Liquid ring vacuum pumps are in class of positive displacement pumps. Using the expansion and reduction principle in the cell of impeller blade, they vacuum the gases with a liquid ring. If the appropriate liquid is selected (generally water) all the gases and vapors are moved.
For a liquid ring vacuum pump the final suction pressure is limited with the liquid ring evaporation pressure. During service liquid temperature is 15 ºC at the pump discharge vacuum pressure reaches 25 mmHg (33 mbar).
Liquid ring vacuum pumps have a wide application area in industry. Because of their working conditions are in liquid, they are useful for applications which include moisture like filtration, drying, refrigeration and distillation