Water vapor is a problem for process equipment that relies on compressed air. Sensitive controls and solid-state devices are the most at risk. The air compression process inherently traps free water from the surrounding air, which results in moisture in air lines. Without an air dryer installed, saturated compressed air accelerates wear and corrosion in downstream equipment.
Air dryer technology separates suspended water vapor from the compressed air. Removal of the water lowers the dew point of the air. The lower the dew point, the cooler the temperature of the air can drop before condensation takes place. Dew point varies proportionally with air pressure, and is the determining factor when sizing air dryers.
Removal of water vapor from compressed air is essential for protecting sensitive components. High quality air dryers, such as refrigeration dryers and desiccant dryers, remove water vapor and condensate before the air reaches vulnerable process equipment.
Refrigerant air dryers utilize dual air-exchangers as well as a refrigerant cycle. Hot air from the compressor flows through an air conditioned dryer and cooled. The cold compressed air then passes through the second exchanger, where the cold are is reheated from hot incoming air. This air drying process pre-cools incoming compressor air, while raising the temperature of air discharging from the dryer. By warming the discharge air, accumulation of downstream condensation is avoided.
Desiccant air dryers utilize silica gel, or activated alumina, as the desiccant. Discharge compressor air passes through a desiccant bead-filled tank where water removal takes place. Desiccant dryers remove the water content through adsorption onto the porous desiccant beads. Desiccant air dryers for sale today include regenerative type dryers that reactive the desiccant beads for extended service.
Several factors influence the appropriate type and size dryer required for a particular application or facility. The criticality of the equipment determines the required pressure dew point required. In addition, ambient air temperatures play a role in the selection and preferred location of the air dryer.
When sizing an air dryer, total flow capacity must be taken into consideration. An undersized unit will cause excessive airflow restrictions, resulting in reduced flow capacity. Other considerations affecting air flow capacity when sizing an air dryer includes dew point, lowest ambient air temperature, dryer inlet air temperature, and operating pressure.
Refrigerated air dryers require less upkeep than a desiccant dryer requires, but consumes slightly more power. On the other hand, deliquescent type dryers need periodic replacement of the desiccant beads.
Regardless the initial cost of sizing and installing a high quality air dryer, they pay for themselves quickly through reduced equipment failures and lost production.