cooler and moisture separator is a good first step, a dryer removes water vapor before it can condense in the pipe line or in downstream equipment.
Refrigerated dryers are the most common type of air dryer. By using a refrigerant to cool the compressed air in heat exchangers, they condense water vapor to a liquid for separation and removal from the air through a moisture separator and an automatic drain. Pressure dew points of +35° F and up are available.
Most indoor applications use refrigerated dryers for their low initial cost and minimal maintenance. Controls range from basic gauge packages to microprocessor-based systems with RS232 outputs.
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Desiccant dryers are used when low dew points are required. This type can produce a pressure dew point down to -100° F or most commonly to -40° F.
Continuous duty dryers use a regeneration cycle to dry the "wet" off line desiccant tower while an on line tower dries the system air. Regeneration is available in a number of the following ways:
Heatless
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Refrigerated dryers
Non-cycling dryers will provide a constant dew point and work most efficiently with a consistent flow of air.
Cycling dryers can provide energy savings at periods of partial load by cycling on and off. While this may result in a varying dewpoint, there can be energy savings.
High inlet air temperature dryers can accept inlet temperatures to 180º F. This dryer will replace an after cooler, separator and filter to save on equipment and installation costs.
Variable Frequency Drive (VFD) refrigerated air dryers are the latest in energy efficient refrigerated dryer technology. This new type of dryer uses a variable frequency drive to change the speed of the refrigeration compressor to match the compressed air load while maintaining a constant dewpoint and reducing energy consumption. 
Desiccant Dryers
Heatless dryers are the least expensive to purchase, however sometimes the most expensive to operate. The regeneration purge air is approximately 15% of rated flow. This air is swept through the off line tower to remove the moisture. Sizing is available from 5 scfm to 5400 scfm in wall mountable to stand alone floor models. The entire plant load can be dried or a small branch line to prevent outdoor freezing such as a dust collector. Energy saving controls are available to reduce the purge flow at partial loads which reduces energy costs.
External and internally heated dryers use a heater located either inside or outside of the desiccant bed. The heat regenerates the desiccant with a small percentage of purge air required. While more expensive to purchase, heated dryers can be more efficient to operate than the non-heated desiccant dryers.
Blower purge dryers operate with an external heater or heat source such as steam and a blower to force the hot air through the desiccant bed. The switching from one tower to the other is controlled by a PLC on either a fixed time or a demand basis. A 1% flow of compressed air may or may not be used as a cool down period to minimize dew point spikes.
Heat of compression dryers use the heat from an air compressor discharge to regenerate the desiccant beds. This type can be one of the most efficient because of energy costs. Compressor type and loading must be considered when looking into this type. 
Pre-Filters
Particulate filters or pre-filters remove harmful oil/water condensate, pipe scale, dirt and rust from your compressed air system. This prevents corrosive damage to compressed air equipment and finished products. Typically, particulate filters are installed upstream of some refrigerated dryers and pressure regulators to prevent valve failure. They are also used as pre-filters to oil removing and coalescing filters to insure high efficiency and long element life in applications such as paint spraying, instrumentation and pharmaceuticals. Particle removal can be tailored to specific needs starting with either 40 or 5 micron bronze elements, and to 1 micron for extra-fine particle removal and are also used as afterfilters for desiccant dryers. When used as a pre-filter to a coalescing filter, pre-filters can increase the life of the coalescing element by 4 to 6 times.
A coalescing oil removal filter functions in a different way from a standard particulate filter, where particulate filters remove particulate and water, coalescing filters are designed to remove oil. Coalescing, by definition, means "to come together". It is a continuous process by which small oil aerosols come in contact with the fibers in the filter media, uniting with other collected aerosols and growing to emerge as a droplet on the downstream surface of the media which by its weight is gravitationally drained away. For maximum performance and efficiency, coalescing filters should be preceded by a particulate or pre-filter. Several grades of coalescing filters are available; from lower grade .3 micron units when longer element life and low pressure drop are a concern, to .001 micron. Coalescing filters are often used with critical instrumentation; paint spraying equipment; more sophisticated air systems; blow molding bottling; in the food industry, and where air blows on a finished product. The finest grade elements are offered for the most critical filtration applications, such as those found in clean rooms.
Activated carbon or adsorber filters were engineered specifically for those critical applications that will not tolerate the presence of oil vapors and associated odors. Activated carbon filters will remove oil vapor and hydrocarbon odors and should be preceded by a pre-filter and coalescing filter.
Scales Air Compressor carries a complete line of NFPA and breathing air filters. Please call one of our local offices for help with your specific needs.