• To check whether the alignment is acceptable, the crankshaft deflection readings are taken.
• From that reading, the deflections in the vertical and horizontal planes are obtained by calculation.
• The calculated figures are compared with the maximum allowable figures from the maker instruction book.
• In many engines the allowable deflection in the horizontal plane is the same as that allowed in the vertical plane, whilst in others the allowables are different.

• Wear of main bearing lower shell
• Wear and ovality of main journal pin
• Wear foundation chocks
• Distortion of engine bedplate
• Distortion of supporting ship’s structure
• Improperly loaded condition of the vessel
• Lifting of flywheel side

Effects of misalignment:­

• Bending of crankshaft
• Fatigue failure owing to cyclic stresses
• Undue vibrations within the engine
• Damage to the main bearing

(c) The deflection measurements are recorded as follows:

• Place a spring-loaded dial gauge in between the crank webs opposite the crankpin.
• The crank to be measured is turned towards BDC with the dial gauge as close as possible to the connecting rod and the gauge is set to zero.
• Turn the crankshaft ahead and record the values in both horizontal crankpin positions and at TDC.
• Turn the crankshaft until the gauge is as close as possible to the connecting rod on the other side and record the value at this position.
• The difference between the value at BDC and TDC indicated the amount of alignment during one revolution.