The seawater flush system is designed to have
Face to seal contact pressure is maintained by
a seawater flush of 15 gpm and 20 psi. A vent line
the force of the springs, which is developed in the
is also provided to allow passage of any air
bellows seal assembly, and by the hydraulic forces
trapped in the stern tube and seal housing to the
induced onto the components of the seals by the
atmosphere.
seawater being sealed. This combination of spring
Two backup sealing systems have been
and hydraulic forces maintains a consistent face
incorporated into the stern tube seal; the inflatable
contact pressure and consistent seal leakage
seal and a conventional stuffing box.
despite seal wear.
The inflatable seal is an elastomer channel
The bellows assembly is the flexible member
incorporated into the mounting ring, When the
of the seal allowing the seal to accommodate
inflatable seal is subject to air pressure, it expands
shaft or hull movements caused by thermal
and seals the radial gap between the stern shaft
differences, thrust loads, vibration, and bearing
and the seal housing. This allows the seal to be
tolerances.
Figure 8-31.--Stern tube piping diagram (typical).
8-48
