Each kind of power requires its own special machinery so constructed and adapted as to utilize it; hence, to be serviceable to mankind, electricity demands machinery suited to its nature; what that is, will be indicated in the following few paragraphs. Electricity is a name derived from the Greek word electron—amber. It was discovered more than 2,000 years ago that amber when rubbed with a Fox’s tail possessed the curious property of attracting light bodies. It was discovered afterwards that this property could be produced in a dry steam jet by friction, and in A.D. 1600 or thereabouts, that glass, sealing-wax, etc., were also affected by rubbing, producing electricity. Whatever electricity is, it is impossible to say, but for the present it is convenient to consider it as a kind of invisible something which pervades all bodies. While the nature and source of electricity are a mystery, and a constant challenge to the inquirer, many things about it have become known—thus, it is positively assured that electricity never manifests itself except when there is some mechanical disturbance in ordinary matter, and every exhibition of electricity in any of its multitudinous ways may always be traced back to a mass of matter. Note.—The great forces of the world are invisible and impalpable; we cannot grasp or handle them; and though they are real enough, they have the appearance of being very unreal. Electricity and gravity are as subtle as they are mighty; they elude the eye and hand of the most skillful philosopher. In view of this, it is well for the average man not to try to fathom, too deeply, the science of either. To take the machines and appliances as they are “on the market,” and to acquire the skill to operate them, is the longest step toward the reason for doing it, and why the desired results follow. Electricity, it is also conceded, is without weight, and, while electricity is, without doubt, one and the same, it is for convenience sometimes classified according to its motion, as— 1. Static electricity, or electricity at rest. Other useful divisions are into— 1. Frictional and And into— 1. Static, as the opposite of There are still other definitions or divisions which are in every-day use, such as “vitreous” electricity, “atmospheric” electricity, “resinous” electricity, etc. Static Electricity.—This is a term employed to define electricity produced by friction. It is properly employed in the sense of a static charge which shows itself by the attraction or repulsion between charged bodies. When static electricity is discharged, it causes more or less of a current, which shows itself by the passage of sparks or a brush discharge; by a peculiar prickling sensation; by an unusual smell due to its chemical effects; by heating the air or other substances in its path; and sometimes in other ways. Current Electricity.—This may be defined as the quantity of electricity which passes through a conductor in a given time—or, electricity in the act of being discharged, or electricity in motion. An electric current manifests itself by heating the wire or conductor, by causing a magnetic field around the conductor Note.—Statics is that branch of mechanics which treats of the forces which keep bodies at rest or in equilibrium. Dynamics treats of bodies in motion. Hence static electricity is electricity at rest. The earth’s great store of electricity is at rest or in equilibrium. Radiated electricity is electricity in vibration. Where the current oscillates or vibrates back and forth with extreme rapidity, it takes the form of waves which are similar to waves of light. Positive Electricity.—This term expresses the condition of the point of an electrified body having the higher energy from which it flows to a lower level. The sign which denotes this phase of electric excitement is +; all electricity is either positive or,-, negative. Negative Electricity.—This is the reverse condition to the above and is expressed by the sign or symbol-. These two terms are used in the same sense as hot and cold. Atmospheric electricity is the free electricity of the air which is almost always present in the atmosphere. Its exact cause is unknown. The phenomena of atmospheric electricity are of two kinds; there are the well-known manifestations of thunderstorms; and there are the phenomena of continual slight electrification in the air, best observed when the weather is fine; the aurora constitutes a third branch of the subject. Dynamic Electricity.—This term is used to define current electricity to distinguish it from static electricity. This is the electricity produced by the dynamo. Frictional electricity is that produced by the friction of one substance against another. Resinous Electricity.—This is a term formerly used, in place of negative electricity. The phrase originated in the well known fact that a certain (negative) kind of electricity was produced by rubbing rosin. Vitreous electricity is a term, formerly used, to describe that kind of electricity (positive) produced by rubbing glass. Magneto-electricity is electricity in the form of currents flowing along wires; it is electricity derived from the motion of magnets—hence the name. Voltaic Electricity.—This is electricity produced by the action of the voltaic cell or battery. Electricity itself is the same thing, or phase of energy, by whatever source it is produced, and the foregoing definitions are given only as a matter of convenience. The term is employed to denote that which moves or tends to move electricity from one place to another. For brevity it is written E.M.F.; it is the result of the difference of potential, and proportional to it. Just as in water pipes, a difference of level produces a pressure, and the pressure produces a flow so soon as the tap is turned on, so difference of potential produces electro-motive force, and electro-motive force sets up a current so soon as a circuit is completed for the electricity to flow through. Electro-motive force, therefore, may often be conveniently expressed as a difference of potential, and vice versa; but the reader must not forget this distinction. In ordinary acceptance among engineers and practical working electricians, electro-motive force is considered as pressure and it is measured in units called volts. The usual standard for testing and comparison is a special form voltaic cell, called the Clark cell. This is made with great care and composed of pure chemicals. The term positive expresses the condition of the point having the higher electric energy or pressure, and, negative, the lower relative condition of the other point, and the current is forced through the circuit by the (E. M. F.) electric pressure at the generator, just as a current of steam is impelled through pipes by the generating pressure at the steam-boiler. Care must be taken not to confuse electro-motive force with electric force or electric energy, when matter is moved by a magnet, we speak rightly of magnetic force; when electricity moves matter, we may speak of electric force. But, E. M. F. is quite a different thing, not “force” at all, for it acts not on matter but on electricity, and tends to move it. THE DYNAMO, OR GENERATOR.The word dynamo, meaning power, is one transferred from the Greek to the English language, hence the primary meaning of the term signifying the electric generator is, the electric power machine. The word generator is derived from a word meaning birth giving, hence also the dynamo is the machine generating or giving birth to electricity. Fig. 217.—See page 251. Again, the dynamo is a machine driven by power, generally steam or water power, and converting the mechanical energy expended in driving it, into electrical energy of the current form. To summarize, the dynamo-electric generator or the dynamo-electric machine, proper, consists of five principal parts, viz: 1. The armature or revolving portion. 2. The field magnets, which produce the magnetic field in which the armature turns. 3. The pole-pieces. 4. The commutator or collector. 5. The collecting-brushes that rest on the commutator cylinder and take off the current of electricity generated by the machine. Fig. 218 shows a dynamo of the early Edison type—the names of the principal parts are given in the note below, as well as those of the other parts of the machine. Fig. 218. This is a two-pole machine, direct current; the figure is introduced to show the “parts” only—as this dynamo has been largely superseded by others of the four pole type. Note.—A, Magnet yoke; B, Magnet and field piece; C, Pole piece; D, Zinc field piece; E, Armature; F, Commutator; I, Quadrant; JJ, Brushes; K, Adjusting handle for the brushes; L, Switch pivot; M, Pilot lamp receptacle; N, Negative lug; O, Switch lever; P, Positive lug; Q, Positive terminal; R, Negative terminal; S, Negative rod; T, Pole piece; UU, Bearings; X, Slides for belt tightener; VVV, Driving pulley; Y, Connecting blocks, one on each side of machine. An electric motor is a machine for converting electrical energy into mechanical energy; in other words it produces mechanical power when supplied with an electric current; a certain amount of energy must be expended in driving it; the intake of the machine is the term used in defining the energy expended in driving it; the amount of power it delivers to the machinery is denominated its out-put. The difference between the out-put to the intake is the real efficiency of the machine; it is well known that the total efficiency of an electric distribution system, which may include several machines, usually ranges from 75 to 80 per cent., at full load, and should not under ordinary circumstances fall off more than say 5 per cent. at one-third to half load; the efficiency of motors varies with their size, while a one horse-power motor will, perhaps, have an efficiency of 60 per cent., a 100 horse-power may easily have an efficiency of 90 per cent. and the larger sizes even more. The general and growing application of electric power to the driving of all kinds of machinery including pumps makes the question of motor driving one of the most important in the power field. For many purposes, a single speed is sufficient, but for others, it is imperative that the speed should be variable; and for still others, though not absolutely necessary, a speed adjustment is very desirable. While the direct-current motor has been in this field so long that its properties are well known and its possibilities fully developed, in the operation of motors located in the immediate neighborhood of the generator the alternating-current motor has marked advantages where a large area of territory has to be covered and the conditions are nearly uniform, that is to say— Where the current has to be transmitted a long distance and the load is approximately constant, the alternating system is preferred, as it can be operated with small main lines or conductors. This effects a saving in copper, over the direct system which requires larger conductors. Fig. 219. Fig. 220. Fig. 217, on page 247, shows a four-pole generator designed to run by a belt or directly connected to an engine. The five parts named, as the principal parts of a dynamo, are all shown in the figure. The machine is arranged ready to be bolted to the floor. Fig. 219 on the opposite page is the armature which is made up of coils of insulated wire, the free ends of which, see Fig. 220, are united to the arms of the commutator bars. When the armature is finished, as shown, the wire forms an unbroken circuit. Fig. 221. Fig. 221 is intended to represent another form of armature, but the principle upon which it operates, is the same, as the other shown. A A, represents the wire coils of the armature, B, is the shaft with its journals, C, is the commutator. All commutators both for generators and for motor armatures are insulated by mica between the bars. Fig. 222. Fig. 222 shows a woven wire brush. The brushes on the dynamo, page 247, are made of carbon. Fig. 223. Fig. 223 shows an alternating induction motor. Induction is a property by virtue of which an electric current is transferred from one conducting line to another without any metallic connection; it is that influence by which a strong current flowing through a conductor controls or affects a weaker current flowing through another conductor in its immediate neighborhood,—the strong current remaining unaffected. Fig. 224. Fig. 224 exhibits the armature for the above alternator; it Its peculiar construction enables it to run without producing any sparks; this feature renders it safe to run where there are explosive gases which might be ignited by an electric spark. In the machine the bearings are cast solid with the end shields, thus assuring perfect alignment when properly turned. Another feature is the automatic self adjusting bearings which are lubricated mechanically by rings resting upon the shaft. These rings were formerly a failure, but by the use of mineral oils are now a success. This machine is one of the simplest designs of alternating motors, the example, Fig. 223, is one developing one hundred horse-power. Fig. 225. Fig. 225 shows a revolving field with “spider.” In this construction of generators or motors the field revolves in place of the armatures, the first object of this design is to reduce the high rotative speed; it is also claimed to have a better electrical efficiency. The field spider consists of an extra heavy cast iron pulley which is keyed to the shaft; the low speed at which it runs permits the employment of bolts to secure the field coils and laminated pole pieces to the rim of the spider, as shown in the engraving. With this construction each individual pole piece can be removed and replaced independent of the others. The laminated pole piece, one of which is shown in detail in Figs. 226-229, takes its name from the fact that it is built up of a large number of layers of soft sheet iron, which it has been demonstrated give a better electrical efficiency than a solid iron. Soft iron is the most magnetic of all metals and is better suited for pole pieces than steel. It should be understood that each individual pole piece is insulated from the others as well as from the spider. The pieces of sheet iron are stamped out—like washers and are cut apart and the ends united so as to form a continuous coil, like a coil of wire and each coil is isolated; mica is used between the layers. Figs. 226-229. Fig. 230 is designed to illustrate the front of a continuous current two wire switchboard with circuit breakers; these are made up usually of marble or slate so that they will not burn; the Insurance Underwriters require a non-combustible material at this place, as well as hangers, and insulators used for conductors. The Switches shown in the middle of the board, are enlarged in Fig. 232, and are used for closing the connections with the generators and lines running to various parts of the field to be lighted or furnished with power. The switch handles are made usually of wood or hard rubber; the blades are of copper. The connections are soldered into the sockets shown upon the ends of the screws which project beyond the back of the switch-board. The upper row of figures as shown in Fig. 230 and enlarged in the engraving, 231, are circuit-breakers. The use of these is analogous to that of the safety-valve upon a steam boiler, so that when the pressure in the circuit exceeds that at which it is set the “breaker” opens the circuit and thus prevents damage. Fig. 230. In this case, the main contact is formed by means of a laminated brush while the final stroke is made on carbon, the motion of this breaker is by means of a toggle-joint which so multiplies the power applied that it does not require much of an effort to close it; this device maintains the same speed in operating the breakers when the circuit-breaker is tripped. A Rheostat is a device for controlling the amount of electricity in a conductor—by the insertion of coils of wire in a box—which may be successively switched in or out of the main circuit by means of a lever and button-switch. The best place to install a rheostat is on a wall or post, as the resistance transforms a portion of the electric energy into heat, which heat must be dispersed into the atmosphere. A transformer is an induction coil employed usually for lowering electric pressure, but it may also be used for raising the same, in which case it is sometimes called a booster. A compensator is a transformer which works automatically. Fig. 231. Fig. 232. Ammeters record the quantity of current flowing through the circuit, in amperes. Voltmeters record the pressure or strength of the current in volts. An Ampere is an electric current which would pass through a circuit whose resistance is one ohm under an electro-motive force of one volt. A Volt is an electro-motive force of sufficient strength to cause a current of one ampere to flow against a resistance of one ohm. The ampere is the unit for calculations relating to the quantity or volume of a current; the volt is the unit for calculating the pressure or strength of the current. The action of the electric current in producing rotation in an electric motor is really quite simple. While many electrical problems are comparatively complicated, the principal elements in the operation of electric motors may be readily understood. The fundamental fact in this connection is the relation between an electric current and a magnet. If a piece of round bar iron be surrounded by a coil through which an electric current passes, it becomes a magnet. In Fig. 233 the passage of a current through the coil of wire around the iron bar in either direction, renders the iron a magnet, with all its well-known properties. It will attract iron, and the space surrounding it becomes magnetic. Iron filings will arrange themselves in the direction shown by the dotted lines in the figure. One end of the magnet is the North or positive + pole and the other the South or negative - pole. If a wire, such as CD, be moved past either pole of the magnet, there will be a tendency for current to flow in the wire either from C to D or D to C, according to the character of the pole past which it is moved, and to the direction of the movement. If the ends of the wire CD are joined by a conductor, so that there is a complete circuit, a current of electricity will flow through this circuit. This circuit may be a simple wire, as shown by the line CEFD, or it may be the wire coils on machines enabling the current to produce mechanical work, or it may be electric lamps producing light. The indispensable feature is that there shall be a complete unbroken circuit from C to D for the current to flow, no matter how complicated or how long this circuit may be. This description of a dynamo and motor carries with it all of the elementary theory of electric generators and motors that is necessary for an attendant to know in order to take reasonably intelligent care of electric machines. Further useful knowledge must be acquired by studying the different types of electric motors and dynamos. All these other types of direct current machines have the same elementary theory, although their construction may be quite different. By suitable illustrations the operation of the electric motor as applied to pumps will be easily understood; its application to other machines is the same in theory and practice. “Why an electric motor revolves” is a question well worth careful, and, if necessary, long study. Fig. 233. The reason why there is a tendency for an electric current to flow in the wire CD when it is moved in the vicinity of a magnet is not fully known. There are several theories, all more or less complicated, and depending upon pure assumptions as to the nature of an electric current. For practical purposes it matters little what the reason is, the fact that current flows when there ts an electric pressure in a closed circuit, is the important thing, and it serves all useful purposes to know that current does flow, and that its direction and amount are always the same under similar circumstances. There are many facts in mechanics that are accepted and used practically, about which little is known as to their fundamental and primary causes, and this fact about motors and dynamos is, therefore, only one of many which all must accept without a full and complete explanation. The intensity of the electric pressure, or electro-motive force, depends upon the velocity of revolution of the wire sections in the armature and upon the strength of the magnets, and the quantity of current depends upon the electro-motive force and upon the amount of the resistance in the circuit. Other things being equal, the current, flowing through a long small wire, or greater resistance, will be less than through a short, thick wire, or a less resistance. Having seen that when a wire is moved in the vicinity of a magnet an electric pressure is produced which will cause a current to flow in a closed circuit, one can easily conceive of many ways in which, by combining magnets and wires so that there will be a relative motion between them, a current of electricity may be generated. In order to cause a continuous flow the relative motion must be continuous; and if the current is to be uniform the motion must be uniform. Fig. 234. Two electro-magnets are shown in Fig. 234, in which the North pole of one magnet is near the South pole of the other, and the magnetic field between the two lies in the approximately straight lines between the two magnets, as indicated by the dotted lines. If the wire CD be moved across this field and its ends be joined, as by the metallic circuit CEFD, a current will flow in this circuit. The wire CD may be made to revolve around the wire EF, passing in front of one pole and then in front of the other pole, as in Fig. 235. The current in the circuit will pass in one direction when the wire is passing one pole, and in the other direction when it is passing the other Fig. 235. A dynamo transforms mechanical into electrical energy, and a motor transforms electrical into mechanical energy. The two operations are reversible, and may be effected in the same machine; a dynamo may be used as a motor, or a motor may become a dynamo. A dynamo is a motor when it is driven by a current of electricity, and it is a dynamo when it is driven by mechanical power and produces an electric current. If a motor be driven by an engine, it can deliver a current of electricity which is able to operate other motors or electrical apparatus or lights. A simple form of electric machine is shown in Fig. 236, which is a general form of the electric motor. In this there are two projections of steel, H and G, which are made electro-magnets by the current flowing through the wires wound around Fig. 236. In order to distribute a current of electricity through these wires it is necessary to make a complete circuit. As each of the wires in the slots passes in front of a pole, a pressure or electro-motive force will be generated, and its direction will depend upon whether the pole is a North or a South pole, i.e., + or -. Note.—In the above illustrations I and J represent the ordinary electric battery; in electrical literature such marks always indicate a battery. The pressure or electro-motive force generated in the wires moving in front of the North, or positive field poles, will be in one direction, while that of those in front of the South, or negative field poles, will be in the opposite direction. Therefore, if two such wires be connected together at one end of the armature, the free terminals of the wires at the other end of the armature will have the sum of the electro-motive forces generated in the two wires. The wires so connected can be considered as a turn of a single wire instead of two separate wires, and this turn may be connected in series with other turns, so that the resulting electro-motive force is the sum of that in all the turns and all the wires so connected. It is customary to connect the coils of an armature so that the electro motive force given is that obtained from half the coils in series. The other half of the coils is connected in parallel with the first half, so that the currents flowing in the two halves will unite to give a current in the external circuit equal to twice the current in the two armature circuits or paths. It is evident that, as the armature revolves, wires which were in front of the positive pole will pass in front of the negative, and that in order to maintain the electro-motive force it will be necessary to change the connections from the armature winding to the external circuit in such a way that all the wires between the two points of connection will have their electro-motive forces in the proper direction. The connection to the armature must therefore be made not at a definite point in the armature itself, but at a definite point with reference to the field magnets, so that all the wires between two points or contacts shall always sustain the same relation to the field magnets. For this purpose a device known as a “commutator” is provided. The commutator is made up of a number of segments, as shown at A, in Fig. 237, which are connected to the armature winding. On the commutator, rest sliding contacts, or brushes, which bear on the segments and are joined to an external circuit, making a continuous path through which current may flow. As the commutator revolves, the different segments Fig. 237. On two-pole machines there are two brush-holders, each containing one or more brushes. On the four-pole machine there may be either two or four brush-holders, and on a six-pole machine, either two, four, or six brush-holders. A single path of the current through the commutator and armature winding is shown by the arrows on Fig. 237. The For the sake of simplicity, the batteries I and J, of Fig. 236, are not used on common forms of generators or motors, but the current that flows from the armature through the commutator is made to flow through the electro-magnets either in whole or in part. If all of the armature current flows around the electro-magnets or fields of the machine, it is a “series” machine; if only a part of the current is used in this way, it is a “shunt” machine; that is, some of the current is “shunted” through the fields. Sometimes both the shunt and series windings are used, and in that case the machine is called a “compound wound” machine. Such a machine has a large wire through which the main current passes, and a fine wire through which the shunted current flows. Fig. 237 shows how the commutator and the fields are connected, and how the current flows from the wires in the armature through the commutator in a series machine. If the current delivered by a dynamo does not flow in the desired direction, it can be reversed by shifting the wires in the binding posts or by throwing a switch. If the motor does not revolve in the desired direction, it can be made to do so by reversing the connections to the armature or field-coils; so that, without knowing which way a current of electricity is to be generated, any practical man can make a motor revolve in a proper direction by simply changing its connections. It is natural that a machine which gives out electric energy when driven by an external power, should, when electric energy is delivered to it, reverse its action and give out mechanical power and do work. Perhaps the simplest way to explain the cause of the movement of an electric motor, when supplied with a current, is to compare its action to the well-known attraction of unlike poles or magnets and the repulsion of like poles. Unlike poles are North and South; like poles are two North or two South. In It has been explained that if a motor be driven by a belt an electro-motive force is produced and the machine acts as a dynamo. It is also a fact that an electro-motive force is produced whether the power for driving the machine is received from a belt or from the electric current,—that is, whether the machine be driven as a dynamo or as a motor. In a dynamo, however, the current follows the direction in which the electro-motive force is acting. In a motor, the electro-motive force produced has a direction opposed to that of the flow of current. This may be illustrated by the following experiment. Two similar machines are driven independently at 600 revolutions and give an electro-motive force of 100 volts. Similar terminals of the two machines are connected together; no current flows between the machines, because the two pressures are the same and are in opposite directions. If now the belt be thrown off from one machine, its speed will begin to fall; this will lower its electro-motive force below that of the other machine or dynamo, but will not change the direction of the force. There will now be a difference of pressure in favor of the machine which is driven, and it will deliver a current through the other machine and run it as a motor. The speed of the motor will continue to fall until the difference in pressure or electro-motive force between the two machines is only sufficient to cause the flow of enough current to keep the motor running against whatever frictional resistance, and other resistance there may be. The electro-motive force generated in the motor, which is against, or counter to that of the current in the circuit, is called the “counter electro-motive force.” In order to determine how fast a motor will run without doing work under any given pressure, it is not necessary to know anything about the dynamo that furnishes the pressure. MAGNETIC NEEDLE.The figure on page 242 shows a magnetic compass needle. This is used to test the direction of an electric current flowing through a wire or cable conductor. The plus sign, +, is the positive and the minus, -, sign is the negative end or pole. A continuous current always flows from the positive to the negative end or pole, hence the north end or pole, N, is the positive end of the needle and the south pole, S, is the south pole of the needle. When one of these devices is held in close proximity to a conductor of electricity it immediately assumes a parallel position to the conductor and indicates the direction in which the current is flowing. The long, upper arrow, as shown in the figure, tells the direction of the flow. A small pocket compass may be used in place of this device and is often carried in the pocket of electricians for the purpose of indicating the direction of the current. PRESSURE IS NECESSARY TO PRODUCE AN ELECTRIC CURRENT.It should be understood that an electric dynamo or battery does not generate electricity, for if it were only the quantity of electricity that is desired, there would be no use for machines, as the earth may be regarded as a vast reservoir of electricity, of infinite quantity. But electricity in quantity without pressure is useless, as in the case of air or water, we can get no power without pressure, a flow of current. As much air or water must flow into the pump or blower at one end, as flows out at the other. So it is with the dynamo; for proof that the current is not generated in the machine, we can measure the current flowing out through one wire, and in through the other—it will be found to be precisely the same. As in mechanics a pressure is necessary to produce a current of air, so in electrical phenomena an electro-motive force is necessary to produce a current of electricity. A current in either case can not exist without a pressure to produce it. ELECTRIC PUMPING MACHINERY.Since the conditions surrounding pumping plants are so widely different, it is impossible to treat every practical application in detail, hence, the space allotted to this subject has been used in the preceding succinct and plain discussion of the principles upon which electric power is applied to the operation of pumps. The following are some of the advantages claimed for electric pumping machinery: “Economy in operation and maintenance is the first and most vital consideration that demands the attention in the installation of pumping machinery. In respect to economy, the electric system has many important advantages. It is saving in the transmission of power, and thus enables a pumping installation to be situated at a considerable distance from the source of power where the first cost and maintenance expense of other systems would be almost prohibitive. “The economy in space required is also worthy of consideration. The driving mechanism of a modern electric pumping outfit occupies a small amount of room and the space required for wiring is negligible. In case of accident, any mechanical injury to wires can be quickly and easily repaired—thus the economy in time and expenditure for repairs. There is no large loss by condensation. The only loss sustained with the electric system in the transmission of power is a small loss due A well designed electric pump will give an efficiency of from 75 to 80 per cent.; and, as the transmission loss depends upon the weight of copper in the transmission line it can be made as low as the cost of power, and, 2, the investment in copper will warrant. DIRECTIONS FOR INSTALLATION.1. It is important to locate the electric pump where it will be dry and clean and where it will be thoroughly accessible for proper care. 2. No pipes should be allowed to pass above the electric motor where liquids are likely to drip upon it. 3. The suction or supply pipe must be as short and straight as possible and must be air tight, as air entering the pump through the suction reduces its capacity or prevents it from working altogether. 4. A tight foot valve and a strainer should invariably be used on the bottom end of the suction pipe when the water is to be lifted from 8 ft. to 10 ft. below the pump. Where the lift is excessive or for any reason the supply be limited, an air chamber placed on the suction pipe near the pump will prove beneficial in preventing slamming of the valves. 5. Provision should be made for draining both pumps and pipes in cold weather by a proper application of frost cocks. 6. If the electric pump is kept dry, clean and well oiled, it will prove the most desirable and least expensive apparatus to be had for the service. 7. Ascertain the nature of electric current to be used. Direct or alternating? Voltage? (If alternating, note phase and number of alternations.) 8. Also record any unusual or peculiar circumstances connected with the installation or operation of the apparatus; and if so, what? DOMESTIC ELECTRIC PUMPS.Fig. 238. Fig. 239. In many places the pressure on the mains is insufficient to raise the water to the upper floors or through improperly designed systems of piping the pressure may be so diminished as to make the flow extremely weak or the difficulty in securing proper water supply may be due to inconvenient location with reference to water mains. The automatic electric house tank pumping plant has been designed and perfected to meet these conditions; the electric plant is connected to some power or lighting circuit and provided with an automatic attachment requiring no more care than can be given by any casual attendant. Such an installation avoids the smoke, ashes, dust and objectionable odors that accompany steam or gas plants. The accompanying diagram shows the general arrangement of the automatic electric house system used with a tank in the upper part of the building and the pump in the basement or cellar. The operation is as follows: When water is being delivered to the tank, the float rises until the upper knob makes forcible contact with the switch lever, opening the switch and stopping the pump. When water is withdrawn from the tank, the float falls until the lower knob makes contact with the switch lever, which again closes the switch and starts the pump. The supply of water is thus maintained within the tank without the aid of an attendant. The accompanying illustration, Fig. 238, shows a Worthington house tank pump of 500 gallons per hour capacity belted to a General Electric direct current motor, the pump and motor being mounted on the same base. Table of Capacity.
The above useful table is inserted to show the capacities, revolutions, size of plungers, etc., in these electrically driven pumps, the automatic feature of which is truly admirable. It must be remembered that the number of combinations between small electric motors and proportionate pumps for water, gas, air, etc., afford an endless field for the exercise of engineering skill. ELECTRIC MOTOR AND AIR PUMP.Fig. 240 is intended to show the application of the electric motor to a triplex pump of small size, the plungers being 31/8 inches in diameter. The Stroke is 47/8 inches which gives a capacity of 108 cubic inches per revolution, with a pressure of 50 lbs. to the square inch. The pumps require about one-half horse power applied at the motor. Fig. 240. The high speed of the motor is reduced by two belt pulleys and two chain wheels. These pumps may be worked independently to produce pressure or vacuum as desired by a separate pipe for each pump. MOTOR AND CENTRIFUGAL PUMP.Fig. 241 is intended to show the application of the electric motor to a centrifugal pump; these two machines are mounted on one bed plate, directly connected by a flange coupling between them. The motor shown, is almost identical with the machine illustrated, Fig. 217, and described on page 251. The pump is so arranged that the discharge can be turned in any direction desired. Wherever electric power is available and the centrifugal pump is the form best adapted to the work, this combination presents advantages over a steam engine operated by a plain slide valve such as is generally used. Fig. 241. DIRECT DRIVEN MOTOR PUMP.Fig. 242 shows a double pump driven directly, without gears or belt, from the shaft of an electric motor. The pump crossheads are connected directly to cranks at each end of the motor shaft. The cranks are set at right angles and each pump is double acting, or has two plungers connected by outside rods and with outside packed stuffing-boxes, so that this portion of the pump is always accessible. The plungers are 31/2 inches diameter and 51/2 inches stroke. The pump and motor are mounted upon a rigid box girder frame: this unit is self-contained and occupies a relatively small floor space. Electric Drive for Fire Pumps. The importance of instantly operating fire extinguishing apparatus can scarcely be exaggerated. The largest conflagrations are but little flames at the beginning, and if caught at the critical moment they make no record of destruction; for such service the electric current is the ideal agent. A notable installation of electric-driven pumps for fire service is in the Marshall Field store, Chicago, a building occupying an entire city block. The outfit consists of a Laidlaw-Dunn-Gordon duplex Underwriter pump connected by single reduction gearing to a waterproof electric motor. Fig. 242. The pump cylinders, 8 × 12 inches, have a computed capacity of 700 gallons per minute at 140 pounds water pressure. The pump, besides its other special features, is claimed to be rust proof throughout so that it will not get out of ready running condition. Fig. 243. ELECTRIC-MINING PUMPS.The electric system has especial conveniences for mine pumping because of its adaptability to long transmissions of power; electric power can be transmitted to almost any distance, and the pumps can be supplied with either direct or alternating current motors. A mining outfit can be easily divided into a number of parts, to facilitate lowering into a mine, after which the assembling of the parts is a simple operation. Stationary pumps for mine use are made in two classes: first, vertical pumps having cylinders in a vertical position in which the over all height is comparatively great and the horizontal dimensions as small as possible; second, horizontal pumps with cylinders in a horizontal position and having for cross dimensions the over all length. The class of pump to be selected, of course, depends upon the limitations of the location. In either case, the motor used for driving the pump is mounted on an extension of the pump base, making a self-contained and compact outfit. Engraving, Fig. 243, represents a Quintuplex pump used principally in mining operations, or wherever large quantities of water are to be delivered under high pressure in the shortest possible space of time. The pump here shown was designed to deliver 225 gallons of water per minute under a head of 1,200 feet. It has five plungers 4 inches in diameter each and having a uniform stroke of 12 inches. These pumps driven by electric motors it is said represent the most economical method of transmitting power, as compared with the best designs of steam pumps. An efficiency of 80 per cent. is claimed for these pumps. Note.—It is interesting to know that in one of the largest electric pumping installations which has ever been made for mining work, the power is carried 2,500 feet underground at a potential of 3,500 volts and then transformed into 220 volts at the motors. No trouble has thus far resulted from the high voltage or any other cause; in regard to danger from underground electric pumps, it can be stated that accidents due to the use of electricity in such installations are almost unknown. Induction motors are arranged to operate without moving contacts. They are therefore free from sparks and can be used in mines where the presence of gases compels the use of safety lamps. Fig. 244 exhibits an electric induction motor operating a 51/2 × 8 portable track pump. Portability is an important feature in all pumps for mine use; and, as track pumps may be put into service immediately at any point on a system of tracks, they meet this requirement better than pumps of any other form. Such an outfit can be hauled to any point in the mine and there operated from some convenient circuit such, for instance, as the circuit supplying power to mine locomotives. Fig. 244. The pump and motor shown in Fig. 244 are mounted on an iron truck, no wood whatever being used in construction, so that adjustment cannot be affected by moisture and an easy running and durable pump is assured. The pumps are made as compact and strong as possible for mine service, which is usually exceptionally rough and continuous. They are of the horizontal type which is best adapted for low passageways and are designed so as to afford easy access to all parts. The pumps are single acting and the plungers are provided with outside stuffing-boxes, which can be packed, and being in sight, any leakage can be quickly detected. Access to all valves is made easy by the removal of one large hand-hole cover on the valve chest. THE STEAM Fig. 245. |
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