DieselShip's Online Content Library

Q1. With respect to the properties of fuel oil, explain the significance of the following terms. (4X4)

(a) Calculated Carbon Aromaticity Index (CCAI).

(b) Open flash point and Closed flash point.

(c) The importance of Sodium to Vanadium Ratio.

(d) Octane Number.

Q2. a) Explain with a sketch the operation of an automatic expansion valve as fitted in the direct expansion refrigeration plants. How is this valve adjusted? (8)

b) Explain how critical temperature restricts plant operation and how these limitations can be overcome? (4)

c) Explain how this system maintains the provision rooms at different temperatures? (4)

Q3. With reference to sleeved keyless propeller assemblies:

A. State with reasons which metal the sleeve should be made for contact with a forged mild steel tail shaft.  (3)

B. State the material used to bond the sleeve to the propeller boss and the general thickness of the bonding material. (3)

C. When removing the propeller from the tail end shaft, state why the following procedures are not recommended: (6)

(i) Application of push off force by means of wedges or jacks and draw off force by strong back.

(ii) Expansion of propeller boss by concentrated local heating with gas torches.

D.  State the correct procedure for the removal of the propeller from tail end shaft. (4)

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Q9: With reference to sleeved keyless propeller assemblies: A. (i) State, with reasons, the metals used in the manufacture of the sleeve and tail end shaft; (ii)State the type and thickness of material used to bond the sleeve to the propeller boss. B. When removing the propeller from the tail end shaft, state why the following procedures are not recommended: (i) Application of push off force by means of wedges or jacks and draw off force by strong back; (ii) Expansion of propeller boss by concentrated local heating with gas torches. C.  State the correct procedure for the removal of the propeller from tail end shaft

Q4. Explain how a Controllable Pitch Propeller (CPP) alters the magnitude and direction of vessel thrust without changing the main engine revolutions per minute (RPM). Include the role of the hydraulic oil distribution box and blade spindle mechanisms in your answer. (16)

Q5. With reference to electro-hydraulic steering gears:

A. Explain in terms of control parlance, the function of the “Hunting gear”. (6)

B. Explain the consequences if the standby pumping unit is motored. (4)

C. State TWO methods employed to prevent the standby hydraulic pump being motored by the operating unit. (6)

Q6. Materials used for hull and machinery are subject to stress and strain in service.

(a) In the context, explain the following: (8)

(i) Types of stress.              (ii) Types of strain.

(b) Describe the tests that may be carried out on steel to be used for ships side plating. (8)

Q7. Explain why a material may fracture when stressed below its yield point. Give examples of components which might fracture in this way if suitable precautions are not taken. Explain how such fractures can be avoided with reference to the materials chosen, careful design and workmanship. (16)

Q8. Reverse osmosis is the modern alternative for shipboard production of drinking water.

(a) Describe using simple diagrams if necessary, the principle of reverse osmosis. (4)

(b) Sketch a line diagram showing a single pass system for producing fresh water from sea water. (8)

(c) Describe such a system. (4)

Q9. Discuss, with reference to the superheater outlet temperature of the main boiler operating at a constant load, the following statements: (4X4)

a) An increase in excess air will tend to cause a decrease in superheater outlet temperature due to the cooling effect of more air being introduced.

b) A decrease in economizer inlet temperature will tend to cause a decrease in super heater outlet temperature due to the cooling effect of more water being introduced.

c) Badly fouled generating tube banks will cause an increase in the super heater outlet temperature.

d) Excessive amounts of total dissolved solids in the boiler water will cause variations in the super heater outlet temperature.