How to calculate misalignment of crankshaft in main engine? What may be the reasons of misalignment?

1. Make an enclosed space permit
2. Stop engine and allow to cool
3. Block the starting mechanism
4. Shut off starting air supply
5. Engage the turning gear
6. Open indicator cock ( because air will compress and give wrong reading on turning the engine)
7. Stop lubrication oil pump
8. Put tag “ Men at work”
9. Open crankcase and allow ventilation before entry
10. 
11. Closing of the crank throw (compression of the gauge) is regarded as negative and opening of the crank throw is regarded as positive.
12. 
13. 
14. The procedure is repeated for each unit and measurements are recorded.

Reasons of misalignment:

• Damage or wipe-out of the main bearing
• Loose engine foundation bolt leading to vibration
• Deformation of ship’s hull
• Crack in the bearing saddle
• Loose main bearing bolt leading to damage of main bearing
• Very high bending moment on the crankshaft due to excessive force from piston assembly
• Grounding of the ship Crankcase explosion or fire
• A defective or worn out stern tube or intermediate shaft bearings
• Loose or broken chokes in the foundation
• Bearing pockets cracked Bedplate deformed – transverse girder damaged
• Tie bolts slack or broken
• Weakening of structure due to corrosion