Third Class Marine Engineering

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Third Class Marine Engineering

• Mechanical Systems
• 3ME6

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Aims

• Describe the function of the lubricating oil
  system.
• Describe the function of the fuel system.
• Describe the function of the cooling system.

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What you should have already done

• HEALTH AND SAFETY GENERAL
• 3 ME 1
• HEALTH AND SAFETY WORKSHOP
• 3 ME 2
• INTRODUCTION TO MARINE ENGINEERING
• 3 ME 3
• ENGINE CONSTRUCTION
• 3 ME 4
• ENGINE CYCLES
• 3 ME 5
• QUESTIONS ON PAGES
• 13, 19, 25, 31 AND 39

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Essential Mechanical Systems

• Diesel engines have 3 main systems that provide
  the following functions.
• Lubricating oil system to cool and lubricate the
  moving parts of the engine.
• Fuel system to provide clean fuel to the
  injectors so that it can be burnt to give power.
• Cooling system that will cool the engine and its
  auxiliary components.

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The Basic Mechanical System

• Any basic system has a tank, filter, pump and a
  method of indicating it is running correctly.
  Systems have a way of returning excess fluid back
  to the tank.

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Basic Mechanical System

• The tank is filled to the correct working level,
  excess can be drained away. The liquid is drawn
  through the filter which removes any debris. The
  liquid is then pumped up to pressure using the
  pump and discharged to the system where it is
  used. Liquid is then returned back to the tank
  and the cycle repeats itself.

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Basic Mechanical System

• When filling any system you must use a correctly
  labelled container and fill it with the correct
  fluid. Oil in to the sump and cooling water into
  the fresh water header tank.
• Beware of filling the wrong tank with the wrong
  fluid.

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Basic Mechanical System

• The system pressure can be monitored using a
  pressure gauge.
• Oil, water and fuel levels are always checked
  prior to starting the engine.

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Basic Mechanical System

• It is good engineering practice to monitor the
  conditions of the mechanical systems regularly
  for problems such as overheating, lack of cooling
  or leaks on the various systems. Learning the
  components of the engine will help you identify
  any problems when the engine is running. Many
  checks can be done before the engine is started
  to ensure your engine will run efficiently.

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Lubrication System

• The lubrication system makes sure that every
  moving part in the engine gets oil so that it can
  move easily. The two main parts needing oil are
  the pistons (so they can slide easily in their
  cylinders) and any bearings that allow things
  like the crankshaft and camshafts to rotate
  freely. In most cars, oil is sucked out of the
  oil pan by the oil pump, run through the oil
  filter to remove any grit, and then squirted
  under high pressure onto bearings and the
  cylinder walls. The oil then trickles down into
  the sump, where it is collected again and the
  cycle repeats.

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Lubrication System

• Most lubricating oil systems will have an oil
  pressure gauge for checking the system pressure.
  The lubricating oil level is checked using a dip
  stick which shows the level in the engine sump.
  The oil system has a thermostat to keep the
  lubricating oil at a constant temperature.

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Lubrication System
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Fuel System

• Diesel engine fuel systems supplies clean fuel
  from the fuel tank, through filters to a lift
  pump and finally to the injection pump, it is
  then delivered to the individual injectors which
  spray the fuel into the top of the piston. Fuel
  systems must be kept clean and free of any water,
  which would otherwise collect at the bottom of
  the fuel tank.

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Fuel System
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Cooling System

• Diesel engines are cooled by air or by a water
  cooling system. Air is used to cool the outer
  fins of the cylinder head. It is directed over
  the fins giving a cooling effect. Most diesel
  engines are cooled by fresh water which
  circulates under pressure around the engine
  cylinder block and cylinder heads narrow
  passages, this fresh water is cooled by pumped
  sea water which also passes through a fresh water
  cooler. The fresh water is maintained at the
  correct temperature by a thermostat.

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Cooling System
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WARNING

• THERE ARE MANY PARTS ON ENGINES WHICH GET HOT AS
  THE ENGINE WARMS UP, CARE SHOULD BE TAKEN TO KEEP
  CLEAR OF MOVING AND HOT COMPONENTS. THE COOLING
  WATER PIPE WILL GET VERY HOT UNTIL THE THERMOSTAT
  VALVE STARTS TO REGULATE THE ENGINES TEMPERATURE.

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OBJECTIVESYou should now be able

• Describe the purpose of each of the mechanical
  systems, and the medium used by each system.
• Answer the questions on page 45 of your task book

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Next Time

• You should have completed the questions on page
  45.
• Electrical System
• 3ME7