Miscellaneous Mechanical ComponentsDOE-HDBK-1018/2-93AIR COMPRESSORSAir Compressors Summary (Cont.)The centrifugal force utilized by the centrifugal compressors is the sameforce utilized by the centrifugal pumps. The air particles enter the eye ofthe impeller. As the impeller rotates, air is thrown against the casing ofthe compressor. The air becomes compressed as more and more air isthrown out to the casing by the impeller blades. The air is pushed alongthe path on the inner wall of the casing. The pressure of the air isincreased as it is pushed along this path. There could be several stages toa centrifugal air compressor just as in the centrifugal pump, resulting inhigher pressure.Rotary compressors are driven by a direct drive that rotates a mechanism(impellers, vanes, or lobes) that compresses the air being pumped. Theactual compression of the air takes place due either to centrifugal forcesor a diminishing air space as the impellers rotate.Cooling systems are required in compressed air systems to remove anyheat added by the compression. The advantages to cooling the compressedair are that cool air takes less space and holds less moisture. This reducescorrosion and allows more air to be compressed into a given volume.Hazards associated with compressed air are similar to hazards of any highpressure system. Three general hazards include the following.Small leaks or breaks can cause minute particles to be blown at speedshigh enough to cause damage. Goggles or safety glasses should be wornwhen working around compressed gas. The compressors, especially larger ones, can be quite noisy when running.The cycling of automatic drain valves contributes noise as well. Hearingprotection should be worn around compressors. Pressure swings may cause system damage. Closed valves in acompressed air system should be slowly cracked open and the pressureshould be allowed to equalize prior to opening the valve further. Systemsshould be depressurized prior to opening for maintenance. Oil should bekept out of air systems to prevent possible explosions.Rev. 0ME-05Page 9
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