What I need to know
Refrigerated compressed air dryers are the most used type for moisture removal from compressed air. They offer a blend of low cost of purchase, and installation with low operating costs.
These dryers use refrigeration system to lower the temperature of the incoming compressed air to just above freezing which condenses a great deal of the water vapor and separates the liquid water and draining it. The dried air is then passed into the compressed air plumbing.
The dryness of the air is quantified by using its dew point at pressure. The point at which water starts condensing while cooling the air is the dew point. The lower this dew point, the dryer the air. If the air within the compressed air plumbing does not get below the pressure dew point, the compressed air remains free of liquid water.
Dryer sizing is based on a standard and then adjusted for actual operating conditions. The standard is as follows for air cooled units:
Flow - in SCFM Compressed air inlet pressure - 100 PSIG (higher pressure raises the rating of the dryer).
Compressed air inlet temperature - 100 Deg. F (higher temperature lowers the rating of the dryer)
Rated pressure dew point - typically 35-40 Deg F. at 100 PSIG. Most climate control dryers are rated at 50 Deg F. at operation pressure
Cooling air (ambient) air temperature - 100 Deg F (higher temperature lowers the rating of the dryer)
For water cooled units the cooling fluid inlet temperature affects the rating of the dryer. Each manufacturer has it own standards.
Many piston air compressors produce air much warmer than 100 Deg F. and special high inlet temperature dryers are available to avoid adding aftercoolers to these systems.
The work a dryer needs to do varies with temperatures and air flow. In most systems the refrigerant compressor runs constantly and its energy usage is primarily affected by temperatures. By using valves that by pass the condenser, various styles of thermal expansion valves, the air temperature is maintained near the freezing point while the refrigerant compressor runs. By using cycling refrigerant compressors and using variable scroll compressors, electrical energy can be saved.
Maintenance
These driers need to have the condenser coils cleaned periodically and the drain valves repaired or replaced. For most applications, this should be done at least once a year and more often in dirty conditions.
Harris Equipment offer a wide range of refrigerated dryers from several manufactures to meet your requirements. |
