US Patent 8061984 Dry gas blow down seal

A sealing assembly configured to seal a rotating shaft of a turbo machine having a high pressure process gas, comprising a housing defining a bore configured to receive the rotating shaft and sealing assembly, wherein the housing is mounted to a casing of the turbo machine; a first sealing stage comprising a single dry gas seal and configured to blow down the high pressure process gas to a lower pressure; a labyrinth seal mounted longitudinally outward from the first sealing stage; and a second sealing stage mounted longitudinally outward from the labyrinth seal, wherein the second sealing stage comprises a tandem dry gas seal having a primary dry gas seal and a secondary dry gas seal axially spaced with an intermediate labyrinth seal.