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Air compressors collect and store air in a pressurized tank, and use pistons and valves to achieve the appropriate pressure levels within an air storage tank that is attached to the motorized unit. There are a few different types of piston compressors that can deliver even air pressures to the user.
Automotive compressors are combustion engine compressors that use the up-and-down stroke of the piston to allow air in and pressurize the air within the storage tank. Other piston compressors utilize a diaphragm, oil-free piston. These pull air in, and pressurize it by not allowing air to escape during the collection period.
These are the most common types of air compressors that are used today by skilled workers and craftsmen. Before the day of motorized engines, air compressors were not what they are today. Unable to store pressurized air, a type of antique air compressor may be found in the blacksmith's foundry bellows.
Now the air compressor is capable of building extreme pressures in storage tanks capable of storing enormous amounts of pressurized gases for industrial use.
The capacity of an air compressor is determined by the amount of free air (at sea level) that it can compress to a specified pressure, usually 100 psi per minute, under the conditions of 68°F and a relative humidity of 38 percent. This capacity is expressed in cubic feet per minute (cfm) and is usually included in the nomenclature of the compressor.
The number of pneumatic tools that can be operated at one time from an air compressor depends on the air requirements of each tool; for example, a 55-pound class rock drill requires 95 cfm of air at 80 psi. A 210-cfm compressor can supply air to operate two of the drills, because their combined requirements is 190 cfm.
However, if a third such drill is added to the compressor, the combined demand is 285 cfm, and this condition overloads the compressor and the tools and results in serious wear.
How air compressors work - Video:
How Air Compressor Work - Video: