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 TM 55-1905-221-14-3
6-16
PROPELLER, PROPELLER SHAFT, AND STUFFING BOX (Continued)
LOCATION/ITEM
ACTION
REMARKS
ALIGNMENT
22. Propeller
a. Alignment of shaft and
Shaft
bearings is not permanently
fixed. The alignment
changes with every docking
due to changes in the keel
blocking, temperature
variations, and the direc-
tion of the sun's rays
relative to the fore and aft
line of the vessel. The
alignment of shafting and
bearings is affected by the
temporary removal of machinery
attached to the shafting or
in the vicinity of the
shafting because of the
redistribution of weights
and stresses. The alignment
is not the same when the
vessel is waterborne as when
it is in drydock. The final
alignment and bolting of the
main propulsion shafting
should always be done when
the vessel is waterborne.
b. The primary purpose for
providing correct alignment
is to eliminate shaft
excited vibrations and to
prevent an excessive pressure
upon any localized portion
of the shafting bearing
surfaces (journal bearing
areas). The longitudinal
line connecting the lowest
extremities of all shafting
journals having the same
diameter should form a
continuous-faired line when
the machinery is at operating
temperature. When the
shafting is correctly aligned
6-190
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