The JZJ series Roots Water Ring Vacuum Pumps are composed of a Roots pump as the main pump and a water ring pump as the preliminary pump in series. Using a water ring pump as the preliminary pump in the Roots Water Ring Vacuum Pumps is more advantageous than other vacuum pumps, as it overcomes the drawback of low gas extraction rate at a certain pressure, which is a limitation of a single water ring pump (the pump's ultimate pressure difference is significantly higher than that of the water ring pump). It also retains the advantages of the Roots pump, which can operate quickly and has a high gas extraction rate. It is particularly suitable for extracting large amounts of condensable steam, especially when the mechanical vacuum pump equipped with a gas seal is insufficient in removing condensable steam, or when the solvent used can degrade the pump oil and affect performance, or when the vacuum system does not allow oil contamination. With explosion-proof motors and electrical equipment, and under compliance with the relevant safety regulations, it can also extract flammable and explosive gases. Therefore, the Roots pump-water ring pump unit is widely used in vacuum distillation, vacuum evaporation, and dehydration crystallization in the chemical industry; freeze-drying in the food industry; vacuum drying in the pharmaceutical industry; polyester chips in the light textile industry; and vacuum extraction systems for high-altitude simulation experiments, etc.