Operating Principle and Functions: The series SYF roots vacuum pump is with overflow valve. The figure-of-eight rotors are counter-rotating at a continual velocity within the pump housing for suction and exhaust of fuel. Two rotors are supported by two bearings and synchronized by a gear, which guarantees these two rotors in specified relative positions. They are near to each other and also to the housing without having actual contacting, so lubrication is unnecessary within the working housing. The cautiously balanced operating elements and high precision bevel wheels ensue the pump be operated stably and constantly underneath the ailment of high-pressure difference. Dynamic seal component utilizes our patent technology and imported oil seals, the vibration level of shaft over the shaft seals is managed to much less than 0.02mm. A gravity valve is installed between the suction and exhaust a part of the pump. The function from the gravity valve is as follows, when the stress difference in between the suction and exhaust part is in excess of the excess weight with the valve, the valve opens instantly, which tends to make the strain difference normally keep within a fixed controllable value, the value is the allowable highest stress distinction to guarantee the pump function commonly and in order that the truth is, the roots vacuum pump with overflow valve is often a kind of overload self-protective pump. Series SYF roots vacuum pump with overflow valve has substantially increased pace at somewhat lower inlet pressure and it truly is possessed overload self-protective perform. Because it is often a pump of dry clearance seal development, if a specific pumping velocity price 15 and an greatest vacuum must be obtained, it truly is needed to supply a lower inlet stress for cutting down the back flow, therefore, a pump has to be backed in use, roots vacuum pump must be commenced soon just after its inlet pressure reaches a permissible value for economization. It can be permit to select distinctive sorts of pump because the backing pump for factual necessities, this kind of as oil seal pump and liquid ring vacuum pump. When pumping the gasoline containing massive amount of vapor, the liquid ring vacuum pump is the excellent backing pump.