Small Vessel Second Engineer - Marine Diesel Engineering Exam

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What are the effects of too large a tappet clearance in four-stroke diesel engine exhaust valves?

Decreased compression and loss of power

What are the effects of too small a tappet clearance in four-stroke diesel engine exhaust valves?

Valve not fully closing, leading to burnt valves

Why may double (nested) valve springs be fitted in a four-stroke diesel engine?

To prevent valve float and ensure proper valve operation

What is the purpose of zinc anodes in air coolers?

To protect against galvanic corrosion Signup and view all the answers

What is the purpose of vent cocks in air coolers?

To release trapped air and gases Signup and view all the answers

What is the purpose of tube fins in air coolers?

To increase the surface area for better heat transfer Signup and view all the answers

Describe a procedure for manually testing the set points on diesel generator HT cooling water, high temperature alarm, and shut down.

Manually adjust the set points and observe the responses to ensure proper functioning Signup and view all the answers

How can the delivered quantity of fuel oil be controlled in Bosch or jerk type fuel injection pumps?

By adjusting the rack position or the cam profile Signup and view all the answers

What is the purpose of the delivery valve in fuel injection pumps?

Prevents fuel from flowing back into the pump Signup and view all the answers

Describe TWO methods of cylinder liner lubrication in medium speed diesel engines.

Splash lubrication and forced lubrication Signup and view all the answers

What are the possible effects of insufficient lubrication in an engine?

Increased friction, overheating, and wear on engine components Signup and view all the answers

What are the possible effects of excessive lubrication in an engine?

Oil leaks, increased oil consumption, and potential damage to the engine seals Signup and view all the answers

Describe the construction of a plate type heat exchanger with the aid of a sketch.

Plate heat exchangers consist of multiple thin plates with gaskets in between, stacked together to create flow channels for heat exchange Signup and view all the answers

State THREE advantages of plate type heat exchangers compared with tube type heat exchangers.

Higher heat transfer efficiency, compact size, and ease of maintenance Signup and view all the answers

List FOUR safety interlocks that may be fitted to a direct air start medium speed diesel engine to prevent inadvertent starting during maintenance.

Locking pins, key switches, warning signs, and mechanical barriers Signup and view all the answers

Explain the opening period of an air start valve on a four-stroke diesel engine in relation to the crank angle, inlet, and exhaust valves.

The air start valve opens during the compression stroke after the exhaust valve closes and before the inlet valve opens Signup and view all the answers

Effect of too small exhaust tappet clearance

Valve does not close fully leading to burning of the valve.

Effect of too large exhaust tappet clearance

Decreases the engine's compression ratio, resulting in a loss of power.

Purpose of double valve springs

They prevent valve float, ensuring reliable valve operation at high engine speeds.

Purpose of zinc anodes in air coolers

They protect the air cooler from galvanic corrosion, which occurs when dissimilar metals come into contact.