Propeller Shaft Aligement

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 at all conditions of ship loading & operation.

Offset Angular

Offset, or Parallel – the shafts are parallel to each other, but are not co-planar, or in the same plane. This can be both vertical and horizontal

Angular – the shafts are not in the same plane, which causes a difference in measurement between measurements made 180 degrees opposite on the coupling faces.

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 Natural vibrations of the shafting or of its supports.

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Destruction of the bronze sleeve of the propeller shaft.

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Cracking or rupture of the propeller shaft or of the crankshaft.

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Destruction or abnormal wear of the stern bearings of  the shafting or of reduction gear bearings or of main engine bearings.

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PROPELLER SHAFT ALIGNMENT METHOD

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PIANO WIRE METHOD

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.

Piano

cable sag calculation L (total length)

x Piano cable dia, (.50 mm)

Y sag 30 kg

W

Use

these formula & calculated sag,

W=Hanging weight(kg) L = total length(m) P= weight of the cable 1m length ( .002kg) X=distance to bearing center(m) Y= sag at given length(m) Sag(Y) =P*X(L-X) / (2w)

Attachment tool

Piano wire

plug

30kg(hanging weight) Intermediate shaft or fly wheel

 Alignment

attachment should be fitted (welded) at the after end of the stern tube (at outside)

Then

the plug is fitted to the center of the flywheel or to the center of the intermediate shaft.  After

that, one end of the piano wire is fitted to the plug and then the wire is driven through the attachment and desired weight is hanged at the other end. Piano

wire is aligned to the after end of the stern tube using inside micrometer. Then

the distance from the wire to the stern tube inside surface is measured on port, starboard, and top and bottom directions. This is done for several places of the stern tube.

These special tool set outer side of the stern tube ,it use to alignment piano

Procedure for alignment of  propeller shaft line using micro alignment telescope

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.

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The glass target is mounted concentrically with stern tube inner bush forward end.(B) The telescope is mounted at outer bush after end using bore fixture. (A) Two small lights are fixed behind that target. Then look through eye piece & telescope focus is adjusted & centered to center of target in inner bush. Then zero adjustment is done, using adjusting screw. After that the telescope is fixed. Another target is arranged to locate on the gear box coupling & gear box fwd end (C) After that focusing screw is used to focus the telescope to that target at gear box coupling. Vertical and horizontal adjusting screws are used to take that reading •

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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, gear box forward end & after end comes to the line of sight. 