Patent ID: 7014192
Filing Date: 2006-03-21
Classification: F16J

Abstract:
1. A multistage shaft sealing apparatus comprising: a seal housing having an inner circumferential surface; a rotating shaft rotatably mounted and passing through an inside of the seal housing; an inside seal unit having a sealed slide surface portion and being provided at a side of fluid to be sealed in a machine; an outside seal unit having a sealed slide surface portion and being provided at a side of atmosphere, the inside seal unit and the outside seal unit being bounded between the seal housing and the rotating shaft; a plurality of intermediate seal units having a sealed slide surface portion and being located between the inside and the outside seal units; an intermediate liquid supply passage for supplying intermediate liquid in plural chambers including first, second and third chambers, which are bounded by the inside seal unit, the outside seal unit and the intermediate seal units; an intermediate liquid discharge passage for discharging the intermediate liquid from the chambers; and a plurality of plugs fixed at the inner circumferential surface of the seal housing, each of the plurality of plugs having an annular baffle plate integrally formed at an end of the plugs and protruding inwardly towards the rotating shaft for detouring the intermediate liquid so as to flow near the sealed slide surface portions in such a manner that the sealed slide surface portions are cooled and lubricated by the intermediate liquid; wherein pressures from a process liquid in the machine to the atmosphere at the outside of the machine are controlled by circulation and supply of the intermediate liquid, in such a manner that an internal pressure in the first chamber is maintained lower than a pressure of the process liquid in the machine, and an internal pressure in the second chamber is maintained higher than the pressure of the process liquid in the machine, and an internal pressure of the third chamber is maintained lower than the internal pressure in the second chamber and higher than the internal pressure of the process liquid.