A screw compressor works with a male and female rotor that rotate in the opposite direction. This movement draws in air that is compressed as the space between the rotors and their housing decreases. The compressed air is then displaced to the outlet.
[pdf] Try to turn the compressor by hand. It should be possible to turn it around. It should turn around smoothly, without any 'hickups' (be sure to completely shut down the air compressor!). Check the isolation of the motor windings.
[pdf] A is first thought to have been used for rock drilling in 1844. Many quarries used hand held tools that required the driller to suspend himself from a rope over the quarry face in order to place the drill hole in the required position. This system used small diameter holes and was not only terribly inefficient, but very dangerous due to flying rock as a result of the inaccuracy of the drilled borehole.
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