A liquid ring pump is a rotating positive displacement pump. They are typicallyused as a vacuum pump but can also be used as a gas compressor.The function of a liquid ring pump is similar to a rotary vane pump the differencebeing that the vanes are an integral part of the rotor and churn a rotating ring ofliquid to form the compression chamber seal. They are an inherently low frictiondesign, with the rotor being the only moving part. Sliding friction is limited tothe shaft seals. Liquid ring pumps are typically powered by an induction motor.