Liquid ring vacuum pumps are used in remediation applications requiring very high levels of vacuum. The pump consists of a vaned impeller rotating within an eccentric pump casing. The casing is partially filled with a seal fluid, usually water or oil. The rotating impeller forces the seal fluid to the outside of the casing, forming a “liquid ring”. The spaces formed between the seal fluid and the vanes are individual compression chambers. Due to the eccentricity of the impeller relative to the casing, each compression chamber is a different size. As each vane on the impeller passes the pump inlet, air is drawn into a compression chamber. Then the rotation of that chamber into deeper seal fluid causes the air to be compressed. At the maximum compression (i.e. deepest seal fluid and smallest compression chamber) the air is expelled through the outlet of the pump. As the chamber rotates back to the pump inlet, the seal fluid becomes shallower and the chamber expands, allowing air to be drawn in again at the inlet. The compression of air within the pump casing allows the pump to achieve higher levels of vacuum than other positive-displacement vacuum pumps, like rotary lobe blowers.
One of the issues with liquid ring pumps, however, is that some seal fluid is expelled along with the air through the pump outlet. This seal fluid must be separated from the air, using some form of separator vessel, and either cooled and recirculated to the pump (oil or water), or discharged and replaced with new fluid (water).
As mentioned, liquid-ring vacuum pumps can achieve very high vacuum, as well as high air flow rates. When selecting a liquid ring pump, the required flow rate and vacuum are the most important factors, and the electrical classification of the motor should also be considered.
MLE Equipment uses liquid ring vacuum pumps manufactured by Dekker Vacuum; in the majority of cases oil is employed as a seal fluid, as oil is better at absorbing heat from compression and rotational forces, and eliminates the threat of corrosion. Please see the provided specification sheets and manuals for more detailed information on liquid-ring vacuum pumps.
