LRVP---Water ring vacuum pump

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This post was last edited by Black gold on 2011-11-8 at 19:49. The water ring vacuum pump (abbreviated as water ring pump) is a type of rough vacuum pump; the ultimate vacuum it can achieve is between 2000 and 4000 Pa, and with an atmospheric ejector in series, this value can reach 270 to 670 Pa. Water ring pumps can also be used as compressors, known as water ring compressors; they are low-pressure compressors with a pressure range of 1~2×105 Pa gauge pressure. 　　Water ring pumps were initially used as self-priming pumps, and later came to be employed in many industrial sectors such as petroleum, chemicals, machinery, mining, light industry, pharmaceuticals, and food processing. Water ring pumps are widely used in many industrial processing steps, such as vacuum filtration, vacuum water pumping, vacuum feeding, vacuum evaporation, vacuum concentration, vacuum rehumidification, and vacuum degassing. Due to the rapid advancement of vacuum application technology, water ring pumps have always been highly regarded for achieving rough vacuums. Since the gas compression in a water ring pump is isothermal, it can be used to pump flammable and explosive gases, as well as gases containing dust or moisture; therefore, water ring pumps are being used more and more frequently. As shown in the figure: an appropriate amount of water is placed inside the pump body as the working fluid. As the impeller rotates clockwise as shown in the diagram, water is thrown outward by the impeller; due to centrifugal force, the water forms a closed ring of approximately uniform thickness, shaped according to the geometry of the pump chamber. The inner surface of the lower part of the water ring is in exact tangency with the impeller hub, while the inner surface of the upper part of the water ring is in contact with the tips of the blades (in fact, the blades extend to a certain depth within the water ring). At this point, a crescent-shaped space is formed between the impeller hub and the water ring, and this space is further divided by the impeller into several small chambers, one for each blade. If 0° at the lower part of the impeller is taken as the starting point, then when the impeller has rotated 180°, the volume of the small chamber increases and it becomes connected to the suction port on the end face; at this point, gas is drawn in. Once suction is complete, the small chamber becomes separated from the suction port ； As the impeller continues to rotate, the small chamber becomes smaller, causing the gas to be compressed ； When the small chamber is connected to the exhaust port, the gas is expelled outside the pump. 　　In summary, a water ring pump relies on changes in the volume of its pumping chamber to achieve suction, compression, and exhaust, and therefore it belongs to the category of variable-volume vacuum pumps. Compared to other types of mechanical vacuum pumps, water ring pumps have the following advantages: they have a simple structure, require low precision in manufacturing, and are easy to process. It has a compact structure, with a high rotation speed; it can generally be connected directly to the motor without the need for a reduction gear. Therefore, a small structural size can yield a large displacement, while also requiring less floor space. Compressed gas is essentially isothermal, meaning that the temperature changes very little during the compression process. Since there are no metal friction surfaces inside the pump chamber, there is no need for lubrication within the pump, and wear is minimal. The sealing between the rotating part and the fixed part can be achieved directly by a water seal. It features even air intake, stable and reliable operation, simple handling, and easy maintenance. Water ring pumps also have their disadvantages: they have low efficiency, generally around 30%, with better models achieving up to 50%. The low vacuum level is due not only to structural constraints but, more importantly, to the saturated vapor pressure of the working fluid. Using water as the working fluid, the ultimate pressure can only reach 2000~4000 Pa. Using oil as the working fluid, a pressure of 130 Pa can be achieved. 　　In short, since the gas compression in a water ring pump is isothermal, it is possible to pump out flammable and explosive gases. Due to the absence of exhaust valves and friction surfaces, it is possible to extract dusty gases, condensable gases, and gas-water mixtures. Thanks to these prominent features, it is still widely used despite its low efficiency