554
§3 SCIENTIFIC LIBRARY
1 UNITED STATES PATENT OFFICE
GPO 16—53001-1
Cassier's Magazine
Engineering Illustrated
Volume XV November, 1898-April, 1899
The Cassier Magazine Company
3 West 29th St., New York
33, Bedford Street, Strand, London
w P 1
C f
Copyright, 1899.
Press of Louis
Cassier & Company.
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kPR 3 1399 Ve*|T 0^
INDEX TO VOLUME XV.
Acetylene, The Generation of, . American Lake Shipping and Casualties, Illustrated.
America's Export Trade, Ancient Mining, .... Illustrated.
Aristotle and Modern Engineering,
C. A. S. Howlett, . George E. Walsh, .
Theo. C. Search, Dr. John A. Church, M. Am. Inst., M. E., Dr. Robert H. Thurston,
E. H. Mullin,
Barrowman, James : The Health Conditions of Coal Mining
Illustrated.
Battleship Design, The Problem of,
Illustrated .
Bayles, James C : Henry Robinson Towne, ..... Benjamin, Professor C. H.: The Evolution of the Machine Tool, . Illustrated.
Bennett, P. A. E., U. S N., F. M.: Engine-Room Experience in War Time, Biggart, A. S.: Sir William Arrol, ......
Illustrated.
Bird, George Frederick : British Four-Cylinder Locomotives,
Illustrated.
Birkinbine, M. Am. Inst., M. E., John : Mine Timbering in the United States Illustrated.
The Franklin Institute, ......
Illustrated.
Blast Furnace Explosion, A, . .
Illustrated.
Block-Setting Titan Cranes, ....
Boiler and Engine Selection, Points in, Boilers, Mechanical Draught for Steam Illustrated.
Bramhall, Frank J. : Luxury in American Railway Travel,
Illustrated.
Biographical Sketches :
Arrol, Sir William, .....
Illustrated.
Aspinall, J. A. F., . .
Beresford, Lord Charles, ....
Head, Jeremiah, ......
Towne, Henry Robinson, ....
Cable Railway, The Vesuvius, ....
Illustrated. Cannon, A Double-Barrel, ....
Chimney, A Factory Without a, .
China, Business Methods in, .
Chinese Middlemen, ......
Chuck for Shop Use, A Magnetic,
Joseph Horner, William O. Webber, Walter B. Snow,
A. S. Biggart,
James C. Bayles, A. Faerber,
PAGE
369 499
508
389 195 270
359
153 124
217 3
142 20
315
426
427
421
48
9i
153 323 512 153 155
514 85 167 167 242
iv INDEX
PAGE
Church, Dr. John A., M. Am. Inst., M. E.: Ancient Mining, . . 389
Illustrated.
Clark, Eugene B. : Electric Power in Steel Making, ..... 441
Illustrated.
Coal Mining, The Health Conditions of, . . . James Barrowman, , 270
Illustrated.
Coal Washing, . . . . . . H. L. Siordet, Associate
illustrated. of the Royal College of
Science, . . 60
Collins, Capt. John W., Engineer-in-Chief of the Service :
The United States Revenue Cutter Service, ..... 373
Illustrated. Compressed Air on Warships, .... Passed Assistant Engineer
illustrated T. W. Kinkaid, U.S.N., 67
Copper Paint, Galvanic Action on Iron and Steel Ships from, ... 87
Cranes, Block-Setting Titan, .... Joseph Horner, . . 171
Illustrated.
Distilling Ship " Iris," For the United States Fleet, The, . Passed Assistant Engineer
illustrated. W. W. White, U. S. N., 75
Double-Barrel Cannon, A, ........ 574
Draught for Steam Boilers, Mechanical, . . Walter B. Snow, . 48
Illustrated.
Dubsky, Alfred O.: The Rome-Tivoli Electric Installation, . . . .331
Illustrated.
Duckham, Fred E.: Pneumatic Grain Elevators and Conveyors, ... 31
Illustrated.
Durfee, W. F. : Early Use of Rolls in Manufacture of Metals, . . . . 478
Illustrated.
How the Pyramids Were Erected, ...... 213
Illustrated.
Elevators and Conveyors, Pneumatic Grain, . . Fred E. Duckham, . 31
Illustrated.
Engine Construction and Steam Navigation in the United
States, Early Marine, .... Charles H. Haswell,
Illustrated. C. and M. E., . 160
Engineering, Aristotle and Modern, . . . Dr. Robert H. Thurston, 195
Engineering in Africa and the Far East, . . J. M. Nisbet, . . 431
Illustrated.
Engine-Room Experience in War Time, . . F. M. Bennett,
P. A. E., U. S. N„ 217
Excavation Without Using Explosives, Subaqueous Rock, Fred Lobnitz, . 204
Illustrated.
Explosives in Naval Warfare, High, . . . Professor Charles E.
illustrated. Munroe, . .115
Electricity :
Electric Light, The Nernst, ....... 514
Electric Lighting of Railway Trains from Car Axles, . . . .88
Electric Motor for Small Industrial Purposes, The, Alfred N. Gibbings,
M. Int. E. E., . 237
Electric Motor, A Portable, . . . . . . . .165
Illustrated.
Electric Motors for Hire, ........ 165
Electric Power in Mining, , John McGhie, , 37
Illustrated.
Eugene B. Clark,
L. D. W. Magie, A. O. Dubsky, .
George Frederick Bird, John Birkinbine,
INDEX
Electricity : —
Electric Power in Steel-Making,
Illustrated.
Electric Railway Statistics, American, Electric Street Railways, Growth of Open-Conduit, Electric Utilisation of Water Powers, Rome-Tivoli Electric Installation, The, Illustrated.
Short Circuits on the Niagara Falls-Buffalo Transmission Lines, Faerber, A. : The Vesuvius Cable Railway,
Illustrated.
Fires, Possible Dangers of Steam Jets for Extinguishing, Fire Extinguisher, Liquid Carbonic Acid Gas as a, Forsyth, William : American Locomotive Repair Shops, .
Illustrated.
Four-Cylinder Locomotives, British,
Illustrated.
Franklin Institute, The, ....
Illustrated. Gas Engines for a Pumping Station, Large, . . .
Gibbings, M. Inst. E. E., Alfred H.: The Electric Motor for Small Industrial
Purposes, ..........
Gimbal Ring Movement, An Early Example of the, .
Illustrated.
Haswell, C. and M. E., Charles H.: Early Marine Engine Construction and Steam Navigation in the United States, Illustrated.
Heating and Ventilating Data, Some, .
Heating Dwellings in Korea,
Heating Large Department Stores,
Herschel, Clemens : The Venturi Water Meter, .
Hitchcock, Thomas : Industrial Imperialism, .
Horner, Joseph : Block-Setting Titan Cranes,
Illustrated.
Horseless Carriages Four Hundred Years Ago,
Illustrated.
Howlett, C. A. S. : The Generation of Acetylene, . Industrial Imperialism, . . , . .
" Ins," for the United States Fleet, The Distilling Ship,
R. Sennett, M.I.C.E
Illustrated.
Thomas Hitchcock, Passed Assistant En- gineer W.W.White,
U. S. N., .
Sidney Tebbutt,
Iron, The End of Wrought, . . . . . . . .
Keely Motor Power, .........
Kinkaid, U. S. N., Passed Assistant Engineer T. W.: Compressed Air on Warships,
Illustrated.
Lamp Holder, A Magnetic Electric, .....
Laundry Machinery, Illustrated.
Leaks in Ammonia Coils of Refrigerating Plants, Detecting, Lifting of Heavy Bodies by the Ancients, The Transporta- tion and, ......
Illustrated.
Lighting of Railway Trains from Car Axles, Electric,
Lobnitz, Fred : Subaqueous Rock Excavation Without Using Explosives,
Illustrated.
Page 441
241
86
321
33i
515 155
84
84
225
142
315
427
237 425
160
166 328
425 411
455 171
458
369
455
75 242
425 67
242 291
J. Elfreth Watkins, C.E., 108
88 204
vi
INDEX
Locomotive, An Early, .....
Illustrated
Locomotive Repair Shops, American,
Illustrated.
Locomotives, British Four-Cylinder,
Illustrated.
Luxury in American Railway Travel,
Illustrated.
Machine Tool, The Evolution of the, Illustrated.
Machine Tools, Handiness of American, Magie, T.. D. W.: Electric Utilisation of Water Powers, Magnetic Chuck for Shop Use, A, Magnetic Electric Lamp Holder, A,
Marine Engine Construction and Steam Navigation in the United States, Early, .... Illustrated.
Marine Engineering, The Outlook in, .
Illustrated.
Marine Engineering, The Outlook in,
W. D. Wansbrough, William Forsyth, George Frederick Bird, Frank J. Bramhall, Prof. C. H. Benjamin,
Charles H. Haswell,
C. and M. E., Commodore George W.
Melville, U. S. N., Commodore George W.
Melville, U. S. N.,
McGhie, John, Electric Power in Mining, ......
Illustrated.
Mechanical Draught for Steam Boilers, . . . Walter B. Snow,
Illustrated.
Melville, U. S. N , Commodore George W. : The Outlook in Marine Engineering, Illustrated.
Mine Timbering in the United States, . . . John Birkinbine,
Illustrated. M. Am. Inst. M. E.,
Mining, Electric Power in, ... . John McGhie,
Illustrated.
Motor, A Portable Electric, .......
Illustrated.
Motors for Hire, Electric, ........
Mueller, Otto H.: Modern Pumping Machinery Tor Mine Service,
Illustrated.
Mullin, E. H. : The Problem of Battleship Design, ....
Illustrated.
Munroe, Professor Charles E. : High Explosives in Naval Warfare,
Illustrated.
Navigation in the United States, Early Marine Engine Con- struction and Steam, .... Illustrated.
Nernst Electric Light, The, ....
Nisbet, J. M.: Engineering in Africa and the Far East, .
Illustrated.
Oil Fires Under Steam Boilers, Oiling Stations for Steamships, . Ore-Crushing Rolls, Sectional, Illustrated.
Painting Structural Iron and Steel,
Pelatan-Clerici Process for Gold and Silver Extraction, The, Pneumatic Shop Appliances, .... Illustrated.
Charles H. Haswell, C. and M. E.,
E. Gybbon Spilsbury, Whitfield Price Pressinger,
PAGE
188 225
142
9i 124
85 321 242 242
160
251
401 37
48 251
20
37
165
165
487
359 115
160
5i4 43i
5i5 515 243
86 282
259
INDEX
vn
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. Fred E. Duckham, . |
PAGE 31 |
|
inces, |
. 259 |
|
88 |
|
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Otto H. Mueller |
• 487 |
|
W. F. Durfee, C. E., |
213 |
|
2 |
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|
335 |
|
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. |
• 250 |
|
170 |
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■ 33i |
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43o |
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• 333 |
|
|
345 |
|
|
. |
. 90 |
|
359 |
|
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A. Faerber, |
155 |
|
.... |
86 |
|
424 |
|
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. 241 |
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Frank J. Bramhall, |
9i |
Pneumatic Grain Elevators and Conveyors, Illustrated.
Pressinger, Whitfield Price : Pneumatic Shop Appliances, Illustrated.
Propeller Shaft, Unusual Location for a Steamship, Pumping Machinery for Mine Service, Modern, Illustrated.
Pyramids Were Erected, How the, Illustrated
Portraits :
Arrol, Sir William, ....
Blathy, O. T„
Cramp, Charles H.,
Dickie, George W.,
Dubsky, A. O.,
Head, Jeremiah, ....
Mengarini, G., .
Pouchain, Charles, . . . .
Towne, Henry R., ....
White, Sir Wm. H., Railway, The Vesuvius Cable,
Illustrated.
Railways, Growth of Open-Conduit Electric Street, Railways in Africa, New, Railway Statistics, American Electric, Railway Travel, Luxury in American, Illustrated.
Raising the Stones of the Pyramids, A Possible Method of,
Illustrated.
Repair Shops, American Locomotive, Illustrated.
Responsibility, ......
Richards, John : George W. Dickie, ......
Rock Excavation Without Using Explosives, Subaqueous, Fred Lobnitz Illustrated.
Rolls in the Manufacture of Metals, Early Use of, . W. F. Durfee, C. E.,
Illustrated.
Rome-Tivoli Electric Installation, The, . . . Alfred O. Dubsky, .
Illustrated.
Search, Theo. C: America's Export Trade, ..... Sennett, A. R., M. I. C. E.: Horseless Carriages Four Hundred Years Ago,
Illustrated.
Short Circuits on the Niagara Falls-Buffalo Electric Power Transmission Lines, Siordet, H. L., Associate of the Royal College of Science: Coal Washing, .
Illustrated.
Smoke Suppression, Fallacies Concerning, .....
Snow, Walter B.: Mechanical Draught for Steam Boilers, . . . .
Illustrated.
Spilsbury, E. Gybbon: The Pelatan-Clerici Process for Gold and Silver Extraction, Steam Jets for Extinguishing Fires, Possible Dangers of, . Steam Laundry Machinery, .... Sidney Tebbutt
Illustrated.
Steamships, Oiling Stations for, .......
Steamships, The Ventilation of, . . . . Stephen H. Terry
Illustrated.
William Forsyth, W. D. Wansbrough,
326
225
137 245 204
478
33i
508 458
515 60
244 48
282
84 291
515
286
viii INDEX
Page Steel Making, Electric Power in, . . Eugene B. Clark . 441
Illustrated. Stokers, Aboard Ship, Mechanical, ... . . . 244
Svenson, John: The Valve Gear of the Willans Engine, . . . 209
Illustrated.
Tebbutt Sidney: Steam Laundry Machinery, . . . . .291
Illustrated.
Terry Stephen H.: The Ventilation of Steamships, . . . 286
Illustrated.
Thurston, Dr. Robert H. : Aristotle and Modern Engineering .... 195 Transportation and Lifting of Heavy Bodies by the
Ancients, The, ..... J. Elfreth Watkins, C E. 108
Illustrated.
Twelvetrees, W. N. : Water Softening, ...... 465
Illustrated.
Typewriter Industry in the United States, The, ...... 241
United States Revenue Cutter Service, The, . . Capt. John W. Collins,
illustrated. Engineer-in-Chief of the
Service 373 Valve Gear of the Willans Engine, The . . . John Svenson . 209
Illustrated.
Ventilating Data, Some Heating and, . . . . . . .166
Ventilation of Steamships, The, . . . Stephen H. Terry, 286
Illustrated.
Venturi Water Meter, The, .... Clemens Herschel, . 411
Illustrated.
Vesuvius Cable Railway, The, ... A. Faerber, . 155
Illustrated.
Walsh, George E.: American Lake Shipping and Casualties, .... 499
Illustrated.
Wansbrough, W. D.: An Early Locomotive, ..... 188
Illustrated.
Wansbrough, W. D. : Responsibility, ....... 137
Warships, Compressed Air on, .... Passed Assistant Engineer
Illustrated. T. W. Kinkaid, U. S. N., 67
Water Powers, Electric Utilisation of, . . . L. D. W. Magie, . 321
Water-Raising Machine, An Old-Time, ....... 324
Illustrated.
Water Softening, . . . . . . W. N. Twelvetrees, 465
Illustrated. Watkins, C. E., J. Elfreth : The Transportation and Lifting of Heavy Bodies by the
Ancients, ......... 108
Illustrated.
Webber, William O.: Points in Boiler and Engine Selection. . . . 421
White, U. S. N., Passed Assistant Engineer W. W.: The Distilling Ship " Iris," for
the United States Fleet, .......... 75
Illustrated.
Willans Engine, The Valve Gear of the, . John Svenson . 209
Illustrated.
PHOTO BY JOHN FERGUS, CANNES, FRANCE.
■yZZjk^Ojvu/
Cassier's Magazine.
Vol. XV.
NOVEMBER, 1898
No. 1
SIR WILLIAM ARROL.
A Biographical Sketch of the Great Bridge Builder,
By A, S. Biggart
T
HE man en- dowed with sufficient ca- pacity and energy to develop his own naturalabilities lives in the influence he wields over others, and endures in the work he leaves be- hind him. For such a man difficulties form the training- school in which his powers are devel- oped, and in overcoming them he is inspired with zeal for further achievements. When energy and capacity are combined with a well-balanced mind, and with the bearing that attracts the confidence of his fellow men, he creates enthusiasm in others and inspires them as willing agents in carrying out his undertakings. A man' s life is made up of character and conduct, but is moulded by experience, and it is upon the school training of experience that future success or failure mainly depends.
To know Sir William Arrol, and his life and work, is to know such a man, - -one who has risen from humble be- ginnings to the highest position in his
1— 1 Copyright,
profession through sheer ability, and persistent effort. Born in the village of Houston, Renfrewshire, in 1839, he is now in his fifty-ninth year. When he was quite a child his family removed to Johnstone, then, as now, one of the engineering centres of Scotland, where his grandfather was the first to intro- duce gas. His father, starting as a spinner, raised himself to the position of manager of the great thread works of Messrs. J. & P. Coats, of Paisley.
William Arrol had little schooling, for, at the early age of nine years, he began work as a piecer in a Johnstone cotton- mill. Two years later he entered the bobbin-turning works of Messrs. J. & P. Coats, and at the age of fourteen was apprenticed to a Mr. Reid, a black- smith and general engineer in Paisley. His apprenticeship over, young Arrol found employment in various districts in England and Scotland, before becom- ing a foreman in the boiler and bridge yard of Messrs. R. Laidlaw & Sons, of Glasgow. He was then twenty-four years of age, and five years later he be- gan business on his own account within a few hundred yards of the present Dalmarnock Iron Works, in the East End of Glasgow.
He began, of course, in a small way, making boilers, girders, and general
All rights reserved. 3
CASSIER'S MAGAZINE,
SIR WILLIAM ARROL.
structural work, and with all the diffi- culties attending the formation of an entirely new business with small means. Soon, however, the business began to grow, and then grew so rapidly that, in 1 87 1, he was compelled to remove to roomier premises. Then was founded the business which is now carried on by Sir William Arrol & Co. , Limited, at the Dalmarnock Iron Works, in the east- ern outskirts of Glasgow. In these new and more extensive works Mr. Arrol was enabled to undertake larger contracts than previously in all kinds of structural work, railway bridges, etc. Here also boiler-making for a time was carried on to a considerable extent, but afterwards was set aside in favour of the particular class of work with which the name of Arrol is now associated. With the in- creasing size and importance of con- tracts, and consequently greater masses ot material requiring to be handled, Mr. Arrol set about designing and making special drilling and riveting plant for the manipulation of material by the most improved and economical methods.
One of the most important contracts at th's time was that with the Caledon- ian Railway Company for a bridge over the Clyde at Bothwell. This structure is a very high one, and Mr. Arrol adopted the novel method of building the bridge on land and rolling it out, span by span, and from pier to pier in front. Another contract was for the ironwork comprising the structural por- tion of the great Central Station at Carlisle. A larger one still was a con- tract for the Caledonian Railway Bridge over the Clyde, to carry this railway to the new Central Station. It was to be a large structure, in width sufficient to carry four pairs of rails, and high enough to allow the smaller class of vessels frequenting this portion of the Clyde to pass underneath. It was in connection with the drilling of the booms for the main girders of this bridge that he introduced the system of building these booms complete, pass- ing a traveling drilling machine over them, with the drills in such positions as to make them capable of boring every hole in the entire boom. The depth ot
drilling in some instances was as much as seven inches of solid material. Not only was special drilling plant made to carry out this contract, but Mr. Arrol, perceiving the great advantage that would be obtained by a system of eco- nomical riveting (as the rivets were so large and so long that it was practically impossible to have satisfactory work performed by hand), set about designing plant for the purpose, and the outcome was the introduction of the hydraulic riveting machine, known under the title of Arrol's Patent, which has done so much to revolutionise riveting in the principal bridge-building and ship-build- ing yards of Great Britain.
Important as were these operations, however, they were small compared with the next undertaking to which Mr. Arrol addressed himself, and which was destined to make his reputation and to bring him honour and fame. This was the construction of the great Forth Bridge. When Mr. Arrol first became associated with this great work, the design in hand was that of the late Sir Thomas Bouch, who was the engineer of the first Tay Bridge. Sir Thomas Bouch's plan for spanning the Forth was to throw a suspension bridge over the estuary on the same site as that on which the present bridge stands. This design provided for piers in practically the same positions as the present piers, with this difference, however, that the height of the suspension bridge erec- tions would have been over 600 feet above high- water level. Sir Thomas Bouch's design would have produced a more graceful structure than the present one, but it would not have given the rigidity that is essential where heavy trains are continually passing over at high rates of speed. In the present structure the provision made for resist- ing wind pressure is much greater than in the original plan. It was, however, on the Bouch design that Mr. Arrol secured the contract for the bridge. He had already spent a large amount of money in preliminary operations, and in the erection of workshops, when suddenly the catastrophe of the fall of the Tay Bridge compelled a pause, and
CASSEER'S MAGAZINE.
ultimately the abandonment of the scheme of Sir Thomas Bouch.
After the fall of the Tay Bridge, Mr. Arrol spent some time in examining the old structure and in preparing plans and submitting proposals for rebuilding it. His idea was to surround the old cast iron columns with others of steel, and to connect these new columns securely together by sufficient bracing; but it was found on further examination that the foundations of the old bridge were not so secure as was essential in a structure of this kind. It was, there- fore, ultimately decided to discard the
SIR WILLIAM ARROL, AGED 25. FROM A PHOTO BY J. & G. TURNER, GLASGOW.
whole of the old structure and to build an entirely new bridge a short distance further up the river. The new scheme was passed through Parliament, under the guidance and direction of Mr. W. H. Barlow as engineer.
While this was in progress Mr. Arrol was constructing a viaduct over the South-Esk at Montrose, and with a view to gaining experience he adopted the novel method of sinking the cylin- ders from a pontoon carried by four legs resting on the bottom. The pon-
toon and legs were so arranged that the pontoon could be lowered, the legs drawn up off the bottom, and the whole floated to a new position, where it was the work of a very short time to drop the legs on the bottom again and raise the pontoon sufficiently clear of the water to allow sinking operations to again commence on the site of any new pier.
When Mr. Arrol's tender for the new Tay viaduct was accepted, he imme- diately made arrangements for starting the work. His experience with the pontoon at Montrose was such as to de- cide him to adopt pontoons for the sink- ing of the cylinders of the new struc- ture. These pontoons were very much larger than that used at Montrose, and contained all the plant necessary for the operations performed at each pier. Thus, the cylinders were built and low- ered into position by a hydraulic ap- paratus from the deck of the pontoon. After the cylinders had been placed in position, the diggers were set to work, these being worked by steam cranes, also resting on the pontoon itself, and when the sinking operations were completed, concrete mixers, hav- ing for a platform a part of the pontoon, were employed, and the concrete was filled into the cylinders as required. These various operations being finished, the pontoon was lowered and floated to another pier. The general arrange- ment of the whole is seen in the illus- tration on page t6.
Several pontoons were adopted in the building of the new Tay Bridge, and in this work a considerable advan- tage was gained from the wreckage of the old structure being near at hand, as many of the operations in connection with the new structure were conducted from the old, although the main girders were the only portions of the old bridge actually wrought into the new. These girders were transferred from the old bridge by cranes in the case of the smaller girders, and in the case of the larger girders they were lifted by pon- toons bodily off the old bridge and floated and lowered into their final posi- tion. A roadway was thus made on
SIR WILLIAM ARROL,
i ill i* ii
.LIAM ARROL & CO., LTD.
SEAFIELD, NEAR AYR,
SIR WILLIAM ARROL'S COUNTRY RESIDENCE.
which the additional new main girders required were run out and lowered.
These arrangements applied only so far as portions of the old structure were used in the new one. In the centre gap of the old bridge from which the main girders fell, and were consequently destroyed, another arrangement had to be adopted. This consisted in floating the girders out from land, and placing them on the new piers at a low level from which they were afterwards raised, span by span, by hydraulic power to their proper position. Temporary col- umns were used for carrying the weight while they were being raised, and the system adopted was to raise them by hydraulic jacks, resting on girders secured by pins to the columns, step by step, as if one were rising on a ladder. As these girders were raised into posi- tion, the iron piers on which they were supported were built underneath, so that when the girders were ultimately at their final level, the weight was trans- ferred from the temporary columns to the main piers. This bridge was begun
early in 1882 and completed in June, 1887, and after being most carefully and thoroughly tebted by the British Board of Trade, was opened for traffic imme- diately thereafter.
Not long after the Tay Bridge was begun, Mr. Arrol secured the contract for the Forth Bridge. In this great work the design adopted was that tech- nically known as the cantilever-and- central-span. The cantilevers are sup- ported from main steel piers founded on each bank of the river, with a third, resting on the island of Inchgarvie, equidistant from those on the banks. The cantilever and central girder span is not claimed by the designer, Sir Ben- jamin Baker, as new in principle, though it is well within the facts of the case to state that no structure approaching the importance of the Forth bridge had been previously constructed on this principle.
The novelty consisted both in the vastness of the structure itself, and in the design of the many and various por- tions of which it is composed. More-
CASSIER'S MAGAZINE.
SIR WILLIAM ARROL.
over, it was also the first great structure built entirely of mild steel. The two main spans are each 1700 feet clear, and have a headway in the centre 500 feet in length, with not less than 150 feet clear height above high-water mark. These immense spans support excep- tional loads to the main piers, and as some of these piers are founded at a depth of almost 90 feet below high water, the making of the foundations alone was a work of exceptional magni- tude.
In past engineering practice it has
proached by viaducts of granite piers and steel girders of an ordinary type, the principal point of interest in connec- tion with them being the great height of the roadway above the water, or ground, level.
Throughout the building of the Forth Bridge Mr. Arrol was the active spirit, and everything was on a gigantic scale. The workshops that had been built for Sir Thomas Bouch's bridge were util- ised, and, in addition to these, other large shops were built near the site of the works, for the manipulation of the
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photo by sir William arrol & co., ltd.
THE MATERIAL LOCK USED IN SINKING CYLINDERS WITH COMPRESSED AIR.
been the habit ot engineers to avoid struts of large dimensions, but in this structure a large proportion of the main members are struts of exceptional size and length. They are, in most cases, of tubular form, rigidly stiffened at close intervals, and so satisfactorily was the design worked out that the Board oi Trade sanctioned a stress of 7^ tons to the square inch on these members. The main spans of the bridge are ap-
60,000 tons of steel required in the structure. The bridge itself was of such a novel type that special plant had to be designed for carrying out the work, and it is in this connection that the impress of Mr. Arrol's personality is seen in practically every stage of the great undertaking.
In the shops hydraulic power was used to a very great extent, not only for the handling of the material, but
IO
CASSIER'S MAGAZINE,
1ED BY PERMISSION OF SIR BENJAMIN BAKER, K, C. M. G.
TRAVELING CRANE AND TUBE-DRILLING~MACHINE USED AT THE FORTH BRIDGE.
also, by means of stamping presses, for manipulating it into forms which had not previously been thought possible. All the rivet-holes in the steelwork of the bridge were drilled, and conse- quently the drilling plant was a very important part of the whole. Mr. Arrol's system of first assembling the parts together and then drilling through the various thicknesses, while placed in the same position as they would occupy when ultimately fixed in the structure itself, was carried out to a very large extent, with the result that the rivet- holes were found, practically speaking, mathematically correct. The traveling drilling machines, which passed over the various parts of the work, were used not only for drilling the main portions of the girders, but also for the many miles of steel tubes required in the structure.
Some idea of the extent of the plant employed may be gained from the fact that it took over a year to have it de- signed and made ready to begin opera- tions, but even long afterwards large additions were continually being made and applied. It may be of interest to add that the cost of the temporary plant was about ,£500,000. This in- cluded several small steamships, 1,000,- 000 cubic feet of timber, 1200 tons of service bolts, 60 miles of wire ropes,
jacks and rams almost innumerable, and other manifold kinds of machinery and plant in proportion.
During the time the workshops were being got into condition the material for the caissons for the foundations was be- ing prepared - by outside contractors. They were then put together on the shores of the Forth. These caissons were all 70 feet in diameter, and after being built and launched sideways, after the fashion ot launching a ship, were carried into the waters of the Forth and thereafter floated to the position where they were to be finally sunk into the bed of the river. The sinking of these caissons was one of the novel and most interesting operations in connection with the great structure. After the caissons had been floated over the site they were to occupy, concrete was grad- ually filled in till there was not only sufficient to sink them to the bed of the river, but also enough to force them into the ground as the material was be- ing excavated in the caisson itself. The caisson proper may be looked upon as a huge diving bell into which the men descended through air locks and shafts, and as the work of removing the mate- rial from the inside proceeds, the caisson lowers itself into the bed of the river. This process was continued till the cais- son arrived at its final depth, after which
SIR WILLIAM ARROL.
ii
the concrete and masonry were carried up to their present height.
One of the most ingenious devices called into being by the necessities of the occasion was the hydraulic spade which Mr. Arrol invented for use in the caissons. This consists of a wrought iron cylinder with a brass casting screwed on to one end, through a stuff-
ing face of, say, 15 inches, one man will stand on each side of the spade to lift it by a cross handle and place the point of the spade in the ground, while the third man, stationed behind, opens the cock and allows the water to enter the top, causing an upward movement of the cylinder, which, being arrested, forces the spade into the ground until
PUBLISHED BY PERMISSION OF SIR BEN, AM. N BAKER, K. C. M. G.
GENERAL VIEW OF THE DRILL ROADS AT THE FORTH BRIDGE.
ing box in which the shaft of the spade passes. On the other end is fixed a cap into which are screwed short wrought iron pipes to vary the lengths of the spade as required. The spade is forged on one end of the shaft, on the other end of which is a piston with the necessary cup leather. A screw in the lower casting communicates with both ends of the cylinder, and high-pressure water is led to it through a small flexi- ble hose, while another hose is employed to carry off the exhaust water.
Each spade is worked by three men, and the action of it is very similar to the ordinary spade. Thus, with a work-
the piston reaches the end of its stroke. Then, upon reversing the cock, the cylinder falls and sets free the upper end, ready to repeat the operation. By means of this ingenious machine ma- terial that had before been taken away only piecemeal by hand in the air cham bers was now excavated in large lumps. As the locks for removing the ma- terial were of a novel form, an illustra- tion of them is given on page 9. While the main piers in the river were in progress the granite piers for the ap- proaches to the main structure were being built. After these had attained to a level of about 10 feet above high
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CASSIER'S MAGAZINE.
SIR WILLIAM ARROL.
13
water, the steel viaducts were built upon them, and were raised by hydraulic power, stage by stage, until they reached their final height of 150 feet above high- water level. As the viaducts were thus raised in stages, the granite piers were built underneath, this operation being so successful that not a hitch occurred during the carrying out of this work. The weight raised in this operation in the case of the longer viaduct was well- nigh 2000 tons of steelwork.
After the main piers had been com- pleted the erection of the superstructure began at three points, namely, North Queensferry, Inchgarvie and South Queensferry. The first portion of the steelwork was one of the most compli- cated parts in the whole, and is techni- cally known as the skewback. The skewbacks rest immediately over the piers on steel bedplates, and some idea may be formed of their intricacy when it is known that in these skewbacks con- verge five different tubes and five differ- ent sets of wind-bracing in the form of large girders.
The skewback proper, with its con- nection to these tubes and girders, al- though neither very long nor very high, weighs somewhere about 500 tons. While in one sense they are compli- cated, in another sense they are not, because the design is such that in every hole the rivet intended for it could be put, although in some cases special means had to be taken to effect this. A considerable portion of the riveting in these skewbacks was carried out by small riveting machines, capable of be- ing easily lifted by one hand, but strong enough to withstand a water pressure of from two to three tons per square inch. The smallness of the machine was necessary to allow it to go into the small spaces in the skewback, and it says a great deal for the design, as well as for the system adopted, that every rivet hole was accurately filled by a good rivet as originally intended.
After the skewbacks and the steel- work immediately over the main steel piers had been completed up to a height of about 50 feet, temporary platforms were erected, stretching from column
to column in connection with hydraulic lifting arrangements within each of the four vertical steel columns. These plat- forms were raised in stages from the vertical columns which supported them until they reached the final height of 350 feet above high-water level. As the platform was raised the column was built up, and after the platform reached its final height the upper portions of the structure were built upon the platform itself, until they were completed suffi- ciently far to enable them to sustain their own weight. While the platform was being raised, these main columns were rivetted by special riveting ma chines attached underneath.
The riveting machines were of a double character, having a cylinder in- side the column as well as one outside. These cylinders were secured to gird- ers running longitudinally with the col- umn, and were raised and lowered by hydraulic power. They had also a cir- cular motion round the column, so that every rivet in the full circumference of the column could be put in by the same power. These machines were so effect- ive that as many as 800 rivets could be driven in a shift of nine hours. The machines were raised with the platform as it rose.
One of the main difficulties in connec- tion with the working of these machines was the supply of steel rivets. Hitherto rivets had either been heated in small hand-blown fires or coal furnaces; but small hand-blown fires could not give the supply of rivets required, and as room for large coal furnaces in a con- venient position to the riveting ma- chines was not available, experiments were instituted with a view to adopting oil for the purpose of heating. These experiments were entirely satisfactory, and it was found that a small furnace, 2 feet 6 inches long by 18 inches square, was sufficient to heat easily all the rivets required for the machine. Since then heating rivets by oil has been very largely adopted in the various iron in- dustries.
After the main piers had been carried to their full height, the erection of the cantilevers was immediately taken in
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CASSIER'S MAGAZINE.
SIR WILLIAM ARROL*
15
hand. The first portion of the canti- levers was erected from small overhang- ing stages by the cranes resting on them. A large platform somewhat sim- ilar to that used in the main pier was then adopted, and was raised by some- what similar means to the level of about 1 80 feet above high water. These plat- forms were not carried further, nor were any more ot a similar nature used, as it was afterwards found that the work could be much more conveniently car-
centre, so that, when they met, the bot- tom boom was first connected, and cer- tain of the temporary connections were thereafter relieved, until the top booms were connected and the remaining temporary connections cut away and the girder allowed to rest on the ends of the two adjacent cantilevers.
After the completion of the central girders, little remained to be done to finish the structure for the opening of traffic, and on March 4, 1890, this cere-
PUBLISHED BY PERMISSION OF F. C. COFFIN.
PONTOON FOR SINKING CYLINDERS OF THE NEW TAY VIADOCT.
ried out from the cranes on the internal viaduct on which the railway now runs, and from those placed on the top member of the superstructure. These cranes, and the small platforms attached to the principals that were being built, offered a more convenient method, which was adopted, for the erection of the remainder of the cantilevers.
After the cantilevers were completed, the next work taken in hand was the erection of the central girders. These were also built by overhanging stages, and special means were taken in con- nection with joining them up in the
mony was performed by the Prince of Wales. At a banquet which followed the opening, and which was attended by many men of note in the railway world, the Prince of Wales announced that the Queen had been pleased to confer the honour of knighthood upon William Arrol for the great ability he had shown in carrying out this great undertaking.
Shortly before the completion of the Forth Bridge the firm of Sir William Arrol & Co. undertook the erection of all the main viaducts and a good many of the swing- bridges for the Manchester
1 6.
CASSIER'S MAGAZINE.
SIR WILLIAM ARROL.
17
Ship Canal Company. About the same time also they undertook the erection of the steelwork for the Tower Bridge across the Thames in London. This bridge in many respects is one of the most novel in Great Britain, having opening bascule spans in the centre, and a high-level footway overhead to allow of passenger traffic proceeding even while the bascule spans are open. In the carrying out of this contract
levels. This, however, was merely an optical delusion, as the central girders met exactly, both as to line and level. After the piers and high-level roadways had been completed, the main chains were erected on a stage, and the ap- proach from the river to the main piers was connected to the chains and com- pleted. The opening ceremony was performed by the Prince of Wales in June, 1894.
PUBLISHED BY PERMISSION OF F. C. COFFIN, ASST. ENGINEER.
THE NEW TAY VIADUCT. PONTOON USED IN TRANSFERRING GIRDERS FROM THE OLD TO THE
NEW PIERS.
it was necessary to stage the River Thames right across, with the excep- tion of the centre opening. The piers were built of steel, with an outside cov- ering of granite. The overhead foot- way is made up of cantilevers and cen- tral girders, and was erected in a man- ner somewhat similar to that adopted at the Forth Bridge. Before the cen- tral girder was joined up, to an observer standing on London Bridge it would seem that the two girders, coming out from the main piers, were at different 1-2
The firm of Sir William Arrol & Co. do not confine themselves to the work of bridge-building, but carry on a very large general business in mechanical engineering and in all kinds of struc- tural work. They manufacture to a very large extent the riveting machines patented by Sir William, which are adopted in most of the leading ship- building and iron centres throughout Great Britain, and also in other coun- tries. In recent years they have also introduced and developed the Arrol-
i8
CASSIER'S MAGAZINE.
THE ERECTING SHOP OF SIR WM. ARROL & CO., LTD. THE ROOF IS WHOLLY COVERED BY GLASS.
Foulis stoking plant used in connection with gas works.
This plant consists of machines for charging and withdrawing the retorts after breaking the coal to proper di- mensions and raising it to hoppers by elevators from the coal stores, thus re- ducing the labour bill to a very large extent. In connection with such oper- ations the results have been so success- ful that the cost of carbonising in many works has been reduced by one shilling per ton of coal handled. When it is mentioned that hundreds of these ma- chines are in operation, and that even under one single management where they are adopted the quantity of coal handled is equal to 600,000 tons per annum, it can at once be seen what an immense saving the adoption of this
plant entails. These machines are used very largely not only in Great Britain, among others by the three principal gas companies in London, but also in many of the principal gas works in Europe, Australia and the United States.
In connection with structural work, Sir William Arrol & Co. make a spe- cialty in designing and erecting all kinds of buildings in steel, and one special feature that is always kept in view is the lighting of these, which is usually done by having the roofs en- tirely covered by glass instead of by slates or other material. The first of these buildings was designed by Sir William about eighteen years ago for the Greenock Foundry Company, in connection with some large extensions which they were making to provide new
SIR WILLIAM ARROL,
19
machine and fitting shops, and it was so efficient and economical in upkeep that several others have been erected for the same firm, as well as numbers for other firms throughout Great Brit- ain, for engineering works, boiler works, foundries, tanneries, stables, etc.
After the completion of the Forth Bridge the services of Sir William Arrol came into much request in connection with scientific, political and philan- thropic work, so that he was compelled to relinquish the active management of his business. By the reconstruction of his firm he secured greater leisure for the growing public calls upon his time.
Sir William was asked to contest the constituency of South Ayrshire, and, in 1895, was elected to Parliament as the representative of one of the largest constituencies in the whole country. This he still represents.
It is not easy for the writer, who was Sir William Arrol's engineer and man- ager during the construction of the Forth Bridge, and who has been his partner since its completion, to write in any other than an enthusiastic strain of him. To know him in private is to learn to admire his many good qualities. While he is human, and. therefore, fallible, his better side is so genuinely real that it dominates his character. Sir William is, and has al- ways been, a man of the people. He is shrewd, and gifted with sound judg- ment and good common-sense, and his life work has proved him to be a man of great energy and perseverance. In nature he is most sympathetic and gen- erous, and in him these qualities take a very practical and real form, to the comfort and advantage of many. Per- haps, however, the quality which has
most impressed those who know him best is that of tolerance. Many a time has he departed from the strict rules of business to "let off" an unfortunate contractor who was losing on his esti- mates, and has in some instances even gone the length of making good his loss.
Like all pure-minded men, Sir Will- iam is a lover of the beautiful, and gratifies his tastes in this way to a con- siderable extent. In his house at Sea- field, near Ayr, he has gathered a choice collection of pictures and works of art. Although not an ardent politician, Sir William is faithful in attendance to his Parliamentary duties, while at the same time not neglecting the many other calls upon him in connection with his direct- orship in such companies as J. & P. Coats, Limited; A. & J. Stewart & Menzies, Limited, and others. Not only does he fulfil all these public duties faithfully, but he also finds time to de- vote to his own business, in which he is always ready to assist with his serv- ices and counsel.
With such a range of duties one would think he could not be other than fully occupied ; but in addition he takes an active interest in work connected with infirmaries, the Chamber of Com- merce, and other public institutions. In Sir William Arrol we find another illus- tration of the truth of the old adage that "it is the busy man who finds leisure to do the most work." Rest for him and men of his type is best and most efficiently secured by change of occupa- tion. Rich in health and energy, Sir William has the prospect of many years of usefulness still before him, and his friends prescribe no limit to the good he may yet accomplish.
MINE TIMBERING IN THE UNITED STATES.
By John Birkinbine, M. Am. Inst. M. E.
w
HEREVER mining is carried on, timber is used as a support to ground which has been dis- turbed by excava- tion. The quantity, the size, the char- acter of the wood, and the method of framing or placing the limber are influ- enced by the abun- dance or scarcity of convenient forests, the width of the mineral vein matter, lode, or lens to be removed, by the dip of the strata, by the quality of the vein and the ad- joining rocks, and other considerations. In operations prosecuted where the material excavated is such as to safely sustain the roof or walls by pillars, the quantity of mine timber employed may be insignificant, and the application of supports may be confined to single props or stulls. In others, the character of the vein matter or of the inclosing walls, and the length, width or pitch of the deposit of mineral to be won, may de- mand liberal quantities of mine tim- ber, applied in various methods which add considerably to the cost of mining. In open-pit excavation timber may be required for other purposes than sup- ports, and in some pits supplemental drifts need to be protected; but as this paper is intended to discuss timbering applied as artificial support to unsafe ground in mining, the comparatively limited employment in the "open" may be dismissed.
In passing, notice should, however, be taken of the liberal application of
wood in connection with mining opera- tions independent of that used for sup- port. Below ground the ventilating and drainage systems, the landing plat- forms, the chutes or winzes, the tram- way tracks, sleepers, and the mine cars; and above ground the shaft or head houses, breakers, power houses, tres- tles, shops, dwellings, sorting platforms, bins, railroads, etc., all demand rough timber or sawn lumber. Ample wood tor other uses than support is an essen- tial for mining, and the absence of this may cause mines to lie idle which, under more favourable conditions, would be active.
So important is an ample supply of timber, that the general custom in word- ing mining leases has been to specify whether or not the lessee will be per- mitted to cut timber from the lands of the lessor for use in the mine or mines; and the right to thus employ the surface resources for the prosecution of under- ground operations, is considered a val- uable feature in the rentals of many mining properties. An abundance of mine timber so closely influences the success of mining that some large com- panies buy outright, or purchase " the wood leave " of timber lands, and main- tain extensive equipments of machinery and considerable forces of men to fell trees, and cut, frame, and handle the necessary timber.
There are mines, wrought entirely underground, which require but little, if any, timber to sustain the walls or roof, as shown by the illustration on page 2 2 ; but even in these there are usually portions of the excavation where artificial supports must be applied, and in this class of workings, shafts or slopes may necessitate heavy and costly fram- ing for protection. On the other hand, even placer deposits which are worked
P3 3U
MINE TIMBERING IN THE UNITED STATES* 21
VL
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CASSIER'S MAGAZINE.
by " hydraulicking, " with water brought in iron pipes, require lumber for the flumes, riffles, and other acces- sories.
To obtain minerals by underground mining, the productive vein, lode, lens, strata or bed, is reached by a horizontal tunnel or " adit," by an in- clined " slope," o^ by a vertical " shaft," and the material is excavated by connecting the " adit," " slope " or 11 shaft " with a series of tunnels, or " levels," leading to smaller tunnels or *' drifts," or to larger excavations
safe pillars, or where the walls confining the vein matter are amply stable that the outlay for timbering underground workings and the shafts, slopes, gang- ways or tunnels leading to them, does not form a prominent item in the cost of mining.
The other extreme is where, prac- tically, every foot of excavation must receive support as work progresses, and these supports require frequent renewal or repeated relief from exces- sive pressure.
The timber requirements, at most
MINE THAT NEEDS FEW TIMBER SUPPORTS.
known as " rooms." In a majority of mines the ''shafts," "slopes," v* adits," 41 levels," " drifts," and " rooms " must be maintained by artificial sup- ports, for which purpose timber is employed.
Upon the maintenance of these arti- ficial supports depends the lives of those employed, and the permanence of the mine as a producer. It is only where the material to be extracted occurs in quite narrow veins, or where the min- eral itself is sufficiently rigid to form
mines, demand the constant services of a gang of men above ground, framing, and a gang below ground, placing new, or renewing old, timbers. To facilitate the handling of the sticks required, spe- cial timber shafts or slopes and timber chutes are not unusual. Some of the large mines maintain extensive wooded tracts from which the mine timber is cut, and well-equipped mills in which the timber is framed by machinery.
There are several mining operations in the United States which use month-
MINE TIMBERING IN THE UNITED STATES.
LIGHT TIMBERS USED IN CAVING SYSTEMS.
ly for mine supports one million or more feet, board measure, of timber. It will, therefore, be evident that the surface forests are being rapidly trans- ferred to form underground forests which sustain the excavations made in prosecuting the mining industry. It is stated that the Comstock group of mines in Nevada consumed the timber from 200,000 acres of forest land up to 1897.
and the table below is presented merely to indicate the extent of the mining in- dustry of the United States. Accord- ing to the reports of the United States Geological Survey, the following quan- tities and values of the more important mineral products were taken from the earth during the year 1896. The notes concerning mining are added to indicate the probable dependence upon timber supports :—
Mineral Products of the United States During i8g6.
Mineral. Quantity or Value
Bituminous coal 137,640,276 net tons
Anthracite 48,523,287 long tons
Iron ore 16,005,499 long tons
Building stone $31,346,171.
Character of Mining. .Underground. .Underground. .Mostly underground. .Quarries.
Petroleum 60,960,361 barrels Obtained from wells.
Limestone for flux 4,120,102 long tons Mostly quarried.
Silver 58,834,800 troy ounces ..Obtained underground.
Gold 2,568,132 troy ounces Partially underground, partially in the open.
Copper 460,061, 430 pounds Underground.
Lead ..188,000 short tons ..Underground.
Zinc 81,499 short tons Underground.
Gypsum ...224,139 short tons Mostly quarried.
Cement 9,513,473 barrels Mostly quarried.
Pyrites 115,483 long tons Mostly underground.
Salt 13,850,726 barrels Obtained from wells.
The column with the caption " Character of Mining " indicates the predominant class of exploita- tion and not the universal practice, for most of the minerals are won partially underground and par- tially in the open.
It is difficult to even approximate the quantity of timber annually demanded for mine supports from the statement of the amounts of various minerals won,
In addition to the above-named products, a number of others were won and marketed, which required timber- ing in their exploitation, such as man-
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CASSIER'S MAGAZINE.
LARGE " STtTLLS.
A MINE LANDING.
MINE TIMBERING IN THE UNITED STATES.
25
ganese ore, corundum and emery, ^quicksilver, sulphur, graphite, barytes, and cobalt.
The grand total valuation of mineral products in the United States for the year 1896 was $637,717,288 (/127,- 543,457), and probably over 220,000,- 000 tons of material were extracted from the earth by underground operations which contributed towards this output. The volume represented by this tonnage would approximate an excavation one square mile in area and 125 feet deep, or a shaft or drift of aver- age size, 7^ x 10 feet, ex- cavated for a length equiv- alent to the diameter of the earth. The latter compari- son will suggest the de- mands for timber in under- ground mining in the United States.
The life of timber placed in underground workings is influenced by its char- acter, by moist or dry air, and alterations of the same; and by the tendency of the strata to crush the timber, or to " creep. " Unless the wood is brittle, the chances are that ex- cessive pressure, such as would destroy the sup- ports, will give notice in advance of rupture. There- fore, watchfulness on the part of timbermen, or min- ers, and attention to these indications reduce the risk to life from " squeezes."
There are occasional instances where, notwithstanding liberal supports, large areas which have been mined, cave in. But there are more fatal accidents re- ported from detached portions of roof or sides falling, or from blasting, than from falling timber supports.
Where the ground in mining opera- tions " creeps" or " swells," the tim- bers must be reinforced, or the swelling ground repeatedly removed, so as to relieve the pressure. To the uninitiated the extent to which mining ground * ' creeps " or • ' swells ' ' without de-
stroying the timber is marvellous, and in some cases those familiar with mining phenomena are astounded that timber: withstands compression under enor- mous loads until its volume is reduced to less than one-half of the original with- out losing its general structure or en- tirely destroying its value as a support. In some of the drifts run in the wide veins of the anthracite coal regions of Pennsylvania, swelling ground necessi- tates constant removal of the excess material. In one instance the ' ' creep ' '
A. BRTCK SUPPORTING ARCH IN THE TILLY FOSTER IRON ORE MINE, NEW YORK.
raised the bottom of drifts (which were about 7 feet in height) so that the open- ing would, practically, close in two days; and measurements of the material removed from the bottom of the drifts so as to keep them open, aggregated a thickness of 45 feet of coal.
In some cases the weight upon mine timber compresses it to stone like hard- ness, a piece of pine 17 inches in length having been reduced to 4 inches. Yellow pine, taken from the lower levels of the Comstock mines, has been so compacted by enormous pressure as to
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CASSIER'S MAGAZINE.
A SAMPLE OF GANGWAY TIMBERING.
have the density and weight of lignum vitae. It has been stated that none of the shafts there are in perfectly good condition, being forced out of line by the rocks moving and swelling. There are, elsewhere, numerous shafts in use which, although originally vertical, are forced into curved or zigzag lines, and slopes could be instanced in which there are very decided " humps."
A feature of mine timbering which demands the best eftorts of the engi- neer is the construction of shafts, or slopes, for these must be planned to last throughout the productive life of the mine. They give access to the work- ings, are the avenues through which the materials are brought to the surface, and generally supply space for air and waterpipes. The timber framing must, therefore, be of ample strength to sus- tain the thrust of the strata and be truly fitted for the cages or skips to traverse them at satisfactory speeds, and must be generally reliable as a means for en- tering or retiring from the mine.
These structures are consequently ex- pensive, and are often costly to main-
tain. The Lake Superior region in the United States, especially the copper range on the Keweenaw peninsula, of Michigan, presents some excellent ex- amples of this kind of construction. Slopes which exceed one mile in length follow the dip of the copper ore and ac- commodate skip cars travelling 3000 feet per minute. Two vertical shafts in the district penetrate the earth for nearly 5000 feet, and in these even greater speeds of lift are maintained.
The Red Jacket shaft of the Calumet and Hecla mines has reached a depth of 4900 feet. It is composed of six large compartments, four of which are used for raising rock and lowering tim- ber. Work upon this shaft has been prosecuted for 8 years at a cost approx- imating $2,500,000 (^500,000). The opening of this shaft is 650 feet above Lake Superior and 1250 feet above ocean level. The bottom of the shaft is, therefore, half a mile below the deepest portion of the bed of Lake Superior, and nearly three-fourths of a mile below the ocean level.
The simplest form of mine support is
MINE TIMBERING IN THE UNITED STATES,
27
a prop or stull, placed between the foot and hanging walls, generally approach- ing a right angle with the dip, or verti- cally between the floor and roof of a drift,4 stope, chamber, or room. As a rule, the top of the prop, or stull, and some- times the bottom, is supplied with wedges to secure firm support, and with plates made of plank for slabs to aug- ment the surface contact and distribute the crushing force on the end of the stick. ^
The stulls vary in size from 6 inches in diameter and 6 or 7 feet long, to 3
cribs of enormous size are employed, requiring the use of great quantities of timber.
Ordinarily mine timbering is consid- ered as made up of " sets " consisting of two props, or legs, whose length ap- proximates the height of the drift or room, and a cap resting on the props, whose length corresponds to the width of the openings. As a rule, the legs are vertical, or nearly so, and the caps and sills, where required, are horizon- tal. Sometimes one leg of a' set is placed at an angle approximating the
A *' SQUARE SET " SYSTEM.
and 4 feet in diameter and 20 to even 30 feet in length. When the props are of insufficient strength, they are placed in groups or " batteries " and are held together by iron bands. Where local conditions require strong support over a considerable area, 4< cribbing" is in- troduced, the timber being laid horizon- tally and the interior rilled with mine refuse. In some of the large mines.
dip, that on the foot-wall side being nearly vertical and shorter than that on the hanging-wall side, so as to give a horizontal floor to the drift, the cap be- ing also horizontal.
Where the floor is insecure or soft, sills are provided, and on these the props are supported. The sets are located at such intervals as the character of the material requires, and the space
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CASSIER'S MAGAZINE.
between is protected by small poles, saw-mill slabs, and plank, known as lagging. These sets are also held in place by horizon-braces or " stuttles." Where the ground requires constant support, false sets, supporting fore poles, driven ahead of the permanent sets, are temporarily employed. With firm side walls doubtful roof material may be supported by caps let into the walls, and props are then unnecessary. The lagging extends from cap to cap as when the sets are used.
The tendency of the roof rock to break into an arched form has, in some important mines, encouraged the use of a sill, two legs and segmental caps whose outline approximates to part of
wide at the floor line, and 6 feet 8 inches high in the clear.
'* Herringbone" timbering, planned to take advantage of the natural ten- dency of the loose roof material to form an arch, is arranged with a long round timber placed longitudinally at the top of the drift or tunnel, supported by di- agonal props from the sides and cov- ered by lagging. This method, how- ever, requires that the walls be suffi- ciently firm to sustain the thrust of the props.
Some systems of mine timberings which appear to be intricate, indicate careful study of the requirements and judicious application of the principles of supporting rock or earth with a min-
AT THE FOOT OF A SHAFT.
an octagon, thus approaching an arch in shape. A noted instance of this is in the Cowenhaven tunnel which pierces the Smuggler Mountain at Aspen, Col- orado, for a distance of nearly two miles. This tunnel is 7 feet 8 inches
imum of timber. One, now much irt use, is recognised as the " square set " system or the "Nevada" system, which, while apparently complex, is merely a series of posts, caps, stuttles and sills (sometimes with diagonal
MINE TIMBERING IN THE UNITED STATES.
29
bracing), placed side by side, and above one another, so as to form the outline of a series of adjoining and superposed cubes. Each post, cap, stuttle or sill is framed from a standard to fit snugly, so that when the various parts are as-
More square than round tenons and mortices are now employed.
By the use of square-set timbering some important mines have been oper- ated which it would have been imprac- ticable to work otherwise. The tim-
A VIEW IN A DRIFT, SHOWINfi AN ORE CHUTE.
sembled and firmly wedged against the walls, openings of considerable height may be filled with a system of practi- cally continuous props, each resting on another below, the width or length be- ing similarly spanned by caps, or stut- tles, in continuous lines.
When the walls, roof and floor are kept tightly wedged against a system of 44 square sets," the weight can be safely carried in openings which are too high, wide, or long, for single sticks which could be handled (even if they were procurable), or for independent series of " sets." Some " square sets " are made of round and some of squared timber, the tenons and corresponding mortices being round or square, accord- ing; to the preference of the miner.
bers for square sets are from 5 to 7 feet long, but they are in use in openings whose height, width, or length exceed 100 feet; square-set timber for a room about 100 feet high would be 14 sets or stories in height.
Whether mine timber should be used with or without bark and whether it should be employed round or squared, are subjects upon which there is a di- vergence of opinion among mine super- intendents. The removal of the bark is somewhat influenced by the character of the wood and the readiness with which the log can be stripped. As the squired timber requires less weight to be handled or shipped, and as it can be framed with exactness more readily than round timber, the distance of the source
CASSIER'S MAGAZINE.
TIMBERING IN THE CALUMET AND HECLA MINE.
of supply and the method of timbering adopted often exert influences in its favour.
The foregoing general statements demonstrate that timbering is not only an important, but an expensive feature of mining, and it is to efforts to reduce this cost that many of the improved methods are attributable. The neces- sity of decreasing the cost of mine tim- bering is evident, for as mining in any section is prosecuted, the demands up- on standing timber are augmented and it becomes requisite to transport it from greater distances. It is seldom that any considerable portion of timber, placed in a mine, can be recovered for subsequent use. Decay, injury due to excessive pressure, damage done in re- moval, and, more often, the risk at- tending removal, prevent any appre- ciable economy in this particular.
The caving system, now quite gen- erally employed, permits timber in smaller amounts and of smaller sizes to be used, in place of larger quantities of greater cross section. The illustration of the caving system shown on page 23 exhibits some of this relatively small timber in place.
Efforts to find substitutes for timber as mine supports have been in the di- rection of the use of metal props and caps, masonry piers, and concrete arches. These have found limited ap- plication in Europe, but in the United States the instances are few.
At the Tilly Foster iron ore mine, in New York, the hard magnetic ore was at first removed by sinking on the ore body from the surface. Subsequently underground exploitation left ore pillars to support the hanging wall, the lens at the 165-foot level being 100 feet wide. These pillars cracked, and slips occurred frequently. Brick arches were then sprung from the foot to the hanging wall across the rooms which had been excavated and these arches were cov- ered with masses of concrete to support the steeply inclined walls and enable the operators to secure the reserves of ore in the pillars and below the levels then wrought.
This plan was but partially successful, and finally the overhanging rock was removed, restoring the mine to an open pit by the quarrying and handling of over 500,000 tons of rock at a cost of $250,000 (^50,000). The illustration
MINE TIMBERING IN THE UNITED STATES.
31
on page 25 shows the brick arches and concrete cover as exposed by the sub- sequent open cut operations.
At the Calumet and Hecla copper mine, in Michigan, brick partitions and iron doors are used as a protection against fire, and in some European mines masonry shafts are employed.
With the amount of timber required, as above indicated, the possibility of fire in mines will be suggested, and, unfortunately, this has been the cause of great loss, both of life and of money. The relatively small cubical contents of the exploited portion of a mine may be poisoned by the smoke from a cord, or less, of wood, which the strong draughts quickly carry to the workings. In some cases the damage to mine timbers
has been insignificant, and yet serious loss of life has resulted. In others, fire from a mine has demanded a stubborn fight, with large expenditures for many months, and great damage to the work- ings by destroying the supports of ques- tionable grounds.
Considering the recklessness which is noticeable when lighted candles, or lamps with flaming wicks, are hung on props, caps, or lagging, it is remark- able that mine fires are not of more fre- quent occurrence. Some of the more serious fires have been in mines requir- ing so little lumber as to cause those engaged in them to feel secure, until a blaze, once started, spread so rapidly through the dry wood as to cut off re- treat and cause great loss of life.
PNEUMATIC GRAIN ELEVATORS AND CONVEYORS.
By Fred. E» Duckham, Engineer of the Millwall Docks, London,
IN Cassier's Magazine for Novem- ber, 1897, tne article on " Dis- charging and Storing Grain at British Ports ' ' referred incidentally to the pneumatic elevator invented by the writer. It may be of interest, therefore, to give some further particulars of the pneumatic process as in use for grain handling in Great Britain and on the Continent of Europe.
The grain trade holds a prominent position among the things that have changed during the writer's forty years' connection with docks and shipping. This is attributed partly to free trade and increase of population, but chiefly to the great advances made in steam engineer- ing, in telegraphy, in shipping, and in machinery; for although the popula- tion of the United Kingdom increased from 28 millions in 1851 to 35 millions in 189 j, enhancing the demand for food, and legislature facilitated the supply ol grain from abroad, the importation would be very uncertain and costly if
dependent upon the old methods of negotiation, transport and working.
Forty years ago 300 tons of grain were considered a good cargo, and a five months' voyage to the Black Sea and back was a satisfactory perform ance. The vessels were subject to de- lays everywhere, by wind and weather, by waiting for orders at ports of call, and by tardy unloading by manual la- bour during a liberal allowance of lay days.
The change, though slow at first, ad- vanced with increasing rapidity, grain- carrying sailing vessels being replaced by screw steamers, some of 4000 or 5000 tons burden, making the entire voyage to the Black Sea and back within two months, including the time of loading and unloading their cargoes. Some re- cent cargo steamers for the American trade have, moreover, a dead-weight capacity of from 12,000 to 14,000 tons.
The vessels belonging to the United Kingdom in 1850 had a total tonnage
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of 2)% million tons, of which steamships lions sterling, while in 1897 it reached
represented 186,474 tons> or 4-8 Per 745 millions.
cent. In 1897 the total was just 9 mil- During the 10 years ending 1850 the
FIG. I. DISCHARGING GRAIN FROM STEAMER TO BARGES.
lion tons, of which 6^3 million, or 71 per cent. , were in steamers.
The total tonnage engaged and cleared in the United Kingdom ports in 1850 amounted to 14^ million tons, of which 21-5 million, or 15 per cent., were steamers, whereas in 1 897 the total was
imports of grain averaged 1,022,067 tons per annum; during the 10 years ending 1890 they averaged 6 157,276
FIG. 2. LOADING GRAIN FROM BARGES B B INTO STEAMER C, BARGE D WITH GENERAL CARGO
INTERVENING.
90 million, of which 81 million, or 90 tons: while during the year 1896 they
per cent, were steamers. reached 9,594,136 tons.
The value of British imports and ex- To deal with such increased trade the
ports in 1850, moreover, was 192 mil- old methods of manual labour neces-
PNEUMATIC GRAIN ELEVATORS.
33
sarily gave place to various machinery, notably the endless band elevators which have for some years been in use in America and elsewhere: but as the car- goes to be discharged at British ports are often of a mixed character, e. g. , general goods and packages in the 'tween decks with grain in bulk in the lower hold, it has been found more con- venient to employ hydraulic cranes with buckets or ' ' grabs ' ' for lifting the grain, but admitting at any time of being ex- changed for slings or hooks for the dis- charge of the ordinary merchandise.
With these appliances, however, it is possible to reach only so much of the grain as is within the area of the hatch- way. The other portions, which may extend ioo feet or more forward or aft, have to be trimmed to the machine be- fore they can be lifted. Grain is, more- over, frequently stowed in bunkers and other confined spaces whence it could be discharged only by manual labour and sacking.
Labour uncertainties, and the advent of steamers representing a debit of ^50 to ^80 for each day in port, gave prom- inence to the necessity for some new appliance that could be relied upon to do the greatest amount of work in the shortest time at the lowest cost with safety.
It was with the foregoing re- quirements in view that the writer's attention was directed to the em- ployment of air for elevating and conveying bulk grain. There was no originality in this idea. Air under vacuum as well as underpres- sure had, from time to time, been tried in England and elsewhere, but the several difficulties that pre- sented themselves prevented the successful operation of the ma- chinery. Prominent among these were the impracticability of suck- ing or forcing grain in bulk through pipes, of getting the grain out of any vacuum chamber into which it had been drawn, and of separating the grain, and, when required, its dust, from the air which had conveyed it.
There are two types of the writer' s
1-3
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CASSIER'S MAGAZINE.
pneumatic elevators now in successful operation: — Those that work by suc- tion^ set up by partly exhausting the grain-receiving tanks, into which air rushes through semi-flexible pipes from the ship's hold, bringing the grain with it, as shown by Fig. i , and those that employ air under pressure as well. In these the grain is received by the
A PNEUMATIC GRAIN NOZZLE.
suction process, but is blown from the elevator into the store or into the receiv- ing ship by compressed air, as shown by Figs. 2 and 3.
The dominant features of each type are, to begin with, the construction of the inlet nozzles of the grain- conveying pipes in such a way that air, in the cor- rect proportion and speed for each de- scription of grain, may enter the pipe,
in doing so pick up the grain, and, by admixture, float it along. It is found that the current of air collects and lifts the grain in a gyratory stream having a speed of 20 or 30 feet per second, and that this touches the pipe only at the ends.
Then there is the so-called armadillo hose, which, though flexible, to enable it to be taken anywhere, is so armoured by steel lining as to resist the wear due to the rapid flow of the grain-laden air.
By means of an automatic air-lock the grain discharges itself from the receiver into which it has been sucked, or finds admission into the chamber from which it is to be expelled. This air-lock consists of a twin box, rock- ing on trunnions, one side emptying while the other is filling, an air-tight sliding joint being provided between the loading side and the sup- ply.
An important feature of the machinery is the extrac- tion of the grain, and, when required, the dust also, from the conveying air, so that the solid particles are deposited in the receiver and the air is drawn off to the exhauster.
The construction of the outlet nozzle is such that while ordinarily the grain would emerge like a shower from a pea-shooter it may quietly deposit itself where desired, — at any part of the ship or building.
The latest-made machines of each type are represented by the Chi- cago, at the Royal Albert Dock, with her sister, the Mark Lane No. 2, at Millwall Dock, London, and the Gar?yowen, at Limerick. TheC/izcago and Mark Lane each float on a rectangular hull, 70 feet by 26 feet by 1 3 feet. The engines, boiler, exhauster pumps, etc., are under deck. At about 'midships there is a tower, about 30 feet high by 20 feet square at
PNEUMATIC GRAIN ELEVATORS.
35
the base, supporting a wrought steel cylinder 14 feet in diameter by 16 feet high, having a double-coned bottom, ^ach cone fitted with one of the auto- matic air-locks before mentioned.
This cylindrical receiver is exhausted of air to, say, 5 pounds per square inch below the atmosphere. There are ex- ternally connections for four 6-inch pipes, made up, partly, of rigid steel tube, and partly of the flexible arma- dillo hose. These extend from the re- ceiver to the grain, which is usually stowed in the lower hold of the ship. The pipes often reach a length of 200 feet. They are suspended by suitable tackle, and maybe swung to the cargo, wherever it may be.
The grain, being drawn up through these powerful suckers, soon finds itself in the cylindrical receiver, makes its way out through the air-lock, and is weighed and delivered in sacks or bulk to the consignee's barges. The Chi- cago has, in ordinary work, transferred 135 tons bulk-wheat per hour from the lower hold of an Atlantic liner into barges alongside. It has been found that the system of delivery by sacks, prevailing to a large extent on the Thames, practically limits the capacity of the elevators to this quantity.
The type represented by the Garry- 4>wen is illustrated in Fig. 3. This is not only fitted with the just-described suction arrangement for unloading from ships to barges, but is also able to blow the grain into storehouses or into an- other ship. It, moreover, has the hull and engines of a screw steamer, and often proceeds down the Shannon to partly unload and so reduce the draught of water of grain-laden ships due for Limerick Dock.
The added machinery consists of two compressed-air chambers under deck, into which the stream of grain, after being weighed, may be directed through automatic air-locks, and whence it is expelled by air under pressure of, say, 8 pounds per square inch, through two lines of 8 -inch pipes, laid under the wharf and up along the roofs of store- houses. It there deposits itself through suitable outlets. This machine was de-
mm
signed to unload and house 70 tons per hour; but it has dealt with 1030 tons in 10 hours.
The principal advantages of the Duckham system of elevating and con- veying grain are: —
1. The pneumatic elevator has no limit in capacity. It is practically in- dependent of everything but its own steam power; it relies upon no opera- tion of being fed by men or machines; its flexible suckers reach the grain wherever it is stowed, and the operation of trimming, which, apart from its cost, vexatiously limits the working power of other ship-discharging elevators, is in this case rendered unnecessary. The working cost on ship- board is thus repre- sented by the wages of one man in at- tendance at each pipe, the pipe in this case lifting 35 tons per hour.
2. As previously stated, the large cargo steamers are generally laden with mixed merchandise, e. g. , goods in pack- ages in the 'tween decks and grain in the lower hold. Formerly these two
kinds of merchandise had to be dealt with in succession, as the elevator and cranes could not work simultaneously in the same hatchway. But the pneu- matic suction pipes occupy only a corner of the hatch, and so allow cranes to be employed in discharging the other cargo while they are unobtrusively sucking out thousands of bushels of grain per hour from sundry storage places in the bowels of the big ship.
3. The pneumatic elevator com- mences operation immediately it gets alongside the ship, and proceeds regard- less of weather and light until its work is done.
4. There is an absence of the risks inseparable from ordinary machinery, and in lieu of loss and damage of grain on deck, the grain is aerated and
SECTION OF THE NOZZLE.
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improved by the process of convey- ing.
5. Though the initial cost of the steam power is somewhat greater in this than the old-fashioned elevating machin- ery, the cost of labour is considerably less. This, coupled with the other advantages possessed by the ma- chine, has brought it into favour at several of the European grain ports, and ought to lead to its employment on the American Continent.
Fig. 3 represents a machine intended to transfer 12,000 bushels of wheat per hour from barges into the exporting ship, while lumber and other goods are
being shipped at the same hatchway* Its ability to suck grain from all parts of the vessel without the delay of mov- ing the elevator from hatch to hatch is alone a valuable feature. The grain may, moreover, be screened, graded and weighed during the transmission, and may be delivered in sacks or in bulk.
It may be interesting to note that the London Grain Elevator Company, the owners of two of the Duckham ma- chines, last year discharged 17,475,520 bushels of grain, occasionally 250,000 bushels per day, chiefly from steamers laden at United States ports.
ELECTRIC POWER IN MINING.
By John McGhie.
AN ELECTRIC HOIST AT THE FREE SILVER SHAFT, ASPEN, COLORADO,
THE increase in the adaptation ot electricity to mining work of all kinds during the past three years has been almost as startling in its rapidity and comprehensive- ness as that which marked the earlier years of electric lighting and elec- tric traction. The progress made in these two individual fields on the surface led directly and immediately to the use of electricity in kindred employ in the mine; for what had proved so universally successful in the light of the sun, it was argued, could not prove less so in the depths whither that light never penetrated.
The early attempts, however, were made in trepidation, and to all was not given that measure of immediate suc-
cess which the sanguine, but somewhat inexperienced, engineer had predicted. Yet, in the majority of cases, economies were realised, difficulties of operation diminished, and sometimes even entirely eliminated, accidents to mines and workers reduced, and such satisfactory results generally were obtained that mine operators and owners no longer turned an unwilling ear to the proposi- tion of the electrical engineer to equip their workings with electrical apparatus. As in electric railway, motor and lighting work, one mine installation satisfactorily operating proved a living missionary to every other mine operator in the surrounding district. The results obtained, though occasionally jealously guarded, leaked out, and the figures,
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o
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ELECTRIC POWER IN MINING.
39
finding their way into the columns of the efficient press devoted to the mining industry, gave food for serious reflection to those still dependent altogether on the mule, the steam engine or the air compressor. The question of greater economy, and the consequent greater satisfaction of stockholders, loomed up large and portentous, and as the active propaganda of successful installations became more widespread, its influence became more weighty, the arguments more convincing; and, although con-
however, the mine operator has not only had to consider the question of a future benefit, but also what must appear to him the more serious one of a present loss, and it is a known fact that old ap paratus assumes in the mind of the owner a factitious value as soon as the question arises of discarding it, and purchasing new apparatus in its place. Furthermore, the change involved not only the supersession of mechanical and animal power in the mine itself; it in- volved the installation of a complete
AN ELECTRIC HOIST AT THE MALTBY COLLIERY OF THE LEHIGH VALLEY COAL CO., WILKESBARRE, PA.
servatism is still strongly entrenched, the eventual equipment with electrical apparatus of all mines, with few excep- tions, is now no longer a false prophecy, — it is almost a foregone conclusion.
Progress, however, has been, to an extent, hampered by considerations which did not enter largely into street railway and lighting work, but which have played an important role in the electric mining field. In the case of electric street railways and electric light- ing stations, new industries were to be created, which for capital might appeal to the whole world. There was no question of extinguishing the value of an existing investment.
In arguing electricity into a mine,
steam and electrical generating plant at the same time. Electricity, therefore, has been compelled to show that its adaptation to mine work would not only mean future economy, but, also, that its economy would be sufficiently large to compensate for the extinction of the value of the apparatus at present in use. That it has been shown capable ot this is, perhaps, best demonstrated by the very large number of mines now using electrical apparatus, and the still larger number in which the use of electricity is proposed and almost decided.
It will hardly be disputed at this date that electricity is the ideal power for use in the operation of mines, and that the advantages it offers, and the benefits
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CASSIER'S MAGAZINE.
AN ELECTRIC MINE LOCOMOTIVE BUILT BY THE WALKER COMPANY, CLEVELAND, OHIO.
which accrue from its use, cannot be equalled or even approached by any other known power, whether animal, steam or air. A power that needs heavy piping; that demands expensive protec- tion in very cold weather and constant expensive maintenance; that cannot be transmitted satisfactorily over long dis- tances; and that operates machinery demanding constant attention, com- pares poorly with a power that requires two or three slender wires only for its transmission; that gives off no heat, nor smoke, nor moisture; that is un- affected by change in temperature, how- ever severe; that can now be trans- mitted over long distances, which, five years ago, would have been deemed fabulous; that can be employed indiffer- ently above or below the surface, by day or night, or continuously the twenty-four hours through, and that drives machinery which demands the minimum of attention. And when to these advantageous features are added decided economies in the operation of the workings, cheapening, and, at the same time, increasing the output, while
demanding no extensive expenditure for maintenance, the attractiveness of elec- tricity as motive power is irresistible.
There is nothing peculiarly distinctive in the adaptation of electricity to min- ing work. The problems solved in other fields recur in almost similar shape in the mining field. No new electrical knowledge was required to adapt elec- tricity to the operation of the mine loco- motive, mine hoist, mine pump or coal cutter. Mechanical experience and mining knowledge combined speedily applied the motor to the machinery which it was fitted to drive.
The problem of the economical trans- mission of electric power to, and in, mines had already found its solution on the surface. Too much mystery is made of electricity in mining work by those gifted with that little knowledge which is admittedly dangerous. There is noth- ing wonderful about it which the world has not already seen demonstrated everywhere in other industries these ten years past, and to approach to-day the question of an electrical mine equipment with any feeling that electricity is a
ELECTRIC POWER IN MINING.
41
mysterious and little-known agent, in- stead of a useful, fully-known and read- ily-controlled force, argues more than the usual ineptness.
Great progress has, in fact, been made in electrically- operated machin- ery. Electrical and mechanical com- ponents have acted and reacted upon each other, the requirements of the one •demanding more perfect workmanship in the other, until the completed device within the past few years has advanced toward a perfection previously incon- ceived. The electric mine locomotive of to-day bears but slight resemblance to the first one, built almost before the trolley car was an accomplished fact; and the electric mine pump, driven by the early direct-current motor, with
weight of the loads and the speed of switching and hauling. The motors are placed as low as possible in as small a space as consistent. They are nar- row, to sit snugly in the narrow space between the wheels; they are wound for both power and speed; the motor casing is made water and dust- tight, and the system of control is sim- ilar to that which has proved so suc- cessful in surface traction.
The advantages of the electric mine pump were clearly perceived from the beginning, and if the mere fact of its extreme portability in the mine had alone been relied upon as an argument, that fact, in itself, would have secured for it the favour of mine operators. With the electric mine pump there is
A MINE HOIST MADE BY THE LIDGERWOOD MFG. CO., NEW YORK, EQUIPPED ELECTRICALLY BY THE BRITISH THOMSON-HOUSTON CO., LTD., LONDON.
-cumbersome galvanised iron wire rheo- stat, is sadly lacking in compactness when compared with the simple induc- tion-motor-driven pump, operated from an extensive three-phase system.
In the design of the electric mine locomotive of to-day every requirement of mine haulage has been considered, — the low roof, the narrow gangway, the
little waste of power in friction and leakage; the space occupied is reduced to a minimum; it may be installed in places not otherwise utilisable; an acci- dent to the conductor can be more readily repaired than one to a steam pipe; the conductors may go down any bore hole in the most convenient way; the cost of maintenance and repairs is
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AN ELECTRIC MINE PUMP BUILT BY MESSRS. HAYWARD-TYLER & CO., LONDON.
small; and the cost of operation, neglect- ing friction, is proportional to the work done. When the pump is at rest all expense in connection with its operation ceases, and the three-compartment shaft so common in mines, i. e. , two for hoist- ing and one for pumping, can be re- duced to a two-compartment shaft, as
discharge pipe and conductors can be confined to one of the hoisting compart- ments.
In addition to the fact that the motor- driven pump can be placed almost any- where in the mine and its position be rapidly changed when necessary, it can be controlled from any point, near or
AN ELECTRIC CENTRIFUGAL PUMP OUTFIT, MADE BY MESSRS. ERNEST SCOTT
CASTLE-ON-TYNE, ENGLAND.
MOUNTAIN, LTD., NEW-
ELECTRIC POWER IN MINING.
43
distant, within the workings or on the surface. It requires the service of no skilled operator, and may be started or stopped by the mere closing of a switch, which may be placed even in the office of the engineer himself at the pit mouth.
The adaptation of the motor to the sinking pump has brought into use a singularly compact device, which allows the gearing and operating mechanism to be entirely inclosed in a water-tight steel casing. This type of pump works as readily under, as out of, water. It may be completely drowned by a sud- den inrush of water in the mine, but its operation continues, the water exerting only a cool- ing effect.
The electrically-driven hoist is undoubtedly the most acceptable machine of its class to the miner. It is in the operation of the steam hoist, perhaps, that every drawback of steam-driven machinery in mines may be realised. Standing over the donkey engine, with its exhaust, its rattle, its vibration and its heat, or by the com- pressed air hoist with every drawback of the steam hoist but the heat, and that changed to extreme cold, the occupation of the operator is one for which there can exist no active competition.
While the electric hoist vibrates, its regular rotary motion cannot be com- pared to the reciprocating racket of the steam piston rod. It gives off no heat, nor does it create cold. It is under the most perfect control, the speed is con- stant, and, like other electrical machin- ery, the power required to drive it is proportional to the load. Like the electric pump, the electric hoist can be located in relation to the incline or shatt exactly where it can be operated to the greatest advantage. These qualities have not been lost on operators, whether of coal or metal mines, and electric mine hoists are now working nearly every- where.
The Free Silver Mine at Aspen, Col. , U. S. A. , has probably one of the larg- est electric hoists in the world. It is a double-reel, flat-rope, over-balanced hoist, with electric power rated at 125 H. P., but capable of exerting 200 horse-power, if necessary. The main motor is a multipolar 100-kilowatt ma- chine, with a speed of 550 revolutions per minute; the auxiliary is a motor of similar type, of 60 kilowatts capacity, and a speed per minute of 475 revolutions. The smaller motor is usually employed to drive an air compressor and a winch for pulling pumps, but is thrown into
AN ELECTRIC AUGUR DRILL IN THE MINE OF THE LOOKOUT COAL CO., WYOMING, PA.
gear with the main hoist-motor when a heavier load than usual is to be handled. The hoist being counterbalanced, the load is reduced to about one-third of that which would be thrown on a plain hoist of the same capacity. The radius of the arms of the reels is 5 feet, each reel carrying 1500 feet of rope 4 in. wide and yi in. thick. The hoist has both car and cage, weighing 5000 pounds, and as in sinking the mine it cannot be timbered to the bottom and the cage cannot go below the timbering, a bucket hangs below the cage. This is 35 in. high, 28 in. in diameter, weighs 400 pounds, and holds 12^ cubic feet of water weighing 800 pounds, or of
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A COAL-CUTTING MACHINE DRIVEN BY A THREE-PHASE INDUCTION MOTOR.
AN ELECTRIC LONG-WALL COAL-CUTTING MACHINE MADE BY THE JEFFREY MFG CO., COLUMBUS, O.
rock weighing 2000 pounds. In case of a sudden inflow of water the hoist is provided also with a bailer, used as an adjunct to the pumps. The maximum hoisting speed with cage and car is 600 feet per minute, using the small pinion of the motor; with the bailer and using the large pinion, about 1000 feet per minute. The voltage used is 525, and the current is taken from a central station at Aspen.
In the Alta Argent mine, in the same district, is another hoist. It is placed at the head of the incline, the position being selected as most convenient for the handling of the ore cars. It is placed on a platform 10 feet above the level at the head of the incline where the cars are stopped and run off. At
this level, with the hoist above him, the operator stands and handles his con- trolling levers and switches, unencum- bered by the hoist, and giving his at- tention at the same time to the cars. One man suffices. Had the hoist been placed directly at the head of the incline two men would have been necessary. The hoist is overbalanced, and is driven by a multipolar slow speed 20 H. P. motor, receiving current at 500 volts trom the station of the Roaring Fork Electric Light and Power Company 3^ miles distant. The transmission wires pass for two miles above ground and for 1 ^ miles through a tunnel and mine workings.
Another example of an electric hoist in situ will suffice. This is driven by a
ELECTRIC POWER IN MINING.
45
direct-current motor and operates in the Maltby Colliery of the Lehigh Val- ley Coal Company, at Wilkesbarre, Pa. The hoist is of the single- drum type, designed to lift 5000 pounds at a speed of 500 feet per minute, and is placed also on a platform above the head of the slope; but the operator, in this case, stands behind the hoist on a separate platform. Standing thus he escapes the vibration of the hoist.
The motor is of the 500- volt, railway type, series-wound, and of no H P. capacity. It is completely enclosed, and is operated by a rheostatic con- troller, equipped with a " magnetic blowout," by means of which any sparks are immediately extinguished in a mag- netic field. The drum is of the stand- ard friction clutch type, 48 in. in di- ameter and 38 in. face, holding about 1400 feet of one-inch wire rope. In operation the empty cars are lowered by gravity, overhauling the rope, while the loaded ones are hauled up out of the levels situated at intervals along the
slope, the lowest being 1200 feet from the hoist. The usual load is four loaded cars per trip, at an average speed of 500 feet per minute. Each loaded car weighs about three and a half tons, and the hoist is capable, in case of necessity, of hauling six per trip. The cars as they pass over the knuckle of the slope pass on to a parting directly under the hoist.
The introduction of the electric cut- ting machine into coal mines has ma- terially contributed to the reduction, not, perhaps, in the price of coal to the consumer, but certainly in the cost of production to the operator. Once elec- tricity is brought into the mine, the electric cutter is an almost necessary adjunct to the locomotive, the hoist, and the pump. The economy derived from its use may be summed up in the statement that the percentage of lump from the machine is twenty-five per cent, greater than from hand labour; that the amount of power necessary to shoot down the coal is much smaller.
AN ELECTRIC LOCOMOTIVE BUILT BY THE GENERAL ELECTRIC CO.
COAL CO., WYOMING, PA.
OF NEW YORK, FOR THE LOOKOUT
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PUMP DRIVEN BY AN ALTERNATING CURRENT MOTOR, MADE BY THE WESTINGHOUSE ELECTRIC & MFG.
CO.. PITTSBURGH, PA., AND LONDON.
i. e., where an 18-in. cartridge is used to break down hand-picked coal, an 8-in. cartridge suffices when the ma- chine is used to undercut the piece.
The rapidity with which the electric coal cutter can be moved is also note- worthy. It can be shifted from the first position and be ready for the next cut in an average of about two minutes; that is, with the props away from the face and the coal properly squared. When the rooms are adjacent, it can be moved from room to room in about fif- teen minutes.
One chain coal cutter will serve as an illustration, as, apart from the motor, the same mechanical features are, more or less, characteristic of all of the chain type. The upper one of the illustra- tions on page 44 shows a coal cutter driven by a three-phase induction motor laid on its side, with its vertical shatt running at low speed and driving the chain sprocket by a single reduction spur gearing. The motor is completely enclosed, and being of the induction type, with neither commutator, brushes nor moving contacts, and consequently sparkless, it can be used with impunity
in gaseous and dusty mines. It stops work when overloaded, and saves the machine from strain and breakage. It reverses and returns automatically as soon as the end of the cutter track is reached. It makes a cut about 4 in. high by 36 in. wide, and in eight hours, in favourable coal, averages eight cuts per hour, or 240 lineal feet in a ten- hour shift. Under the most unfavour- able conditions it will average at least four cuts per hour.
Of electric mine drills two types are in use, — the percussion or reciprocating drill and the augur drill. The latter is a simple augur, turned into the ore vein by a small motor. The mechanism is fixed to a stand, which holds it station- ary in any fixed position to give the drill the necessary angle.
The percussion drill differs from this, both in its operation and its supply. Its mechanism is almost as simple as that of the augur drill, the moving parts having been reduced to a reciprocating steel plunger and a rotating ratchet rod. No electrical knowledge is required to operate the machine. Two coils of wire, alternately energised, raise and
ELECTRIC POWER IN MINING.
47
propel the plunger. These are of bare copper wire of square section insulated with mica alone. The stroke may be shortened almost indefinitely, and a hole started even with a ^-inch stroke, while if the drill is not fed up to the rock and the bit fails to strike, the plunger is automatically cushioned by the coils instead of striking the front head. The drill is stopped and started by the movement of a small handle.
To supply current to the percussion drill demands a special dynamo. This is as simple in construction as the drill itself. It runs at 375 revolutions per
Electric machinery has not been in- troduced into mines without a certain amount of trouble, entirely outside mere missionary work. Conviction has not been obtained without great, and, occasionally expensive, effort. A single example will serve to show this. A prominent manufacturer of electric mine machinery equipped a large freight car with a complete central three-phase station, i. e., with boiler, generator, switchboard and line. This was held ready for installation at the mouth of the mine of any operator desirous of in- vestigating the economy and efficiency
AN ELECTRICALLY DRIVEN ROOTS BLOWER FOR MINE SERVICE.
minute and delivers current from two copper collars on the shaft to the car- bon'brushes, each impulse going alter- nately to the two coils in the drill. The drill operates, consequently, in synchron- ism, each revolution of the armature producing one full stroke of the drill. The device has obtained a good foot- hold in quarry as well as in ordinary mine work.
Electric motors are employed also to drive blowers and ventilating fans, sometimes connected together by belt, but generally directly mounted either on the frame or the base of the blower or fan.
of electric mine operation. Station and mine machinery were left with him, and he was thus in a position to watch both generating and operating machin- ery in comparison with the other meth- ods used in his mine and could judge for himself. The excellent work done by this missionary installation in bring- ing about a change to newer methods was more than surprising,
Within the limits of this article it would be impossible to refer to all the different uses to which electricity has been applied directly in mines or indi- rectly in the allied industries. Electric motors are used to operate dredges and
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CASSIER'S MAGAZINE.
amalgamators in some of the rich aurif- erous placer deposits, and to drive the crushers, rolls and stamps of many im- portant mines.
Electricity finds an extensive use in the world's great electrolytic copper works as well as in the phosphate
beds of the far South of the United States. ; It is used to light the galleried workings of cement quarries and to drive coal conveyors and washers at pit mouths. The consideration of these applications, however, must be reserved for some other time.
MECHANICAL DRAUGHT FOR STEAM BOILERS.
By Walter B. Snow.
From a Lecture Delivered at Sibley College, Cornell University.
has been most extensively applied under all conceivable conditions, until it has become the symbol of artificial, or, as it may properly be designated, of me- chanical draught, and is to-day the ac- cepted substitute for the chimney.
The centrifugal fan, or fan blower, as an apparatus for producing draught, is no new thing. As applied for the purpose of ventilation it dates back to the six- teenth century, but as a substitute for, or auxiliary to, the chimney, its first application appears to have been made early in the present century by Edwin A. Stevens, of Bordentown, N. J. , who, in 1827, arranged a fan for forcing air into the ash pits of the boilers on the steamer North America. But engine speeds and steam pressure were then low; the demand for accelerated com- bustion was not urgent, and experience had not been gained in the proper ap- plication of fans for forced draught. As a consequence, this economic improve- ment, which was to mean so much in later days, was but very meagrely adopted.
It is hardly necessary to here recite the history of the gradual development of this system of draught production. Suf- fice it to say that at the present day the subjectof mechanicaldraught engages the attention of every progressive engineer in the design of a steam generating plant.
Two types of fans exist. The first,
HE chimney has long stood as practically the on- ly available means of producing draught, which, thus produced, has commonly been called " natural draught," and if it satisfactorily met all of the requirements of modern boiler practice, one would scarcely expect to see a substitute proposed. Primarily introduced for the purpose of increasing the rate of combustion, arti- ficial draught was designated as ' ' forced draught," its field of application being considered to begin where that of the chimney ended. By later refinements it has, however, become not only a means of assisting chimney draught, and of pro- ducing the conditions requisite to ac- celerated combustion, but it is now ac- cepted as a convenient and efficient substitute for the chimney under all ordinary conditions.
Artificial draught may be produced by means of steam jets inducing a flow of air, by blowing engines, by air com- pressors, by positive rotary blowers and by fan blowers or exhausters. The fan
MECHANICAL DRAUGHT FOR STEAM BOILERS*
49
INDUCED-DRAUGHT PLANT WITH STURTEVANT FANS IN THE BOILER HOUSE OF THE HOLYOKE MASS. STREET RAILWAY COMPANY.
known as the disc or propeller wheel, is constructed on the order of the screw propeller and moves the air in lines par- allel to its axis. Because of its inability to operate against high pressures, it is practically valueless for draught produc- tion. The second, or fan blower proper, consists, in its simplest form, of a num- ber of blades extending radially from the axis, and presenting practically flat surfaces to the air as they revolve. By the action of the wheel the air is drawn in axially at the centre and delivered from the tips of the blades in a tangen- tial direction. This type may be simply designated as the centrifugal fan, or more properly, as the peripheral dis- charge fan.
The degree of vacuum which may be produced at the inlet, or of pressure which may be maintained at the outlet, of a fan of this type, is dependent upon the circumferential speed of the wheel; 1-4
and the velocity of the air discharged through an outlet of proper size is sub- stantially equal to that speed.
In the attempt to force air at a given velocity through a given pipe, it is the province of the fan wheel, if employed therefor, to create within the fan case a total pressure above the atmosphere which shall be sufficient to produce the velocity and also overcome the resist- ances of the case and the pipe. If, however, the pipe be removed and the fan be allowed to discharge the air through a short and properly shaped outlet, the pressure necessary will, with an efficient fan, be substantially that re- quired to produce the velocity.
The pressure created by a given fan varies as the square of its speed ; the volume of air delivered is, however, practically constant per revolution, and therefore is directly proportional to the speed.
5°
CASSIER'S MAGAZINE.
INDUCED-DRAUGHT PLANT AT THE WORKS OF TH]
PLAIN, MASS.
B. F. STURTEVANT CO., JAMAICA
The work done by a fan in moving air is represented by the distance through which the total pressure is ex- erted in a given time. It varies as the cube of the velocity; that is, as the cube of the revolutions of the fan. The rea- son is evident in the fact that the pres- sure increases as the square of the veloc- ity, while the velocity itself coincidently increases; hence the product of these two factors of the power required is in- dicated by the cube of the velocity.
A fan should never be made so small that it is necessary to run it above the required pressure in order to deliver the
necessary volume. To double the vol- ume under such circumstances requires eight times the power; three times the volume demands twenty-seven times the power.
The chimney as a means of creating a movement of air depends upon the heating of that air, by which a difference in density is produced. The heat thus employed is, however, absolutely wasted so far as its utilisation for any other purpose is concerned. Any at- tempt to extract more of the heat from the gases as they escape from the boiler must, with a given chimney, result in a
MECHANICAL DRAUGHT FOR STEAM BOILERS.
reduction of the draught. This inherent loss with an ordinary coal actually amounts to about 20 per cent, when the gases are at 5000 and the excess of air is 100 per cent. Evidently such a great loss as is thus possible should require energetic effort to secure its reduction by means of a more economical substi- tute for the chimney.
Heat being the agency by which the air movement is brought about, the effi- ciency of a chimney must be measured by the amount of heat expended for this purpose. As heat is transformable into work, the efficiency is, therefore, to be measured by the number of foot-pounds of work represented by the pressure difference exerted through the distance moved, as compared with the number of foot-pounds represented by the total amount of heat expended.
It may be shown that when no work is lost in friction, and the respective temperatures of the external air and the chimney gases are 62 ° and 5000, the theoretical efficiency of a chimney 100 feet high will be only about six ten- thousandths. In practice the resistance of the chimney, the cooling of the gases
the work done, or its equivalent in heat units expended to produce the given result, will be about 70 times as great in the case of a chimney as in that of a fan.
All other questions aside, the fan is, therefore, far more economical than the chimney. This economy means that when a fan is employed, the surplus heat can be utilised and the gases re- duced to a minimum temperature before they escape, without impairing the draught.
The methods of application of me- chanical draught may be broadly classi- fied under two heads, — the plenum and the vacuum methods. Under the plenum, or " forced," draught, method the air may be supplied in either of two ways. First, by making the ashpit practically airtight, and forcing the air into it. Second, by making the fire room itself practically airtight and main- taining therein the required air pressure.
Under the vacuum or "induced" method there is practically only one means of application, — the introduction of an exhausting fan in the place of a chimney. A short and comparatively light stack usually serves to carry these
AN ASHPIT DAMPER IN A BRIDGE WALL.
and other causes combine to reduce even this extremely low efficiency.
If in the place of the chimney there be substituted an engine-driven fan of proper size, the resultant of the effi- ciencies of the steam boiler, the engine, and the fan, together with the loss of fric- tion in the apparatus, may be reasonably taken at about 4 per cent. Therefore,
gases sufficiently high to permit of their harmless escape to the atmosphere.
Evidently, the method of application to be adopted must depend upon cir- cumstances. It cannot be said that un- der all conditions any one of these three principal methods, or their numerous modifications, is superior to the others.
The application of mechanical
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CASSIER'S MAGAZINE.
draught presents a three-fold opportun- ity for increased economy in steam pro- duction. First, in the reduction of avoidable losses; second, in a decrease in the first cost and resultant fixed charges on the entire generating plant; and third, in a reduction in the operat- ing expenses, principal among which is the cost of the fuel. In addition, me- chanical draught possesses certain ad- vantages which cannot be directly meas- ured in money values, such as its pecu- liar adaptability to the requirements, its independence of climatic conditions, its flexibility and the like.
A resultant efficiency of ioo per cent, on the part of either the coal or the boiler is an absolute impossibility be- cause of certain inevitable losses inci- dent to the combustion of the coal and the operation of the boiler. Although under the best conditions over 80 per cent, of the full calorific value of the fuel may be utilised in the production of steam, yet, it is true that this high standard is seldom reached in ordinary practice. An efficiency of only 60 per cent, is common practice, and even 50 per cent, is far from exceptionally low.
The losses which are more or less avoidable are: — First, those due to in- complete combustion, as usually evi- denced in the presence of smoke and carbonic oxide in the flue gases and in unconsumed coal in the ashes, as well as to a small amount of hydrogen or marsh gas which may pass out with the gases.
Second, loss from excess of air, due to the fact that to secure practically per- fect combustion, air is usually supplied in excess of the theoretical quantity chemically required for combustion. This loss is twofold, being dependent upon the quantity of unused oxygen and associated nitrogen and upon the moisture in the air.
Third, the loss resulting from too high temperature of the gases leaving the boiler. This loss, except in so far as it is influenced by the air supply and the rate of combustion, is dependent upon the design of the boiler and its appurtenances, and, therefore, is not chargeable to the character of the fuel.
It is one of the most important factors in fuel efficiency.
Fourth, loss of heat by removing ashes at too high a temperature. This, by care, may be reduced, but not en- tirely avoided.
Fifth, loss by radiation. This may be reduced by increasing the thickness of walls and covering all exposed por- tions of the boiler. But from a practi- cal standpoint it can never be entirely avoided.
The losses resulting from incomplete combustion are manifestly due to inade- quate supply or imperfect distribution of the air. The presence of smoke in- dicates an absolute loss. Although this seldom exceeds one per cent, in ordi- nary practice, even this amount may be almost entirely eliminated and the smoke nuisance may, in most cases, be practically avoided by such regulation of the air supply and the intensity of draught as is possible under the condi- tions of mechanical draught.
Nearly forty years ago, Rankine wrote that " in furnaces where the draught is produced by means of a blast pipe, like those of locomotive engines, or by means of a fan, the quantity of air required for dilution, although it has not yet been exactly ascertained, is cer- tainly much less than that which is re- quired in furnaces with chimney draughts : and there is reason to believe that on an average it may be estimated at about one- half of the air required for combustion." Such has since proved to be the fact.
Theoretically, the amount of air chem- ically required for the combustion of one pound of coal is about 12 pounds; but practically, with chimney draught, the amount actually supplied, including that resulting from leakage, is far in excess and varies greatly under different conditions. Donkin and Kennedy have shown by gas analyses that, in the case of sixteen different plants, the air supply ranged between fifty-six per cent, and three hundred 'and twenty eight per cent, in excess of the chemical require- ments.
If the air is supplied in excess of that necessary for perfect combustion, there
MECHANICAL DRAUGHT FOR STEAM BOILERS,
53
is a definite loss, disregarding that due to moisture in the air, which is twofold in its character: — First, the excess of air entering the furnace is heated by the burning fuel, thereby lowering the temperature of the mixture of gases and air below that which would prevail if the gases only were present. As a conse- quence, the rate of absorption of heat by the water is reduced, for it is de- pendent upon the difference in temper- ature between the water and the gases.
Second, owing to larger volume and higher velocity, there is less time to part with the heat, and the temperature of the mixture of gases and air escaping to the chimney is higher than would be the case if there were no excess of air, while the increased volume is such that the total amount of heat thus carried away, without exerting any useful effect, is greatly increased. In other words, paradoxical as it may seem, the larger the volume of air supplied, the higher will be the temperature of the escaping gases.
A high furnace temperature and low stack temperature, other things equal, are evidently conducive to greater effi- ciency. It has just been shown that such conditions are incident to a reduc- tion in the excess of air supplied. But perfect combustion with a small supply of air will result only when it is inti- mately distributed throughout the fuel. For such intimacy of contact intense draught and a clean and reasonably thick fire are necessary, conditions which may be most readily maintained by means of mechanical draught.
With a thick fire the air is compelled to come in contact with a greater amount of fuel and afforded a better opportun- ity to promote perfect combustion. This points to the efficiency of reason- ably high rates of combustion. When secured under proper conditions, with a given grate area and boiler, any in- crease in the rate must be accompanied by an increase in the total air supply, and hence a probable increase in the temperature of the escaping gases. But if the total consumption remaining the same, the grate area be reduced, the rate of combustion per square foot of
grate will of necessity be increased, and the efficiency of combustion may be greater. Clark states that " the pro- portion of surplus air required appears to diminish as the rate of combustion and the general temperature in the fur- nace is increased," and that " the sys- tem of forced draught opens the way for increase of efficiency in facilitating the adoption of grates of diminished area in combination with acceleration of combustion."
With a decreased supply of air, the intensity of the fire is increased, its temperature is higher, more heat is radiated to the exposed boiler surfaces, and more is taken up by the gases. Furthermore, the diminished superficial area of the grate and of the exposed in- terstices between the fuel necessitates a higher velocity to secure the admission of a given volume of air. This in- creased velocity in turn requires greater draught or air pressure.
If a given grate be reduced one-half, and the rate of combustion be doubled, the same volume of air would have to travel through the exposed interstices at twice the velocity. But the pressure or vacuum required to produce this velocity would be four times as great, and, as a consequence, the air would be forced or drawn into spaces between the fuel which it could not reach under less impelling force. Much more intimate contact and distribution are the results. Less free oxygen passes through the fuel bed unconsumed, and for a given supply of air a higher efficiency of the fuel is attained.
Undoubtedly the source of the great- est loss in boiler and fuel efficiency lies in the usual high temperature of the escaping gases. In seventeen inde- pendent boiler tests, Donkin & Kennedy found the heat lost up the stack, when no economiser was used, to range be- tween 9.4 per cent, and 31.8 per cent, of the total heat of combustion.
With the chimney, a comparatively high temperature of the rejected gases is an absolute necessity for the produc- tion of the draught. Its production by means of a fan is, on the other hand, independent of the temperature of the
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CASSIER'S ^MAGAZINE.
MECHANICAL DRAUGHT FOR STEAM BOILERS.
55
gases, and there is, therefore, oppor- tunity to utilise the heat which is a positive and unavoidable loss in the case of a chimney.
In this direction lies one of the great- est opportunities for increasing boiler efficiency. Although additional surface may be obtained by reducing the size of the tubes and increasing their num- ber, or by ribbing them, or introducing retarders, it is usually customary to ab- stract the surplus heat from the gases by some means in a sense independent of the boiler. It may then take the form of a feed-water heater, otherwise known as an econ- omise^ or the lorm of a de- vice for abstracting the heat from the gases and transfer- ing it to the air supplied to the fuel, or both.
The results obtained by any of these methods have, in the case of chimney draught, al- ways been restricted by the cost of the excessively high chimney necessary to produce the requisite draught with the decreased temperature and in- creased resistance. The sim- plicity and efficiency of me- chanical draught, however, obviates this difficulty, and makes possible the attainment of a much lower final tempera- ture of the flue gases with a corresponding increase of effi- ciency. So far as production of draught is concerned, the gases may be cooled down to atmos- pheric temperature, but the practical limit is necessarily above this because of the expense of the abstracting ap- paratus required.
Numerous forms of heat abstractors have been devised for the purpose of transferring the heat from the escaping gases to the entering air. The How- den apparatus, which is largely em- ployed on shipboard, is illustrated on page 54. Forced draught is used. An- other system, known as the Ellis & Eaves, is provided with larger abstrac- ors and is operated by induced draught.
Retarders in the tubes, as well as
such devices as the Serve ribbed tubes, have shown a considerable economic gain, by a reduction of the stack tem- perature, and with both mechanical draught has been shown to be most de- sirable.
We may now consider the influence, from a commercial standpoint, which the application of mechanical draught exerts upon the aggregate first cost of a steam-boiler plant. For this purpose there has been selected a plant of rea- sonable size of which the detailed cost is known. This plant consists of 8
BRIDGE DECK
UPPER DECK
THE BOILERS, FA.NS AND HEAT ABSTRACTORS IN THE STEAMSHIP " KENSINGTON."
modern water-tube boilers, each of 200 horse-power normal rating, set in pairs, making a total of 1600 horse-power. A chimney is provided, 8 feet in in- ternal diameter and 180 feet high, of sufficient capacity to overcome the resistance of the two feed-water econo- mises and produce the draught nec- essary for any probable forcing of the boilers. The detailed cost of that portion of the plant which concerns the present discussion is, in round num- bers, as follows : —
8 water-tube boilers of 200 horse-power
each - $25,000.00
2 feed-water economisers 7,000.00
Boiler and economisers, setting and by- pass 6,000.00
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CASSIER'S MAGAZINE.
A DUPLEX FAN FOR A BOILER PLANT, MADE BY THE B. F. STTJRTEVANT CO., BOSTON AND LONDON.
Automatic damper regulator and dampers 300.00
Chimney, complete 0,000.00
Building, complete 11,000.00
$58,300.00
In the other plan there are two fans, each driven by a separate engine. Each fan is capable of independently producing the draught for the entire plant, and thus serves as a relay, if de- sired. Such an apparatus, with the short stack, can be installed complete, under ordinary conditions, for about $3500 (^700). The total economy in first cost effected by the introduction of the mechanical draught plant, which amounts to a reduction of about 62 per cent., may be indicated as follows; the saving of space occupied by the chim- ney being neglected : —
Chimney Draft.
Cost of chimney $9,000.00-
Cost of damper regulator and dampers 300.00
$9,300.00 Mechanical Draft. Cost of fans, engines, draft regulator, and
short stack, installed complete .$3,500.00-
Saving by use of mechanical draft. 5,800.00
$9,300.00-
A still further reduction might have been secured by designing the plant so as to operate the boilers at somewhat above their rated capacity, as could be readily done by means of the same me- chanical draught apparatus. The omis- sion ot one boiler would bring the rated capacity down to 1400 horse-power, and would call upon the fans to increase the steaming capacity of the other boilers by only about 14 per cent, above the
MECHANICAL DRAUGHT FOR STEAM BOILERS*
5?
normal. This would show an addi- tional saving in first cost which may be thus presented: —
i, boo Nominal Horse-Power Plant.
Cost of 8 boilers _ $25,000.00
Cost of setting's, etc 6,000.00
Cost of building- 11,000.00
$42,000.00 7,400 Nominal Horse- Power Plant.
Cost of 7 boilers $21,875.00
Cost of settings, etc., about.... 5,50000
Cost of building, about 10,500.00
Saving by use of mechanical draft 4,125. 00
$42,000.00
This shows a possible supplementary saving on the entire plant of $4125 (^825), which makes a total reduction ot" $9925 (,£1985) to be credited to the account of the mechanical method. Of course, the fixed charges for interest, taxes and insurance will be correspond- ingly reduced. Had this comparison been based upon the cost of a plenum
of the steam used in producing draught would be reduced to practically noth- ing.
The value of the land may be an im- portant factor in first cost. If figured at $2 (8 sh.) per square foot, for£in- stance, the omission of the chimney would in this case save $990 (^198), and the reduction in the number of boil- ers, $960 (^192) on the cost of the land required for the plant.
The total net saving in first cost of a single plant, under the given conditions,, may be thus summarised : —
By omission of chimney and damper $5,80000
By reduction in number of boilers 4,125.00
By saving in space occupied by chimney . ggo.oo- By saving in space by boiler omitted g6o.oo
$11,875.00
This total saving is made possible by the expenditure of $3500 (^700) for
INDUCED-DRAUGHT PLANT ON THE ELLIS & EAVES SYSTEM AT THE STEAMSHIP PIER OF THE AMERICAN LINE, NEW YORK.
or forced draught plant, the saving in the cost would have been shown to be even greater because of the smaller fan required.
In any properly arranged plant the exhaust steam from the fan engine would be utilised so that the actual cost
the mechanical draught apparatus ; that is, the saving is nearly three and one- half times the expenditure necessary to secure it. The reduction of $11,875 (^2375) m tne cost would indicate an annual saving in fixed charges of about 1 (/166) to $890 (^178), accord-
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CASSIER'S MAGAZINE.
mg as the aggregate of interest, taxes and insurance is taken at 7 or 7^ per cent.
This amount would, under conditions of the best economy, be practically suffi- cient to cover the cost of operating the mechanical draught apparatus, provided no attempt was made to utilise the ex- haust steam, and would far more than cover it were this steam usefully em- ployed. When to the economical ad- vantages already pointed out i.5 added the increased convenience of mechanical draught, its positive character, its ready adaptability, its independence of cli- matic conditions, and its instant re- sponse to any demand for increased steam supply, the account stands deci- dedly to its credit. Therefore, any fur- ther saving, as, for instance, in the cost of the fuel burned, is clear gain over and above any expenditure that may have been made on account of the introduc- tion of this method.
Under ordinary conditions the steam- ing capacity of boilers may be greatly increased by the application of mechan- ical draught. This is equivalent to a reduction in the number of boilers re- quired to secure the same capacity. Howden has shown that in the case of a certain vessel the cost of the boilers, fittings and connections, for the same output was $63,000 (^12,600) less with his system of forced draught than with natural draught. Such a reduction on shipboard is twofold in its effect, for it leaves so much more space unoccupied and thereby increases the carrying ca- pacity of the vessel.
As a further factor in the matter of cost it should be noted that the fan pos- sesses a definite advantage over the chimney in that it is portable and is al- ways a valuable asset. The chimney, on the other hand, is a fixture; it is suited only to certain conditions and is practically valueless unless those condi- tions exist.
The largest and most important factor in the operating expense is the cost of the fuel itself, which should be meas- ured, not by the number of pounds, but by the available heat units obtained for a given price. In this cost are properly
included the transportation charges, the expense of getting the coal into the boiler house and putting it into the fur- nace as well as taking out and carrying away the ashes.
The ability to utilise cheap fuels is an inherent advantage of mechanical draught, due to the fact that such fuels, being, as a rule, finally divided, with a large percentage of dirt and ash, require an intense draught for their combustion.
In addition to the economic advan- tages of mechanical draught which have been presented, there are others which relate primarily to the convenience of installation and operation. Prominent among these is the feature of adaptabil- ity. The fan, which is usually of steel plate, may be constructed in any shape to meet specific requirements, may be located as desired with regard to the position of the boilers, and, without ex- pensive foundations, may be used for either forced or induced draught, and, because of its portability, may be re- located or exchanged for another of different capacity In its operation it is perfectly flexible, may be run at high or low speed, independently of the chimney temperature, and is always susceptible of instantaneous change in response to sudden demands. A mere change in engine cut-off produces an effect secured with a chimney only by adding to its height at great expense.
External temperature changes have no appreciable effect upon the operation of mechanical draught, which above all else is independent of climatic condi- tions. The fan is a most important factor in smoke prevention, and in con- nection with the closed-fire room sys- tem the resulting ventilation is of vital importance.
Briefly summarised, mechanical draught has here been shown to be capable of reducing the avoidable losses, of decreasing the first cost of a steam generating plant, and of reducing the fuel expense. In addition, it presents cer- tain marked conveniences in the matter of installation and operation. In these days when every step in the process of steam generating and utilisation is being scrutinised in the attempt to reduce the
MECHANICAL DRAUGHT FOR STEAM BOILERS.
59
cost by even a single per cent. , the op- portunity presented by the employment of mechanical draught cannot be and is not overlooked, The economical neces- sity was not so imperative when Ran- kine and Clark, long ago, pointed to its marked advantages ; and the future was but dimly discerned when, only fifteen years ago, Seaton referred to the chim- ney as a rough and ready, but exceed- ingly wasteful, way of inducing the air to flow into furnaces with sufficient velocity to cause the fuel to burn, and
prophesied that it would some day be superseded by more scientific and economical apparatus.
What these men foresaw, we to-day realise. Mechanical draft now stands so well established in the engineering world as to lead a noted engineer to re- mark that " the building of tall chim- neys to secure draught simply advertises the owner's lack of familiarity with modern improvements, or his want of confidence in results easily demon- strated."
f
'-' '.-"7- "*;>
JS%r&
COAL WASHING.
By H. L. Siordet, Associate of the Royal College of Science.
HE object of a coal washing plant is to rid the coal which comes from the pit of all stones, slate, shale, pyrites and other impurities, with which it is always mixed to a greater or less ex- tent. Some coals have these impur- ities finely dissem- inated all through them, and in that case it is necessary to disintegrate the whole bulk in order to be able to prop-
erly separate the coal. Other coals con- tain the impurities in greater or smaller lumps, many large lumps of coal being practically quite free from foreign mat- ter. In that case it is generally the custom to preserve the large lumps for the market as nearly whole as possible, and with soft coal especially great care is taken in handling it so as not to break it up more than can be helped.
When the impurities occur in lumps sufficiently large to be readily detected by the eye, the process of picking these out by hand is resorted to with advan- tage. The usual method employed in washing coal embodies a practical ap- plication of the different specific grav- ities of the component parts of a mass
A COAL WASHING PLANT ERECTED BY THE HUMBOLDT ENGINEERING WORKS CO., KALK, NEAR COLOGNE ON THE RHINE, GERMANY. 60
COAL WASHING.
61
COAL WASHER MADE BY THE HUMBOLDT ENGINEERING WORKS CO.
of coal as it comes from the mine. Of the two bodies of the same size the one with the greater specific gravity will sink the faster when placed in water. Now if the water in which the bodies are immersed be agitated in such a way that a continuous upward pulsation is produced it may be possible to regulate this pulsation in such a manner that the lighter body is kept floating and can be washed over, whereas the heavier body remains at the bottom. This is the principle of the jig or washer.
The mixed coal or shale is brought into a box or tank filled with water, running over, and the water is kept moving up and down by successive strokes of a plunger or piston.
It will be evident from the above that besides the washer proper a thorough arrangement for classifying is necessary in a coal washing plant, otherwise there would be large pieces of low specific gravity and small pieces of high specific gravity collected together at the bottom of the washer. With ore dressing it is, in most cases, the valuable products which have the greater specific gravity, whereas with coal it is almost invariably the impurities that are heavier.
Let us assume that the coal to be dealt with is sufficiently pure in the larger lumps to go straight to the mar- ket, and that the shale or impurities occur as lumps of all sizes! The coal is brought up from the mine in tubs or small waggons. These are run into so-called tipplers which turn the whole waggon over, emptying the contents on to a screen. According to the value laid on the coal not being broken up through rough treatment, various devices are applied, both to the tipplers and the screens.
The former may be provided with special shoots or aprons to allow the coal to slide gently on to the screen, or the tippler itself may be driven with a variable speed, having a relatively slow motion whilst the coal is being emptied.
The screens may be of various kinds. The simplest of these is the common bar-screen, consisting of bars laid us- ually on an incline and placed at certain distances apart. The small stuff falls through the spaces and is treated in further machinery, and the -large stuff slides along the bars, to be afterwards either hand-picked or loaded at once into railway waggons for transport.
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A COAL WASHING PLANT EQUIPPED BY THE JEFFREY MFG. CO., COLUMBUS, OHIO.
SECTION OF A JEFFREY-ROBINSON COAL WASHER.
Many other screens are devised for screening off the small stuff and moving the large along gently. One of these ingenious contrivances is the Humboldt- Klein screen, which throws the coal upwards and forwards and catches it again gently further along the screen.
If the large stuff is still composed of lumps of coal and of stones, it is usual to submit the whole to the process of hand picking. This is done by passing the rejection from the bar or other screens on to an endless band, or me- tallic belt, called a picking band. Boys or girls stand along each side of this belt and as the coal slowly moves past them, they pick out the stones and rub- bish, and the coal itself runs off to the railway waggons. Care has again to be taken not to let the large coal drop from any great height into the waggons, and for this purpose devices, such as anti-breakage shoots, are used. These are endless bands which can be lowered down to the bottom of the trucks, or raised, and carry upright angle irons or plates at certain distances apart, which, in moving down the incline, carry the coal gently along with them.
COAL WASHING.
63
The stuff which is small enough to tail through the bar or other screens, called the screenings, must now be sep- arated into pieces of equal size. This is usually done in a revolving screen with several concentric shells, each hav- ing different-sized perforations. The different sizes fall down troughs or launders direct into the coal washers, of which there are one or several for each size, according to the quantity of
a bed of perforated metal on which the stuff to be treated is deposited. In the coarse washer these perforations are smaller than the stuff to be treated. The coal, which is lighter, is carried away, over the top of the washer, hav- ing been raised sufficiently by the pal- pitating action of the piston on the water; the impurities, on the other hand, being heavier, are not raised by the jigging action of the piston, but run along the bottom of the bed under the action of the flowing water and are al- lowed to run off through a special open- ing at the same height as the perforated
ELEVATION OF A COAL WASHING PLANT BUILT BY THE JEFFREY MFG. CO.
stuff to be treated. The revolving screen has, of course, the number of shells proportioned to the number of sizes of washed coal required for the market.
As a rule, two distinct kinds of washers are used in a coal washery. The one kind is called a coarse washer, and is used for treating any size down to, say, y^" or ^"; and the other is called a fine- washer, as it treats any size from, say, y2" or W! down to dust.
The washers are both arranged with
bed. This process is called washing over the bed.
In the fine washers the process is somewhat different. Here the perfora- tions of the metal bed are larger than the stuft to be treated; but instead of the stuff coming on to the metal bed direct, this is covered by a layer of coarse felspar, which cannot pass through the perforations. The light stuff, or coal, is again washed over the top of the washer, but the heavier im- purities find their way gradually through
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A TROUGH WASHER, SHOWING THE TROUGH RAISED. BUILT BY THE SCAIFE FOUNDRY AND MACHINE CO., LTD., PITTSBURGH.
the felspar bed and through the perfor- ated sheet and are deposited in the bot- tom of the body of the washer, whence they can be run off to the rubbish heap. This latter process is called jigging, or washing through the bed.
Of course, the water used in these washing machines carries off a quantity of fine particles of coal in suspension, and in order to collect this, the overflow water from the washers is run off to settling pits, where the sludge is de- posited. The water, when sufficiently clarified, is pumped back to the wash- ers. The fine sludge is then let off from underneath the settling tanks or pits and is often carried to its destination by a scraper conveyor.
The illustration on page 61, repre- sents a coal washer of the general type just described, built by the Humboldt Engineering Works Company, of Kalk, Germany, and clearly shows some of the working details mentioned.
On page 62 is shown a sectional view of an American machine built by the Jeffrey Manufacturing Company, of
Columbus, O. It consists principally of a well-built cone, of heavy plate steel, having at its lower end a specially arranged water jacket. Inside this cone is a rotating shaft provided with arms and blades, and operated by power from the head, as shown. This shaft is turned at the rate of about eight revolutions per minute. The blades projecting down into the cone keep the material in a constant state of agitation. The lower end of the cone is provided with two valves, operated by means of levers. A water tank or reservoir is usu- ally arranged overhead, although in some cases the water is fed direct from the pump through pipes connected with the water jacket, out of which the water passes into the washer through various openings so as to supply it equally on all sides. The force of the water is regu- lated by means of valves so that the pressure is made to correspond with the specific gravity of the coal that is being washed. The overflow water is collected in a suitable tank and by means of a pulsometer pump is again forced
COAL WASHING.
65
into the reservoir or direct to the washer.
The coal passes into the centre ring B of the washer from spout A, while the water supply enters at E through perforations G. The coal is kept in a continual state of agitation, and, as it sinks into the tub, is met by the upward current of the water; the good coal being lighter in weight than the impurities, is forced upwards, as indicated by the upward turned ar- rows, and out at D; the impurities, be- ing heavier in weight, sink below in the
or falls direct into the cars. The water from the overflow is collected, and by means of the pump is again forced into the tank or washer for further use.
Another type of American machine is the trough washer, one of which is shown in the illustrations on this page and the one opposite, being made by the Scaife Foundry and Machine Company, Ltd., of Pittsburgh. In this case the body of the washer is a rigid, almost semi-circular iron trough, two feet in diameter and twenty-four feet long. Its movable
THE SCAIFE COAL WASHER. TROUGH LOWERED.
direction of arrows turned downward, and ^are collected in the chamber J. When this is filled, the upper valve H is closed and the lower valve H is with- drawn; this allows the accumulated ref- use to be discharged, after which the lower valve H is closed and the opera- tion is repeated.
A general elevation of an outfit using this washer is given on page 63. The go pd coal passes from the washer proper on to inclined perforated chutes or screens, and is freed from the water, after which it is either carried by means of conveying machinery to storage bins
i-5
side is strengthened somewhat to facili- tate the discharge of impurities. Inside it has a series of fixed dams or partitions, which can be readily made higher or lower by bolting plates to them or by cutting, should the nature of the coal require such changes.
The trough is made so heavy that it should last many years without repairs. It is carried along one side by a series of hinges which attach it to a cast iron frame supporting the whole apparatus. A shaft running the entire length of the trough turns in babbitted journals bolted to the frame. It is given a reciprocat-
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ing motion by means of an arm in its centre, worked by a connecting rod at- tached to the flanged driving pulley. As the trough and frame are inclined, the driving pulley on the main shaft should be moved along its shaft a little out of line, in order to make the belt run properly. This pulley should also have a clutch to start and stop the washer.
On one side of the washer pulley is seen an iron spool with its chain, clutch and operating lever. The latter has a steel tongue which enters an eye in the centre of the movable side of the trough and thus holds the trough up. The long shaft carries a considerable number of stirring arms or forks. Two large weights, supported by forged arms fas- tened to the trough, counterbalance the greater part of the weight of the empty trough, and throw it back as far as de- sired when dumping the refuse. These weights are movable along the arms, so that their lifting moment can be varied at will. The lifting chain is wound a couple of times about the spool, and at its lower end is a weight (not seen in the illustrations) which gives the neces- sary tension to the chain, and partly counterbalances the weight of the filled trough.
Coal is fed with water at the upper end of the trough. By the combined action of the flowing water and stirrers, the slate, pyrites and other impurities settle to the bottom and are caught be- hind the dams in the trough, while the clean coal passes over the top and out at the lower end. When the spaces between the dams are entirely filled with impurities, the supply of coal is stopped or it is temporarily turned into an adjacent washer, and all the remain- ing coal is washed over the dams. The operating lever is moved a few inches to the right, which draws the steel tongue out of the eye and allows the
trough to drop free and discharge the refuse.
Should any dirt remain in the trough it can be quickly washed out by means of a water box or pipe discharging into the entire length of the lowered trough. By moving the lever a few inches still further to the right, the spool clutch is thrown out and the trough raised. The washing is then recommenced.
Probably nowhere has coal washing been so highly perfected as in Germany, due to the pressing needs there of a process of this kind because of the rela- tively large amount of impurities carried in German coals. The Essen district is particularly remarkable for its many coal-washing plants, clustered round about the town of that name, and they all give evidence that the Germans have spared neither money nor thought to make these plants, with all their intri- cate machinery, models of complete- ness.
One of the striking features in some of the best coal washing plants of the district is the cleanliness within the buildings, considering the nature of the material treated. It is a fact that one may spend a whole day in some ol them without so much as soiling one's white collar, and at the end of the day one is certainly not more in need of a wash than after a couple of hours' walk through the average manufacturing town burning soft coal. Where such coal washing plants are erected on a large scale, one finds, as a rule, that everything connected with the mine is in keeping; for instance, the winding plant, the pit-head gear and other de- tails; and the comfort of the workmen and colliers is also well attended to. Warm baths are on the spot for all the men, and it is a pleasant sight to see a shift of men coming up from the mine all spick and span, with no trace of the pit left on them.
COMPRESSED AIR ON WARSHIPS>
By Passed Assistant Engineer T. W. Kinkaid, U. S. N.
A VISITOR on b oard a modern man-of-war, be it cruiser or bat- tle - ship, must, after only a cur- sory examina- tion of the ves- sel, be impressed chiefly with two prominent features, — the multiplicity of mechanical contrivances, and the heat and discomfort encountered on the lower decks of the ship. The me- chanical devices are labour savers; and their builders attempt to combine in their designs the characteristics of great power for space occupied, lightness, economy of energy consumed, durabil- ity, and freedom from noisome qual- ities.
Formerly all auxiliary machinery on board ship was designed to work by steam or by hand power. The disad- vantages of steam as used to distribute power throughout a structure like a steamship, with its many closed com- partments and tortuous passages, have long been evident; but new competitors, like hydraulic, electric, and pneumatic systems of power distribution, have had no quick triumph over steam. Engi- neers and mechanics are familiar with the ills of steam machinery, and, when difficulties arise, they are met with the accumulated skill and confidence of many decades. With new systems a new fund of experience must be ac- quired before the conservative will per- mit the ousting of the steam engine, in spite of its known tendency to unduly heat a compartment, to saturate the air
with unwelcome moisture, to scorch adjacent woodwork, to produce un- sightly rust stains, to first corrode then burst its piping, to produce obnoxious smells from its lubricating oil, and others more. Of course, much of the heat in the interior of a warship is due to the fact that the engines and boilers occupy perhaps two-thirds of the ship's length; but the numerous steam and exhaust pipes leading to and from the more or less distant auxiliary engines add greatly to the heat discomfort.
In considering the question of install- ing a compressed air system on board of a man- of -war, it must be recognised that there are two principal classes inta which air motors can be divided, name- ly, those which are to run continuously or nearly so, and those which are used for short periods only. The character of the motor service reacts upon the design of the compressors. The con- tinuously-run motors, as, for example, ventilating fans and flushing pumps, should appropriately be driven by air from an economical form of compressor. Such a compressor, in order to furnish a large output of air per pound of steam consumed, must possess the complica- tion, high cost, and greater weight which are the inevitable concomitants of a high degree of economy. On the other hand, the motors which are only occasionally brought into use may not only be of the simplest construction themselves, but the air compressor as- sociated with them should possess light- ness, reliability, and cheapness rather than great economical efficiency that would be, in the end, dearly bought.
One of the mooted questions of com- pressed air service relates to the em- ployment of reservoirs. In shore work,,
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where weight is not a bugbear to the designer, reservoirs are freely used as separators of moisture, and, when lo- cated near the motors, to steady the flow within the supply pipes. On board ship a reservoir of moderate size near the compressor is admissible, especially if the compressor be not kept constantly running; and it may sometimes be thought advisable, in the case of an in- termittently-used motor, to locate a storage tank at the motor end in order to reduce the size of supply pipe from the compressor. Whether or not weight is saved by this arrangement, it is un- questionably easier and cheaper to lead a small pipe through bulkheads and around obstructions than it would to run a pipe one or two sizes larger.
Then there are special conditions which seem to warrant the storage of air at very high pressures in order that a supply at lower pressure may be avail- able at short notice. This is the case on many battle-ships, where a small high-speed compressor fills a battery ot steel flasks to a pressure of 2000 pounds per square inch, the pressure falling to about 1350 pounds when a torpedo is connected up and charged. The sup- ply of air taken by one Whitehead tor- pedo weighs 50 pounds. On torpedo- boats, however, the flasks are not used, on account of the weight involved. The United States dynamite cruiser Vesu- vius', which fires aerial torpedoes, carry- ing each an explosive charge of 500 pounds, stores air at a pressure of 1500 pounds per square inch.
A reservoir of sufficient capacity to operate a large motor for any consider- able length of time must necessarily be of great weight and bulk, and would, therefore, be inadmissible on board cruising ships. Were it not for the drawbacks mentioned, it would be prac- ticable for a man-of-war to utilise her surplus steam power, when lying at anchor, or when proceeding slowly, to pump up a supply of compressed air sufficient to operate her turret and magazine machinery and much of her auxiliary machinery during an entire action.
The location of a ship's air compres-
sors should oe in or near the engine rooms or fire rooms. This plan of loca- tion not only reduces the length of the steam and exhaust piping required, but also places the machines within reach of a body of mechanics who can attend to their regular steaming duties and to the compressors besides.
The air of the engine rooms is not suitable for use in a power transmission, not only on account of its comparatively high temperature, but also because of its high relative humidity. Modern practice aims to secure the air as cold and as dry as possible. The colder the supply, the greater the weight of air that can be taken by a given compressor in a given time.
Special air ducts should be led to the compressor valve chambers from the upper deck of the ship. Moisture man- ifests its injurious quality at the motor, where the expansion of the air under ordinary circumstances produces tem- peratures low enough to form snow if watery vapour be present. The snow thus formed is almost certain to clog the passages of the motor and put it temporarily out of use. It is sometimes the practice to inject water or even steam into the air supplied to the motor, but both of these plans are objectionable in the warm living spaces of a man-of-war. Heating the air at the motor not only obviates snow for- mation, but very greatly improves the economic efficiency — sometimes as much as 50 per cent. But reheating devices, if used on board ship, would destroy at once one of the great ad- vantages of a compressed air transmis- sion.
When power is to be transmitted to a considerable distance, the high tem- perature resulting from the compression of the air is sure to be lost before the motor is reached, and therefore it is ad- vantageous to cool the air in the com- pressing cylinder, compressing it as nearly isothermally as possible, and thus economising power. But on ship- board the length of the transmission is not great and a moderate amount of cooling suffices, especially if the trans- mission pipes are to be lagged. It is
COMPRESSED AIR ON WARSHIPS,
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necessary for the smooth running of air pistons, and for their tightness as well, to provide a steady lubrication, and the oil used undoubtedly interferes with the cooling efficiency of the jackets. On the other hand, the oil supplied to the com- pressor cylinder is carried along with the air and ensures the lubrication of the motor cylinders and the preservation 01 the interior surfaces of the piping.
Piping on shipboard is necessarily very tortuous, and much of the re- sistance to the air in its transmission is due to bends and elbows. A pressure of 80 or 90 pounds per square inch should be used. High pressure is suit- able for the intermittently used motors, as it keeps their size down to convenient limits; but excessive pressure not only means a loss of economy in the opera- tion of the continuously-run motors, but increased liability to leakage also. If a motor be run sometimes fast and at other times slowly, there will, in the latter case, be considerable throttling of the air, because at the reduced speed the full pressure of the main cannot be utilised. The expansion of the air un- der such circumstances may produce such a low temperature as to seriously interfere with the working of the motor. The remedy, one which has been sug- gested by mining practice, is to provide a throttle valve at some distance from the motor, so that the air, cooled by expan- sion (wire-drawing), can again absorb heat from surrounding objects. The motor cylinders should not be lagged; in fact, their exposed surface should be large, so as to favour the absorption of heat from the warm atmosphere of the compartment.
Recently manufacturers of jet blowers have effected improvements in their ap- paratus which seem to place these blow- ers on an equal footing, as regards economy, with the ordinary simple re- ciprocating engine using steam or com- pressed air to drive a fan. Although there is not much danger from snow formation in the motors used on the lower decks of a man-of-war, yet the jet blower obviates that difficulty entire- ly and at the same time effects a great economy in the weight of the ship's ven-
tilating apparatus and in that of the forced draught appliances of the boilers. Induced draught is considered the most desirable form of artificial draught. It is certainly the most convenient and the one least harmful to furnaces and tubes; and the jet offers the simplest means of obtaining it. Rotary engines are much used in air power transmissions aboard ship. They are not economical, but they are compact and light, and well adapted for winch service, for example.
The double-bottom compartments of a warship must be fitted with means for freeing them of water, although it is likely that for a majority of the com- partments such means will never be brought into requisition. The long lines of expensive and heavy piping which are commonly run from the vari- ous compartments of the double bottom to the auxiliary pumps could be dis- pensed with entirely were means pro- vided for putting a moderate pressure of air in any compartment, the water being expelled in such a case through a short pipe into the bilges above. In the case of a badly leaking compartment, an air pressure of ten to fourteen pounds per square inch would probably suffice to control the leak; and this would seem to be a more satisfactory expedient than to attempt to " pump out the whole ocean. ' '
It is pretty well settled that at least 40 or 50 per cent, of the steam indicated horse-power of the compressing engine can be indicated at the motor. In con- sidering the steam and compressed air systems competitively, we have the facts that in the steam pipe to the small steam motor there is loss by condensa- tion and loss by friction of the moist steam, and in addition, the well-known wastefulness of small engines as com- pared to the large triple expansion en- gine of the central compressor. The central compressing engine has short steam pipes and exhaust pipes, while the small distant steam engine has long piping with many elbows and unions. As regards consumption of steam, there- fore, the two systems are about on a par.
In the matter ot weight, it is probable
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that the steam system still has the ad- vantage, in spite of the fact that the air motor needs no return exhaust pipe, its exhaust being direct into the surround- ing atmosphere, — a grateful, cooling addition to the local ventilation. The weight of the compressor can be kept down by adopting high speed, but at the risk of reduced economy due to wire drawing in the steam ports and also in the air ports.
The shrill noise made by the exhaust of air from a motor is obviated by em- ploying some simple form of muffler. Leading the exhaust into a cylinder full of pebbles has proved an effective and cheap plan; but, of course, the muffler adds to the back pressure and also to the total weight of the system.
In a paper read by Fleet Engineer John T. Corner, R. N. , before the In- stitution of Mechanical Engineers, at Portsmouth, several years ago, that writer gave the following description of a successful compressed air installa- tion for dockyard service: —
" In the most modern part of the dockyard the lifting and hauling appli- ances are worked chiefly by compressed air; the only exceptions are the heavy cranes and sheers, which are worked by steam power direct. The air is com- pressed to 60 pounds pressure per square inch, into eight wrought iron re- ceivers having a total capacity of 18,000 cubic feet. The compressing is done by one or the other of two separate sets of pumps. One set consists of two pairs of compressing pumps worked through gearing, either separately or together, by a pair of simple engines of 90 I. H. P. The other set of pumps is worked by a pair of compound beam engines of 200 I. H. P. This machinery is situated at the main pumping station, about the centre of the yard; and, besides the air compressing machinery, the same build- ing contains the main dry dock pump- ing machinery of 1000 I. H. P., and two pairs of 120 H. P. engines for gen- eral fire and dock drainage purposes. The larger set of air compressing pumps will fill the eight receivers to 60 pounds pressure in one hour. No case of a re- ceiver bursting has occurred here; and
there is no record of a pipe having been replaced during the last two years. There is also less trouble with air joints than with steam and hydraulic joints.
' 'The air pipes, which have a total length of 14,000 feet, or about 2^3 miles, vary from 3 to 12 inches in di- ameter, extend around the large basins, and are connected to forty 7 -ton cap- stans, to five 20-ton cranes, and to the machinery for working seven caissons besides driving a small workshop engine. The air pressure is also used occasionally for driving small engines for carrying out machine work on board ships building, and it has further been connected with the auxiliary steam pipes of some of the larger battle-ships, so that air pressure could be used instead of steam for driv- ing the hydraulic pumping engines on board ships for working the gun gear for drill purposes, and also for driving the electric light engines and other aux- iliary machinery on board. This ob- viates the necessity of getting up steam in the ship's boilers, thus admitting of their being kept systematically in a cer- tain condition, either closed and dry, or quite full of water, which would be impractical if they were being used at irregular intervals and at short notice. "
In air lifts using pistons, a single stroke of which affects the entire lift, jerkiness is apt to be experienced unless a variable hydraulic resistance be op- posed directly to the piston. Oil or glycerine is the liquid used, the resist- ance to the flow of which varies as the square of the speed.
An interesting application of com- pressed air in the United States Navy is found on board the monitor Terror. In this vessel air is used for taking up the recoil of the guns and running them out to battery after firing; for rotating the turrets ; for elevating and depressing the guns; for all the movements of the breech plug, except locking it; for working the telescopic rammer; for blowing out the powder gases, when the breech is opened; for picking up and hoisting the ammunition; and for steering the ship. Even in vessels fitted with hydraulic systems, compressed air
COMPRESSED AIR ON WARSHIPS.
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is usually employed in the accumulators. The accumulator of the U. S. S. Mon- terey is of this type.
On the Terror there are two main compressors, one situated near the for- ward turret, the other near the after turret. By means of a communicating pipe, nominally 8 inches in diameter, either compressor can supply either tur- ret. A smaller high-speed compressor, located in the main engine room, sup- plies the air for steering, and also an- swers for light service in the turrets when it is not desired to warm up the large compressors. There is no separ- ate pump to supply the high-pressure air for the recoil service, but two plun- ger pumps forming parts of the large compressors supply the recoil cylinders, These pumps are thrown out of action by simply closing their suction valves.
The main compressors deliver air at 125 pounds per square inch gauge pres- sure. Although the recoil cylinders are surprisingly tight, yet after some months it is necessary to restore the working pressure in them, and, more- over, the guns are always secured lor sea by being run in, which can be accom- plished only by exhausting most of the air from the recoil cylinders. When the recoil service pressure is needed, the main compressor is started and the small plunger pump takes in air at 125 pounds pressure, delivering it at almost any pressure that may be desired. At present the working pressure in the re- coil cylinders is 550 pounds per square inch. With this pressure the recoil ot the 10 - inch guns with full service charge, 240 pounds, of brown prismatic powder, is about 30 inches.
The recoil cylinders, two to each gun, are secured to the gun saddle. The pistons within the cylinders remain sta- tionary; the cylinders recoil with the gun. The piston rods, which are secured to the rear transom of the car- riage, are large and stiff, so large, in fact, that, with the'air pressure the same on both sides of the piston, the gun is kept run out. When the gun is fired, there is, of course, a banking up of air before the pistons, but an ingenious valve rod, tapered in the middle, ad-
vances with each cylinder into the hol- low piston rod and allows sufficient air to pass from one side of the piston to the other to restrain the rise of pressure within the desired limit. The valve rod is full at each end, so that a proper cushion is ensured at the limits of the recoil and of the counter recoil. The proper proportions of the valve rod were determined experimentally.
The action of the recoil mechanism is all that can be desired. The carriage and its pivots are not unduly strained, and the gun goes out to battery with a motion that is highly satisfactory. The firing of the guns does not necessitate repumping up the recoil cylinders, as the dense air is simply passed from one side of the recoil piston to the other. The maximum pressure in the recoil mechanism depends upon the taper of the valve rod, and never exceeds about 1350 pounds per square inch. The heavy piston rods of the recoil mecha- nism are packed with square machine- braided hemp, well soaked in paraffme. This packing is very efficient, and seems to last indefinitely.
All of the air supplied to the turrets is carried in two pipes, for the high- pressure and low-pressure services, re- spectively, to the central column. This column is provided with passages and leather packed sleeves that give the proper distribution to the various mo- tors in the turret, undisturbed by its rotation. The train of the guns is 270 degrees, the superstructure on the deck of the ship preventing a complete rota- tion.
Two pipes are led along the sides of each gun carriage, one carrying air at 125 pounds pressure for the breech plug motor, the other supplying the recoil cylinders. The latter pipe is a small one, which leaves the carriage near its pivots and there takes the form of a flexible copper coil, which opens and closes as the gun is depressed or ele- vated.
The necessary flexibility for the low- service pipe is secured by employing a short length of hose such as is used in air-brake service. As the breech plug motor recoils with the gun, it is neces-
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sary to employ a telescopic joint. The breech plug motor is simply a cylinder and piston, the latter attached to a sta- tionary hollow rod, the cylinder carry- ing the tray which holds the plug itself. The telescopic rammer is carried on a heavy bracket attached to the gun car- riage. It is always in line with the bore of the gun.
The weight of one of the Terror* s io-inch guns is 56,400 pounds, and the preponderance at the breech end is about 25,000 pounds. The ram which supports the rear transom of the car- riage and determines the elevation of the gun is a simple hollow plunger, suitably packed, and bearing against the tran- som with its upper rounded head. In order to provide a dead beat movement for the elevating mechanism, the pneu- matic system is combined with the hy- draulic, that is, the fluid used under the elevating ram is a mixture of 80 per cent, glycerine and 20 per cent, water; and this liquid is fed to the elevating cylinder from a closed tank. The sur- face of the liquid in the tank is pressed upon by the air from the pneumatic valve of the elevating gear.
When the turret officer in the sight- ing hood moves the valve lever to secure the depression of the muzzle, two valves are moved by the one lever; one valve admits compressed air to the top of the tank, while the other admits the glycerine from the tank into the elevating cylinder. When the lever is thrown to mid-position, the elevating gear is locked, as the glycerine is in- elastic. The other extreme throw of the lever allows the glycerine to exhaust back into the tank and the air from the upper portion of the tank to escape into the turret, the ram meanwhile falling as much as may be desired, and the breech of the gun following by virtue of the preponderance.
The magazine for each turret is lo- cated underneath that structure. Each gun has its own loading car, which moves up and down on a pair of curved tracks formed of steel Z bars. The movement of the car is imparted by a wire rope which leads over six multiply- ing sheaves mounted on the extremities
of an upright cylinder and its ram. The shell is brought out from the shell room in tongs with trolley gear, and is then released into a tray, which swings it into position before the tray of the loading car. Pneumatic power is then applied to tilt the shell into the car. The powder, in two bags of 120 pounds each, is then placed by hand in the other trays of the car, which is now ready to rise. At the height of its travel the car strikes a lug on the bracket of the gun carriage, and has then assumed a position which brings the rammer, the shot, and the bore of the gun all in line. The rope of the car hoist reeves over a sheave on the gun pivot, so that the elevation of the gun, as well as the train, can be changed during the progress of the loading, without altering the relative positions of the rammer, loading car, and gun. This is a very happy arrangement and establishes the superiority of the Ter- ror's turret gear over that found on ships fitted with hydraulic systems, where the guns usually have one or two loading positions to which they must return after each fire.
The turrets of the Terror weigh, with their contents, about 250 tons each. To turn this huge mass rapidly requires the exertion of a large amount of power for a short time. The friction is kept comparatively low by the employment of conical roller bearings. Neverthe- less, to rotate the turret through its full train of 270 degrees in one minute, re- quires the exertion of several hundred horse-power during that brief period. The turret-turning gear consists of a couple of pairs of high-speed engines operating through worm gear and spur gear upon a circular rack fixed to the deck. The fineness of the gear is re- sponsible formuch loss of power through friction, but it is valuable in securing accuracy of train and dead beat move- ments.
The sequence of operations in firing and reloading one of the Terror's 10-inch guns is as follows: — Immediate- ly after firing, the gun returns to bat- tery without shock; a turn of a crank unlocks the breech plug; the rammer
COMPRESSED AIR ON WARSHIPS*
73
reaches out, clasps the plug and with- draws it from the gun into the breech plug tray; the plug motor draws aside the plug; a jet of air plays for a short time into the open breech, driving out smoke and gases from the muzzle; the powder chamber is swabbed out; the loading car finishes its ascent; the ram- mer extends and drives the shot into the gun; the rammer returns; a catch is loosened and the first bag of powder drops into the tray just vacated by the shot; the powder is rammed home; the rammer returns and drives in the sec-
mechanism are concerned, the actual time of loading, from fire to fire, is about i minute, 9 seconds; but the accumula- tion of powder ash becomes serious as the firing proceeds, so that good time for five successive rounds may be put down at about 13 minutes.
The pneumatic steering gear of the Terror is notable for its reserve power and for the simplicity of its mechanism. Two cylinders lie athwartship, facing each other and having a common piston rod. Only the outboard faces of the pistons are used to impart motion. The
WIRE ROPES
FROM STEERING
STATIONS
THE PNEUMATIC STEERING GEAR ON THE MONITOR "TERROR" OF THE UNITED STATES NAVY.
ond bag of powder, which has been re- leased into the tray; the rammer having closed up again, the breech plug slides into position; a stroke of the rammer drives the plug into the screw box, and, as the rammer again closes, a turn 01 the crank rotates the plug through 60 degrees of arc and locks it. While all these operations have been going on, the gun has been laid upon the target. The electric primer is inserted in the breech plug and the gun is reported ready for firing.
As far as the actual movements of the
inner faces are much reduced in area by the large piston rod, and their effective area is utilised only in checking the motion of the piston rod. At the mid- dle of its length this rod carries a slotted head fitted with circular brasses which move the tiller and at the same time allow its angularity to change. An ordinary D- slide-valve distributes the air for the motor. A certain quantity of air is confined in the inboard ends of the athwartship cylinders. This is the air for cushioning, and its elasticity and compressibility relieve the steering gear
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CASSIER'S MAGAZINE,
from dangerous stresses likely to be engendered in a seaway.
A pipe which joins the inboard ends of the cylinders is fitted with a piston valve through which the cushion air must pass if it moves at all. The dis- tributing slide valve and the cushion valve derive their motion simultaneously from a threaded spindle working in a nut mounted on a float lever. This float lever is connected on the same principle as similar levers in marine en- gine reversing gears. When the rudder moves in obedience to the air pressure in one of the cylinders, the motion is communicated to the float lever in such a way as to tend to close the distributing valve and the cushion valve. Thus any tendency to slamming of the rudder from one side to the other is avoided.
Rotary motion is communicated to the threaded valve spindle from various sources. There are steering stations in the ship's pilot house and also in each turret, and each of these stations is pro- vided with both an electric and a me- chanical steering device.
The mechanical devices are simply
steering wheels carrying slender wire ropes to drums near the steering engine and communicating with the valve spin- dle through sprocket gear and toothed clutches. The electric device is in- genious A small motor is geared to the valve spindle with worm gearing. This motor is operated through rheo- stats, and is prevented from over-run- ning, — when the helm is hard over, — by means of a cut-out. All sheaves used with the pneumatic machinery have ball bearings.
The use of compressed air on board ship is chiefly advantageous in that it affords a welcome relief from the heat- ing effects due to the employment of steam for operating remote auxiliary machinery. Not only in time of battle, but during the long weeks and months that precede an action, the officers and crew suffer the evil effects of confine- ment below decks; and the warship which can most ameliorate the condition of her living and working spaces, — especially as regards temperature and purity of air, — stands the best chance, other things being equal, of flying her colours to the end of the fight.
THE DISTILLING SHIP "IRIS," FOR THE UNITED STATES FLEET.
By Passed Assistant Engineer W. W. White, U. S. N., Prise Essayist, American Society of
Naval Engineers.
ON the sea, as on the land, the present is the era of the engi- neer. Especially is this true of the whole fabric of naval war. From the dawn of history until, and beyond, the time when, under Cromwell, the British began their almost unbroken series of naval triumphs, the warrior afloat was, like Blake, a soldier simply. Time and the inevitable logic that the fighting man must know his ship, as well as his weapons, wrought such changes that in the days of Nelson and Collingwood, we find the sailor the su- preme military authority. The soldier and the sailor have as their lineal suc- cessor in this age, the ' ' fighting engi- neer." In giving this apt title to the naval combatant of our day, the Hon. Theodore Roosevelt, until recently the Assistant Secretary of the United States Navy, has said: —
" On the fighting ship, the fighting man must stand supreme; only he must know how to handle his tools and must change as the ship changes, so that precisely as he once knew about sails, now he must know about engines. There can be no divided command. Only one man can exercise it; but he must be thoroughly fitted for it."
The changes which time has made in the ship of the line and her lesser sis- ters, seem more like those of revolution than of evolution. In the old days, the needs of " the fleet in being " were few and simple. It could keep the sea in- definitely with little else than canvas, cordage, wood, oakum, and pitch for repairs; salt beef, hard bread, rum, and water for mess-supplies; and enough powder and round shot to equip the
short and sightless smooth-bores, whose opposing muzzles almost touched in action before their fire became effective.
In this age of the engineer, however, old things have, indeed, passed away, and the warship has become a vast as- semblage of mechanism — steam, elec- tric, hydraulic, and pneumatic — whose requirements are as large and varied as those of a great engineering establish- ment on the land — with this vital differ- ence, however, that to maintain, at a maximum, the fighting value of the modern fleet, its innumerable wants must be filled, whether it lie in the sheltered waters of a home port, or be in an alien and unfriendly harbour, thousands of miles from its nearest base of supplies.
While steam holds its sway as the source of all the varied energies of a warship the fundamental needs of a fleet must be coal, and, with the intricate construction of modern boilers, an am- ple supply of fresh water. The absolute necessity of the latter, for boiler use, is a development of recent years, but fol- lows as an essential condition of keeping the machinery, in its entirety, up to the highest pitch of efficiency. A solution of the problem has been admirably worked out by the United States Navy Department, in providing and equipping two distilling ships for the production and transport of fresh water, which ves- sels, in the auxiliary service of a modern war-fleet, are second only in importance to colliers.
While all modern men-of-war are fitted with appliances for making fresh from salt water, it is not always possi- ble, owing to restrictions in space and
75
76
CASSIER'S MAGAZINE.
weight, to install either an economical plant or one of sufficient capacity for all purposes. In fact, it is only within the past few years that serious attention has been directed to providing a daily supply sufficient not only for drinking, cooking and incidental purposes, but also to replenish the inevitable waste in the feed water for the boilers. The uni- versal practice previously had been to make up the loss of water, due to leak- age in the various pipes, valves, etc., of marine machinery, directly from the sea, a course which had only simplicity to commend it.
With, however, the general introduc-
The introduction of coil, ortubulous, boilers has resulted in making 'the use of fresh water, not only desirable, but indispensable, if this type of generator is to be kept in efficient condition. ^ Sea water is sometimes depended upon to make up deficiencies in the feed water with shell boilers, but it .is resorted to only in dire necessity with coil boilers, where its frequent use never fails to produce disastrous results. Thus far, the tubulous type has gener- ally been restricted, in the United States Navy, to tor- pedo-boats and destroyers; still, the numerous advantages
LONGITUDINAL SECTION AND PLAN OF THE UNITED STATES DISTILLING SHIP "IRIS.
tion of triple expansion engines came the necessity of minimising scale in the boilers, not only on account of the lia- bility to accidents, but, also, from the commercial requirement that increased life should be given the boilers, which, when constructed to withstand high pressures, were extremely expensive in first cost. It was realised, too, that the use of salt water, and the consequent formation of scale upon the heating sur- faces, meant not only an increased ex- penditure of fuel under any circum- stances, but as well, the impossibility for that reason of attaining the former maximum speed, — a factor which is of prime importance in a warship.
which it presents, especially lightnes- as compared with shell boilers, has been a sufficient inducement to wars rant its installation as part of the boiler power in several cruising ships, and it is not improbable that, in the near fu- ture, shell boilers for naval vessels will be superseded by this type.
An apparatus for the conversion of sea into fresh water becomes, therefore, a necessary auxiliary on all sea-going steamships. In its first stage of de- velopment the distiller assumed the elementary form of a nest of tubes, or coil, contained within an outer closed shell, sea water being continually circu- lated by a pump, ^or other means,
THE U. S. DISTILLING SHIP IRIS."
77
through, or on the outside of, the tubes, or coil, with a steam connection led di- rectly from the boilers to the other side. The circulating water, in removing heat, reduced the inflowing steam to water, which then dropped by gravity to storage tanks in the hold. This method possessed the salient fault of quickly causing the vital parts of the boilers to become coated with scale, since, as steam was condensed, its equivalent in volume of sea water had to be supplied to the steam generators, resulting in precipitation of certain salts
that steam originally from the boilers, in passing through the tubes, transfers heat to the surrounding sea water, and thus evaporates it into steam. This causes condensation in the tubes, and water so produced is finally returned to the boilers. Steam formed in the sea water compartment of the evaporator is piped to the distiller, and is there con- densed, if it is intended for drinking purposes. If it is to be used to supply extra feed water for the boilers, any one of three courses, depending upon the arrangement of piping, is allowable,
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QffiDHHQ
LONGITUDINAL SKCTION AND PLAN OF THE UNITED STATES DISTILLING SHIP "IRIS."
on the internal surfaces, of which sul- phate of lime is the most difficult to remove.
To obviate the formation and ac- cumulation of scale in the boilers, evap- orators are now generally installed and interposed between the boilers and dis- tillers. For marine purposes, these consist essentially of a closed vessel containing sea water, in which heating surface in the form of a series of tubes, either straight, bent, or spiral, is dis- posed, and of a construction which per- mits the ready removal of the tubes for cleaning. While there is ample range for variation in the details of different designs, all are similar to the extent
viz., directly to the main condenser; or to the low-pressure receiver of the en- gine to do useful work before condensa- tion; or to the hot-well to mix and raise the temperature of other feed. Of these different arrangements of piping the latter is preferable from the standpoint of economy.
The amount of" make-up feed " re- quired is dependent, in a measure, on the power developed, the number of auxiliaries in use, the extent of steam piping and valves, and, above all, on the care exercised in preventing waste. Generally speaking, it may be taken as from 6 to 8 tons per day per iooo I. H. P. developed.
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CASSIER'S MAGAZINE,
A SET OF THREE EVAPORATORS.
Complication, weight, and space limit the choice of evaporators for warships to the single-effect system, — the ap- paratus just described, — and this type of plant is the only one installed on these vessels. It is usually of sufficient capacity to furnish the extra feed needed for ordinary cruising, but is totally in- adequate for extended steaming at high powers.
It is customary, therefore, to carry in the double bottoms a reserve supply of fresh water for boiler use, procured from the shore. But when a squadron is actively and continuously engaged at considerable distance from a base where fresh water is to be had in quantity, economical distilling ships of great capacity, to follow and supply the different ships as required, become an imperative adjunct to the highest efficiency. To meet the exigency thus developed in the recent war between the United States and Spain, the United States Navy Department, on the recommendation of Commodore George W. Melville, the engineer-in- chief of the Navy, some time ago pur-
chased and fitted out two distilling ships, the Iris, formerly the Menemsha, of the Hogan Line, and the Rainbow \ late the Norse King. The distilling plants of both are the same in all prin- cipal parts, differing only in slight de- tails. The particulars of one, there- fore, answer practically for both. It is to the Iris, however, as having been the first of the two to go into commis- sion, and the first vessel of her kind in the world, that this description relates. It is evident that the controlling ele- ment in the design of a large distilling plant, for the purposes mentioned, is, of necessity, economy in expenditure of fuel, and to insure success in this direction a sufficient allowance of space and weight is essential. As an assur- ance of economy, multiple evaporators, working in series, are installed, by which means steam, generated in the first, or high-pressure evaporator, is utilised to generate steam in the second, or intermediate, and steam from the latter, passing to the third, or low-pres- sure, produces steam which is finally sent to a condenser. It will be observed
THE U. S, DISTILLING SHIP "IRIS.
79
that boiler steam is used only in the tubes of the first evaporator.
The his is an iron vessel, 310 feet between perpendiculars, 38^ feet beam, and 27 feet depth of hold. Her main machinery, which was built in 1885 by Messrs. R. & W. Hawthorn at New- castle-on-Tyne, England, consists of a compound engine with cylinder di- ameters of 31 and 70 inches and a com- mon stroke of 48 inches, with two cy- lindrical double-ended Scotch boilers, each 12 feet in diameter and 16 feet long, containing four plain furnaces of 42 inches diameter. A horizontal steam drum is provided for each boiler. The grate and heating surfaces are, respect- ively, 154 and 5 1 14 square feet.
The speed of the vessel when loaded is about 10 knots, and is from 11 to 12 when light, the I. H. P. varying be- tween 1300 to 1400. Her coal bunker capacity amounts in all to about 2475 tons.
The distilling plant was designed by
nary conditions, that the plant shall be worked on the most economical basis, yet provision has been made in the de- sign for great elasticity. To this end, the piping between the evaporators of each set is so arranged that the three of each group may be worked in triple effect; or, with any one of a set cut out, the remaining two may be worked in double effect; or, so that all may be used in single effect. Moreover, as each of the evaporator coils is divided into two equal nests for convenience in handling, when withdrawn for cleaning or repairs, blank bonnets are provided, so that, in such an event, the half re- maining in place may continue in use.
The shells and heads of the evapor- ators are of steel, y2 inch thick, and designed for a working pressure of 50 pounds. In proportioning the water liberating surface and steam room, suffi- cient was allowed to insure dry steam when working under a vacuum of 24 inches, with an output from each evap-
CROSS VALVE
8 CROSS VALVE
ELEVATION OF ONE GROUP OF EVAPORATORS, SHOWING STEAM PIPING ARRANGED SO THAT EVAPORATORS MAY WORK IN SINGLE, DOUBLE OR TRIPLE EFFECT.
the Bureau of Steam Engineering, Uni- ted States Navy Department, was built by M. T. Davidson, of Brooklyn, N. Y. , and was installed at the Navy Yard at Norfolk, Va. It consists of 1 2 cylin- drical evaporators, alike in all particu- jars, 5 feet, 6 inches in diameter bf 6 feet, 2x/i inches in length, arranged in four groups ot three each. The total daily capacity, when working in triple effect, is calculated to be 60,000 gallons, and for each pound of coal burned in the boilers an approximate output of two gallons of fresh water is expected. While it is contemplated, under ordi-
orator of 4000 gallons, these being ap- proximately the limiting conditions of the low-pressure evaporator in triple effect. One manhole, 11 x 15 inches, and a cleaning hole 6x6 inches, are provided in each shell.
Each evaporator is provided with two manifolds, fitted with straight brass tubes, 2 inches outside diameter, tinned inside and out, No. 13 B. W. G. thick, with a total heating surface of 320 square feet. The tubes are ex- panded into steel tube-sheets, the inner One of which, together with its chest, is free to move in order to provide for
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CASSIER'S MAGAZINE.
expansion. Steam chests and bonnets are oi cast iron, and these parts and the tubes were tested to a pressure of 150 pounds per square inch.
Four condensers, one for each group of evaporators, are a part of the installa- tion. They each contain about 300 square feet of cooling surface in the form of brass tubes, S/% inches outside diameter and No. 18 B. W. G. thick. Sea water is forced through the tubes, and the resulting condensed or distilled water on the outside of the tubes is re- moved and sent to an 8-inch main, with branches to different storage tanks in the hold by 6" x 8" x 10" single-cyl- inder air pumps, situated directly be- neath each condenser.
For circulating sea water through the condensers, two 10" x 14" X 14" single- cylinder pumps are provided, and the
OXE OF THE THIRTY-SIX TANKS PLACED IN THE
FORWARD AND AFTER HOLDS FOR STORING
DISTILLED WATER.
arrangement of piping and valves is such that either pump and any con- denser may be shut off for overhauling without interfering with the operation of the remaining part of the plant. These pumps are also intended for trans- ferring fresh water from the storage
tanks to ships alongside, and either may be used for this purpose while the other is in operation, circulating sea water through the condensers.
When used for discharging fresh water, the suction is taken through a pipe joining the distributing main to the storage tanks, previously men- tioned, and in this suction two valves are placed, back to back, to minimise the chances of salt water mixing with the fresh. The discharge, under these circumstances, leads to a manifold, fitted with proper valves and 2^ -inch hose connections, on the upper deck.
Three feed heaters, having about 50 square feet of heating surface each, are operated in conjunction with the plant, the heating agent being the exhaust steam from the various pumps and the water drained from the evaporator tubes. By this means considerable saving in heat-units results from the temperature of the sea water being raised before en- tering the evaporators to be converted into steam.
It is obviously desirable, in the prac- tical operation of the plant, that steam generated in the boilers, or water re- sulting from the condensation of such steam, should be kept entirely distinct from steam or fresh water produced by the evaporators. This separation pre- sents no difficulty other than an appar- ent complication of piping and valves about the feed heaters. Ordinarily, two of these are employed in raising the temperature of the sea water feeding the evaporators, heat being abstracted for the purpose from the exhaust steam of the different pumps and from the water discharged from the traps drain- ing the tubes of the first, or high-pres- sure, evaporators; in other words, by steam taken in the first instance from the boilers, and which, after condensa- tion, drops through gravity to the feed tank, to be returned to the boilers as feed water.
The remaining heater, which is fitted for the same purpose as mentioned for the other two, utilises as a heating agent the drain water from all evaporators ex- cept the high-pressures. The first- mentioned drains form part of the out-
THE U. S. DISTILLING SHIP "IRIS/
put of distilled water, and, in conse- quence, after transit through the heater, pass to the condensers of the plant. The arrangement of piping, valves, etc. , also permits all exhaust steam, and trap discharges from the high-pressure evap- orator tubes, to be sent directly to the
stalled for this service. By-pass pipes and valves between the suction and dis- charge pipes are fitted, in order that those evaporators under pressure, ex- ceeding atmospheric, may be blown down without other resource.
Salinometer pots are fitted to all
ELEVATION AND LONGITUDINAL SECTION OF ONE OF THE EVAPORATORS.
main condenser, or feed tank, in the engine room.
For supplying sea water to the evap- orators, three single-cylinder pumps, 6" x 4" X 8", are provided, which draw from the overboard delivery pipes of the condensers, and are so arranged that any pump may feed any evapor- ator, either direct or through the feed heaters. Provision is also made by which the evaporators working under a vacuum may be fed by gravity. With the entire plant in operation, however, <it is intended that each pump, feeding through a feed heater, shall supply each group, or lot, of evaporators (high- pressure, intermediate, and low-pres- sure) which work at the same pressure.
As water in the different evaporators becomes concentrated from the continu- ous generation of steam and constant substitution of sea water therefor, con- nections by which the saturation may be reduced after reaching a prescribed limit, are necessary. Two brine pumps, of the same size as the feed pumps, one for each set of six evaporators, are in-
1-6
evaporators for the purpose of ascertain- ing the density of the contained water. Usually, sea water has a density of 1-32, as compared with distilled water; or, in other words, the different salts dissolved amount to about 1-32 by weight, of which nearly 4-5 is common salt. With the plant in operation, the brine pumps serve to maintain the saturation at about 3.5-32 in the low-pressure evaporators, a density which experience has proven should not, as a rule, be exceeded. These pumps may also be used, if de- sirable, to remove water from any of the evaporators.
The tubes of each evaporator are drained by traps, which act automati- cally, as water accumulates from the condensation of the entering steam. Two mains are installed to receive the discharge from these, with valves to direct the flow to either. One main joins the exhaust pipe from the pumps, while the other is led into one of the feed heaters.
In designing the various details of the plant care was observed in so propor-
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CASSIER'S MAGAZINE.
THE STARBOARD SIDE OF THE EVAPORATOR ROOM.
tioning those parts which require re- moval for periodic cleaning that they might be readily handled by ordinary appliances, and without necessitating the breaking of pipe connections. At- tention was also given to accessibility of parts so removed, and facility of re- pair or renewal of any element in case of injury. Special tools, used in assem- bling the different details, are furnished as part of the outfit.
The steam pipes are of such size that the velocity through them does not ex- ceed 7000 feet per minute under maxi- mum conditions of output, and all steam and exhaust piping is seamless drawn, — of copper, where the diameter is of 2 inches or above, and of copper or brass for sizes below. All piping through which distilled water is conveyed, is of iron. Steam and exhaust piping, evap- orators, heaters, etc., are carefully lagged and covered to prevent radia- tion.
In the operation of the plant it is in- tended to maintain boiler pressure, or no pounds, in the first evaporator tubes. The resulting shell pressure, and pressure, consequently, in the tubes of the second, or intermediate evaporator, is to be 30 pounds. This will produce a shell pressure in that
evaporator, and pressure in the tubes of the last evaporator of 16 pounds, steam being finally generated in the low-pressure shell under a vacuum of 24 inches and sent to the condenser. The pressures given are absolute.
Assuming the heat communicated to the sea water, in passing through the feed heaters on its way to the different evaporators, to be sufficient to raise the temperature to 212 degrees, one pound of boiler steam will cause the genera- tion of 0.9 pounds of steam in the shell of the high-pressure evaporator. This produces 0.87 pound of steam in the shell of the intermediate, and the latter, in turn, evaporates 0.88 pound in the shell of the low-pressure. At the ex-