CON & NA-FEB-2020

Q1. With reference to Container Ships : (a) Describe the problem of Parametric Roll ; (b) Explain how this problem is suitably addressed in the design and operation of the vessel. (c) Describe possible methods for improving the stability of these vessels.

 

Q2. The Hull of a vessel in way of the purifier room requires extensive welding repairs and as Chief Engineer you are requested to supervise.

a. Suggest a suitable type of welding process.

b. State, With reasons, FOUR common welding defects.

c. State what tests may be carried out for the hull repair before returning the vessel to service.

Q3. A. With reference to the underwater surface of a ship’s hull; i. Describe a hull plate roughness analyser system; ii. State the significance of the roughness profile and compare the typical roughness values for a new ship and a ship eight years old;

B. Which reference to the application of self-polishing paint in dry dock – i. Describe the plate preparation necessary; ii. State the defects that may occur in the paint coating if it is not correctly applied.

Q4. Describe a forced ventilation system for the machinery spaces and a natural ventilation system for a lower hold. Why hold ventilation is considered necessary?

Q5. With reference to the prevention of hull corrosion discusses: A. Surface preparation and painting of new ship plates. B. Design of the ships structure and its maintenance. C. Catholic protection by sacrificial anodes, of the internal and external areas of the ship.

Q6. A. Describe briefly the significance of the factor of sub-division;

B. A box shaped vessel 65m X 12m X 8m has KG 4m and is floating in sea water upright on an even keel at 4m draft F and A. Calculate the moments of statically stability at i. 5 degrees and ii. 25 degrees’ heel.
 

Q7. A. Describe the effect of cavitation’s on the propeller blades.

B. A propeller 4.6m diameter has a pitch of 4.3m and boss diameter of 0.75. The real slip is 28% at 95 rev/min. Calculate the speed of advance, thrust and thrust power.
 

Q8. A. Describe the stability requirements of a ship for dry-docking.

B. A ship 130m long displaces 14000 tonne when floating at draughts of 7.5m forward and 8.10m aft. GML –125m, TPC – 18,LCF-3m aft of midships. Calculate the final draughts when a mass of 180 tonne lying 40m aft of midships is removed from the ship.
 

Q9. A ship of 9.900 tonnes displacement has KM 7.3m, and KG 6.4m. She has yet to load two 50 tonne lifts her own gear and the first lift is to be placed on deck on the inshore side (KG = 9m and centre of gravity = 6m, out from centre line). When the derrick plumbs the quay, its head is 15m above the keel and 12m out from centre line. Calculate the maximum list during the operation.
 

Q10. (a) Describe how thrust power is determined.

(b) The following information relates to a model propeller of 400mm pitch
Revs/min  400 450 500 550 600
Thrust N     175 260 365 480 610
Torque Nm 16.8 22.4 28.2 34.3 30.5
(i) Plot curves of thrust and torque against rev/min (ii) When the speed of advance of the model is 150 m / min and slip 0.20, calculate the efficiency.