Therefore, the water ring pump unit can be widely used in vacuum distillation, vacuum evaporation, dehydration crystallization, etc. in the chemical industry; freeze drying in the food industry; vacuum drying in the pharmaceutical industry; polyester chips in the textile industry; and vacuum systems for high-altitude simulation tests, etc.
Water ring vacuum units can be roughly divided into the following types:
Water ring pump: The main function of the water ring pump in the unit is to create the preliminary vacuum required by the Roots pump. Generally speaking, the ultimate vacuum of a single-stage water ring pump is not high, and the pre-vacuum required by Roots pumps currently produced in China is relatively high. Therefore, in practice, we usually do not use a single-stage water ring pump as the backing pump for a Roots pump, but instead use a two-stage water ring pump with lower ultimate pressure as the backing pump, which can also reduce the ultimate pressure of the unit.
The ultimate pressure of a pump combined with a water ring pump is 400Pa, which can meet general vacuum requirements, but its range of use is somewhat limited. If two Roots pumps are connected in series and then combined with a water ring pump, the ultimate pressure of the unit can be greatly improved (reaching 25Pa). Therefore, in this type, it is common to see two Roots pumps in series followed by a two-stage pump as the backing pump to form a unit. If a higher ultimate pressure is needed, three Roots pumps can be combined with a water ring pump, achieving an ultimate pressure of 1Pa.
If the three-stage water ring unit still cannot meet the ultimate pressure requirement, we can use a water ring pump in parallel with a mechanical vacuum pump. This unit is mainly used for vacuum systems that need to handle large amounts of water vapor, have long durations, and require very high ultimate vacuum, such as in vacuum drying.
In vacuum systems that require handling large amounts of water vapor, using a water ring pump is more appropriate, but because its ultimate vacuum is not high, the overall ultimate vacuum of the unit is relatively low (this is only relative). In vacuum systems requiring higher vacuum, a mechanical vacuum pump with higher ultimate vacuum is needed as the backing pump. A gas ballast mechanical vacuum pump can be connected in parallel with a water ring pump as the backing pump for the pump. During vacuum drying, first use the water ring pump for pre-evacuation until the water vapor is greatly reduced, then start the gas ballast mechanical vacuum pump and cut off the water ring pump. In cases where drying takes a long time, the required cooling water and power are relatively small.
