Vacuum pumps and compressors are different types of devices, compressors are devices for obtaining pressure, and vacuum pumps are devices for obtaining vacuum, referred to as vacuum pumps, also referred to as vacuum-acquisition devices. Since vacuum technology involves pressures ranging from 103,125 Pa to 10-12 Pa, this period contains more than a dozen orders of magnitude. It is impossible to achieve this with only one vacuum pump in such a wide pressure range. To this end, various types of structures and various types of vacuum pumps have been manufactured using various principles. There are 3 major categories and dozens of structural forms. The liquid ring vacuum pump is a rotor with multiple blades that is eccentrically mounted in the pump casing. When the rotor rotates, the working medium liquid (usually water or oil) is thrown toward the pump casing and forms a liquid ring concentric with the pump casing.
The liquid ring forms a rotary variable capacity vacuum pump with the rotor blade with a change in volume cycle. The liquid ring pump can be divided into two types, water ring type and liquid ring type, depending on the working medium. The water ring type vacuum pump is the most common type of liquid ring type vacuum pump. The water ring vacuum pump is mainly used in the process of rough vacuum and large pumping amount. It has been widely used in the chemical, petroleum and light industry sectors. The advantages of the pump are: simple structure, easy manufacture, reliable operation, convenient use, high durability, and can extract corrosive gas, dust-containing gas and gas-water mixture. The temperature of the gas to be pumped is preferably -20 to 40 °C. The ultimate vacuum of a single-stage water ring pump can reach 92-98% (8000-2000Pa), the ultimate vacuum of a two-stage water ring pump can reach 99.9% (100Pa), and the displacement is 0.25-500m3/h. Since the saturated vapor pressure of the oil is higher than that of water, the single-stage and two-stage oil ring pumps are more than one order of magnitude higher than the ultimate vacuum of the same type of water ring pump. At present, the main models of domestic water ring pumps are SZ type, SZB type, SZH type, SZZ type and SZ type, SK type, 2BEl type. The 2BEl water ring vacuum pump is an energy-saving product developed by the German company Siemens. A single-stage single-acting structure is adopted.
