Screw Vacuum Pump: A rotary screw pump has become the earliest designed favourable displacement pumps which was referred to as the Archimedes‘ screw. In its easiest form, this pump includes an individual screw inside of a hollow cylinder. Contemporary types integrate double or triple screws meshing against each other. 4 https://rackingmanufacturing7.techionblog.com/26883912/a-secret-weapon-for-air-compressors