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Q8. Recent experience has shown persistence damage occurring on seating faces of main engine exhaust valve, which is not confined to any particular unit.

(a) State with reason the possible causes. (6)

(b) State the short-term action to be taken in order to minimize engine operational problem. (5)

(c) State with reason how future incident of this nature could be minimized. (5)

Q9. With reference to engine inlet and exhaust valves:

(a) State why tappet clearance is essential and why it must be periodically checked. (6)

(b) List with reasons the likely consequences of excessive and insufficient tappet clearance. (4)

(c) State how carbon build-up can occur during engine running and indicate the possible effects on cylinder performance. (6)

Q7. a) Give reasons why cracks occasionally develop in large piston crown. State to what extent this cracking is considered of consequence. (8)

b) State how it is dealt with in the following instances - A. Fine hairline; B. Localised and shallow crack. (8)

Q1. (a) How is fuel (HFO) for a marine diesel engine (main engine) being delivered from a fuel oil storage tank up to the combustion chamber? Explain with a line diagram. (10)

(b) What is the significance of the following:

          (i) Heating arrangement with temperature control. (3)

          (ii) Prevention of air lock in the system. (3)

Q6. During unit overhauling of Main engine, sudden rough weather caused accident in engine room. State what all checks and precaution taken up prior to carry out such operation.

Q5. (a) Sketch and describe a device employed for continuous monitoring of the viscosity of heavy fuel oil being supplied to a main engine (8)

(b) Explain how the system employing the device described in (a) operates to adjust the fuel viscosity. (8)

Q7. What is meant by ‘Power balancing’ with respect to reciprocating engines? Why is balance desirable and how is it obtained in the case of a large marine engine? What difficulties may be experienced in balancing an engine running at about 500 R.P.M. and how can these difficulties be overcome?

Q2. During your watch, main engine operation suddenly becomes erratic with speed varying widely even though fuel control remains at the value originally set:

a) State with reasons the possible cause of this behavior (8)

(b) Explain in detail how this cause can be traced, and the problems rectified. (8)

Q2. a) During an inspection it is noticed that tie rods of certain main engine units have become slack, state with reasons the possible causes of this. (5)

b) Explain how correct tension is restored and the risk of future slackness minimized. (5)

c) A tie rod has fractured and cannot be replaced immediately, State with reasons the course of action to be adopted in order to allow the engine to be operated without further damage. (6)

Q2. (a) Explain the purpose and working principle of the Load Dependent Cooling System (LDCS) in a two-stroke main engine. With the help of a diagram, describe how the system varies cooling water flow with engine load. (10)

(b) Discuss the advantages and disadvantages of using a load dependent cooling system over a conventional constant flow cooling system. What issues may arise if the system malfunctions. And how are they addressed? (6)

Q3. Sketch and describe the arrangement of a main engine camshaft chain. Describe the repair procedure following fracture of one chain link during operation of the engine. Give possible reasons for the failure and explain how the chain is set initially at the correct degree of tension. (16)

Q6. Briefly explain the following:

(a) How would you know if a refrigeration system is 'undercharged'? (4)

(b) What should you do to ensure that there is no water leakage into the engine cylinder before preparing main engine for sea? (4)

(c) What would be the probable cause of a rise in the level of the lub oil sump tank of a main engine? (4)

(d) How does the valve rotator as fitted on an exhaust valve of aux. engine work? (4)