Operating Principle and Options: The series SYF roots vacuum pump is with overflow valve. The figure-of-eight rotors are counter-rotating at a constant speed inside the pump housing for suction and exhaust of gas. Two rotors are supported by two bearings and synchronized by a gear, which assures these two rotors in selected relative positions. They are really close to to each other and also to the housing without actual contacting, so lubrication is unnecessary in the functioning housing. The thoroughly balanced working components and high precision bevel wheels ensue the pump be operated stably and continuously below the ailment of high-pressure difference. Dynamic seal component utilizes our patent technological innovation and imported oil seals, the vibration amount of shaft to the shaft seals is managed to less than 0.02mm. A gravity valve is set up amongst the suction and exhaust part of the pump. The perform of the gravity valve is as follows, once the strain distinction concerning the suction and exhaust part is over the excess weight of the valve, the valve opens immediately, which makes the stress big difference often retain in a fixed controllable value, the value may be the allowable highest stress difference to ensure the pump operate generally and so that in reality, the roots vacuum pump with overflow valve is often a form of overload self-protective pump. Series SYF roots vacuum pump with overflow valve has considerably greater speed at fairly lower inlet pressure and it is actually possessed overload self-protective function. Because it can be a pump of dry clearance seal construction, if a certain pumping pace rate 15 and an ultimate vacuum need to be obtained, it truly is necessary to provide a reduced inlet pressure for reducing the back flow, consequently, a pump must be backed in use, roots vacuum pump needs to be commenced soon following its inlet pressure reaches a permissible value for economization. It truly is allow to pick distinct varieties of pump because the backing pump for factual prerequisites, such as oil seal pump and liquid ring vacuum pump. When pumping the gasoline containing big amount of vapor, the liquid ring vacuum pump is the best backing pump.