Electrical aids to greater production

Preface

Eighty per cent, of the power used in making munitions has to be applied electrically. The Great War has brought to the engineer in the industrial plant, to the chief electrician of such plants and to the consulting engineers at work in laying out and designing the electrical equipment for industrial work, many new opportunities.

Emergency power needs have been supplied, additions and alterations to wiring systems to carry added loads, extensions have been built, all with the general idea of helping to increase factory output and hold down factory costs.

The war indeed has emphasized the inherent economy and flexibility of electricity as a method of driving all classes of machinery and has stimulated greatly the application of electricity for lighting and power.

This volume is written out of the experiences of the men who have been engaged in this work. Electrical World from week to week has presented articles on application of electricity to plants, taking up the problems of installation and maintenance as well as the problems of layout and control.

In this volume, the best of this practice has been assembled to provide for the work of reconstruction now upon us a background of practical suggestions to help install, operate and maintain electrical equipment in different classes of industries.

The material has been chosen and edited, not to make a text book, but rather a practical handbook of methods, schemes and plans which can be lifted out and adapted to a wide variety of conditions.

For the information presented, Electrical World is indebted to the cooperation of scores of electrical engineers in industrial establishments; where permitted, individual credit has been given to the men who together have met so successfully the problems of applied electricity during the war and whose work forms the basis for the practical application in factories to help increase output and reduce costs under the normal conditions of peace.

Chapter I General Power Problems Of Industrial Plants

INDUSTRIAL APPLICATIONS OF ELECTRICITY

If it were possible to state in just one word what the great advantage is that has created the universal adaptation of electricity to practically every known industry, it might be summed up in the one word "control," says Dwight D. Miller, formerly with the engineering department of the Society for Electrical Development, Inc. This is true since by means of control not only is the highest economy secured, but also increased production within a given time and of a quality higher than possible to attain by those other methods of power application in which the possible degree of control is only nominal by comparison.

Notwithstanding the fact that the electrical industry had its inception in the production of light, still, owing to the limitation of space allowed, this subject must be passed over with the statement that there have been many and large increases in efficiency in the various lamps invented and manufactured from the time of the first open-arc lamp down to the highly efficient gas-filled tungsten-filament lamp of to-day. Up to recently the cost of lighting had steadily decreased, so that it is possible to obtain many times the candlepower for the same energy consumption, or the same candlepower at a greatly reduced cost for energy consumed.

In dealing with the subject of heat, atmosphere, time and temperature are the three controlling and essential factors necessary

l for quality production in quantity, especially in those processes involving high temperatures. The fact that these three factors are more easily and accurately controlled through the medium of electric heat than is possible with any method of combustion heating makes it a heating medium so far superior to others as to offset in many instances its higher first cost. This is at once evident when we recognize that heat produced from electric energy is produced at 100 per cent efficiency and is accomplished automatically under fixed conditions, beyond the effect of human errors consequent to manual control, while the utilization of the heat of combustion devices involves a large number of variables all of which either involve the human element in their control or are beyond its power to correct. The heat of electric energy is peculiar in that it can be generated in any quantity regardless of temperature. This feature is unique and renders its utilization much more flexible and its control nicer than is the case where the heat of combustion must be utilized. With given fixed electrical conditions, such as line voltage and resistance of the leads, electrodes and resistor material, the same amount of current will flow, automatically producing the same temperature to an exact degree, since it is governed by Ohm's law. AVith this law the human element has absolutely nothing to do, because as long as the voltage and resistance of the circuit remain constant the same current must flow per se.

In general the ratio of efficiency of application of heat of combustion to application of electric heat becomes greatly in favor of the latter as the higher temperatures are reached, because electric energy is always transformed into heat at 100 per cent efficiency, regardless of the temperature, so that only the heat losses due to radiation, conduction and convection must be taken care of. In the case of combustion heating, however, it is the lack of control of the factors producing the heat itself which prevents perfect combustion and, combined with the heat losses just mentioned, renders its efficiency of utilization much less. In fact, it is by no means rare to find coal or even oil-fired furnaces to-day whose thermal efficiency is no greater than 1% per cent, which means that sixty-five times as much heat as is utilized in the useful work of heating is discharged into the atmosphere.

Much has been said regarding the high cost of electric heat — that it is much, more expensive than the various forms of fuel. This is true when viewed from a B.t.u. basis only. The crux of the whole matter, however, lies in the fact that the cost of heat energy alone, as compared with the entire cost of the finished product, is in many instances negligible. Many items enter into the total cost of production, of which heat energy is only one; so that, while electric heat may be more expensive, if by its use the other items (such as time required, labor, fire insurance, etc.) are cut in greater proportion, producing greater quantity as well as improved quality, it is evident that not only is electrically generated heat cheaper to use but also that its use is imperative in order to compete successfully with those using it in similar processes.

Probably no more striking and forcible example of the saving of both- time and money effected by the use of electric heat can be found than in the case of repairing the interned German ships. Although there was a total of 109 ships damaged, which, if new cylinders and parts had had to be supplied, would have taken eighteen months to two years to repair, all these ships were placed in service in less than eight months by the use of electric welding. The estimated cost of repairs on the first ship amounted to $32,000, and the time required from ten to twelve months for completion. By means of electric welding the work was completed in fifty- two hours at a cost of less than $2,000 for the actual work done. Moreover, the cylinders withstood a test of more than 50 per cent in excess of their normal working pressure, although it is customary to test them up to an excess pressure of only 20 per cent. In many cases an electrode high in manganese was used which in itself supplied the proper tensile strength to the weld. Thus repairs were easily made in places which would have been extremely difficult, if not entirely inaccessible, had a method of welding which required a flux been employed.

Spot Welding Used Extensively. Another case in point is the manufacture of the all-metal automobile bodies by means of spot and arc welding. Indeed, were it not for the ease and rapidity with which welds are thus made, together with the strength obtained, many manufacturing processes which involve a complete and oil-tight junction of metals would be commercially impossible, the stock being too light and thin to permit of riveting successfully. In manufacturing small articles like window-sash pulleys, as is done at the American Pulley Company, Philadelphia, by spot and projection welding, many thousand welds are made per hour — in fact, just as fast as the operator can press a lever, demonstrating in a most striking manner both the flexibility and ease of control of the electric welder. Ship plates are pinned to the frames of the vessel by spot welding and later on are welded along the edges, practically fusing the plates into one another. In both of these applications heat is developed at the exact spot, to the exact degree and for the exact length of time only to effect a perfect junction of the metal. Where can you find a fuel-fired process so simple, so complete and so efficient in utilization of heat?

The practice of heating by induction is rapidly coming into use. In this case the material to be heated forms the short-circuited secondary of the transformer by which it is inclosed. While this method of heating is probably the most efficient of all now in commercial use in its practical application, it can only be used in connection with materials of uniform cross-sections, because with an uneven cross-section part of the piece may become superheated or even burned before the other part attains the desired temperature.

Industrial Heating. Lieut. Col. C. F. Hirshf eld, when head of the research department of the Detroit Edison Company, made some very interesting experiments with internal heating in connection with the baking of "japans." He says: "It is of particular interest to note that baking by internal heating is essentially an electrical method, and that it is far removed in every way from methods previously in use." In his paper on "Low Temperature Electro-Thermal Processes" he clearly demonstrates, by means of micrographs, that the surface coats of japanned articles baked by the heat radiated from electrical airtype heaters possess a much higher and more perfect gloss or finish, that they are denser, freer from crater holes and will weather much longer than is the case with those baked by hotair convection currents of combustion heating. Moreover, the time of bake was reduced to two hours and forty minutes for the electric compared with five hours and thirty minutes for the combustion method.

He next experimented with inductive or internal heating as against electrical radiation and found that better results could be obtained with a bake of fifteen minutes and at a temperature of 338 deg. Fahr. (170 deg. C.) by internal heating than could be secured by means of external electric heating (radiation) using a temperature of 446 deg. Fahr. (230 deg. C.) for fortyfive minutes. He says : "It seems probable that one coat baked in this way will prove the equal of two or three baked by the older methods. The effect of all this upon energy charges for a given weight of metal baked is perfectly obvious."

In view of the superior results noted above it is unfortunate that induction heating cannot be universally adapted to the baking of japanned articles. However, it is being successfully used in heating metal tires for wagons and rims for large automobile trucks, since in these cases the cross-sectional area is uniform. It is also being tried out in connection with electrically heated boilers. In this case a hollow brass casting forms the short-circuited secondary of the transformer and heats the water as it flows through. The casting is connected to the boiler in a manner similar to a gas hot-water heater of the circulation type.

By the use of automatic devices such as time elements with solenoid switches, etc., ovens can be automatically controlled and brought up to temperature before the operator arrives in the morning, so that there is no time lost in starting the day's work, or the bake may be completed and power shut off after the quitting time of the operator at night.

Many other examples can be given showing the advantages of electric heat in low-temperature processes, such as its use in connection with linotype melting pots, glue pots and hot tables of various kinds. Here the heating units are small, compact and easily so adjusted that heat is applied exactly in the location desired and accurately controlled either manually or automatically by the many devices already perfected for this purpose.

Electric Furnaces. Through the medium of the various electric furnaces now being rapidly installed by progressive companies, the entire metallurgical industry is much benefited. By the use of the electric arc the temperature range above zero has been practically doubled and made available for commercial uses. This has not only opened up a wide field for development in the electrochemical industry but has also already resulted in the commercial production of materials heretofore unobtainable or previously unknown, such as aluminum, calcium-carbide, carborundum and artificial graphite.

On account of the great heat developed in the electric furnace, reactions take less time and are more complete, hence the yield for a given time is increased. Because of the fact that the heat of the electric furnace is not dependent upon combustion, and can be used in a neutral or reducing atmosphere, it is a "clean heat, ' ' in that it is not contaminated by the various products of combustion. Thus both the time lost and the expense incurred in using deoxidizing agents are, to a great extent, done away with and the product is of a higher quality.

Not only has the electric furnace made tremendous strides within the past ten years in the steel industry both in connection with the melting and refining of steel and in its heat treatment, but it is now rapidly establishing itself in that other great allied branch — the non-ferrous field.

Many books have been written and the technical press for the last three or four years has contained a multitude of articles on the advantages of the electric furnace. Briefly, the whole subject may be summed up by saying that the use of the electric furnace enables commercial practice to approach very nearly the scientific accuracy of the laboratory, thus insuring not only certainty of production and duplication of results, but also production of a quality higher than can be commercially obtained by the use of combustion heating.

THE POWER PROBLEM OF THE MANUFACTURING

PLANTS

Although power is an important factor in production, it receives very little consideration compared with other factors, points out Sydney Fisher, an electrical engineer who has been connected with large manufacturing companies in England and with two major war industries in this country. Power must be available in sufficient quantity when required, and its supply must be unfailing. Production must never be held up for power; in other words, power must be ever ready for production. These exacting requirements can be met in modern plants with electric service, and yet the cost of this vitally important factor in production does not amount, in many cases, to more than a few mills per unit of product. This has been made possible by the remarkable development of electrically operated equipment in late years.

Not only in the supply of motive power and power for lighting has electricity simplified production, but also in its application to production processes. Temperature control, so important in delicate heat-treatment operations, is a reality, and losses due to radiation, etc., are very small. The electric welding machine is used not only for welding, where it has eliminated many operations, but also in delicate heat-treatment operations where high local heating is required. It is also used in heating and clinching rivets, these operations being performed together. Electric plating and cleaning baths have greatly simplified operations which heretofore were difficult and expensive. The battery truck has made rapid transportation over short distances possible with economy in time and help. Scientific heat treatment has been made possible by the development of the thermo-electric couple for pyrometry. The telephone, the telecall, the fire alarm, all play a very important part in plant operation.

Efficient Operation and Reliable Service Chief Considerations. Reliable equipment is only one part of the problem, however — a very important part, to be sure, but not the all-important part. Enough power and continuity of service form the prime consideration of the power engineer, but over-equipment in any part of the system will result in poor operation and unreliability when the plant is in full swing. Efficiency and continuity of service can only be obtained through scientific selection and arrangement, careful installation and operation, and proper maintenance of scientifically designed reliable equipment.

The following suggestions, based on two years' experience in power work at one of the largest munition plants in this country, if not the largest, may be helpful to those engaged in present and future power work. Suggestions will be offered under the following headings: (1) organization, (2) selection of equipment, (3) inspection, (4) installation, (5) operation, and (6) maintenance.

The power engineer and the production engineer of a munition plant, or, in fact, any manufacturing plant, should each be responsible to the chief engineer. On no account should the power engineer be responsible to the production engineer. The production enginer is always afraid of an insufficiency of power. If allowed to have his way, complications will ensue.

Selection of Equipment. Generating equipment rated at 2300 volts, three-phase, 60-cycle, with 440-volt power and 110- volt lighting equipment, is without question the best system for industrial plants, in the writer's opinion. This is true from the initial-cost, operating and maintenance standpoints. The selection of generating, controlling, transmission, transforming and distributing equipment should be based on the assumption that a high motor load factor (90 per cent) will be maintained where possible and that the necessary synchronous apparatus will be installed at the load to bring the power factor up to 80 per cent at the transformer stations. This will result in the correct design of all branches of the system, insure subsequent efficient operation, reduce the possibility of breakdown to a minimum and reduce the cost of equipment.

Careful selection of motor equipment can be made without a large expenditure of time and money. Elaborate test equipment is not necessary. A young electrician carefully instructed and provided with several ammeters (0-15 amp., 0-75 amp. and 0-150 amp.) and with a suitable voltmeter can do all that is necessary. Records should be made of the minimum, average and maximum currents and the order and frequency of their occurrence. All peculiarities of the work cycle can be expressed in terms of current. The corresponding power output values can be obtained from a current-horsepower output curve plotted from manufacturer's data on efficiency and power factor at various loads.

The rated output of the motor should equal the average load demand. Peak loads not exceeding 150 per cent rated load and occurring at intervals for short periods may be taken as an overload. This apportionment of motor to load will insure a power factor of 80 per cent. The first two or three motors will have to be selected by well-based guesses. After tests have been made on these units the results can be used in making more scientific selections of the other units. At the plant on which the writer bases most of his opinions 400 motors aggregating 6000 brake-hp. were selected in this way. Careful study of the work cycle often results in the coupling of two drives on one motor with resulting adequate power for each and a high motor load factor.

When the load is intermittent and fluctuates, as in the case of drop hammer and heavy press drives, a high average load and consequent high power factor is unobtainable. In such cases use should be made of a synchronous motor fan or blower drive requiring sufficient reactive power to raise the power factor to 80 per cent. Where possible reactive power should be supplied at the load, thus increasing the generator, transmissionline and transformer capacity for useful average power and reducing equipment and transmission losses. The 2000-kw. turbo-generator unit is a good unit for industrial plants. Where the space is not too limited two such units are advisable, one of the bleeder type and the other of the mixed-pressure type, as they make the best use of low-pressure steam during winter and summer months respectively.

Control apparatus is pretty well standardized. In addition to standard exciter, generator and feeder panels, a station recording voltmeter, a power-factor meter, a voltage regulator and a ground detector (three-phase) will be found necessary. Power-limiting reactances are not a necessity even with timelimit relays, as the reactance of modern generators is sufficient to limit the current of the usual short circuit.

Combined turbine, motor-driven exciters are to be recommended for munition plants. Under normal conditions of operation the exciter is motor-driven. Should the speed of the motor drop below 95 per cent synchronous speed, the turbine automatically takes the load. This insures sufficient power for the station lighting in the event of a shut-down.

Fiber duct gives very good results for underground transmission. Manholes should not have perforated covers, should be shaped to the lay of the cable and should be made thoroughly waterproof. Should a circuit pass near furnaces or heated area, it should be run through a tunnel opening into a well-ventilated manhole at each end. Overhead transmission is less expensive and quickly installed but is easily tampered with.

Value of Several Motors to Each Machinery Group. Motor equipment should be selected on the basis of two or more to each group of machinery. This arrangement is more expensive, but is preferable for several reasons. For instance, a high motor-load factor is more easily obtained, a 42-hp. average load being better supplied by three 15-hp. motors, or one 20-hp. and one 25-hp. unit, than by one 50-hp. motor. Obviously when power requirements are uncertain and quick deliveries of small sizes are possible, a number of smaller sizes is better than a few large sizes. Furthermore, if the motor equipment is reduced to a few standard sizes (5 hp., 10 hp., 15 hp., 20 hp. and 25 hp.) fewer " spares" are required and the expense is less, the units being smaller.

With this arrangement, if many machines are idle or the duty is light, whole sections can be run on one of the motors, the others being disconnected. Another advantage of this arrangement, especially in a plant just being built or extended, is that operation does not have to be delayed by deliveries of equipment. If the generator capacity is small owing to slow delivery of units, loading up one motor in the section instead of having two or three running lightly loaded will relieve the station units of unnecessary reactive power load and hence increase the station capacity for the average power load. In the writer's experience a 20-hp. motor has taken the load of an entire group (33 hp.) for two hours, with the aid of an ordinary desk fan to keep it cool, while another motor in the section was being replaced. This is another reason why there should be more than one motor driving the group.

Money spent on circuit breakers to isolate circuits is by no means wasted. A short circuit at some remote point will shut down an entire feeder, perhaps the plant, unless some precautionary measure is taken. Overload relays are not desirable on individual motor circuits, however, unless steps are taken to study the work cycle and set them for the maximum current. Furthermore, they also must be inspected frequently, otherwise they will trip and shut down a group of machines, causing unnecessary delay. If a motor is carefully selected and fused for the maximum current, there should be no trouble. A 440-volt circuit is advisable for motor applications, as the copper for a 220-volt circuit is expensive.

In the opinion of the writer the incandescent lamp is best for lighting, 60-watt and 100-watt units providing general illumination being preferable for production work and 25-watt or 60- watt individual lamps for tool and assembly work. Vapor lamps, while they possess advantages as regards quality of light, are easily damaged and the maintenance is high.

Inspection and Installation of Equipment. Standard apparatus, such as motors, transformers, control equipment, etc., as supplied by reliable firms, are carefully inspected at the shop. Frequently, however, machines built to supply a less urgent order are supplied, and while they may be identical in design, they have different characteristics. In the writer's experience, three exciters specified for parallel operation were subsequently found to be over-compounded, flat-compounded and under-compounded respectively. The adjustment could have been made very easily at the shop but involved considerable time and expense after installation.

Tests for grounds in the fields of generators should be conducted. If the system is installed on contract, the layouts should be studied carefully and the sizes of bus copper and cable from generator through to motor should be checked. It is surprising how errors creep into a mass of detail. Occasionally 300-kva. transformers may be accidentally installed for 500-kva. service and the error not detected until the plant is in "full swing"; then the tar begins to drop and the bus copper changes color. Contacts of circuit breakers should be inspected with a thickness gage to detect poor contacts before they cause trouble.

While cable purchased from a reliable firm is guaranteed for a year, the reels should be meggered before and after being drawn through ducts. A megger test set is expensive, but it will be found invaluable in locating defects and ascertaining the condition of equipment. Transformer taps should be carefully checked, as phase reversal may cause considerable trouble when two transformer houses are tied together. While awaiting installation do not allow transformers to remain in the rain uncovered. The air gap and oil rings of motors should be inspected and the rotor should be tested to see if it binds. Compensator contacts should be inspected, as three-phase starting and single-phase running, due to a bad contact on the running side, is by no means uncommon.

The installation of generating, transmission and transforming equipment is usually and preferably placed in the hands of contractors. Curves showing daily progress in all branches of work should be plotted on one sheet and the contractor consulted to ascertain the cause of delay in any branch of the work. Installation should be constantly checked from drawings as defects do not come to light until the plant is in full operation, by which time the bills may be paid.

The power engineer should consult with the machinery layout department to determine the best grouping of machines from a power standpoint, and to eliminate short double-cross belts where possible and the arrangements which require excessive starting currents and needless constant expenditure of energy in overcoming friction. Sometimes chain drives are advisable, as they will transmit overloads. Motors are frequently regarded as underrated because the main drive of a belt, particularly on a damp day, is very inefficient. Excessive belt tension is frequently the cause of a seized motor bearing. A. motor should be given a central position relative to the group of machines which it is required to drive, and the motor pulley placed under a girder if possible.

Operation of Equipment. Instruction cards should cover the operation and maintenance of every piece of equipment in the plant. No doubt should be left in the mind of the operator. Rules for starting, stopping and oiling should be very complete. Rules giving the method of procedure in case of shut-down can be drawn up to cover nearly every possible condition. A complete set of instruction cards will prevent shut-down, shorten the period of shut-down and place responsibility on the right person. A comprehensive set of signals (whistles and colored lights) should be in operation in the station, covering the starting and stopping of the main units and auxiliary apparatus.

Voltage regulators are a boon, but they fail sometimes. They may operate satisfactorily twenty-four hours a day for six months and then fail, causing the station to lose the load. Once in six months is once too often when a 10,000-hp. load is dropped and about 25,000 men are forced to be idle. At the plant where the writer is engaged periodic shut-downs were experienced until the regulator was made semi-automatic. If the regulator fails as now adjusted, the station voltage drops only to a certain value, which insures against dropping the load. This is done at a sacrifice of the automatic feature whereby the voltage is maintained constant under all conditions of load ; hence the operator must adjust the generator and exciter fields when the load "goes off" and "comes on" at recess periods to keep the regulator on the line.

The field excitation of each generator should be adjusted so as to maintain the same power factor in each unit, as under this condition the station capacity will be a maximum. In 'some cases machines operate better at a lower or higher power factor. Sometimes it is desirable to raise the average power load of a bleeder turbine in order to obtain as much low-pressure steam as possible. Another precaution to take is to keep tie switches open when it is not necessary to have them closed, as the fuse capacity is doubled and the damage due to short circuits is thereby increased when they are closed.

Operators should be instructed to start motors with quick decisive motion. "Hobbing" should be discouraged, especially when belts are being put on. If the proper compensator taps are used, the acceleration will be such as to permit applying any belt without danger to the operator.