| 主权项 |
1. An internally pressurized seal assembly in combination with a housing and a shaft, the seal assembly providing a seal between the shaft and the housing, the housing defining a relatively lower pressure process chamber in which a relatively lower pressure process fluid is contained, the internally pressurized seal assembly being mounted between concentric surfaces of the shaft and the housing, the internally pressurized seal assembly comprising:
an inboard side that is adjacent the relatively lower pressure process chamber and an outboard side that is remote from the relatively lower pressure process chamber, the inboard and the outboard sides of the seal assembly being axially opposite one another; a first seal ring being fixed to a flange of a sleeve member which is supported by the shaft and the first seal ring being sealed with respect to the shaft, and the first seal ring having an annular sealing surface that extends radially and faces the outboard side of the first seal ring, the first seal ring having an inner surface that is radially spaced from the sleeve member; a second seal ring being fixed to a carrier ring and sealed with respect to the housing, the second seal ring being located on the outboard side of the first seal ring and having an annular sealing surface that extends radially and faces the first seal ring which is located on the inboard side of the second seal ring, the second seal ring having an inner surface that is radially spaced from the sleeve member, and the inner surfaces of the first and the second seal rings and the sleeve member defining a relatively higher pressure gap, outer surfaces of the first and the second seal rings being radially spaced from an inner surface of the housing defining a relatively lower pressure process chamber extension that is open to the relative lower pressure process chamber; a resilient means located between one of the first seal ring and the housing, and the second seal ring and the shaft to urge said one of the first and the second seal rings axially towards the other of the first and the second seal rings such that the annular sealing surface of the first seal ring sealingly engages the annular sealing surface of the second seal ring to form a seal between the annular sealing surfaces of the first and the second seal rings and prevent leakage of the relatively lower pressure process fluid in the relatively lower pressure process chamber extension radially inwardly to the relatively higher pressure gap defined between the inner surfaces of the first and the second seal rings and the sleeve member; an inlet being located on an outboard side of the second seal ring communicates with the relatively higher pressure gap, the inlet being connected to a source of barrier fluid at a pressure in excess of the pressure of the process fluid in the relatively lower pressure process chamber, such that a relatively higher pressure barrier fluid is introduced into the relatively higher pressure gap to communicate with inner surfaces of the first and the second seal rings, the relatively lower pressure process fluid and the relatively higher pressure barrier fluid cooperating with one another so as to only permit the relatively higher pressure barrier fluid to flow radially outwardly from the relatively higher pressure gap past the first and the second seal rings and into the relatively lower pressure process chamber and the process chamber extension and prevent leakage of the relatively lower pressure process fluid radially inwardly to the relatively higher pressure gap; a thermal shroud member is supported by the flange of the sleeve member and extends axially toward the outboard side of the first seal ring and another thermal shroud member is supported by the carrier ring and extends axially toward the inboard side of the second seal ring, axially adjacent ends of the shroud members have flange formations, the flange formations extend radially inward from the respective shroud member toward the respective outer surface of the first and the second seal rings, the shroud members restricting communication between the relatively lower pressure process fluid in the relatively lower pressure process chamber extension and the outer surfaces of the first and the second seal rings to adjacent the annular sealing surfaces; and thermally insulative sleeves being secured to the respective inner surfaces of the first and the second seal rings so as to shield the inner surfaces of the first and the second seal rings from communicating with the relatively higher pressure barrier fluid, the thermally insulative sleeves being spaced from the sleeve member. |
