The definition of a dried out vacuum pump is a pump that will not use any fluids to make a vacuum or contact the process gas and can also discharge to atmosphere. … Timing gears with oil reservoirs and close clearances between the rotors and casing are extra attributes that define a dry vacuum pump.

Principle of Operation

Dry screw vacuum pumps operate with two screw rotors rotating in opposite directions. This traps the moderate to be pumped between the cylinder and the screw chambers and transports it to the gas discharge. … It also results in a lower heat load of the compressed gas.