A liquid ring vacuum pump comes with 
an impeller with blades attached to a center hub located in a cylindrical body but off-set from the center.
In Number 1 to the right, you can see the blades near the top of the pump are nearer to the exterior wall than at the sides and bottom level of the pump. You can observe this more obviously in Figure 2.
The impeller sits among two end Liquid-ring Vacuum Pumps plates (port plates) that have shaped holes cut into them called ports.
The pump requires a liquid (also known as the sealant) to create vacuum as follows. Prior to starting the pump, it should be partially filled with the liquid sealant. The liquid can be water (rendering it a water band pump), essential oil or a solvent, dependant on the application.