Modern marine engineer manual volume i

Steam at 212°F has more internal energy than liquid water at the same temperature.. Properties of Pure Substances Most engineering systems employ a working fluid of some kind to port ene

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Copyright © 1999 by Cornell Maritime Press, Inc.

All rights reserved No part of this book may be reproduced in any

manner whatsoever without written permission except in the case of

brief quotations embodied in critical articles and reviews For

information, address Cornell Maritime Press, Inc.,

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Library of Congress Cataloging-in-Publication Data

Modern marine engineer's manual - 3rd ed / Everett C Hunt, editor

-in-chief; contributing editors, Gus Bourneuf, Jr [et al.]

p em.

Includes bibliographical references and index.

ISBN 0-87033-496-4

1 Marine engineering I Hunt, Everett C.,

1928-II Bourneuf, Gus.

VM600.M65 1999

CIP

Manufactured in the United States of America

First edition, 1941 Third edition, 1999

For the Regiment of Midshipmen

at Kings Point, New York

In memory of Jay

FOREWORD : xv PREFACE TO THIRD EDITION : xvii PREFACE TO FIRST EDITION : xix

Engineering Material Requirements 2-1 Engineering Material Types 2-3 Engineering Material Manufacturing Processes 2-41 Material Properties and Performance 2-46

vn

viii CONTENTS

CHAPTER 3

Steam Power Plants

J ames A Harbach

Actual Marine Steam Power Plants 3-7

Steam Power Plant Systems 3-21

Steam Power Plant Operating Procedures 3-31

Bearing Lubricants and Lubrication Systems 4-37

Bearing Installation and Maintenance 4-59

Bearing System Condition Monitoring and Troubleshooting 4-68

Boiler Components and Construction 5-26

Boiler Automation Systems 5·49

Steam Turbine Construction 6-25

Rotor Vibration Modes and Amplitude 6-44 Propulsion Turbine Operation 6-45Propulsion Steam Turbine Operating Problems 6-48

Propulsion Gas Turbines 7-30

Safety Considerations During Bunkering 8-14

Emissions Testing and Control 8-25

Mechanical Fuel Treatment 8-30

Chemical Fuel Treatment 8-34

Operational Problems in a Diesel Engine Fuel Oil System 8-39

Summary Approach to Shipboard Fuel Problems 8-39

Reduction Gear Principles 9-13

Gear Tooth Loading and Stresses 9-18

Propulsion Reduction Gear Construction 9-21

Transmission System Monitoring 9-36

Gear Inspection and Repair Using a Plastic Hone 9-49

Shipboard Engineering Operations 13-4

Shipyard Repairs and Overhauls 13-11

ERM-Engine RoomResource Management 13-76

Shipboard Computer Applications 13-82

Computerized Maintenance Management

Eugene D Story and Donald A Dailey

Appendix to Chapter 15 15-49

APPENDIX : A-I INDEX

The term "global economy" has been much overused to describe manythings-the rise and fall of financial powers, the redistribution ofwealth, streamlining, downsizing, and more-all suggesting a relativelynew phenomenon However, global economy is still largely about interna-tional commerce-trade across the seas-as it has been for centuries Andtransport across those seas continues to be done by high-capacity ships ca-pable of moving cargo over long distances Commerce always involves abalance of factors such as superior materials, skilled labor, low cost, andstate-of-the-art technology These factors can be readily modeled and ana-lyzed using computer software costing as little as a semester at a local col-lege The interaction of variables has been examined sufficiently so thatpatterns of trade or specifics of vehicle selection can be fine-tuned for vi-ability Sea trade remains the favored method of global transport; the over-whelming majority of international commerce is still carried by ships, as ithas been for nearly three millennia

Over the last quarter-century, technical developments and economies

of scale have resulted in dramatically lower costs for building, propelling,and loading ships; the attendant labor cost components are becoming al-most the sole determinant of competition among the world's fleets Materi-als for shipbuilding can now be produced, refined, and shipped anywhere

at such low cost that sourcing differences are insignificant Much of thecredit for this progress goes to advancements in areas closely aligned withand including marine engineering

Ships-those remarkable, self-contained, floating cities-still face thetimeless challenges associated with the sea No other mode of carriertransport is required to function reliably and continuously at full power forlong periods and have the capability for adequate maintenance and repair

to be done in-situ Ships must be designed so that basic ship functions can

be carried out at untoward angles of trim or heel and despite the ing orientations caused by pitching or rolling Engineering considerationsare complicated by ever-increasing engine cycle temperatures furthercompounded by salt-laden combustion air; engineers must continuallystrive for the economy to be gained from using lower-quality fuels

alternat-xv

New challenges appear at a brisk pace While ship operating economy

continues to favor lower-paid and potentially less-skilled crews, these

same individuals are still expected to be knowledgeable about the

increas-ingly complex ships they sail The extensive use of shipboard electronics

and the expansion of international safety criteria have significant

poten-tial for worldwide benefit, but they also present additional concerns

re-garding the day-to-day operations of ships of all sizes and types These

operating realities further challenge those who design, build, and manage

ships

This book offers the fundamental elements required to help engineers

stay current on ways to benefit from the technological advances occurring

in these rapidly changing times The third edition of volume 1 of the

Mod-ern Marine Engineer's Manual is a superb up-to-date reference for

stu-dents and practicing professionals alike It incorporates state-of-the-art

changes that have been implemented since the publishing of the second

edition, with emphasis in appropriate areas Written by experts in marine

engineering and the relevant academic fields, it is authoritative and

con-tains a significant amount of high-caliber input

DavidA O'NeilPresident, 1997-1998The Society ofN aval Architects and Marine Engineers

Preface to Third Edition

The first edition of volume 1 of Modern Marine Engineer's Manual was

published on the eve of World War II to provide a useful and practicaltext for the engineering officers, students, port engineers, and ship repairspecialists of a rapidly expanding American merchant marine The secondedition, published twenty-four years later, provided useful updates of theoriginal text Due to dramatic changes in all aspects of ship machinery andship operations during the past thirty years, this third edition is not a revi-sion of past editions but an entirely new text written in the tradition of ear-lier editions All the contributing editors are experts in the areas for whichthey have prepared chapters Many are employed as consultants; othershold academic appointments in their fields

The diesel engine-now the most popular form of main propulsion tem-is covered in volume 2 The third edition of volume 1 remains primar-ily a source of information on steam and gas turbine power plants Thereciprocating steam engine is no longer covered in the text, and the mate-rial on steam turbine propulsion has been reduced However, gas turbinemain propulsion has been covered in detail in the expectation that thistype of power plant will become increasingly popular as new environ-mental regulations continue to require the use of higher-quality fuel, con-tributing to improved economics for the gas turbine It is possible that gasturbines combined with heat recovery steam generators and steam tur-bines may become the most popular propulsion system for cruise liners.Also covered in this newest edition is the personal computer, which israpidly becoming essential shipboard equipment for many tasks, includingspare parts management, maintenance programs, vibration analysis, powerplant analysis, management systems for quality and safety, communica-tions, and record keeping

sys-International, national, and local laws and regulations concerning theprotection of the environment and the safety of shipboard personnel andproperty plus the rules of classification societies and flag states all combine

to provide a new challenge to ships personnel Shipboard systems designed

to comply with many of these requirements (including ISO 9002 and theISM code) are described in the text

xviii PREFACE TO THIRD EDITION

Pumps, pumping systems, and heat exchangers, which are found on all

types of ships, are given extensive coverage

Petroleum fuels are frequently treated chemically and processed

me-chanically on modern ships The characteristics of fuels, fuel chemical

treatment, fuel mechanical processing, and the implications of such

treat-ments and processes for the maintenance of both internal combustion

en-gines and boilers are presented

Since shipboard equipment in most ofthe world is manufactured to the

metric system, metric measurements are used along with the traditional

American units of measure

In recognition of the use of the text by students, each chapter includes

review questions as well ~s references to materials for further study

The editors wish to thank all the companies and organizations who

gave permission for the use of illustrations and other material in this

edi-tion The names and locations of these companies are acknowledged at the

end of each chapter

Preface to the First Edition

The expansion of shipbuilding made evident about four years ago thatthere was need of an American textbook on marine engineering thatwould adequately explain the design and operation of all the general types

of marine equipment and at the same time should be written simply, to beeasily understood Because marine engineering was, and is advancing andchanging so rapidly, it was necessary that a considerable amount of theory

be included in order that the student be prepared to understand future velopments in the field of marine engineering There was the thought too,that for effective use in this time of stress, it would have to be widely dis-tributed among the shipyard and seagoing personnel This meant that theprice ofthe book had to be such that the men could pay

de-At this point, it may be mentioned that methods of study of a technicalbook are very important if useful results are to be obtained A certain timeshould be set aside each day for study This may be interfered with by out-side emergencies, but every effort should be made to adhere to it A shortsection of the book should be read through completely each day Then itshould be re-read and important words underlined in pencil The drawingsmay then be copied in the notebook

It may also be mentioned that many men "look, but see not." Every man

in the "black gang" should be able to sketch on paper the position of everyimportant piece of equipment in the engine room of his ship and know theposition of every important control and valve

More and more marine engineering design is breaking up into ties and this is the reason that this book is written by a number of men Theauthors of the various chapters of the book are specialists, each on his sub-ject, some are engineers of the U.S Maritime Commission and others areengaged in various outside branches of the maritime industry Anyone ofthe authors of the manual will be glad to answer any difficult point thatmay be brought up in regard to his specialty Should the student wish toreach one of them he should write care of the Cornell Maritime Press

special-It will be noted by those familiar with the subject that a large use hasbeen made of the instruction pamphlets of the U.S Navy This use wasmade both because of the short time available to prepare this manual andbecause of the excellence of the Navy material

xx PREFACE TO THE FIRST EDITION

The experienced marine engineers will notice the omission of many

ex-cellent pieces of marine equipment from these pages This was due to the

sharp necessity for conserving time and printed space In regard to printed

space the editor believed that a full description of a single type of

equip-ment to be greatly preferred to cursory and inadequate descriptions of the

products of all the various manufacturers That a piece of equipment is

pre-sented in this book does not mean that the author prefers it to some other

piece of equipment that may not be mentioned It may but illustrate the

point of the subject better

The thanks of the editor go out to the splendid cooperation he has

re-ceived from the authors of the chapters, from the publishers, from all

branches of the marine industry without exception and from his superiors

in the U.S Maritime Commission

Grateful acknowledgment is hereby made to those companies which

have supplied us with data and illustrations concerning their products:

[The remaining paragraphs of the preface were devoted to an extensive

list of companies and organizations that were of help to the editor.]

Volume I

[Alan Osbourne]

thermody-The analysis and design of energy systems require the use of all three ofthe thermal sciences For example, the overall performance of a refrigera-tion system can be analyzed using only the principles of thermodynamics,but the design ofthat system's thermostatic expansion valve relies heavily

on the use of fluid mechanics, and determining the surface area of its denser and evaporator requires the use of heat transfer principles

con-THERMODYNAMICS

Definitions and Units

Before a study of thermodynamics can begin, a brief review of some basicdefinitions and unit systems is necessary

SUBSTANCES

Most energy systems are based on the use of a working substance to carryenergy from one location to another A pure substance is one that has thesame chemical and physical composition at all points A steam power plantuses water, a pure substance, in its operation Air is used as the workingsubstance in many systems, for example, an open-cycle gas turbine Air isnot a pure substance but a mixture of oxygen, nitrogen, and several otherinert gases

1-1

1-2 THERMAL SCIENCES AND ENGINEERING

CLOSED AND OPEN SYSTEMS

A thermodynamic system is defined as a collection of matter or space If agiven mass of substance is defined as the system, this is referred to as aclosed system Air expanding in a piston-cylinder would be most easilyanalyzed as a closed system If a given volume is defined as the system, this

is referred to as an open system A section of pipe with water entering andexiting is an example of a fixed-volume or open system Note that in aclosed system, only energy crosses the system boundary In an open sys-tem, both energy and mass cross the system boundary It is important tonote that the selection of the system boundaries determines whether thesystem is open or closed These boundaries can be selected based on theanalysis to be performed

PROCESSES AND CYCLES

A process is the change in the state of a system from one point to another.There are an infinite number of ways of getting from state one to state two.The intermediate states that the system goes through describe the path Twoexamples of common processes are constant-temperature and constant-pressure In the first, the temperature is the same constant at all systemstates In the second, the pressure is unchanged A series of processes can

be put together to return to the same system state Such a series of cesses is called a thermodynamic cycle (see fig 1-1)

pro-UNIT SYSTEMSEngineers work with numbers daily Dimensions are normally associatedwith those numbers, defining the value of properties such as length, pres-sure, and temperature The two measurement systems in common use are

the English engineering system (U.S customary units) and the Systeme

International D'unites (SI) system.

Units are either fundamental or derived The fundamental units aredefined and form the basis ofthe unit system All other units are then de-

1-4 THERMAL SCIENCES AND ENGINEERING

Note that in the SI system, a conversion constant (gc) is not required toachieve consistent units Since the standard acceleration of gravity is

9.807 mlsec 2, one kg of mass "weighs" 9.807 newtons at sea level

TEMPERATURETemperature scales were originally based on the freezing and boilingpoints of pure water at standard atmospheric pressure In the English en-gineering system, water freezes at 32°F and boils at 212°F In the SI sys-tem, water freezes at ooe and boils at lOOoe

A temperature scale can also be defined with absolute zero (the lowestpossible temperature) as a zero reference For the Rankine absolute tem-perature scale, each degree division is the same as the Fahrenheit scale.Since absolute zero is -459.67°F, water freezes at 491.67°R and boils at671.67°R The absolute SI temperature scale is Kelvin Water freezes at273.15°K and boils at 373.15°K A comparison of the four temperaturescales is shown in figure 1-2

PRESSUREPressure is defined as the normal force per unit area The most commonunit of pressure in the English engineering system is pounds of force per

1-10 THERMAL SCIENCES AND ENGINEERING

that since there was no change in elevation there was no change in

poten-tial energy Kinetic energy is calculated as follows:

One of the more difficult forms of energy to understand is internal energy

Internal energy is a measure of the internal activity of the molecules in the

system It includes such things as the vibrational and rotational

move-ment of the molecules The difficulty is that it is impossible to measure

these molecular energies directly They must be measured indirectly, by

measuring such things as the temperature or phase of the fluid A liquid

has more internal energy when hot than when cold Steam at 212°F has

more internal energy than liquid water at the same temperature Internal

energy is usually given the symbol U.

Another energy term that must be considered is flow energy This is the

work done to push mass into or out of an open system Flow energy is the

product of pressure and volume:

Wflow = pV = pmu

In most open-system problems, both internal and flow energy terms

ap-pear together It is convenient to define a new property called enthalpy,

which is merely the sum of the two:

H = U + pV

or for a unit mass:

h = u + pu

Enthalpy is commonly tabulated for various fluids such as steam and

refrigerants There is a temptation to think of enthalpy as heat, which it is

not It is merely the sum of u and pu.

The following example illustrates the use of many of the energy terms

just defined and their application to the first law of thermodynamics

EXAMPLE1-2: A steam turbine is supplied with 5,000 lbm/hr of steam at

an enthalpy of 1,400 Btu/lbm and a velocity of 100 ftlsec The steam

ex-hausts at an enthalpy of 950 Btu/lbm and a velocity of 900 ft/sec

Deter-mine the horsepower produced

Properties of Pure Substances

Most engineering systems employ a working fluid of some kind to port energy from one location to another If the fluid has a constant compo-sition, regardless of phase, it is referred to as a pure substance The mostcommon pure substance used as working fluid in engineering systems iswater The water can exist as a liquid, a vapor (steam), or a solid (ice) In allsituations it is still H20

trans-In addition to the three phases, a pure substance like water can exist as

a mixture of two phases A glass of ice water has H20 in both the liquid andsolid phases Imagine starting with 1 pound of ice at OaFand standard at-mospheric pressure (14.696 psia, or 101.325 kPa) Let's add heat to the ice.Initially, as heat is added, the temperature of the ice increases At 32°F(O°C) something different happens-the ice begins to melt Energy isadded but the temperature stays constant as the water undergoes a phasechange from solid to liquid It takes 144 Btu of energy to completely meltthe 1 pound of ice

As further heat is added to the 32°F (O°C)liquid, the temperature gins to rise again, until a temperature of 212°F (lOO°C)is achieved As fur-ther heat is added, a second phase change takes place The water boils,again undergoing a phase change at constant temperature Mter the addi-tion of another 970 Btu, the water has been completely turned to vapor at212°F-"saturated steam." If we now add more energy to the steam, itstemperature will begin to rise again, resulting in "superheated steam."

be-It is important to note that the water in the example above would haveboiled at a different temperature if the pressure had not been 14.696 psi a

1-12 THERMAL SCIENCES AND ENGINEERING

(101.325 kPa) If the pressure had been 1 psia, it would have boiled at101.6°F If the pressure had been 100 psia, the water would have boiled at327.8°F This relationship between saturation temperature and pressure

is very important and forms the basis for the operation of many systems Itallows us to make distilled water from seawater in a flash evaporator andboil refrigerant-12 in the evaporator of a refrigeration system and keepmeat frozen

STEAM TABLESTables 1-2, 1-3, and 1-4 provide the properties of saturated and super-heated steam Table 1-2 presents data for saturated vapor and liquid withsaturation temperature as the input variable Table 1-3 presents the satu-rated vapor and liquid data with the saturation pressure as the input vari-able Note that properties with the subscript "f"are for saturated liquid,

properties with the subscript "g" are for saturated vapor, and those withthe subscript "fg" are for the difference between the two For example, hfg isthe difference between the enthalpy of saturated vapor and saturated liq-uid at the tabulated temperature or pressure Table 1-4 presents data forsuperheated steam and compressed water with pressure and temperature

as the inputs

In order to determine the properties of a mixture of saturated vapor and

liquid, the quality x must be used Quality is the ratio of mass of vapor to

the total mass of the mixture For example, the enthalpy of a mixture can

EXAMPLE 1-3: Steam is expanded in a turbine from 900 psia and 900°F to

1 psia The exhaust has 10 percent moisture Determine the energy tracted from each pound of steam in Btu

ex-Solution: Using table 1.4 for 900 psia and 900°F,

h= 1,452.2 Btujlbm

Using table 1.3 for 1 psia and x = 0.9

h f =69.73 Btu/lbm, hg = 1,036.1 Btujlbm,

h= 69.73 + (0.9)(1,036.1) =1,002.2 Btujlbm

THERMODYNAMICS 1-17

Second Law of ThermodynamicsThere is nothing in the statement ofthe first law of thermodynamics thatinfers there is any limitation on the direction of energy flow or the conver-sion of one form of energy to another It is the second law that provides suchlimitations For example, a hot and a cold metal block are placed into an in-sulated box Ifwe opened the box an hour later, we would not be surprised

to find two warm blocks But the opposite is not true Ifwe put two warmblocks in the box and opened it an hour later, we would not expect to findone hot block and one cold block

Another important limitation of the second law concerns the conversion

of work to heat, and vice versa Ifwork is supplied to a system, it is possiblefor it to be completely converted to heat But the opposite cannot happen It

is impossible to devise a system that will convert all the heat supplied to itinto work Any engine must reject or exhaust some of the heat supplied tothe surroundings In other words, some of the energy supplied to the en-gine is "unavailable" to perform work Another way of stating this implica-tion of the second law is that the thermal efficiency of a heat engine must beless than 100 percent

THE CARNOT CYCLEThe Carnot cycle represents a hypothetical heat engine that provides anupper limit on the conversion of heat supplied into work A real engine op-erating between the same two temperature limits can have a thermal effi-ciency that approaches, but does not exceed, that ofthe Carnot cycle.The Carnot cycle, shown in figure 1-4, consists of the following four pro-cesses:

• 1-2 reversible constant-temperature heat addition

• 2-3 reversible adiabatic expansion

• 3-4 reversible constant-temperature heat rejection

• 4-1 reversible adiabatic compression

The thermal efficiency of the Carnot cycle can be calculated using thefollowing equation:

1-20 THERMAL SCIENCES AND ENGINEERING

A useful tool in analyzing processes is the Mollier chart, a plot of the thalpy of a substance versus its entropy Figure 1-5 is a Mollier chart forsteam The dark curved line in the middle of the graph is the saturationline The region above this line is the superheated steam region Mixtures

en-of saturated steam and liquid lie below this line Lines of constant perature and pressure in the superheat region and lines of constant tem-perature and moisture in the saturated steam and liquid region aid inlocating points on the chart

tem-EXPANSION PROCESSAssume a fluid is being e:wanded in a turbine, producing power If the ex-pansion process is ideal, with no losses (Le., reversible) and with no heattransfer to the surroundings (adiabatic), the entropy of the fluid at the out-let will be the same as that at the inlet This is referred to as an isentropic(constant entropy) process It will plot on the Mollier chart as a verticalline See the process 1 to 28 in figure 1-6

THERMODYNAMICS 1-23

A calorimeter is a device for measuring the enthalpy of steam A mon variety used for measuring the enthalpy of wet steam with a smallamount of moisture is the throttling type One of the difficulties with wetsteam is that the temperature and pressure are not independent proper-ties One additional property is necessary to determine the state of thesteam Figure 1-9 shows a typical throttling calorimeter Wet steam underpressure is expanded into a chamber at atmospheric pressure As thesteam is throttled, it becomes superheated The enthalpy of the super-heated steam can now be determined using the superheated steam tableswith the steam's temperature and pressure Since the process across thevalve is throttling, the enthalpy of the superheated steam in the chamber

com-is the same as that of the wet steam in the line The mocom-isture (or quality)can be calculated using the following equation:

1-34 THERMAL SCIENCES AND ENGINEERING

TABLE 1·7 Viscosity Conversions

Universal Centipoise Furol No.1 No.2

The units of absolute viscosity in the English system are Ibf-sec/ft2•

In the metric system, the basic unit of absolute viscosity is the poise(poise = gm/cm-sec)

In fluid mechanics, the ratio of absolute viscosity 11 to density p oftenarises This ratio is called the kinematic viscosity v Since density is massdivided by volume (length3), the usual unit of kinematic viscosity in theEnglish system is ft2/sec, and in the metric system is the stoke (cm2/sec).Over the years, a number of other units of viscosity have become com-mon in engineering practice Many of these are based on a particulardevice developed for measuring viscosity For example, the Saybolt visco-simeter uses the time it takes a 60-cc sample offluid to pass through an ori-fice of a particular size The units are SSU (Saybolt Seconds Universal) andSSF (Saybolt Seconds Furol) Other similar units are Redwood No.1 andNo.2 and degrees Engler Table 1-7 provides some useful conversionsamong some common units of viscosity The viscosity of most fluids variessignificantly with temperature Figure 1-13 shows the viscosity of somecommon liquids as a function of temperature

HEAT TRANSFER

Heat transfer-the flow of thermal energy from one location to plays an important role in the operation of many engineering systems Ifthe exchange of energy is the result of a temperature difference, the trans-fer of heat is said to have taken place Ifheat is being transferred from onebody to another, the first law of thermodynamics requires that the internalenergy given up by the first body be equal to that taken up by the second.The second law ofthermodynamics requires that the heat flow be from thehot body to the cold body

another-The processes that govern heat transfer are commonly termed duction, convection, and radiation Almost all situations encountered inengineering practice involve two, or sometimes all three, modes of heat

con-transfer Conduction is the term applied to the exchange of internal energy

within a body, or from one body in contact with another, by the exchange ofenergy from one molecule to another by direct communication In conduc-tion, the heat transfer takes place within the boundaries ofthe bodies and

there is no observable movement of the matter making up the bodies

Con-vection is the term applied to heat transfer caused by the mixing of one

por-tion of a fluid with another as the fluid moves While the exchange ofenergy from one molecule to another is via conduction, the energy is trans-

ported from one location to another by the movement of the fluid

Radia-tion is the term applied to the exchange of thermal energy from a warmer

body to a cooler body through electromagnetic radiation The important

1-36 THERMAL SCIENCES AND ENGINEERING

difference between radiation and the two modes discussed above is that theheat transfer can occur without the need for a medium of transport be-tween the bodies For example, the earth receives heat from the sun acrossmillions of miles of vacuum by thermal radiation

Conduction

Conduction was defined above as the movement of thermal energy within asubstance with no displacement of the material While conduction can oc-cur in a fluid, it is most commonly observed in solids A simple example ofheat transfer by conduction is the steady-state flow of heat through asolid wall Figure 1-14 shows a wall with a thickness ofLlx with constant

1-38 THERMAL SCIENCES AND ENGINEERING

can be made are that liquids are better conductors than gases, solids are

better conductors than liquids, and solid metals are better conductors than

nonmetals It should be remembered that the thermal conductivity is not

constant; for most materials it will vary with temperature and sometimes

pressure Use caution in applying tabulated values at temperatures

differ-ent from those listed

A situation commonly encountered is a wall composed of several layers

of different materials of different thicknesses Figure 1-15 shows a wall

constructed ofthree layers of different materials Under steady-state

con-ditions, the heat flow through each layer must be the same

Table 1-9 lists some typical values of the convective film coefficient forair and water in common situations Note the wide range of values listed.Some general observations can be made First, the film coefficient ishigher for water (a liquid) than for air (a gas) Second, the film coefficient

is higher when a phase change is taking place (boiling or condensing)than when there is only a change in fluid temperature Third, the highervelocities of forced convection result in higher film coefficients than freeconvection Determining the value of the film coefficient to use in a par-ticular situation requires judgment and experience There are a number

of good texts and reference books on heat transfer (including

Fundamen-Note that each of the terms in the denominator of the above equationhas been modified to adjust for the varying area This equation should beused for heat transfer through a cylinder whenever there is a significantdifference between the inside and outside diameters.

Log Mean Temperature Difference

Heat exchangers are used in a wide variety of marine engineering systems.They are used to cool lubricating oil, to heat fuel oil, and to condense steam.Consider a tube-in-tube heat exchanger with one fluid flowing in the centertube cooling the fluid flowing in the annulus between the tubes The fluidsare arranged to flow in the same direction, or parallel-flow (see fig 1-18).The heat transferred across the tube area is equal to heat lost by the hotfluid and also equal to heat gained by the cold fluid:

HEAT TRANSFER 1-45

If the direction of flow of one of the fluids in the tube-in-tube heat changer is reversed, it becomes counter-flow Figure 1-19 shows a counter-flow heat exchanger with its temperature distribution Like the parallel-flow heat exchanger, the mean temperature difference across the tube is

ex-the lmtd This is also true for heat exchangers where one or both of ex-the

flu-ids are undergoing a phase change as in a steam turbine condenser or inthe evaporator of a refrigeration system For many other configurations,

1-46 THERMAL SCIENCES AND ENGINEERING

such as a shell-and-tube heat exchanger with multiple tube passes, a

cor-rection factor must be applied to the lmtd Any text on heat transfer or heat

exchanger design will contain procedures for calculating the lmtd

correc-tion factor for common heat exchanger configurations

EXAMPLE1-10: A counter-flow heat exchanger is to cool 10,000 lbm/hr of

oil with aCpof 0.8 Btu/lbm-F from 190°F to 120°F Water is used to cool the

REVIEW

1 Explain the difference between weight and mass

2 Define absolute pressure, gauge pressure, and vacuum

3 How are density and specific volume related?

4 What is the continuity equation for steady flow?

5 How does power differ from work?

6 In your own words, define the difference between heat, internal ergy, and enthalpy

en-7 What is the importance of the Carnot cycle?

8 What is a Mollier chart?

9 Briefly describe the three modes of heat transfer

10 What is the overall heat transfer coefficient? What two modes of heattransfer does it combine?

REFERENCES

Burghardt, M D., and J A Harbach 1993 Engineering Thermodynamics,

4th ed New York: HarperCollins

Chapman, A J 1987 Fundamentals of Heat Transfer. New York: millan

Mac-EI-Wakil, M M 1984 Powerplant Technology New York: McGraw-Hill.

Fox, R W., and A T McDonald 1992 Introduction to Fluid Mechanics, 4th

ed New York: John Wiley & Sons

Schmidt, F W., R E Henderson, and C H Wolgemuth 1984

Introduc-tion to Thermal Sciences New York: John Wiley & Sons.

CHAPTER 2

Engineering Materials

ENGINEERING MATERIAL REQUIREMENTS

Historically, many different, naturally occurring materials have beenused to develop devices and components of engineering systems Ex-amples include early use of wood to make beams, shafts, rods, nails, or pinsand pipes; stone for building gravity structures such as foundations, col-umns and arches; and fibers to make flexible materials such as rope, fabric,orjoint sealants such as caulk Copper, lead, iron, and tin were also used inancient times for making pipes and tools; lead pipes were used in Romanwater systems, copper provided the basis for bronze using tin, and iron car-burized in fires, or alloyed and tempered, was used to make early steels fortools, swords, armor, and other war implements It is known that lead wasused about six thousand years ago in Egypt Writings of early civilizationsrefer to the use of iron, a rare metal derived from ores as early as three tofour thousand years ago In modern times, earlier generations learned thatimportant structural elements, such as ship's hull structure and rigging,engine components, foundations and casings, pressure vessels and fit-tings, shafts, rods, plates and beams, and the like, must be constructedfrom materials that are durable, readily worked, and have properties al-lowing flexible and reliable service Because of the marine environment'sseverity, knowledge ofthe nature of materials and their important physi-cal, mechanical, thermal, chemical, electrical, and nuclear properties (nu-clear properties will not be treated in this chapter), and understandinghow to use that knowledge to develop reliable engineering constructions,have been major engineering concerns essential to successful develop-ments

In this chapter, consideration of engineering materials is restricted tosolids, materials that can be used structurally to resist, support, isolate, or

2-1

2-2 ENGINEERING MATERIALS

transfer loads Fluids are engineering materials as well, their application

also designed in engineering practice and their properties precisely

de-fined in order to plan for their efficient use However, fluids do not resist

shearing forces, i.e., forces acting transverse to a body's axis, undergoing

large deformations if so loaded, making fluids unsuited for resisting or

transferring many applied loadings Thus, only solid materials are treated

here

On first studying physics, students treat bodies as being rigid; they

as-sume bodies do not deform when acted upon by forces Actually, all bodies

deform when acted upon by forces To be suitable for engineering systems,

loaded-material deformations must be generally small and predictable As

naturally occurring materials are found inadequate in many respects (in

strength, toughness, ductility, or corrosion resistance) there has been a

continuing thrust to develop new materials more suitable for systematic

use in component and system designs To select materials that will be

sat-isfactory for resisting, supporting, or transmitting applied forces over a

system's expected lifetime, mechanical and related material properties

must be known and duly considered

All force applications are dynamic to a greater or lesser degree, even

when the forces are applied for long time periods and generally considered

static In addition to force magnitude, the speed or frequency with which

forces are applied, and the duration oftheir application, influence material

response These effects, too, need to be understood and considered in

sys-tem design

In engineering systems, energy is converted from one form to another

Chemical energy can, for instance, be converted into thermal energy, then

into mechanical energy, then into electrical energy, and back into

me-chanical energy Materials respond to thermal as well as meme-chanical

load-ings They expand or contract when heated or cooled, and if heated to high

temperatures or cooled to low temperatures their mechanical properties

generally change significantly as well Metals lose strength and melt if

heated to high enough temperatures and may become brittle and more

readily fracture if cooled to very low temperatures In designing thermal

systems then, the effect of temperature on material properties needs to be

known and considered

It is generally more difficult and expensive to produce and use

materi-als ofhigh purity Pure materimateri-als may not have the properties sufficient for

particular applications; the properties may in fact be undesirable in some

way, readily oxidizing or undesirably interacting with other materials, for

instance By understanding the chemical characteristics of materials, it is

possible to mix them to form alloys to obtain the most desirable

perform-ance in specific applications

Chemical interactions of materials typically involve sharing or

ex-change of charged particles and free electrons This may result in electrical

current flows between and through materials It is important then to derstand and quantify material electrical characteristics so considerationcan be given to them in system design and undesirable interactions can beprevented from causing system performance deterioration Componentisolation is necessary to produce thermally efficient systems and to pre-vent unwanted thermal exchanges between system elements

un-Material weight (expressed as density or in terms of specific gravity) isanother important physical factor All weights must be sustained by liftforces; for displacement-type ships, these forces are called buoyancy Butproviding lift is not without cost Thus lighter-weight materials such asbalsa wood, aluminum, titanium, and glass-reinforced plastic (GRP) haveinherent advantages due to their light weight, high strength, and competi-tive cost in certain applications

Engineering material property investigations are routinely conductedand their results are systematically presented in technical literature Se-lection of materials suitable for application in a system design should con-sider the following (not necessarily in this order):

• available material types

• material properties (density, mechanical, thermal, chemical, cal)

electri-• material quality, consistency ofcharacteristics, and ease ofevaluation

• service requirements materials must meet (strength, toughness,corrosion resistance)

• material workability and susceptibility to manufacturing processes

• material performance reliability in the system environment

• relative costs of finished materials

ENGINEERING MATERIAL TYPES

The list of materials available for application is extensive, with propertiesthat are wide ranging in density, stiffness, strength, ductility, malleabil-ity, machinability, joinability, notch toughness, conductivity, interactiv-ity, and more Materials are typically grouped into metals, nonmetals, andcomposites Metals in the pure element forms are frequently undesirablefor direct use and are therefore typically combined with other elements toform alloys; due to the importance of iron as a widely used material, metalalloys are further classed as ferrous or nonferrous Alloys are formed withcharacteristics making them suitable for typical or special-service environ-ments: hot or cold, wet or dry, static or dynamic Production processes to pre-pare materials for use, and a material's final shape, can affect serviceperformance as well Thus, most metals in marine services are alloys, whose

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elements are chosen to enhance parent metal properties and provide foreasier producibility and improved in-service performance

In addition to traditional metals, metal alloys, and such naturally

oc-curring nonmetals as wood and stone, a variety of plastics and ceramics arenow available Newly available also are composites, which are composed ofmore than one material Glass- or fiber-reinforced plastic (GRP or FRP),for example, is a modern class of material being used in a widening range ofapplications; the fibers are immersed in a resin matrix fixing the com-posite's geometry The fibers provide the strength while the matrix pro-vides fiber adhesion affording axial force transfer between fibers by shear.Available fibers include, in addition to glass, more exotic products such asDacron, Mylar, Kevlar, and carbon fiber Table 2-1 lists a number of ele-ments, along with their approximate specific gravities, melting and boilingpoints, crystalline structure, elastic moduli, and other characteristics,which are used sometimes in pure form but more typically in alloyed forms

Basic Elements

Most metals used in marine engineering systems are alloys of aluminum,copper, iron, lead, nickel, tin, titanium, and zinc, although pure forms ofthese metals are often used as well Copper, gold, and silver are sometimescalled "noble" metals as they do not oxidize readily; gold and sometimescopper are found in the free state, as is platinum Pure metals tend to bemore expensive to produce, typically requiring refining to obtain the de-sired purity, and may be inadequate in strength; however, they often pos-sess good ductility, conductivity, and other desirable properties To obtainmaterials better suited for specific engineering use, these basic metals aretypically combined with small amounts of other metal elements such as an-timony, chromium, cobalt, magnesium, manganese, and tungsten to im-prove strength, machinability, corrosion resistance, and other properties,while not seriously reducing ductility, toughness, or other attributes and

increasing fatigue resistance if possible In addition to the metal elements,

such nonmetals as carbon, silicon, and sulfur are used in developing alloysthat have desired properties

In the pure state, the metallic atoms arrange themselves in randomly

oriented crystal structures as they solidify into grains, with many tions developing between the crystal grains Of particular significance tomarine materials are the face-centered cubic (FCC), body-centered cubic(BCC), hexagonal close-packed (HCP), and tetragonal crystalline struc-tures Antimony forms in a rhombohedral lattice Figure 2-1 illustratesseveral crystal structure atomic arrangements It is noteworthy that allthe FCC metals have generally good ductility, a desirable characteristic forengineering system components, whereas HCP and some BCC elementsare brittle or become so at low temperatures The minimum elongation ofmaterials before rupture, a measure of material ductility, is frequentlyspecified as a criterion for material selection

disloca-2-8 ENGINEERING MATERIALS ENGINEERING MATERIAL TYPES 2-9

Commercially useful metals are usually found in igneous rock ore

formations composed of mixtures of metallic and mineral compounds Some

typically occurring, commercially exploitable mixtures such as

nickel-cobalt-silver, iron-magnesium, zinc-cadmium, lead-chrome, lead-molybdenum, and

aluminum-silicate, are found in particular regions of the world The metals

are usually found in such compound forms as arsenates, sulfides, and

ox-ides or in combinations with other metals Such metals as copper, gold,

platinum, and silver are frequently found or may occur only in a free state

Meteorites are about 90 percent iron and 6 percent or so nickel, and it is

be-lieved the earth's core has a similar content

Reduction of ores to prbduce metals typically entails crushing,

wash-ing, concentratwash-ing, smelting, roasting, fusing, dissolving, precipitating,

electrolytic reduction, or refining To carry out these processes, suitable

fluxes, oxidizers, reagents, and other chemical substances must be brought

into play Some limited notes on these are given in the following sections

More detailed information on processes and material properties can be

found in inorganic chemistry reference texts such as those listed at the end

of this chapter (the older works are still useful in understanding materials

and their properties) Many errors and inaccuracies are found in the

litera-ture and no complete reference is known; only approximate values are

given here to provide readers with reasonably reliable information

ALUMINUM

Aluminum is the most abundant metallic element in the earth's crust,

be-ing the third element in abundance in igneous rocks at about 8.1 percent

Aluminum oxide is the fourth most abundant compound in the earth's

crust The element is typically found in nature combined with others, such

as potassium, in the form of silicates Bauxite, Al2nH20, is an important

component in the metal's production, which is usually by electrolysis of its

aluminum oxide; aluminum production facilities are typically located near

hydroelectric or coal-fired power plants where electric power is less

expen-sive As produced, aluminum is nearly pure, about 99+ percent, and lacks

many structural abilities that would make it most desirable At the atomic

level, its crystalline structure is face-centered cubic (FCC) and this

pro-motes certain properties: it is very ductile, even at very low temperatures,

and very malleable (only gold is more malleable) Aluminum can be rolled

into very thin sheets, called "foil," and is easily extruded into specially

shaped sections This lends itself to production of structural and

architec-tural shapes, as for trim items Mter extrusion, the shape is typically

passed through straightening rolls, removing twists or curvatures Due to

its softness and low melting temperature, aluminum is readily cast and is

found in many shipboard outfitting items, though usually as an alloy

Relatively soft, aluminum has a Brinell hardness of about 20 and a

rela-tively low yield stress, about 5,000 psi (34.47 MPa), and ultimate strength,

about 13,000 psi (89.63 MPa) in its annealed condition Being quite ductile,

it undergoes a 35 to 45 percent elongation before rupture Due to its lowstrength and light weight (specific gravity =2.7), the pure metal cannot beused to full advantage When alloyed, aluminum can be heat treated or me-chanically worked to obtain more desirable properties However, thestrength of heat-treated or cold-worked material tends to revert to the an-nealed condition if heated above its recrystallization temperature Easilymachined, it takes on a high initial polish; the surface rapidly develops anoxide coating which then retards further oxidation

Nearly pure aluminum (about 99.5 percent) is used for electrical ductors Having less electrical conductivity (63 percent, i.e., electrical re-sistivity is 1.6 times greater) than copper, which has a specific gravity of8.94, but with lighter weight, it is pound-for-pound about twice as good aconductor However, its thermal expansion coefficient is 1.55 times that ofcopper; if in-service thermal variations are significant, care must be taken

con-to keep electrical connection devices tightened

At ambient temperatures, aluminum oxidizes readily, forming an oxidecoating on its surface that protects (shields) the metal from further oxida-tion, even when the metal is melted At higher temperatures, however, theoxide, in the presence ofthe liquid metal, may be ignited by an arc or flame.Thus, if electrical arcs are formed, as in a faulty electrical connection, themetal will readily melt and can ignite (undergo extremely rapid oxidation),initiating fires in adjacent combustible materials More discussion of thismetal and its properties is given below in the section on alloys

ANTIMONY

Known of in ancient times, antimony was not clearly identified until theseventeenth century While not rare, its occurrence is still only about0.002 percent, about the same as for cadmium It is mainly obtained fromits sulfide mineral, stibnite, by crushing and roasting An inexpensive,relatively hard (about 2.2 times as hard as tin), but easily scratched andbrittle metal of bluish-white color, antimony flakes readily Having a lowmelting temperature, the metal alloys easily with most metals and isused as a hardener of tin in making babbitt, antifriction metal, pewter,and white metal, and oflead in making hard metal, type metal, and bat-tery plate It expands on solidifying and is thus useful in reducing shrink-age, better filling mold volumes when cast Tin-antimony solder, with amelting point of about 450°F (232°C), is suitable for soldering copper tub-ing joints in potable water plumbing systems Antimony's compressibil-ity is about the same as that of lead

CADMIUM

Typically, cadmium is found in zinc ores in a concentration of about 0.5percent, though it is sometimes found in a more pure form as a cadmium

2-10 ENGINEERING MATERIALS

sulfide It is often produced as a by-product of zinc production as it is more

volatile and more easily reduced in the zinc smelting process; most

cad-mium, however, is produced by the electrolysis of zinc Cadmium is a

silver-white metal that is not as hard as but more ductile and malleable than zinc

It polishes to a high luster but tarnishes gradually as the surface oxidizes It

is often used for anticorrosion plating of wire, tools, and other steel products

If the items are subsequently heat-treated, the cadmium alloys with the

iron, giving about the same corrosion resistance as is found in zinc plating

(galvanizing) Cadmium becomes rather brittle at higher temperatures and

is frequently used as a substitute for tin in bearing metals It is sometimes

used in small amounts to.strengthen copper (otherwise relatively weak), as

small amounts do not significantly increase copper's resistivity

CHROMIUM

A highly corrosion- (oxidation-) resistant material, chromium is used

ex-tensively to electroplate steel and other metals to reduce surface oxidation

and to make corrosion-resistant chromium (stainless) alloys of steel for

service at normal as well as elevated temperatures As a pure metal, it has

a luster similar to that of platinum, taking on a brilliant polish Chrome ore

is found in igneous rocks in a concentration ofless than 0.04 percent, most

importantly in the form of a ferrous chromite, and it is usually obtained by

first fusing the ore with sodium carbonate to form a sodium chromate It

can then be reduced in an electric furnace Harder than iron and annealed

nickel and a little less so than copper, chromium has the effect

ofincreas-ing the hardness of steel when the steel is rapidly quenched, and it

in-creases the wear resistance of cutting-tool steels when 1.5 to 2.5 percent

chromium is added to the steel

COBALT

Cobalt, a silver-gray metal, is ductile and malleable and is found mainly in

nickel-cobalt-silver ores, although common cobalt minerals such as those

with arsenic and sulfur, like CoAsS, are more generally found with iron

ores The ore is smelted with a suitable flux in a blast furnace, which

pro-duces the unrefined liquid silver metal and an amalgam of arsenides of

several metals such as cobalt, iron, or copper This amalgam is then

sub-jected to various roastings, using salt to form a chloride of cobalt which can

then be extracted with water Cobalt can be precipitated as a hydroxide,

which in turn can be reduced to the metal with carbon It has important

uses in making high-strength, structural alloys for use in high-temperature

applications As an alloy with chromium and tungsten, it is important in

making high-speed cutting tools

COPPERCopper is sometimes found in its elemental state, certainly providing the ba-

sis for its use by early civilizations in making bronzes Copper also (in some " -_

regions predominantly) occurs in the form of sulfide and oxide ores.Crushed native copper ores can be mechanically concentrated and then pu-rified by melting with an appropriate flux Oxide ores are heated in a fur-nace and smelted with coke and a suitable flux The sulfide ores are moredifficult to reduce as there is typically some iron present The purest coppercan be obtained by electrolytic processing to produce nearly 100 percent purecopper Copper has a face-centered cubic crystalline structure and retainsits ductility through a broad temperature range, having an elongation of 45+percent at ambient temperatures before rupture

As a pure element, its thermal and electrical conductivities are verygood, though not as good as those of silver Copper is competitively priced

in world markets and is extensively used in electrical applications such asconductors and motor windings, but primarily in its nearly pure form, assmall amounts of impurities can significantly reduce its electrical conduc-tivity

Although copper is quite ductile, in its annealed state it is quite weakand soft, with a yield stress of less than 10,000 psi (68.95 MPa) and aBrinell hardness number of about 40 Because of its low yield stress andductility, it is easily extruded into tubes and rolled into sheets It work-hardens when plastically deformed, raising its yield strength, but becomesmore brittle and less fatigue resistant, making it unsuitable for dynamicloading as in a vibratory environment Because of copper's relatively lowrecrystallization temperature (about 250°F [121°C] depending on howmuch plastic straining it has experienced), work-hardened items can beannealed if desired by heating above the recrystallization temperatureand quenching in water, thus allowing grain growth and restoring its soft-ness and ductility Because of its very good thermal conductivity, it is ex-tensively used in heat transfer components, particularly tubing products.Copper is highly resistant to corrosion under ambient conditions and isextensively used for alloys As discussed below, the alloys typically retainthis corrosion-resistant property

GOLD

Produced for over six thousand years, gold is a relatively rare metal, tuting only about 5 parts per billion in the earth's crust, and with quite un-even distribution It frequently occurs in rich concentrations in native form

consti-as flakes and nuggets in lode and alluvial deposits It is found consti-as a pound only in various telluride forms or in quartz veins Much metal is re-covered as a by-product of extraction processes during production ofcopper, lead, nickel, silver, and zinc Most countries have some gold; almosthalf have some production Seawater also contains some gold, about 0.014micrograms per liter Having a distinctive deep yellow color and an FCCcrystal lattice, it is relatively heavy, strong, and soft and is the most malle-able and ductile of metals (one cubic inch of pure metal can be rolled or