Patent ID: 6305691
Filing Date: 2001-10-23
Classification: F05D,F16J

Abstract:
A shaft sealing apparatus comprising a seal casing and a rotary shaft passing through the seal casing and having a mechanical seal and a dry gas seal mounted thereon in line with each other so as to seal a target sealing fluid area from an atmospheric area through a first and a second purge fluid area formed between said both seals with said first purge fluid area being located adjacent a sealing surface of said dry gas seal and said second purge fluid area being located adjacent a spring retainer side of said dry gas seal, wherein a purge fluid is supplied from an external supply line into said first purge fluid area and the supplied purge fluid is then released outside the apparatus from said purge fluid area through a relief line, wherein said dry gas seal includes a stationary-side seal ling and a rotation-side seal ring, either one of the rings includes a dynamic pressure-producing groove, said dry gas seal is driven in a state in which said dry gas seal faces are not in contact with each other, and the relief line is provided with an orifice, wherein a bypass line provided with an electromagnetic valve and a pressure switch is attached to said relief line so as to communicate with the latter and so as to bypass an orifice of said relief line, wherein said bypass line is for bypassing an orifice on the relief line, and the bypass line is provided with an electromagnetic valve and a pressure switch.