Iron and Steel ProductionAnnual Report of Committee on Applications to Iron and

Steel Production*F. B. CROSBY, Chairman

To the Board of Directors: 6600-volt, 60-cycle, turbo generators to supply powerTo anyone who has followed closely from its in- for the plant. Steam will be obtained from blast

significant status at the beginning, on through the first furnace gas and powdered-coal-fired boilers designed forand into the second quarter of this 20th century, the 300-lb. pressure at 180 deg. superheat.application of electricity in the iron and steel industry, There is no question but that blast furnace gas shouldthe steady growth to its present gigantic proportions has be used as efficiently as possible and wherever possible,always seemed inevitable, though none the less amazing. before any other fuel is considered. Considerable

In some respects, the year 1925-26 has seen all economies can yet be made in the use of gas for heatingprevious records broken in the rate of electrification. blast furnace stoves. This will leave more gas avail-The applications of electric power have become so able for the generation of power, either through gasdiversified that it renders entirely out of the question engines or boilers and turbines, for the productionmore than the briefest outline of outstanding features of steam for plant uses, or when mixed with coke-ovenin the developments of the past year. gas, for use in heating furnaces throughout the plant.

I. GENERATION OF POWER Coke-oven gas finds a ready application in practicallyevery heating, reheating and annealing furnace opera-The steam turbine continues to prove the most tion in the plant, but where a large city offers a ready

reliable of prime movers in the steel plant power station. market, it is often necessary to restrict its use in theWith the increased economies in boiler room practise, steel plant to effect an economic balance between citywith blast furnace gas as fuel, and the further use on the and plant consumption.mills of cooling water from the condensers, the pro- The steel industry is still looking to the central sta-duction costper kw-hr. from the turbine driven generator tions for an answer to the question of pulverized versusclosely approaches that of the gas engine. Coal or oil solid coal. In this field the opinion is prevalent thatcan be used as auxiliary fuel supplementing the supply powdered fuel research and application are in theof blast furnace gas and thus avoiding delays which may incubation stage and that developments in the neararise due to shortage of gas during periods of castings or future may revolutionize present standards of boilerfurnace repairs. practise.The thermal efficiency of the gas engine is very at-

tractive and where an ample supply of blast furnace gas II. DISTRIBUTIONis available this prime mover finds warm support. Five Many steel plants have reached and passed thenew installations of gas-engine-driven blowers, and one economic limit of 2200 volts for distribution. The largegas-engine-driven generator are reported for the current powers often required result in prohibitive currentyear. values at this voltage. This is reflected in excessiveThe ideal arrangement appears to be a combination of costs of protective oil switches and line losses even in the

steam turbines, gas engines and purchased power, with relatively short transmission distance from the loaddependence upon the gas engine and central station center to the numerous mill motors.for the base load while the turbines float on the line A distribution voltage of 6600 has become quite usual,carrying the peaks. Under these conditions a large so that only in the smaller plants, and in some casesblock of power can be purchased at favorable rates where power is purchased, is 2200 volts standard. Theowing to the comparatively low maximum demand increasing loads in the larger plants are taxing even thecharge, especially if hydropower happens to be 6600-volt systems, but, so far, only one plant is re-available. ported as having main roll motors fed directly from aOne steel company which is putting through a 13,200-volt system.

complete electrification program of old and new mills III. MAIN ROLL DRIVEis building a modern power plant with two 12,500-ky-a., Many of the mills laid out previous to the advent of*Committee on Appliceations to Iron and Steel Production: the steel mill motor, now, each year, are reaching a point

F. B. Crosby, Chairman, M\organ Construction Co., 15 Belmont St., where, because of competition with recent equipmet

A. C. Cummins, A. G. Pierce, G. E. Stoltz, it is necessary to throw them out or re-build them so farW. C. Kennedy, A. G. Plchue, J. D. Wright. as possible along modern lines. The first consideration

Presented at the Annubat Convention of the A. I. E. E., at is usually the replacement of the original engine by aWhiate Sulphusr Springs, June 21-25, 1928. suitable motor and control.

902

June 1926 IRON AND STEEL PRODUCTION 903

One electrical manufacturer reports the sale of an scheme first suggested by them in 1922 and nowaggregate of 33,270 h.p. of motors replacing engine generally adopted.drives during the past year. During this period This same electrical manufacturer also reports a newthe company has installed and placed in operation tonnage record for electrically-driven blooming mills31,000 h. p. (continuous rating) of reversing-mill made by a 40-in. mill, driven by one of its reversemotors and has taken orders for six additional reversing equipments; namely 90,175 tons of ingots rolled in oneequipments aggregating 24,600 h. p. Three of these six month. A repeat order duplicating the electricalunits are replacing engine drives of existing mills, equipment was obtained for a 46-in. mill, using a motorwhile two are for new mills which are to replace engine rated 7000 h. p., 50 to 100 rev. per min.driven mills. Another of its installations of especial interest is aNotable among the reversing equipments installed 9000-h. p. unity power factor, 107-rev. per min.,

during the year are two 7000-h.p. motors, the largest 6600-volt, 25-cycle synchronous motor which, from thesingle armature machines thus far built for this service. standpoint of continuous h. p. capacity, is the largestAn 8000-h. p. unit of slower speed but nearly 50 per cent motor of any type used for industrial purposes in thelarger in physical dimensions is, however, nearing com- United States or, so far as can be learned, in any otherpletion in the factory. country. It is also notable in that it is the first really

Developments in the frequency converter type of large synchronous motor to be used for driving a rollingalternating-current adjustable speed drives provie . mill. The motor may be started, stopped, or reversed

alternationg-cur nt,adjustabl ese ddr esov for from a master switch exactly the same as any otheroperation at constant torque above andt below syn- typ ofrligml oo.TeKrdre ytmochons. Thi meho of spe.dutetrqie type of rolling mill motor. The Korndorfer system ofchronism. This method of speed adjustment requires control is used and the complete operation of starting ononly two rotating machines,-the main motor and the the low voltage tap of the auto-transformer, switchingfrequency converter,-both on the same shaft. The to a higher tap, applying field at the correct time, and

slip energy of the induction motor is changed to linefrequency in the frequency converter and returned tothoignteln,isakncrofuomialyfrequency in the frequency converter and returned to In the design of the motor, particular attention has beenthe line through speed adjusting transformers. Three g t ounits of this type, one of 770 h. p. and two of 1600 h. p. teriti the exa for thetmotorqfe isdriveeach,~~ar*oeigbit teristics. The excitation for the motor field iS derivedeach, are now being built. from a separate motor-driven exciter.A 5000-h. p., 99-rev. per min., 60-cycle, inductionfrmaspatmor-ivnece.One of the best examples of motor drive for so-called

motor built for a continatious billet mill drive is of tandem mills was put in operation about the first of theinterest particularly in that it is designed for 13,200- year. Practically every stand is driven by an in-volt operation. Heretofore, except in one instance . . d(see Report for 1925) main-roll motors have not been divid aldirct rrnt motor-generator sets; a widebuilt for voltages above 6600 as it was thought that

range of speeds is obtained by a combination of genera-insulation troubles on higher potentials would be ag_-o otg n otrfedcnrl

gravated by the dirty atmosphere and conducting dust Tor vaggegan moto oficthro lusually found in steel plants. The aggregate capacity of the several motors drivingThe necessity of maintainin constant seed relation this mill amounts to 15,850 h. p. (40 deg. cent.) The

yetween the g d oll l electrical apparatus is located in the best possible sur-between the several driveslofmen anemmills ha roundings, emphasizing the growing importance which

the mill operators are assigning to the electrical part ofcontrol for compound wound, adjustable speed, direct- their equipment.current motors. This involves a series exciter and avariable potential field rheostat mechanically con- While the cost of such an elaborate drive is relativelynected to the main shunt field rheostat, with resistance high, the equipment is, on the whole, very economical;so proportioned that the series excitation is of the the flexibility and the wide speed range permit of rollingcorrect value to give very nearly zero speed regulation on this mill a great variety of products which wouldat any speed setting. This method of control is being otherwise require at least two separate mills of a lessapplied to a 10-in., semi-continuous, merchant mill in flexible type.three sections which are driven by 1000-, 1200- and The following tabulation includes only main mill2000-h. p., d-c. motors respectively. motors on a continuous rated basis, in units above 300Another electrical manufacturer reports unprece- h. p. as reported by the three principal electrical

dented activity in its steel mill business for the past manufacturers in this country, up to 1st May, 1926.year with an aggregate h. p. rating of mill motors sold___________from 1st June, 1925 to 1st May, 1926, of 102,910 h.p. i.923 1924 1925 1926This company also reports placing in operation a 60-cycle ..|452840 |478390 |543440 |5864404000-h. p. reversing drive in which the single motor 25-cycle ........ .475825 490225 538450 582430iS suppliedl from a fly-whneel motor-generator consisting Drc-urn . 960 346 360 506of two 750-volt generators permnanently paralleled, a 11228335 11293475 115i2500 11698930

904 IRON AND STEEL PRODUCTION Transactions A. I. E. E.

IV. AUTOMATIC CONTROL of these anti-friction bearings is to increase the freeThe year 1925 showed great activity in the applica- running speed of bridges and trolleys and the light

tion of automatic control to cranes and auxiliary mill hook hoisting speeds. This imposes a greater respon-machinery. Its dual functions of control and protection sibility than ever before on the control equipment toare now universally accepted so that there is now little protect the motors and gearing in plugging and empha-opposition to its general use. Although there were no sizes the necessity for reliable brakes and limit switchesnew developments of remarkable importance, a most for the hoists. Brakes on the trolley motors, hithertointeresting feature was the rapidly increasing use of the rather unusual, would appear to be necessary on ainductive time element control system. trolley equipped with roller bearings. In some cases

This system of control was commercially introduced the hoist control will need to provide some means ofin 1924 by one manufacturer and shortly afterwards a limiting the light hook hoisting speed.similar system was brought out by another. The Automatic control of the electro-pneumatic type isessential features of these systems of control are: being applied to the control of two 275-h. p., compound-(1) the short circuiting of accelerating resistance within wound motors in parallel for the drive of a large blooma definite time, regardless of the load, and (2) the shear. The cycle for this machine requires a completesecuring of a time interval purely by electro magnetic operation in about six seconds and the pneumaticallymeans. In the first system, the time interval is operated contactors of the large capacities involved aresecured by making use of the transient voltage induced much faster and more positive in action than magneticin a transformer or "inductor" due to changes in the contactors of similar capacity. The electro-pneumaticmotor current. In the second system, use is made of contactors are assembled in steel frame work, and makethe slowly decreasing magnetism of shunt-wound a more compact and sturdy controller than the usualrelays when their coils are short-circuited. Both contactors mounted on slate or other insulating panels.systems fill a long-felt need. Theoretically, current- V. AUTOMATIC SUBSTATIONSlimiting control provides a valuable protection to themotor. Practically, the protection actually afforded in te us of automaticallycontll substations inmany instances is almost nil since the current-limiting steel plants has increased very greatly since the firstrelays must be adjusted to start the motor under the installation in 1924. An installation recently put intohelav mest loadjwhich may bee otounted operation provides for the automatic control of twoheaviest load which may be encountered. withncurrent-limiting control, therefore, the motor starts 1500-kw. synchronous motor-generator sets and ofslowly under heavy load and quickly under light load twelve 4000-ampere, d-c. feeders. This automaticslwl une heav loa an qucl une lih load, equipment iS in a substation with several large revers-in either case subjecting the motor to excessive current. eipment is wi as tationt sallarpreversOn the other hand, time-element control imposes ex- ing mill drives with an attendant always present, butcessive current on the motor only when the motor has It was felt that the more reliable operation was ofan excessive load to accelerate and thus gives the motor s v t w tmuch better average protection. equipment just the same. Several other installationsAlthough the larger portion of these installations are being made for the automatic control of motor-

has been for the control of mill tables and other auxil- generator sets and a-c. and d-c. feeders.iary drives, a very considerable number has been VI. YARD ELECTRIFICATIONinstalled for the control of open-hearth charging The Diesel electric locomotive of which specialmachines, soaking-pit cranes and standard cranes, mention was made in this report last year has grownparticularly for the bridge motions. Installations rapidly in favor as experience has demonstrated itsof particular interest include a dynamic lowering possibilities. Larger sizes up to 60 tons or more arecontroller for a bucket hoist and an ore-bridge trolley now available and with their proved economy andcontroller. Recent installations placed in control reliability appear to have successfully solved the dan-rooms entirely separated from the mill proper with gerous problems of third rail or overhead trolley in thecontrol panels mounted in continuous switchboards, steel plant.resistors mounted overhead in tiers on structuralsupports, with foot walks between, and with ample VII. ILLUMINATION OF YARDS AND BUILDINGSprovision for ventilation, mark the growing appreciation This past year has seen a marked impetus in theof the fact that proper and substantial installation increasing recognition of the value of good lightingcontributes probably as much as first class equipment in mill buildings and yard. More attention has beento continuity and economy of operation. given to the specific requirements of different kinds ofA very interesting development of the past year mills and to the different operations within a given

which will surely have an important effect on crane mill.econtrol is the increasing use of roller bearings. One The kw-hrs. required for lighting range from 10 tolarge installation has been made of cranes equipped 15 per cent of the total powerloadandareanappreciablethroughout with roller bearings even including the item in the total cost. More efficient lighting unitssheave bearings in the hook block. An obvious effect have been developed of larger wattage yielding more

June 1926 ELECTRICITY IN MINE WORK 905

light per unit current consumption and, incidentally, The initial installation consists of two motor-genera-requiring less time for cleaning. tor sets, each delivering 600 kw., single-phase, 1875

VIIT. ELECTRIC HEATING volts, 480 cycles, to six Northrup high-frequencyThe use of electricity forheatingisfurnaces, each generator being driven by a 3-phase,The useof electricityforheatingisincreasingrapidly 60-cycle, 2300-volt synchronous motor, with direct-

in a great variety of applications. One instance of connected exciter. To compensate for the low powerespecial interest is the heating of ingot hot tops. factor and obtain best circuit conditions, a bank of

Early in 1925 an equipment was installed for heating capacitors is included with each furnace.the tops for ingots,-primarily of monel metal and Last fall, the equipment for the first three-voltage-nickel. Before using this equipment, 3800 lb. of metal control arc melting furnaces was sold. Thesewas poured to obtain a 3000-lb. ingot, the waste averag- equipments are used with six-ton, three-electrodeing 20 per cent to 30 per cent. Now 3250 lb. of metal furnaces, one originally installed with a 1200-kv-a.are poured and 85 per cent of the ingots are used with bank of transformers and the two others with a 1500-very little cropping while a large percentage of the kv-a. bank of transformers.remaining 15 per cent is worked into commercial Each new equipment consists of a 2550-kv-a. bankproducts. of transformers which will deliver full output at 165,The electrical equipment consists of one 1800-kv-a., 156 or 147 volts and a lower capacity at 138, 120, 95,

three-phase transformer designed to supply power to 85, 80 or 70 volts. Air core reactors of 25 per centthe ingot heating equipment and also to serve as a capacity for connection in the 11,500-volt circuit,spare for a six-ton arc melting furnace. Other equip- together with suitable switching equipment, were alsoment consists of one 10-per cent, three-phase, air core includedreactor for use in the 2200-volt circuit, instrument and The melter has a choice of several voltages to startcontrol panel; also six automatic, single-phase, electrode the heating, probably using 2550 ky-a, at 165 or 156regulating equipments for controlling the input to the volts, 2400 ky-a, at 138 for the intermediate voltagearcs used to heat the top of the ingot. and a still lower kv-a. at the refining voltage,-prob-

IX. ELECTRIC FURNACE ably 85 or 90 volts, depending upon the furnaceLast December, several units of the first commercial equipments.

installation of Northrup induction furnaces operating Marked economies are effected in furnace operation,at 480 cycles were put in operation. This particular especially from the standpoint of the life of the sideinstallation was made for melting nickel silver and walls and roof, together with possible reduction insimilar alloys, but these equipments have many pos- electrode consumption.sibilities in the heating and melting of ferrous metals In conclusion, I wish to give full credit to the membersand alloys, several applications being under considera- of this committee for their effort as individuals intion at present. gathering the data which forms this report.

Electricity in Mine WorkAnnual Report of Committee on Applications to Mining Work*

F. L. STONE, ChairmanThe Committee on Applications to Mining Work has I think that no mine operator who is contemplating

done very little constructive work during the past year. the opening of a new mine would consider any otherFrom the nature of things, the committee can only method of drive.watch the development of the use of electric power in In coal mines there always exists the hazard ofmines. This use is becoming more general every year explosion from gas, and in the bituminous mines fromand electric motors are supplanting every other kind of both gas and coal dust. These explosions have de-motive power. This is due, of course, to their higher stroyed hundreds of lives and ruined millions of dollars'efficiency and flexibility of control, combined with worth of property. The operators consequently arethe fact that they are just as reliable, if properly de- making strenuous efforts to eliminate the initial causesigned for mine use, as any of the other forms of drive, of such explosions.

*Committee on Applications to Mining Work: A small percentage of these explosions has beenF. L. Stone, Chairman, General Electric Co., Schenectady. N.Y~. traceable to the electric arc. After such anl explosionW. C. Adams, G. M. Kennedy, Charles Hi. Matthews. ha ocurd al trcso-t nta asr salM. C. Benedict, R. L. Kingsland, D. C. McKeehan. hsocre,altae flS1ta as r salGraham Bright. A. B. Kiser, W. F. Schwedes, obliterated. Consequently many explosions have beenH. W. Eales, Carl Lee, W. A. Thomas, atrbtd fo h ato ete xlnto,tL. C. Ilsley,' John A. Malady. C. D. Woodward. atlue,frtewn fabte xlnto,t

Presented at the Annual Convention of the A. I. E. E., electric arcs, without any real justification.White Suhlphur Springs, W. Va., June 21-26, 1926. The hazard, however, does exist and it is entirely