Q4
With reference to shaft alignment:
(a) Explain the meaning of fair curve or rational alignment.
(8)
(b) Shaft alignment is often verified using hydraulic jacks to obtain a simple graph. Sketch such a graph,indicating the following:
(8)
(i) Static load;
(ii) Hysteresis;
(iii) Influence number;
Explain the limitations of checking shaft alignment solely by hydraulic jacking methods
Reference Answer
### (a) Fair Curve or Rational Alignment **Concept:** Fair curve alignment, also known as rational alignment, is a modern and sophisticated method for aligning a vessel's propulsion shafting system. It deliberately deviates from a simplistic straight-line alignment. Instead, the bearings are intentionally offset vertically from a straight reference line to induce a predetermined 'fair curve' in the shafting. This approach is based on a comprehensive engineering analysis that considers all anticipated operating conditions. The primary objective is to ensure that every bearing along the shaft line remains positively loaded under all conditions (cold, hot, various drafts, and sea states) and that the bending stresses and bearing-specific loads are maintained within acceptable design limits. This prevents issues like hammering of bearings, edge loading, and excessive crankshaft web deflections.
Full answer on MeoMock — surveyor-grade reference answers for 7,000+ written exam questions.