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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)

Q8. How are large slow speed engines structured to withstand the following forces?

A. Forces due to combustion load;

B. Guide forces;

C. Inertia forces.

Q9. (a) Describe how it is determined whether a crankshaft was twisted during a major “smash up” in a main engine.

(b) Explain where twisting is most likely to occur.

(c) Specify with reasons the degree of twisting that might be accommodated without correction

(d) Explain briefly what adjustments and precautions should be instituted when putting an engine with a twisted crankshaft back into service.

Q7. Evaluate the influence of the following factors upon cylinder and piston ring wear rates. (16)

A. Position of rings in relation to piston crown.

B. Spread and proximity of coolant passages from liner wall.

C. Flow rate and specific heat of coolant.

D. Chromium plating of ring faces.

Q8. What is a “Cam"? Explain its function. With reference to its application in diesel engines

Discuss the requirement and the type of cam used in

a) Fuel Pump

b) Indicator drive

c) Inlet Valve

d) Exhaust Valve

e) Starting air distributor. (16)

Q3. 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)

Q8. (a) With a aid of a sketch briefly describe the important structural parts of 2-Stroke main Engine? How are different structural parts held together? (10)

(b) What is the function of Cross Head Guides? (6)