Q9.
With reference to Crankshaft deflections:
(a) Explain why crankshaft deflections are taken.(4)
(b) Write a procedure for the taking of main engine crankshaft deflections.(8)
(c) Explain the action to be taken if some crankshaft deflection readings are outside acceptable limits.(4)
Reference Answer
### (a) Reasons for Taking Crankshaft Deflections (4 Marks) Crankshaft deflections are a critical diagnostic measurement taken as part of a planned maintenance schedule to assess the alignment of the main engine's crankshaft. The primary purposes are: 1. **To Verify Main Bearing Alignment**: The crankshaft is a long, heavy, and flexible component supported by several main bearings. The primary purpose of taking deflections is to check for wear or misalignment in these bearings. A worn-down, damaged, or improperly fitted bearing will no longer support its share of the crankshaft's weight, causing the shaft to bend. This bending is directly measured by the deflection gauge. 2. **To Prevent Fatigue Failure**: Misalignment induces significant alternating bending stresses in the crank webs and journals as the shaft rotates. These stresses, if left uncorrected, can lead to the initiation and propagation of fatigue cracks, ultimately resulting in a catastrophic failure of the crankshaft. Such a failure can cause immense secondary damage to the engine and poses a severe risk to the vessel and its crew.
Full answer on MeoMock — surveyor-grade reference answers for 7,000+ written exam questions.