As the name liquid ring vacuum pump suggests, this type of pump features a liquid ring. There is no mechanical contact between the pump's moving parts. The liquid acts as small pistons, in much the same way as a traditional piston pump. As a result, the pump also develops very little heat and it is possible to achieve a deep vacuum.
When the pump starts, the liquid ring rotates at the same speed as the rotor. The rotor is slightly offset from the centre and the liquid ring features an array of small cells. A cell in the uppermost position is completely filled with water. As the cell turns, a pocket of air is created at the rotor hub.
The liquid acts as a piston as it moves away from the rotor hub to create a suction effect. As the cell passes the bottom of the chamber, the liquid begins pressing in towards the rotor hub. This causes the air to be forced out of the cell, filling it with liquid ready for the next suction cycle.
To separate the suction and compression parts of the pump, the ends of the casing are fitted with a flow plates and pump housing. Some pump types feature connections at both ends, while others (monoblock pumps) only have one at one end of the liquid ring.