Basic Marine Engineering

Transcript

CHAPTER 01 STRUCTURE AND ORGANIZATION OF ENGINEERING DEPARTMENT 1. Organization – An organization is a social entity that has a collective goal and is linked to an external environment (a compartment for a particular task). 2. Structure – The typically hierarchical arrangement of lines of authority, rights and duties of an organization. Organizational structure determines how the roles, power and responsibilities are assigned, controlled, and coordinated, and how information flows between the different levels of management. 3. Organization structure of marine, ship wright & automobile engineer officers – Naval Head Quarters. 1 සීමාන්විතයි DGE – Director General Engineering DME – Director Marine Engineering DAE – Director Automobile Engineering DES – Director Engineering Services DHR – Director Hull Repairs DDME (A&O) – Deputy Director Marine Engineering (Auxiliary and Offshore) DDME (F&I) – Deputy Director Marine Engineering (FAC and Inshore) DDES – Deputy Director Engineering Services DDAE – Deputy Director Automobile Engineering DDHE – Deputy Director Hull Engineering SSEO (A&O) – Senior Staff Engineer Officer (Auxiliary and Offshore) SSEO (M&D) – Senior Staff Engineer Officer (Monitoring and Development) SSEO (NC) – Senior Staff Engineer Officer (New Construction) SSEO (QA) – Senior Staff Engineer Officer (Quality Assurance) SSEO (ADM) – Senior Staff Engineer Officer (Administration) SSEO (AM) – Senior Staff Engineer Officer (Automobile) SSHEO – Senior Staff Hull Engineer Officer MANAGER (IPCCP) – Manager (Inshore Petrol Craft Construction Project) SEO (Ref & AC) – Senior Engineer Officer (Refrigeration and Air Conditioning) SEO (NC) – Staff Engineer Officer (New Construction) SEO (FAC) – Staff Engineer Officer (Fast Attack Craft) SEO (M) – Staff Engineer Officer (Marine) SEO (R) – Staff Engineer Officer (Repair) SEO (ILMS) – Staff Engineer Officer (Integrated Logistics Management System) SEO (ADM) – Staff Engineer Officer (Administration) SEO (TRG) – Staff Engineer Officer (Training) SEO (AM) – Staff Engineer Officer (Automobile) SEO (D) I – Staff Engineer Officer (Design) I SPE (MECH) – Senior Project Engineer (Mechanical) SAEO – Staff Automobile Engineer Officer SPE (IPCCP) – Senior Project Engineer (Inshore Petrol Craft Construction Project) OIC (HVP) – Officer In Charge (Heavy Vehicle Pool) EO (M) – Engineer Officer (Maintenance) PE (IPCCP) – Project Engineer (Inshore Petrol Craft Construction Project) PE (M) – Project Engineer (Marine) PE (QA) – Project Engineer (Quality Assurance) PE (H) – Project Engineer (Hull) PE (M) MAW – Project Engineer (Maintenance) Malima Auto Works PE (BR) MAW – Project Engineer (Body Repairs) Malima Auto Works 2 සීමාන්විතයි 4. Duties and responsibilities of key appointments are as follows. a. Director Marine Engineering (1) (2) (3) (4) (5) (6) (7) b. Responsible to the Director General Engineering on all matters pertaining to Marine Engineering including Shipwright matters. Formulating plans and strategies in all Marine Engineering works. Forecasting Marine Engineering requirements. Recommending and monitoring all Marine Engineering purchases, refits of ships/craft. Ensuring effective and timely implementation of maintenance and repair scheduled to achieve optimum performance of SLN ships and Craft. Handling of appointments of officers in the Engineering Branch in consultant DGE. Direct and monitor the functions of Deputy Director Hull Engineering (DDHE) and advise DDHE in arranging and coordination of shipwright works related to Marine Engineering until Director Hull Repairs (DHR) is appointed. Director Engineering Services (1) (2) (3) (4) (5) (6) (7) (8) (9) Planning and forecasting departmental requirements on general engineering matters. Planning and forecasting of the cadre requirement of engineering branch. Selection of engineering personnel for special tasks and for training consultation. Formulating academic and Continuous Professional Development training requirements of Engineering branch personnel. Making views/recommendations for BOI reports on losses and damages to machinery, ships/craft and vehicle in consultation DME and DAE. Monitor progress of training of Engineering branch Officers and sailors local and abroad. Planning and forecasting departmental requirements on general engineering matters. Planning and forecasting of the cadre requirement of engineering branch. Selection of engineering personnel for special tasks and for training consultation. 3 සීමාන්විතයි (10) (11) (12) c. Director Automobile Engineering (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) d. Formulating academic and Continuous Professional Development training requirements of Engineering branch personnel. Making views/recommendations for BOI reports on losses and damages to machinery, ships/craft and vehicle in consultation DME and DAE. Monitor progress of training of Engineering branch Officers and sailors local and abroad. Responsible to DGE for all matters pertaining to Automobiles and transport system in SLN. Efficient and effective functioning of Automobile Department in SLN. Projection of annual vehicle machinery requirement and initiate purchasing action. Allocation of vehicles to meet SLN requirements. Maintaining of records on all Automobiles belonging to SLN including hired vehicles. Arrangement for registration/insurance of vehicles. Responsible for maintenance of vehicles in SLN. Preparing and scrutinizing of specifications of Automobile, Earth moving vehicles. Land vehicles and other machinery tools related to automobile field and initiating procurement action. Make recommendations on spares purchase/ repair files related to vehicle maintenance and forward for approval. Administration of warranty and contract repairs to Automobiles and machinery related to Automobile Engineering Workshop. Coordination of hiring of vehicles and services rendered from outside organization. Proposing improvements on infrastructure facilities, amendments to current regulations/ orders to improve departmental activities. Forecasting of man power requirements. Issuing of Service Driving License. Supervising of staff under DAE Department. Director Hull Repairs (1) (2) Responsible to DGE for efficient and smooth functioning of Shipwright Branch and to consult DME in arranging all kinds of repairs, related to Marine Engineering and maintenance schedule. Plan strategies of all shipwright matters. 4 සීමාන්විතයි (3) (4) (5) (6) (7) (8) 5. Forecast manpower, material and equipment requirement for Shipwright branch. Preparing all specifications for Shipwright branch requirements in SLN. Appointments and Training of officers of Shipwright branch. Drafting of sailors and Training of offices and sailors of Shipwright branch. Forecast, schedule and monitoring of slipping/ docking of shops & craft. Monitoring and quality controlling of IPCCP. Structure of marine engineering department – Eastern Naval Area CSD (E) – Commodore Superintendent Dockyard (East) CLD (E) – Commodore Electrical Department (East) DSD (E) – Deputy Superintendent Dockyard (Engineering) 5 සීමාන්විතයි MED (FAC) – Manager Engineering Department (Fast Attack Craft) MED (F&A) – Manager Engineering Department (FGB & Auxiliary) MED (YS) – Manager Engineering Department (Yard Support) MHED (E) – Manager Hull Engineering Department (East) CAEO (E) – Command Automobile Engineer Officer (East) SME (FAC) SQ – Senior Marine Engineer (Fast Attack Craft) Squadron SME (FAC) WS – Senior Marine Engineer (Fast Attack Craft) Workshop SME (FGB) – Senior Marine Engineer (Fast Gun Boat) SME (MV) – Senior Marine Engineer (Major Vessels) SME (DT) – Senior Marine Engineer (Dockyard Tender) SME (OBM) – Senior Marine Engineer (Out Board Motors) SME (AM) – Senior Marine Engineer (Auxiliary Machinery) SME (R&F) – Senior Marine Engineer (Refrigeration and Factory) SE (QA&T) – Senior Engineer (Quality Assurance & Training) SHE (DM&R) – Senior Hull Engineer (Dry Maintenance & Refit) SHE (WS) – Senior Hull Engineer (Work Shop) SHE (F) – Senior Hull Engineer (Fleet) ME (FAC) SQ – Marine Engineer (Fast Attack Craft) Squadron ME (FAC) WS – Marine Engineer (Fast Attack Craft) Workshop ME (FGB) SQ – Marine Engineer (Fast Gun Boat) Squadron ME (FGB) WS – Marine Engineer (Fast Gun Boat) Workshop ME (PC) – Marine Engineer (Patrol Craft) ME (UC) – Marine Engineer (Utility Craft) ME (HP OBM) – Marine Engineer (High Power) Out Board Motors ME (LP OBM) – Marine Engineer (Low Power) Out Board Motors ME (BG) – Marine Engineer (Base Generators) ME (MR) – Marine Engineer (Machinery Repairs) ME (Ref & AC) – Marine Engineer (Refrigeration and Air Conditioning) ME (F) – Marine Engineer (Factory) ME (QA&T) – Marine Engineer (Fast Gun Boat) ME (MTTU) – Marine Engineer (Machinery Trial & Testing Unit) HE (QA&T) – Marine Engineer (Quality Assurance & Training) HE (F) – Hull Engineer (Fleet) HE (RF) – Hull Engineer (Refit) HE (S) – Hull Engineer (Slipway) MTE (R) – Motor Transport Engineer (Repairs) MTE (BR) – Motor Transport Engineer (Body Repairs) MTE (M) – Motor Transport Engineer (Maintenance) 6 සීමාන්විතයි CHAPTER 02 SI UNITS AND MEASURING INSTRUMENTS SI Unit 1. The International System of Units (SI) specifies, a set of seven base units of measure from which all other units of measurement are formed, by products of the powers of base units. The International System of Units consists of a set of base units, a set of derived units, some of which have special names and a set decimal-based multipliers that are denoted as prefixes. 2. Base Units Name of the unit Meter Kilogram Second Ampere Kelvin Mole Candela Symbol Measure m kg s A K mol cd Length Mass Time Electric current Thermodynamic temperature Amount of substance Luminous intensity Derived Unit 3. Derived units are units which are deriving from SI base units. Following units are derived units from SI units. Name Square meter Cubic meter Meter per second Newton meter Meter Per second squared Kilogram per cubic meter Hertz Radian Newton Joul Pascal Symbol Quantity m2 m3 m/s Nm ms-2 kg/m3 Hz Rad N J Pa Area Volume Velocity Torque Acceleration Mass density Frequency Angle Force Energy Pressure 7 සීමාන්විතයි Expression in terms of SI units m2 m3 ms-1 kgm2 s-2 ms-2 kgm-3 s-1 Dimensionless kgms-2 kgm2 s-2 kgm-1s-2 4. The names of SI units are always written in lowercase. The symbols of units named after persons, however, are always written with an uppercase initial letter (e.g. the symbol of hertz is Hz; but meter is m). 5. Conversions Measurement Length Area Volume Mass Non-SI unit Inch (in) Foot (ft) Yard (yd) Mile Square Inch (in2) Square Feet (ft2) Hectares (ha) Cubic Inch (in3) Cubic Feet (ft3) Gallon UK Ounce (oz) Pound (lb) Metric (SI) unit Millimeters (mm) Centimeters (cm) Meters (m) Kilometers (km) Square Millimeters (mm2) Square Centimeters (m2) Square Kilometers (km2) Cubic Millimeters (mm3) Cubic Meters (m3) Liters (l) Grams (g) Kilograms (kg) Conversion 1 in = 25.4 mm 1 ft = 30.48 cm 1 yd = 0.914 m 1 mile = 1.609 km 1 in2 = 645 mm2 1 ft2 = 929 cm2 1 ha = 0.01 km2 1 in3 = 16387 mm3 1 ft3 = 0.028 m3 1 gal = 4.55 l 1 oz = 28.35 g 1 lb = 0.45 kg Measuring Instruments 6. Measuring instrument is a device for measuring a physical quantity such as the extent or amount or degree of something. Established standard objects and events are used as units (US, UK or Metric) and the process of measurement gives a number relating the item under study and the referenced unit of measurement. Calliper 7. A calliper is a device used to measure the distance between two symmetrically opposing sides. It can be used with inward or outward-facing points to measure either directly or indirectly as measuring transferring tool. Outside Calliper 8. Bowlegged outside callipers which clear the work are used to take outside measurements. Two kinds of callipers are available: firm jointed calipers, which are free to move but are held firmly in any position by friction or spring-jointed calipers which are controlled by a knurled nut on a threaded rod. The tips of the calliper are adjusted to fit across the points to be measured and then measuring distances by a ruler. 8 සීමාන්විතයි Inside Calliper 9. Inside calipers are available in the same size range as outside callipers. They have straight legs, turned out at the top and are used to take inside measurements. They are available with firm or spring joints. As with outside callipers, it is possible within limits to measure external dimensions with firm joint inside callipers. The tips of the calliper are adjusted to fit across the points to be measured, the calliper is then removed and the distance read by measuring between the tips with a measuring tool, such as a ruler. Odd Leg Calliper 10. These are generally used to scribe a line a set distance from the edge of a work piece. The bent leg is used to run along the work piece edge while the scriber makes its mark at a predetermined distance, this ensures a line parallel to the edge. Some has a slight shoulder in the bent leg allowing it to sit on the edge more securely and other has a renewable scriber that can be adjusted for wear, as well as being replaced when excessively worn. Divider Calliper 11. Divider callipers have a small knurled spigot to facilitate the scribing of circles. Adjustment is made by means of a knurled nut on a threaded rod. Dividers normally have two identical flat legs with hardened points. They are sometimes fitted with removable points which can be adjusted for equal length and be replaced when worn. Vernier Calliper 12. The vernier caliper, named after its inventor, is a development of the slide caliper, but is graduated to make finer readings. It is capable of measuring internal and external dimensions and can also be used as a depth gauge. Vernier calipers are available with imperial and metric graduations. The vernier, dial, and digital calipers give a direct reading of the distance measured with high accuracy and precision. These calipers comprise a calibrated scale with a fixed jaw, and another jaw, with a pointer, that slides along the scale. 9 සීමාන්විතයි Vernier Scale 13. A Vernier is a mechanical means of magnifying the last segment on the main scale so addition subdivisions can be made. The reference point is the „0‟ on the vernier scale. To read a vernier, the line of coincidence must be located. The line of coincidence (LOC) is the line on the Vernier that coincides with a line on the main scale. Micrometer Calliper 14. Micrometers are designed to produce the extremely fine measurements required in engineering, so that parts of a machine will meet with the minimum tolerance. The micrometer is used with different types and sizes of frames to provide precise measurements of many different objects. It is a caliper using a calibrated screw for measurement, rather than a slide. 10 සීමාන්විතයි 15. There are micrometers for measuring depth, inside dimensions and most commonly outside dimensions. The micrometer has a U-shaped frame with an anvil on one side and an adjustable spindle extending from the other. The knurled thimble adjusts the spindle to the required setting, which is then fixed by the lock nut. A ratchet stop is sometimes fitted to the end of the spindle. If the ratchet is used to adjust the spindle it will click or slip when the anvil and spindle contact with the work. Reading Micrometer 16. Micrometer calliper is read at the point where the edge of the thimble crosses the barrel scale and the last step of measuring is reading the value on the thimble scale. 17. The latest development in micrometers is expensive, but extremely easy to use. When the spindle and anvil come in contact with the work piece, the measurement can be read directly from a digital display. It is very accurate and does not involve the computations needed by a standard micrometer. 18. There such as, a. b. c. d. e. are different types of micrometers available which used for different purposes Outside Micrometer - Typically used to measure wires, shafts, blocks etc. Inside Micrometer - Used to measure the inside diameter of holes. Depth Micrometer - Measures depths of slots and steps. Bore Micrometer - Typically a three-anvil head on a micrometer base used to accurately measure inside diameters. Tube Micrometer - Used to measure the thickness of tubes. 11 සීමාන්විතයි CHAPTER 03 HEAT ENGINE Definition of Heat Engine 1. It is a device, which transforms the chemical energy of a fuel in to thermal energy and uses this energy to produce mechanical work. This means there are two processes involved, a. b. Transforming chemical energy of fuel into heat energy Using this heat energy do mechanical work External Combustion Engine (ECE) 2. The energy developed by combustion process, transfer in to a secondary medium which produce mechanical power. An EC engine is a heat engine where an (internal) working fluid is heated by combustion in an external source, through the engine wall or a heat exchanger. The fluid then, by expanding and acting on the mechanism of the engine, produces motion and usable work. Example: Steam Engine, Steam Turbine plant. Internal Combustion Engine (ICE) 3. Chemical energy is converted in to heat energy and heat energy in to mechanical power. An IC engine is a heat engine in which the combustion of a fuel occurs with an oxidizer (air) in a combustion chamber. High-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine, such as pistons, turbine blades, or a nozzle. This force moves the component and generating useful mechanical energy. Example: Petrol, Diesel Engines and Gas Turbine. 4. Advantages of ICE over ECE a. b. c. d. e. f. g. Mechanical simplicity High power to weight ratio Lower initial cost Less requirement of water Less bulky Higher overall efficiency Low maintenance 5. External combustion engine has one major advantage over IC engine is it can use cheaper fuel including solid fuel. Therefore they are used where cost of power is more important than size of plant. 12 සීමාන්විතයි Basic components of an IC engine 6. Basic components of an IC engine are as follows. a. b. c. d. e. f. g. h. j. k. l. m. n. p. q. r. s. Crank shaft Cam shaft Piston Connecting rod Fly wheel Rocker arm Push rods Piston rings Bearings Inlet & exhaust valves Timing gears and wheels Cylinder head Cylinder liner Cylinder block Crank case Oil sump Spark plug / fuel injector Two and Four Stroke Engines 7. Based on working cycle of an IC engine, it can be divided into two main types. a. Four stroke working cycle b. Two stroke working cycle Four Stroke Working Cycle 8. The following requirements are common to all internal combustion engines. a. Filling the cylinder with air or fuel-air charge b. Compressing this charge to generate high temperature and pressure. c. Burn the fuel to create the necessary rise in pressure to move the piston. d. Expelling the burnt gasses from the cylinder in order to draw in fresh charge to continue the working cycle. 9. These requirements can be met in the following ways by the provision of inlet and exhaust valves arranged to open and close in a special sequence and relative to the position of the piston in the cylinder. 13 සීමාන්විතයි 10. In a four stroke engine all the above requirements are met by four distinct strokes. a. Induction Stroke or Intake Stroke In this stroke the piston moves from TDC (Top Dead Center) to BDC (Bottom Dead Center). The inlet valve remains open and the exhaust valve remains closed. As the downward movement of the piston creates a vacuum atmospheric air is sucked in through the inlet valve. This continues till the inlet valve is closed after the piston reaches BDC. b. Compression Stroke At the end of the induction stroke both the valves are closed and the cylinder becomes gas tight. Therefore as the piston moves from BDC towards TCD the pressure of the air trapped inside rises rapidly due to reduction of volume. The heat created by the compression will be sufficient to ignite the fuel, when injected. c. Power Stroke Towards the end of compression stroke fuel is injected into the cylinder in atomized form. These fuel partials mixed with air inside the cylinder, absorb heat from it and ignite. The burning causes rapid increase in temperature and pressure inside the cylinder. This forces the piston towards the BDC. As useful power is developed during this stroke it is called power stroke. d. Exhaust Stroke during the power stroke all useful energy is extracted from the burning fuel-air mixture. In order to continue the cycle, fresh air is to be inducted into the cylinder. Prior to that the burnt gases in the cylinder are to be expelled. This is done during the exhaust stroke as the piston moves from BDC towards TDC. The exhaust valve is kept opened and the gasses pass through it to the atmosphere. At the end of the exhaust stroke the exhaust valve is closed. 14 සීමාන්විතයි 11. These four strokes occur continuously to develop continuous power. These strokes occupy two complete revolutions of the crankshaft. Therefore one power stroke is achieved for every two revolution of the crankshaft. Two Stroke Working Cycle 12. In this cycle induction, compression, power and exhaust are arranged to take place in two strokes of the piston, i.e. one revolution of the crankshaft. Ports cut into the cylinder walls are used instead of valves. These ports are opened and closed by the position of the piston. Exhaust ports are usually cut higher than inlet ports. Both the ports are cut towards the bottom of the cylinder. Compression Stroke (with Intake) 13. When the inlet port is uncovered a mixture of fuel and air is drawn inside the cylinder. During its upward travel the piston covers both inlet port and exhaust port making the cylinder gas tight. Therefore the charge in the cylinder gets compressed. Power Stroke (with Exhaust/Transfer) 14. This charge is the ignited by a spark (in SI engine). This causes a rise in temperature and pressure inside the cylinder forcing the piston towards BDC. When the piston uncovers the exhaust port exhaust gases are expelled from the cylinder under their own pressure. When the inlet port is uncovered fresh charge is inducted making the cylinder ready to continue cycle. Usually two stroke engines are spark ignited using petrol as fuel, but compression ignited two stroke diesel engines are also used. 15 සීමාන්විතයි 15. Comparison between two strokes and four strokes are as follows. FOUR STROKE ENGINE Cycle is completed in four stroke of piston/ two revolution of crankshaft. Heavy flywheel is needed due to turning movement is not uniform. Engine is heavy and bulky (for the same power). Higher weight-to-power ratio because it is much heavier. Low environment hazards. Less wear and longer engine life due to a good lubricating system. Used where efficiency is important. High fuel efficiency and mileage. Uses valves for inlet and exhaust. Thermal efficiency high. TWO STROKE ENGINE Cycle is completed in two stroke of piston/ one revolution of crankshaft. More uniform turning movement and lighter flywheel is needed. Engine is light and compact for the same power output. Lesser weight-to-power ratio because it is much lighter. Environment pollution is high. Faster wear and shorter engine life due to lack of lubricating system. Used where low initial cost, lightweight & compactness is involved. Low fuel efficiency and mileage. Uses ports for inlet and may use valves for exhaust. Thermal efficiency low. SI and CI Engines 16. IC engines can be divided into two basic types according to the method of ignition. a. Spark Ignition Engine – Fuel air mixture introduces to cylinders of the engine then compressed and ignited with the help of a spark generated by spark plug and starts the power stroke. (Petrol engines). b. Compression Ignition Engine – Air drawn into the cylinders and then compressed. At the end of compression stroke fuel is introduced and starts the power stroke (Diesel engines). 17. SI and CI engine comparison SI ENGINE Use Petrol, Gas and Kerosene as fuel. Spark plug required for firing. Use Carburetor to mix air & fuel. Carburetor control air/fuel mixture Load / speed controlled by controlling quantity of air-fuel mixture. CI ENGINE Use Diesel as fuel. Injectors required for firing. Injector use for fuel atomization. Injector pump control fuel amount. Load / speed controlled by quantity of fuel injected. 16 සීමාන්විතයි Usually consider as high speed engines. Low compression ratio. Light weight. Low cost. Good for low & medium power engines. Less noise. Less emission of polluted particles. Efficiency is low. Low fuel economy. Less reliability. Frequent maintenance required. Less torque. CO2 emission high. Higher exhaust temperature. Higher fire hazard. Lower operating life. Usually consider as low speed engines. High compression ratio Heavy weight High cost Good for medium & high power engines Noise is comparatively high High emission of polluted particles Efficiency is high High fuel economy High reliability Less maintenance High torque at low rpm CO2 emission low Lower exhaust temperature. Lower fire hazard. Higher operating life. Classifications of IC engines 18. IC engine can be classified into different types under following characteristics. a. Basic engine design (reciprocating, rotary) b. Arrangement of cylinders (inline, v-type, radial) c. Number of cylinders (single, multi) d. Method of ignition (spark, compression) e. Number of strokes or working cycle (two, four) f. Method of air intake (natural, supercharge, turbocharge) g. Type of fuel used (gasoline, diesel, gas) h. Fuel input method (injection, carburetion) j. Cooling (air, liquid) k. Application (automotive, marine, power generation) Systems of a Marine Diesel Engine Fuel System 19. The fuel oil used by all diesel engines in Navy is called LSHSD (Low Sulphur High Speed Diesel). Sulphur content is a very important property of the fuel. If the sulphur content is high it forms sulphur dioxide during combustion process. This sulphur dioxide may be absorbed by the moisture present in the incoming air to form sulfuric acid. This sulfuric acid is highly corrosive and result in excessive corrosion of piston, cylinder liner, valves etc. Therefore low sulphur content of fuel is essential. 17 සීමාන්විතයි 20. Quality of the fuel injected into the cylinder has a significant effect on the performance of engine. Benefits of using low sulphur diesel on the engine and the environment are as follows. a. b. c. d. e. f. g. Decreases corrosion in pistons and/or cylinder liner wear. Reduces maintenance costs. Increases overhauling duration (TBO). Potentially extends lubricant life. Reduces exhaust particulate and odor emissions. Reduces visible black smoke. Reduces sulphur oxide emissions which contribute to acid rain, will reduce the risk of acid rain occurring. System Components a. b. c. d. e. f. g. h. 21. Ready use tank Fuel separator Duplex filter Fuel feed pump Micro filter Fuel injection pump HP lines Injectors Function of marine fuel system a. b. c. d. e. Fuel stored at ready use tank. Fuel transferred to fuel injection pump by fuel feed pump. Before it enters to FIP, fuel gets filtered by fuel filters. Fuel injection pump deliver fuel to fuel injectors through high pressure lines according to firing order. Fuel injectors atomize fuel in to respective combustion chamber. 18 සීමාන්විතයි Fuel Hygiene 22. One of the most common factor affecting the quality of fuel is water particles mixing with fuel. Effects of water mixing with fuel are as follows. a. b. c. d. e. f. Loss of power Low peak pressure Low exhaust temperature Pitting on piston crown and liner wall Corrosion of parts of fuel injection system Uneven power / fluctuation in speed Lubrication System 23. Lubrication is an art of admitting a substance (which is softer) between two surfaces which are in contact and relative motion. It will reduce friction as well as wear from the surfaces. An IC engine has many metallic surfaces in close contact and moving against each other. Therefore the friction and resultant heat and wear down will damage the engine unless lubricated properly. Purpose of Lubricating System 24. Under system. a. b. c. d. e. f. g. 25. mentioned facts can be considered as essential purposes of lubricating oil To cool the surfaces by carrying away heat generated by friction. To reduced friction & wear, by continuous supplying of oil. To clean the surfaces by washing away carbon & metal particles caused by wear. To provide sealing effect. Example: lub oil helps the piston rings to maintain an effective seal against the high pressure gases in the cylinder from leaking in to crank case. To prevent corrosion. To reduce engine noise. To provide dampening effect. Basic Component a. b. c. d. e. f. Lub oil pump Lub oil filter Lub oil cooler Lub oil strainer Lub oil sump Breather 19 සීමාන්විතයි 26. There are three main types of lubricating systems associated with IC engines. a. Mist lubricating Used for 2 stroke engines where 2 to 3% of oil is added into fuel and the fuel/oil moisture is inducted through carburetor. As the gasoline is vaporized, oil in the form of mist goes via crankcase into the cylinder. Thus lubricates crank shaft, piston, piston rings & cylinder. This system is simple, low cost and no additional components like lub oil pump. b. Dry sump lubricating system The lub oil is not stored in the sump. As soon as the lub oil falls into the sump after lubricating various parts of the engine it is transferred to a circulating tank. There are two pumps used in the system. The pressure pump takes suction from circulating tank and discharge to gallery. The Scavenging pump takes suction from sump and discharge to circulating tank thus keeps sump dry. Advantages of this system are easy access to the crankcase fitting, low fire/explosion risk, smaller crank case resulting in smaller engine, reduced risk of contamination and economical. Main disadvantages are high cost and high maintenance cost. c. Wet sump lubricating system The oil required by the engine is contained in the sump at the lower part of crankcase. Pump draws oil from the sump through strainer, filter and the cooler. From the cooler, oil is supplied to the gallery and then to main bearings, big-end bearings via drilled passages in the crankshaft and to small-end bearings via drilled passages in the connecting rod. Tappings are taken from the gallery to cam shaft, rocker arms, timing gears, auxiliary drives and to cylinder walls through spray jets. The oil then drains back into the sump. The 20 සීමාන්විතයි advantages of this system are compact, self-contained and reasonably cheap. Main disadvantages are risk of crank case explosion and increase in crankcase size. Further this system can be sub divided into following categories. (1) Splash lubricating system Used in small engine, where sump level is maintained at high level. The dipper strike in the oil & splash on various parts of the engine. (2) Semi-pressure lubricating system In this system oil pump supply the oil with pressure to main bearings and cam shaft bearings lubrication and rest other parts are lubricated with the help of splash lubrication. (3) Full pressure lubricating system In this system engine driven oil pump supplies oil to the various engine parts (drilled internally) from where oil flows to piston ring, piston pin, cylinder walls. Oil is also supply to rocker arms, governor, fuel injection pump, water pump bearing etc. 27. Types of lubrication oil use in SLN a. b. c. d. e. f. j. k. Shell Gadinia 40 (SAE 40 grade) Shell Gadinia 30 (SAE 30 grade) Shell Rimula X 15 W 40 Shell Rimula Ultra 10 W 40 Caltex Lanka Super DS SAE 40 Caltex Lanka Super DS SAE 30 Quick Silver 2 Cycle Outboard Oil Caltex Super Outboard 3 Cooling System 28. In an IC engine only a part of the heat energy generated by the burning fuel is converted into mechanical work. Rest of the heat energy accumulates in the cylinder, piston and associated parts. If this excess heat is note removed it will lead to melting of the parts. Cooling system of an engine is designed to extract this additional heat and dispose it off so that the engine can operate continuously without failure of parts. 29. There are two types of cooling systems associated with IC engines. Generally only small engines use air as a cooling medium and not used in marine engines. In this system an engine driven fan forces a continuous airflow around the hot cylinder, cylinder head etc. In water cooled engines, water is circulated through jackets for cooling the parts. Two cooling circuits are used: 21 සීමාන්විතයි a. Primary Cooling Fresh water is usually used for primary cooling. In this fresh water pump takes suction from the system and discharges the water into the cylinder jackets. The water extracts heat from the cylinder, through jackets, during circulation. From the jackets the water rises through internal passages and reaches the cylinder head, exhaust manifold and then to fresh water cooler. An expansion tank is fitted to compensate for the water lost in the form of vapour. A thermostatic valve ensures certain minimum temperature of fresh water when the engine is in operation. Pressure and temperature gauges are fitted for efficient monitoring of the system. In engines where lub oil is cooled by fresh water, fresh water circulates through the lub oil cooler also. b. Secondary cooling As the fresh water circulates through the engine it gets heated up. This heat must be extracted from the fresh water before it is re circulated through the engine. The secondary cooling system is used for this purpose. In ships secondary cooling system uses seawater. But the radiator unit of an automobile also fulfills the same function. A centrifugal pump takes suction from the ship‟s sea water system and discharges it to the fresh water cooler. In the fresh water cooler heat is transferred from the hot fresh water to the cooler seawater. This seawater is then discharged overboard. 30. System Components Fresh water pump Thermostatic valve Expansion tank Heat exchanger Sea chest Strainer Sea water pump After cooler (Charge air cooler) 22 සීමාන්විතයි Intake Air and Exhaust System 31. The induction system must provide the engine with an adequate supply of clean air for good combustion for all operating speeds, loads, and operating conditions. To increase the amount of power that can be developed from an engine the amount of fuel burnt and air induction in its cylinders have to be increased. Air intake of an IC engine may be natural aspiration, supercharging or turbocharging. 32. On a naturally aspirated four-stroke-cycle engine, the system includes the air cleaner, the intake manifold, and the connecting tubing and pipes. On the two-stroke cycle, the system also includes a blower for scavenging air and for combustion. On a turbocharged engine, additional air is supplied by means of a turbocharger, which is exhaust gas–driven. On a supercharged engine a mechanically driven blower is used to supply additional air. The turbocharger compresses intake air to a density up to four times that of atmospheric pressure. This greater amount of dense air allows more fuel to be burned, thereby doubling the engine‟s power output. The turbocharger also reduces exhaust emissions and exhaust noise. 33. An air shutdown valve may be included to allow engine intake air to be shut off completely for emergency engine shutdown. 34. An intercooler or after-cooler may also be included in the induction system. Since cooler air is denser, a greater amount of air is in fact supplied if the air is cooled. The intercooler is mounted to cool the intake air after it leaves the discharge side of the turbocharger and before it enters the engine. 23 සීමාන්විතයි CHAPTER 04 SHIP’S SYSTEMS Introduction 1. A set or group of components interconnected to ensure efficient working of equipment is called a System. Purpose 2. The purposes of a Ship's system are, a. To increase the operational efficiency of machinery and ship. b. To save manpower and time. c. To save wastage of material. d. To save duplication of equipment. 3. Various systems fitted onboard ships are as follows. a. b. c. d. Domestic fresh water system Compressed air system Fuel filling and transfer system Sea water system (1) Fire main system (2) Cooling water system (3) Sanitary system (4) Pre-wetting system (5) Bilge system (6) Magazine spraying and flooding system (7) Ballasting / de-ballasting system Domestic Fresh Water System 4. This system is meant for receiving fresh water from another ship or ashore and storing it in storage tanks and also for distributing water from storage tanks to various consumers. It can also pump water to other ships or overboard from storage tanks. This system is provided with clarifiers for mixing chlorine with the fresh water. This system may be of any of the following types, a. b. c. Gravity fresh water system. Pressurized fresh water system. Direct pumping system. 24 සීමාන්විතයි Sea Water System 5. This system is meant for supplying seawater throughout the ship for various requirements. The salt water systems onboard are as follows. a. Fire main system. It is meant for supplying sea water to the fire hydrants for fighting the fire on board ship. It also supplies sea water to pre-wetting system, sanitary system, bilges pumping out system, magazine spraying system, ballasting and de-ballasting system and for anchor washing. Fire main system is fitted with two or more pumps to maintain the sea water pressure throughout the ship. 25 සීමාන්විතයි b. Cooling water system It is meant for supplying sea water to cool down the lubricating oil of main engines and auxiliary machinery. All the machinery require sea water for cooling has separate sea water pump to maintain the sea water pressure in the cooling system and additional line given to these system via fire main to use in case of an emergency. c. Sanitary system It is meant for supplying seawater to the crew's sanitary spaces and bathrooms for sanitation. d. Pre-wetting system This system sprinkles the sea water with the use of sprinklers on the weather-deck to provide a cover for the ship when the ship is passing through a nuclear fallout area. e. Bilges pumping out system It is meant for pumping out the bilges with the use of educators which were operated by the sea water under pressure. 26 සීමාන්විතයි f. Magazine spraying and flooding system This system is used to keep the temperature of magazines within limits to avoid any explosion, which can cause heavy damage to ship. This system is normally operated remotely. g. Ballasting system / De-ballasting This system is meant for filling sea water by flooding directly through sea cock or through main suction line into empty fuel tanks or ballasting tanks to maintain ship's stability and emptying the sea water from filled fuel tanks or de-ballasting tanks by pumping out through main suction line or by portable/submersible pumps to sea. 27 සීමාන්විතයි Compressed Air System 6. It supplies high pressure and low pressure air through the ship for the following purposes. a. b. c. d. e. f. g. h. j. k. l. Main engine and diesel generator starting system. Gas turbine starting system. Gas turbine liquid firefighting system. For compressed air foam system (CAFS) as a firefighting system. For supplying water to accommodation and various parts of the ship through hydrophore. For automation and control air for main and auxiliary engine. For different application on the deck side and in engine room such as chipping, drilling, buffing, pressurized water jet cleaning etc. by use of pneumatic tools and machinery. Torpedo firing system. Testing of water tight compartments. Compressed air is also used for ships whistle and fog horn. General cleaning purposes Fuel Filling and Transferring System 7. This system is meant for receiving fuel to fill storage tanks and to transfer fuel from storage tanks to daily use tanks or other places required within the ship or transferring to other ship/craft. The fuel filling and transferring system has the tanks, piping and pumps for loading, storing and transferring fuel internally. 28 සීමාන්විතයි 8. Fuel comes onboard at the deck fueling station and then flows by gravity through a fueling manifold in the machinery spaces to the storage tanks. Fuel is transferred with the fuel transfer pumps from the storage tanks to daily use tanks prior facilitate to the main machinery. These tanks are normally above the main machinery level and nearby the machinery spaces therefore, it provides fuel to the main machinery by gravity. In smaller craft these tanks are optional and each machinery provided with a suitable fuel pump to take the required suction from the tank. 9. The fuel oil filling and transfer system provides a means for routing the discharge of the fuel oil transfer pump to the deck connection so that the ship may be defueled with installed equipment. 10. The colour code used for systems on board ship stated below. a. b. c. d. e. f. g. h. j. Red – Fire main system, hanger spraying system & firefighting systems Orange – Oils other than fuel Black – Waste media Blue – Fresh water system Brown – Fuel system Green – Sea water Silver – Steam White – Compressed air system & air ventilation system Yellow – Flammable gases 29 සීමාන්විතයි k. Gray – Non-flammable gases CHAPTER 05 MACHINERY LAYOUT OF AN ENGINE ROOM 01. On a ship the engine room is the propulsion machinery spaces of the vessel. To increase the safety and damage survivability of a vessel, the machinery necessary for operations may be segregated into various spaces. The engine room is one of these spaces and is generally the largest physical compartment of the machinery space. The engine room houses the vessel's prime mover usually some variations of a heat engine - diesel engine, gas or steam turbine. On some ships, the machinery space may comprise more than one engine room such as forward and aft or port and starboard engine rooms or may be simply numbered. 02. On a large percentage of vessels, ships and boats, the engine room is located near the bottom and at the rear or aft end of the vessel and usually comprises few compartments. This design maximizes the cargo carrying capacity of the vessel and situates the prime mover close to the propeller minimizing equipment cost and problems posed from long shaft lines. 03. Large engines drive electrical generators that provide power for the ship's electrical systems. Large ships typically have two or more synchronized generators to ensure smooth operation. The combined output of a ship's generators is well above the actual power requirement to accommodate maintenance or the loss of one generator. 04. Besides propulsion and auxiliary engines, a typical engine room contains air compressors, RO plant, air conditioning plants, refrigeration plants, purifiers, fire pumps, feed pumps, fuel pumps and electrical instrumentation. 05. Engine rooms are hot, noisy, sometimes dirty, and potentially dangerous. The presence of flammable fuel, high voltage (HV) electrical equipment and internal combustion engines (ICE) means that a serious fire hazard exists in the engine room, which is monitored continuously by the ship's engineering staff and various monitoring systems. 06. If engines are equipped with internal combustion or turbine engines, engine rooms employ some means of providing air for the operation of the engines and associated ventilation. If individuals are normally present in these rooms, additional ventilation should be available to keep engine room temperatures to acceptable limits. The requirement for general ventilation and the requirement for sufficient combustion air are quite different. Engines pull sufficient air into the engine room for their own operation. However, additional airflow for ventilation usually requires intake and exhaust blowers. 30 සීමාන්විතයි 07. Machinery layout 01 – Machinery control room 03 – Port main engine 05 – Starboard generator 07 – Air compressor 09 – Hydrophore 11 – Air bottle 13 – RO plant 15 – Port AC plant 17 – No 2 fire pump 02 – Starboard main engine 04 – Gear box 06 – Port generator 08 – Forward power board 10 – Fresh water pump 12 – Fuel transfer pumps 14 – Stbd AC plant 16 – No 1 fire pump 31 සීමාන්විතයි CHAPTER 06 AUXILIARY MACHINERY ONBOARD SHIP Air Conditioning and Refrigeration Plants 1. Introduction The term refrigeration has been derived from the word "Freeze" which involves the conversion of a liquid into solid by extraction of heat. Freezing involves the extraction of sensible heat for lowering the temperature of the liquid followed by removal of latent heat of freezing for conversion of the liquid to solid at a constant temperature known as freezing point. A heat pump or a refrigerating machine can be utilized for the removal of heat from a given body or space. Refrigerators are commonly used for production of ice, cooling of storage chambers in which perishable food, fruits, drugs etc. may be stored for liquefying gases and vapour in chemical and pharmaceutical industry, for cooling water in water coolers and in air conditioning of buildings, milk vans etc. 2. Refrigeration Refrigeration can be defined as the process by which the temperature of a given space or substance is lowered below that of the surroundings and maintaining it. 3. Air conditioning Air conditioning can be defined as the process of simultaneous controlling of temperature, humidity, cleanliness and flow of air or air motion. 4. Basic Laws of A/C & Refrigeration Refrigeration are:(a) (b) (c) The basic laws of Air Conditioning and All liquids while evaporating take heat from their surroundings. Any vapour can be condensed back to liquid if it is suitably compressed and cooled. The temperature at which any liquid will evaporate or boil away directly depends upon the pressure to which it is subjected. 5. There are several types of Air Conditioning and Refrigeration systems are available and the most common system using in SLN is vapour compression refrigeration system. 6. Main Components of a Vapour Compression A/C Plant refrigeration A/C plant consists of four main components. (a) (b) (c) (d) Compressor Condenser Expansion Valve/Regulating Valve Evaporator 32 සීමාන්විතයි A vapour compression 7. Compressor The refrigerant is removed as a gas from the evaporator during the suction stroke of the compressor. The compression stroke compresses the gas and the temperature and pressure of gas is increased. The superheated gas is delivered to the condenser in the cycle. 8. Condenser The purpose of condenser is to extract the heat from superheated refrigerant and liquefy it. The high pressure refrigerant vapour enters the condenser and heat flows from refrigerant to cooling medium thus allowing refrigerant to change the state from gas to liquid. 33 සීමාන්විතයි 9. Expansion Valve / Regulating Valve The refrigerant after changing its state is made to pass through the expansion valve. Here the pressure falls, which causes the state of refrigerant liquid to change to gaseous form. This change of state causes the cooling to the temperature required in the evaporator. 10. Evaporator The refrigerant must be completely changed to gas in the evaporator to avoid liquid being returned to the compressor. In the evaporator the brine, solution/cooling water rejects the heat to the refrigerant and the refrigerant completely changes to gaseous form. Thus the refrigerating effect is achieved. Basic Refrigeration Cycle 11. The refrigeration cycle begins with the refrigerant in the evaporator. At this stage the refrigerant in the evaporator is in liquid form and is used to absorb heat from the product or from an area. When leaving the evaporator, the refrigerant has absorbed a quantity of heat from the product or the area and is a low-pressure, low-temperature vapour. This lowpressure, low-temperature vapour is then drawn from the evaporator by the compressor. When vapour is compressed it rises in temperature. Therefore, the compressor transforms the low-temperature vapour to a high-temperature vapour, in turn increasing the pressure. 12. This high-temperature, high-pressure vapour is pumped from the compressor to the condenser and it is cooled by the surrounding air, sea water in marine system or in some cases by fan assistance. The vapour within the condenser is cooled only to the point where it becomes a liquid once more. The heat, which has been absorbed, is then conducted to the outside air or sea water. At this stage the liquid refrigerant is passed through the expansion valve. The expansion valve reduces the pressure of the liquid refrigerant and therefore reduces the temperature. The cycle is complete when the refrigerant flows into the evaporator from the expansion valve as a low-pressure and low-temperature liquid. 13. An air conditioning system can be further classified as direct and indirect air conditioning system plant (a) Direct expansion system The refrigerant is circulated through the evaporator coils directly for cooling the space or taking the heat from the products. There is no secondary refrigerant such as brine or fresh water used in this system. Therefore, the refrigerant has to circulate in separate evaporators placed for cabins or the plant is placed at only one location and cooled air will be taken by a blower through the ducts to the cabins. 34 සීමාන්විතයි (b) Indirect expansion system In this type a secondary refrigerant is cooled by the primary refrigerant in a chiller and then this secondary refrigerant is circulated through the coils of the air treatment unit in which heat transfer takes place. This makes the system bulky as more amount of brine is required to be circulated for the same refrigerating effect compared to a direct refrigerating system. A separate chill water pump available to circulate chill water through the system. 14. Applications of A/C & refrigeration plants The air refrigeration applications may be grouped in six general categories. a. b. c. d. e. f. 15. d. e. and Domestic Refrigeration. Commercial Refrigeration. Industrial Refrigeration. Marine and Transportation Refrigeration. Comfort Air Conditioning. Industrial Air Conditioning. Use of A/C plants on board ships a. b. c. conditioning The common uses of A/C plants are as follows. Air Conditioning of mess decks. Sick bay air conditioning. Air conditioning of Machinery Control Room and operations rooms etc. for better operation of equipment. Air conditioning of missile hangers. Air conditioning of magazine compartment. 16. Uses of refrigeration plant onboard ship The common uses of refrigeration plants onboard ship are as follows. a. b. c. d. e. Preservation of meat, fish etc. (Cold room -7 to -11 0C). Preservation of Vegetables, fruits, milk products etc. (Cool room 15 to 19 0C) Preservation and storage of medicines. Cooling of drinking water Preparation of ice for domestic and medical purposes 35 සීමාන්විතයි RO Plant 17. Principle of Osmosis Osmosis is the natural phenomena, which takes place when solutions of different concentrations are separated by a semi-permeable membrane. The solvent flows from the weak solution to the strong solution through the semi-permeable membrane. Thus osmosis tends to reduce the difference or to equalize concentration of liquids on both sides. Many phenomenon observed in nature are due to Osmosis. These include plants taking water from the soil through their roots, the lining of our stomachs accepting the food and water that we drink. 18. Principle of Reverse Osmosis This osmosis process can be reversed, by applying pressure (above osmotic pressure) on the strong solution side and is called Reverse Osmosis process. That is the solvent (pure water) is extracted from seawater. All Reverse Osmosis plants operate on this principle. 19. In Reverse Osmosis, the pressurized sea water is forced through a semi-permeable membrane to the fresh water recovery side. The membrane rejects the salt ions present in the sea water, yet allows the pure water to pass through the thin membrane material. Only about 30% of the sea water actually passes through the membrane as permeate. The remaining 70% sea water flushes the salt ions and other impurities off the membrane surface, and is discharged back into the sea as brine. Pressure of up to max of 65 bar is applied to the sea water to force the pure water molecules through the semi-permeable membrane. The majority of the dissolved salts and all of the organic material, bacteria and suspended solids are retained by the membrane and are discharged from the system with the brine. 36 සීමාන්විතයි 20. Main Components of RO Plant (a) (b) (c) (d) (e) (f) (g) (h) Pre-filter Pump Filter Pump Sand Filter Cartridge Filter De-acidification Filter High Pressure Plunger Pump Servomotor Control DT Module Function of main components 21. Pre-Filter Pump Pre-filter pump is used to supply Sea Water to the RO plant filter pump with sufficient pre-pressure and quantity, and consist of centrifugal pump. 22. Filter Pump Filter pump is designed to supply this raw water received from the Pre-Filter pump to the filter system and thereafter to the high-pressure pump with designed pressure and quantity. The Filter Pump is also a centrifugal pump. 23. Sand Filter The sand filter contains 3 layers of fine, medium and coarse sand. This unit is designed for rapid filtration of the raw water with back washing facility. The filter system is supplied with gauges and diverting valves. The normal flow of water is from top to bottom. Only the top layer carries out the function of filtering while others are supporting layers. 37 සීමාන්විතයි 24. Cartridge Filter Cartridge filter is designed to remove any suspended matter to reduce organic or inorganic fouling of the membrane up to 10 microns. Cartridge filter is supplied with sufficient pre-pressure from the filter pump. 25. High Pressure Pump The high pressure plunger pump system consists of a slow revolution triplex plunger pump supplied with motor, pulsation damper and pressure relief valve. The high pressure pump is fitted in a separate frame for alternative installation in case of space shortage and for easy installation. 26. Pulsation Damper The pulsation damper is fitted on the discharge side of the HP pump. The pump being triplex plunger type reciprocating pump the discharge pressure of each cylinder varies over the entire length of its stroke. The pulsation damper evens out the pressure variations so that the pressure at the DT module is even and steady. 27. De-Acidification Filter The normal sea water contains carbonates in small percentage. During reverse osmosis process these carbonates break up and generate CO 2, which passes over to the permeate side. This carbon dioxide will combine with water and form carbonic acid. Hence, to prevent the corrosion of product water flowing coated iron pipes a de-acidification filter is installed. This filter converts free CO 2 back in to Ca++ and HCO3-1 by the following chemical reaction. CaCO3 +CO2 + H2O = Ca (HCO3) 2 28. DT Module The DT module consists basically of a disc membrane stack and pressure vessel. The disc membrane stack is fitted inside the pressure vessel. End flanges with groove rings close both openings of the pressure vessel. The membrane spacer and the pure water manifold are designed as an integral part of the hydraulic disc. The integrated spacer forms the open raw water channel. The extremely short feed water path across the membrane followed by a 180-degree flow reversal eliminates polarization concentration. The result is minimum membrane fouling and scaling and a minimum flow path with low resistance. 29. The membrane cushions are stacked on the center tension rod. Each membrane cushion is covered at top and bottom by a hydraulic disc to form a separate chamber for each cushion. Raw water, which flows under high pressure into the membrane module at raw water inlet on the DT module, enters the membrane stack at the first membrane. On its way to the next chamber it flows across bottom and top membrane cushion surface. This permeates drains into the pure water manifold around the tension rod. From there it is discharged out through permeate line. The brackish water is sealed off with an „O‟ Ring from the pure water manifold. 38 සීමාන්විතයි Operation of RO plant 30. The sea water is pumped into the system by the pre filter booster pump at the inlet of the filter pump. The filter pump further ensures that sufficient pressure is maintained in the system for normal operation. The sea water then filtered by the sand filter and the cartridge filter which removes the foreign materials down to 10 microns. The filtered water is then pressurized to 60 bar (normal operating pressure) by the high pressure pump. The water passes over the membrane cushions in the DT Modules. 31. The high pressure is regulated by the servo motor control valve. About thirty percent water passes across to the pure water side. The remainder water is called as brine is discharged back to the sea. The entire operation of the RO plant is automatically controlled by a stored programme in the microprocessor fitted in the control panel. The control panel houses all the electronics and the electrical circuits. The pure water is called as permeate water which is the output of the RO Plant is sent to the storage water tank of the ship. Purifier 32. When a centrifuge is set up as a purifier, a second outlet pipe is used for discharging water as shown. In the fuel oil purifier, the untreated fuel contains a mixture of oil, solids and water, which the centrifuge separates into three layers. While in operation, a quantity of oil remains in the bowl to form a complete seal around the underside of the top disc and, because of the density difference, confines the oil within the outside diameter of the top disc. 39 සීමාන්විතයි 33. As marine fuel oil normally contains a small quantity of water, it is necessary to prime the bowl each time that it is run; otherwise all the oil will pass over the water outlet side to waste. The water outlet is at greater radius than that of the fuel. Within the water outlet there is a gravity disc, which controls the radial position of the fuel water interface. 34. A set of gravity discs is supplied with each machine and the optimum size to be fitted depends on the density of the untreated oil. When the fuel centrifuge is operating, particulate matter will accumulate on the walls of the bowl. If the centrifuge is set as a clarifier, the particulate matter will be a combination of water and solid material. If it is set as a purifier, the free water is continuously discharged; therefore, the particulate matter will consist of solid material. In older machines it is necessary to stop the centrifuge to manually clean the bowl and disc stack, however, the majority of machines today can discharge the bowl contents while the centrifuge is running. Pumps 35. Introduction Pumps form an important part of any engineering system. Pumps serve as a means of transporting fluids. They convert mechanical energy into potential, kinetic and thermal energy of the fluid. This mechanical energy may be obtained from an electrical motor. 36. Water, by far, is the most common fluid handled by pump and serves as a "standard" fluid for determining pump performance. 37. Pump liquid. Pump is a mechanical device used to increase the pressure energy of 38. Uses of Pumps Pumps are widely used on board ships for the following purposes: a. Domestic fresh water supply to Bathrooms, Wash basins, Galley etc. b. Fire main/sanitary supply of sea water. c. Machinery cooling by sea water/fresh water. d. Embarking/Disembarking of POL. e. Transfer of POL within the ship. f. Pumping out bilges and flooded compartments. g. Supply of fluid for operation of steering gear, stabilizers and hydraulic machinery. h. Circulation of brine in Air Conditioning plants. 40 සීමාන්විතයි 39. Types of Pumps All pumps can be grouped under the following heads. a. Positive Displacement Pump Positive-displacement pumps are another category of pumps. Types of positive-displacement pumps are reciprocating, semirotary and rotary pumps. Positive-displacement pumps operate by forcing a fixed volume of fluid from the inlet pressure section of the pump into the discharge zone of the pump. These pumps generally tend to be larger than equal-capacity dynamic pumps. Positive-displacement pumps frequently are used in hydraulic systems at pressures ranging up to 5000 psi. A principal advantage of hydraulic power is the high power density (power per unit weight) that can be achieved. They also provide a fixed displacement per revolution and, within mechanical limitations, infinite pressure to move fluids. These pumps do not require to be primed and therefore can be conveniently used as priming pumps. b. Dynamic Pressure Pump In this type of pump energy is continuously added to the fluid within the pump. Dynamic pumps are one category of pumps under which there are several classes, two of which are: centrifugal and axial. These pumps operate by developing a high liquid velocity and converting the velocity to pressure in a diffusing flow passage. Dynamic pumps usually have lower efficiencies than positive displacement pumps, but also have lower maintenance requirements. Dynamic pumps are also able to operate at fairly high speeds and high fluid flow rates. Reciprocating pump 40. In a reciprocating pump, a volume of liquid is drawn into the cylinder through the suction valve on the intake stroke and is discharged under positive pressure through the outlet valves on the discharge stroke. The discharge from a reciprocating pump is pulsating and changes only when the speed of the pump is changed. This is because the intake is always a constant volume. Often an air chamber is connected on the discharge side of the pump to provide a more even flow by evening out the pressure surges. Reciprocating pumps are often used for sludge and slurry. 41 සීමාන්විතයි 41. One construction style of a reciprocating pump is the direct-acting steam pump. These consist of a steam cylinder end in line with a liquid cylinder end, with a straight rod connection between the steam piston and the pump piston or plunger. These pistons are double acting which means that each side pumps on every stroke. 42. Another construction style is the power pump which converts rotary motion to low speed reciprocating motion using a speed reducing gear. The power pump can be either single or double-acting. A single-acting design discharges liquid only on one side of the piston or plunger. Only one suction and one discharge stroke per revolution of the crankshaft can occur. The double-acting design takes suction and discharges on both sides of the piston resulting in two suctions and discharges per crankshaft revolution. Power pumps are generally very efficient and can develop high pressures. These pumps do however tend to be expensive. Rotary pump 43. A rotary pump traps fluid in its closed casing and discharges a smooth flow. They can handle almost any liquid that does not contain hard and abrasive solids, including viscous liquids. They are also simple in design and efficient in handling flow conditions that are usually considered to low for economic application of centrifuges. Types of rotary pumps include cam-and-piston, internal-gear, lobular, screw, and vane pumps. 42 සීමාන්විතයි 44. Gear pumps are found in home heating systems in which the burners are fired by oil. Rotary pumps find wide use for viscous liquids. When pumping highly viscous fluids, rotary pumps must be operated at reduced speeds because at higher speeds the liquid cannot flow into the casing fast enough to fill it. Unlike a centrifugal pump, the rotary design will deliver a capacity that is not greatly affected by pressure variations on either the suction or discharge ends. In services where large changes in pressure are anticipated, the rotary design should be considered. Centrifugal pump 45. A centrifugal pump consists of an impeller and an intake at its center. These are arranged so that when the impeller rotates, liquid is discharged by centrifugal force into a casing surrounding the impeller. The casing is there in order to gradually decrease the velocity of the fluid which leaves the impeller at a high velocity. This velocity is converted to pressure which is needed to discharge the fluid. 46. Some of the advantages of centrifugal pumps are smooth flow through the pump and uniform pressure in the discharge pipe, low cost, light weight, less maintenance and an operating speed that allows for direct connection to steam turbines and electric motors. The centrifugal pump accounts for not less than 80% of the world‟s pump production because it is more suitable for handling large capacities of liquids than the positive-displacement pump. Axial flow pump 45. Axial flow pumps are also called propeller pump. These pumps develop most of their pressure by the propelling or lifting action of the vanes on the liquid. These pumps are classed with centrifugal pumps, although centrifugal force plays no part in the pumping action. When sea water has to pass through large condensers, axial flow pumps are used. It ensures sufficient speed and adequate flow of water. The screw propeller creates an increase in pressure by causing an axial acceleration of liquid within its blades. This is converted to straight axial movement by suitably shaped outlet guide vanes. 43 සීමාන්විතයි 47. These pumps are used for drainage, sewage, storm water disposal, irrigation and condenser water circulation. These pumps are marked under the names as propeller, axial flow and straight flow. In general, vertical single-stage axial and mixed-flow pumps are used however; sometimes two-stage axial-flow pumps are economically more practical. Horizontal axial-flow pumps are used for pumping large volumes against low pressures. 47. Comparison of Centrifugal and Reciprocating pumps Centrifugal pump Reciprocating pump Simple in construction, because of less number of parts. Total weight of the pump is less for a given discharge. Suitable for large discharge and smaller heads. Requires less floor area and simple foundation. Less wear and tear. Maintenance cost is less. Can handle dirty water. Can run at higher speeds. Its delivery is continuous. No air vessels are required. Thrust on the crankshaft is uniform. Operation is quite simple. Needs priming. It has less efficiency. Complicated in construction, because of more number of parts. Total weight of the pump is more for a given discharge. Suitable for less discharge and higher heads. Requires more floor area and comparatively heavy foundation. More wear and tear. Maintenance cost is high. Cannot handle dirty water. Cannot run at higher speeds. Its delivery is pulsating. Air vessels are required Thrust on the crankshaft is not uniform. Much care is required in operation. Does not need priming. It has more efficiency. 44 සීමාන්විතයි CHAPTER 07 TRANSMISSION OF ENGINE POWER AND SHAFTING Purpose of Engine Power Transmission 1. Marine propulsion is the mechanism or system used to generate thrust to move a ship or craft across water. Marine engineering is the discipline concerned with the design of marine propulsion systems. Most modern ships use a reciprocating diesel engine as their prime mover, due to their operating simplicity, robustness and fuel economy compared to most other prime mover mechanisms. The rotating crankshaft can be directly coupled to the propeller with slow speed engines and via a reduction gearbox for medium and high speed engines. 2. Power transmission is occurring according to two methods. a. Direct drive A direct drive mechanism is one that takes the power coming from a motor/engine without any reductions or without changing the rotational direction. Generators, slow speed and smaller engines and pumps are examples for this type. b. Indirect drive The drive mechanisms of most engine powered in ships and of many boats are the indirect type. With this drive the power developed by the engine is transmitted to the propeller indirectly, through an intermediate mechanism that reduces the shaft speed. Speed may be reduced mechanically by a combination of gears or by electrical means (for example a diesel electric drive). Reduction Gear 3. The mechanical drives include the devices that reduce the shaft speed of driven unit, provide a means for reversing the direction of shaft rotation in the driven unit and permit quick disconnection of the driving unit from the driven unit. 4. Propellers operate most efficiently in a relatively low rpm range. The most efficient designs of diesel engines however, operate in a relatively high rpm range. In order that both the engine and the propeller may operate efficiently, the drive mechanism in many installations includes a device that permits a speed reduction from engine crankshaft to propeller shaft. The combination of gears that brings about the speed reduction is called a reduction gear. In most diesel engine installations, the reduction ratio does not exceed 3 to 1. There are some units, however, that have reductions as high as 6 to 1. The propelling equipment of a ship / craft must provide astern power as well as forward power. 45 සීමාන්විතයි Gearbox 5. In mechanical drives, the direction of rotation of the propeller shaft is reversed by use of reverse gears. The drive mechanism of a ship or boat must do more than reduce speed and change direction of rotation. Most drive mechanisms have a clutch. The clutch disconnects the drive mechanism from the propeller shaft and permits the engine to be operated without turning the propeller shaft. 6. Most of ships and craft are normally equipped with a „Thrust Reversing Gearbox‟ which has three gear positions of „Ahead‟, „Neutral‟, and „Astern‟ to navigate and manoeuvre safely at sea. Main components of a gear box are, a. b. c. d. e. Reduction gear wheel Gear wheels (forward and reverse pinions) Reverse driven gear wheel Clutch (forward and reverse) Rubber block drive (Coupling) 7. Reversible Engines These engines are not designed with reversible gear mechanism. For astern movement, engine should shut down and changes the direction of firing immediately. Purpose of shafting system 8. It is used to transmit the torque developed by the engine to the propeller and to transmit the thrust developed by the propeller to the ship's hull. Further it provides support to the propeller and shafts and safely withstands transient operating loads. 46 සීමාන්විතයි Arrangement of Shafting 9. The shaft line is divided into three main sections coupled together rigidly. Those are, a. Thrust shaft The thrust of the propeller is transmitted to the ship hull through the thrust block, which is usually fitted in this length of shafting. b. Intermediate shaft The length of shafting connecting the thrust shaft and tail shaft is known as intermediate shaft. c. Tail shaft The final length of shafting, to which the propeller is attached, is known as tail shaft. Main components of Shafting System 10. The main components of shafting system are as follows. a. b. c. d. e. f. g. h. j. k. Thrust block Plummer block Bulkhead gland Shaft locking gear Loose coupling Stern gland Stern tube bushes A' bracket Eddy plate Rope guard 47 සීමාන්විතයි Thrust Block 11. Its function is to transmit the thrust to the ship's hull. The thrust pads transmit the thrust to the thrust block body which is rigidly secured to the ship structure. Plummer Block 12. Its function is to support the length of intermediate shafting. A Plummer Block is assembled with self-aligning ball bearings or spherical roller bearings to support the load and weight of the whole equipment and to maintain the rotational movement stably so it is a very important that requires high degree of precision even at difficult running conditions. Bearings may be grease lubricated or oil lubricated in large Plummer blocks. 48 සීමාන්විතයි Bulkhead Gland 13. These are fitted where the shaft passes through the watertight bulkheads to maintain watertight integrity between two adjacent watertight compartments. Further, it has the capability to withstand shaft movement in vertical, angular and horizontal direction. These are grease lubricated. There are two main types of bulkhead glands available and those are, a. b. Flexible spherical bulkhead gland Self-aligning bulkhead gland Shaft Locking Gear 14. Shaft locking gears are used to lock the individual shaft to prevent it from rotating under the following conditions. a. b. c. d. e. 15. To lock the shaft at 12 „O‟ clock position before entering into dry dock. To prevent damaged engine or shaft from rotating. To prevent a damaged component of shafting from further damage. When a ship to be towed with damaged shafting. To load an engine when required to sail at slow speed with one shaft engaged. There are two types of shaft locking gears use inboard ships and those are, a. b. Positive locking gear type Band brake type 49 සීමාන්විතයි Loose Coupling 16. It is the coupling connecting the intermediate shaft with the tail shaft and the thrust shaft. This facilitates easy disconnection of the shafting link specially the tail shaft. This consists of an iron flange or collar which is forced on to a tapered cone at the inboard end of the tail shaft and secured by keys and rings. Stern Gland 17. It is fitted in way of shaft passing through the ship structure to sea and avoids water ingress from sea into the ship. The commonly used sealing arrangement in the stern glands includes: a. Conventional stuffing box with turns of soft packing. b. Facial contact sealing gland. c. Inboard water lubricated inflatable ET type split deep sea seals. d. Out board/inboard oil lubricated stern tube seal. 50 සීමාන්විතයි Stern Tube Bushes 18. The Stern tube consists of a shipbuilder‟s tube which is integral with the hull. Stern tube bushes are fitted inside the stern tube to support the tail shaft in way of shaft passing through ships structure in to the sea and the stern gland is mounted on the forward inboard end. 19. The bushes are fitted at each end of the stern tube and consist of gunmetal or steel bushes made in halves and lined with lignum vitae, hard rubber strips, thordon /feroform bushes or white metal. Most of ships these bushes are water lubricated and few are oil lubricated. At the inboard end gland can be of soft packing type or facial contact type. ‘A’ Bracket 20. It is fitted on the outboard side of the ship and adjacent to the propeller to support the tail shaft and to take the weight of the propeller. The bearings inside the „A‟ bracket may be hard rubber, thordon or feroform and the bearings are fitted on a gunmetal bush. Generally, these bearings are water lubricated. 51 සීමාන්විතයි Eddy Plate 20. Eddy plates fitted on aft side of stern tube and forward side of „A‟ bracket. These are fitted to maintain the stream line profile of the ship and minimize the corrosion and cavitation effect due to eddies. Therefore these are specially shaped fittings to streamline flow of water. Rope Guard 21. A cylindrical steel plate in halves, called rope guard is fitted between the propeller and the aft end of the „A‟ bracket to prevent ropes, wires, chains from becoming wound around the shaft. 52 සීමාන්විතයි CHAPTER 08 STEERING SYSTEM Principle of Steering Gear 1. A ship is steered by a rudder which is power operated by the movement of steering wheel. The rudder is moved by hydraulic rams mounted on the inboard rudder head and hydraulic power is supplied from pumps. The delivery of oil from the pumps to the rams is achieved by the inclusion of Telemotor system/electric motor etc. 2. Steering system is divided into three parts. a. Control Equipment Control equipment conveys the signal for desired rudder angle and activates the power unit and transmission system. b. Power Unit desired angle. c. Transmission System This system is the means by which the movement of the rudder is accomplished. Power unit provides the force to move the rudder to the Types of Steering Gear 3. The steering gears can be classified into different types depending on the control equipment used. a. Manual Rudder turned manually (as operated in a whaler). b. Mechanical steering gear All transmissions from the steering wheel to the rudder are by mechanical means through hand operated tiller or rudder operated by a rope, chain and pulley or rack and pinion. c. Telemotor steering gear This employs „master and slave‟ principle. The control and power systems are hydraulic. d. Electro-hydraulic steering gear the power system is hydraulic. e. All electrical In this control system is electrical and Both control and power systems are electrical. 53 සීමාන්විතයි 4. Characteristic features of Steering gear are, a. b. c. d. e. f. g. h. 5. Dependable and safe operation under any navigating condition. Long service life. Ability to put the rudder over to the required angle at full ship speed. Ability to put the rudder over to the required speed of rudder motion. Possibility of rapid changeover from main type of steering to the auxiliary system. Possibility of control from several places. Minimum overall size and weight. A simple design with easy maintenance and servicing. Various Positions of Steering a. b. c. Primary Steering position (Bridge) Secondary Steering position (Wheel house) Aft steering position (1) Local control (2) Emergency Rudder 6. The rudder is the fin or spade like projection under the counter and below the water line, generally placed as far as practicable. It is hung on a circular, solid shaft called a stock that penetrates the hull through a stuffing box and bearings. It often has a fixed, faired, foil like sections ahead of it, which is firmly attached to and part of the ship‟s structure. It moved by hydraulic rams mounted on the rudder head and hydraulic power is supplied from constant running rotary pump. Types of Rudders 7. The general types of rudders are as follows. a. Unbalanced Blade entirely aft of the stock. b. Balanced Portion of the rudder area disposed systematically throughout the rudder height, is forward of the stock. c. Semi Balanced Rudder Area forward of the stock does not extend the full height of the blade aft of the stock. 54 සීමාන්විතයි Telemotor Steering Gear 8. The Telemotor steering gear consists of the following major units. a. Steering Wheel - Steering control lever. b. Telemotor Transmitter - Operates the rack by the steering wheel at bridge and moves the transmitter plunger. It displaced fluids to receiver. 55 සීමාන්විතයි c. Telemotor Receiver - In which identical movement is conveyed from the transmitter and then applied to the stroke of the pump. Fitted in steering compartment. d. Steering Pump - Variable displacement delivery pumps which can deliver a reversible flow of liquid to the steering rams. e. Steering Rams - Moved by the delivery of the fluid from the pumps and convey the movement to the rudder head. f. Floating Lever plunger. g. Hunting Rod - To center-up the pump or to bring the pump in non-pumping position as and when rudder has reached the desired angle. h. Rudder - Steering controller. It gets activated by the movement of the transmitter Function of Telemotor System 9. Telemotor transmitter connected to steering wheel by a rack. When the steering wheel moves Port and Stbd Telemotor piston moves up and down accordingly. Telemotor transmitter has connected to Telemotor receiver by two hydraulic lines. The displacement of fluid due to the piston movement thereby causes a corresponding movement of the receiver plunger. The system is maintained fully charged with fluid, with air release, center balancing ports and equalizer springs on the receiver to maintain correct relationship of movement. 10. Telemotor receiver has connected to hydraulic pump with the help of floating leaver. Floating lever activate the hydraulic pump and provides required amount of hydraulic oil to hydraulic ramps. Because of the oil pressure generated by the ramps, the rudder will turn to the required directions. Hunting rod de activates the hydraulic pressure pump after achieving the required rudder angle. The Hunting Gear `centers up‟ the pump when the rudder has moved over the degrees of helm applied by the steering wheel or if the system without hunting gear it would be necessary to take the stroke off the pump (center-up) by moving the wheel back to the central position. Electro-Hydraulic Steering System 11. In this system the helm (steering wheel) in the bridge or wheel house transmits orders electrically and executes the orders hydraulically on the rudder through steering gears located directly above the rudder. Although several different designs of steering gears are in common use, their operating principles are similar and in this system only transmitter and receiver are electrical when comparing with the Telemotor system. 56 සීමාන්විතයි 12. Modes of Steering a. Non-follow up In this mode rudder will continue to turn when the steering wheel or other controller is moved from its control position. Rudder movement is stopped only when the steering control is centered once again. b. Follow-up With this system movement of the rudder follows the movement of the steering controller. If the controller is moved to indicate a desired rudder position, the rudder will turn until the actual rudder angle is the same as the desired rudder angle shown on the steering pedestal. c. Automatic With these systems the steering control circuits are controlled by signals received from the master compass; so that the ship is automatically held on to a selected course. 57 සීමාන්විතයි Emergency Steering System 13. An emergency steering system, as the name suggests, is a system which is used during the failure of the main steering system of the ship. A situation can occur in which the remote control operation may fail to work and there can be a sudden loss of steering control from the bridge. This can be due to sudden power failure, any electrical fault in the system or the control system which includes faulty Telemotor or servo motor which is used for transferring the signal from bridge to the steering unit. 14. To have control the steering of the ship at such emergency situation with manual measure from within the steering gear room, an emergency steering system is used. Procedure for Emergency Steering Operation 15. The following points should be followed for emergency steering operation. a. The procedure and diagram for operating emergency steering should be displayed in steering gear room and bridge. b. Even in emergency situation we cannot turn the massive rudder by hand or any other means, and that‟s why a hydraulic motor is given a supply from the emergency generator directly through emergency switch board. It should also be displayed in the steering room. c. Ensure a clear communication for emergency operation via VHF or ships telephone system. d. Normally a switch is given in the power supply panel of steering gear for Telemotor; switch off the supply from the panel and change the mode of operation by selecting the switch for the motor which is supplied emergency power. e. There is a safety pin at the manual operation helms wheel so that during normal operation the manual operation always remains in cut-off mode. Remove that pin. f. A helms wheel is provided which controls the flow of oil to the rams with a rudder angle indicator. Wheel can be turned clockwise or anti clockwise for going port or starboard or vice versa. g. If there is a power failure, through sound power telephone receive orders from the bridge for the rudder angle. As soon as you get the orders, turn the wheel and check the rudder angle indicator. 58 සීමාන්විතයි 16. A routine check should always be done for proper working of manual emergency system and steering gear system. An emergency steering drill should be carried out every month (prescribed duration - 3 months) in the steering gear room with proper communication with bridge to train all the ship‟s staff for proper operation of the system so that in emergency situation ships control can be regained as soon as possible, avoiding collision or grounding. 59 සීමාන්විතයි CHAPTER 09 DOCKING AND SLIPPING 1. Purpose of docking a ship/craft is as follows. a. To undertake routine maintenance of underwater hull & components of propulsion system. b. Repairs to underwater fittings. 2. Types of docks a. b. Graving docks Floating docks 3. Graving Dock The classic form of dry-dock, properly known as graving dock, is a narrow basin usually made of earthen berms and concrete closed by gates or by a caisson, into which a vessel may be floated and the water pumped out leaving the vessel supported on blocks. The keel blocks as well as the bilge block are placed on the floor of the dock in accordance with the "docking plan" of the ship. More routine use of dry-docks is for the cleaning (removal of barnacles and rust) and re-painting of ship's hulls. Modern graving docks are box-shaped to accommodate the newer boxier ship designs whereas old dry-docks are often shaped like the ships that are planned to be docked there. This shaping was advantageous because such a dock was easier to build, it was easier to side-support the ships and less water had to be pumped away. 4. Floating Dock A floating dry-dock is a type of pontoon for dry docking ships, possessing floodable buoyancy chambers and a "U"-shaped cross-section. The walls are used to give the dry-dock stability when the floor or deck is below the surface of the water. When valves are opened, the chambers fill with water causing the dry-dock to float lower in the water. The deck becomes submerged and this allows a ship to be moved into position inside. When the water is pumped out of the chambers, the dry-dock rises and the ship is lifted out of the water on the rising deck allowing work to proceed on the ship's hull. Alternative Dry-dock Systems 5. Apart from graving docks and floating dry-docks, ships can also be dry docked and launched by: a. Marine railway - For repair of larger ships up to about 3000 tons weight b. Shiplift - For repair as well as for new building. From 800 to 25000 tons weight c. Slipway, Patent slip - For repair of smaller boats and the new building launch of larger vessels 60 සීමාන්විතයි 6. Preparations for docking a. b. c. d. e. f. g. h j. k. l. 7. Safety precautions whilst on dock a. b. c. d. e. f. g. h. j. k. l. m. n. 8. Remove all ammunitions, guns & explosives. De-bunkering the ship. Ensure that all spare parts & paints are available as per the defect list. All stores those are not mandatory to be kept onboard to empty. All water tanks must be empty. Adjust the trim with consultation of dock master. Zero list and trim according to ship builders‟ standard. Ensure that all moving parts & cranes, derricks are properly secured. Educate men about safety precaution to be adhered whilst on dock. Ensure availability of sufficient men onboard. Ensure all defects are included in the defect list & prepare a supplementary defect list if required. Ensure that the ship is properly earthed. Place safety instructions boards at all necessary places. Ensure that fire sentries are properly placed prior to allowing any welding/cutting operations. Do not shift or add/remove weight without taking prior precautions. Ensure that all men wearing proper safety gears. No loose electrical wiring to be allowed. Fire party must be ready in all aspects. Temporary ladders & gangways must be properly secured. Ensure that no spillage of oil /oily substances on docks. Cover all equipment whilst carrying out blasting. No consumption of liquor onboard. All the work are properly monitored & attended. Proper precautions are taken prior to entering confined spaces. Routines / Repairs to be attended during the docking/slipping a. b. c. Scrape and clean under water portion of hull. Surveying of hull. Examine under water structure which includes - Hull plate thicknesses, propellers, shaft brackets, rudders, keel, ship builder‟s tube, eddy plates, zinc protectors and consumable anodes, gratings of inlets and discharges, ICCP anodes and electrodes for damages. 61 සීමාන්විතයි d. e. f. g. h. j. k. 9 Check draught marks are in position and paint them. Paint underwater structure of hull. Check the bearing clearances of “A” brackets and replace bearings which having excessive clearances (max 4mm). Polish the shaft and give protective coating to outboard length. Check the rudder bearing clearances. Alignment of shafting system. Overhauling of all the underwater valves. Prior-Undocking a. b. c. d. e. f. g. All the underwater valves should be service & proved. All underwater hull repairs to be completed. All Zinc protectors are properly secured. Do necessary calculations & considering the record of weight shifting & ensure that trim is same as that existed while docking. Ensure that all places, where hull repairs were attended, are properly checked & proven. Have all underwater compartment manned by competent personnel while undocking. Stop flooding halfway through and check the performances of the underwater valves. 62 සීමාන්විතයි CHAPTER 10 OUT BOARD MOTORS Introduction 1. Out board motor is designed to propel a boat/raft of reasonable size. It can be easily installed and detached from the boat/raft. OBM is a power plant complete with engine, fuel supply and starting system. It has a power head and drive shaft extending downwards into the water to drive the propeller. 2. Main parts of OBM a. Power Head This part is generating power for the operation of OBM. This section contains horizontally mounted cylinders, piston, cylinder head, crank shaft, fly wheel, carburetor, electrical system, fuel pump and starting mechanism. b. Mid-Section This section contains the drive shaft, bracket, exhaust manifold, water pump discharge line etc. c. Lower Unit The lower unit has transmission gears, a dog clutch, water pump, water pump inlet strainer, anti-cavitation plate, propeller and water & exhaust outlet. POWER HEAD MID-SECTION LOWER UNIT 63 සීමාන්විතයි Basic working principle 3. The majority of existing outboard motors use two stroke technology. However the current movement in emissions regulations is pushing the design of current outboards towards the 4 stroke and direct injection two stroke design. Efforts to build a 4 stroke outboard in the past have been many and varied, mostly unsuccessful as the design technology and precision production that can be achieved today were impossible to achieve then. Resulting motors were bulky and unreliable. Those motors that were viable were for the most part rejected by the boating public. 4. The two-stroke engine completes its power cycle in only one crankshaft revolution with two strokes of the piston. There are no valves, camshafts, springs chains, etc. So the engine is much less complex and lighter. Instead of valves there are a series of strategically located transfer ports - intake and exhaust, cut into the sides of the cylinder wall. The ports are on opposite sides of the cylinder. The transfer ports are opened and closed by the up and down movement of the piston. To accomplish a complete power cycle both sides of the piston are used; consequently several events occur simultaneously during each stroke. 5. On the up stroke the top side of the piston is compressing an air/fuel mixture in the cylinder. At the same time the bottom side of the piston pulls another fresh charge of air/fuel mixture into the crankcase thru a one way valve called a reed valve. Near the top of the stroke the compressed air/fuel above the piston is ignited by the spark plug and begins to burn. The rapidly burning fuel expands and begins forcing the piston down. 6. On the down "power" stroke the piston is forced towards the crankcase reducing its volume and creating a positive pressure. As it continues downward travel it starts first to uncover the exhaust ports. Exhaust gas begins to rush out of the cylinder. Then the intake ports are uncovered. The fresh air/fuel charge in the crankcase is forced into the cylinder and continues to push the remaining exhaust gases out. Systems 7. Following systems are available in OBM‟s. a. b. c. d. e. Electrical system Fuel system Cooling system Power transferring system Lubrication system 64 සීමාන්විතයි Electrical System 8. There are 02 types of electrical ignition system. a. Contact breaker ignition system. b. Capacitor discharge ignition system. Contact Breaker Ignition System 9. This system contains with under mentioned accessories. a. Fly wheel & magnet. b. Charger coil c. Lighting coil d. Capacitor e. Ignition coil f. Spark plug 10. The magnets are fixed on the fly wheel and when fly wheel rotates these magnets are generating magnetic fluxes. This magnetic flux gets contact with charger coil which is fixed in stator plate. Because of that 230 AC current will generate. This current converts in to DC current at rectifier. 11. After converting in to DC current, it will store inside the capacitor. The electrical circuit will complete through contract breaker. Then stored DC current flows ignition coil. There are 02 coils inside the ignition coil, those are a. Primary coil b. Secondary coil 12. The voltage increases up to 50000, when it passes from primary coil to secondary coil. Finally this current flows up to spark plug. Capacitor Discharge Ignition System 13. This system is the most common method of ignition system use in OBMs and it consists with under mentioned accessories. a. Fly wheel & magnet b. Pulsar coil (sensor coil) c. Charger coil d. Lighting coil e. CDI unit (power pack) f. Ignition coil 65 සීමාන්විතයි g. Spark plug 14. 230 AC current will generate by charger coil by disturbing to the magnetic flux. This 230 AC current will flows to CDI unit. 230AC current converts into 170 DC current by rectifier inside the CDI unit. This 170 DC current will store inside the capacitor. As piston moment, the pulsar coil generates 0.3 AC current. This current flows to SCR and complete the circuit. Stored current at capacitor flows to ignition coil. The voltage will increase up to 50000 DC when current flows from primary coil to secondary coil. Thereafter the produced current flows to spark plug. 15. Magnetic field is generated around the secondary coil when current passes through the primary coil. The interruptions of the current flow through the primary coil induce a current (at 50000VDC) to jump across the electrode. Lubrication System 16. Mist Lubrication system Mist lubrication system is using to lubricate the machinery parts. In this system, lube oil mixing with fuel generally in 1:50 ratio. 17. Types of Lubrication oil Using a. b. c. d. 2T oil Caltex super out board motor oil Caltex TCW 3 out board motor oil Quicksilver two cycle oil 66 සීමාන්විතයි Fuel System 18. The unique feature of the fuel pump of OBM is that, the pumping action is taking place inside the pump by the suction & compression of the pistons of the engine. The pump consists of two diaphragms, one inlet & one out let valves. On the upward movement of the piston, suction is created inside the crank case. Due to this the diaphragm of the pump is pulled back. In return diaphragm creates vacuum in its front chamber. It causes the inlet valve to open & fuel enters into the front chamber of the diaphragm because of the atmospheric pressure. 19. When the piston moves down, it compresses the intake charge in crank case. This pressure forces the diaphragm in the forward direction. There by the fuel in front chamber of the diaphragm is compressed, inlet valve closes & fuel is forced out to the pulsation chamber and through outlet valve it goes to the float chamber of carburetor. 20. The carburetor is the metering device for mixing fuel and air. At the idling speed the engine requires a mixture of about 8 parts of air to 1 part of fuel. At high speed the mixture ratio is about 12:1. A throttle valve controls the volume of air fuel mixture in to the engine. A chock valve is placed behind the throttle valve to cater for a rich mixture for starting of the engine. 67 සීමාන්විතයි Cooling System 21. Cooling system consists of the following components: a. Water pump b. Thermostat c. Water manifold 22. The water pump is located at the top of the gear case and is driven directly by the drive shaft. The pump has a rubber impeller. The cooling system consists of one warning nipple and one thermostat. 23. Warning nipple is for monitoring whether the cooling system is functioning properly or not. If water does not come through the warning nipple immediately after starting the motor, at once stop the engine and rectify the defect. It is prohibited to run the OBM when water pump is not working. Thermostat functions at 45°C to 60°C. Gear Box Construction 24. The gear box consists of one bevel pinion and two drive gears. The engine power is transmitted to the propeller through the bevel pinion and drive gears. The two drive gears are mounted on the propeller shaft and are supported on bearings. A dog clutch mechanism is adopted to engage the desired gear with the propeller shaft so as to rotate the propeller gear shifting lever is provided to shift the gears for ahead or astern direction. 25. The bevel pinion and drive gear teeth ratio is to increase the power at propeller. The propeller is mounted on the splined propeller shaft. There are double oil seals to prevent oil leakage at the shaft ends. 68 සීමාන්විතයි Classification of OBM’s 26. An OBM can divide in to 03 parts as per the construction. a. Short tail Centre part of the OBM is short. These kind of OBM‟s are using for light crafts (Eg. RFD‟s). These OBM‟S are using for shallow water operations. b. Long tail Centre part of the machine is longer than short tail OBM‟s. c. Extra-long tail Mid-section of the machine is longer than long tail OBM‟s, using for deep sea operations. 27. Types of OBM’s using in SLN a. b. c. d. e. f. 28. Starting Procedure a. b. c. d. e. f. g. h. 29. Johnson Yamaha Suzuki Evinrude Mariner Mercury Check the Engine weather it is properly installed. Check the fuel line and fuel level. Ensure oil is mixed with fuel in correct ratio. Check the Engine for any disturbances. Check the propeller blades for any damages. Keep the gear leaver in Neutral position Keep the throttle handle in Start position. Keep the switch at correct position. Points to be checked when started a. b. Check the cooling system. Check for any abnormal sounds or vibration. 69 සීමාන්විතයි