The cupola furnace

Front matter

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Preface

Although it is now more than twenty years since the publication of the author's volume, " The Founding of Metals," that book is still in demand. The reception which has been tendered to it, together with the urgent requests of many foundrymen for a more modern work on cupolas, has encouraged .him to prepare the treatise now offered to the public.

This volume is designed to supply a want long felt, for a work on melting that would give practical details regarding the construction and management of cupolas, and the melting of iron for foundry work. Several valuable books have been written on the moulding and founding of iron and steel, but in these books, as in the foundry, but comparatively little attention is given to the cupola ; and foundrymen and melters have been left to grope very much in the dark, and to rely solely on their own experience, in the construction and management of their cupolas.

This condition of things, and the great importance of the subject, have combined to induce the author in the present work to endeavor to develop the most vital principles connected with the cupola, its construction and its use, together with the best practice of this country. In order to accomplish these ends, he has supplemented his almost lifelong experience by consulting the latest works on foundry practice, and by visiting leading and thoroughly up-to-date foundries in different parts of the United States. He therefore trusts that this book will prove to be a useful aid to foundrymen, whether owners or workers, both here and abroad.

( iii )

IV PREFACE.

As is the general custom of the publishers, they have caused the work to be supplied with a copious table of contents, as well as a very full index, which will render reference to any subject in it both prompt and easy.

EDWARD KIRK.

Philadelphia, February 22, i8gg.

CHAPTER I. The Cupola Furnace

PAGE

Advantages of the cupola furnace for foundry work; Quantity of fuel required for melting iron in various kinds of furnaces; Attempts to decrease the amount of fuel consumed in the cupola by utilizing the waste heat 1

Description of the cupola furnace; Forms of cupolas; Sizes of cupolas; Foundation of a large cupola ......... 2

Advantage of iron supports over brick-work; Height of the bottom of the cupola; Pit beneath the cupola 3

Bottom plate; Bottom doors; Support of the doors; Various devices for holding the doors in place; Construction of the casings ... 4

Stack casing; Construction of the stack; Tuyere holes .... 5

Location of the charging door and its construction; Lining of the casing and materials used for it .......'. 6

The scaffold and its location; Construction of the scaffold; Size of the scaflFold i

CHAPTER II. Constructing a Cupola

Proper location of a cupola; The scaflFold . ...... 8

Conveyance of coal or coke to the scaflfold; Cupola foundation and its construction 9

Prevention of uneven settling; Brick walls for the support of a cupola; Best supports for a cupola . 10

Height of cupola bottom; Provision for the removal of the dump; Bottom doors 11

Casing; Material for the casing or shell of the modern cupola and stack; Strain upon the casing due to expansion and shrinkage and its prevention; Contraction of the stack; Prevention of sparks . . .12

What constitutes the height of cupola; Utilization of the waste heat; Table giving the approximate height and size of door for cupolas of diflferent diameters ........... 13

Melting capacity of a cupola; Charging door; Air chamber . . .14 vi CONTENTS,

PAGE

Construction of the air chamber when placed inside the casing and when placed upon the outside of the shell; Air capacity of the air chamber; Admittance of the blast to the air chamber 15

Location and arrangement of the air chamber when the tuyeres are placed high; Tap-hole 16

Arrangement when two tap-holes are required; The spout and its construction; Tapping of slag 17

Location of the slag-holes ; Tuyeres ; Number of tuyeres for small cupolas ............. 18

Best shape of tuyere for a small cupola; Number of tuyeres for large cupolas ; Size of combined tuyere area ; Tuyere boxes or casings ; Height at which tuyeres are placed in cupolas ..... 19

Objection to high tuyeres; Two or more rows of tuyeres; Arrangement of a large number of rows 20

Area of the rows; Increase in the melting capacity with two or three rows of tuyeres; Lining; Material for lining the casing . . .21

Grouting or mortar for laying up a lining; Manner of laying the brick; Thickness of cupola linings; Stack lining ...... 22

Arrangement of brackets 23

Preference by many of angle iron to brackets; Mode of putting in angle iron; Reduction of the lining by burning out 24

Settling of the lining; Mode of reducing the size and weight of the bottom doors and preventing the casing from rusting off at the bottom; Prevention of the absorption of moisture into the lining . . .25

Illustration of the triangular-shaped tuyere in position in the lining; Form of bottom plates. Fire-proof scaffolds; Exposure of the scaffold and its supports to fire 26

Devices to make scaffolds fire-proof; Novel plan of construction of a scaffold and cupola house in Detroit, Mich 27

Best and safest scaff'olds; Cupola scaffold in the foundry of Gould & Eberhardt, Newark, N. J., and of the Straight Line Engine Co., Syracuse, N. Y 28

CHAPTER III. Cupola Tuyeres

Modes of supplying the cupola furnace with air; Admission of the air through tuyeres or tuyere holes; Former and present melting capacity

of a cupola; Epidemics of tuyere invention 30

The round tuyere; Arrangement of round tuyeres in the old-fashioned

cast-iron stave cupolas 31

Oval tuyere; Expanded tuyere 32

Doherty tuyere 33

Sheet blast tuyere; Horizontal slot tuyere; Mackenzie tuyere. . . 34 Blakeney tuyere 35

CONTENTS. Vii

PAGE

Horizontal and vertical slot tuyere 36

Reversed T tuyere or vertical and horizontal slot tuyere; Vertical slot

tuyere; Truesdale reducing tuyere . ....... 37

Lawrence reducing tuyere .......... 38

Triangular tuyere; Results in melting with this tuyere obtained by the

Magee Furnace Co., Boston, Mass 39

Water tuyere 40

Colliau tuyere; Whiting tuyere 41

Chenney tuyeres; The double tuyere; Mode of placing the tuyeres in

Ireland's cupola; Claims for the double tuyere 42

Consumption of fuel in a double tuyere cupola; Three rows of tuyeres;

Cupola constructed by Abendroth Bros., Port Chester, N. Y. . .43 Object in placing tuyeres in a cupola; Production of heat by consuming

the escaping gases from the combustion of fuel . . . . .44

Greiner tuyere; Adjustable tuyeres 45

Cupola of the Pennsylvania Diamond Drill and Manufacturing Co.,

Birdsboro, Pa.; Bottom tuyere ........ 46

Mode of covering the mouth of a bottom tuyere 47

Bottom tuyere patented in this country by B. H. Hibler; Thomas D.

West on the bottom tuyere 48

Size of tuyeres; Size of the combined tuyere area of a cupola . . .49 Height of tuyere; Great difference of opinion on this subject; Experiments with tuyeres at various distances above the sand bottom . . 50 Experiment to soften hard iron by bringing the molten metal in contact

with charcoal in the bottom of a cupola; Reason given in favor of high

Tuyeres in stove foundry cupolas; Location of tuyeres in smaller cupolas. 52 Tuyeres in machine and jobbing foundry cupolas, and in cupolas for

Number of tuyeres; Objection to the use of only one tuyere; Two tuyeres

sufficient for the largest cupola in use 54

Arrangement of a double row of tuyeres; Shape of tuyeres; Tuyeres to

improve the quality of iron 55

Tuyere boxes 56

CHAPTER IV. Cupola Management

Necessity of learning the peculiarities in the working of a cupola; A cupola cannot be run by any given rule or set of rules; Drying the lining 58

Drying a backing or filling between the casing and lining; Putting up the doors; Devices for raising the doors into place . . . .59

Support of double doors; Sizes of props to support the bottom . . 60

Vlll CONTENTS.

Ring attachment to the prop; Superstition of older melters regarding

the prop; Dropping the doors; Modes of releasing the prop . . 61 Sand bottom; Sand employed for this purpose; Objection to clay sands and other sands; Sand which makes the very best kind of bottom . 62

63 64 65

Wetting the bottom sand; Bringing the sand into the cupola .

Cause of leakage in the sand bottom .......

Boiling of iron due to a wet bottom; Pitch or slope of the bottom .

Effect of a high pitch; Change in the action of the iron at the spout by the pitch of the bottom; How the bottom should be made . . .66

Slope of the bottom in cupolas with two tap holes; Spout; Spout lining material 67

Effect of the use of too much clay or of too much sand in the lining; Mode of making up the spout lining ....... 68

Building up the sides of the lining; Place of the greatest strain upon the spout lining 69

Proper shape of the spout lining; Cause of pools of iron forming in the spout; Removal of slag from the spout ....... 70

Front; Material used for putting in the front; Mode of putting in the front 71

Eflfect of working the front material too wet; Troubles due to poor front material 72

Sizes of tap hole; Locating the holes . ....... 73

Slag hole 74

Slag hole front; Chilling of slag in the tap hole 75

Lighting up; Mode of placing the wood and shavings in the cupola; Patting in the bed fuel 76

Effect of carelessness in arranging the wood and lighting up . . .77

The bed; The melting point in a cupola; The melting zone and determination of its exact location; Necessity of discovering the melting point in order to do good melting 77

To find the melting point 78

Cause of trouble in melting after a cupola has been newly lined; Fuel required for a bed in cupolas of different diameters . . . .79

Charging; Old way of loading or putting the fuel and iron into a cupola; Modern way of stocking a cupola; Correct theory of melting iron in a cupola 80

Practical working of a cupola upon this theory ; Effect of too heavy charges of iron, and of too heavy charges of fuel; Variation in the ■weight of the first charge of iron 81

Variations in the per cent, of iron to fuel; Placing the charges . . 82

Mode of placing the pieces of pig or other iron ; Distribution of the charge of fuel; Charging additional iron ...... 83

Poor melting njay be due to bad charging; Improper and proper charging of a cupola; Charging flux; On what the quantity of flux depends 84

Blast; The old and the modern ways of giving blast to the cupola; Blast phenomena 85

CONTENTS. IX

PAGE

Melting; When melting begins in a cupola; Difference in opinion as to the time for charging the iron before the blast is put on . , .86

Best time for putting on the blast; Chilling and hardening of the first iron; Running of a heat without stopping in; Mode of reducing the size of the tap-hole 87

No advantage in holding molten iron in a cupola to keep it hot; Proper management of hand-ladle work; Indication of how the cupola is melting by the flow of iron from the tap-hole . . . . .88

Poking the tuyeres 89

Fuel; Amount of fuel required in theory and in practice; Necessity of keeping an accurate account of the amount of iron melted . . .90

Chief object of melting iron in a cupola; The old story of " not enough blast;" Necessity of an even volume of blast. ..... 91

Tapping bars; Shapes and sizes of tapping bars 92

Steel bar for cutting away the bod before tapping; Bod sticks; Combination stick 93

Objection to the combination stick; Number of bod sticks for each cupola; Bod material; Importance of the material of which the bod is composed ............. 94

Mixture for a good bod; Bod for small cupolas; Qualities of a good bod. 95

Tapping and stopping in; Mode of making the bod; How to make the tap 96

Mode of stopping in; Difficulties in stopping in; Devices to assist in stopping in ............ 97

The skill of the melter seen at the tap-hole; Uneven melting is the fault of the melter; Dumping .......... 98

Removal of the small props; Bridging over of small cupolas above the tuyeres and mode of removing the bridge ...... 99

Various methods of handlin_^ the dump; Removing the dump and various devices for this purpose 100

Breaking up the dump and picking it over; Different ways of recovering the iron from the dump; Chipping out 101

Theory of some melters to prevent iron from running into the tuyeres; Objection to this theory; Cupola picks ....... 102

Daubing; Materials used 103

Soaking fire clay; Amount of sand required for mixing with the clay; No advantage in using a poor cheap daubing 104

Putting on the daubing; Shaping the lining; Object of applying daubing to a lining; Mode of making new linings 105

Chipping off cinder and slag that adhere to the lining over the tuyeres; Not necessary or advisable to fill in the lining at the melting zone; Objections to sudden offsets or projections ...... 106

Thickness of the daubing; Sectional view of a cupola, illustrating effect of excessive daubing . . . . . . . . . .107

Shaping the lining of the boshed cupola; Special directions required for

X CONTENTS.

PAGE

shaping and keeping up the lining of the patent and odd-shaped cupolas ............. 109

Relining and repairing; Thickness of the lining; Location of the greatest-wear on the lining; Destruction of the lining at and below the tuyeres; Length of time a cupola lining will last; Burning away of the lining 110

Thickness of lining required to protect the casing; Repairing the lining at the melting zone . . . . . . . . . . .111

Repairing a lining with split brick; Mode of making a split brick . . 112

CHAPTER V. Experiments in Melting

Various opinions formerly held by foundrymen as to the point in a cupola at which the melting of iron actually took place; Different ways of charging or loading a cupola ........ 113

Experiments to learn definitely at what point iron is really melted in a cupola; Construction of an experimental cupola ..... 114

Results of the first experiment ......... 115

Arrangement of the bars of iron for the next experiment . . . 116

What was learned from this experiment; Arrangement of the bars and cupola for the next heat . . . . . . . . . .117

High pressure of blast may be almost wholly due to the size of the tuyeres; Arrangement of the bars for the next heat and the result of this experiment . . . . . . . . . . . .118

Arrangement of the cupola for the next heat and result of the experiment 119

Fuel used in the experiment; Reasons why iron is not melted in a cupola

by the blast and flame of the fuel; Melting zone in a cupola . . 120 Fire under the tuyeres .......... 121

Low tuyeres; Results of an experiment with low tuyeres. . . . 122

Melting zone; What determines the location of a melting zone in a

cupola; Lowering and raising the melting zone 123

Change in the location and depth of the melting zone .... 124 Experiments to learn the depth of the melting zone in practical melting. 125

Charges used in the experiments .126

Charges with which the most melting was done in these experiments; Necessity of passing the blast through a certain amount of heated fuel before a melting zone was formed in a cupola ..... 127 Cause of iron melted high in a cupola being made dull .... 128 Development of the melting zone above the tuyeres; Experiments with

a cupola with the tuyeres placed near the top; Failure of this plan . 129 Melting with coal; Softening hard iron; Experiments in softening iron by passing it in molten state through charcoal in its descent from the melting zone to the bottom of the cupola 130

CONTENTS. XI

PAGE

Time for charging; DiflFerence of opinion among foundrymen as to the proper time for charging; Experiments to ascertain the proper time for charging and putting on the blast after charging .... 132

Devices for raising the bottom doors ........ 133

Device for raising heavy doors 134

CHAPTER VI. Fluxing of Iron in Cupolas

Definition of a flux; Use of fluxes; Materials used as fluxes; Purpose of the use of limestone in the production of pig-iron .... 135

On what the making of a brittle cinder in a cupola by the use of limestone depends; Limestone in large quantities ..... 136

Variation in the quantity of limestone required to produce a fluid slag; Weight of slag drawn from a cupola ....... 137

Constituents of the slag; Efi'ect of flux upon iron ..... 138

The action of fluxes on lining ......... 139

How to slag a cupola; Cause of trouble in slagging; General method of charging the limestone; The slag hole ...... 140

Slag in the bottom of a cupola; Importance of the time for drawing the slag; Does it pay to slag a cupola? Estimate of the cost of slagging . 141

Shells; Use of oyster, clam and other shells; Cause of the crackling noise of shells when the heat first strikes them; Marble spalls . . . 142

Experiments with mineral and chemical materials with the view of making a cheap malleable iron; Reasons why iron is often ruined as a foundry iron by improper melting and fluxing; Increase in the per cent, of iron lost in melting by improper melting and fluxing . . 143

Effect of silicon on iron; Per cent, of silicon an iron may contain; Use at the present time of high silicon cheap southern iron . . . 144

Heavy breakage due to the use of high silicon irons; Effect of carbon upon cast iron ; Removal of free carbon from iron .... 145

Fluor spar, and its use as a flux ......... 146

Cleaning iron by boiling; Poling molten iron ...... 147

CHAPTER VII. Different Styles of Cupolas

Old Style Cupolas.

Old style cupola in general use throughout this country many years ago,

described and illustrated 149

Practice of casting with the use of the old-style cupola .... 151 The reservoir cupola, described and illustrated ..... 152 Stationary bottom cupola; Old style English cupola, described and illustrated 154

Expanding cupola, described and illustrated 155 xii CONTENTS.

PAGE

Ireland's cupola, described and illustrated 157

Ireland's center blast cupola, described and illustrated .... 159

Voisin's cupola, described and illustrated ....... 161

Woodward's steam-jet cupola, described and illustrated .... 163

Objection to this style of cupola; Tank or reservoir cupola, described

Production of Soft iron by putting a quantity of charcoal on the sand

bottom; Use of tanks in England 169

Mackenzie cupola, described and illustrated 170

Management of the Mackenzie cupola ....... 172

The Herbertz cupola, described and illustrated; Movable hearth of this

Advantages of the application of a steam jet to create draft in the

Test heats with the Herbertz cupola 176

Composition of the escaping gases from the Herbertz cupola . . . 177 Explanation why less carbon and silica are eliminated from the iron in

the Herbertz cupola than in the ordinary blown cupola . . . 178 Working of the Herbertz cupola at Elizabethport, N. J .... 179

The hearth in the cupola used at Elizabethport 180

Process of melting; Results of test-heats at Elizabethport . . . 181 Herbertz's cupola used for melting steel, described and illustrated;

Pevie cupola, described and illustrated 184

Object of Mr. Pevie in constructing a cupola; Stewart's cupola, described

Rapid melting of this cupola; The Greiner patent economical cupola,

described and illustrated .......... 188

What the novelty of this invention consists of 189

Principle of the workings of the Greiner cupola illustrated . . . 190 Mr. Greiner's conclusions. ......... 191

Points in favor of the Greiner cupola; Colliau patent hot-blast cupola,

described and illustrated 192

History and description of the cupola aud results obtained in melting . 193

Claims made for the Colliau furnace 194

The Whiting cupola, described and illustrated. 196

Jumbo cupola, described and illustrated 198

Charge table for the Jumbo cupola 200

The Crandall improved cupola with Johnson patent center blast tuyere,

described and illustrated. 202

Mode of applying the air to this cupola 203

Claims made for the Crandall cupola; Blakeney cupola, described and

illustrated 204

Advantages of this cupola 20?

CONTENTS. XI 11

CHAPTER VIII. Art in Mei<ting

PAGE

The art of melting iron in a cupola but little understood by many foundrymen and foundry foremen; Troubles experienced in melting. 206

No chance work in nature or in art; Necessity of understading the construction and mode of operation of a cupola to do good melting . . 207

Location and arrangement of the tuyeres; Preparation of the cupola for a heat; Lighting up 208

Melting iron in a cupola a simple process; Things to be learned and practiced; Necessity of a close study of all the materials used in melting 209

What should be the aim of every moulder; Advisability of the foreman of a foundry being the melter; Duties of the melter .... 210

Chapter IX. Scai.ks And Their Use

Necessity of an accurate scale upon the scaffold; Size of scale required; What the melting of iron in a cupola, when reduced to an art, consists in 211

Division of the fuel and iron into charges; The theory of melting not understood by many foundrymen; Incorrect methods of calculating the charges of iron and fuel . . 212

Use of old, worn-out scales condemned 213

CHAPTER X. The CUPOI.A Accounts

Value of cupola records; Manner of keeping the accounts . . . 214

Cupola report of Abendroth Bros., Port Chester, N. Y 215

Cupola report of Byram & Co., Iron Works, Detroit, Mich. . . . 216

Daily report of Foundry Department, Lebanon Stove Works . . . 217

Melting sheet of Syracuse Stove Works 218

Report of castings in Shop 219

Cupola slate for charging and cupola report 220

Blanks for reports and records and mode of making them out; Report

on a slate; Correctness essential to the value of a cupola account . 221

CHAPTER XL

Pig Mould for Over Iron.

Saving in iron and labor by the use of cast iron pig moulds for collecting over iron 222

XIV CONTENTS.

Chapter XII

What a Cupoi,a wii,i. Melt.

PAGE

Chief use of the cupola furnace; Employment of the cupola furnace for other purposes than melting iron 223

Quantity of iron that can be melted in a cupola; Number of hours a cupola may be run; Size and weight of a piece of cast-iron that can be melted in a cupola; Charging large pieces of iron at the foundry of Pratt & Whitney Co., Hartford, Conn.; Melting of cannon and other heavy government scrap at the Eobdell Car Wheel Co., Wilmington, Del 224

CHAPTER XIII. Melting Tin Plate Scrap in a Cupola

Various ways of preparing the scrap for charging; Attempts to recover the tin deposited upon the iron; Quality of the molten metal from the scrap 225

Susceptibility of the molten metal to the effect of moisture; Uses of the metal; Production of a gray metal from the scrap; Tests to learn the amount of metal lost in melting the scrap . ..... 226

Action of tin as a flux when melted with iron; Uusuitability of galvanized sheet-iron scrap for melting in a cupola; Doctoring the metal from tin-plate-scrap; Process of melting tin- plate-scrap . . . 227

Fluxing tin-plate-scrap; Construction of a cupola expressly for melting tin-plate-scrap ..... . . .... 228

Cost of melting tin-plate-scrap and profit in the business. . . . 229

CHAPTER XIV. Cost of Melting

Unreliability of melting accounts as generally kept; Objection to measuring fuel in baskets . . . . . . . . . . . 230

Results of an accurate account of the melting in a foundry in New Jersey; Cupola book; Proper method of figuring the cost of melting per ton 231

CHAPTER XV. Examples of Bad Melting

Necessity of giving causes of poor melting; Trouble with the cupolas at

the stove foundry of Perry & Co., Sing Sing, N. Y 233

Cause of the trouble; Sectional views of lining out of shape . . . 236

Remedy of the troubles 240

Bad melting at a West Troy Stove Works; Visit at the foundry of Daniel E. Paris & Co., West Troy, N. Y.; Inspection of the foundry with a view of locating the trouble . ........ 242

CONTENTS. XV

PAGE

Trouble due to the use of too much fuel 243

Experimeut of running the cupola with less fuel ; Objection of the

tnelter to the experiment ......... 244

Result of the experiment; Heats with a still further reduction of fuel . 246 Cause of bad melting in this foundry ....... 247

Warming up a cupola; Visit to the plant of the Providence Locomotive

Works; Trouble with the cupola .... .... 248

Cause of the poor melting due to the bed being burned too much . . 249 Remedy of the trouble; Bad melting, caused by wood and coal; Cause

of poor melting in one of the leading novelty foundries in Philadelphia 250 Poor melting in a Cincinnati cupola; Sectional elevation showing the

condition of the cupola 251

Uneven burning of the bed ; Reason for the necessity of dumping a

cupola at the foundry of Perry & Co. ....... 253

Chapter XVI. Mei.ters

Respect due to the practical and scientific tnelter; Unfortunate position of a poor melter; Interference with a good melter frequently the cause of poor melting 254

Necessity of furnishing proper tools for chipping out, and making up the cupola; What should be the aim of every melter .... 255

Interest of every foundryman to keep his melter posted .... 256

CHAPTER XVII. Expi<osioN OF Molten Iron

Conditions under which molten iron is explosive; Explosions caused by a wet spout or a wet bod 257

Cause of sparks; Various causes of the explosion of molten iron; Explosion due to thrusting a piece of cold, wet or rusted iron into molten iron 258

Explosion of molten iron when poured into a damp or rusted chill-mould or a wet sand-mould; Accident in the foundry of Wm. McGilvery & Co., Sharon, Pa 259

Explosion of molten iron when poured into mud or brought into contact with wet rusted scrap; Accident in the foundry of James Marsh, Lewisburg, Pa.; Accident at the foundry of North Bros., Philadelphia, Pa. 260

Explosion at the foundry of the Skinner Engine Co., Erie, Pa., and at the foundry of the Buffalo School Furniture Co., Buffalo, N. Y. . . 261

Prevention of explosions 262

XVI CONTENTS.

CHAPTER XVIII. Spark-Catching Devices for Cupolas

PAGE

Spark-catcher in old-style cupolas 263

Spark-catching device for modern cupolas 264

Return flue cupola spark-catcher, designed by John O. Keefe. . . 266

Other spark-catching devices 268

The best spark-catching device; Cause of sparks being thrown from a cupola; Prevention of sparks being carried out of the stack; Enlarged stack 269

CHAPTER XIX. Hot Blast Cupolas

Hot blast cupolas constructed by Jagger, Treadwell & Perry . . . 271 Cupola at the foundry of Ransom & Co., Albany, N. Y.; Arrangement

with exhaust pipes ........... 273

Heating the blast for a cupola; Waste heat from a cupola; Plans for

utilizing the heat escaping from a cupola ...... 274

Cupolas at the Carnegie Steel Works, Homestead, Pa.; Prevention of

the escape of heat in low cupolas 275

Chapter XX

Taking off the Blast During a Heat — Banking a Cupola— Blast Pipes, Blast Gates.

Explosions in blast pipes, blast gauges, blast in melting; Length of time the blast can be taken off a cupola; Management of a cupola from which the blast is taken off ........ . 276

Banking a cupola; Communication from Mr. Knoeppel, Foundry Superintendent, Bufi'alo Forge Co., Buffalo, N. Y., on banking a cupola . 277

Blast pipes; Importance of the construction and arrangement of blast pipes; Underground blast pipes ........ 279

Objection to underground blast-pipes; Materials used in the construction of blast-pipes; Galvanized iron pipes 280

Table prepared by the Buff"alo Forge Co , Buffalo, N. Y., as a guide for increasing the diameter of pipes in proportion to the length; Diameter of blast-pipes; Friction in pipes ........ 281

Frequent cause of a blower being condemned as being insufficient. . 282

Table showing the necessary increase in diameter for the diff"erent lengths 283

Connection of blast pipes with cupola ; Combined area of the branch pipes 284

Table of diameter and area of pipes 285

Connecting blast pipes direct with tuyeres ; Perfect connection of air chambers; Poor arrangement of pipes in a "perfect cupola" . . 286

CONTENTS. xvii

PAGE

Mode of connecting a belt-air chamber with the tuyeres; Best way of connecting blast pipes with cupola tuyeres . . . . . . 288

Blower placed near cupola .......... 289

Poor melting often caused by long blast pipes; Perfect manner of connecting the main pipe with an air chamber; Blast gates; Advantage of the employment of the blast gate ........ 290

Explosions in blast pipes; Prevention of such explosions; Blast gauges; Variety of gauges 292

What an air-gauge to be of any value in melting must indicate . . 293

Blast in melting; Means for supplying the required amount of air to the cupola; Machines for supplying the blast; Relative merits of a positive and non-positive blast ......... 294

Amount of air required for combustion of the fuel in melting a ton of iron 295

Theory of melting in the old cupolas with small tuyeres; Necessity of discarding the small tuyeres ......... 296

Points to be remembered in placing tuyeres in a cupola; Best tuyere for large cupolas; Size of the largest cupolas in which air can be forced to the center from side tuyeres ......... 297

Cupolas of the Carnegie Steel Works, Homestead, Pa. ; Experiments with a center blast tuyere 298