Working Principle and Capabilities: The series SYF roots vacuum pump is with overflow valve. The figure-of-eight rotors are counter-rotating at a continuous velocity inside the pump housing for suction and exhaust of gas. Two rotors are supported by two bearings and synchronized by a gear, which ensures these two rotors in selected relative positions. They’re near to each other and to the housing with out real contacting, so lubrication is needless from the operating housing. The thoroughly balanced operating components and substantial precision bevel wheels ensue the pump be operated stably and constantly underneath the issue of high-pressure big difference. Dynamic seal component employs our patent technological innovation and imported oil seals, the vibration volume of shaft around the shaft seals is controlled to much less than 0.02mm. A gravity valve is put in among the suction and exhaust a part of the pump. The function with the gravity valve is as follows, once the pressure distinction among the suction and exhaust portion is in excess of the fat from the valve, the valve opens immediately, which can make the stress big difference constantly preserve in a fixed controllable value, the value will be the allowable highest pressure difference to guarantee the pump work generally and to ensure in truth, the roots vacuum pump with overflow valve is a type of overload self-protective pump. Series SYF roots vacuum pump with overflow valve has substantially higher pace at rather reduced inlet stress and it is possessed overload self-protective function. Since it is a pump of dry clearance seal construction, if a particular pumping pace rate 15 and an ultimate vacuum need to be obtained, it can be essential to provide a reduced inlet pressure for cutting down the back flow, hence, a pump must be backed in use, roots vacuum pump must be started soon after its inlet stress reaches a permissible value for economization. It is actually permit to pick diverse types of pump since the backing pump for factual requirements, such as oil seal pump and liquid ring vacuum pump. When pumping the fuel containing massive level of vapor, the liquid ring vacuum pump will be the ideal backing pump.