Q1. Discuss the causes of vibration and noise in main gearing and describe detrimental effects on machinery and operating personnel. How would you detect the source(s) of this vibration and how might it be reduced to tolerable limits?
Q8. With reference to Main engine crankshafts:
a) Explain the term axial vibration
b) Describe, with the aid of a sketch, how axial vibration may be minimised
c) State with reasons which bearing would be most at risk due to the effects of axial vibration
d) Describe how damage to the bearing stated in part (c) may be repaired.
Q8. a. Explain why top bracing is used for large crosshead engines. (4)
b. Describe, with the aid of a sketch, a hydraulic top bracing unit for a large crosshead engine indicating where the top bracing is fitted and how it operates. (6)
C. Write instructions for the checking of a large crosshead engine top bracing system and a holding down system. (6)
Q5. With respect to Induced Vibrations in a ships hull:
A. State FOUR sources of excitation that may induce vibration into the main hull girder;
B. Suggest methods for reducing the vibration levels induced by EACH of the exciting forces in A.
Q2. (a) Define the term Torsional Vibration with respect to an engine crankshaft, stating the effect that high levels can have on an engine crankshaft.
(b) Explain how engine deterioration influences the risk of Torsional Vibration, stating what can be done to minimise that risk.
(c) Explain TWO possible reasons for the activation of a Torsional Vibration alarm after an engine has been started if there had been no previous history of such an alarm and if no maintenance had been undertaken on the engine whilst it was stopped.