Small Vessel EOOW 060-01 Marine Diesel Engineering Exam

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Questions and Answers

Explain why relief valves may be fitted to diesel engine crankcases.

To prevent excessive pressure buildup inside the crankcase.

Outline the circumstances that may cause relief valves in diesel engine crankcases to operate.

Excessive pressure due to combustion blow-by or abnormal engine operation.

State a safety detection system that may be fitted to diesel engine crankcases.

Pressure sensors or alarms.

Describe what is meant by the term microbe in the context of microbial infestation of distillate fuel.

A microscopic organism, such as bacteria or fungi. Signup and view all the answers

State what microbes need to survive in distillate fuel.

Water and nutrients. Signup and view all the answers

Describe the possible diesel engine problems caused by microbial infestation of distillate fuel.

Clogged filters, corrosion, and fuel degradation. Signup and view all the answers

Describe how microbial infestation of distillate fuel can be identified.

Through visual inspection, microbial testing kits, or fuel analysis. Signup and view all the answers

Explain how the lubricating oil of a diesel engine may become contaminated with water.

Through condensation, leaks, or improper maintenance practices. Signup and view all the answers

Outline the problems that water in an engine oil may cause.

Reduced lubricating properties, corrosion, and accelerated wear. Signup and view all the answers

Explain the term 'atomisation' with reference to the combustion of fuel.

Atomisation refers to the process of breaking down fuel into small particles or droplets to mix better with air for efficient combustion. Signup and view all the answers

Describe the possible causes of high bearing temperatures in diesel engines.

Lack of lubrication, overloading, misalignment, or bearing damage. Signup and view all the answers

Explain the procedure to be adopted if high bearing temperatures are detected in a diesel engine.

Immediate shutdown, inspection, and rectification of the root cause. Signup and view all the answers

What is the purpose of the volute casing in main engine turbochargers?

The volute casing helps in converting the high-velocity exhaust gas energy into pressure energy before it enters the turbine blades. Signup and view all the answers

Explain the difference between in-line and Vee type engines.

In-line engines have cylinders arranged in a straight line, while Vee type engines have cylinders arranged in a V-shape. Signup and view all the answers

State the advantages of Vee type engines.

Vee type engines are more compact, have better balance, and allow for better power output compared to in-line engines. Signup and view all the answers

What factors influence the terms explained in the combustion of fuel?

Factors like air-fuel ratio, fuel quality, combustion chamber design, and engine operating conditions influence atomisation, penetration, and compression ratio. Signup and view all the answers

Explain the purpose of the diffuser in main engine turbochargers.

The diffuser slows down the high-velocity air from the compressor to convert kinetic energy into pressure energy before entering the engine. Signup and view all the answers

Sketch two Vee engine bottom end arrangement types.

Sketches will vary but should show the different configurations of crankshafts, connecting rods, and pistons in Vee engine bottom end arrangements. Signup and view all the answers

What is the purpose of the nozzle ring in main engine turbochargers?

The nozzle ring directs the high-velocity exhaust gases onto the turbine blades, driving the turbocharger. Signup and view all the answers

Study Notes

Relief Valve in Diesel Engines

Relief valves are fitted to diesel engine crankcases to prevent excessive pressure build-up.
Excessive pressure can be caused by a variety of factors, including:
- Blow-by: When combustion gases leak past the piston rings and into the crankcase.
- Crankcase ventilation system failure: When the system that removes crankcase gases malfunctions.
- Overfilling of the crankcase: When too much oil is added.
A safety detection system that may be fitted to diesel engine crankcases is a pressure switch that triggers an alarm if the pressure exceeds a set limit.

Microbial Infestation in Diesel Fuel

Microbial Infestation is a phenomenon where microorganisms, specifically microbes, grow and reproduce in distillate fuel.
These microbes need water and nutrients to survive in distillate fuel, which they source from the fuel itself or from contamination.
Microbial infestation can cause a variety of problems in diesel engines:
- Fuel filter blockage: The microbes can form a slime that can clog filters.
- Fuel tank corrosion: The microbes can produce acids that corrode the fuel tank.
- Fuel injector blockage: The microbes can cause blockages in the injectors, leading to poor fuel flow.
- Engine performance issues: The engine may run rough or stall due to fuel quality issues.
Identifying microbial infestation involves visually examining the fuel for signs of slime, testing for microbe presence, and observing fuel filter clogging.

Water Contamination in Lubricating Oil

Lubricating oil can become contaminated with water through various means:
- Leakage: From faulty seals, gaskets, or cooling systems.
- Condensation: When water vapor condenses in the crankcase, usually during cold starts or when the engine is not running.
- Overfilling with water: Accidental addition of water to the oil sump.
Water in the lubricating oil can cause several problems:
- Reduced lubrication: Water displaces oil, leading to friction and wear.
- Corrosion: Water accelerates corrosion of engine components.
- Oil degradation: Water contaminates the oil, leading to sludge build-up.
- Increased viscosity: Water can increase the viscosity of the oil, making it harder to circulate.

Atomization and Diesel Engine Combustion

Atomization refers to the process of breaking down liquid fuel into fine droplets, which are then mixed with air for combustion.
Efficient atomization is crucial for complete combustion in diesel engines, which are typically characterized by high compression ratios.

High Bearing Temperatures in Diesel Engines

Possible causes of high bearing temperatures in diesel engines:
- Insufficient lubrication: Lack of sufficient lubrication leads to increased friction and heat.
- Bearing wear: Worn bearings generate excessive friction and heat.
- Improper bearing clearance: Incorrect bearing clearance can cause excessive load and heat.
- Oil contamination: Contaminated oil reduces lubrication effectiveness and increases temperatures.
- Overheating: Overheating of the engine can lead to high bearing temperatures.
If high bearing temperatures are detected, the engine should be shut down immediately and the root cause investigated.

Turbocharger Components and Features

Volute casing: The volute casing in a turbocharger guides the exhaust gas flow, creating a pressure gradient that drives the turbine.
Diffuser: The diffuser in a turbocharger slows down the compressed air flow, increasing its pressure before it enters the combustion chamber.

Engine Types

In-line engines: In-line engines have cylinders arranged in a single line.
Vee-type engines: Vee-type engines have cylinders arranged in two banks, forming a 'V' shape.
Advantages of Vee-type engines:
- Compact size: Vee-type engines are more compact than in-line engines with the same number of cylinders.
- Lower vibrations: The arrangement of cylinders in a Vee shape helps balance out the vibrations generated by the engine.
Two Vee engine bottom end arrangement types:
- Common crankshaft: Both banks share a single crankshaft.
- Separate crankshafts: Each bank has its own crankshaft, connected by a gearbox or a common drive shaft.

Nozzle Ring in Turbochargers

The nozzle ring in a turbocharger is responsible for controlling the flow of exhaust gases to the turbine.
The nozzle ring can be adjusted to vary the turbine speed, affecting boost pressure and engine performance.

Factors Influencing Diesel Engine Combustion

Factors that influence diesel engine combustion:
- Fuel properties: Fuel type, cetane number, and viscosity.
- Air intake: Amount of air, air temperature, and air pressure.
- Engine speed: How fast or slow the engine is running.
- Injection timing: When the fuel is injected into the cylinder.
- Combustion chamber design: Shape and size of the combustion chamber.

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Description

Prepare for the Small Vessel Engineer Officer of the Watch (EOOW) 060-01 examination administered by the Scottish Qualifications Authority on behalf of the Maritime and Coastguard Agency. Practice questions and guidelines for the upcoming exam on Friday, 20 October 2023, from 1400 to 1600 hrs.