STCW Marine Engineering 3

Question 1

What is the purpose of an intercooler in a marine diesel engine air supply system?

Accepted Answer

To cool compressed air from the turbocharger before it enters the engine

Answer

Cooling the compressed air after the turbocharger (charge air cooling) increases air density, improving combustion efficiency and reducing thermal stress.

Question 2

In a marine refrigeration system, what is the role of the expansion valve?

Accepted Answer

To reduce refrigerant pressure, causing it to vaporize and absorb heat

Answer

The expansion valve throttles high-pressure liquid refrigerant to low pressure, allowing it to evaporate and absorb heat from the space being cooled.

Question 3

What does 'cavitation' mean in the context of a centrifugal pump?

Accepted Answer

Formation and collapse of vapor bubbles due to low inlet pressure, causing damage and loss of flow

Answer

Cavitation occurs when local pressure drops below the liquid's vapor pressure, forming bubbles that collapse violently and erode pump components.

Question 4

Which STCW document outlines the minimum standards of competence for officers in charge of an engineering watch?

Accepted Answer

STCW Code Table A-III/1

Answer

STCW Code Table A-III/1 specifies the minimum standard of competence for officers in charge of an engineering watch in a manned engine room.

Question 5

What is the purpose of the crankcase relief valve on a marine diesel engine?

Accepted Answer

To vent excessive crankcase pressure rapidly and prevent an explosion

Answer

Crankcase relief valves open rapidly during a crankcase explosion to release pressure, preventing catastrophic structural failure of the engine.

(STCW) Standards Certification and Watchkeeping for Seafarers Practice Test

(STCW) Standards Certification and Watchkeeping for Seafarers Practice Test

STCW Marine Engineering 3