Exam Question

### (a) Importance of Taking Crank Web Deflections
Taking crank web deflections is a critical diagnostic and preventative maintenance procedure for any reciprocating engine, including auxiliary engines. Its primary importance lies in monitoring the alignment of the crankshaft's main bearings.
1. **Detection of Bearing Wear**: The deflection readings provide a direct indication of main bearing wear. As a bearing wears down, it allows the crankshaft to sag at that journal, causing the crank webs of the adjacent units to either spread apart or close in as the shaft rotates. Early detection allows for planned maintenance before a catastrophic failure.
2. **Prevention of Crankshaft Fatigue Failure**: A misaligned crankshaft is subjected to significant alternating bending stresses with every revolution. These stresses, concentrated at the fillets of the journals and webs, can lead to fatigue crack initiation and eventual fracture of the crankshaft, which is an extremely serious and costly failure.