EKM-Sep-2021

Q1. (a) Explain the factors you would consider in deciding whether to open up a cylinder unit for an overhaul? After opening the unit and preparing for assembly, how would you decide whether to renew or re-use piston rings? 

(b) List the causes of piston ring failure which may result in gas leakage or ring breakage.

Q2.Show with the aid of a sketch how fuel can be continuously circulated through fuel injection valves on large engines while the engine is operating or under, stand-by conditions.

Q3. A. Sketch and describe the Main engine starting air distributor. 

B. List the safety devices and interlocks incorporated in the main engine air starting system and state the purpose of each.

Q4. A. Explain the possible reasons T/C vibration while operating at a steady speed; 

B. State how the incidence of turbocharger vibration might be minimized; 

C. Explain the action to be taken in order to maintain 2 stroke engine operation in the vent of turbocharger having to be taken out of service; 

D. Indicate the effect this action will have on engine operation.

Q5. (a) Describe, with the aid of a sketch, the main engine hydraulically operated exhaust valve which is designed to rotate in service. (b)Explain TWO methods of how the opening of the exhaust valve described in part(a) can be controlled. (c) Explain why the valve described in part (a) is rotated.

Q6. With reference to the large two-stroke engine: (a) Explain how abnormal and excessive cylinder liner wear is caused, state how it can be detected: (b) Explain the effects and consequences of excessive cylinder liner wear (c) Explain how abnormal cylinder liner wear may be prevented.

Q7. With regards to connecting rod ovality of four-stroke diesel Engine. Explain Following. a) Importance of connecting rod ovality. b) Method of measuring the connecting rod ovality. C) Discuss the impact of ovality if it increases beyond the maximum allowance limit. d) Method of ascertaining the elongation of connecting rod bolts.

Q8.Describe the starting and reversing system of an electronically controlled diesel engine and compare it with an engine having a camshaft and explain the following; A. reduction in air consumption during engine starting; B. Improved performance during astern starting and crash astern.

Q9. Write a report to the engineering superintendent regarding the replacement of the fuel injectors of three main engine units due to server erosion of the nozzle holes and burning of the injector tips. Explain in your report how the defects were detected, the likely cause of the damage and the action taken to prevent further incidents of this type.