SECTION 2 Safety and System Precautions
- Use EXTREME CAUTION when working in the vicinity of the dryer.
- Relieve pressure before servicing dryer or associated equipment.
- Disconnect power before servicing dryer.
- Use ear and eye protection when in the vicinity of the dryer or exhaust ports, especially if the dryer is
being operated without mufflers. Even when mufflers are used, a tower blowing down to atmosphere will
raise particles, create more noise than during “normal” operation and may startle an individual not used
to this portion of the operation.
- In the case of an overpressure situation there is a safety relief valve on each tower designed to protect
the equipment. If these end up pointed in a hazardous direction after dryer installation, they should be
piped to safe location.
- Automatic or manual drain valves will eject water, oil, particulates and air under partial pressure when
operated. Proper precautions must be taken.
- Condensate drainage from compressed air systems may contain oil or other contaminants. Follow all
applicable regulations for safe handling and disposal.
- Various component failures could cause large air loss and subsequent pressure drop. Preventive
maintenance should be performed to reduce the likelihood of this. If this occurs, bypass the dryer
immediately to restore flow and pressure.
- Activated Alumina dust is considered a nuisance dust. Proper precautions should be taken when
handling desiccant. For more information and for other types of desiccant, refer to applicable Material
Safety Data Sheet. For disposal of used desiccant refer to the applicable regulations.
NOTE: Desiccant contaminated with oil or other foreign substances may be covered under disposal
regulations for the contaminant.
SECTION 3 General Operation
Desiccant dryers work on the principle of adsorption. Adsorption is the process of removing water VAPOR
from the air to be dried. All condensed liquid water should be removed from the inlet air stream prior to
reaching the dryer by suitable separators, traps, filters, and drains. The dryer can not be burdened with
liquid condensate carry-over.
All desiccants are adversely affected by oil, aerosols, dirt, rust, scale or liquid water. Effective pre-
filtration in conjunction with automatic condensate drainage is a must for proper dew point
suppression and long desiccant life.
The saturated inlet air is alternately cycled through each of the two desiccant beds. One bed is “on-line”
at full line pressure and flow, adsorbing water vapor from the saturated inlet air. This is the drying bed.
The other bed is “off-line” at atmospheric pressure (0 PSIG) being regenerated by a depressurized
portion of the dried outlet air (purge air). This is the regenerating bed.
The quantity of purge air for a standard pressure dryer is approximately 15% of inlet design flow. This air
is taken from the dry air outlet, directed through the purge flow controls, purge check valves, desiccant
bed, and finally exhausted to atmosphere to accomplish regeneration. Purge air consumption is typically
the largest cost involved with operating a heatless desiccant air dryer. (Purge air is “non-recoverable” and
the air system in question must be designed to allow for this usage.)
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