A Liquid-Ring Vacuum Pump liquid ring vacuum pump is easy to operate and is utilized in several applications across various industries. A liquid band pump works with a sealant needed in its operation. This liquid could be water, oil or any other solvent which is usually rotated by an impeller within the casing of the pump.
As the shaft turns, a liquid ring is established by the centrifugal force generated by the rotating impeller. This power holds the liquid ring against the inner wall of the pumping chamber. Since the impeller is situated eccentric to the pumping chamber, the 
depth of entry of the blades into the liquid ring decreases and boosts as the impeller rotates. This creates increasing cell volume on the inlet port side, creating vacuum.
On the discharge interface side, the impeller cell volume decreases as the blades move further into the liquid band. This increases the pressure until discharge takes place through the discharge interface.
A continuous flow of fresh sealing liquid is supplied to the pump via the sealing-liquid inlet.
Regarding the two-stage liquid ring pump, the discharge from the first stage does not discharge to atmosphere. Rather, the 1st stage discharges through the manifold resulting in the second stage and also through a discharge interface positioned in the intermediate plate between your first- and second-stage impellers.