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^
JOURNAL
OF THE
Association it Engineeriog Societies.
Boston. Cleveland. Minneapolis. Louisiana.
Montana. St. Paul. Buffalo. Cincinnati.
Detroit. Pacific Coast. St. Louis.
CONTENTS AND INDEX.
VOLUME XXVI. January to June, 1901.
PUBLISHED BY
THE BOARD OF MANAGERS OF THE ASSOCIATION OF ENGINEERING SOCIETIES.
John C. Tsautwine, Jr., Secretary, 237 S. Fourth Street, Philadelphia. ^ C* O *♦* ' >
4o4do
I
*/
CONTENTS.
VOL. XXVI, January-June, 1901.
For alphabetical index, see page v. No. i. JANUARY.
PAGE
Hydraulic Excavation. Latham Anderson I
Street Lighting of Cities. Henry H. Humphrey 18
Water Power by Direct Air Compression. William O. Webber 35
A Modern American Blast Furnace — Its Construction and Equipment. Arthur
C. Johnston, M. E 47
Obituary. — George W. Percy 59
Association of Engineering Societies 62
Proceedings. Lists of Members of the Associated Societies.
No. 2, FEBRUARY.
Brick and Concrete-Metal Construction. Economy and Strength of Brick and Concrete Arches for Floor Systems of Highway Bridges. William D.
Bullock 73
A Test of the Strength of Rapp Floor Arches. Frederic H. Fay ... 79 Expanded Metal as Used in Fireproof Building Construction and Other
Work. William M. Bailey 84
Description of Ransome System of Concrete Steel Floors. M. C. Tuttle . 93 Tests of Roebling Fireproof Floors. Andrew W. Woodman, C. E . . 100
A Review of Concrete-Metal Construction. Chas. M. Kurtz 108
The Steel Skeleton Construction of a Tall Office Building. J. S. Branne . . 125 The Engineering Society — Its Relations to the Engineer and to the Profession.
H.J. Malochee 149
Proceedings.
No. 3. MARCH.
A Study in Hydraulics. George H. Fenkell 155
Discussion. Messrs. Hazen, Hubbell, Williams, Trautwine and Fenkell 163
Submerged Pipe Crossings of the Metropolitan Water Board. Caleb Mills
Saville 193
Discussion. Messrs. Herschel and Mclnnes 219
iv ASSOCIATION OF ENGINEERING SOCIETIES.
PAGE
Extension of the Group Theory of Atoms and Molecules. Arthur A. Skeeh . 223 Engineering Explorations in Montana and Elsewhere in the Rocky Mountains.
Francis W. Blackford 239
Obituary. — James S. B. Hollinshead 251
Henry M. Claflen 253
Proceedings.
No. 4. APRIL.
Installation, Operation and Economy of Storage Batteries. Ernest Lunn . . 255
Concrete Construction. C. R. Neher 273
Discussion. Messrs. Diehl, Neher, Knighton, Vander Hoek, Tut/on,
Rocktvood and Norton . . . 279
Obituary. — Sherman Emmett Burke 283
Proceedings.
No. 5. MAY.
The Softening of Feed Water for Boilers. Louis Bendit 285
On the Engineering Difficulties Attending a Proper Inspection of Cement.
J. F. Coleman 305
Discussion. L. IV. Brown 311
Early Transportation Canals. J. T. Fanning 315
Proceedings.
No. 6. JUNE.
Subaqueous Tunnels for Gas Conduits. IV. JV. Cummings 327
Discussion. Messrs. Carson, Saville, Shailer and Cummings .... 339 The Increasing Elevation of Floods in the Lower Mississippi River. Linus IV.
Brown 345
Discussion. Messrs. Richardson, Harrod, Hardee, Lewis and Brown . 360
Obituary. — David Walker Hardenbrook 402
Proceedings.
INDEX. VOL. XXVI, January-June, 1901
The six numbers were dated as follows :
No. 1, January. No. 3, March. No. 5, May.
No. 2, February. No. 4, April. No. 6, June.
Abbreviations. — P = Paper ; D = Discussion : I = Illustrated.
. . . " .
Names of authors of papers, etc., are printed in italics.
PAGE
J\ir Compression, Water Power by Direct . William O. Webber.
P., L, Jan., 35
Arches, Rapp Floor , A Test of the Strength of . Frederic H. Fay.
P., I., Feb., 79
Anderson, Latham. Hydraulic Excavation P., I., Jan., 1
Annual Report of the Chairman of the Board of Managers Jan., 65
Annual Report of the Secretary of the Board of Managers Jan., 65
Arches, Economy and Strength of Brick and Concrete for Floor Systems
of Highway Bridges. Wm. D. Bullock P., I., Feb., 73
Articles of Association Jan., 62
Atoms and Molecules, Extension of the Gioup Theory of .
Arthur A. Skeels P., I., March, 223
Bailey, William M. Expanded Metal as Used in Fireproof Building Con- struction and Other Work P., I., Feb., 84
Jjatteries, Storage , Installation, Operation and Economy of .
Ernest Lunn P., I., April, 255
Bendit, Louis. The Softening of Feed Water for Boilers . . .P., I., May, 285 Blackford, Francis W. Engineering Explorations in Montana and Else- where in the Rocky Mountains P., March, 239
Blast Furnace, A Modern American , Its Construction and Equipment.
Arthur C. Johnston P., I., Jan., 47
Boilers, The Softening of Feed Water for . Louis Bendit . P., I., May, 285
Branne, J. S. The Steel Skeleton Construction of a Tall Office Building.
P., I., Feb., 125 Brick and Concrete-Metal Construction.
Economy and Strength of Brick and Concrete Arches for Floor Systems
of Highway Bridges. Wm. D. Bullock P., I., Feb., 73
A Test of the Strength of Rapp Floor Arches. F. H. Fay. P., I., Feb., 79 Expanded Metal as Used in Fireproof Building Construction and Other
Work. William M. Bailey '. . P., I., Feb., 84
Description of Ransome System of Concrete Steel Flotfrs. M. C. Tuttle.
- P., I., Feb., 93 Tests of Roebling Fireproof Floors. Andrew W. Woodman.
P., I., Feb., 100 A Review of Concrete-Metal Construction. C. M. Kurtz. P., I., Feb., 108
(v)
vi ASSOCIATION OF ENGINEERING SOCIETIES.
PAGE
Bridges, Floor Systems of Highway , Economy and Strength of Brick and
Concrete Arches for . Wm. D. Bullock P., I., Feb., 73
Brown, Linus W. The Increasing Elevation of Floods in the Lower Missis- sippi River P. , D., June, 345
Building, The Steel Skeleton Construction of a Tall Office .
J. S. Branne P., I., Feb., 125
Bullock, William D. Economy and Strength of Brick and Concrete Arches
for Floor Systems of Highway Bridges P., I., Feb., 73
Burke, Sherman Emmett . Obituary. Engineers' Club of Cincinnati . April, 283
(^anals, Early Transportation . J. T. Fanning May, 315
Cement, On the Engineering Difficulties Attending a Proper Inspection of .
/. F. Coleman P., D., May, 305
Chairman of Board of Managers, Annual Report of Jan., 65
Claflen, Henry M. . Obituary. Civil Engineers' Club of Cleveland . March, 253
Coleman, J. F. On the Engineering Difficulties Attending a Proper Inspec- tion of Cement P., D., May, 305
Compression, Water Power by Direct Air . William 0. Webber.
P., I., Jan., 35
Concrete Construction. C. R. Neher P., D., I., April, 279
Concrete-Metal Construction, Brick and P., D., I., Feb., 73
Concrete-Metal Construction, A Review of . Charles HI. Kurtz.
P., I., Feb., 108
Conduits, Gas Subaqueous Tunnels for . W. W. Cummings.
P., D. , I., June, 327
Cummings, W. W. Subaqueous Tunnels for Gas Conduits. P., D., I., June, 327
I^arly Transportation Canals. J. T. Fanning P., May, 315
Electric Lighting of City Streets. Henry H Humphrey .... P., I., Jan., 18 Engineering Explorations in Montana and Elsewhere in the Rocky Moun- tains. Francis W. Blackford P., March, 239
Engineering Society, The Its Relations to the Engineer and to the Pro- fession. H.J. Malochee P., Feb., 149
Excavation, Hydraulic . Latham Anderson P., L, Jan., 1
Expanded Metal as Used in Fireproof Building Construction and Other Work.
William M. Bailey P., I., Feb., 84
Extension of the Group Theory of Atoms and Molecules. Arthur A. Skeels.
P., I., March, 223
panning, J. T. Early Transportation Canals P., May, 315
Fay, Frederic II. A Test of the Strength of Rapp Floor Arches. P., I., Feb., 79
Fenkell, George H. A Study in Hydraulics P., D., I , March, 155
Fireproof Building Construction and Other Work. Expanded Metal as Used
in . William 71/. Bailey P., I., Feb., 84
Fireproof Floors. Roebling, Test of . Andrew W. Woodman . P., I., Feb., 100
Floods, The Increasing Elevation of in the Lower Mississippi River.
Linus W. Brown P., D., June, 345
Floor Arches, Rapp A Test of the Strength of Frederic II. Fay.
P., I., Feb., 79 Floor Systems of Highway Bridges. Economy and Strength of Brick and
Concrete Arches for . Wm. D. Bullock P., I., Feb., 73
Floors, Description of Ransome System of Concrete Steel . M. C Tuttle.
P., I., Feb., 93
INDEX. vii
PAGE
Floors, Roebling Fireproof Tests of . Andrew IV. Woodman
P., I., Feb., ioo Furnace, Blast A Modern American , Its Construction and Equip- ment. Arthur C. Johnston P., I., Jan., 47
(jas Conduits, Subaqueous Tunnels for . W. IV. dimming:;.
P., D., I., June, 327
j-j ardenbrook, David Walker . Obituary. Montana Society of Engineers.
June, 402
Hollinshead, James S. B. . Obituary. Montana Society of Engineers.
I., March, 251
Humphrey, Henry H. Street Lighting of Cities P., I., Jan., 18
Hydraulic Excavation. Latham Anderson P., I., Jan., 1
Hydraulics, A Study in . George H. Fenkell . . . . P., D., I., March, 155
Increasing Elevation of Floods in the Lower Mississippi River. Linus W.
Brown P., D., June, 345
Installation, Operation and Economy of Storage Batteries. Ernest Lunn.
P., I., April, 255
J ohnston, Arthur C. A Modern American Blast Furnace — Its Construction
" and Equipment P., I., Jan., 47
}\_urtz, Charles M. A Review of Concrete-Metal Construction. P., L, Feb., 108
Lighting, Street — of Cities. Henry H. Humphrey P., I., Jan., 18
Lunn, Ernest. Installation, Operation and Economy of Storage Batteries.
P., I., April, 255
^[a/oehee, H J. The Engineering Society — Its Relations to the Engineer
and to the Profession P., Feb., 149
Metropolitan Water Board, Submerged Pipe Crossings of the . Caleb Mills
Saville P., D., I., March, 193
Mississippi River, The Increasing Elevation of Floods in the Lower .
Linus W. Broivn P., D., June, 345
Modern American Blast Furnace, A Its Construction and Equipment.
Arthur C. Johnston P., I,, Jan., 47
Molecules, Atoms and , Extension of the Group Theory of . Arthur
A. S/ceels P., I., March, 223
Montana, Engineering Explorations in — — and Elsewhere in the Rocky Moun- tains. Franeis IV. Blackford P., March, 239
j\c'/^r, C. R. Concrete Construction P., D., I., April, 273
(Jbxtuary —
Sherman Emmett Burke, Engineers' Club of Cincinnati .... April, 283
Henry M. Claflen, Civil Engineers' Club of Cleveland .... March, 253
David Walker Hardenbrook, Montana Society of Engineers . . . June, 402
James S. B. Hollinshead, Montana Society of Engineers . .1., March, 251
George W. Percy, Technical Society of the Pacific Coast . . .1., Jan., 59
Office Building, Steel Skeleton Construction of a Tall . J. S. Branne.
P., I., Feb., 125
On the Engineering Difficulties Attending a Proper Inspection of Cement.
J. /*'. Coleman P., D., May, 305
viii ASSOCIATION OF ENGINEERING SOCIETIES.
PPAGE ercy George W. . Obituary. Technical Society of the Pacific Coast.
L, Jan., 59
Pipe Crossings, Submerged -of the Metropolitan Water Board.
Caleb Mills Saville P., D., I., March, 193
Power, Water by Direct Air Compression. William 0. Webber . P., I., Jan., 35
J[\ansome System of Concrete Steel Floors. Description of Jll. C. Tuttle.
P., I., Feb., 93
Rapp Floor Arches. Test of the Strength of . Frederic H. Fay. P., I., Feb., 79
Review of Concrete-Metal Construction. Chas. M. Kurtz . . . P., I., Feb., 108 Rocky Mountains, Engineering Explorations in Montana and Elsewhere in
the . Francis W. Blackford P., March, 239
Roebling Fireproof Floors, Tests of . Andrew W. Woodman . P., I., Feb., 100
^aT'ille, Caleb A/ills. Submerged Pipe Crossings of the Metropolitan Water
Board P., D., I., March, 193
Secretary of Board of Managers, Annual Report of Jan., 65
Skeels, Arthur A. Extension of the Group Theory of Atoms and Molecules.
P., I., March, 223
Softening of Feed Water for Boilers, The . Louis Bendit . . P., I., May, 285
Steel Skeleton Construction of a Tall Office Building. J. S. Branne. P., I., Feb., 125
Storage Batteries, Installation, Operation and Economy of . Ernest Lunn.
P., I., April, 255
Street Lighting of Cities. Henry H. Humphrey P., I., Jan., 18
Study in Hydraulics, A- . George H Fenkell .... P., D., I., March, 155
Subaqueous Tunnels for Gas Conduits. W. W. Cummings . . P., D., I., June, 327 Submerged Pipe Crossings of the Metropolitan Water Board.
Caleb Mills Saville P., D., I., March, 193
J unnels for Gas Conduits, Subaqueous . W. W. Cummings.
P., D., I., June, 327 Tuttle, M. C. Description of Ransome System of Concrete Steel Floors.
P., I., Feb., 93
Water Power by Direct Air Compression. William 0. Webber . P., I., Jan., 35
Water, The Softening of Feed for Boilers. Louis Bendit . . P., I., May, 285
Webber, William 0. Water Power by Direct Air Compression . P., I., Jan., 35
Woodman, Andrew W. Tests of Roebling Fireproof Floors . . P., I., Feb., 100
GEORGE W. PERCY
President, Technical Society of the Pacific Coast.
Editors reprinting articles from this journal are requested to credit not only the Journal, but also the Society before which such articles were read.
As
SOCIATION
OF
Engineering Societies.
Organized 18SI.
Vol. XXVI. JANUARY, 1901. No. i.
This Association is not responsible for the subject-matter contributed by any Society or for the statements or opinions of members of the Societies.
1
HYDRAULIC EXCAVATION.
By Latham Anderson, Member Engineers' Club of Cincinnati.
[Read before the Club, October 18, 1900.*]
The origin of hydraulic mining is recorded as follows by an eminent authority, Mr. Charles Waldeyer, of California, and pub- lished in the report of Dr. Rossiter W. Raymond, United States Commissioner of Mining Statistics, 1873. Page 390 et seq.:
"The origin of hydraulic mining dates back as far as the spring of 1852, . . . when a miner, whose name is forgotten, put up a novel machine on his claim at Yankee Jim, in Placer county, Cal. This machine was very simple. From a small ditch on the hillside, a flume was built towards the ravine, where the mine was opened; the flume gained height above the ground as the ravine was approached, until finally a 'head' or vertical height of 40 feet was reached. At this point the water was dis- charged into a barrel, from the bottom of which depended a hose, about 6 inches in diameter, made of common cowhide, and ending in a tin tube about 4 feet long, the latter tapering down to a final opening or nozzle of I inch.
"This was the first hydraulic apparatus in California. Sim- ple in design, dwarfish in size, yet destined to grow out of its in- significance into a giant powerful enough to remove mountains from their foundations."
Within three decades after the conception of that germ of the giant the topography of two antipodal continents has been profoundly modified, in large areas, by hydraulic mining. In California alone countless millions of cubic yards of detritus, torn from their primordial beds, have been transported from the moun- tains to the ocean, an average "haul" of more than 100 miles, or have been dropped on the way in the main river beds and the Bay of San Francisco. Many miles of the abyssmal canyons of
*Manuscript received December 31, 1900. — Secretary, Ass'n of Eng. Socs.
2 ASSOCIATION OF ENGINEERING SOCIETIES.
the Sierras have been filled a hundred feet and more in depth by the heavier parts of the tailings.
When one is first brought to face these stupendous results, he finds it difficult to accept facts so at variance with previous human experience. But the main facts are incontrovertible, hav- ing been recorded in years of litigation and legislation concern- ing the struggle for existence between the farmers and the miners. For the filling of the river beds with tailings so increased the destructive effects of floods as to damage or ruin whole districts of farming country, and the shoaling up of large areas in the bay had so seriously affected navigation therein that these two inter- ests combined and organized to demand the abolition of hydraulic mining. The outcome was a Waterloo to the great hydraulic mining companies. Nothing could more strongly emphasize the vastness of these deposits and their resulting damages than that verdict of the courts and legislature. It is still further accentu- ated by the fact that these findings and laws were possible in Cali- fornia,— the child of mining, and especially of gravel mining, — which has produced more than three-fourths of all the gold output of the State.
The extent of these mining operations may be further illus- trated by a glance at two of the large hydraulic mines as types of the class, — viz, the North Bloomfield, in Nevada county, Cal., and the Spring Valley, at Cherokee, Butte county. The capital in- vested in the North Bloomfield was $2,500,000. To gain outlet for the tailings into the nearest canyon, a tunnel 7 by 9 feet, 6900 feet long, had to be cut through solid rock. The sluice line was over 2 miles in length and 6 feet wide. The "bank" or auriferous gravel deposit was 400 feet deep and 600 feet wide, the company owning a mile and a half in length of this deposit. A 6-inch g;ant was used under a 500-foot head delivering 32.8 second feet of water and developing nearly 1690 horse power; and a 7-inch nozzle under a 250-foot head, delivering 31.54 second feet and developing about 1560 horse power. From 15,000 to 18,000 cubic yards of gravel were washed away each day of twenty-four hours.
The Spring Valley bank was about 400 feet in height. The bed rock tunnel was much shorter, but to obtain a dumping ground the company had to purchase over 700 acres of valuable farm land. At the time of the writer's visit in 1882, they had buried this land 12 feet deep with tailings, were expecting to add three feet to this depth, and still would be under the necessity of buying more land.
At the Dardenelles Mine 10-inch nozzles, under heavy pres- sure, are said to have been used.
HYDRAULIC EXCAVATION. 3
All the data concerning the three above-named mines are given from memory, the writer not having any records at hand for verification.
It may seem superfluous to rehearse before an audience of engineers so many facts concerning hydraulic excavation, which have become stale history. The only purpose of the recital is to emphasize the strangeness of this strange freak in economic his- tory, that in this century, pre-eminent for discoveries and appli- ances in the mechanical arts, so little has been done towards adopting, in general engineering practice, this most economical of all methods of earth removal. It is still more singular that it has not been generally adopted in the mining of other ores than gold, especially in winning limonite iron from its clay beds on the flanks of hills to which, in the writer's opinion, it is better adapted than even to gold mining.
But this is only in passing, as mining is not within the scope of this paper.
For the purposes of this discussion, there are three different processes employed in hydraulic excavation, — viz:
First. The sluice (sometimes called the "ground-sluice").
Second. The "giant."
Third. The "boom."
Under certain conditions all may be used to advantage by the general practitioner.
The second is, in the opinion of the writer, more generally applicable, and more powerful and economical in the class of works herein contemplated.
The sluice is best adapted to shallow deposits, where the banks would not be high enough to cause danger from caves. It consists simply of a line of boxes laid along the bottom of an open cut through the deposit to be moved. The material is loosened by the pick or plow, and shoveled by hand or dumped from wheelbarrows into the stream running through the boxes, at the lower end of which it is discharged upon the dump. Of course the more copious the supply of water, and the rate of fall in the boxes, the greater their carrying power and the econ- omy of the process.
The boom consists of a temporary dam behind which the water supply is allowed to accumulate till a sufficient amount is stored, when the water is let out in a rush by suddenly opening large flood gates. The wave or torrent thus produced is directed against the foot of the bank to be removed. It is said that the boom has seldom been used outside of Colorado; but its advo-
4 ASSOCIATION OF ENGINEERING SOCIETIES.
cates there claim that it is one of the most economical methods of hydraulic excavation where the supply of water is either very abundant or very scarce.
The writer has had no experience with the hydraulic boom, and only quotes from other writers on the subject.
The following- table is quoted from Van Wagenen's "Manual of Hydraulic Mining" (D. Van Nostrand Company), page 20, to illustrate the comparative efficiency of primitive hand work and the three types of hydraulic mining above enumerated.
The two materials assumed as a basis of comparison are ordinary loose and cemented gravels. Of course only an ap- proximate and general average is attempted in such tables. Ac- cording to the writer's experience, while very soft and friable clay will cut and wash away more rapidly than any gravel, the average compact clay bank will come between the two enumerated gravels in rate of working, being closer to the loose gravel.
TABLE.
ORDINARY. CEMENTED.
By the pan. 1 cu. yd H cu- yd.
" " rocker. 2 "yds 2 " yds.
" " long ton. 5 to 6 " " 3 to 5 " "
" " sluice. 10 to 20 " " 6 to 12 " "
" " hydraulic. 100 to 1000 " " 100 to 1000 " "
" " boom. unlimited. unlimited.
The table shows the number of cubic yards of dirt which may be washed per day of ten hours per man, in the first two cases each man working alone, and in the last four in pairs or econom- ically arranged gangs.
The likelihood that the boom will ever be indicated as a sole means of excavation in general practice is so remote that the device is not worthy of consideration here, but it may, in rare instances, be a useful auxiliary to the giant. It is also frequently beneficial to increase the carrying capacity of an hydraulic sluice line by turning into its head an auxiliary natural stream without head, or from a lower source than that supplying the giant.
Mr. Waldeyer's paper, above quoted, contains a lucid descrip- tion of hydraulic mining, and, notwithstanding the fact that it was written more than a quarter of a century ago, the reader may gain a clear impression of all the essential features of the process which are germane to this discussion.
But a word of caution is demanded here to the reader who consults text-books on hydraulic g-old mining for information as
HYDRAULIC EXCAVATION. 5
to the serviceability of the hydraulic for general purposes. We must keep in mind that the sole aim of the miner is to save gold, and as much gold as possible, consistent, of course, with economy. To this end, it is always necessary to restrict the amount of gravel carried by the boxes in order to increase the yield of gold.
(It goes without saying that all the mere gold-saving im- provements and appliances of the miner are foreign to the topic in hand.) The maximum discharge of the boxes occurs when the velocity of the current is greatest and the water is most charged with mud, but the clearer the water and the slower the current the more readily will the fine gold settle to the bottom of the boxes and be caught by the quicksilver. Hence the necessity of re- stricting the discharge, in order to' increase the amount of gold
saved, and whence it follows that statistics from gold-mining practice must invariably underestimate the capacity of the giant as a labor-saving device.
To recapitulate the conditions essential to economical hy- draulic excavation, they are : the greater the volume of water, the head and the fall in the sluice line, the higher the bank (i.e., the deeper the cut), and the more available the dumping ground, the greater the economy.
As all of these must be self-evident to every engineer, ex- cept possibly that of the height of the bank, we will refer to that at length further on.
It is now in order to outline the process of opening and working an hydraulic mine. From the great storage reservoir in the Sierras, fifty or one hundred miles distant, a ditch conveys the water to the service or distributing reservoir, which is on the nearest hill to the "cut" which will give the required "head" or pres- sure. From the distributing reservoir the water is conveyed to the workings in a riveted sheet iron pipe, in 16-foot lengths, which
6 ASSOCIATION OF ENGINEERING SOCIETIES.
are jointed stovepipe fashion. To the lower end of the pipe line P, Fig. i, is strongly attached the giant. A longitudinal section of one of the smaller sizes is shown in Fig. I. This con- sists of a pipe about 9 feet long, attached at its lower end to a cast iron globular casing or jacket G\ inclosing the minor globe G. Attached to the outer surface of G are the trunnions T, whose horizontal axis passes through the center of the spherical surfaces G and G1. The trunnions pass outwardly through col- lars in the casing G1. This arrangement permits ample upward and downward movement of the pipe. The outer end of the pipe is provided with a screw joint, so that nozzles N of different aperture may be attached. There is a horizontal joint J between the lower extension of the globe, called the "goose neck" (GN), and the heavy bedplate BP. Of course all joints and bolt holes
Fig. 2
|
S |
S |
|||
|
Sin |
Sin |
|||
|
1 • 1 |
•1 , — + |
|||
|
Sin, |
1 • 8 |
• | |
Sin |
|
|
* |
must be packed water-tight. (The joint J is tightened by the rod R passing down through the goose neck and bedplate.) Hori- zontal and vertical motion may be imparted to the pipe, simul- taneously, if desired, by the lever L, a piece of scantling attached, at its front end E, to the pipe by the collar strap C, and to the fulcrum F by the collar C1 and the pin P3.
The plan of the bed frame is shown in Fig. 2, in which S.S. are the bed sills and Sm,Sm are the mud sills. Nailed to the top of the lever is a shallow wooden box W, which is weighted down with loose stones so as just to counterbalance the downward reaction of the water upon the pipe. It is apparent that this machine is so simple as to be readily set up, managed and kept in order by any workman of average intelligence. But, like many other simple machines (billiard cues, for instance), there are widely differing degrees of skill displayed by different prac- titioners. This is so pre-eminently true with regard to the giant
HYDRAULIC EXCAVATION. 7
as to make the pipeman the essential and most important em- ploye on the works after the installation is complete. In fact, the degree of economical success or failure of the enterprise is gaged by his skill. It lies in him to make or mar the business. It is, therefore, a sheer waste of money to put such a plant in the hands of a novice or of an unskillful pipeman. Quick percep- tion, nerve, intelligence and good judgment all go to make up the ideal pipeman or bank foreman. (In small plants the two offices are usually combined.)
THE NOZZLE.
The nozzle N requires further notice. Upon the perfection of its shape and condition the cutting efficiency of the stream mainly depends. The cutting power of a stream of given volume and nozzle velocity is in the ratio of its solidity at the point of impact. Strictly speaking, a column or shower of spray 'has no
|
Fig. 3 |
Fig. 4: a |
|
fr {. \ ,i |
V «•: J |
|
Sec. on ab Fig. ■& |
r A * — h Sec. on v d Fig. S |
cutting power; it merely washes. But a solid stream with a noz- zle velocity of say 90 feet (due to a head of 150 feet) pierces a bank like a projectile or bores like an auger. It surprises the novice to see what refinements of precaution are requisite to in- sure such solidity of stream.
First. Xo entrained air should be permitted to pass the nozzle.
Second. The bore of the latter should be of correct shape ("ajutage"), and, in the cylindrical part, should be as true and smooth as a gun barrel. Because iron soon becomes roughened by rust, hard gun metal is a better material for nozzles.
Third. Rifles or radial plates r, r, Figs. 3 and 4, should be inserted in the pipe to prevent the rotary motion otherwise bound to occur, which whirling motion of the column would de- stroy its cylindrical shape and solidity.
THE SLUICE LINE.
In gold mining, the boxes, Figs. 5 and 6, must be of planed, tongued and grooved lumber, so as to be perfectly water-tight, since the smallest leak would cause the loss of fine gold and
8 ASSOCIATION OF ENGINEERING SOCIETIES.
amalgam, and they must have costly bottom paving. But, for our purposes, any tolerably tight boxes of cheap, undressed lum- ber will answer. And here is our first advantage in point of economy over the gold miner. A further gain is in avoiding (usually) the costly bottom paving of the gold miner, no lining being required for small operations, say of 20,000 or 30,000 yards, while for larger ones 1 or i|-inch plank bottom linings would usually be sufficient on moderate grades. The upper end of the boxes should be provided with flaring wings of temporary sheet piling.
Near the head of the upper box is placed an inclined grating, with spaces of such size as to arrest all stones too large to be car- ried freely by the current in the boxes. The rejected stones are forked over in a pile to one side of the line of boxes by a man sta- tioned at the grating for that purpose. If required, these piles of stones may be carried or run out of the cut on a tramway as
j 1 ■ 1 1 i_
Fig. 5. Elevation of Upper End.
the work proceeds. The giant is set up a little to one side of the sluice head.
Everything is now in position to begin the cut. Fig. 7 shows in plan the relative positions of the sluice head S, the giant G and the initial point P. T.T. is the tramway for removing the piles of refuse R (including boulders, stumps, roots of trees, etc.). The stream from the giant is turned upon the point P. A cavity is rapidly formed in the base of the hill and a mixture of water, mud and stones pours down into the boxes. When the face of the cut approaches the limit of the giant's cutting efficiency, the work is stopped. The giant is taken up, a new joint or joints of pipe are added, and the giant set up in its new position. Espe- cial care is demanded in securing the bed frame of the giant firmly in the ground. Small, sharp gravel or firm soil should be rammed hard around the mud sills, and the frame should be strongly braced against forward or lateral motion, because a very slight movement of the giant would loosen some of the joints in the pipe line.
HYDRAULIC EXCAVATION. 9
The sluice head is carried forward at the same time with the giant, by adding boxes at the upper end.
When the bank attains a height of 15 or 20 feet, it is usually in a shape to begin the first cave. The foot of the bank is under- cut several feet in height, forming a cave, or a series of caves with intervening pillars. When the caves are knocked into one by cutting out the pillars, the overhanging mass trembles, splits off on the plane of the back of the cave, and plunges into the cut with a momentum that shatters the mass. Now, the higher the bank the larger will be the amount of overhanging earth brought down by a given amount of undercut, whence the econ- omy of high banks becomes apparent. Take the case of a bank like that at North Bloom-field, 400 feet high. Suppose the cut is 40 yards long, 2 yards deep and 10 feet high. The amount of un- dercut would be about 260 yards, and the amount caved down
&13 X 4 l£j 3x4 1 X C
Strip
Fig. 6. Section of Elevation on Line a b, Fig. 5.
would be over 10,000 tons. But such high banks are usually so dangerous that it is preferred to work them in two stages, as they were doing at North Bloomfield on the occasion of the writer's visit. But operations on such a scale would rarely, if ever, be demanded in engineering work. In railroad cuts of from 40 to 100 feet, for instance, it is not likely that more than from 2 to 4 second feet of water under 150 feet head (2 to 3-inch nozzles) would ever be required. In most cases, especially on high sum- mits, the water would have to be delivered by steam power.
To recapitulate, in point of economy our practice is inferior to the great hydraulic mining plants in the following particulars :
First. In volume of water.
Second. (Usually) in amount of head or pressure.
Third. (Probably in most localities) in not having a natural or gravity supply and pressure.
But, on the other hand, we have the following advantages over any and every mining plant:
io ASSOCIATION OF ENGINEERING SOCIETIES.
First. We may use cheaper boxes and sluice line.
Second. We avoid the expense of all the costly gold-saving devices and appliances, — e.g., costly bottom paving in the sluice line, undercurrents, box-riffles, retort house and the loss of at least four days' time each month in "cleaning up" (collecting amalgam) and in repairing sluice line.
Third. We save the interest and sinking fund on the capital invested in the huge dam and reservoir, and in the scores of miles of main ditch.
Fig. 7.
Fourth. The outlay, in railroad work especially, will be much smaller for giants, pipe line, tools and machinery for the cut than in mining.
As a deduction from the foregoing premises, we conclude that, under certain conditions, a great saving may be effected in the cost of the above indicated classes of engineering work by the use of hydraulic excavation, especially with the nozzle.
That this conclusion may not be relegated to the domain of abstract argument, your attention is called to the following recent
HYDRAULIC EXCAVATION. n
instances of the successful application of hydraulic cutting and filling in general engineering practice.
We will begin with extracts from "Reservoirs for Irriga- tion," by James D. Schuyler, Member American Society of Civil Engineers (United States Geological Survey Report, 1896-97, Part IV).
HYDRAULIC DAM CONSTRUCTION.
La Mesa Dam, San Diego, Flume county, Cal., for the pur- pose of storing the flood water of San Diego River, etc. "The dam was designed and constructed by J. M. Howells, C.E., Presi- dent of the San Diego Flume Company. . . . It is an earth and rock-fill dam, 66 feet high and 20 feet wide on top, the ma- terials for which were transported and deposited in place by flowing water, by the process known to miners as 'ground-sluic- ing,' the surplus water from the flume being used for this pur- pose, and at the same time being stored in the reservoir as it was being formed back of the dam (page 649). The volume of ma- terial handled was 38,000 cubic yards, which had to be brought an extreme distance of 2200 feet, and stripped from an area of ir| acres to a mean depth of 2 feet. Had the material been favor- able in depth and character, it is thought the entire dam could have been finished for 25 or 30 per cent, of its ultimate cost, which was about $17,000. Instead of sluice boxes, the material was conveyed for the last 2000 feet in 24-inch wooden stave pipes lined with strips of steel to resist wear. Cost, 90 cents per foot. (Page 650.)
PROPOSED PINE VALLEY DAM, SAN DIEGO, FLUME COUNTY.
(Page 653.) Dam to be 130 feet high, 30 feet wide on top. The water to be used for sluicing will have to be pumped to a height of 400 feet, in order to reach the deposits of material available for sluicing, but the engineer estimates that even this high lift is feasible and profitable, and he expects to increase the duty of water used from 5 per cent, of solids conveyed (the maximum ac- complished at La Mesa Dam) to about 20 per cent, of solids, or 13 cubic yards per miner's inch of twenty-four hours (0.02 cubic foot per second). "If this duty can be maintained, and the cost of pumping be assumed at a maximum of 5 cents per 1000 gallons, the cost per yard for water will be about 5 cents, with but little additional cost for loosening (with pick), as the material is soft." (Please note that if giants were used no additional cost for loosen- ing would be incurred.)
12 ASSOCIATION OF ENGINEERING SOCIETIES.
PROPOSED LAKE HELENA DAM, SAN DIEGO RIVER.
(Page 654.) The proposed dam is 1100 feet long on top, 190 feet at base, 155 feet high, 25 feet wide on top, bottom thickness of 650 feet and to contain 789,000 cubic yards. "This site is considered favorable for hydraulic construction because of the abundance of material on both sides and the possibility of using water under high pressure to loosen the material by powerful jets from hydraulic mining giants.
DAM AT TYLER, TEXAS.
(Page 654.)
This dam, constructed in 1894, has the following features: Length 575 feet, height 32 feet, and contains 24,000 cubic yards. This impounds 1770 acre feet and covers 177 acres.
The water was pumped through a 6-inch pipe from the old city pumping station. This hill is 150 feet high and the pipe terminated halfway from its base, where a common fire hydrant was placed, to which was attached an ordinary 2^-inch hose with a i|-inch nozzle. The cost, including the plant and all the appurte- nances of the reservoir, was 4! cents per yard.
The following additional facts throw further light upon the secret of this remarkable result:
"The stream was directed against the face of the hill under a pressure limited to 100 pounds per square inch. The washing was carried rapidly into the hill on a 3 per cent, grade, which soon gave a working face of 10 feet or more, increasing gradually to 36 feet in vertical height. By maintaining the jet at the foot of the cliff it was undermined as rapidly as it could be broken up and carried away by the water."
SAN LEANDRO AND TEMESCAL DAMS, CALIFORNIA.
(Page 655.)
These furnish part of the supply of the city of Oakland, hav- ing 60,000 inhabitants. They were constructed by their princi- pal owner, Mr. A. Chabot, who had been a practical hydraulic miner.
The Temescal Dam was built in 1868. The work was con- tinued a number of seasons by collecting storm water from time to time. The dam is 105 feet high and 18 feet wide on top, cover- ing only 18.5 acres, with a capacity of 188,000,000 gallons.
The San Leandro Dam was built in 1874-75, and has a height of 120 feet above the stream bed. Total volume of dam is 542,-
HYDRAULIC EXCAVATION. 13
700 yards, of which 160,000 yards were deposited by the hydraulic process. The water was brought four miles in a; ditch, and the sluiced materials were conveyed in a flume lined with sheet iron plates, laid on a grade of 4 to 6 per cent. The water used was 10 to 15 second feet, and the ground-sluicing method was alone employed ; nevertheless the cost was estimated at one-fourth to one- fifth that of putting the earth in place by carts or scrapers.
HYDRAULIC FILLS ON THE CANADIAN PACIFIC RAILWAY.
(Page 657.)
At trestle No. 374, North Bend, in Frazer River Canyon, there is required to fill the chasm an embankment 231 feet in ex- treme height and containing 148,000 cubic yards. The plant con- sisted of 1450 feet of sheet steel pipe 15 inches in diameter, 1200 feet of sluice boxes or flume 3 feet wide and 3 feet deep; one No. 3 "giant" monitor with 5-inch nozzle, and a large derrick driven by a Pelton water wheel. Piping head 125 feet. The sluice boxes were laid on grades from 11 to 25 per cent., partly sup- ported on high trestles. The boxes were paved with wood blocks on the lighter grades and old railway rails on the heaviest. Fifty per cent, of the pit consisted of cemented gravel, 30 per cent, of loose gravel and 20 per cent, of large boulders which had to be removed by the derrick. Nevertheless, the entire cost of the work, including the plant, was $5089, or at the rate of 7.24 cents per yard (and including explosives used on the cemented gravel). "Had the pressure of the water been greater (400 to 500 feet head) and the gravel loose, the duty of the water would have been in- creased four- fold."
The entire force employed consisted of eight men, all com- mon laborers except the pipeman. The water used was ap- proximately 20 second feet or 1000 miner's inches, the duty per- formed being 1.77 yards per twenty-four-hour inch. At the cross- ing of Chapman's Creek the railway company, in 1894, made a similar fill of 66,000 yards at a total cost of 7.5 cents per yard, of which 3.2 cents was for plant. The actual work of sluicing cost bat 1.78 (one and seventy-eight hundredths) cents per yard.
HYDRAULIC FILLS ON THE NORTHERN PACIFIC RAILWAY.
(Page 659.) Work of a precisely similar nature has been in progress for a number of years past on the line of the Northern Pacific Rail- way, where several high and dangerous trestles have been re- placed by hydraulic-made embankments of earth, gravel and loose
i4 ASSOCIATION OF ENGINEERING SOCIETIES.
rock. During 1897, nine high trestles, requiring from 6200 to 108,500 cubic yards. Of this amount 377,000 cubic yards in eight of the trestles were moved and put in place at an average cost of 4.79 cents per cubic yard. The detail of the cost is given below:
Sluicing and building side levees 3.85 cents.
Hay used in levees 09
Tools 08
Lumber and nails 22
Labor building flumes 44
Engineering and superintendence 11
Total 4-79
"In all the above work the water was carried to the borrow pits and the sluicing done by gravity. In one case, however, pumping was resorted to, and 42,250 cubic yards were moved by water thus lifted, at an average cost of 13.5 cents per cubic yard."
"The plant required is rather inexpensive. According to locality, one nozzle would require from 300 to 1000 feet of light sheet iron pipe costing 27! cents a foot and a No. 2 giant costing $95. Outside of this nothing is required except picks, shovels, hoes and axes. From five to six men are required with each nozzle to build the levee, build sluice boxes and do everything else required."
THE DRAINAGE OF THE OKEFINOKEE SWAMP, GEORGIA.
In the "Engineering Society Annual of the University of Georgia," Vol. I, 1893, page 12, there is an article entitled "Hy- draulic Excavation," by B. M. Hall, C.M.E., formerly a professor in the Georgia University. From this valuable paper we make the following extracts:
"Notwithstanding the fact that hydraulic gold mining has been in progress for so many years on the Pacific slope and in the State of Georgia, engineers seem slow to adopt this cheap plan of excavation for other work, such as railroads, canals, etc., even when the conditions necessary to successful operation are all present and in plain view.
"These conditions are:
"1. Material that is soft enough to be loosened and washed away by water.
"2. A sufficient volume of water at an elevation above the proposed cut.
"3. Sufficient grade, away from the bottom of the cut, for giving the water enough velocity to take away the material.
HYDRAULIC EXCAVATION. 15
. . . Where booming is resorted to, for getting soft material out of the way, the cost is often as low as one cent per cubic yard. . . .
"The most important work of this nature that we know of is being done in Charlton county, Ga., by the Suwanee Canal Com- pany, in excavating the outlet canal for the drainage of Oke- finokee Swamp. That swamp, situated in Charlton, Clinch, Ware and Pierce counties, is a shallow fresh water lake, covering an area of 400,000 acres and filled with black muck. . . .
"The Suwanee Canal Company purchased the greater part of this land from the State of Georgia, and about 100,000 acres from individuals. The object of their undertaking is:
Summit JEl. 148.00
/ \Preliminary Cut
L—^—X El. 131.00
P \
El. of Swamps / <\
11G.00 / -\
Fig. 8. Drainage of Okefinokee Swamp, Georgia. Hor. Scale i Mile to 1 Inch. Ver. Scale.
"1. To cut and place on the market this vast store of valua- ble timber, and,
"2. To thoroughly drain the lands for cultivation.
"A profile of the swamp and proposed drainage is shown by Fig. 8.
"In making plans for drainage, the first thing necessary was to provide a sufficient outlet by cutting a deep canal through the dividing ridge. It is here that the method of hydraulic excava- tion is being used on a grand scale and in a highly interesting manner. First, a narrow, shallow canal was cut across the ridge with teams and scrapers as in railroading. Its depth was about 17 feet at the summit, and it ran to nothing at e.ach end, as its bottom was level across the ridge. ... At the eastern mar-
16 ASSOCIATION OF ENGINEERING SOCIETIES.
gin of the swamp a pumping plant, consisting of two 8o-horse- power boilers and two 14-inch centrifugal pumps, lifts 30,000 gal- lons of water per minute into a flume, producing an immense stream, which runs into and through the canal. At the eastern end of this preliminary cut, where the slope toward the mine is steep, the water began to do its work. A deep and wide canal is being carried rapidly back toward the swamp."
A "porcupine" harrow, made of a round log filled with har- row teeth, is dragged up and down the canal by steam power, a distance of 1000 feet. The excavated material is dumped into a lateral ravine of such storage capacity that nothing but clear water drains into the St. Mary's River. The average cost of ex- cavation on the outlet canal is 2\ cents per cubic yard.
HYDRAULIC EXCAVATION AT SEATTLE.
The Seattle and Lake Washington Navigation Company is opening navigable tidal' channels by dredging and the reclamation of tide lands adjacent to the business center of Seattle, Wash- ington, by filling with the fine black sand dredged from the chan- nels. Two powerful dredges are used, each with a capacity of 600 to 700 cubic yards per twenty-four hours, which is pumped from the bottom of the channel through 18-inch pipes, a distance of 2000 to 4000 feet, and deposited to a depth of 18 to 20 feet over the area to be reclaimed. Some 36,000,000 cubic yards are to be handled in this way, and 1500 acres filled in solidly to a height of 2 feet above tide. About 1,000,000 yards had been put in place January 1, 1897, the cost of which was 16 cents per yard by con- tract.
In conclusion, the writer desires to call the attention of the Club to what he considers a rare opening for an extensive and profitable hydraulic cut and fill in Cincinnati. The whole of Mill Creek bottom, between Hopkins street and Harrison avenue and between the Cincinnati, Hamilton and Dayton and the Baltimore and Ohio Railroads, could be filled in by piping down the north- ern end of Mt. Harrison, to a level, say, ranging from 70 to 90 feet above datum. In the writer's opinion, little, if any, explosive would be required, provided not less than 20 second feet of water were used and under a head of not less than 250 feet. The water would be pumped from the river at the mouth of Mill Creek into a temporary reservoir on top of the ridge south of Liberty street. The reservoir need be only large enough to perform the function of a standpipe in maintaining an even pressure. A vertical cut of at least 200 feet could soon be established, when, by taking
HYDRAULIC EXCAVATION. 17
advantage of soft layers at the base in undercutting, immense masses might be caved down. After the caves the softer parts and finer stone could easily be piped away, leaving the larger merchantable stone to accumulate on the floor of the cut, per- fectly clean. Assuming that the stone averaged 20 per cent, of the bank, and that it is worth on the ground 40 cents per cubic yard, the stone would pay 8 cents per cubic yard of bank toward the cost of excavation. On this basis the writer esti- mated, some years since, that the work could be done at 15 cents per yard net, provided not less than 3,000,000 cubic yards were moved.
[2]
18 ASSOCIATION OF ENGINEERING SOCIETIES.
STREET LIGHTING OF CITIES.
By Henry H. Humphrey, Member of the Engineers' Club of St. Louis.
[Read before the Club, November 21, 1900.*]
The proper lighting of streets in our modern cities cannot be overestimated. Their illumination is scarcely secondary in importance to the maintenance of grades and paving. When the streets are neglected until their surfaces have become uneven and unsafe, the necessity of illumination is heightened.
It is evident to any one at all observant that the recent developments in street illumination are in the direction of a uni- form and diffused light, rather than along the well-beaten path of previous years which gave brilliantly lighted crossings and Egyptian darkness in the middles of the blocks. The develop- ment of the inclosed arc lamp and the growth of mantle gas lighting are illustrations of this point.
Some cities still cling to the old-style open arc lamp; nota- bly the city of Chicago, which is still making all its increase with this type of lamp, and the city of Denver, Col., which is at present installing a new city lighting plant using open arcs for all but one of the circuits. It is reported, however, that this feature of this contract may be changed before the plant is completed and in- closed arc lamps installed throughout the city.
The question of the candle power of the lamp itself is one of importance, but is evidently not a "paramount issue." The old- style direct-current series open arc lamp is without doubt superior in actual candle power to any of the later types of inclosed lamps. Nevertheless, it is giving place very rapidly to inclosed arc lamps of either the direct current or alternating current type. Devel- opment along the lines of electrical progress is not always made in the interest of the public, or of the users of light. Many sys- tems, improvements, etc., are developed by the manufacturing companies for the sole purpose of making an increased market for their goods. This development in arc lamps, however, pass- ing from the open lamp to the inclosed lamp, is one that directly benefits the public and the user of light. Admitting that the candle power is considerably less, for the same expenditure of energy in the lamp, the light is so much easier on the eyes in the immediate neighborhood of the lamp, and the illumination is so much more uniform, that the result is far superior.
A comparison of candle powers between the direct-current open arc, the alternating-current inclosed arc and the direct-cur-
^Manuscript received December 10, 1900. — Secretary, Ass'n of Eng. Socs.
STREET LIGHTING OF CITIES.
19
rent inclosed arc lamps, is somewhat uncertain, owing to the dif- ferent methods employed by different observers and to the differ- ent standards of light used. In fact, the result of candle-power measurements of arc lamps has been so uncertain that very few authoritative data upon this subject have been published.
In Fig. 1 a series of curves, prepared by Mr. H. H. Wait, of Chicago, and presented to the Northwestern Electric Associa- tion, is reproduced here by his permission.
OO 8o°
I— D. C.
II— D. C. Ill— D. C. IV— D. C. V— A. C.
Fig. 1.
Open arc.
Inclosed arc, clear inner globe.
" alabaster inner globe, with reflector.
" " opal inner globe, without reflector.
No. 1 represents the direct-current open arc lamp.
No. 2, the direct-current inclosed arc lamp with clear inner globe.
No. 3, the direct-current inclosed arc lamp with alabaster inner globe and with reflector.
No. 4, the alternating-current inclosed arc lamp, with ala- baster inner globe and with reflector.
so ASSOCIATION OF ENGINEERING SOCIETIES.
No. 5, the alternating-current inclosed arc lamp, with opal inner globe and without reflector.
These curves show very decidedly the sacrifice of maximum illumination, in one direction, in order to secure a more uniform distribution of light and a better average illumination.
It is almost universally conceded that the direct-current in- closed arc lamp produces more light per watt than the inclosed alternating-current arc lamp, but the exact ratio between them has not, to my knowledge, been determined. The best data that I am able to find are the tests made by Prof. C. P. Mathews, of Purdue University, under the direction of the Committee on Arc-Light Photometry of the National Electric Light Associa- tion. His tests are based on constant-potential lamps, instead of upon series lamps, and his watt measurements are taken across the lamp terminals instead of across the arc only. He has tested 8 direct-current inclosed arc lamps and 7 alternating-current in- closed lamps, made by different manufacturers. The average difference in candle power between the direct-current lamps and the alternating-current lamps is 30 per cent., the average differ- ence in watts consumed at the terminals of the lamp is 27 per cent.; the difference in watts at the arc is I2-| per cent.
Taking one particular case, comparing the performance of a direct-current 558-watt lamp, with no outer globe and no shade, with a 418-watt alternating-current lamp, with shade, gives a . difference of 39 per cent, in light in favor of the direct-current lamp at an expenditure of 23 per cent, more power in watts. There is apparently but slight difference between the efficiencies of these lamps when the watts across the terminals are consid- ered.
His data also give the watts at the arc in each of these lamps. The average watts used by the D. C. lamps are 529, of which 384 are available in the arc, and 144 or 27 per cent, are wasted in the dead resistance and in the mechanism of the lamp. The aver- age watts used by the A. C. lamp are 417, of which 342 are avail- able in the arc and 74.5 or 18 per cent, are wasted in the mechan- ism. If we reduce the results obtained, to the basis of light pro- duced by watts in the arc, we find that the difference in candle power with the same expenditure of energy in the arc is approxi- mately 16 per cent, in favor of the direct-current lamp. The average current for the direct-current lamps was 4.90 and for the alternating-current lamps 6.29.
Fig. 2 shows two curves from his data for 450 watts-in-the-arc arc lamps. In this figure, curves 1 and 2 are for the direct-
STREET LIGHTING OF CITIES. 21
current lamps; curves 3 and 4 are for the alternating-current lamps. These are approximations only, since the candle power of the lamp varies greatly with different makes of carbons and with different current densities in the arc. These curves can be con- sidered as approximating closely the conditions in series inclosed lamps, since in this type of lamp only 3 per cent, of the energy is used in the mechanism of the lamp.
300
200
100
100
200
300
The company which recently secured the electric lighting contract in St. Louis for the next ten years proposed, at the time of the award, to build a new power house and plant complete, equipped for commercial lighting as well' as for public lighting. Many of the contracts for machinery were awarded and actually signed, when the sale of the stock of the company to local in- terests changed entirely the scheme and development of the plant. Believing that the engineering details in connection with this work may have some general interest, I will describe briefly the
22 ASSOCIATION OF ENGINEERING SOCIETIES.
principal engineering features connected with the new electric lighting system in this city.
The general design of this plant, as installed, was outlined in the report of the engineers of the Imperial Electric Light, Heat and Power Company, under date of September 3, 1897, as follows:
"In an enterprise of this magnitude it seems to us advisable to bear in mind the possibility of doing the city lighting from this same plant. For a steady load, such as all-night street lighting, when the generators can be worked to their full capacity during their entire run, there is no apparatus that surpasses the direct- current machine and series direct-current arc lamp. The new series inclosed 150-hour arc lamp is being put upon the market now and the reports that we have from it are entirely satisfactory. Large direct-current multiple-circuit series arc lighting genera- tors can now be obtained, suitable for direct connection to en- gines, and give a large and efficient unit without the necessity of excessively high voltage. We believe that this type of generator would fulfill the requirements of city lighting better than any alternating current or constant potential direct-current apparatus would do."
Anticipating the city lighting contract, the company installed one extra duct throughout its entire underground system, and a trunk line of ten extra ducts north and south to the limits of the underground district for the purpose of arc lighting. This fore- sight has made it possible for the present contractors for city lighting to install their work in the underground district within the time available, an accomplishment that would have been im- possible for any company having to install an entirely new system of conduits.
The question of type of apparatus, whether to use the direct- current series inclosed arc lamp, or its formidable rival, the alter- nating series inclosed arc lamp, was promptly decided by the adoption of the former. The comparative difference in candle power of the two lamps, with the same consumption of energy, was unquestioned, and, since the city lighting contract calls for an expenditure of 480 watts at the arc, leaving the question of candle power entirely out of consideration, it was the desire of the company to give the public the benefit of the 16 per cent, in- crease in light.
Advocates of the alternating-current system claim that they can deliver more light from alternating-current lamps, operated from large constant-potential alternating-current generators,
STREET LIGHTING OF CITIES.
23
than can be obtained from the use of direct-current apparatus. While this is an open question, and one dependent almost entirely upon the economy of the steam-generating and steam-using ap- paratus in the station, it did not enter seriously into the con- sideration of design of plant under the existing conditions. The Imperial plant was already in operation, with a direct-current system that had proved its efficiency and adaptability to the ser- vice intended; and the city lighting load, consisting of hut 525 K. W., was too small a factor to affect seriously the design of
Fig. 3. Motor-Driven Arc Dynamos.
the entire plant. It is admitted that driving these arc dynamos by means of compound condensing engines would be more effi- cient, from coal to watts-at-arc, than the present motor-driven units which, as shown below, give an efficiency of transformation of 80-J per cent. About one-third of this. 19^ per cent, loss is probably in the motor, and could have been saved by driving direct from the engine. It is believed, however, that the practical advantages to be obtained from a plant of this design, where a multiplication of small units is avoided, where one man can oper- ate the entire station, and where each large unit in the Imperial plant is a reserve unit for the city lighting work, are so great that
24 ASSOCIATION OF ENGINEERING SOCIETIES.
they overbalance the saving in coal obtained by placing the prime movers directly connected to the arc machines.
The arc lighting plant consists of 12 no-light Western Elec- tric series arc .dynamos, built upon their standard 125-light frames, and each machine guaranteed capable of operating no 500-watt series inclosed arc lamps through 40 miles of No. 8 B. & S. circuit. Each two arc machines are driven by a 200 horse-power direct-current 500-volt motor, the three comprising a self-contained unit, five of which are capable of operating the present city lights, leaving one unit as reserve. These machines
Fig. 4. 500- Volt Switchboard.
are located at present in a temporary building adjoining the Im- perial plant on the east side and located on the south side of St. Charles street, just west of Ninth street. In the design of the complete plant these arc generators will be on the second floor of the building, leaving the entire ground space available for boilers, engines and 500-volt direct-connected generators. .Fig. 3 shows these machines.
Fig. 4 shows the 500-volt constant-potential switchboard, with switch, starting box, ampere meter, etc., for each motor- driven unit. The center of the board contains an "illuminated- scale Weston 500-volt volt meter, showing the potential upon the
STREET LIGHTING OF CITIES.
25
bus bars at all times. Inclosed fuses for each circuit are placed on the rear of the board.
Fig. 5 shows the arc board, containing 12 dynamo circuits and 12 outside circuits. The terminals are widely separated, the positive being at the top of the board and the negative at the
Fig. 5. Arc Lighting Switchboard.
bottom. Each circuit contains a combination Weston ampere meter and polarity indicator. There is a transfer bus across the middle of the board, so that a dynamo at one end of the board can be connected to a circuit at the other end without stretching long connecting cables across the front of the board. The center
26 ASSOCIATION OF ENGINEERING SOCIETIES.
of the board contains a Weston 10,000-volt volt meter with termi- nal plugs. There is also a plug for ground connection, and two plugs for 500-volt connection used for testing circuit during the day. At the rear and above the board can be seen the static ar- resters which will be mentioned later.
The arc machines are of the ironclad, Gramme Ring arma- ture, bipolar type, each equipped with the well-known Western Electric regulator. A special lightning arrester is placed upon the pole of the machine in such a manner that the stray mag- netism from the pole piece blows out the arc when a discharge takes place.
The motors are 6-pole ironclad machines, and operate at a speed of approximately 675 revolutions per minute. Each motor has a special field rheostat, by which the speed can be regulated through a range sufficient to provide for the variation in voltage due to commercial load on the station bus bars supplying the motors.
There are three circuits in the underground district, each containing approximately 105 lamps. These are supplied through No. 8 B. & S. lead-covered cables, manufactured by the Standard Underground Cable Company, having 6-32 inch rubber and 3-32 inch lead. The cables are drawn into the ducts in continuous lengths, from the base of the iron arc lamp pole on one corner to the base of the iron arc lamp pole on the next corner, thus avoid- ing all joints, either inside the ducts or in the manholes. The district north of the underground district is supplied by four overhead circuits, each containing approximately 90 lamps. They are carried through the underground district to its limit at Ninth and Wash streets, by means of a 12-conductor lead-covered cable, the 12 wires being placed in one cable and surrounded by a lead sheath % inch in thickness. This cable provides for four extra wires for increase of plant or for use in case of trouble on any one conductor.
The district south of the underground is supplied by three circuits of approximately 90 lamps each, carried to the limit of the underground district at Seventh and Spruce streets through a similar 12-conductor cable.
For the overhead circuits triple-braided weather-proof wire is used, supported on double-petticoat glass insulator.
The lamps are suspended at the corners of street intersec- tions by means of iron arc lamp poles. The interior of the pole, as shown in Fig. 6, contains a hoisting windlass and pulleys for raising or lowering the lamp. The figure also shows the method
STREET LIGHTING OF CITIES.
27
of insulating the wires where they leave the iron pole and swing up to the lamp. The lead-covered cable is brought from the manhole, or service box in the street, through an iron pipe lateral, both cables of the circuit being placed in the same 2^-inch iron pipe. In the base of the lamp they end in special hard rubber
Fig. 6.
terminals, placed over the end of the lead sheaths and filled with paraffine to prevent any possibility of moisture entering the cable. From this special terminal a rubber-covered duplex cable, con- sisting of 2 No. 12 B. & S. flexible wires surrounded by 7-64 inch of rubber and the two conductors braided together, extends up
28 ASSOCIATION OF ENGINEERING SOCIETIES.
through the pole. This cable passes out through the special porcelain insulator and up to the lamp, being supported above the lamp upon a porcelain knob spreader and connected to a solid wire which enters the binding post of the lamp, providing a solid and secure connection at the binding post. These solid wires are bared for a short distance at a point midway between the porcelain knob and the binding post of the lamp, providing a space where a specially constructed "jumper" can be readily attached whenever it may become necessary for a lamp to be changed while the circuit is in operation. The linemen carry in- sulated stools upon which they stand while handling the live cir- cuits.
The use of a switch in the base of these poles, by which the lamp could be cut out of circuit entirely while a lineman is work- ing upon it, would be very desirable, and such a switch was in- stalled before the plant was put into operation. It took a very short experience, however, with these switches, which were the best the market afforded, to convince all connected with the en- terprise that they were a failure in the position in which they were placed. Being convinced that it would be impossible to de- sign a practical switch which would occupy the limited space available in the base of these poles and still be safely operative upon 8000 volt circuits, they were abandoned entirely and the solid connection was made as above described.
The use of iron poles for the suspension of arc lamps was a condition of the city contract, which left the engineers no option. The use of special terminals and the cable above described in the underground district, and the use of special triple-petticoat glass insulators on the poles on the overhead circuits, will, we believe, render the circuits safe from anything but the ordinary mechanical accidents incident to any class of apparatus placed upon the streets of a city.
As intimated above, some trouble, due to the static discharge from the underground cables, was encountered. This was not unanticipated; but it was believed that drawing both cables through the same iron duct, where they enter the base of the iron arc lamp pole, would provide a sufficient connection between the two, so that the lead sheaths would be practically connected together throughout the entire circuit. At the plant all of the six cables of the three circuits were drawn into the same duct of the conduit and with the same object in view. It was ascertained, however, soon after starting the plant, that these contacts were not sufficient. The static effect from the cables manifested itself
STREET LIGHTING OF CITIES.
29
in the short-circuiting of arc lamps through the insulation at the top of the inclosing globe, where the full difference of potential of the lamp is effective. The lead sheaths of all the cables were securely soldered together in the manholes where they enter the lateral which goes into the lamp poles. They were also con- nected securely together at the plant just behind the switchboard. These efforts had little, if any, beneficial effect upon the opera- tion of the circuits. In addition to this, a special static dis- charger, shown diagrammatically in Fig. 7, consisting of an ordi- nary Leyden jar condenser, was connected to the copper of each circuit at the rear of the switchboard in the plant. Each con- denser is provided with a revolving contact arm, driven by a small motor which alternately connects the condenser to positive wire,
Fig. 7. Static Discharger.
to ground, to negative wire and to ground, thus receiving a charge from the line and discharging it to ground about 30 times per minute. After this apparatus was installed the static effect of the cables has so entirely disappeared that it is not appreciable in the operation of the plant.
The city contract includes 739 32 candle-power incandescent lamps, located in the alleys throughout the electric-lighted dis- trict. These are all supplied from the regular 3-wire 235-470 volt mains of the Imperial Company, requiring, therefore, no special apparatus. It might be of interest, however, to show a special switch designed for switching these circuits in and out by means of the arc lighting current. This switch, which was designed by Mr. E. P. Warner, of Chicago, is shown in Fig. 8. When the arc current is turned on it operates upon the solenoid, which, act- ing through the lever, closes a 3-wire 500-volt switch, switching on
30
ASSOCIATION OF ENGINEERING SOCIETIES.
the alley incandescent lights throughout the district controlled by this particular switch. When the arc circuit is shut down in the morning the plunger of the solenoid is released, and, in fall- ing, it opens the switch, cutting the incandescent lights out of circuit. This simple arrangement saves the services of a man, with horse and wagon, to go around and start the incandescent lights, saving also the loss of current in switching lamps on ahead
Fig. 8. 500- Volt Switch Electrically Controlled by Arc Circuit.
of time where a considerable district must be covered and all the lamps in the district started not later than the schedule time.
In Table A are shown the data obtained under test of one of the motor-driven arc-light units, the test continuing from 12 o'clock midnight until the closing-down time in the morning. The first column gives the time; the second, third and fourth columns the amperes and voltage supplied to the direct-current motor, also the rise in temperature of the motor fields during the time of test. The fifth, sixth and seventh columns give the am- peres, voltage and field temperature of one of the arc dynamos;
STREET LIGHTING OF CITIES.
31
column eight and nine, the amperes and voltage of the other arc dynamo. Column ten gives the speed of the unit, column eleven, the temperature of the air in the room, and column twelve the efficiency, being the ratio of the electrical input to the electrical output of the unit. You will observe that each reading gives two
TABLE A. Test of Motor-Driven Arc Unit.
|
Motor. |
No. 7 Arc Dynamo. |
No. 8 Arc Dynamo. |
Speed. |
Air Temp. F°. |
Effi- |
|||||
|
Time. |
Amp. Volts. |
Field Temp. F°. |
Amp. |
Volts. |
Field Temp. |
Amp. |
Volts. |
ciency. |
||
|
I2-IO |
325 1 49° 300 482 |
140 |
7.0 6.7 |
8580 8125 |
128 |
7.0 68 |
9346 8850 |
675 |
108 no |
78.6 |
|
12-30 |
330 487 302 480 |
147 |
7.0 6.8 |
8791 8325 |
130 |
7-i 6.9 |
9346 8850 |
677 |
109 114 |
79.O |
|
1-00 |
325 497 305 488 |
154 |
7.0 6.8 |
9425 8925 |
135 |
6.9 6.7 |
9610 9100 |
676 |
109 114 |
82.5 |
|
1-30 |
340 505 320 493 |
*57 |
7.0 6.9 |
9610 9100 |
140 |
7.0 69 |
9979 9450 |
676 |
108 no |
79-8 |
|
2-00 |
325 512 303 502 |
158 |
7.0 9610 6.8 9100 |
142 |
7.0 6.8 |
9504 9000 |
700 |
107 109 |
80.4 |
|
|
2-30 |
320 500 300 490 |
160 |
6.9 9346 6.8 8850 |
144 |
7.2 7.0 |
9187 8700 |
701 |
109 112 |
81.0 |
|
|
3-00 |
330 500 310 490 |
162 |
7.0 9504 6.8 9000 [ |
147 |
7-i 6.9 |
9557 9050 |
695 |
I08 I07 |
80 9 |
|
|
3-30 |
327 505 305 495 |
162 |
7.0 9400 6.9 8900 |
148 |
7.0 6.8 |
9504 9000 |
700 |
no 116 |
80.0 |
|
|
4-00 |
325 507 305 498 |
154 |
7.0 9504 6.9 9000 |
151 |
7.0 6.8 |
9610 9100 |
720 |
107 107 |
81.2 |
|
|
4-30 |
327 515 305 504 |
153 |
7.o 9557 6.9 9050 |
152 |
7.0 6.8 |
9820 9300 |
715 |
109 115 |
80.5 |
|
|
5-00 |
320 515 300 503 ! |
150 |
7.0 9900 6-9 9375 |
152 |
7.0 6.8 |
9504 9000 |
730 |
no 117 |
82.4 |
|
|
5-50 |
323 520 305 5°7 |
148 |
7-0 9451 6.9 8950 |
148 |
7.0 6.8 |
9583 9075 |
100 no |
79-3 |
||
|
Average efficienc |
■ |
80.5 |
figures, the first figure in each case being that of the standard test instruments, while the second reading is that of the regular station switchboard instruments. The test instruments read uni- formly higher than the station instruments. They were carefully compared with recently calibrated instruments, and they are be- lieved to be correct. The total capacity called for in each of
32
ASSOCIATION OF ENGINEERING SOCIETIES.
these arc machines, as given above, is 1 10-500 watt arc lamps each through 40 miles of No. 8 B. & S. wire. This is equivalent to a total voltage of 8750 volts at 7 amperes. The test shows that the machines ran above their rated load during the entire test, the load on one reaching as high as 9979 volts, which is 15 per cent, above the rating.
The guaranteed efficiency of the unit was 78^ per cent. The average efficiency during test was 8of per cent., reaching, in one case, as high as 82^ per cent, and in another 82.4 per cent. The machines came well within their guarantees regarding rise in tem- perature of all of their conductors. It will be noted that the temperature of the motor fields reached its maximum at 3 a.m.. and from that time steadily decreased, although the work being done by the motor increased slightly during the test. This de- crease in temperature is probably due to a slight increase in the speed of the unit following the high voltage at the bus bars. The voltage readings of the arc circuits show but slight increase dur- ing the night, after the number of lamps in circuit was allowed to remain constant. This increase of voltage is more noticeable on another type of lamp shown in the next table.
TABLE B. Test of High-Voltage Arc Circuits.
|
Time. |
No. 2 Circuit. |
No. 1 Circuit. |
||
|
Amperes. |
Volts. |
Amperes. |
Volts. |
|
|
6-36 |
65 |
59OO |
6-5 |
7000 |
|
7-0O |
6-5 |
6400 |
6.6 |
7300 |
|
7-35 |
6.5 |
6900 |
% 6.5 |
6500 |
|
8-00 |
6-5 |
7200 |
6.6 |
6900 |
|
8-30 |
6.5 |
7450 |
6.5 |
7400 |
|
9--OO |
6.5 |
7700 |
6-5 |
7900 |
|
9-30 |
6-5 |
7650 |
6-5 |
8350 |
|
IO-OO |
6-5 |
7700 |
6-5 |
8550 |
|
IO-30 |
6.5 |
7450 |
6.5 |
8600 |
|
II-OO |
6.5 |
7350 |
6-5 |
8750 |
|
II-40 |
6-5 |
7I50 |
6.4 |
*6500 |
|
I2-00 |
6-5 |
7I50 |
6-5 |
6900 |
|
I2-IO |
6-5 |
7100 |
6-5 |
6950 |
♦Machine flashed just before reading was taken.
STREET LIGHTING OF CITIES.
33
Table B gives data obtained from a test of another high- voltage plant in a neighboring city; column one gives the time, columns two and three give the amperes and voltage upon one
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Fig a.
Load Ci rvi Oct 1895
10 In 12 S 4 S 8 10 U.S. 12
s. Showing Original Hypothetical Curve and Present Actual Curve with the U?i of Baiterv Also Load Curve Nov. (900 5howinc City Liohtibc Load
Fig. 9.
circuit and columns four and five the amperes and voltage on the other circuit. These were both overhead circuits. The former contained 92 lamps and the latter no. This last circuit had 5 lamps more than either of the circuits shown in the last table. 3
34 ASSOCIATION OF ENGINEERING SOCIETIES.
These lamps, an hour after they had been put in operation, used but 64 volts per lamp, including the loss in the line. After they had been in operation for about five hours, however, the voltage per lamp had increased to 68 volts and 78 volts, respectively, for the two circuits, the lower voltage per lamp of one circuit being accounted for by a number of newly-trimmed lamps upon that circuit. This characteristic of an arc lamp is a serious drawback for street lighting, inasmuch as the lights show dim during the first part of the night, when people are upon the street and the light is needed, and show up much brighter during the latter half of the night when the streets are practically deserted, and when the light is not so essential.
In a paper read before this Club last year I showed the load carve of the Imperial plant, which I will reproduce in Fig. 9. I repeat it here for the purpose of showing what a small effect the city lighting load has upon the total load of the plant. The lower line gives the preliminary load curve, prepared by the engineers before the plant was built and submitted in their preliminary re- port covering the design of the plant. The second line gives the load upon the plant one year after it had started, and a year and one month ago. It illustrated the use of the battery at that time, and attention was called to the large all-night load, the com- paratively low peak or maximum load and the high average for the entire twenty-four hours, which is 39.27 per cent, of the maxi- mum. A year ago the peak of the load was 5600 amperes. The third or highest curve gives the present load-curve of the plant, showing the changed use of the battery, which is no longer able to carry the night load and allow the shutting down of the plant. It is still available for doing its full load capacity at the peak of the load, and its use as a balancer and equalizer of pressure is the same as it was a year ago. The increase in the all-night load is only partly due to city lighting, the city lighting load being only about half of the present total all-night load. The dotted curve shows the load on the plant exclusive of city arc lighting.
The station at present shows a maximum load of over 13,000 amperes, which is more than twice the maximum of thirteen months ago, which was 5600 amperes. The average load for the twenty-four hours has increased from 2198 amperes to its present amount of 6345 amperes, approximately three times as much as that of a year ago, and greater than the maximum load on the plant at that time. The load-factor of the plant has increased from 39.27 per cent, to 47.7 per cent., giving a load-factor that can be equaled by few, if by any, plants in this country.
WATER POWER BY DIRECT AIR COMPRESSION. 35
WATER POWER BY DIRECT AIR COMPRESSION.
By William 0. Webber, Member Boston Society of Civil Engineers.
[Read before the Society, November 21, 1900.*]
The use of compressed air for power purposes and as a means for the transmission of power is much older than is usually conceded. It was used by Smeaton in 1786, by Medhurst in 1810, by Rennie in 1812, by Vallance in 1818, at the Triger mines of Challones in 1845, by Cubitt in sinking the piers of the Rochester bridge in 185 1. Brunei also made a similar use of it at Saltash in 1854. It was also used by Brunei on the Thames Tunnel, by Barlow on the Thames Subway and in the shaft of the Marie Col- liery in 1856.
Air has been transmitted for considerable distances and under a great range of pressures. At the Mont Cenis Tunnel, air was transmitted to the boring machinery 20,000 feet under a pressure of 105 pounds per square inch. In the installation at Paris, in 1881, by M. Popp, the length of the pipes slightly exceeded twenty-four miles. This plant, as well as the one installed by the same person in Vienna in 1877, was originally used for the running and regu- lating of clocks, but it afterward developed into power for work- ing small motors. In Paris the main is a steel pipe 20 inches in diameter, and the air, maintained at 90 pounds pressure, transmits 6000 horse power.
At a large compressed-air plant at Offenbach, near Frank- fort-on-the-Main, air is distributed through 25,000 feet of cast iron pipe under 90 pounds pressure. At the Portsmouth Dock Yards, England, air is transmitted through 14,000 feet of pipe, varying from 3 to 12 inches diameter, under 60 pounds pressure, and is used to drive forty 7-ton capstans, five 20-ton cranes and machinery for working seven caissons.
There is also a large compressed-air plant at the Terni Steel Works in Central Italy. In this plant 1,200,000 cubic feet of air per day, under 75 pounds pressure, are used to drive a 100-ton hammer, a 100 and 150-ton crane and numerous engines.
In this country 2,500,000 cubic feet of air per day, at 60 pounds pressure, delivering 1700 horse power, are used at the Chapin mines in Michigan. The mains in this plant are 24-inch wrought iron pipes, one-quarter inch thick. Very successful compressed-air tramways have been operated for a number of years at Berne, Switzerland, and at Nantes, France.
*Manuscript received December 31, 1900. — Secretary, Ass'n of Eng. Socs.
36 ASSOCIATION OF ENGINEERING SOCIETIES.
Mekarski used compressed air for driving tramway cars in
1877.
In all of the above-named uses of compressed air, the com- pression was produced by steam-actuated mechanical compressors. The older ones were all simple compressors, Mekarski being the first to use compound compressors, and he was followed in this line by Northcote in 1878.
The adaptability of compressed air for various uses is very great. While electricity supplies power and light very directly, it cannot be used for heating except at a prohibitive cost. Gas is used very directly to supply heat, power and light, but is expensive for heating and power at the prices generally charged. City water pressure can be used to supply power, and indirectly light, by the use of a water motor driving a dynamo, but is too expensive for most purposes. Steam supplies heat and motive power almost directly, and indirectly light through a dynamo. It is, however, more expensive than compressed air, and involves more risk and attention. Compressed air can be used directly as a source of motive power, ventilation and refrigeration ; also in the operation of elevators.
We have already mentioned its use in connection with power hammers, cranes and motors. For drying purposes it is even more efficient than heat. Compressed air is also largely suscepti- ble to double uses. For instance, after it has been used cold, or without pre-heating expansively in a motor to produce power, the exhaust furnishes an efficient and cheap method of producing re- frigeration. When pre-heated and then used through a motor the exhaust is still hot enough to contribute considerably to the heating of a building.
In the transmission of compressed air over long distances, the loss of pressure due to friction in pipes of proper sizes, and the loss due to leakage in properly constructed pipes and joints, are very small. Velocities of from 30 to 50 feet per second are allowable. When an air distribution system is introduced into a thickly settled community, the safety from the air main is much greater than from a steam main or a water main under pressure, and a leakage or even the bursting of such a pipe is attended with very much less damage.
Another great advantage in such a case is that power users require no new plant, and need incur no outlay for motors. Their present steam engines, with little or no alteration, are admirably adapted for serving as air motors.
Tests of small motors of from one to two horse power, using air at the ordinary atmospheric temperature and at 735 pounds per
WATER POWER BY DIRECT AIR COMPRESSION. 37
square inch absolute, exhausting at from 330 to 54°, required a consumption of 1200 cubic feet of air per brake horse power per hour. At the Berne tramway the air is compressed to 450 pounds per square inch. On the average the cars use about 35 pounds of air per car-mile. This, however, was used in connection with hot water. In small motors of from one to two horse power, with the air pre-heated to a temperature of about 1580 and exhausting at about the freezing point or 320, 850 cubic feet of air per brake horse power per hour were used.
In some very carefully conducted trials made by Professor Riedler, using an 80 horse power engine which was actually giving 72 indicated horse power, using air at 80 pounds pressure, heated to 3200, with' cylinders jacketed with hot air and exhausting at about 950, about 425 cubic feet of air per brake horse power per hour were used. This showed an efficiency of about 92 per cent.
Practically all that has been said above refers to air compressed by the old methods of mechanical compression. We now come to the subject of air being compressed directly by falling water or under pressure. Air compressed by the ordinary methods of mechanical compression contains at least the same amount of moisture as the surrounding atmosphere from which it was com- pressed ; and, in parting with the heat necessarily contributed to the air by the mechanical compression, it is inclined to absorb more moisture. There is incidentally a considerable loss of energy in parting with this heat. Air compressed directly by falling water is kept at the same temperature as this water. It is compressed isothermally, and the consequent expansion, when used in motors, produces an almost truly adiabatic expansion line. Tests, however, have shown that air compressed in this manner contains only one- sixth of the moisture originally in the surrounding atmosphere from which it is compressed. This is probably because the moisture in the bubble of air is pressed or squeezed out to its surface and then absorbed by the surrounding water. Incidentally there is no loss of power in parting with any heat, and there is a practical result which is of more importance, — the hydraulically compressed air can be expanded down to a temperature much below the freezing point, while atmospheric air, with the usual amount of moisture, mechanically compressed, cannot be used at all, owing to the freezing up of the exhaust passages of the motor in which the attempt to use it is being made.
During some tests made at Magog in September, 1899, owing to the conditions under which these tests wyere made, the change in the humidity in the air was not so great as above stated. The
38 ASSOCIATION OF ENGINEERING SOCIETIES.
moisture in the external air showed 90 per cent, of saturation, and, after compression, 29 per cent., or a little more than one quarter. In the Magog tests, using an old 75 horse power Corliss engine, with air at 53^ pounds gage pressure, with cold air direct from the compressor at from 66° to 730, and exhausting down to the ex- tremely low point of 42° below zero, 850 cubic feet of air per brake horse power per hour were used ; and, with the air pre-heated to from 2050 to 2950 Farenheit, and exhausting at from 670 to 68°, 620 cubic feet of air per brake horse power per hour were used.
Probably one of the oldest applications of the use of water power to the wants of man was a form of hydraulic air compressor which operated as an entrainment apparatus. This was the well- known water bellows or trompe of the Catalan forges.
This apparatus, briefly described, consisted of a bamboo pole, disposed at a slight inclination from the perpendicular, into the upper end of which a stream of water was led, entraining air with it in its downward passage. The lower end of this bamboo pole was introduced into a bag made of the skin of some animal, the air be- ing allowed to escape from the water into the upper part of the bag, whence it was led by pipes or tuyeres to the forge, the water being allowed to escape from the lower edge of the bag. From this original device a great many improvements have been worked out, and besides this a number of other forms of hydraulic air compressors, or of compressors using other liquids for com- pressing air or other gases, have been designed.
Siemens invented an apparatus on the principle of the steam injector, but the use of this was confined principally to the produc- tion of a vacuum. It is used to operate the pneumatic dispatch tubes in London. It has also been used for blast purposes in Siemens's furnaces and in sugar works.
Another quite ingenious device, Fig. 1, shown in a patent granted to W. L. Home, consists of two flat plates, A and B, in- closing between them an air space from which a pipe leads to the atmosphere. The upper plate A is perforated with conical holes, the smaller end of each hole being adjacent to the air space between the two plates. Directly opposite the apertures of the upper plate A are corresponding conical apertures in the lower plate B, with the smaller end of the aperture next the air-space, the lower and larger part of the conical openings being prolonged by tubes C C. The upper plate is kept under a head of water, and the water jet, passing across the thin air space referred to, draws in the air through the large air pipe D, and compresses it through the smaller orifices.
WATER POWER BY DIRECT AIR COMPRESSION.
39
Another device, using a somewhat similar principle, was in- vented by M. Romilly. It consists of a conical tube attached to an air reservoir by its larger end, and having a check valve interposed in the passage so as to prevent the air from escaping. Water is then injected into the smaller end of this conical tube through an ajutage which gives it the form of a liquid vein at a given pressure. This vein entrains the air with it and causes it to be compressed in the reservoir.
Fig. i. W. L. Horne.
But all of the apparatus just described did not really employ the same methods as those used in the old trompe. One of the first inventions carrying out this idea, Fig. 2, was made by Mr. J. P. Frizell, of Boston, Mass., a member of this Society. His inven- tion made use of an inverted siphon having a considerable hori- zontal run D between the two legs A and B. A stream of water was led into the upper end of the longer leg A, and at the top of the horizontal run D between the two legs of the siphon was pro- vided an enlarged chamber C in which the air separated from the water. The water was then led off from the lower part of this air chamber and passed off through the short leg B of the siphon, the pressure of the air accumulated in the air chamber being there-
40
ASSOCIATION OF ENGINEERING SOCIETIES.
fore due to the height of water maintained in the shorter leg of the siphon. This application of carrying upward the water, after the air was separated from it, so as to produce a considerable pressure upon the air, seems to have been original with Mr. Frizell, and in this feature his device differs from the old trompe. Mr. Frizell made two working models of this type of apparatus. In the first the legs of the siphon were 3 inches in diameter, the head of water being 25 inches, and an efficiency of 26^ per cent. was obtained. A larger apparatus was then constructed at the Falls of St. Anthony, on the Mississippi River, a few miles above
Fig. 2. J. P. Frizell.
St. Paul. The longer leg of the siphon in this plant was 15 inches by 30 inches and the short leg of the siphon 24 inches by 48 inches in section. The height of water above the air chamber was 29 feet. The head in feet varied from 0.98 to 5.2, the first head being just sufficient to cause a flow through the pipes The working head varied from 2.54 feet to 5.02 feet and the efficiency from 40.4 per cent, to 50.7 per cent., the quantity of water in these cases varying from 5.92 to 11.89 cubic feet per second.
From his experiments Mr. Frizell estimates that with a shaft 10 feet in diameter, a depth of 120 feet and a fall of 15 feet the ef- ficiency would be 76 per cent., and that with a head of 30 feet and a fall of 230 feet the efficiency would be 81 per cent.
WATER POWER BY DIRECT AIR COMPRESSION.
41
Another device, Fig. 3, differing somewhat from that of Mr. Frizell, was invented by A. Baloche and A. Krahnass in 1885, and consisted of a siphon B carrying water from an upper to a lower reservoir, the lower end of the siphon being projected through an inverted vessel R placed nearly at the bottom of the second reser- voir. Just beyond the bend of the siphon, and in line with the vertical axis of its longer leg, an air pipe T projected into the descending leg of the siphon, thus entraining the air with the de-
Fig. 3. A. Baloche and A. Krahnass.
scending column, which carried it down into the inverted chamber R, from which the air escaped at the top, while the water passed out from the bottom into the lower reservoir. This apparatus produced pressure on the air in the top of the inverted chamber, due to the height of the water column upon it.
Another device, Fig. 4, patented by Thomas Arthur in 1888, differs from the last in having a stream of water led directly into the top of the vertical pipe A. Inserted into the mouth of this pipe was a double cylindrical cone C forming an annular air passage between it and the walls of pipe A.
42
ASSOCIATION OF ENGINEERING SOCIETIES.
Owing to the increase in the velocity of the water in passing through the narrow throat of the double cone, air is inhaled through the pipe D through the annular space mentioned and through per- forations in the lower cone, and is entrained with the falling water.
Through the down-flow pipe A rises a vertical delivery pipe Z for the compressed air, having its lower end H enlarged and open at the bottom. Projecting upward into this enlarged air-delivery pipe was a water-escape pipe F through which the water passed after having parted with the air. This escape pipe was in the form
Water II! J Water Air \Jff
Fig. 4. T. Arthur.
of an inverted siphon and maintained on the air in the delivery pipe Z a pressure due to the elevation of the water at its discharge point above the air line in the large end of the delivery pipe.
A number of other patents on apparatus of this type were issued to Charles H. Taylor, Nos. 543,410, 543,411, 543,412, July 23> J895- His inventions, Fig. 5, consisted principally of a down- flow passage having an enlarged chamber at the bottom and an enlarged tank at the top. A series of small air pipes projected into the mouth of the water inlet from the large chamber at the upper end of the vertically descending passage, so as to cause a number of small jets of air to be entrained by the water, Taylor
WATER POWER BY DIRECT AIR COMPRESSION. 43
44 ASSOCIATION OF ENGINEERING SOCIETIES.
seemingly having been the first to introduce the plan of dividing the air inlets into a multiplicity of smaller apertures evenly dis- tributed over the area of the water inlet.
Taylor at first seems to have attempted to utilize centrifugal action in causing the separation of the air from the water in the larger chamber at the bottom of the compressed column; but he afterward abandoned this scheme and used, instead, deflector plates in combination with a gradually enlarging section of the lower end of the down-flow column in order to decrease the velocity of the air and water and cause partial separation to take place. The deflector plates changed the direction of flow of the water. This was evidently intended to facilitate the escape of the air.
The latter improvements on this device have been in the method of introducing the air into the mouth of the downwardly flowing water column, so as to insure the largest proportion of air being taken down with the water, and in methods of decreasing the velocity of the combined air and water at the bottom of the descend- ing column, causing the water to part more readily with the air, the water then passing out at the bottom of the enlarged chamber into an ascending shaft, maintaining upon the air a pressure due to the height of water in the uptake, the air being led off from the top of the enlarged chamber by means of a pipe.
The first of these compressors on the Taylor principle was in- stalled at Magog, Quebec, to furnish power for the print works of the Dominion Cotton Mills Company. The head of water is 22 feet; the down-flow pipe is 44 inches in diameter, and extends downward through a vertical shaft 10 square feet in cross section and 128 feet deep. At the bottom of the shaft the compressor pipe enters a large tank, 17 feet in diameter and 10 feet high, which is known as the air chamber and separator.
A series of very careful tests on this plant demonstrated that with 19.5 feet head, using 4292 cubic feet of water per minute, was recovered the equivalent of 1148 cubic feet of free air per minute, which would represent 248 cubic feet of air per minute compressed to 53.3 pounds pressure, showing that out of a gross water horse power of 1 58. 1, 1 1 1.7 horse power of effective work in compressing air was accomplished, giving therefore an efficiency of 71 per cent.
In the tests at Magog we recovered 81 horse power, using an old Corliss Engine without any changes in the valve gear as a motor; this would represent a total efficiency of work, recovered from the falling water, of 51.2 per cent.
WATER POWER BY DIRECT AIR COMPRESSION.
45
When the compressed air was pre-heated to 2670 F. before being used in the engine, in horse power was recovered, using 115 pounds coke per hour, which would equal about 23 horse power. The efficiency of work recovered from the falling water and the fuel burned would be, therefore, about 61^ per cent. On the basis of Professor Riedler's experiments, requiring only 425 cubic feet of air per brake horse power per hour, when pre- heated to 3000 F. and used in a hot-air jacketed cylinder, the total efficiency secured would have been about 87^ per cent.
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The second compressor on the Taylor principle is located on Coffee Creek, to the south of Ainsworth, British Columbia. The Available head of water is 107.5 ^eet- The down-flow pipe is 33 inches in diameter. The shaft is 32 square feet area and 210 feet deep. The maximum volume of water is 4200 cubic feet per minute and would represent, at 71 per cent, efficiency, 587 horse power. This compressor is expected to utilize about 5100 cubic feet of free air per minute or 734 cubic feet of compressed air at 87 pounds pressure, and give an air motor horse power of 360 horse power.
46 ASSOCIATION OF ENGINEERING SOCIETIES.
It is possible, however, that this plant may not give as high per- centages as this, as the water passages are of smaller areas than those at Magog.
Three other plants are now under construction, — one at Peter- borough, Ontario ; one at Norwich, Conn., and one in the Cascade Range, State of Washington. The plant at Peterborough, Ontario, for the Government of the Dominion of Canada, is to be used in connection with one of the locks on the Trent Valley Canal, the chief dimensions being as follows : Head of water, 14 feet ; gage pressure, 25 pounds; diameter of compressor pipe, 18 inches; diameter of shaft, 42 inches ; depth below tailrace, 64 feet.
The whole plant is inclosed in the masonry wall of the lock, the usual rock chamber in the bottom of the shaft being built in concrete and only a few feet below the lower water level of the lock. At Norwich, Conn., at what is known as the Tunnel Privilege on the Quinebaug River, the plant will give 1365 H. P. of air at a pressure of 85 pounds per square inch. The head of water is 18^ feet; diameter of shaft, 24 feet; diameter of compressor pipe, 13 feet ; depth of the shaft, 208 feet.
The air will be transmitted a distance of four miles with a loss in transmission not exceeding 2 per cent., through 16-inch pipe, which will be laid with flanged joints and rubber gaskets.
The plant which is being constructed in one of the canyons of the Cascade Range of mountains in the State of Washington will give 200 H. P. of air at a pressure of 85 pounds per square inch. Head of water, 45 feet.
There is no shaft, as the apparatus is constructed against the vertical walls of the canyon. The diameter of the compressor pipe is 3 feet. The diameter of the up-flow pipe is 4 feet 9^ inches. The capacity of the plant is based on 2000 miners' inches of water, equal to 53.2 cubic feet per second. The total height of this apparatus is about 260 feet.
Besides what is now known as the Taylor type of compressor, some forms of hydraulic ram compressors were designed by Som- meiler and also by Mr. H. D. Pearsall. These operated in a nearly similar manner to the hydraulic ram and gave an efficiency of 80 per cent.
A MODERN AMERICAN BLAST FURNACE. 47
A MODERN AMERICAN BLAST FURNACE— ITS CON- STRUCTION AND EQUIPMENT.*
By Arthur C. Johnston, M.E., Member of the Civil Engineers' Club of
Cleveland.
[Read before the Club, November 27, iooo.f]
In an article written in 1896, entitled "Forty Years of Progress in the Pig Iron Industry," John Birkinbine says : "A retrospect of four decades will show that this interval covers most of the advances in the production of pig iron made in the United States, and also those introduced in European countries, for, although the use of mineral fuel, the application of heated blast and the employ- ment of steam blowing machinery were not uncommon features of smelting plants, the increased production of pig iron up to 1855 was due chiefly to an augmented number of blast furnaces and enlarged dimensions of stacks. But what was considered at that time a large furnace would now rank as small, while the quantity of metal obtained in a year from the greatest producers of forty years ago was equaled by the monthly output of a number of modern fur- naces in 1895."
The relative proportions of representative furnaces, from 1855 to 1900, are well shown in Fig. 1.
Much has been written about the increasing size and output of furnaces generally, but, on account of the rapidity of development, very little concerning their actual construction and the means em- ployed for bringing about the increased production. The object of this paper is to describe the mechanical construction of a modern furnace, its equipment and the appliances for concentrating and handling the enormous amount of material that is required to make 600 tons of iron per twenty- four hours in a single stack; and to
*Note. — Owing to the keen competition of commercial interests in the iron and steel industry in this country, great care has been taken to eliminate from this paper anything that would seriously affect the interests of the company owning the furnaces herein described. It is on this account that the paper is confined to a description — from the standpoint of a blast furnace engineer — of the mechanical construction of a complete modern furnace plant, the object being to show thereby the great advances that have been made in blast furnace construction and equipment during the last ten years, and to give an adequate idea of the enormous oossibilities of the American iron and steel industry, which has at its command such producers as these. The subjects of ore and coke supply, the burdening and grades of ore used, the fuel consumption and the extent and cost of output have been carefully avoided, otherwise the paper could have been made much more interesting and valuable.
fManuscript received December 8, 1900. — Secretary, Ass'n of Eng. Socs.
48
ASSOCIATION OF ENGINEERING SOCIETIES.
draw some conclusions based on the operation of such a furnace, taking as a concrete example the plant of the Lorain Steel Company, at Lorain, Ohio. It is regretted that it will not be possible, within the limits of this paper, to introduce other furnaces for the sake of comparison, but it is hoped that the record of experience in the operation of the Lorain furnaces — two of the largest in the world — will be of value in the design of perhaps still greater iron producers. The plant mentioned was built in 1899, and consists of two stacks, each 100 feet high from hearth level to furnace platform,
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22 feet in diameter at the bosh and 14 feet at the hearth. By refer- ence to Figs. 2, 3 and 4 it will be seen that they are arranged on the American system, which places two furnaces in a group, there being four heating stoves for each furnace and a boiler house and engine house common to both. The plant is arranged to be capable of extension by adding to the engine and boiler houses, making them of sufficient capacity for another similar group of two fur- naces. Sections showing the lines and construction of the furnaces themselves are shown in Figs. 5 and 6. It will be seen that there is a slight difference between the lines of furnace No. 1 and those of No. 2.
The distinctive feature of these furnaces is the great depth of the hearth jacket, and the low level to which the furnace columns
A MODERN AMERICAN BLAST FURNACE. 49
are carried in consequence. The hearth jacket itself is also of novel design. It consists of two series of segmental steel castings, held together by bolts and buckstays, with rust joints at the abutting edges of the different segments. Between the jacket and the masonry there is inclosed a complete ring of individual vertical pipes, intended to serve the double purpose of a cooling system and a means of relieving the jacket of excessive bursting strains, due to the expansion of the contained furnace bottom, by the partial collapse of the pipes. The intention was to have the cooling water for the jacket discharged into the annular space at the top of the same and to carry it downward through the pipes from which it would seek its level within the wall surrounding the jacket, whence it would be led off through a waste pipe placed at the desired level. In accordance with modern practice, the tuyeres are spaced as closely as possible, there being sixteen 6-inch tuyeres in the circle. A special feature is the great number of cooling plates. As will be seen in Fig. 7, there are twelve rings of bronze coolers, two of which are below the tuyeres and three additional rings of cast iron coolers above the bronze plates. Fig. 8 shows clearly the construc- tion of the coolers with their socket plates, and Fig. 9 the details of the tuyeres. There are, in all, 277 bronze and 48 cast iron coolers in each furnace. The stock lines are protected by twelve rings of cast iron segments built into the brickwork. The mantels are built of f-inch steel plate, with two courses of -|-inch plate at the bottom and one at the top. The gases generated in the stacks are led off through two downcomers, each 73 inches in diameter and brick- lined to 63 inches inside diameter. The general outline of these downcomers may be seen in the general plan of the furnaces, Fig. 4, and it will be observed that, owing to the steep angle at which they are carried up, it is practically impossible for dust to lodge in them at any point, which is a very important consideration. As a matter of fact, when the furnaces were blown out, after a year's run, these pipes were found to be as clean as a gun barrel. In the dust- catcher (Fig. 10) the direction of motion of the descending gases is so suddenly changed upward that ample opportunity is given for the precipitation of the dust, which can then be dropped into rail- way cars standing on the track which runs through the tunnel under the foundations.
The gases are further cleansed by being precipitated against the surface of a body of water in the gas washer (Fig. 11). From the washer the gases are led into the gas main. A by-pass, how- ever, is arranged whereby the washer can be cut out of the system. This is accomplished by making two connections direct from the [4]
So
ASSOCIATION OF ENGINEERING SOCIETIES.
dust-catcher to the gas main, controlled by 56-inch cut-off valves, which are fitted with water-cooled seats and discs. The connec- tions from the dust-catcher to the washer, and from the washer to the gas main, are controlled by cut-off valves of a different type (Fig. 12). In Fig. 13 are shown the various connections between the downcomer and the gas main.
The gas main is a steel shell 85 inches in diameter and brick- lined to 75 inches, and it extends along the front of the eight stoves, having a downward connection to the burner at each of them. Here again precautions are taken to precipitate the dust
carried over by the gas ; also in the burner itself there is still another dust-catching chamber. The stove burner is 18 inches in diameter, with a 6-inch air supply pipe (Fig. 14), and the opening for it in the stove is 22 inches in diameter.
Furnace gases are slow in burning, and for economical results a long combustion chamber of ample size must be provided. By reference to the section through the stoves (Fig. 15) it will be seen that the combustion chamber is carried up to the top, and that the burnt gases descend through the rectangular passages formed by the stove bricks, which are heated thereby until they reach the desired temperature. Each stove has a heating surface of 34,000 square feet. The gases are passed from the stoves to the chimney
A MODERN AMERICAN BLAST FURNACE. 51
through a 50-inch valve with air-cooled disc and water-cooled seat ; the air is brought down through the stem, as shown in Fig. 16. The chimney is 10 feet in diameter and 225 feet high, and brick- lined to the top (Fig. 17).
In designing these furnaces it was figured that each of them would require from 45,000 to 50,000 cubic feet of air per minute, measured by piston displacement, when making 600 tons of iron each in twenty-four hours. To supply this volume the engine house is equipped with five horizontal compound blowing engines, with steam cylinders 44 and 84 inches in diameter, and two air cylin- ders 84 inches in diameter, all having a common stroke of 66 inches. The general design of these is shown in Fig. 18. The fifth engine is intended for a reserve, to be thrown on either pair of furnaces in the contemplated extension. They are designed to be capable of delivering air at a maximum pressure of 30 pounds per square inch, although the average blast pressure is only about 14 pounds. Any engine can be connected with either furnace at any time, as the two cold-blast mains run parallel with one another over the blowing cylinders, and each main has a connection with a shut-off valve to each cylinder.
The cold blast mains are 48 inches in diameter, and are rolled from ^-inch plate. Each is equipped with a 48-inch snort valve, which in closing opens a 14^-inch relief valve mounted on the same frame, and thus prevents a dangerous pressure from accumulating in the main when the blast is suddenly shut off from the furnace. In addition, there are three 8-inch safety valves on each pipe. Thirty-inch connections are made from the mains to the stoves (Fig. 19), and the valves in these branches have in their seats a smaller valve which opens first automatically and relieves the pres- sure, an arrangement which enables the main valve to be opened more easily.
The cold air from the blast mains passes into the stoves and up through the checker bricks, which have been previously heated by the burning furnace gases, and down through the combustion cham- ber— the gas burner having been withdrawn and its door and chimney valve closed — into the hot-blast main through a 32-inch hot-blast valve (Fig. 20). By referring again to Fig. 19 these connections will be readily traced. The hot-blast mains are 69 inches in diameter, and double brick-lined to 50 inches inside diameter. Before connecting with the bustle pipes, the hot-blast mains divide and join them with two connections in order to better equalize the pressure around the complete circle. From the bustle pipes the hot blast is led to the tuyeres, and into the furnaces
52 ASSOCIATION OF ENGINEERING SOCIETIES.
through the tuyere stocks. Two 16-inch drop valves are placed on the bustle pipe. These open automatically when the blast pressure is shut off, and air is admitted instead of drawing dangerous gases back through the tuyeres from the furnace; these also close auto- matically when the blast is turned on. Explosion doors are pro- vided at the furnace top, and wherever possible in all pipes and chambers carrying gas.
For handling the stock at these furnaces an entirely new sys- tem is in use. The stock bins are placed underground (Fig. 21). There are five stock bin cars, with suspended weighing hoppers, for the two furnaces. The bins are 725 feet in length, and the ore, limestone and coke are delivered to the furnace skip car by the weighing cars, which draw their supply from the chutes in the bottom of the bins. The skip then carries the charges up the in- cline and delivers them at the furnace top, as shown in Fig. 22.
The stock bin cars are driven by two railway motors, and the door in the bottom of the suspended hopper is opened and closed by an air cylinder, the pressure being supplied by an electrically- driven air-pump carried on the car. The operator can weigh all charges from the car platform. The skip has a capacity of 240 cubic feet, and is hoisted, by means of four i^-inch cables, by a pair of 14 x 16-inch engines geared 6.5 to 1 to a 72-inch drum. To complete a single "charge" the skip makes four trips, — taking first two loads of coke and then two loads of ore and limestone mixed. Two loads of coke, or of limestone and ore, are kept always on the bell in order to act as a seal and to keeo it cool. When making 600 tons of iron in twenty-four hours the skip delivers ninety "charges," making 360 trips to the furnace top, an average of a return trip every four minutes. The skip is counterweighted, so that the engine does work both in raising and in lowering it.
For pumping water for the cooling plates there are two com- pound, fly-wheel Holly pumps, each having two double-acting water plungers 22 inches in diameter, with a stroke of 28 inches. These are capable of delivering 7,000,000 U. S. gallons of water per twenty-four hours each. As a reserve there is also a duplex pump with two double-acting water plungers, 14 inches in diameter and 10 inches stroke. All these pumps deliver water to a stand pipe 12 feet in diameter and 150 feet high. The water passes through from three to four cooling plates before being discharged into the waste troughs. Arrangement is made also whereby water from the boiler-feed system can be sent through the cooling plates, in order to force out deposits of sediment by means of the in- creased pressure. Brass ball-and-socket unions are used through- out the piping for the cooling system.
A MODERN AMERICAN BLAST FURNACE. 53
The boiler house is equipped with 24 vertical water tube boilers, each of 250 horse power ; so arranged as to use either fur- nace gas or coal as fuel. A cross-section of the boiler house is shown in Fig. 23, as is also the type of boilers used. These boilers are admirably adapted for furnace gas as fuel, as, on account of their great height, there is sufficient time to effect the complete combustion of the slow-burning gases. The gas main from the furnaces is extended into the boiler house, and has a connection to the burner in front of each grate.
With the increasing output from single furnaces, it was soon found to be practically impossible to handle the pig iron quickly enough when cast in sand beds in the ordinary manner; and this was the first cause of the development of the pig casting machine, which, with the mixer or storage tank, is one of the most important of recent inventions in connection with the blast furnace. Fig. 24 gives a general idea of the form of the machine. It consists of two endless chains carrying molds or chills of pressed steel, the details of which are shown in Fig. 25. In operation the machine is beautifully simple. The molten iron is poured from the ladle into a trough terminating in two spouts, from which it runs into the chills. The chain then drops down under the surface of the water contained in the tank, and travels under water for a distance of about 100 feet. It then turns upward, and as it ascends the incline the pigs are sprayed with cold water from a spray pipe ; and by the time they reach the head of the machine they are sufficiently cooled to be loaded on cars which stand on the loading track. They may, as an alternative, be delivered by the machine to a con- veyor, which in turn delivers them to the stock piles for use in the cupolas. The chains travel at the rate of 20 feet per minute, and the chills are spaced 12 inches center to center, so that each chain delivers 20 pigs per minute, weighing on the average no pounds each ; and thus it will be understood how very efficient this machine is and what a great saving of labor it represents. Instead of clay washing the molds to prevent the iron from fusing with them, they are smoked by two smoke furnaces just before they pass over the tail sprockets. A set of chills will, under ordinary circumstances, last for nine months or a year. In cold weather, however, it is necessary to heat the water in the tanks, otherwise the repeated sudden and violent difference of temperature soon cracks the chills. The ladles are tipped by an electric ladle-tipping machine, from the spindle of which a connection is made with the hand wheel on the ladle car. Provision is made for casting in sandbeds at the fur- naces, using the space inclosed by the retaining walls between the
54 ASSOCIATION OF ENGINEERING SOCIETIES.
two stacks and opposite the stoves ; but this is done only in case of accident to the casting equipment.
Fifteen-ton ladle cars (Fig. 26) are used to convey the molten iron from the furnaces to the pig-casting machine. By referring again to the general plan it will be seen that these stand in a row on the hot-metal track which runs along the front wall inclosing the furnace foundations, and that the iron runners from the tapping holes terminate in spouts at a sufficient elevation to allow the iron to pour into the ladles. Similarly, the slag runners have spouts projecting over the cinder track, which is parallel to the end retain- ing wall. The cinder ladles (Fig. 27) are of 200 cubic feet capacity, and have removable cast iron linings, which can be renewed when worn out. The furnaces are tapped six times per day each, draw- ing off 100 tons of iron at each cast when working at their full capacity. The tapping hole is stopped up after the cast by means of a steam tapping-hole gun, which is shown in Fig. 28, as is also its method of use. It is suspended from a small jib crane attached to one of the furnace columns, and can be swung out of the way when not in use.
When the iron from the furnaces is to be used direct in the steel mill without remelting, the ladle cars containing the molten metal are taken to the mixer building, which contains a large mixer or storage tank which is capable of holding 300 tons of molten iron, and the general design of which is shown in Fig. 29. Here the ladles are lifted off the cars by an overhead electric traveling crane, and the iron is poured into the tank, which serves the double purpose of a reservoir from which the steel works can draw their supply and also of insuring a very much more uniform grade of iron, since all casts are mixed together. The mixer itself can be tilted by hydraulic cylinders to pour the iron into the steel works ladle. The iron is kept from chilling by means of fuel-oil burners inserted in the doors placed on the center of rotation and in the pouring spout.
Furnace No. 1 was put in blast July 5, 1899, and blown out July 14, 1900; furnace No. 2 was blown in August 23, 1899, and put out of blast July 19, 1900. During these periods No. 1 made 162,687 tons °f iron, and No. 2 made 132,290 tons. They were seldom worked to their full capacity. Figs. 30 and 31 respectively show the lines of the furnace walls obtained by actual measurement immediately after cooling off ; measurements were taken at four points of the compass, as indicated in the figures. It will be seen that the diameter of the bosh has increased considerably for the short blast ; bronze plates in place of the cast iron coolers would
A MODERN AMERICAN BLAST FURNACE. 55
probably have held the lines better at this point, and several new furnaces are being so equipped. The cast iron rings protecting the stock lines were found to be badly warped inward ; in many cases they had drawn the brickwork with them. This was probably caused by the high temperature at the furnace top when blowing out. However, it is very doubtful as to whether these rings are of any practical value. If they are used at all, they should be made light enough to prevent their warping from drawing the brickwork. There is a good deal of wear on the stock lines, as will be realized by referring to Fig. 32, which shows the profiles of stock as de- livered by the bell ; but with unprotected walls this would be evenly distributed all the way round, and the movements of the stock would probably be more regular on account of having no projections on the walls. The action of the bell and seal were very satisfactory.
The operators' houses were originally placed over the incline on each furnace top, which necessitated keeping two men in each house on account of danger from escaping gases, but later a single house was placed on the center of the stove platform, from which the bell apparatus for both furnaces was operated with much less expense and greater immunity from danger. The furnace top is equipped with six explosion doors placed directly under the plat- form. This proved to be a serious defect, as whenever gas leaking from these became ignited the mantel and platform were often badly warped by the heat; and in one instance the frame carrying the incline was also badly bent. This demonstrates the necessity of carrying the explosion-door frames out from the furnace clear of everything. The joints of these doors were originally made as shown in Fig. 33, a, but after the furnaces were blown out they were changed as shown in Fig. 33, b. The surfaces in this case were machined, and the door and frame brick-lined. The value of asbestos packing for doors that open frequently is very doubtful, as it soon becomes dry, hard and lifeless, which makes the preven- tion of leakage impossible. In another of the large furnaces recently built in this country the joints of the furnace-top explosion- doors were simply plain, flat, machined surfaces.
The cooling system of the hearth jacket was soon rendered in- effective by the stopping up of the pipes, due to leakages and small breakouts of slag from the bosh walls, which made it necessary to spray water on the outside of the jacket. The depth of the jacket is also unnecessarily great, and perhaps the only advantage of this type of jacket is that a section can be replaced when damaged by a breakout or other cause. The average amount of cooling water used for both furnaces was about 7,000,000 U. S. gallons per
56 ASSOCIATION OF ENGINEERING SOCIETIES.
twenty-four hours. This includes that used in the furnace-cooling system, and in the seats and discs of all water-cooled valves. The average rise in temperature of the water was 10.50 F. From these figures we may arrive at a very close approximation of the amount of heat carried away by the water. A complete system of cast iron runners for the hot metal was originally installed, but this was soon found to be useless and was dispensed with except at the spouts. There is a great difference of opinion in regard to the use of cooling plates below the tuyeres ; many claim that the tendency to chill the iron is too great, but it may be said that they were used with very satisfactory results in these stacks.
It is remarkable to what a small extent furnace designers have been guided by experience in the construction of heating stoves. Very many of the largest furnace plants have been badly crippled for long periods of time in order to allow the stoves to be recon- structed. The points of weakness are principally found in the plates forming the lower courses, and in the weakness of the stove fittings riveted to the shell. The plates of the bottom course in the Lorain stoves were -£ inch thick, and many of these were badly cracked soon after the furnaces were put in blast. It will be seen, by referring to Fig. 19, that all the pipe connections are made at the bottom, and that cutting away so much of the plate makes it very weak. For a stove of this size, therefore, a plate not less than J inches thick should be used. The flanges of castings, riveted to the stove shells, were about 1^ inches thick, of cast iron. Many of. these were also broken by the heat — especially the gas opening door — which caused bad and annoying leaks. These fittings were replaced by heavy steel castings, and no further trouble was experi- enced. Fig. 34 shows a gas opening door that has been very satis- factory. It will be noticed that the joint is of the spherical type, and that the door itself is brick-lined, which is the only sure way of preventing it from warping. The stove gas burner was originally designed 22 inches in diameter, with a 10-inch air-supply pipe, and the opening in the stove was made 28 inches in diameter. This burner was found to use too much gas, so that there was not suffi- cient for the boilers. It was modified to the dimensions shown with very satisfactory results.
The hot-blast valve (Fig. 20) is much heavier than the one originally used. The lighter valves were a great source of trouble, and in replacing them all the cast iron rings riveted to the shells were found to be cracked. All the castings, except the bronze water-cooled seats in the later valve, were of steel. On account of the hot-blast valve being opened and closed so frequently, and its
A MODERN AMERICAN BLAST FURNACE. 57
consequently greater liability to get out of order, another shut-off valve should be inserted between it and the hot-blast main ; other- wise a crippled hot-blast valve cripples the furnace, since no pres- sure can be carried in the hot-blast main. The longer branch made necessary by the extra valve is also of great advantage, in that more freedom is allowed for the expansion of the main.
The blast temperature could be easily raised to 12000 or 13000 F. with these stoves. With large percentages of soft ores in the burden, however, it is found that a high-blast temperature causes a high-blast pressure. A 15-inch mixing pipe, connecting the cold- and hot-blast mains, was often found to be too small to reduce the hot-blast temperature by the desired amount, and a larger connection had to be made. An automatic controlling device, used with great success at another of the large furnace plants, was also contemplated. This consists of placing in the mixing pipe a butterfly valve, which is electrically controlled from the pyrometer, to keep the temperature of the blast within certain limits. The power necessary to move the valve is supplied by the blast pressure. At the plant mentioned it was found to be possible to keep the temperature of the hot blast within 50 above or below that desired.
One of the greatest sources of trouble at these furnaces was the "whipping" of the cold-blast main caused by the pulsations of the engines. This is an annoyance to which too little attention has been paid at many furnace plants, especially when it is considered how easily it can be avoided. The mistake is often made of trying to hold the pipe against these pulsations by strapping it to some solid foundation, but this can result only in loosening the rivets and causing leaks. All that is necessary is to provide a receiver of suffi- cient capacity to break up the column of air and absorb the pulsa- tions.
The commercial efficiency of a furnace depends primarily upon the cost of delivering the raw materials of ore, limestone and coke at the furnace top, and of getting rid of its product as pig or molten iron. This plant is admirably situated with respect to its ore sup- ply, for the reason that the ore is unloaded from vessels* directly to the stock piles without reshipment by rail. From the stock piles it is loaded by steam shovels into special pressed steel hopper-
*The dock machinery for unloading ore from vessels was fully described in a previous paper read by the author before this Club, and published in the Journal of the Association of Engineering Societies, January, 1900, Vol. 24, page 1, and in an article in Cassier's Magazine, September, 1900, Vol. 18, page 355-
58 ASSOCIATION OF ENGINEERING SOCIETIES.
bottom cars of 50 tons capacity, similar to the standard steel railway- cars, but much shorter. These cars are then brought to the stock bins, and their contents are dropped through the hoppers, ready for use in the furnaces. Placing the stock bins underground has the advantage that no trestle with heavy grade approaches is re- quired, but it is very doubtful whether the great cost of construc- tion and maintenance is fully warranted on this account, as in cold weather the ore seems to freeze in them as readily as when placed in elevated bins. Limestone and coke are received by rail, and the coke is stocked by means of a traveling cantilever crane operating a grab bucket.
The plan of the furnace yard is shown in Fig. 35. All the tracks are of standard gauge, and the sharpest curve is of 461 feet radius. The hot-metal ladle car has a rigid wheel base of 7 feet 6 inches, and the 461-foot curve has been found by experience to be about as sharp as it can round. It is very important to have the tracks carrying hot metal as free from curves, grades and other complications as possible, as a ladle full of molten metal off the track is a very serious matter. It will be noticed, by reference to Fig. 26, that the ladle cars for hot metal are equipped with hand- tilting gear. This is certainly an unnecessary expense and compli- cation for a modern furnace equipment. Wherever the ladle must be tipped — namely at the pig-casting machine, the mixer and in the ladle repair house — there are cranes at hand to do this, and the hand gear is a drawback rather than a help. Especially is this so at the mixer, where the ladles are lifted off the car and replaced thereon after pouring. A much more satisfactory ladle car would be one mounted on a pair of swiveling trucks, with simply the necessary supports to receive the ladle trunnions and a lock to pre- vent the ladle from tipping while in transit. A satisfactory ladle is one of the most necessary adjuncts to a modern furnace equipment.
■ ■Q. <^»
V
-A MODERN AMERICAN BLAST FURNACE. PLATE 4.
FIG. 20. 32" HOT-BLAST VALVE
IS.
... 18. 44"X84'X84"X66"
. -,. . ..
ffl®^
OBITUARY. 59
OBITUARY.
George W. Percy.
By the sudden and lamentable death of our highly esteemed President, on Friday, December 14, 1900, the Technical Society, and indeed the entire community, sustained an irreparable loss.
George Washington Percy was born at Bath, in the State of Maine, on July 5, 1847, his early youth being spent amid agricul- tural surroundings. He received his education as a boy at the Kent's Hill Academy, in his native State. It was during the progress of the Civil War that he found employment in the mer- cantile marine of this country. At this time he made a voyage to Europe, and also visited other countries.
Endowed with a natural aptitude for mechanical and mathe- matical pursuits, he decided about this time to study architecture, with a view to adopting it as his life profession. How wisely his choice was made is exemplified by the many structures which will stand for ages as monuments of his professional skill and intelli- gence.
His technical education was commenced in the office of Mr. Fassett, of Portland, Maine, and for some years his time was spent in faithful and painstaking study in qualifying himself for practic- ing the profession of his choice. Subsequently Mr. Percy entered the office of Bradley & Winslow, architects, of Boston, Massachu- setts, and while there superintended several important works.
Coming to California in 1869, he settled in Stockton, returning to the East in September, 1871, immediately after the great Chicago fire, in which city he did some heavy work during the rebuilding operations, after which we once again find him located in Boston. Among other works with which Mr. Percy was associated in this latter city is the Equitable Life Insurance Building, a typical example of the class of work in which he took a special interest.
Returning once more to California, in 1876, and locating in San Francisco, still full of youth and energy, he immediately com- menced to build up a successful and steadily increasing practice. Numerous important buildings in San Francisco and throughout the Pacific coast will testify for many generations to his profes- sional ability and constructive knowledge. It is perhaps unneces- sary to do more than mention the following as being among the more important of Mr. Percy's works : Stockton Insane Asylum, Stanford University library and assembly hall, girl's dormitory, Stanford University, Academy of Sciences Building, Market, near
60 ASSOCIATION OF ENGINEERING SOCIETIES.
Fifth street; Alameda city hall, Nevada State University, Reno, Nevada ; Episcopal church, Stockton ; Alvinza Hayward residence, San Mateo; Leland Stanford, Jr., museum, Palo Alto; Crassley dome and professors' homes, Mt. Hamilton; Methodist Episcopal church business building, Alameda ; California School of Mechani- cal Arts, Sixteenth and Utah streets ; San Joaquin county alms- house ; De Fremery block, Oakland ; children's house and play- ground and other buildings in G. G. Park; Strathmore apartment house, Larkin street; First Unitarian church, Geary and Franklin streets ; Golden Gate Park panorama, Strawberry Hill ; City Front Stables, Clay, near East street ; John Benson office building, Leides- dorff and Pine streets ; Hobart Building, Post street ; the "Hobart" vault, Cypress Lawn Cemetery; Hoit's School, Menlo Park; the Bourn tomb, Laurel Hill Cemetery ; Wells Fargo Building, Mission and Second streets; Alexander Young business block, Honolulu; Hayward Building, California and Montgomery streets.
In 1 88 1 Mr. Percy traveled in Europe for pleasure and to study ancient and modern work, being especially interested in the archaeological remains of Rome of all ages. Indeed, his continued study and interest regarding ancient Rome in all its phases was maintained to the last, and probably few persons were better in- formed than he was concerning the materials and constructive methods of the Romans.
In addition to filling the presidential chair of the Technical Society, in which he took the warmest interest, Mr. Percy was an active associate member of the American Institute of Architects; also a trustee of the San Francisco chapter, American Institute of Architects, and also a member of the Pacific Lodge of Free and Accepted Masons. He was a member of the Berkeley Literary and Professional Club ; also of the Astronomical Society of the Pacific Coast, and was an amateur astronomer of no small ability. He was the author of many instructive technical papers, which he read before the societies in which he took so deep an interest. His interest in young students of architecture was often manifested, many of whom applied to him for advice and assistance in their studies, and never in vain. His skill and experience has also been frequently sought in consultations involving questions concerning architecture and construction. Among many such cases may be mentioned the fact that he was invited to act as consulting architect in connection with the new Union Depot and ferry building of this city. Indeed, it may justly be said of him that he was at the very zenith of a successful career, and that he not only occupied a high and honorable position among the members of his own profession,
OBITUARY. 61
but also enjoyed the absolute and perfect confidence of his many clients.
Among contractors and business men with whom he was brought into contact in the construction of his buildings he was most highly respected, and invariably regarded by them as being absolutely fair and just in his requirements, dispensing equal jus- tice to contractors and owners alike without fear and without favor.
A widow and four children — two sons and two daughters — are left to mourn the loss of a devoted husband and a loving father.
Mr. Percy possessed an exceedingly strong personality. His wide capability, his sterling integrity and earnestness and, above all, his absolute thoroughness were apparent in everything he undertook. These moral qualities and the knowledge that he was in every sense a manly man, as well as a genial gentleman, will ever be associated with the memory of our late fellow-member and friend.
G. Alexander Wright, Committee.
62 ASSOCIATION OF ENGINEERING SOCIETIES.
ASSOCIATION OF ENGINEERING SOCIETIES.
Articles of Association.
The following Articles of Association were adopted at a meeting held in Chicago, December 4, 1880. At this meeting there were present representa- tives of the
Western Society of Engineers, Civil Engineers' Club of Cleveland, Engineers' Club of St. Louis, and the
Boston Society of Civil Engineers was represented by letter.
For the purpose of securing the benefits of closer union and the advancement of mutual interests, the engineering societies and clubs hereunto subscribing have agreed to the following
ARTICLES OF ASSOCIATION.
ARTICLE I.
NAME AND OBJECT.
The name of this Association shall be "The Association of Engineer- ing Societies." Its primary object shall be to secure a joint publication of the papers and the transactions of the participating Societies.
ARTICLE II.
ORGANIZATION.
Section i. The affairs of the Association shall be conducted by a Board of Managers under such rules and by-laws as they may determine, subject to the specific conditions of these articles. The Board shall consist of one repre- sentative from each Society of one hundred members or less, with one ad- ditional representative for each additional one hundred members, or fraction thereof over fifty. The members of the Board shall be appointed as each Society shall decide, and shall hold office until their successors are chosen.
Sec. 2. The officers of the Board shall be a Chairman and Secretary, the latter of whom may or may not be himself a member of the Board.
ARTICLE III.
DUTIES OF OFFICERS.
Section i. The Chairman, in addition to his ordinary duties, shall countersign all bills and vouchers before payment and present an annual re- port of the transactions of the Board ; which report, together with a synopsis of the other general transactions of the Board of interest to members, shall be published in the Journal of the Association.
Sec. 2. The Secretary shall be the active business agent of the Board and shall be appointed and removed at its pleasure. He shall receive a com-
ARTICLES OF ASSOCIATION. 63
pensation for his services to be fixed from time to time by a two-thirds vote. He shall receive and take care of all manuscript copy and prepare it for the press, and attend to the forwarding of proof sheets and the proper printing and mailing of the publications. He shall have power, with the approval of any one member of the Board, to return manuscript to the author for correc- tion if in bad condition, illegible or otherwise conspicuously deficient or unfit for publication. He shall certify to the correctness of all bills before trans- mitting them to the Chairman for counter-signature He shall receive all fees and moneys paid to the Association and hold the same under such rules a~ the Board shall prescribe.
ARTICLE IV.
PUBLICATIONS.
Section i. Each Society shall decide for itself what papers and transac- tions of its own it desires to have published and shall forward the same to the Secretary.
Sec. 2. Each Society shall notify the Secretary of the minimum number of copies of the joint publications which it desires to receive, and shall fur- nish a mailing-list for the same from time to time. Copies ordered by any Society may be used as it shall see fit. Payments by each Society shall in general be in proportion to the number of copies ordered, subject to such modification of the same as the Board of Managers may decide, by a two- thirds vote, to be more equitable. Assessments shall be quarterly in advance, or otherwise, as directed by the Board.
Sec. 3. The publications of the Association shall be open to public sub- scription and sale, and advertisements of an appropriate character shall be received, under regulations to be fixed by the Board.
Sec. 4. The Board shall have authority to print with the joint publica- tions such abstracts and translations from scientific and professional journals and society transactions as may be deemed of general interest and value.
ARTICLE V.
CONDITIONS OF PARTICIPATION.
Section i. Any Society of Engineers may become a member of this A-sociation by a majority vote of the Board of Managers, upon payment to the Secretary of an entrance fee of fifty cents for each active member, and certifying that these Articles of Association have been duly accepted by it. Other technical organizations may be admitted by a two-thirds vote of the Board, and payment and subscription as above.
Sec. 2. Any Society may withdraw from this Association at the end of any fiscal year by giving three months' notice of such intention, and shall then be entitled to its fair proportion of any surplus in the treasury, or be responsible for its fair proportion of any deficit.
Sec. 3. Any Society may, at the pleasure of the Board, be excluded from this Association for non-payment of dues after thirty days' notice from the Secretary that such payment is due.
ARTICLE VI.
amendments. These articles may be amended by a majority vote of the Board of Managers, and subsequent approval by two-thirds of the participating So- cieties.
64 ASSOCIATION OF ENGINEERING SOCIETIES.
ARTICLE VII.
TIME OF GOING INTO EFFECT.
These articles shall go into effect whenever they shall shall have been ratified by three Societies, and members of the Board of Managers appointed. The Board shall then proceed to organize, and the entrance fee of fifty cents per member shall then become payable.
These articles were adopted by the several Societies upon the following dates :
Engineers' Club of St. Louis, January 5, 1881. Civil Engineers' Club of Cleveland, January 8, 1881. Boston Society of Civil Engineers, January 19, 1881. Western Society of Engineers, April 5, 1881. The Board of Managers was organized at Cleveland, January 11, 1881. The following Societies have since certified their acceptance of the arti- cles, and have become members of the Association of Engineering Societies : Engineers' Club of Minneapolis, July, 1884. Civil Engineers' Society of St. Paul, December, 1884. Engineers' Club of Kansas City, January, 1887. Montana Society of Civil Engineers, April, 1888. Wisconsin Polytechnic Society, June, 1892. Denver Society of Civil Engineers, January 24, 1895. Association of Engineers of Virginia, February 1, 1895. Technical Society of the Pacific Coast, March 1, 1895. Detroit Engineering Society, January, 1897. Engineers' Society of Western New York, January, 1898. Louisiana Engineering Society, September 15, 1898. Engineers' Club of Cincinnati, January, 1899. The Wisconsin Polytechnic Society withdrew from the Association in March, 1894.
The Western Society of Engineers withdrew in December, 1895. The Engineers' Club of Kansas City disbanded at the close of 1896. The Denver Society of Civil Engineers and the Association of Engineers of Virginia disbanded in 1898.
ANNUAL REPORT OF THE CHAIRMAN. 65
Animal Report of the Chairman of the Board of Managers.
December 31, 1900. To the Members of the Board of Managers of the Association of Engineer- ing Societies:
Gentlemen: — I have the honor to transmit to you and to the Asso- ciation through you, the annual report of the Secretary of the Association for the year 1900. This shows an increase in membership during the year from 1475 in 1899 to 1541, while the number of the societies has not changed.
There has been a slight increase in the cost of the Journal, as shown by the Secretary's report, causing a diminution in the net assets from those of 1899. The character of the Journal is such that there should be no difficulty in making it self-sustaining, and the attention of the mem- bers of the Association is called to the fact that our Journal has a cir- culation of about 1900 copies, and the advantages of advertising in such a journal will be evident to all.
In the report of the Chairman for 1899 he stated that no Engineer could afford to be without the Journal. I desire to repeat that statement, and ask the members of the Association to keep this Journal before their friends, with a view to inducing them to subscribe to it.
I also desire to call your attention to the able and efficient work of the Secretary, who does all the business of the Association, and gives a great amount of time and care to the work. It is desirable that the mem- bers of the Association should make every effort to secure advertisements for the Journal among the members of the societies which they represent.
Respectfully submitted,
James Ritchie, Chairman.
Annual Report of the Secretary of the Board of Managers.
Philadelphia, December 31, 1900. Mr. James Ritchie, Chairman,
305 City Hall, Cleveland, O.
Dear Sir: — I have the honor to present the following report upon the operations of the Secretary's office during the year 1900, and of the condition of the Association at the present time.
These data are concisely stated in the following statistical appendices:
A. Statement of receipts and expenditures during 1900.
B. Estimate of assets and liabilities at the close of 1900.
C. Detailed statement of cost of Journal during 1900, by months.
D. Comparison of mailing lists of the Journal at the close of 1899 and of 1900, respectively.
E. Statement of material in Journal during 1900, by pages.
66 ASSOCIATION OF ENGINEERING SOCIETIES.
F. Comparison of conditions, 1894 to 1900, inclusive.
A study of Appendix F shows an increase in the cost of the Journal, with a corresponding diminution of net assets, due partly to a sharp advance in the printers' rates and partly to an increase of 18 per cent, in the amount of matter published. The close of the year, nevertheless, finds us with a cash balance in hand of $1448.24, and total net assets of $2165.67.
During the year, no new societies have joined the Association, but the aggregate membership of our societies shows an increase of about 4^ per cent. The present aggregate of 1541 members is greater than at any time during the history of the Association, exceeding, as it does, by about 4^ per cent., the aggregate membership at the close of 1895, before the withdrawal of the Western Society of Engineers.
In my report for 1899 I was obliged to call attention to " a decided falling off in the amount of material presented for publication in the Journal," the number of pages per thousand members having fallen to 369, the lowest reached during the preceding six years.
This condition has been, to a great extent, remedied during 1900; the number of pages of papers having increased from 958 in 1899, to 1130 in 1900, and the total per thousand members having increased to 432.
The close of the year finds us with considerable material on hand await- ing the January Journal.
In my last annual report I called attention to the commendable activity of the Cleveland Society in obtaining advertisements for the Journal, that society having, by means of the commission of 90 per cent, allowed by the Association, relieved itself entirely of charges on account of the Association Journal.
At this writing the Engineers' Club of St. Louis is taking measures to follow the example of the Cleveland Society.
The List of Members of the Societies in the Association, first pub- lished in the Journal for January 1899, and again in that for January 1900, now appears for the third time, and with further improvements in the matter
of its typography.
Respectfully submitted,
John C. Trautwine, Jr., Secretary.
ANNUAL REPORT OF THE SECRETARY. 67
APPENDIX A.
Statement of Receipts and Expenditures during 1900.
CASH, 1900.
Dr.
To Balance. January 1, 1900 $1,866 34
" Assessments, at $2.00 per member :
Boston Society of Civil Engineers $992 00
Civil Engineers' Club of Cleveland 387 50
Engineers' Club of St. Louis 407 00
Civil Engineers' Club of St. Paul 58 00
Engineers' Club of Minneapolis. 28 50
Montana Society of Engineers 168 00
Detroit Engineering Society .. 171 00
Engineers' Society of Western New York, 83 00
Louisiana Engineering Society 120 00
Engineers' Club of Cincinnati 179 00
Technical Society of the Pacific Coast 288 50
To Subscriptions
" Sales of Journal
" *' " Descriptive Index
" Advertisements.
" Sales of reprints ,
" Interest on deposits
" Electros
" Letter-heads
" Copyright fee
' Illustrations furnished to authors, etc.
' 792 misdirected envelopes sold.
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2,882 |
50 |
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768 |
94 |
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l8l |
92 |
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26 |
50 |
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370 |
83 |
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IO4 |
25 |
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16 |
44 |
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25 |
25 |
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6 |
25 no |
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1 |
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65 |
17 |
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15 |
84 |
Cr.
By Patterson & White Co. (Printers) $3,523 15
Illustrations 558 10
Secretary's salary 600 00
Car fares 30
Discounts on subscriptions 28 85
" sales 2 20
Messenger service 4 42
Stationery 17 40
Telegrams 9 46
Postage stamps 34 32
Express charges 2 55
Back numbers bought 50
Binding Journals for Paris Exposition 8 50
Civil Engineers' Club of Cleveland. Amount due
from advertisement 16 20
Prof. Geo. D. Shepardson, expenses as chairman 5 00
Engineers' Club of St. Louis, credit balance at end
of 1899 9 50
>,33i 23
Forward $4,820 45 $6,331 23
68 ASSOCIATION OF ENGINEERING SOCIETIES.
Forward $4,820 45 $6,331 23
By Secretary's trip to Boston, Feb. 6
trip to New York, March 9 ,
Copyright fee
Subscriptions refunded ,
Amount overpaid on subscription, refunded. Advertising, including cost of cuts ($24.80).
4,882 99
|
21 |
10 |
|
4 |
00 |
|
1 |
00 |
|
5 |
50 |
|
2 |
00 |
|
28 |
94 |
Cash balance, December 31, 1900 $1,448 24
APPENDIX B.
Estimate of Assets and Liabilities at the Close of 1900.
available assets.
Cash balance, December 31, 1900 $1,448 24
Less subscriptions for 1901, paid during 1900 53 00
$i,395 24
Amounts receivable from Societies (for assessments, etc.):
Boston Society of Civil Engineers $38 20
Montana Society of Engineers 130 00
Detroit Engineering Society 47 50
Engineers' Society of Western NewYork, 34 55
$250 25
Subscriptions due:
For 1900 90 00
" 1899 100 80
" 1898 and earlier 19200
382 80
For reprints 109 60
' Advertisements 306 ^^
" Sales of Journals 2250
" Index. 725
" " " Cuts 275
$1,081 48
$2,476 72
LIABILITIES.
Patterson & White Co. (Printers):
For December Journal $168 50
" Reprints 700
$175 50
Civil Engineers' Club of Cleveland, commissions
on advertisements $108 90
Engineers' Society of Western New York 70
Illustrations. 25 95
311 05
Net Assets $2,165 67
ANNUAL REPORT OF THE SECRETARY.
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70 ASSOCIATION OF ENGINEERING SOCIETIES.
APPENDIX D.
Comparison of the mailing lists of the Journal, at the close of 1899 and of 1900, respectively:
In- De-
1899. 1900. crease. crease.
Boston Society of Civil Engineers 495 501 6
Engineers' Club of Cleveland 185 208 23
Engineers' Club of St. Louis 206 204 ... 2
Civil Engineers' Society of St. Paul 29 29
Engineers' Club of Minneapolis.. 19 13 ... 6
Montana Society of Engineers 107 109 2
Technical Society of the Pacific Coast 146 136 ... 10
Detroit Engineering Society 97 105 8
Engineers' Society of Western New York. 43 72 29
Louisiana Engineering Society. 53 74 21
Engineers' Club of Cincinnati 95 90 ••• 5
In the societies composing the Association, 1475 1541 89 23
Net increase 66
Extra copies to Societies 46 50 4
Advertisers 18 14 ... 4
Exchanges 115 116 1
Subscribers 249 216 ... 33
Complimentary copies 1 6 5 ...
Totals 1904 1943 99 60
Net increase 34
Besides this, many copies have been sold and specimen copies sent out; and authors of papers have each received five copies of the Journals contain- ing them. Two thousand five hundred copies of the January number were printed, 2100 of February, March and April, and 2250 of each of the other months.
APPENDIX E. Statement of material in Journal during 1900, by pages.
January
February
March
April
May
June
July
August
September ...
October
November ..... December
Papers.
Pro- ceed- ings.
Chair- man's Report
24
Adver- tise- ments.
Indexes to Vols.
List of Mem- bers.
Totals.
210 104 84 80 86 76 90 60 74 74 80 64
Totals 666 107 24 187 16 82 1082
Covers 48
Total 1 130
Cuts.
Plates and full- page cuts.
ANNUAL REPORT OF THE SECRETARY.
7i
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Editors reprinting articles from this journal are requested to credit not only the Journal, but also the Society before which such articles were read.
As
SOCIATION
OF
Engineering Societies.
Organized 1881.
Vol. XXVI. FEBRUARY, 1901. No. 2.
This Association is not responsible for the subject-matter contributed by any Society or for the statements or opinions of members of the Societies.
BRICK AND CONCRETE-METAL CONSTRUCTION.
Papers Presented at the Meeting of the Boston Society of Civil Engineers, held October 17, 1900.
Economy and Strength of Brick and Concrete Arches for Floor Systems of Highway Bridges.*
By William D. Bullock, Member Boston Society of Civil Engineer
The Weybosset bridge in the city of Providence spans the Providence River at Market square. There are three piers dividing into four spans the river channel, which is 132^ feet wide. The channel at the bridge being on a curve the steel plate girders, which are 42^ inches deep, are placed on radial lines, Fig. 1.
Extending from girder to girder, and riveted to them, are transverse floor beams 2 feet deep and spaced 8^ feet apart. Supported on these floor beams are 10-inch I beams, spaced about 2 feet 5 inches apart in radial lines, between the main girders.
The spaces between the I beams and the main girders are covered by brick arches, leveled up with Portland cement con- crete to within 2 inches of grade.
The area of the bridge is 31,610 square feet.
Located as this bridge is, in the center of the city and furnish- ing the main passageway between the east and west sides, it is subjected to very heavy and concentrated travel, including both highway and trolley car travel. Under these circumstances the question of designing a substantial floor at a reasonable cost became one of great importance.
^Manuscript received November 6. 1900. — Secretary, Ass'n of Eng. Socs. 12
74
ASSOCIATION OF ENGINEERING SOCIETIES.
BRICK AND CONCRETE-METAL CONSTRUCTION.
75
76
ASSOCIATION OF ENGINEERING SOCIETIES.
The ordinary forms of flooring of steel shapes, at the price of 2.34 cents per pound paid for this bridge, would cost about 72 cents per square foot, and the concrete for leveling up ready to receive the asphalt paving would cost 15 cents per square foot, making a total cost of 87 cents per square foot for this form of construction at the former low price of steel. At the prevailing prices of steel during the past year, of say 5 cents per pound, the cost would be about $1.68 per square foot.
The cost of the steel 10-inch I beams and dam plates was 26 cents per square foot of floor, and the cost of the brick arches and concrete for leveling up to grade was 26 cents per square foot, making a total cost, for the masonry floor, of 52 cents per square foot. This shows a difference of 35 cents per square foot in favor of the masonry floor as compared with the low con- tract prices. In addition to the saving in the first cost of the masonry arch floor, there is an additional saving in the reduced surface of metal to be painted.
— — — - —
Fig. 3. Test of Arches Proposed for Driveway Floor of the Weybosset
Bridge.
The weight of the steel floor of Carnegie shapes leveled up with concrete would be about 112 pounds per square foot and that of the masonry floor 118 pounds per square foot.
After the plans were decided upon and the actual work of construction begun, it was decided to make the concrete 2f inches thicker, in order to enable the trolley company to use deeper rails than originally intended. This increased the weight 39! pounds and the cost 7 cents per square foot. Fig. 2 shows the section of the floor as actually constructed.
The question is thus narrowed down to whether or not a thin floor of masonry arches between steel I beams will have sufficient strength to meet the trying conditions of a city high- way bridge. In addition to various calculations made to deter- mine this question, it was thought desirable to make some prac-
BRICK AND CONCRETE-METAL CONSTRUCTION.
17
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78 ASSOCIATION OF ENGINEERING SOCIETIES.
tical tests on arches of the same dimensions and exactly of the same construction as those proposed to be used. In the city bridge shop 6 brick arches were built between io-inch I beams, leveled up with concrete, and the I beams tied together with iron clamp bars. In the absence of any testing machine a contrivance was improvised from materials on hand for making the tests, substantially as shown by Fig. 3. The arches were made of par- tially vitrified paving brick made by the New England Brick Company and laid in Atlas Portland cement mortar, 1 to 1. The concrete was made of Atlas and Alpha Portland cement 1 part, sand 2 parts and screened medium gravel 4 parts. The Atlas cement, tested neat in briquettes at the end of 24 hours, showed a tensile strength of 426 pounds per square inch and the Alpha 365 pounds per square inch.
The voids in sand were 30.3 per cent, of volume.
The voids in gravel were 35.9 per cent, of volume.
The weight of the brick arches per cubic foot was 150.3 pounds and the concrete 158.1 pounds.
The foregoing table shows the results of the tests. The bear- ing shoe was of the same width and curvature as some of the heavy low gears in use in this city. The yielding of the heavy 4 x £-inch clamp bars in the first and sixth experiments showed that there was a large horizontal thrust from the arches.
BRICK AND CONCRETE-METAL CONSTRUCTION. 79
A Test of the Strength of Rapp Floor Arches.*
By Frederic H. Fay, Member Boston Society of Civil Engineers.
From time to time the Engineering Department of the City of Boston has been asked by the Building Commissioner to make tests upon different types of fireproof floors. These tests, however, had nothing to do with fireproof qualities, they having been made solely to satisfy the Commissioner that the floors in question were capable of sustaining the load required by the city building laws. Hence we might call them tests of the "working strength." One of these, a test of some floor arches of the Rapp type of construction, is described herewith. Considering the fact that the test was made upon one of the floors of a building (which at the time was in process of construction), and that the arches had been built before the test was proposed, it is thought that the conditions found were those likely to be met in practice.
Details of this Rapp floor are shown in the accompanying figures.
Two adjoining arches near the center of the building were selected for the test, the span of each arch being, approximately, 7 feet 10^ inches, and the width 16 feet 5 inches, the distances being measured between the centers of the supporting beams. The total area of the two is about 258 square feet.
The test consisted in loading the arches with a live load of about 500 pounds per square foot, the behavior of the arches during the test being studied by noting their deflection and spread.
CONSTRUCTION OF THE FLOOR.
Between columns 11 and 12 and columns 16 and 17 are two 18-inch I-beam headers. At right angles to the latter are three 15-inch I beams, the middle one being framed into the 18-inch beams and the other two connecting directly to the columns.
Curved Rapp tees are supported by the bottom flanges of the 15-inch beams. These tees consist of pieces of sheet steel 4^ inches wide and 1-16 inch thick, bent so as to form a "T" section with about 2^-inch flange and i^-inch stem. Separators, made by bending a strip of steel 1^ inches wide by 1-16 inch thick, regulate the spacing of the tees at about 8f inches on centers.
The Rapp tees being placed with their stems upward, the flanges are available for supporting rows of bricks which form an
*Manuscript received November 6, 1900. — Secretary, Ass'n of Eng. Socs.
8o ASSOCIATION OF ENGINEERING SOCIETIES.
arch of nearly 9 inches rise above the bottom of the beams. The bricks were laid dry, and after they were in place cement grouting was supposed to have been poured over the arch and into the joints between the bricks. Many of the joints, however, apparently con- tained but little mortar.
A filling of cinder concrete, said to be made of one part Atlas cement and eight parts cinders, was then deposited upon the arches to the level of the tops of the 15-inch beams. Thus there was about 4 inches of concrete above the brick arch at the crown, the depth increasing to a maximum of 12 inches of concrete at the springing. Neither the upper layer of concrete, inclosing the nailing strips, nor the wooden floor had been put in place at the time the test was made.
The 15-inch I beams were said to be connected by tie rods, which had been bent upward two inches or more out of line in order that they might not be exposed in the ceiling at the crown of the arch.
Separator
Rapp Tee
Details of Arch
Details of Rapp Floor in Building on India Street.
DETAILS OF THE TEST.
The test was begun Wednesday, November 9, and ended Saturday, November 12. When the arches received their full load the concrete filling had been in place fifteen days. The loading was made by using bricks carefully piled in such a manner as to avoid breaking joints, thus allowing their weight to be uniformly distributed. A representative of the building department super- vised the loading, and by weighing and measuring several lots of bricks secured the data from which the total weight of bricks was estimated from their volume. The maximum load applied was, very closely, 500 pounds per square foot.
The deflection of the floor was obtained by taking levels upon the under side of the beams and arches of the two bays tested, and
BRICK AND CONCRETE-METAL CONSTRUCTION. 81
also upon two of the adjoining arches. The spread of the arches was determined by measurements with a steel tape and an engi- neer's scale.
The first series of levels and measurements was made between 10 and 2 o'clock of Wednesday, November 9, before any live load was applied to the floor. From 2 o'clock of Wednesday until noon of Thursday workmen were engaged in putting on the bricks.
Partial Plan of Second Floor, Showing Tested Bays.
Friday morning, after the arches had been carrying their full live load for nearly twenty-four hours, the second series of readings was taken. Friday afternoon the load was entirely removed. After a period of rest of about sixteen hours the bays were again measured on Saturday morning, to determine to what extent the floor had recovered from the effects of the load.
Table I shows the deflections of the two arches tested. The deflections there given are net ; that is, the toral drops of the arches have been corrected to allow for the settlement of the supporting beams, so that the net results given are the same as though there had been no vertical movement of the arch supports.
82
ASSOCIATION OF ENGINEERING SOCIETIES.
TABLE I. Showing Deflection of Arches.
|
Point. [On Under Side of Arch]. |
Deflection Under Live Load of 500 Lbs. per Sq. Ft. |
Upward Movement Upon Removal of Load. |
Deflection Still Remaining after Removal of Load. |
||
|
k |
0.21 inch |
O. II inch |
0.10 inch |
||
|
1 |
0.26 |
" |
0 14 " |
0.12 " |
|
|
in |
0.24 |
" |
C. 1 6 " |
0.08 " |
|
|
11 |
0.18 |
" |
O 13 " |
0.05 " |
|
|
o |
0.30 |
" |
019 " |
O.II " |
|
|
p |
0.22 |
c i |
O 16 " |
0.06 " |
|
|
Average for Arch kllll Average for Arch nop Average for both arches |
0.24 0.23 0.23 |
« |
0.14 " 0.16 " 0.15 " |
O.IO " 0.07 " 0.09 " |
Measurements at the middle of the 15-inch beams showed the spread of the arches in the direction C D to be as given in Table II.
TABLE II. Showing Spread of Arches.-
|
Arch. |
Elongation Under Live Load of 500 Lbs. per Sq. Ft. |
Contraction Upon Rrmoval of Load. |
Elongation Still Remaining after Removal of Load. |
|
From b to e From e to li |
0.16 inch 0.09 " |
0.09 inch 0.07 " |
0.07 inch 0.02 " |
Throughout the test levels were taken upon the two adjacent arches, at C and D, which were liable to deformation from the thrust of the loaded arches. Xo considerable movement was found in either adjacent arch, and apparently their shape was practically unchanged.
CONCLUSIONS.
Under the load of 500 pounds per square foot the average deflection of the two arches tested was ^ inch. Sixteen hours after the removal of the load the arches had regained about 60 per cent, of their deflection, making the average deflection still remaining less than ^ inch. Some permanent set might have been expected, due to the closing of certain joints between bricks which were only partly filled with cement grout. Still, it is possible that the arches had not entirely recovered from their fatigue, and that a further slight upward movement could have been detected had readings been taken at a longer interval after the removal of the load. The smallness of the spread of the arches was probably due to the fact
BRICK AND CONCRETE-METAL CONSTRUCTION. 83
that the floor had been built in the adjoining bays, and its stiffness was sufficient to prevent much sidewise motion of the arches in question. It is not likely that the bent tie rods would be very effi- cient in holding" the thrust, which must have been resisted prin- cipally by the sidewise bending- of the supporting beams and outer walls. The practice of bending tie rods in arches is certainly not to be recommended, and it is understood that, in accordance with the suggestion of the Building Department, the rods of the other floors of this building have been made straight.
84 ASSOCIATION OF ENGINEERING SOCIETIES.
Expanded Metal as Used in Fireproof Building Construction and Other Work.*
By William M. Bailey, Member Boston Society of Civil Engineers.
The object of this paper is to give briefly some information regarding the uses of expanded metal, and the results of a few tests made on expanded metal and concrete structures.
At intervals there have been submitted for the consideration of engineers and architects different combinations of plastic mate- rials and steel, and of concrete and steel, with the steel in the form of isolated ribs acting entirely in tension ; combinations where single rods are imbedded in the tension side of the concrete, and combina- tions of steel and concrete where the steel in continuous sheets is imbedded in the tension side of the concrete and acts also under transverse stress. Each of these methods claims to possess cer- tain advantages. The expanded metal system belongs to the latter class, in which the expanded metal acts entirely in tension and is distributed through the tension side of the slab or beam. The metal should be placed as far as possible from the neutral axis where its moment of resistance is greatest, and at the same time be thor- oughly imbedded in the concrete. In order to develop the full strength of steel it is also necessary that it should be held in place by some means possessing greater strength than the cohesion between the steel and the concrete.
Expanded metal is made from sheet steel cut with the grain, and expanded into diamond-shaped meshes, greatly increasing