Multistage shaft sealing apparatus

摘要

A plurality of seal units are provided between a seal housing and a rotating shaft. An inside seal unit, an outside seal unit, and at least one pair of intermediate seal units are aligned in an axial direction. The inside seal unit contacts fluid to be sealed. The outside seal unit contacts the atmosphere. The intermediate seal units are located between the inside seal unit and the outside seal unit. A plurality of chambers are defined by each of seal units. An intermediate liquid is supplied to the chambers. A pressure in an inside chamber is maintained lower than a pressure of the fluid to be sealed in a machine. Pressures in second and third chambers are maintained equal to or higher than the pressure of the fluid to be sealed.