What is a blowers "Slip"? :
Each rotor of a Roots type blower turns at an equal speed but in the opposite direction to the other. This is achieved by using a pair of equal ratio gears to drive the rotors. Using this type of configuration, blowers can run without internal lubrication to the rotors, as they never come into contact with either the outer casing or each other, thus air is delivered completely oil free.
As the rotors turn, air is drawn into the inlet side of the blower and travels around the outer casing of the machine in the pockets between each lobe of the rotor. Once at the discharge side of the blower the air is forced out and stopped from passing back into the chamber by the finite clearances between all of its’ internal components. The tiny amount of air that does manage to pass back through these minute clearances is what is known as blower “Slip”. The greater the difference between the inlet pressure (normally below atmospheric pressure) and discharge pressure (normally above atmospheric pressure), the higher the level of slip will be.
The higher the temperature of the gas being handled, the higher the level of slip due to the decrease in the density of the gas allowing it to more easily pass through the small fixed internal blower clearances
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