Shaft alignment is the process of positioning two or more rotating shafts so their centerlines are aligned when machines are operating normally. Misalignment can cause damage like abnormal bearing wear. There are several methods to check alignment including using a piano wire or line-of-sight with a telescope. For a piano wire method, the wire is tensioned and distances from it to bearings are measured. For a telescopic method, targets are mounted on stationary points and the telescope is used to align the rotating components by sighting through the targets. Proper shaft alignment is important for reducing vibrations and extending component life.

2. Shaft alignment is process of position two or
more shafts that centre lines of rotating shafts,
form a single line when the machines are
working at normal. It is aligned to be given
reasonable bearing reactions & bending
moments at all conditions of ship loading &
operation.

4. •Destruction or abnormal wear of the stern bearings of
the shafting or of reduction gear bearings or of main
engine bearings.
•Destruction of the bronze sleeve of the propeller
shaft.
•Cracking or rupture of the propeller shaft or of the
crankshaft.
•Natural vibrations of the shafting or of its supports.

6. • Pilgrim wire
• Line of sight (telescopic)
• Gap & offset

8. If the misaligned shafts center lines are
parallel but not coincident, the misalignment
is called axial misalignment

9. If the misaligned shafts meet at a point but are
not parallel, then the misalignment is called
angular or radial misalignment.

11. A wire is used as a reference line. The
wire is tensioned to standard amount
by fixing at one end and having a
weight over a pulley at the other end.
Then distance from wire to bearings
are measured, allowance being made
for sagging of the wire.

13. The piano wire is centered to the after
end of stern tube outer bush by using
inside micrometer or caliper. For that
we should calculate the sag at that
point. There is a method to calculate the
sag

14. G
y
x
L
L - length of wire (fixed end to end) (m)
G - hanging weight (kg) = 30kg
P - wire weight per meter length (kg/m) =0.002kg/m
y - sag at given length (m)
x - distance (m)
Wire sag calculation
Y =P x X(L – X)/2G

15. The bushes can be machined on either the internal diameter or
the external diameter depends on the material of construction
and availability of machining margin. The bushes shown
below include one where the center line of the shafting and the
bush match, while the other one shows the bearing material
machined eccentrically to achieve concentricity between shaft
line and the bush center.

17. The telescopic alignment commonly used for
intermediate shaft alignment & crank shaft
alignment .because it is accurate more than
piano wire alignment & easy to do.
Any type of alignments are wanted two fixed
center . In this alignment I get outer bush aft
end & inner bush forward end as the fixed
point. It is depend upon our requirement &
placed.

18. • The glass target is mounted concentrically with stern tube inner bush
forward end.
• The telescope is mounted at outer bush after end using bore fixture.
• The telescope focus is adjusted & centered to center of target in
inner bush.
• Another target is arranged to locate on the gear box coupling & gear
box fwd end
• The telescope is focused to target at gear box coupling.
• Then ,
X – the gear box is adjusted from base with adjusting screw &
center line of sight.
Y – reconfirm that line of sight is passing through stern tube inner
bush target.
• The telescope is focused to gear box forward end & the above steps
are repeated.
• Until both end position comes to the line of sight.