Structure and Features
Roots pump is used as main chief pumps, double-stage liquid ring vacuum pump is as backing pump. They are connected in series. The roots pump and liquid pump can be started and closed automatically by vacuum relay or electric tactility pressure gauge. Possess overload self-protective function
It has many virtues as follow compared with the ordinary Roots pump and liquid ring vacuum pumps

1. The system can pump ordinary gas, which possesses particles of dust, vapour, because water ring vacuum pump is as backing pump. It can be used in bad environment.
2. If multilevel roots pumps are connected in series, the ultimate pressure of approximate is increased 1pa.
3. In a quite wide pressure range (50Pa to 4000Pa) a stable, fairly high pumping speed can be gained
4. Low power compare with multilevel
   

These can be combined as follow according as different useful request
1. A roots pump systems with double stage liquid ring vacuum pump
2. Two roots pump systems with double stage liquid ring vacuum pump
3. Three roots pump systems with double stage liquid ring vacuum pump
Use:
The vacuum system is suitable for high vacuum distilling, vacuum vaporizing and vacuum dehydrating-crystal of chemical and medicine industry, vacuum drying and vacuum soaking of electric utility and light textile industry, freeze-dryer of food industry etc.