Dry screw pumps are increasingly popular as an alternative to oil-sealed rotary vane pumps for many medium and high vacuum applications. Vacuum furnaces end-users and designers must have a good understanding of how claw and screw pumps operate. This includes the principles of operation and operating characteristics, pump design and features, sealing, purging, and ancillary devices. A dry screw pump is used alone when a high vacuum is not required. When used in series with other pumps, this primary pump is also referred to as a “backing” pump.
An Excerpt:
“Screw pumps operate using two counter-rotating screw rotors which are engineered so that they rotate “towards each other”. This traps the gas in the space between the “screws” of their rotors. As the screws rotate, this trapped volume decreases which not only compresses the gas but moves it towards the exhaust.”
Source: Vacuum Science World
A screw pump is a famous type of the positive displacement pump. It is also called a water screw pump. A screw pump uses one or more screws to move fluids or water along the axis of the screw. These screws interlock to pressurize the fluid and move it inside the system. These screws are meshed with each other and reciprocate in the cavity of the cylinder.
In this pump, the water or other fluids enters into the pump through the inlet valve and flows linearly toward the outlet side of the pump along with the interlocking screws. The small gap between the screw and the cavity increases the fluid pressure when fluid flows through the pump.