BE (Mech), MEO Class - I (M)

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© Atul Kumar Gupta 2020 All rights reserved All rights reserved by author. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the author. Although every precaution has been taken to verify the accuracy of the information contained herein, the author and publisher assume no responsibility for any errors or omissions. No liability is assumed for damages that may result from the use of information contained within. First Published in January 2020 ISBN: 978-93-89763-23-2 BLUE ROSE PUBLISHERS www.bluerosepublishers.com [email protected] +91 8882 898 898 Cover Design: Vandana Kanyal Distributed by: BlueRose, Amazon, Flipkart, Shopclues

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Author is indebted to shipping industry for providing a satisfying and rewarding career first at sea and once again while being involved in maritime training. Author has learnt to work with safety while onboard and is committed to promote the safety culture through this book for ensuring safer ships and cleaner seas. In return to various achievements which have been possible through the shipping industry, author dedicates this book to young mariners for ensuring safe and sustained growth of the shipping industry.

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ACKNOWLEDGEMENTS Author is indebted to numerous learned and distinguished people for their invaluable support through their work which has undoubtedly contributed and enriched the contents of this book. Several publications have been the main source of knowledge for the author apart from his own experience at sea while on board ships and also while teaching this subject at International Maritime Institute, Greater Noida. The eminent authors listed here have been and will continue to be the mainstay. The author recommends the readers of this book to refer undermentioned publication for further studies. Marine Steam Boilers - J.H. Milton and Roy M. Leach Marine Boilers - G.T.H. Flanagan The Running & Maintenance of Marine Machinery - Cowley Introduction to Practical Marine Engineering - The Society of Naval Architects and Marine Engineers D.A. Taylor - Introduction to Marine Engineering H.D. McGeorge - Marine Auxiliary Machinery Author expresses his gratitude to his batchmates and colleagues at International Maritime Institute, Greater Noida for guiding him and providing the necessary support while writing this book. Author is thankful to his students who have helped him by sharing various images from the internet and details of their ships collected during afloat training, to make the book more illustrative. Atul Kumar Gupta iv

PREFACE TO THE FIRST EDITION This book is aimed to provide theoretical and practical knowledge about the marine boilers which have been in use earlier and being used presently. Author has included more than 100 illustrations for clarifying the minute details about the boilers and associated auxiliary machinery. The book covers the syllabus of Marine Boilers specified by Indian Maritime University, Chennai for 4th Semester of B.Tech (Marine Engg.) Course to achieve the following competencies as required by STCW 2010. Competency No. 4

Operate Main & Auxiliary machinery and associated control system (Table A-III/1)

4.1.4

Marine Boiler

4.3.2

Steam boiler and associated auxiliaries and steam systems Manage the operation of propulsion plant machinery. Plan and schedule operations. Operation, surveillance, performance assessment and maintaining safety of propulsion plant and auxiliary machinery. (Table A-III/2)

4.4D 4.5(14) Competency No. 9 9.3.4 9.3.5

Design features and operative mechanism of marine steam boiler. Heat cycle, thermal efficiency and heat balance of marine steam boiler. Maintenance and repair of shipboard machinery and equipment (Table A-III/1) Repair and maintenance of Main and Auxiliary Boiler including economizer. Boiler water maintenance and tests.

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Author has tried to make the subject easy to understand by using simple language and sharing his practical experience gained on ships and while teaching this subject at International Maritime Institute, Greater Noida, with an objective that this book will be useful for the students not only in passing their exams but the knowledge acquired by them can be used on ships while practically working on the boilers.

Atul Kumar Gupta

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CONTENTS

1. Boiler design considerations ............................... 1 2. Smoke tube boilers ……………………………….25 3. Water tube boilers.............................................. 35 4. Hybrid, composite & exhaust gas boilers …..….84 5. Boiler mountings & accessories ........................ 98 6. Refractory and water walls .............................. 144 7. Oil burning process ......................................... 154 8. Tests on boiler ................................................ 180 9. Boiler feed water system ................................ 186 10. Boiler control system ...................................... 220 11. Operation, care & maintenance ...................... 233 12. Alphabetical topic wise index.......................... 255

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CHAPTER 1 BOILER DESIGN CONSIDERATIONS A boiler is a closed vessel containing water which is heated to convert into steam. On application of heat, the force of attraction between the molecules of water decreases and they separate to convert into steam. Kinetic energy of these molecules exerts force on the containing walls thereby exerting pressure on it. The energy released by burning the fuel in boiler furnace is stored as temperature and pressure in the steam produced. All boilers have a furnace or combustion chamber where fuel is burnt to release its energy. Air is supplied to the boiler furnace for combustion of the fuel to take place. A large heating surface area is provided for quick transfer of heat from combustion of fuel to the water. All modes of heat transfer i.e. conduction, convection and radiation are utilised in the boiler. A drum is provided where steam and water can separate. There are controls to ensure that fuel oil, air and feed water supplies are matched to meet the steam demand. There are a number of mountings which ensure the safe operation of the boiler. Fig. 1.1 symbolically distinguishes between production of saturated and superheated steam. Water is first heated to obtain the saturated steam in the boiler drum. Saturated steam is again reheated with the flue gases to obtain the superheated steam.

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Fig. 1.1 Saturated steam is obtained from boiler drum which is suitable for heating or miscellaneous purposes. Saturated steam may be further heated which is termed as superheated steam and used for obtaining mechanical work with the help of steam turbines. Fig. 1.2 describes different phases of steam on the Temperature - Entropy diagram. Water is supplied in the steam drum along saturated liquid line which receives latent heat and leaves the steam drum along saturated vapour line. Steam may be further heated as per the requirement, which then receives sensible heat in the superheated steam zone. Tip of the curve represents critical point which occurs at 220.6 bar corresponding to 374oC. Zone above the horizontal line passing through critical point is called as supercritical zone.

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Fig. 1.2 Steam generated in supercritical zone is beyond the scope of this subject as this heat exchanger is termed as steam generator instead of a boiler. Many thermal power plants worldwide are operating on supercritical steam. Usual operating pressure of these plants is above 250 bar. Supplied feed water is completely converted into steam in the heat exchanger and there is no reserve space for steam and water like a drum in a boiler.

USES OF STEAM ON SHIPS Steam may be put to use for any of the following purposes on ships. 1 2 3

For heating of fuel and lubricating oils on all ships. For heating and humidification of accommodation in winters on all ships. For heating of domestic water on all ships. 3

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9 10 11

12 13 14 15

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For blowing sea chest gratings on most ships to clear any debris / ice and permit the entry of cooling sea water in engine room. For blowing soot from heat transfer surfaces of large water tube boilers and exhaust gas economizer on some motor ships for increasing the efficiency of heat transfer. For extinguishing scavenge space fires on most propulsion engines by a process known as smothering. For preheating jacket cooling water on motor ships during port stay to keep the engine warmed up for easy starting. For cleaning of cargo tanks on oil and chemical tankers for change of grade or to prepare the ship for dry docking. For propulsion on steam ships, now restricted to liquefied natural gas carriers. For electric power generation on steam ships and some container vessels. For driving various pumps / equipment on steam ships and conventional oil tankers. (Conventional oil tankers are those ships which use steam turbine driven cargo oil pumps where as new oil tankers use submerged cargo oil pumps) For operation of winch & windlass on all steam ships and some conventional oil tankers. For operation of cargo oil pump turbine on most conventional oil tankers. For air extraction from vacuum condenser on steam ships and some conventional oil tankers. For operating steam driven reciprocating (stripping) pump on conventional oil tankers.

16 For cargo heating on chemical / petroleum / gas tankers and vaporizing liquefied gas cargo to facilitate cargo discharging or for using cargo as fuel in engine room. 17 For operation of ships whistle on steam ships and some conventional oil tankers to raise general alarm or to alert other ships in the vicinity. 18 For gas freeing / ventilation of cargo oil tanks on some conventional motor tankers to enable tank inspection / repair. 19 For production of distilled water for boiler on steam ships and motor ships during prolonged port stay if fresh water generator is equipped with steam heating arrangement. 20 For atomizing the fuel oil on large boilers of steam ships and conventional oil tankers. Main use of steam on motor vessels is for heating applications thus a small capacity auxiliary boiler is used for this purpose while the ship is in or around the port. When the motor ship proceeds to sea, exhaust gas boiler is used for this application. Oil fired boiler may assist exhaust gas boiler when engine is being operated at reduced capacity.

SELECTION OF STEAM PRESSURE Fig. 1.3 shows the amount of heat required to change the states of water i.e. from ice to water and then to steam. It is also observed that change of state from one phase to other occurs at constant temperature which is represented by its latent heat. Sensible heat component for the three phases are also shown.

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Fig. 1.3

Fig. 1.4 Fig. 1.4 represents Temperature / Pressure verses Enthalpy diagram for water / steam. 6

It can be observed from the diagram that boiling temperature of water rises as the pressure increases but the amount of latent heat of vaporization required per Kg of water reduces. Process of feed water heating (1-2), evaporation into steam (2-3) and superheating (3-4) are represented on the diagram. For producing mechanical power using steam turbines, only the sensible heat can be utilized which means all the latent heat supplied is wasted in the condenser. As the component of sensible heat is much smaller as compared to latent heat, efficiency of steam turbine is very low which can be improved by raising steam inlet pressure thereby reducing latent heat component and reducing the exhaust pressure by which more sensible heat can be utilized. Usual steam pressure suitable for steam propulsion turbines ranges between 100 to 110 bar. Steam Pressure

Steam Temp.

100oC

Specific Enthalpy @ Saturation Point 2676 Kj/Kg

Atmospheric Pressure 4.5 bar 9.5 bar 16 bar 100 bar -0.05 bar

Specific Enthalpy @ 500oC 3488 Kj/Kg

155.5oC 178oC 204.3oC 311oC 32.9oC

2752 Kj/Kg 2778 Kj/Kg 2793 Kj/Kg 2727 Kj/Kg 2561 Kj/Kg

3483 Kj/kg 3478 Kj/kg 3470 kj/kg 3374 kj/kg -

Above table lists typical steam pressures maintained on motor / steam ships for specific applications which are described below. 7