Marine Diesel Engineering Examination - SQA Small Vessel Second Engineer 060-01

Too large a tappet clearance can cause the exhaust valve to not fully close, leading to poor combustion, increased emissions, and potential damage to the valve and valve seat.

Too small a tappet clearance can cause the exhaust valve to not fully open, leading to increased exhaust backpressure, reduced engine power, and potential valve train damage.

Double (nested) valve springs may be fitted to provide additional force to quickly close the valves, reducing the risk of valve float at high engine speeds.

Zinc anodes are used in air coolers to provide cathodic protection, preventing corrosion of the metal components.

Vent cocks allow air to be released from the air cooler, preventing air pockets that could reduce cooling efficiency.

Tube fins increase the surface area of the air cooler tubes, improving heat transfer from the coolant to the surrounding air.

To manually test the set points, the cooling water temperature would be gradually increased, either by restricting coolant flow or applying external heat. The high temperature alarm should activate at the specified set point, and the engine should shut down at the higher shut down set point temperature.

Too large a tappet clearance can prevent the exhaust valve from fully closing, leading to poor combustion, increased emissions, and potential damage to the valve and valve seat.

The delivered quantity of fuel oil is controlled by varying the stroke of the fuel injection pump plunger.

The purpose of the delivery valve is to prevent the back-flow of fuel from the injector nozzle into the pump.

Two methods of cylinder liner lubrication in medium speed diesel engines are: (1) Splash lubrication, where oil is splashed onto the liner from the crankcase, and (2) Pressure lubrication, where oil is supplied directly to the liner through oil galleries.

(i) Insufficient lubrication can lead to increased wear, scuffing, and seizure of the piston and liner. (ii) Excessive lubrication can cause oil dilution, increased oil consumption, and potentially lead to oil leaks.

A plate type heat exchanger consists of a series of thin, corrugated metal plates stacked together with gaskets between them. The plates are arranged to create alternating flow channels for the two fluids, allowing for efficient heat transfer between them.

Three advantages of the plate type heat exchanger compared to the tube type are: (1) higher heat transfer efficiency, (2) smaller size and footprint, and (3) easier maintenance and cleaning.

Four safety interlocks that may be fitted to a direct air start medium speed diesel engine to prevent inadvertent starting during maintenance are: (1) Emergency stop button, (2) Air supply isolation valve, (3) Crankshaft turning gear engagement, and (4) Maintenance mode switch.

The air start valve opens during the compression stroke, slightly before the inlet valve closes and the exhaust valve opens. This allows the compressed air to enter the cylinder and start the engine rotation.

When the piston is removed, the cylinder liner and piston assembly should be inspected for wear, scoring, and other damage. Possible faults that may be found include excessive wear, scuffing, seizure marks, and deposits on the liner and piston.

(a) Vibration from the engine should be damped to prevent the transmission of harmful vibrations to the gearbox and other components, which can lead to premature wear and failure. (b) Vibration damping is typically achieved through the use of a flexible coupling or damper installed between the engine and gearbox.

(a) Advantages of helical teeth over spur teeth include smoother operation, higher load capacity, and reduced noise and vibration. Disadvantages include more complex manufacturing and higher cost. (b) Advantages of double helix over single helix include better load distribution, reduced end thrust, and improved balance. Disadvantages include more complex design and manufacturing.