These are oil - immersed, rotaryvane type pumps. The rotor with two spring loaded vanes is mounted eccentric inthe stator body. As the rotor rotates, the vanes sweep the crescent shape airspace twice in each revolution. There is inbuilt non-return valve whichprevents back flow of air. All moving parts are manufactured from gradedmaterial. These parts are precisely machined, ground and assembled with closetolerances which results in increased efficiency and long trouble freeoperating life.