MARINE BOILER AND STEAM ENGINEERING Prepared By P.THANGA SABARI AP, Marine MSEC

1. MARINE BOILER AND STEAM ENGINEERINGPrepared ByP.THANGA SABARIAP, Marine MSEC

2. Marine Boiler and Steam Engineering OBJECTIVE To make the students understand the concepts and working of boiler ,steam engines ,steam turbines and their maintenance. At the end of the module the students are equipped with the knowledge of, • Marine boilers and its types. • Steam engines and their working principle. • Steam turbine and its working principle.

3. BOILER • A boiler is a closed vessel in which water is heated to produce steam. USES OF STEAM ONBOARD • FUEL OIL HEATING • DOMESTIC FRESH WATER HEATING • TO RUN STEAM TURBINES • SOOT BLOWING • MAIN ENGINE PRE HEATING • ACCOMODATION HEATING • GALLEY

4. UNIT 1 VARIOUS TYPES OF BOILERS AND BOILER MOUNTINGS • TYPES OF BOILERS • BOILER MOUNTINGS

5. BOILER • A boiler is a closed vessel in which water or other fluid is heated for produce steam. • A boiler or steam generator is a device used to create steam by applying heat energy to water.

6. USES OF STEAM • PRODUCED ELECTRICITY IN TURBINES • PRE HEAT THE OIL IN SHIPS • STEAM ENGINES • FOOD INDUSTRIES

7. Types of marine boiler; Based on the flow of gases and water; • 1. Fire tube boiler • 2. Water tube boiler Based on the position of boiler • 1. Horizontal boiler-axis of the boiler is horizontal • 2. Vertical boiler- axis of the boiler is vertical • 3. Inclined boiler –axis of the boiler is inclined Based on the mode of tiring: • Externally fired boiler • Internally fired boiler

13. FIRE TUBE BOILERS • SCOTCH BOILER • COCHRAN BOILER • SPANNER BOILER • COMPOSITE BOILER

14. WATER TUBE BOILER • LAMONT EXHAUST GAS BOILER • COMPOSITE BOILER • BABCOCK WILCOX BOILER • FOOSTER WHEELER-D-TYPE BOILER • DOUBLE EVAPORATION BOILERS.

15. COCHRAN BOILER • These boilers essentially consist of one or more fire tubes passing through a cylindrical shell which may be horizontal or vertical and is filed to at least half of its volume with water. • Cochran boiler • Simple vertical boilers of the fire tube type find favour in small plants requiring small quantities of steam and where the floor area is limited. The most common applications are steam rollers, pile drivers, steam shovels, portable hoisting rigs and certain other mobile applications. • CONSTRUCTION • Cochran boiler, illustrated in Fig.1, provides an excellent example of the improved design of vertical, multi-tubular, internally fired natural circulation boiler. • The Cochran boiler essentially consists of: • (i) Boiler shell with hemispherical crown, • (ii) Furnace, fire box and grate, • (iii) Combustion chamber and flue pipes, • (iv) Smoke box and chimney; and • (v) Connections for boiler mounting and accessories,

16. CONSTRUCTIONAL AND OPERATIONAL DETAILS The unit consists of a cylindrical shell with a dome shaped top where the space is provided for steam. The shell is formed of steel plates joined together with the rivets. Both the circumferential and longitudinal joints are lap joints made steam tight by fullering or caulking operation. The fuel is burnt on grate in the furnace provided at the bottommost part of boiler. The furnace has no riveted seams exposed to flame and is pressed hydraulically from one plate to finished shape. This makes the furnace suitable to resist the intense heat produced by the combustion of fuel. The grate consists of iron bars which are arranged with spacing between them. The spacing allows the air to pass onto the fuel for combustion. The firebox is hemispherical so that the unburnt fuel, if any, is deflected back to the grate and complete combustion is achieved. An ash pit is attached beneath the furnace for collecting ash after regular intervals. The boiler can be arranged to burn almost any kind of fuel including wood, paddy husk and oil fuel. For operation as an oil fired unit, an oil burner is fitted at the fire hole. The grate is then dispensed with a lining of fire brick is provided beneath the furnace.

19. The coal, on burning, produces hot flue gases and these hot products of combustion from the fire box enter through the small flue pipe into the combustion chamber which is lined with fire bricks on the outer wall of the boiler. The lining prevents the shell from being damaged due to the overheating. • The dome shaped furnace and the combustion chamber prevent the loss which could otherwise occur because of combustion being retarded and much unburnt and combustible matter leaving the furnace. The unburnt fuel is deflected back to the grate and complete combustion, is achieved in combustion chamber where the high temperatures are maintained. • The hot gases passing through the horizontal smoke tubes give their heat to the water and in doing so convert water into steam which gets accumulated in the upper portion of the shell from where it can be supplied to the user. The flue tubes are generally of 62.5 mm external diameter and are 165 in number. The crown of the shell is made hemispherical in shape which gives the maximum space and strength for a certain weight of material in form of plates. • Finally the flue gases are discharged to the atmosphere through the smoke box and the chimney. The smoke box door enables the cleaning and inspection of the smoke box and fire tubes. Through a manhole provided at the crown of the shell, a man can enter the boiler for periodic cleaning and maintenance of the boiler. There are connections provided at appropriate places for fixing the usual boiler mounting such as pressure gauge, water level indicator, safety valve, steam stop valve, feed check valve and blow off cock etc.

20. SCOTCH BOILER

21. Scotch Marine Boiler • Scotch marine boiler is a fire tube boiler. It is also a scotch or tank type boilerwhich is used for the marine works. The reason behind, it is used for marine work is its compactness, efficiency in operation and its ability to work in any type of water. Brick work setting and external flues are not required in scotch marine boiler.Types  It is of two types:1. Single Ended2. Double Ended  Single Ended Scotch Marine Boiler: • The length of the single ended steam boiler may be upto 3.5 m • The single ended steam boiler contains one to four furnaces and these furnaces enter from the front end of the boiler. Double Ended Scotch Marine Boiler: • The length of double ended steam boiler is upto 6.5 m. • In double ended scotch marine boiler, the furnaces are present on both of its ends. And the number of furnaces varies from 2 to 4 in each end.

22. Construction • The various parts of scotch marine boiler are as follows1. Furnace: It is used to burn the fuel inside the boiler. A single ended scotch marine boiler is fired with four furnaces. The furnaces are generally corrugated for strength. Each furnace has its own combustion chamber.2. Combustion chamber: It is portion of the boiler where the combustion of the fuel takes place. There are fine plates in the combustion chamber , which require staying i.e. the top plate, back plate, two side plate and the tube plate. There are number of smoke tubes placed horizontally and connect the combustion chamber to the chimney.3. Smoke box: The smoke box has numbers of smoke tubes which is placed horizontally and connects the combustion chamber to the chimney. The smoke passes through these smokes tubes and finally enters into the chimney.4. Chimney: It is used to exhaust the smoke and burnt gases out of the boiler. The exhaust gases is released into the environment through chimney.5. Boiler shell: The boiler shell is made up of steel plate. It protects the internal parts of the boiler. All the important fittings of the boiler are fitted on the boiler shell.

24. Working of scotch boiler:The fuel is inserted into the furnace through the fire hole. The fuel in the furnace is ignited through the fire hole. The burnt fuel enters into the combustion chamber. • Here the combustion of the fuel takes place. The heat generated into the combustion chamber is used to heat the water surrounding the combustion chamber. The water gets converted into steam and it is supplies to steam turbine. The exhaust gases after combustion passes through the smoke tubes and reaches to the chimney. • The chimney releases these smoke and exhaust gases into the atmosphere. In the scotch marine boiler the water surrounds the furnace, combustion chamber and smoke tubes and due to this it provides the greater heating surface to the water. .

25. For better understanding lets discuss its working step by step.First the fuel is inserted into the furnace through the fire hole and here it is ignited. • The fuel is burnt on the furnace and hot burnt gases are generated. This hot burnt gas enters into the combustion chamber. A large amount of heat is generated into the combustion chamber. The heat form the combustion chamber use to heat the water surrounds it.  • The water gets converted into steam and made to pass on the steam turbine. • The water surrounds the furnace, combustion chamber and smoke tubes and due to this the scotch marine boiler provides a greater heating surface for the water. • The burnt exhaust gas passes to the chimney through smoke tubes.  • The chimney releases these exhaust gases or smoke in the atmosphere. • In this boiler the level of water is maintained a little above the combustion chamber

26. Application • This boiler is generally used in marine works and on ships. This is because of its compactness, efficiency in operation and its ability to work in any type of water.Advantages • The various advantages of scotch marine boiler are as follows:It is compact in size. • It has good efficiency in operation. • It has the ability to work in any type of water. • Brick work setting and external flues are not required in scotch marine boiler

27. SPANNER BOILER

28. COMPOSITE BOILER • Composite marine steam boiler Composite marine steam boilers are combination of oil-fired boilers and exhaust gas economizers

30. WATER TUBE BOILERS

31. LAMONT BOILER

32. Principle: • This boiler works on basic principle of forced convection. If the water is circulate by a pump inside the tube, the heat transfer rate from gas to the water is increases. It is the basic principle of it. Construction: • This boiler is the first force circulation boiler. This boiler consist various part which are as follow.

33. Economizer: • Economizer use to preheat the water by using remaining heat of the combustion gases. It increases the boiler efficiency. The feed water first supplied to the economizer before entering to the boiler. • Centrifugal pump: • The Lamont boiler is a force convection boiler. So a centrifugal pump is used to circulate water inside the boiler. This pump is driven by a steam turbine. The steam for the turbine is taken by the boiler. • Evaporator tube: • The evaporator tube or can say water tubes are situated at furnace wall which increase the heating surface of boiler. This is also at the up side and down side of the furnace and other equipment. The main function of these tubes to evaporate water into steam.  This also cools down the furnace wall.

34. Grate: • The space in the furnace where the fuel is burn is called grate. It is bottom side of furnace. • Furnace: • In the Lamont boiler vertical furnace is used. The main function of Furnace is to burn the fuel. • Super heater: • The steam generated by the evaporator tube is saturated steam. If it directly used in steam turbine can cause the corrosion. So the saturated steam sends to the super heater where it can increase the temperature of steam. • Water steam separator drum: • The steam separator is situated outside from the boiler. The mixture of water and steam from the evaporator tube send to the steam separator where it separate the steam and send it to super heater. The remaining water again sends to the economizer. • Air preheater: • It’s main function to preheat air before entering into furnace.

35. Working: • Lamont boiler is a forced circulation, internally fired water tube boiler. The fuel is burn inside the boiler and the water is circulating by a centrifugal pump through evaporator tubes. The working of this boiler is as follow. • A feed pump forces the water into the economizer where the temperature of water increases. This water forced into the evaporator tube by using a centrifugal pump driven by steam turbine. Water passes 10 - 15 times into the evaporator tube. The mixture of saturated steam and water is formed inside the tube. • This mixture sends to the steam separator drum which is outside the boiler. Steam from the separator sends to the super heater, where the saturated steam converts into superheated steam. The water again sends to the economizer where it again passes by the evaporator tubes. • The air from the air preheater enter into the furnace where fuel burn. The flue gases first heat the evaporator tube then passes by the super heater. These gases from the super heater again use to preheat the air into air preheater before exhaust into atmosphere. • This working pressure of this boiler is above 170 bar and have the steam generation capacity of about 50000 kg/hour at temperature 773 K .

37. Advantages: • 1. It can high pressure boiler. • 2. It is flexible in design. • 3. This boiler can reassemble in natural circulation boiler. • 4. It can easily start. • 5. It has high steam generation capacity of about 50 ton/ hour. • 6. This boiler has higher heat transfer rate.

38. Babcock and Wilcox boiler • Babcock and Wilcox boiler is a natural circulation, externally fired medium pressure, stationary horizontal water tube boiler in which water is flow in the inclined tubes. The furnace is located outside of the drum.   • This boiler is invented by Stephen Wilcox and George Herman Babcock in the year 1967. So this is named as Babcock and Wilcox.

39. Main Parts: • Babcock and Wilcox is a stationary water tube boiler. It has inclined tubes which are inclined at 10 to 15 degree, which are inclined to maintain natural circulation of water from drum to tubes and steam from tubes to drum. The main parts of this boiler are as follow. • 1. Steam separator drum: • This drum is situated upside of the boiler. It is larger diameter drum in which water and steam placed together. The one half of the drum is filled with water and the other half is remaining for steam. • 2. Water tubes: • Water tubes are situated bottom side of the drum. Water flows from the drum to the tubes. • 3. Uptake header: • Steam separator drum and water tubes are connected by the two tubes. One is known as uptake header and the other one is known as down take header. The steam from the water tubes to the drum flow by the uptake header. • 4. Down take header: • The water flows form the drum to the water tubes through down take header. When the steam flows by uptake header to the drum, at the same time water flows from drum to the water tubes by down take header which maintains the flow of water.

40. 5. Grate: • The place in the furnace, where the fuel is placed and burn known as grate. • 6. Furnace: • The furnace is the place where the fuel burns. This is situated at the down side of the water tubes. When the fuel burns, the flue gases generate. This gases flow upper side and passes through water tube, which heat the water and convert it into steam. • 7. Super heater: • Super heater is situated upper side of the water tube. One end of super heater is connected to the drum and other end is for process work. Steam flows from the drum to the super heater, where it heated by the flue gases and send for the process work. • 8. Baffles: • Baffles are provided between the water tubes. The main function of baffles is to divert the flue gases, so it flows more than one time through the tube and more heat is transfer. • Other mounting like safety valve, blow off valve, fuel door, inspection door, mud box, feed valve, stop valve, pressure gauge etc. are also provided for safely working of boiler.

42. WORKING: • Now we discuss about working of Babcock and Wilcox boiler. This is a high pressure, natural circulate, water tube boiler. The working of this boiler is as follow. • *  First water is filled in the water drum through feed pump. The drum is half filled with water and the upper half is for steam. • First flue is fired at the grate. • *   The flue gases generate by burning of fuel. These gases start flowing from one end to another end of boiler. • *   The flue gases passes by the water tubes and exchange heat with water. The baffles are provided in the way, which deflects the flue gases before escaping from the chimney. Due to this deflection, the flue gases pass more than one time through water tubes, which cause more heat transfer. • *   The water flows from the drum to the water tube through down take header.

43. *   The water tube nearer to the furnace heated more than the other, so the density of water decrease in this tube which causes the flow of  steam from tube to drum through uptake header. At the same time the water from the drum enters into the tubes through down take header. • *   The circulation of water from drum to tubes and again tubes to drum is natural, due to density difference. • *   The steam separates in the drum at the upper half. This is saturated steam. This steam sends to the super heater through steam pipe. The steam is heated again by the flue gases in the super heater and taken out for process work. • *   The flue gases send to the atmosphere from the super heater. • *   This process repeat until sufficient amount of steam generates. This boiler can generate 20 ton steam per hour.

44. Advantages: • 1. The steam generation rate is higher about 20 ton per hour at pressure 10 to 20 bars. • 2. The tubes can be replaced easily. • 3. The boiler can expand and contract freely. • 4. It is easy to repair maintenance and cleaning. • 5. It drought loss is low compared to other boiler. • 6. The overall efficiency of this boiler is high.

45. TIMBLE TUBE BOILER

46. TIMBLE TUBE BOILER • A thimble tube boiler is a form of steam boiler, usually provided as an auxiliary boiler or heat-recovery boiler. They are vertical in orientation and would be considered a form of water-tube boiler. • The characteristic feature of this boiler are its 'thimble tubes'. These are short horizontal water tubes, closed at one end and tapered.

47. Waste heat recovery calculation: • Only small percentage of energy in the fuel is ultimately converted into useful power . Mostly the energy in the fuel is dissipated into the surrounding as heat: • 1 to 2% is lost to the surrounding from hot surfaces. • Some heat is rejected with exhaust: • About 10% in steam plants. • About 25 to 30% in diesel plant. • About 65 to 70% in gas turbine plant. • Some heat is rejected to sea , via cooling water: • Up to 60% in steam plant mostly in condenser. • Up to 30% in diesel plant , at engine coolers. • Less than 1% in gas turbine plant, at lubricating oil coolers.

48. FOOSTER WHEELER BOILER-D-TYPE