Multi-stage rotary vacuum pump used for high temperature gas

A multiple-stage rotary dry type vacuum pump comprising a plurality of pump sections including shafts supported by bearings on both driving and gear sides, a rotor fixed to the shaft, a pair of gears at ends of the shaft for synchronously driving a plurality of the rotors, oil vessels for reserving lubrication oil in the pump sections, and a housing with a suction inlet and an exhaust outlet, the exhaust outlet of one pump section being communicated with the section inlet of the next pump section through a communication path, only vacuum pump handling gas being introduced into operation housings of the pump sections without introducing liquid thereto, a gas compressed in one pump section passing through the communication path into the next pump section to cause the gas to successively be compressed in the plurality of pump sections,

• wherein mechanical seals are arranged in the sides of said pump housing adjacent to said bearings, an oil pump for lubrication oil for the bearings is arranged for supplying lubrication oil to the bearings, the oil pump is communicated with the oil vessel, the discharge opening of the oil pump is communicated with an oil supply pipe connected to the supporting bodies of the mechanical seals so that lubrication oil passes through the supporting bodies of the mechanical seals, and a return oil piping is arranged for returning the lubrication oil.