Rotary vane: Rotary vane pumps are comprised of a series of vanes that are mounted to a rotor that turns in the cavity. As the vanes rotate, centrifugal drive extends them from their individual slots, forming compression cells that get bigger to draw surroundings in from the intake and smaller to push air out the exhaust.
Articulated piston: An articulated piston commercial vacuum pump works in a way similar compared to that of a car engine. As the 
piston moves downward in the cylinder, air flow is drawn in through the intake valve. During the piston’s upward stroke, the air flow is permitted to escape via an exhaust valve. Two spring-backed piston rings are accustomed to seal the piston to the cylinder.
Screw: Rotary screw pumnps include two parallel rotary screws in the pump casing. The screws are synchronized to turn in reverse directions, which in turn causes the compression action that occurs. The gas is usually compressed in Industrial Vacuum Pumps direction of the pump’s discharge port.
Liquid ring: Liquid ring pumps also operate via positive displacement. During operation, the pump’s impeller rotates inside the pump casing. A rotating liquid ring after that seals the impeller and its blades. Liquid is usually sucked in to the compression chamber to keep the ring steady. Conveyed gas can be compressed during each impeller revolution.
Claw: Claw vacuum pumps contain two rotors that are extremely close but do not come in contact with each other during rotation. As the rotors switch they actually enlarge the space between them to attract air, then as they rotate around, actually reduce the space between them to compress the atmosphere from the chamber.