Marine Engineering Third Class Study Guide and Training Manual

The Sea Cadets

MARINE ENGINEERING

THIRD CLASS

STUDY GUIDE AND TRAINING MANUAL

Issue 1 SCTC GANNET

August 2001

Marine Engineering – Third Class – Study Guide and Training Manual

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MARINE ENGINEERING THIRD CLASS

STUDY GUIDE

AND TRAINING MANUAL

NAME _____________________________ RATE _____________________________ ADDRESS _____________________________ _____________________________ _____________________________ UNIT _____________________________ DISTRICT _____________________________ AREA _____________________________ DATE STARTED _____________________________

INSTRUCTOR ________________________________ AREA STAFF OFFICER ________________________________


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CONTENTS

SYLLABUS SUBJECT PAGE REFERENCE 3 ME 1 Health and Safety - General 7 3 ME 2 Health and Safety - Workshop 15 3 ME 3 Introduction to Marine Engineering 21 3 ME 4 Engine Construction 27 3 ME 5 Engine Cycles 33 3 ME 6 Mechanical Systems 41 3 ME 7 Electrical System 47 3 ME 8 Basic Electrical Knowledge 51 3 ME 9 Power Generation 55 3 ME 10 Tools and Fasteners 59

Progress Chart 67


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Health and Safety - General

3 ME 1

Introduction The Health and Safety at work Act 1974 places formal responsibility for health and safety at work on all personnel. This act of Parliament applies to civilians and all service personnel, instructors and Cadets. It is the duty of Commanding Officers and superiors at all levels to: a) Ensure that compartments and access are kept in a safe condition. b) Ensure that equipment and machinery are operated safely. c) Inform personnel who may be at risk of the existence of hazards and how to

reduce them by taking precautions. d) Provide training and supervision to maintain safe conditions. Cadets must take responsibility for their own personal protection, use the correct equipment, and follow the health, safety and fire instructions provided. Unit Fire Drill Your fire drill card will tell you how to evacuate the unit, by which route, and where you should muster in the event of a fire or emergency. It will also tell you the emergency phone number of the emergency services. You should memorise this number and where the fire appliances are located. Emergency Signs These should glow in the dark, are provided for your safe exit of the building. Your instructor should take you on a tour of your unit and identify these signs and safe exit routes. First Aid box, eye wash bottles and fire blankets These are located in different locations; most units have a first aid box in the engineering workshop and one in the admin office. They will contain basic first aid items, such as bandages, dressings and Elastoplast and should only be used in an emergency. Eye wash bottles are used to flush the eye when contaminated. Fire blankets will smother the fire, and remove oxygen.


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Unit Fire appliances There may be several types of appliances in your unit, all should be in working order and comply with current safety standards. Each appliance should be used as directed. Type Use Colour (a) Water Wood, paper, textiles. Red Not on electrical fires.

(b) AFFF Foam Wood, paper, textiles Cream

and flammable liquids. Not on electrical fires.

(c) Dry Powder General, oil and Blue electrical.

(d) CO2 Electrical and Black flammable liquids. Potential Hazards There are three types of hazards associated with all engines:- a) Mechanical Fuels, Oils, spillages and fires. b) Electrical Shock, burns, arcing and fires. c) General Rotating machinery, noise and exhaust fumes. Personal Safety Rules • All accidents must be reported to the instructor immediately. • Any fuel/oil must be washed from eyes instantly, using an eye-wash bottle or

fresh tap water. • Oil/fuel spillages are to be mopped up immediately. • Overalls are to be worn when in an engineering environment. • Protective footwear is to be worn in an engineering environment. • Ear defenders are to be used when engines are running. • Barrier cream is to be used before working with machinery. • Wash thoroughly before eating, drinking or using the toilet. • Do not skylark when working with or near to engines or machinery. • Jewellery or items that may get caught in machinery are not to be worn. • Keep away from engine exhaust fumes and hot parts of the engine.


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Fire Drill These will be explained by your instructors and should be fully understood as your life may depend on it. a) They will include fire exits and what to do in case of a fire and where to

muster when you are clear of the fire. b) Emergency drills will include the various ways in which to safely shut down

an engine. This will be covered before you start the practical projects. Health and Safety Declaration This is a form declaring that you have understood the health and safety instructions given to you by your instructor. All Cadets and Staff including instructors are to sign this declaration at the start of any Marine Engineering course. This is an example of a Health and Safety declaration.

I hereby declare that I have been informed of the above hazards by the Course Marine Engineering Instructor, and agree to abide by the conditions and limitations imposed as a result of them, during my course. Furthermore, I have been informed of the emergency procedures to be followed in the event of a Fire, Emergency evacuation and personal injury or dangerous occurrence.

Date Name Rank/Rate Signature Course Remarks


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The Sea Cadets

Declaration of Health and Safety Induction

I hereby declare that I have been informed of the above hazards by the Course Marine Engineering Instructor, and agree to abide by the conditions and limitations imposed as a result of them, during my course. Furthermore, I have been informed of the emergency procedures to be followed in the event of a Fire, Emergency evacuation and personal injury or dangerous occurrence.

Date Name Rank/Rate Signature Course Remarks


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Questions : 3 ME 1 1. Who is responsible for Health and Safety in you Unit? 2. Identify the Fire Extinguishers and First Aid Boxes fitted in your Unit. 3. Describe where your emergency assembly point is located. 4. Name 5 PERSONAL SAFETY rules. 5. What is the Emergency Drill for your unit?

Cadet Objectives

Identify all the unit fire extinguishers, and their uses. Recognise potential hazards Explain the actions to be taken in the event of an emergency Take part in an emergency drill

Course Notes _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


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Health and Safety - Workshop

3 ME 2 Emergency procedures and equipment Fire Drill and Unit layout - Revise your unit’s fire drill and the layout of your unit. This is necessary as every one needs to know the layout of the building so that they can find their way out when blinded by smoke or when in the dark. Locate the Glow signs and the stowage of your fire fighting equipment in your unit. Find your muster point and remember it. First Aid Kits and Eye wash bottles - Using a First Aid kit discuss the contents and where the first aid kits and eyewash bottles are located in the building and on your motor boat (if applicable). Personal protective equipment These consist of the following:- (a) Hard Hat Understand that webbing spreads the impact over the whole head

rather than the point of impact. There is also a date system for use, Unapproved stickers or paint/inks must not be used.

(b) Safety Glasses Worn if there is a slight possibility of eye damage - as a

precautionary measure. For use when working at a work bench or on an engine.

(c) Ear Defenders Various types, ear-muff type, clip-on, and small plugs

inserted in ear, to reduce danger of exposure to high level noise. (d) Goggles Used where the possibility of eye damage is increased. They will

absorb impact and give all round protection when handling dangerous fluids. (e) Face Mask Various types for dust and partial fume removal, they can be

throw-away or re-useable types. (f) Overalls Various different types, must be washed regularly and instructions

followed. Some may be flame retardant and used for special tasks. Disposable overalls give little protection and should only be used as a last resort.

(g) Gloves Various types for hand and lower arm protection. (h) Boots Various types. Most have protective toe and heel guards fitted. Many

are resistant to oils and acids. They should have a non-slip sole for working in engine rooms and with oily machinery.


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Avoiding hazards in the workshop environment Fuel and electrical fires can be started by poor maintenance, carelessness and not following safety guidelines. By following these guidelines, risks to Staff and Cadets can be minimised. • Stow fuel using a safety type of canister and away from heat. • Petrol fumes will ignite more easily than diesel fumes. • Oils, greases and fuels are slippery and spills must be cleaned up immediately. • No Smoking or Naked Lights rules must be observed and correct extinguishers are

at hand when working in an engineering environment. • Tidiness is next to godliness – no rags or other flammable materials are to be left

loafing. • Fumes can kill, particularly engine fumes from the exhaust. Do not operate

engines inside buildings as exhaust gasses will quickly fill a poorly ventilated room.

• Any accident, however small must be reported and recorded. • Never work on live equipment. Disconnect electrical supplies before working. • Batteries are to be well ventilated when charging. • Keep water away from electrical components. • Know how to stop a machine before you start it! • Never reach across rotating or moving machinery. • Only properly installed machinery is to be run. • Use the appropriate Personal Protective Equipment for the job in hand. • Use ear defenders when operating machinery. • Wash thoroughly before eating and drinking or using the heads. • Use barrier cream on your hands prior to working. • No jewellery is to be worn when in a workshop environment or operating

machinery. • No skylarking, as this often leads to accidents. • Never lift heavy weights or engines without supervision and the correct

equipment. Electrical hazards Electricity is dangerous, it can kill or injure!

(a) Electric Shock caused by electricity flowing through the body, which in turn affects the control of the muscles, it can stop the heart and lead to death.

• Do not touch the casualty, until he/she is isolated from the power. • Isolate the power supply and summon help. • Carry out first aid if qualified.

(b) Electrical Burns Severe burns are caused at the point of contact with

the electrical source.

(c) Electric sparking and Fires sparks can jump across air gaps, fires can be caused by overheating of cables, poor insulation or by nearby flammable materials.


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Hazards associated with all engines are: We can reduce these potential hazards but we cannot totally eliminate them. Many of these hazards can be reduced by sensible behaviour and by following basic safety rules. Engine Fuel – By their very nature, fuel and oils catch fire very easily. Care is to be taken to ensure that any leaks are dealt with as soon as they occur, and that all spillages are cleared away as a matter of urgency. Rotating Machinery – This should always be protected by guards where possible. Never remove a guard whilst a machine is running. Never run a machine without a guard in place. Never lean over a running engine. Oil and Personal Hygiene – The term mineral oil covers a large range of fuels, oils and lubricating oils. Prolonged contact with certain oils may lead to swellings and sores which are slow to heal and could be cancerous. The use of barrier creams or gloves will prevent this occurring. If in doubt seek medical attention. Noise – The internal combustion engine generates noise at a pitch and a volume which is detrimental to hearing. Prolonged exposure to noise from a running diesel engine can lead to permanent damage to hearing and possible deafness. Ear Defenders or Ear Plugs are to be worn at all times when in the vicinity of running engines. Reporting of accidents It mandatory that all accidents are reported to your instructor. This is a legal and a SCC requirement. Accidents are to be recorded in the Unit accident book and the Commanding Officer informed.


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Questions : 3 ME 2

1. What are the 4 main hazards associated with running engines? 2. Name 5 personal safety rules. 3. What is the Emergency Drill for your unit? 4. Where and why do you report an accident?

Cadet Objectives

Know how to reduce the risk of personal accidents (both mechanical and electrical). Identify the various items of personal protective equipment, and know when and how they should be worn.

Course Notes _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


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Introduction to Marine Engineering

3 ME 3

History of the internal combustion engine During the 19th century the steam reciprocating engine was developed. These were crude engines which had poor efficiency, were temperamental and used a lot of labour. By the late 1880s they were widely used in transport on land and sea and in industry. The power was introduced into the engine in the form of steam which necessitated the use of a boiler and auxiliary pumps, requiring a lot of space. At this time scientists and engineers throughout Europe were obsessed with the idea of power that could be created within the cylinder itself. If this could be achieved the steam power unit could be dispensed with. Many problems faced these men, changes in design to withstand the high temperatures and pressures inside the cylinder; suitable fuels to bring about the power required and countless others. Working independently and yet with a common aim these men gradually found the answer to their problems and by 1900 had succeeded. Research followed two definite lines of thought and from these the Spark Ignition Engine and the Compression Ignition Engine were designed. Development of the internal combustion engine

1770 First steam carriage – Cagnot, French. It kept turning over at corners. 1794 Crude Gas Engine – Robert Steel, English. 1801 Gas Engine from wood – Lebon d’Humberstien, French. Basic 2 stroke. 1805 First Internal Combustion Engine vehicle. Voltaic spark, kick open exhaust –

Issac de Rivaz, Swiss. 1826 Forty litre Gas Engine. Poor power/weight ratio – David Gordon. 1858 First proper 2 stroke. Coal gas using platinum spark plug – Joseph Lenoir

Belgium. 1877 Niklaus Otto tried to patent the 4 stroke but Karl Benz fought the patent, and

in 1886 the patent was made invalid and Benz was in charge of the 4-stroke development. The actual designer of the 4 stroke was Otto’s Chief Engineer – Gotlieb Daimler. (Hence the Daimler cycle).

1884 Engines were mass produced by Benz. 1892 Rudolph Diesel designed a heat engine. (Compression Ignition Engine). 1897 First Great British Diesel Engine – Mirlees. 1900 Engines followed two paths – Spark Ignition Engine (SIE) and Compression

Ignition Engine (CIE).


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The different types of engine Steam Engines – These can be reciprocating or rotary (turbine). They require a boiler and auxiliary pumps to provide the power, and could be described as external combustion engines, taking up much more space than internal combustion engines. Gas Turbines - These are high powered, expensive and are used to power modern major warships, trains and aircraft. They are not piston engines and are not covered by the course. Internal Combustion Piston Engines (ICPE) – This term covers both the Spark Ignition Engine and the Compression Ignition Engine. Spark Ignition Engine (SIE) – In the spark ignition engine an easily vaporised fuel, normally petrol is mixed with air and is ignited by an electric spark at the end of the compression stroke. This is the basic motor car engine or outboard motor. Compression Ignition Engine (CIE) – In this engine a fuel of a much higher flash point is used, giving a much higher safety factor. The fuel is ignited by the high temperature of the air at the end of the compression stroke. When the air is compressed in the cylinder, by the piston, to several hundred degrees, fuel is injected as a fine spray into the cylinder. This engine is the basic diesel engine fitted in some cars, vans, lorries and most small boats. Diesel engines are used because they are economical, self contained and are more efficient than petrol engines, are generally cheaper to maintain, and their fuel is less hazardous than petrol.

Internal Combustion Piston Engines

Spark Ignition Engines (Petrol) Compression Ignition Engines (Diesel)

Steam Engines Gas Turbines

HEAT ENGINES


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Types of movement There are two types of movement that can transmit power – reciprocating and rotary. They transmit power from the piston through the engine to the shaft and propeller. Reciprocating Movement - Movement in up and down motion. An example is the piston moving from the top of the cylinder to the bottom of the cylinder. Rotary Movement – Movement in a circular motion. An example is a propeller shaft. In a piston engine, both rotary and reciprocating movements are used to convert power from the engine to the propeller. Main components of a basic piston engine Engines may vary considerably but the majority incorporate the components listed below. These components will be covered in more detail in the next Section, 3ME4 -Engine Construction. 1. Cylinder block and crankcase. The unit forms the principal part of the

engine. It may be cast as a single unit, or the cylinders may be detachable from the crankcase.

2. Cylinder head. The head, usually detachable, is bolted to the cylinder block

and forms a gas tight and water tight ‘lid’ on each cylinder. 3. Sump. This is a light casing fitted to the underside of the crankcase to

contain the lubricating oil. 4. Piston. The piston is a sliding fit in the cylinder bore. It is fitted with piston

rings to prevent gas leakage past the piston. The top of the piston is known as the crown. The lower part, which acts as the guide is called the piston skirt.

5. Connecting rod. The connecting rod is attached to the piston at one end by a

gudgeon pin which is fitted to the piston. This is known as the Little End. The bottom end of the connecting rod is attached to the crankshaft, at the Big End Bearing.

6. Crankshaft. The crankshaft is carried in main bearings which are part of the

crankcase casting. It converts the reciprocating movement of the piston to more useful rotary movement.

7. Flywheel. Most internal combustion piston engines have a heavy flywheel to

carry the engine over the non-power strokes, particularly in the four-stroke engine where there is only one power stroke in four on each piston. The flywheel is attached to the crankshaft, and is outside the crankcase.


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8. Valves. The valves are usually fitted in the cylinder head, and are called overhead valves. When open they allow the passage of Air, Fuel, and Exhaust gas, when shut they seal the cylinder.

9. Camshaft. Each valve is lifted by a cam, which is pear shaped and machined

in an angular position on the camshaft so that it will lift the valve for the correct period.

10. Rocker gear. Overhead valves are operated by rockers with one end of each

rocker bearing on the cam or push rod, and the other end on the valve stem.


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Questions : 3 ME 3 1. Who invented the Compression Ignition Engine? 2. What do the letters SIE and CIE stand for? 3. Explain the different types of movement in the piston engine. 4. What is a disadvantage of a steam engine? 5. Name two advantages of a diesel engine.

Cadet Objectives Describe the main differences between petrol and diesel engines.

Course Notes _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


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Engine Construction

3 ME 4

General Arrangement of a Diesel Engine Diesel engines have an infinite number of jobs to carry out and are, therefore, of many various shapes and sizes. From simple single cylinder engines to multi-cylinder engines however, the basic components remain the same.


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The main components Engines may vary considerably but the majority incorporate the components listed below. 1. Cylinder block and crankcase. The unit forms the principal part of the

engine. It may be cast as a single unit, or the cylinders may be detachable from the crankcase. A water cooling space is included in the cylinder block. Small air cooled engines have fins to provide a large surface area for the cooling air.

2. Cylinder head. The head, usually detachable, is bolted to the cylinder block.

In some small two-stroke engines, however the cylinder head is part of the cylinder and can not be detached. A water cooling space in the head communicates with the water cooling passages in the cylinder block. Air cooled types incorporate fins, as in the cylinder block.

2. Sump. This is a light casing fitted to the underside of the crankcase to

contain the lubricating oil. This is normally OMD (oil mineral detergent), or a commercial equivalent.

3. Piston. The piston is a sliding fit in the cylinder bore. It is fitted with piston

rings to prevent gas leakage past the piston. The top of the piston is known as the crown. The lower part, which acts as the guide is called the piston skirt. Compression rings are fitted to maintain a seal between the piston and the cylinder wall and an oil control (scraper) ring removes excess oil from the cylinder wall.

4. Connecting rod. The connecting rod is attached to the piston at one end by a

gudgeon pin which is fitted to the piston. A bush in the end of the connecting rod provides a bearing surface. This is called the small end bearing. The bottom end of the connecting rod is attached to the crankshaft, with a halved bearing and bottom cap securely bolted to the connecting rod. This is called the big end bearing.

5. Crankshaft. The crankshaft is carried in main bearings which are part of the

crankcase casting, with halved bearing shells and bottom caps securely bolted to the crankcase.

6. Flywheel. Most internal combustion piston engines have a heavy flywheel to

carry the engine over the non-power strokes, particularly in the four-stroke engine where there is only one power stroke in four on each piston. The flywheel is attached to the crankshaft, and is outside the crankcase, but sometimes it is enclosed by the clutch case, or the reversing gear case. The flywheel usually incorporates a toothed ring into which the engine starter pinion engages to start the engine.

7. Valves. The valves fitted to all four-stroke engines and some to two-stroke

engines are mushroom-shaped. They have a long stem, over which a spring is installed to hold the valve on the seating. The valves are usually fitted in the cylinder head, these are called overhead valves.


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Engine components cont… 8. Camshaft. Each valve is lifted by a cam, which is pear shaped and machined

in an angular position on the camshaft so that it will lift the valve for the correct period. The camshaft may lie above the cylinder head, when it is called an overhead camshaft, or alongside the crankshaft with push rods to lift the valves if they are of the overhead type.

9. Rocker gear. Overhead valves are operated by rockers with one end of each

rocker bearing on the cam or push rod, and the other end on the valve stem. Side valves are usually placed immediately above the cams so that the rockers are not required.

10. Tappets. All valve gear is fitted with tappets, a form of set screw and lock-

nut, which may be fitted to the rockers, the push rods, or the tappet spindle for side valve engines. The tappets are adjusted to give a slight clearance for expansion between the tappet and the valve stem. This clearance is always stated for inlet and exhaust valves of each engine.

OVERHEAD VALVE GEAR


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11. Timing gear. The camshaft must be accurately timed to the crankshaft so that

the valves will open when required and for the correct period. The timing gear consists of gear wheels usually mounted at the front end of the crankcase and enclosed by a timing case. The gear wheels are marked to show the correct setting.

12. Fuel pump and injectors. The fuel injection pump may be fitted on the side

of the engine, or an individual fuel injection pump may be fitted alongside each cylinder. The pump is driven by the timing gear so that fuel is injected into each cylinder at the correct time. Each cylinder head is fitted with an injector, which consists of a non-return valve and a nozzle which produces a fine spray of fuel into the cylinder. The speed of the engine is varied by a governor which controls the quantity of fuel discharged by the fuel pump.

13. Joints/Gaskets. These are fitted to prevent the leakage of oil, gas or water.

The cylinder head gasket is normally made from copper and compressed fibre, whilst other joints are of treated paper or metal-to-metal with joining compound between the mating faces.


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Questions : 3 ME 4

1. What is a camshaft? 2. What is a crankshaft? 3. Name the two bearings associated with the connecting rod. 4. What is the purpose of the flywheel and what is the starter ring for? 5. Name two parts of a piston. 6. On a six cylinder diesel engine how many injectors are fitted? 7. Show your instructor the main parts of the diesel engine on your unit’s diesel,

or on a diagram of a diesel engine.

Cadet Objectives 1. Identify all major components and understand their purpose. 2. Know the function of a gasket.

Course Notes

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Engine Cycles

3 ME 5

The Four Stroke Cycle The four-stroke cycle is so called because there are four distinct parts to each complete cycle. The cycle keeps the piston moving upwards and downwards and the crankshaft revolving, and the sequence is as follows: The Induction Stroke – The piston is moving down the cylinder and sucking in clean air through the air inlet filter, down through the inlet manifold and into the cylinder, via the inlet valve. The inlet valve has opened for this specific operation and closes when the piston is at the bottom and the cylinder is full of clean air.


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The Compression Stroke – The piston is now moving back up the cylinder, both the inlet valve and the exhaust valve are shut and no air can escape. The air is now being compressed (compression) and as this occurs it heats up. When the piston is at the top of the stroke and the air is at its most compressed state, diesel fuel is injected into the cylinder as a high-pressure spray.


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The Power stroke – The fuel and air mixture compressed within the cylinder, burn rapidly and expand, driving and forcing the piston down, producing the power.


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The Exhaust stroke – The piston travels back up the cylinder pushing all spent gases out of the opened exhaust valve, which closes when the piston reaches the top of its travel. The inlet valve then opens as the cycle starts again.

The power produced is, in part, directly related to the volume of the cylinders, although other factors enhance performance. It is the amount of fuel/air burnt that produces the power. Combustion (the fire triangle) – All internal combustion engines require Heat, Fuel and Air for combustion. Combustion takes place when energy is released by the atomising of the fuel under pressure and bringing it into contact with the high temperature of the compressed air. This mix of fuel, air and heat causes an increase in temperature and pressure in the top of the cylinder. The ignition and expansion that occur will push the piston downward.


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The Two Stroke Cycle The exhaust valve opens much earlier in the power stroke than in the case of the 4-stroke cycle. With the piston still descending inlet ports cut into the base of the cylinder walls are uncovered. Air enters the cylinder until the piston again covers the inlet ports as it ascends. The exhaust valve has by this time closed so that a charge of air is trapped in the cylinder. The piston continues to rise, compressing air until just before the top of the stroke when the fuel is injected. The fuel is ignited by the heat of compression and the burning gases drive the piston down in the power stroke.

NOTE: THE CRANKSHAFT WILL ROTATE TWO REVOLUTIONS TO

COMPLETE ONE FULL CYCLE IN THE 4-STROKE CYCLE AND ONE REVOLUTION IN THE 2-STROKE CYCLE.


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Questions : 3 ME 5

1. When the piston moves down during the power stroke is: a) The exhaust valve open or shut? b) The inlet valve open or shut? 2. When the piston travels back up the cylinder after the power stroke is: a) The exhaust valve open or shut? b) The inlet valve open or shut? 3. How many revolutions will the crankshaft do during one full cycle of a

4-stroke cycle engine?

Cadet Objectives 1. Know the three elements of combustion. 2. Know the 2 and 4 stroke cycles. 3. Describe the relative positions of pistons at each stage of the cycle.

Course Notes _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


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Mechanical Systems

3 ME 6

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. 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. Tank Filling Tank drain

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

Tank

Pump Filter

System


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Beware of filling the wrong tank with the wrong fluid. Your instructor will show you how to replenish correctly all the engine levels. The system pressure can be monitored using a pressure gauge. Oil, water and fuel levels are always checked prior to starting the engine. 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. Lubricating oil system The lubrication system will supply clean oil under pressure, from the sump to the engine bearings, gears and rocker gear. 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.

BASIC DIESEL ENGINE LUBRICATION SYSTEM

Oil in

Oil pump

Oil filter

Top endvalvegear pushrods

Camshaft

Crankshaftbearings

Timing gears

Sump

Oil pressure gauge

Dipstick


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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.

BASIC DIESEL ENGINE FUEL SYSTEM

Cooling systems 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 head’s 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. 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.

Fuel tank

Main filter

Liftpump

Fine filter

Injection pump Injector

Fuel in Leak off lines


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Cooling systems (contd)

DIRECT OR RAW WATER COOLING

INDIRECT OR FRESHWATER COOLING

Sea Cock

Strainer Waterpump

Oil Cooler

Engine block

Exhaust manifold

Directly attached to the engine

Sea Cock

Strainer Seawaterpump

Oil Cooler

Thermostat

Directly attached to the engine

Engine cylinder head & block

Header Tank

& Heat

exchanger

Freshwaterpump

Exhaust manifold


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Questions : 3 ME 6 1. Name the three main systems fitted to a diesel engine. 2. How would you check the oil level of a diesel engine? 3. What are the main components of any basic system? 4. Why are systems checked before and after starting?

Cadet Objectives 1. Describe the purpose of each of the mechanical systems, and the medium used

by each system.

Course Notes _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


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Electrical System

3 ME 7 The main electrical system components Electrical systems fitted in a SCC power boat may vary slightly, but the majority would include: (a) Battery - This provides the stored electrical energy for the electrical system. It

is usually a lead/acid type. It will be covered in detail in 3 ME 9.

(b) Starter Motor - This is fitted with a pinion which engages with a toothed rim on the flywheel to turn the engine. As soon as the engine starts, it over-runs the pinion and causes it to disengage. The starter can be either a pre-engaged starter or an inertia type starter motor.

The starter motor is connected to the battery via a switch. When the switch is closed, current passes to the field coils and causes their soft iron cores to become magnets, whilst at the same a second magnetic field is formed in the armature. The interaction between these two magnetic fields causes the armature to rotate. The shaft on the armature has a mechanism to turn over the flywheel, such as a solenoid or spring loaded pinion, which then drives the flywheel. When the engine has started the solenoid/spring mechanism disengages the pinion from the flywheel.

(c) Alternator/Dynamo - This charges the battery, and is driven by a belt off the

engine. The rotating internal parts generates electricity and send it to the battery which will continually charge whilst the engine is running. If there is a heavy demand on the battery, it will discharge its charge, and render the starting circuit inoperable when the next attempt to start the engine is made. A small red light or negative indicator on the engine start panel will indicate if the system is not charging.

(d) Voltage Regulator - This regulates the voltage at 12 volts, and is a usually a

sealed component. (e) Wiring loom - Electricity is transferred from the different electrical

components through terminals to this loom of insulated wires. The wires are colour coded to identify which components supply each other. The wiring loom is earthed at various points to prevent components becoming live, to reduce the chance of electrocution or electric shock.

(f) Fuses - These protect the various components and electrical circuits from

electrical defects. Fuses are coded by colour and must be the correct size for the circuit. The different types of Fuse will be covered in Class 2.


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BASIC DIESEL ENGINE ELECTRICAL SYSTE Materials used in electrical components Insulators: Materials which don’t allow current to

eg. Plastic, wood, air, rubber, glass. Conductors: Materials which allow current to flow

eg. Metal, water, carbon.

Starter switch

Starter motor

- +Battery

Solenoid

Generator Navigation lights, horn,

VHF etc.

Bilge pumps &Alarm systems

M

f

fr

Distributionboard

Battery isolator switch

low freely. (High resistance).

eely. (Low resistance).


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Questions : 3 ME 7 1. What is the source of power for the electrical system? 2. Identify the major electrical components in your unit motor boat 3. Explain why the electrical system uses a dynamo/alternator? 4. What are the dangers of electrical circuits? 5. What is the function of fuses in the electrical system?

Cadet Objectives

Identify all major electrical components and understand their purpose Provide examples of insulators and conductors

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Basic Electrical Knowledge

3 ME 8

Simple Circuits A circuit is the combination of several electrical components that when connected together and provided with a power source will cause an action of some kind. This action will be in the form of light, movement, heat or noise. A basic circuit will comprise of:- Electrons. Current is the movement of electrons through a material. Before a current can flow in a conductor there must be an applied voltage. This can be produced by chemicals, heat, light, friction, pressure and by magnetism. Conventional current flow is from positive to negative. Current. Is the movement of free electrons, current is measured in Amps. Voltage. Voltage is an electromotive force (or potential difference) measured in

volts.

Resistance. Resistance is measured in Ohms and depends on temperature. Ohms Law. At a constant temperature, the steady current flowing through any conductor is directly proportional to the potential difference across its ends. I = V R Where I is current (amps) V is voltage (volts) R is resistance (ohms) Your instructor will demonstrate Ohms law and show you how to calculate the different methods of calculating voltage, current and resistance. Electrical circuits can be measured using a multimeter which will carry out the following tests.

a) Continuity. b) Measure voltage. c) Measure resistance. d) Measure current. e) Test a fuse.


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Simple circuits (contd.) There are two types of electrical circuits, and both are used for different applications. Series Is when components are connected one after another (similar to Christmas

tree lights) and they all share the current equally. If one of the components fail, the circuit will fail.

Example of a circuit in series

Parallel Is where each component has its own circuit, and if one component fails the

others will continue to work.

Example of a circuit in parallel


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Questions : 3 ME 8

1. In which direction does current move? 2. Explain Ohms Law in your own words. 3. What is the difference between series and parallel?

Cadet Objectives 1. Construct a circuit to demonstrate series and parallel connections. 2. Carry out practical measurements of current, voltage and continuity. 3. Demonstrate an understanding of Ohms Law.

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Power Generation

3 ME 9

Generators A generator is used to convert mechanical rotating energy into electricity. The generator is driven by a belt, which connects the engine crankshaft and the generator rotor. The electricity generated is discharged to the electrical system. This belt driven rotor is turned within the generator, and is surrounded by opposing magnets that have been wound with wire. This rotating movement within the magnetic field generates electricity.

TYPICAL MOTOR BOAT GENERATOR

Electrical current Electrical current is the movement of electrons through a conductor, they are moved by an electromotive force (emf), it is measured in volts, this will have been demonstrated in 3 ME 8 using the multimeter when making electrical circuits.


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Batteries These can be wet, dry or gel type cells.

The wet cell (secondary cell) is a container which has plates of different materials that are submerged in electrolyte. A chemical reaction takes place between the plates and positive particles migrate through the electrolyte to the negative plate. A circuit is made between the plates and this will continue until the electrolyte has been expended. This type of battery is normally used for motor boats. The dry cell (primary cell) is made of a carbon rod surrounded by manganese dioxide with an electrolyte of ammonium chloride. The cell is sealed and is activated when connected to a circuit, such as a torch. Different chemicals can be used, but the principal is the same. The average voltage from the cell is 1.5 volts.

The gel cell is a sealed unit which has been constructed similarly to the wet cell. The electrolyte is contained within the unit and cannot be opened. The battery will only last a limited lifetime, where upon the battery has to be replaced. This type of battery is now fitted in most new cars. A number of cells connected together in series is called a battery. The usual output would be 12 volts for a SCC motor boat. Primary cells cannot be recharged; secondary cells are rechargeable. Battery Maintenance

WARNING: BATTERY CHARGING OR ANY OTHER FORM OF BATTERY MAINTENANCE MUST ONLY BE CARRIED OUT UNDER CLOSE ADULT SUPERVISION

When checking batteries, personal protective equipment must be worn. This includes goggles, gloves and an apron. A battery hydrometer must be used to check the specific gravity of the battery, for a lead acid type the reading should be 1.230 to 1.260. If using a Nickel cadmium type the reading will be 1.160 to 1.230. A discharged cell will read 1.18 or less on the hydrometer. The readings should be taken at a cell temperature of 20 degrees C. Should the electrolyte need to be replenished, distilled water should be used, and filled to just above the plates.

Batteries must be charged in a well-ventilated area with the plugs removed from the top of the battery. There must be No Smoking or naked lights when charging as batteries discharge hydrogen which is an explosive gas. Battery terminals should also be checked for tightness and never make contact between the positive and negative terminals as this will complete a circuit. Battery terminals should be kept clean and protected with petroleum jelly (Vaseline), to stop corrosion products building up.


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Questions : 3 ME 9 1. Explain how electricity is generated for a motor boat. 2. What is the difference between a primary cell and a secondary cell? 3. Why must battery charging take place in a well ventilated area? 4. What are the SAFETY rules when working with batteries? 5. Why are battery terminals kept clean and protected?

Cadet Objectives

Describe the various methods of power generation Demonstrate the use of a hydrometer and personnel protective equipment when checking the condition of a battery.

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Tools and Fasteners

3 ME 10

Common Workshop Tools The following tools and fasteners are an example, you may have others which you use frequently which are not covered here:. Check your tools for worn and broken parts, before they are used. An example would be a hammer that has a broken or damaged shaft, the head securing pin may be missing or loose. Files and screwdrivers must have handles fitted. Beware of using excessive force, and the hazards to health when not using the correct tools. Understand the correct way to tighten and loosen a nut. Clockwise to tighten and anti-clockwise to loosen a nut. Soldering Irons should be used under the supervision of a qualified instructor. Measuring tools are expensive and should be used with care. Scribers and calipers should not be used for poking dirt out of holes, or skylarking. They are precision instruments and should be treated as such. Multimeters are expensive and should be used with care. Never skylark with this instrument as used incorrectly it could give you an electric shock. There are many different types of tools and different types of fasteners, some of which are listed below:

(a) Spanners Open ended, Ring, Adjustable, Box and Combination. (b) Sockets Various sizes, Metric and Imperial. (c) Screwdrivers Cross-head, Flat-head. (d) Hammers Mallet, Ball-pein and Claw. (e) Allen Keys Metric and Imperial. (f) Pliers Long-nosed, Side-cutting. (g) Hacksaw Standard and Junior. (h) Files Half-round, Triangular and Flat. (i) Fasteners Nuts, Bolts, Washers and Connections. (j) Soldering Iron Electrical (l) Multimeter Electrical


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Fasteners and Gaskets (a) The termination and connection of electrical wiring should be done with pliers

and suitable connections. It is important to prevent loose connections that could earth or short the electrical circuit, or may even start a fire.

(b) Gaskets are pre-formed or can be made from commercial gasket material.

Most diesel engine gaskets are now compressed fibre and copper, fitted to prevent the leakage of oil, gas or water. Some joints may be metal-to-metal with jointing compound between the faces.

(c) Fasteners – You should be able to recognise and remove/replace nuts, bolts, washers, screws, clips, split pins and common fasteners.

When a project has been completed, return your tools and ensure that the working area is left in a clean and tidy condition. All surplus

items are to be properly disposed of.


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Questions : 3 ME 10 1. Describe what checks you would carry out on tools for before using them. 2. Demonstrate how electrical connections are checked for security. 3. Why is it important to use the right tool for the right job? 4. Why is it dangerous to use a file without a correctly fitted handle?

Cadet Objectives

1. Demonstrate an understanding of the correct use of standard mechanical

and electrical tools. 2. Show how awareness of the correct way to loosen and tighten fasteners,

and the likely hazards to health when not using the correct tool.

Course Notes

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The Sea Cadet Corps

Marine Engineering Specialisation

Progress Chart for Class 3

Lesson Instructor Date 3 ME1 Health & Safety

3 ME 2 H & S - Workshop

3 ME 3 Introduction

3 ME 4 Engine Construction

3 ME 5 Engine Cycles

3 ME 6 Mechanical Systems

3 ME 7 Electrical System

3 ME 8 Basic Electrical

3 ME 9 Power Generation

3 ME 10 Tools & Fasteners

3 ME 11 Practical Projects

Revision period

Examination

Notes: 1. Apply to your ASO(ME) who will supply an authorised examination paper. 2. SCC form T7(MarEng) to be signed by CO and forwarded to ASO(ME) on

completion of the examination.


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Marine Engineering Third Class Study Guide and Training Manual

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Transcript of Marine Engineering Third Class Study Guide and Training Manual