Project Gutenberg's Pumps and Hydraulics - Part Two, by William Rogers

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Title: Pumps and Hydraulics - Part Two

Author: William Rogers

Release Date: August 4, 2018 [EBook #57639]

Language: English

Character set encoding: UTF-8

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TEN THOUSAND HORSE POWER.
(See Part One, Page 133.)

—BY—

WILLIAM ROGERS

Author of “Drawing and Design,” etc.

RELATING TO

HAND PUMPS; POWER PUMPS; PARTS OF PUMPS; ELECTRICALLY DRIVEN PUMPS; STEAM PUMPS, SINGLE, DUPLEX AND COMPOUND; PUMPING ENGINES, HIGH DUTY AND TRIPLE EXPANSION; THE STEAM FIRE ENGINE; UNDERWRITERS’ PUMPS; MINING PUMPS; AIR AND VACUUM PUMPS; COMPRESSORS; CENTRIFUGAL AND ROTARY PUMPS; THE PULSOMETER; JET PUMPS AND THE INJECTOR; UTILITIES AND ACCESSORIES; VALVE SETTING; MANAGEMENT; CALCULATIONS, RULES AND TABLES.

WITH ILLUSTRATIONS.

ALSO

GENERAL CONSIDERATIONS; GLOSSARY OF PUMP TERMS; HISTORICAL INTRODUCTION, WITH ILLUSTRATIONS; THE ELEMENTS OF HYDRO-MECHANICS, HYDROSTATICS AND PNEUMATICS; GRAVITY AND FRICTION; HYDRAULIC MEMORANDA; LAWS GOVERNING FLUIDS; WATER PRESSURE MACHINES; PUMPS AS HYDRAULIC MACHINES, ETC.

PART TWO.

PUBLISHED BY

THEO. AUDEL & COMPANY

72 FIFTH AVE.,
NEW YORK, U.S.A.

7, IMPERIAL ARCADE,
LUDGATE CIRCUS, E.C.,
LONDON, ENG.

The owner of a great tannery had once an improvement in making leather proposed to him by a foreman, but the merchant could not comprehend it even with the most earnest verbal explanation. As a last resort he said, “put it in writing so that I can study it out.” This was done and the change after an examination of the paper was made as advised. So in these volumes much important information is written and printed that it may be “studied out.”

The author believes the following features of his work adapt it to the purpose for which it was designed:

1. It contains no more than can be mastered by the average engineer and those associated with him, such as millwrights, machinists, superintendents of motor power, electric stations, water works, etc.

2. It is thoroughly systematized. The order and development of subjects is thought to be logical, and the arrangement of topics especially adapted to the needs of those who aspire to do the best service in their every day responsibilities.

3. The work is written in accordance with modern theories and practice; no exertion has been spared in the attempt to make it fairly represent the latest state of the science of hydraulics and its adaptation to the needs of modern mechanical advancement, i.e., in the line of practical hydraulics.

4. It has been made by “men who know for men who care,” for the whole circle of the sciences consists of principles deduced from the discoveries of different individuals, in different ages, thrown into common stock; this is especially so of the science of hydraulics; thus it may be truthfully owned that the work contains the gathered wisdom of the ages, utilized wherever the author has found that it would increase the usefulness of the volumes.

5. It is a work of reference minutely indexed. We are warned by Prof. Karl Pearson that “education can only develope; it cannot create. If a man has not inherited ability to learn, education cannot make him learn,” but in a well indexed book, simply and plainly written, both classes referred to are equally benefited.

There came the moment, once upon a time, when the author of this book, in his eager pursuit of knowledge, asked one question too much, to which he received the “gruff” answer:

“Look ahere, I don’t propose to make a dictionary of myself.”

This was a painful retort from a man already under large obligations to the questioner, but it had its reason in being spoken. There are things in the way of a man’s own craft that he most unwillingly imparts to anyone else.

It is not thus with this work; nothing has been withheld that would make it plain and helpful to one in need of the special line of information aimed to be conveyed in its make-up.

In making acknowledgment for favors received the author first remembers Mr. Alberto H. Caffee who arranged in behalf of the L. Middleditch Press for the issue of the work. Mr. Caffee’s name appears in the dedication, with that of the brave soldier and accomplished gentleman Maj. Abram B. Garner.

Mr. Harry Harrison’s skill is shown in the “lay out” or typographical arrangement of the work and Mr. Henry J. Harms has contributed his careful supervision to each page of the book as it has gone through the press.

Lewis F. Lyne, Mechanical Engineer, has, amid his other responsible and active duties “passed upon” each page of the entire two volumes.

Credit is due also to Mr. Edward F. Stevens, assistant at the Yale University library, New Haven, Conn., for a careful reading of the two volumes for clerical errors, punctuation, etc. Mr. Stevens is a graduate of Colby University and a ripe scholar; moreover after leaving college he has had some twelve or more years experience in business and editing with a mechanical book publishing house widely known throughout England and the U. S.—a rare combination of useful experience.

The final revision of the two volumes has been made by one of the brightest young engineers in New York City, now consulting engineer and attorney at Patent Law with offices in the Flat Iron Building, corner of Twenty-third St. and Fifth Avenue—Mr. Edward Van Winkle.

These names should assure confidence in the contents of the work, which has been some years in preparation, and with nothing spared to make it trustworthy.

Pneumatics treats of the mechanical properties and effects of air and similar fluids; these are called elastic fluids and gases, or aëriform fluids.

Hydro-pneumatics. This is a compound word formed from two Greek words signifying water and air; in its primary meaning it conveys the idea of the combined action of water and air or gas.

Fig. 330.

Air is the respirable fluid which surrounds the earth and forms its atmosphere. It is inodorous, invisible, insipid, colorless, elastic, possessed of gravity, easily moved, rarefied and condensed, essential to respiration and combustion, and is the medium of sound. It is composed by volume of 20.7 parts of oxygen and 79.3 of nitrogen, by weight, of 23 of oxygen and 77 of nitrogen. These gases are not chemically united, but are mixed mechanically. Air contains also ¹⁄₂₀₀₀ of carbon dioxide, some aqueous vapor, about one per cent. of argon, and small varying amounts of ammonia, nitric acid, ozone, and organic matter. The specific gravity of the air at 32° F is to that of water as 1 to 773, and 100 cubic inches of air at mean temperature and pressure weighs 30¹⁄₂ grains.

Aëriform fluids are those which have the form of air. Many of them are invisible, or nearly so, and all of them perform very important operations in the material world. But, notwithstanding that they are in most instances imperceptible to our sight, they are really material, and possess all the essential properties of matter. They possess, also, in an eminent degree,16 all the properties which have been ascribed to liquids in general, besides others by which they are distinguished from liquids.

Elastic fluids are divided into two classes, namely, 1, permanent gases and, 2, vapors. The gases cannot be easily converted into the liquid state by any known process of art;* but the vapors are readily reduced to the liquid form either by pressure or diminution of temperature. There is, however, no essential difference between the mechanical properties of both classes of fluids.

As the air which we breathe, and which surrounds us, is the most familiar of all this class of bodies, it is generally selected as the subject of Pneumatics. But it must be premised that the same laws, properties and effects, which belong to air, belong in common, also, to all aëriform fluids or gaseous bodies.

There are two principal properties of air, namely, gravity and elasticity. These are called the principal properties of this class of bodies, because they are the means by which their presence and mechanical agency are especially exhibited.

Although the aëriform fluids all have weight, they appear to possess no cohesive attraction.

The pressure of the atmosphere caused by its weight is exerted on all substances, internally and externally, and it is a necessary consequence of its fluidity. When the external pressure is artificially removed from any part, it is immediately felt by the reaction of the internal air.

Heat insinuates itself between the particles of bodies and forces them asunder, in opposition to the attraction of cohesion and of gravity. It therefore exerts its power against both the attraction of gravitation and the attraction of cohesion. But, as the attraction of cohesion does not exist in aëriform fluids, the expansive power of heat upon them has nothing to contend with but gravity. Hence, any increase of temperature, expands an elastic fluid prodigiously, and a diminution of heat condenses it.

17

A column of air, having a base an inch square, and reaching to the top of the atmosphere, weighs about fifteen pounds. This pressure, like the pressure of liquids, is exerted equally in all directions.

The elasticity of air and other aëriform fluids is that property by which they are increased or diminished in extension, according as they are compressed. This property exists in a much greater degree in air and other similar fluids than in any other substance. In fact, it has no known limit, for, when the pressure is removed from any portion of air, it immediately expands to such a degree that the smallest quantity will diffuse itself over an indefinitely large space. And, on the contrary, when the pressure is increased, it will be compressed into indefinitely small dimensions.

The elasticity or pressure of air and all gases is in direct proportion to their density; or, what is the same thing, inversely proportional to the space which the fluid occupies. This law, which was discovered by Mariotte, is called “Mariotte’s Law.” This law may perhaps be better expressed in the following language; namely, the density of an elastic fluid is in direct proportion to the pressure which it sustains.

Air becomes a mechanical agent by means of its weight, its elasticity, its inertia and its fluidity.

The fluidity of air invests it, as it invests all other liquids, with the power of transmitting pressure; fluidity is a necessary consequence of the independent gravitation of the particles of a fluid. It may, therefore, be included among the effects of weight.

The inertia of air is exhibited in the resistance which it opposes to motion, which has already been noticed under the head of Mechanics. This is clearly seen in its effects upon falling bodies, as will be exemplified in the experiments with the air-pump.

The great degree of elasticity possessed by all aëriform fluids, renders them susceptible of compression and expansion to an almost unlimited extent. The repulsion of their particles18 causes them to expand, while within certain limits they are easily compressed. This materially affects the state of density and rarety under which they are at times exhibited.

It may here be stated that all the laws and properties of liquids (described under the heads of Hydrostatics and Hydraulics) belong also to aëriform fluids.

The chemical properties of both liquids and fluids belong peculiarly to the science of Chemistry, and are, therefore, not to any extent, considered in this volume.

The air which we breathe is an elastic fluid, surrounding the earth, and extending to an indefinite distance above its surface, and constantly decreasing upwards in density. It has already been stated that the air near the surface of the earth bears the weight of that which is above it.

Being compressed, therefore, by the weight of that above it, it must exist in a condensed form near the surface of the earth, while in the upper regions of the atmosphere, where there is no pressure, it is highly rarefied. This condensation, or pressure, is very similar to that of water at great depths in the sea.

Besides the two principal properties, gravity and elasticity, the operations of which produce most of the phenomena of Pneumatics, it will be recollected that as air, although an invisible is yet a material substance, possessing all the common properties of matter, it possesses also the common property of impenetrability.

The Thermometer is an instrument to indicate the temperature of the atmosphere. It is constructed on the principle that heat expands and cold contracts most substances. The thermometer consists of a capillary tube, closed at the top and terminating downwards in a bulb. It is filled with mercury which expands and fills the whole length of the tube or contracts altogether into the bulb, according to the degree of heat or cold to which it is exposed. Any other fluid which is expanded19 by heat and contracted by cold, may be used instead of mercury.

As it has been proved by experiment that 100 cubic inches of air weighs 30¹⁄₂ grains, it will readily be conceived that the whole atmosphere exercises a considerable pressure on the surface of the earth. The existence of this pressure is shown by the following experiments. On one end of a stout glass cylinder, about 10 inches high, and open at both ends, a piece of bladder is tied quite air-tight. The other end, the edge of which is ground and well-greased, is pressed on the plate of the air-pump, Fig. 331. As soon as the air in the vessel is rarefied by working the air-pump, the bladder is depressed by the weight of the atmosphere above it, and finally bursts with a loud report caused by the sudden entrance of air.

Fig. 331.

Fig. 332.

Fig. 333.

The preceding experiment only serves to illustrate the downward pressure of the atmosphere. By means of the Magdeburg hemispheres, Figs. 332 and 333, the invention of which is due to Otto von Guericke, burgomaster of Magdeburg, it can be shown that the pressure acts in all directions. This apparatus consists of two hollow brass hemispheres of 420 to 4¹⁄₂ inches diameter, the edges of which are made to fit tightly, and are well greased. One of the hemispheres is provided with a stop-cock, by which it can be screwed on to the air-pump, and on the other there is a handle. As long as the hemispheres contain air they can be separated without any difficulty, for the external pressure of the atmosphere is counterbalanced by the elastic force of the air in the interior. But when the air in the interior is pumped out by means of an air-pump, the hemispheres cannot be separated without a powerful effort.

The Barometer is an instrument to measure the weight of the atmosphere, and thereby to indicate the variations of the weather, etc. It consists of a long glass tube, about thirty-three inches in length, closed at the upper end, and filled with mercury. The tube is then inverted in a cup or leather bag of mercury, on which the pressure of the atmosphere is exerted. The following experiment, which was first made in 1643, by Torricelli, a pupil of Galileo, gives an exact measure of the weight of the atmosphere.

Fig. 334.

A glass tube is taken, about a yard long and a quarter of an inch internal diameter, Fig. 334. It is sealed at one end, and is quite filled with mercury. The aperture, C, being closed by the thumb, the tube is inverted, the open end placed in a small mercury trough, and the thumb removed. The tube being in a vertical position, the column of mercury sinks, and, after oscillating some time, it finally comes to rest at a height, A, which at the level of the sea is about 30 inches above the mercury in the trough.

21

The mercury is raised in the tube by pressure of the atmosphere on the mercury in the trough. There is no contrary pressure on the mercury in the tube, because it is closed; but, if the end of the tube be opened, the atmosphere will press equally inside and outside the tube, and the mercury will sink to the level of that in the trough. It has been shown that the heights of two columns of liquid in communication with each other are inversely as their densities; and hence it follows that the pressure of the atmosphere is equal to that of a column of mercury the height of which is 30 inches. If, however, the weight of the atmosphere diminishes, the height of the column which it can sustain must also diminish.

Why a vacuum gauge is graduated in inches instead of in pounds is thus explained. Take a tube say 35 inches long, closed at one end, filled with mercury and inverted with its open end in a bowl containing the same liquid.

The atmosphere will exert on the surface of the mercury in the bowl a pressure of about 15 pounds per square inch and this pressure will be transmitted to that in the tube so that the upward pressure inside the tube at the level of the mercury in the bowl will be 15 pounds per square inch.

Below the surface the pressure increases, due to the depth of mercury, but the weight of mercury inside the tube below the level in the bowl counteracts the weight of that outside so that the upward pressure per square inch at the surface line is 15 pounds per square inch inside the tube no matter how much or little it is submerged. In the upper end of the tube the mercury has dropped away, leaving a complete vacuum.

22

The 15 pounds will force the mercury up into the tube until the column is high enough to balance that pressure. One cubic inch of mercury weighs about half a pound. It would take two cubic inches to weigh a pound and a column two inches high to exert a pressure of one pound per square inch of base, or a column 30 inches high to balance the pressure of 15 pounds.

Fig. 335.

Fig. 336.

If instead of a perfect vacuum there was a pressure of two pounds in the upper end of the tube the column would have to balance a pressure of 15-2 = 13 pounds and would be 26 inches high. As the absolute pressure in the top of the tube gets greater, that is to say, as the difference between that pressure and that of the atmosphere or the so-called vacuum gets less, the column of mercury gets lower, and its height is a measure of the completeness of the vacuum.

23

Hero’s fountain, which derives its name from its inventor, Hero, who lived at Alexandria, 120 B.C., depends on the elasticity of the air. It consists of a brass dish, D, Fig. 335, and of two glass globes, M and N. The dish communicates with the lower part of the globe, N, by a long tube, B; and another tube, A, connects the two globes. A third tube passes through the dish, D, to the lower part of the globe, M. This tube having been taken out, the globe, M, is partially filled with water; the tube is then replaced and water is poured into the dish. The water flows through the tube, B, into the lower globe, and expels the air, which is forced into the upper globe; the air, thus compressed, acts upon water, and makes it jet out as represented in the figure. If it were not for the resistance of the atmosphere and friction, the liquid would rise to a height above the water in the dish equal to the difference of the level in the two globes.

The fountain in vacuo, Fig. 336, shows an interesting experiment made with the air-pump, and shows the elastic force of the air. It consists of a glass vessel, A, provided at the bottom with a stop-cock, and a tubulure which projects into the interior. Having screwed this apparatus on the air-pump, it is exhausted, and the stop-cock being closed, it is placed in a vessel of water, R. By opening the stop-cock, the atmospheric pressure upon the water in the vessel makes it jet through the tubulure into the interior of the vessel, as shown in the drawing.

Gases are bodies which, unlike solids, have no independent shape, and, unlike liquids, have no independent volume. Their molecules possess almost perfect mobility; they are conceived as darting about in all directions, and are continually tending to occupy a greater space. This property of gases is known by the names expansibility, tension, or elastic force, from which they are often called elastic fluids.

Gases and liquids have several properties in common, and some in which they seem to differ are in reality only different degrees of the same property. Thus, in both, the particles are capable of moving; in gases with almost perfect freedom; in liquids not quite so freely, owing to a greater degree of viscosity. Both are compressible, though in very different degrees.

If a liquid and a gas both exist under the pressure of one atmosphere, and then the pressure be doubled, the water is compressed by about the ¹⁄₂₀₀₀₀ part while the gas is compressed by one-half. In density there is a great difference; water, which is the type of liquids, is 770 times as heavy as air, the type of gaseous bodies, while under the pressure of one atmosphere. A spiral spring only shows elasticity when it is compressed; it loses its tension when it has returned to its primitive condition. A gas has no original volume; it is always elastic, or in other words, it is always striving to attain a greater volume; this tendency to indefinite expansion is the chief property by which gases are distinguished from liquids.

Fig. 337.

Matter assumes the solid, liquid, or gaseous form according to the relative strength of the cohesive and repulsive forces25 exerted between their molecules. In liquids these forces balance; in gases repulsion preponderates.

By the aid of pressure and of low temperatures, the force of cohesion may be so far increased in many gases that they are readily converted into liquids, and we know now that with sufficient pressure and cold they may all be liquified. On the other hand, heat, which increases the vis viva of the molecules, converts liquids, such as water, alcohol and ether or gas into the aëriform state in which they obey all the laws of gases. The aëriform state of liquids is known by the name of vapor, while gases are bodies which, under ordinary temperature and pressure, remain in the aëriform state.

In describing exclusively the properties of gases, we shall, for obvious reasons, refer to atmospheric air as their type.

Expansibility of Gases. This property of gases, their tendency to assume continually a greater volume, is exhibited by means of the following experiment:—A bladder, closed by a stop-cock and about half full of air, is placed under the receiver of the air pump, Fig. 337, and a vacuum is produced, on which the bladder immediately distends.

Fig. 338.

This arises from the fact that the molecules of air flying about in all directions press against the sides of the bladder. Under ordinary conditions, this internal pressure is counterbalanced by the air in the receiver, which exerts an equal and contrary pressure. But when this pressure is removed, by exhausting the receiver, the internal pressure becomes evident. When air is admitted into the receiver, the bladder resumes its original form.

26

The compressibility of gases is readily shown by the pneumatic syringe, Fig. 338. This consists of a stout glass tube closed at one end, and provided with a tight-fitting packed piston. When the rod of the piston is pressed down in the cube, the air becomes compressed into a smaller volume; but as soon as the force is removed the air regains its original volume, and the piston rises to its former position.

Weight of Gases. From their extreme fluidity and expansibility, gases seem to be uninfluenced by the force of gravity: they nevertheless possess weight like solids and liquids. To show this, a glass globe of 3 or 4 quarts’ capacity is taken, Fig. 339, the neck of which is provided with a stop-cock, which hermetically closes it, and by which it can be screwed on the plate of the air-pump.

The globe is then exhausted, and its weight determined by means of a delicate balance. Air is now allowed to enter, and the globe again weighed. The weight in the second case will be found to be greater than before, and if the capacity of the vessel is known the increase will obviously be the weight of that volume of air.

When the atoms or particles which constitute a body are so balanced by a system of attractions and repulsions that they resist any force which tends to change the figure of the body, they will possess a property, known by the name of elasticity. Elasticity, therefore, is the property which causes a body to resume its shape after it has been compressed or expanded.

Fig. 339.

Pressure exerted by Gases. Gases exert on their own molecules, and on the sides of vessels which contain them, pressures which may be regarded from two points of view. First, we may neglect the weight of the gas; secondly, we may take account of its weight. If we neglect the weight of any gaseous mass at rest, and only consider its expansive force, it will be seen that the pressures due to this force act with the same27 strength on all points, both of the mass itself and of the vessel in which it is contained.

It is a necessary consequence of the elasticity and fluidity of gases that the repulsive force between the molecules is the same at all points, and acts equally in all directions.

If we consider the weight of any gas, we shall see that it gives rise to pressures which obey the same laws as those produced by the weight of liquids. Let us imagine a cylinder, with its axis vertical, several miles high, closed at both ends and full of air. Let us consider any small portion of the air enclosed between two horizontal planes. This portion must sustain the weight of all the air above it, and transmit that weight to the air beneath it, and likewise to the curved surface of the cylinder which contains it, and at each point in a direction at right angles to the surface. Thus the pressure increases from the top of the column to the base; at any given layer it acts equally on equal surfaces, and at right angles to them, whether they are horizontal, vertical, or inclined.

The pressure acts on the sides of the vessel, and it is equal to the weight of a column of gas whose base is this surface, and whose height its distance from the summit of the column. The pressure is also independent of the shape and dimensions of the supposed cylinder, provided the height remain the same.

For a small quantity of gas the pressures due to its weight are quite insignificant, and may be neglected; but for large quantities, like the atmosphere, the pressures are considerable, and must be allowed for.

Diffusion of gases.—Liquids mixed together, gradually separate, and lie superimposed in the order of their densities, and the surfaces of the separation of the liquids are horizontal. But when gases are mixed, they present other conditions of equilibrium, as follows.

1.—A homogeneous and persistent mixture is formed rapidly, so that all parts of the same volume are composed of the same proportions of the mixed gases.

28

2.—In a mixture of gases, the pressure (or elastic force), exercised by each of the gases, is the same as it was when alone.

3.—The rapidity with which the diffusion takes place, varies with the specific gravity of the gases. The more widely two gases differ in density, the quicker the process of intermixture.

Evaporation.—This is the slow formation of vapor from the surface of a liquid. The elastic force of a vapor which saturates a space containing a gas (like air), is the same as in a vacuum. The principal causes which influence the amount and rapidity of evaporation are as follows.

1st.—Extent of a surface. As the evaporation takes place from the surface, an increase of surface evidently facilitates evaporation.

2d.—Temperature. Increasing the elastic force of vapor, has a most important influence on the rapidity of evaporation; therefore the temperature of ebullition marks the maximum point of evaporation.

3d.—The quantity of the same liquid already in the atmosphere exercises an important influence on evaporation. The atmosphere can absorb only a certain amount of vapor, and evaporation ceases entirely when the air is saturated, but it is greatest when free from vapor, that is perfectly dry.

4th.—Renewal of the air. If currents of air are continually removing the saturated atmosphere from above the surface of a liquid, evaporation takes place most rapidly, since new portions of air, capable of absorbing moisture, are presented to it. Evaporation is therefore more rapid in a breeze than in still air.

5th.—Pressure on the surface of the liquid influences evaporation, because of the resistance thus offered to the escape of the vapor. That is to say—water boils more freely in an open vessel than within a steam boiler under pressure. Hence, the necessity for having large steam disengaging surfaces to prevent priming or lifting of the water when the boiler is forced beyond its rated capacity.

The use of compressed air has become very general through the use of small hand pumps; the cylinder of these must be smooth, and the plunger is usually packed with a cup leather packing.

Fig. 340.—Gas Fitter’s Proving Pump.

Fig. 340 shows a gas fitter’s air proving pump. The gauge is attached to any opening into the system of pipes to be tested, with a rubber hose leading to the pump. By working the pump the air is forced into the pipes; upon stopping the pump if the hand upon the gauge remains stationary there are no leaks in the system. If there are leaks the hand of the gauge will gradually return to the zero mark.

Fig. 341 shows a Portable Tire Air Pump, which can be used by hand or affixed to a wall or bench; it is of the lever type, with 2 × 8 cylinders, fitted with check valve and extra heavy rubber tubing. As the leverage on the piston-rod increases the resistance on the piston also increases, thereby securing the30 powerful leverage of the well-known “toggle-joint” principle as the piston finishes its stroke; thus the best possible results are obtained.

Fig. 342 illustrates a Hand Lever Air Pump with cylinder 3¹⁄₄″ × 6¹⁄₄″; its capacity—one stroke—is 36 cubic inches. The greatest pressure it is intended to operate against is 150 lbs. to the square inch. In operation this design has the advantage of the leverage of the toggle-joint indicated above.

Fig. 343 exhibits a Hand Air Pump which has the same dimensions as that just described, screwed to the floor. Its particular advantage is the fact that the motion of the lever is natural and easy being horizontal and still retaining the advantages of the toggle-joint.

Fig. 341.—Hand Pump.

Fig. 342.

Fig. 343.

An air pump is an apparatus for, 1, the exhaustion; 2, compression or transmission of air.

A vacuum pump is an apparatus consisting of, 1, a chamber or barrel; 2, a suction pipe with a valve to prevent return flow; 3, a discharge pipe which has a valve which is closed when the chamber is emptied and, 4, a steam induction pipe provided with a valve that is opened when the chamber is filled with water and closed when the chamber is filled with steam.

It is not right to call an air pump a vacuum pump, as the latter does not move air alone; it removes water, vapor and air from the condenser to form a vacuum. An air pump is designed to pump air alone.

A vacuum is a space entirely devoid of matter. That is, it is a space that contains nothing—no oxygen, no hydrogen, no air, no water, no pressure. It is for this reason that a perfect vacuum in practice is very difficult to obtain, especially as applied in a steam engine, as a liquid when in the presence of a vacuum generally gives off some vapor, owing to the fact that the surface is more or less in tension, besides its usual evaporative quality. Among all the liquids it has been found that mercury, on account of its very high specific gravity, can be best used to produce a vacuum and maintain it, and it is for this reason that the words “vacuum” and “inches of mercury” are synonymous.

32

The particular feature that makes steam valuable in producing a vacuum is the fact that when it is condensed, it decreases 1600 times in volume and except for this small quantity of water and some vapor which even cool water gives off in a vacuum, a perfect vacuum would be established and it is only necessary to draw off the condensed steam and vapor by proper apparatus to enable the vacuum to be maintained which the condensation has created. The apparatus for doing this is called the air pump and the reservoir in which this condensation takes place is called the condenser.

The condensation of steam in the condenser is effected in two ways. The exhaust steam either meets in direct contact the water which is to condense it, or, the steam impinges upon cool metallic surfaces the temperature of which is kept down by circulating cool water through them. In the first case the condensed steam and the condensing water meet and mingle. The condenser is an iron pot or shell into which the steam is exhausted and the cooling water enters it in the form of a sheet or spray. Such condensers are called jet condensers for this reason, and the cooling water is called the injection. All water that is used for condensing steam is therefore called the injection water.

When the exhaust steam strikes cool surfaces and is condensed by those surfaces, such condenser is called a surface condenser. The cooling surface is usually a series of pipes or tubes made of brass or copper to secure a rapid transfer of heat. These tubes are usually tinned inside and outside to prevent corrosion and in marine practice are made ⁵⁄₈″ in diameter. In most cases, condensation is effected by bringing the exhaust steam in contact with the outside of the tubes, the circulating water being inside.

In the surface condenser, as the circulation does not mingle with the condensed steam, the air pump has nothing to do with this water but is only required to pump out the condensed steam and air which enter the condenser; the pump which takes care of the circulation is called the circulating pump.33 When large quantities of water are used and the difference in level through which the water must be raised is slight as on board ship, centrifugal pumps are generally used.

In the jet type of condenser where the water acts directly on the steam, the injection water will cause a lower temperature with less water and less apparatus than a surface condenser. The amount of injection water varies from 20 to 30 times the weight of steam to be condensed in cool seasons and from 30 to 35 times the amount in summer season. With fresh water this can be pumped into the boiler when the oil is extracted from it. It is for this reason that surface condensers are universally used for sea-going vessels to avoid salt water. They are also much used on land in places where the feed water contains mineral salts and is injurious to the boiler.

In places where the cost of hydrant water is excessive, it is of importance to use the same injection water over and over again, but this cannot be done until the water is first cooled. There are numerous methods by means of which this is done. All of these methods utilize the principle of scattering the injection water in the way best calculated to bring the greatest surface in contact with the largest quantity of air so that evaporation may take place quickly and effectively.

This is sometimes done by pumping the water through a number of spray nozzles up into the air, allowing it to fall into a lake or cold well below, or, as is more usually the case, the injection water is allowed to descend in a tower in a fine state of division over tiles or wire gauze or corrugated surfaces. A current of air, either forced by a fan or drawn up through it, causes a vaporization of the film of warm water pouring over the different surfaces, and the air cooling and the evaporation combined withdraw the heat from the water so that when it reaches the bottom it is in condition to be used again.

34

Fig. 344.

Fig. 345.

Cooling towers are used with either jet or surface condensers and can be used either with or without a fan, depending upon the design. In general these towers usually lower the temperature of the water from 120 degrees to 80 degrees, which35 is sufficient to maintain a vacuum of about 26 inches. As they depend chiefly upon the results of evaporation to do the cooling, they work better on a dry day than when the air is humid.

The figures on the opposite page are designed to illustrate the use of an air pump in connection with a jet condenser; this combination is properly called a vacuum pump because it not only pumps air, but water and vapor as well. The steam end of this apparatus is described in Part One, page 324, of this work.

The air and vacuum end has a cylinder lined with composition-brass bored smooth; the piston has square rubber and canvas packing. The discharge—as shown in cut—is located sufficiently high, so that the cylinder retains a large portion of water. This forms a seal and causes the pump to work more advantageously than it would with air alone. A small pipe leads from the discharge chamber to the piston-rod stuffing-box. This contains a double packing and the water which flows through this small pipe forms a continuous seal around the piston-rod and thus prevents air from entering.

The injection water enters the elbow at the top and is drawn through an annular opening into the condenser. This opening may be regulated by the small hand wheel shown at the top end of the stem.

The exhaust from the steam end flows into the condenser through the pipe as may readily be observed—or escapes into the atmosphere by throwing the switch valve.

36

A ball-float attached to an air valve is located at the right hand of the condenser so that in case the pump should fail to operate from any cause, the injection water will lift the ball-float, which in turn will open the air valve and by discharging the vacuum will prevent the flooding of the engine cylinder with water.

It is a well-known fact that the atmosphere exerts what is usually termed “back pressure” of 14.7 pounds per square inch upon the piston area of a steam engine, also that water converted into steam, may be converted into its original state by condensation. Now, if this back pressure, which is, in reality, the weight of the surrounding atmosphere, be removed from the piston of a steam engine, the steam on the opposite side of the piston would have that much (14.7 lbs.) less work to do.

Applying this to steam engines means conveying the exhaust, or expanded steam, which would otherwise be allowed to escape into the open air, into a closed chamber, where it is met by a spray of cold water, which so rapidly absorbs the heat contained in the steam that it ceases to retain its gaseous form, and is again reduced to its original bulk as water. A great change has now taken place, and the steam is reduced to its liquid form. As this water of condensation only occupies about ¹⁄₁₆₀₀ of the space filled by the steam from which it was formed, the remainder of the space is vacant, and no pressure exists.

The difference in volume accounts for the atmospheric pressure on the outside of the chamber, and as the vacuum extends throughout the whole distance which the exhaust steam originally occupied, it, of course, is made available in the cylinder of the engine in the shape of a decreased pressure on the exhaust side of the piston; the atmospheric pressure remains constant, therefore we have the atmospheric pressure acting on one side of the piston, and absent on the other; the gain being 14.7 pounds per square inch, if a perfect vacuum could be secured. It amounts in average engineering practice to from 12 to 13 pounds, or 24 to 26 inches of mercury, as the graduations usually read on vacuum gauges.

37

Jet and Surface Condensers are further described and illustrated in a special allotted section of this work. The vacuum pump is usually of the reciprocating order, although other methods have been employed for emptying condensers, but not with equally satisfactory results.

The gain to be secured by using a condensing apparatus may be measured in two ways: first, by the decrease in fuel consumption over that necessary when running non-condensing, which will represent a constant decrease in running expenses; or, second, by the increase of power working quite up to its economical limit, in a non-condensing engine.

By the use of a condenser a further increase of power is realized in raising the mean effective pressure of steam within the engine cylinder without increasing the demand upon the boiler.

The application of a condenser to a steam engine increases its economy from 20% to 25% depending upon circumstances, while by compounding and condensing an economy of 35% to 40% is effected.

The vacuum pump shown in the engraving, Fig. 346, represents a single cylinder double acting vertical design having but one set of valves and those used exclusively for the discharge.

The suction port is in the middle of the cylinder, A, shown in the sectional view, Fig. 347. The piston, E, when it passes this port imprisons the water beyond it and pushes this water out of the discharge valves, D D, if the piston is rising, and out of the valves, C C, if the piston is descending. The main discharge pipe is attached to a flange at B.

This pump is made to work easily and steadily by adjusting the cushioning valves, F. F.

38

The discharge valves are reached through the holes provided for that purpose and covered by plates shown in the engraving, Fig. 347.

The main slide valve moves horizontally for the reason that if it moved up and down the force of gravity would seriously interfere with its regular action.

This slide is moved by a valve piston in the usual way. The parts of the valve may be inspected and adjusted by removing the cover held by the two studs shown.

The outline engraving, Fig. 348, shows a cross-compound double acting vacuum pump, six-inch high pressure, nine-inch low pressure cylinders, by eight-inch stroke, and two air cylinders, ten-inch diameter by eight-inch stroke.

They are piped up to run either high or low pressure, also to run independently by manipulating the cocks, C, and D, as directed in the engraving showing arrangement of valves, Fig. 349, page 41.

Fig. 346.

These pipes are simple in design and run direct to the boiler for live steam and convey the exhaust to the atmosphere or condenser as desired. On a recent test at a fair rate of speed the capacity of this39 pump was shown to be equivalent to taking care of a triple expansion engine of 2,000 I. H. P. On a further test this same pump on a basis of 20 lbs. weight of steam per I. H. P. per hour demonstrated its ability to take care of 3,000 I. H. P. triple expansion engine.

The advantages claimed for this pump are briefly as follows:

Unusual light weight and compactness.

There being NO SUCTION VALVES, working-beams, rock shaft and bearings, beam-links, etc., this pump is simple.

It is economical in the use of steam, by reason of compounding the steam cylinders; also clearance loss is reduced to a minimum by the perfect regulation that is secured by the valve gear described. Full stroke at any and all speeds can be readily maintained.

As the air pistons travel within a distance of less than ¹⁄₈ inch of the air cylinder heads, a high efficiency results. Although double-acting, the flow of water and vapors is always in one continuous direction—the same as in a single-acting air pump. Either side of pump can run independent of the other, which means a spare pump to be used in case of accident to the other side of this pump.

Fig. 347.

40

Fig. 348.

Referring to the accompanying table of tests, page 41, it may be claimed that with an average of 36 double strokes per minute this pump handled at the rate of upwards of 26,000 pounds of feed-water per hour, which on a basis of 20 lbs. engine economy shows this vacuum pump capable of taking41 care of a 1,300 I. H. P. engine at this very moderate speed. By comparing the power required to drive this pump (which aggregated 1.18 I. H. P.) to the I. H. P. of an engine of the power here represented it is apparent that this pump did its work on less than one-eleventh of one per cent. of the I. H. P. of said engine, which is a very excellent showing.

Fig. 349.—See page 38.

Table No. 4 also shows a very excellent vacuum maintained under extreme duty.

Table.

42

Fig. 350.

43

The Deane Vacuum Pump. There are a number of novel features exhibited in the construction of this pump; the cylinder has four ports, that is to say two steam or admission ports and two compression or cushioning ports.

Referring to the engraving, page 42, Fig. 6, shows the main valve to be a plain D slide,—directly under it the same valve is shown in section. The projection on the back of this valve fits into the valve piston. The secondary valve, 5, surrounds the main valve and contains two plain slide valves, one on each side. Referring to 3, it will be noted that one of these valves admits steam while the other allows the steam to escape after having done its work of moving the valve piston.

A longitudinal section of this secondary valve and steam cylinder are shown, in 2.

In the engraving, 1, it is shown that the cylinder for each end of the valve piston is jacketed with live steam so that the cylinder itself heats up as quickly as the valve piston, hence the piston cannot stick in the cylinder due to unequal expansion of valve and seat.

The supplemental valve ports are shown in section 4.

To set the valve of this pump: Remove the steam chest, place the piston at mid stroke with the lever, plumb, then set the stem at its mid position with the secondary valve in place. See that the tappets measure equal distances either side of the tappet block.

44

Fig. 351.

The water end of this pump consists of a cylinder with valve chambers as shown. The piston rod has two stuffing-boxes, which makes a water seal around the rod so that no air can enter the cylinder, as the chamber between the two stuffing-boxes is kept constantly filled with water. It will be noticed45 that the suction pipe enters the pump in such a position in relation to the valves that both suction and discharge valves are perpetually immersed in water.

When this pump is pumping air only, there is sufficient water left within the valve chambers to provide a water seal under all working conditions. The valves in this pump are easily reached for inspection or repairs, a hand-hole being provided for each valve, with proper covers, which are easily and quickly replaced.

The Worthington Vertical Beam Vacuum Pump with condenser attached is shown in Fig. 351.

This is a pump of great simplicity and strength. The figure shows a compound engine for using high pressure steam; these machines can be built with simple steam cylinders of equal diameters, but they are not recommended except in special cases; for example where the steam pressure is very low. Each side of the pump end is single-acting, the buckets being of the form used for years in detached air pumps in marine service. The two sides are connected together by a beam and links attached to the cross-heads. As one side comes down and does little work, the other side makes an up-stroke and does full duty in emptying the condenser to which the suction is attached.

The condensing chamber is usually placed at the rear and connects directly with the channel plate at the bottom of the pump. The opening shown in front is for the discharge water.

The steam cylinders are so arranged that either piston may be examined by removing its cylinder head, without disturbing the other cylinders. The valves are of the Corliss, or semi-rotative, type and the high-pressure cylinders are provided with cut-off valves to assure the desired ratio of expansion.

The interior of each air cylinder may be inspected by removing the plates shown in front, near the middle. There are also two plates at the top for inspection of the discharge valves. The four machinery steel columns form a light but very strong frame allowing free access to the working parts.

46

Fig. 352.

47

The next four cuts show Dean Brothers’ twin cylinder air pumps with their special steam valve gear. They are made for and supplied with either surface or jet condensers. See Fig. 352.

The arrangement of the valve gear is such that steam will be applied at the upper end of one piston at the same instant that it begins to act on the lower end of the other. By this device steam is so controlled in the steam chests that no pressure comes on the main pistons, until the moment that both are ready to move, after having reached the full limit of their stroke, thereby securing an exactly uniform, but opposite, motion of the pistons. Fig. 354 is a sectional elevation of the steam cylinder and steam chest; Fig. 353, a front elevation; Fig. 355, a section of the air cylinder, and Fig. 352, an exterior perspective view of the pump.

Each steam cylinder has its own steam piston, piston rod, valve movement, steam chest, etc. A sleeve, a, is rigidly attached to each piston rod, and connected to this sleeve is a lever, b, the outer end of which connects with a link, c, which in turn is connected to a sleeve, d, loosely mounted upon the valve rod between collars, e. The valve rod, f, operates the auxiliary slide valve and admits the steam from above and below the auxiliary piston. This piston has attached thereto the main slide valve, which admits and exhausts steam alternately from above and below the main steam pistons. Any movement of the main piston communicates movement in the opposite direction to the sleeve, d, which moves the valve rod only when it strikes one or the other of the collars. As there is considerable lost motion between the sleeve and the collars, the main steam piston will be nearing the end of its stroke when the valve rod begins to move.

Fig. 353.

Extending through the ends of the steam chests are short piston rods, g, which are connected to a centrally pivoted vibrating lever, h, mounted on a pivot. When the main steam piston has moved from the top to the bottom of the steam48 cylinder, the corresponding valve rod has moved in the opposite direction and the auxiliary slide valve has moved upward, opening the port, i, to steam and the port, k, to the exhaust port. At the moment the main steam piston has completed its downward stroke the auxiliary piston is forced upward and carries with it the main slide valve, l. This opens the main steam port and exhaust port, which reverses the movement of the main piston. When the main piston reaches the upward49 limit of its stroke the auxiliary valve has moved downward, opening the port, k, to steam and the port, i, to the exhaust, causing the auxiliary piston to move downward, thus reversing the movement of the main valve and piston.

Fig. 354.

By this arrangement the valve operating piston, m, is held at all times immovably at one end of the stroke, except when the main piston is nearing the end of its stroke and is ready to reverse. Supposing the left-hand main piston has not quite reached the upper limit of the stroke, the steam would still be on the lower side of its auxiliary or main valve operating piston and the exhaust open to the other side. We now have steam on the bottom side of both auxiliary pistons, and as they are of equal diameters and are connected by the lever, h, they are balanced and cannot move the main steam valves. The right-hand main steam piston must wait until the left-hand piston has completed its stroke before it can reverse, and consequently the movement of the main pistons will always be in opposite directions, and neither can reverse until both have completed their stroke.

50

There are three ways that this apparatus may be operated: First, the pumps may be operated in conjunction with each other, as is hereinbefore described. Second, the lever, h, may be detached from the auxiliary or main valve operating pistons, and the two pumps may then run independently of each other or in the ordinary and well-known manner, each performing its own independent work. Third, by further detaching the link, c, on one of the valve gears the auxiliary slide valve, n, will remain at rest and the corresponding pump will not move while the other pump continues to operate. These are important features, because, as in case of accident, it may be necessary to use one pump while the other is disabled, and in some cases it may be desirable to operate the pumps independently. The engineer will appreciate this feature, as the stoppage of an air pump is a serious matter.

Fig. 355.

The piston rods are separable at the crossheads. The crossheads are of steel. The steam cylinders and pump cylinders are connected by six heavy steel stretcher rods. Adjusting valves are fitted to steam cylinders for controlling motion of pistons. The valve gear is provided with a special lever adjustment by which the length of stroke of pistons may at any time be changed, even while the pump is running.

In Fig. 356 is shown a form of independent vacuum pump, with its condenser, built by the Conover Mfg. Co.

This apparatus consists of a jet condenser with air pump, boiler feed pump, and engine to drive both, combined as one machine. The air pump is a single acting bucket plunger pump, driven by a crank shaft, turned by the engine, which is a single cylinder compound automatic cut-off engine, and also drives the boiler feed pump; it is of the trunk pattern, and the small space around the trunk on the top side of the piston forms the high pressure cylinder. Steam is admitted to the high pressure side, at boiler pressure, and is cut off and expanded and exhausted into the receiver, whence it is admitted under the bottom side of the piston, where it is again cut off and expanded, finally exhausting into the condenser.

51

The piston makes the down stroke when the air pump makes the up stroke; and it will be seen by referring to the cut that the engine does nearly all its work when making the downward stroke. When steam is acting on the top side of piston at high pressure, the vacuum at the same time is pulling on the full area of the piston underneath.

Fig. 356.

When the engine makes the up stroke, the steam at low pressure from the receiver acts to push the piston up; and as the air pump is doing no work then, being on its down stroke, the only work of the engine is to keep the machine up to speed.

52

Fig. 357.

53

It will thus be seen that the engine is suited to meet the demand of the large power on one stroke, and very little on the other, thus adapting itself admirably to its requirements.

The valves are of the Corliss type, and do not trip; the cut-off being set by hand, does not require to be changed or altered, as the speed is controlled by a throttling governor.

Fig. 357 shows a cross section through the steam cylinder of this vacuum pump.

Fig. 358.

The Edwards air and vacuum pump is shown in Figs. 358, 359 and 360, in which it may be perceived that both foot and bucket valves are dispensed with; the only valves used are those which in other pumps are known as head or discharge valves.

The following brief description of its leading features will be understood by reference to the illustrations: Fig. 358 is a sectional view through the center of the air pump, but the piston and rod are shown as a full view.

The action of this pump is as follows: the condensed steam flows continuously by gravity from the condenser into the base54 of the pump, and is there dealt with mechanically by the conical bucket working in connection with a base of similar shape. Upon the descent of the bucket the water is projected silently and without shock at a high velocity through the ports into the working barrel (see Fig. 359). The rising water is followed by the rising bucket, which closes the ports, and, sweeping the air and water before it, discharges them through the valve at the top of the barrel.

Fig. 359.

It may be said that however slowly an ordinary air pump with foot and bucket valves may be running, the pressure in the condenser has to be sufficiently above that in the pump to lift the foot valves, overcome the inertia of the water, and drive the water up through the valves into the barrel where the water is dealt with mechanically. The higher the speed of the older type of pump the greater is the pressure required to overcome these resistances owing to the very short space of time available, and as any increase of pressure in the condenser is accompanied by a corresponding increase of back pressure in the55 low pressure cylinder, hence the absence of the valves referred to allows a higher speed of the plunger. The elimination of the foot valves it is claimed gives from ¹⁄₂ to 1 inch better vacuum.

Fig. 360.

Another advantage claimed for this pump is that clear air inlets are maintained—see Figs. 359 and 360. Under ordinary working conditions, when the bucket descends and the ports open, there is no obstruction between the condenser and the pump; the air has a free entrance while immediately afterward the water is injected into the barrel at a high velocity. Thus, instead of obstructing the entrance of the air, the water tends to compress that already in the barrel, and to entrain or carry in more air with it.

The bucket or piston is a hollow casting with water grooves instead of packing rings.

The valve seat is constructed with a rib between each valve and a lip around the outer edge, so that each valve stands in its own water and is separated from the others. This forms a ready means of testing the relative tightness of each valve.

The cast iron working barrel is lined with brass.

The pump rod is Tobin bronze, and valve plate and valves of composition. These pumps are either single, twin, triplex, and are steam, electric or belt driven, for stationary, marine or sugar plantation service.

The steam driven pumps are built with either single or compound steam cylinders, fitted with new and improved valve gear, and with their arrangement of fly-wheels, insures smooth running, making full strokes free from vibration.

56

Fig. 361.—See page 70.

Compressed air is air compressed by mechanical force into a state of more or less increased density. The power obtained from the expansion of greatly compressed air in a cylinder, on being set free is used in many applications as a substitute for steam or other force as in operating drills, shop tools and engines which are driven by the elastic force of compressed air.

A compressor is a machine usually driven by steam by which air is compressed in a receiver so that its expansion may be utilized as a source of power at distances where an ordinary engine could not be conveniently used.

The compressor proper comprises two sets of valves, usually designed to be opened automatically by excess of pressure under them and to be closed by gravity or by the action of springs when the pressures become equal. The inlet valves open just after the piston commences its stroke, when the expansion of the compressed air remaining in the cylinder behind the piston has lowered the pressure above the valves. They close at the end of the intake stroke, just as the piston comes to rest. The outlet valve lifts during the compression stroke, at about the time the rising pressure in the cylinder becomes equal to that in the outlet passage above the valves; and they close when the flow of air ceases as the piston completes its stroke.

Any of the accurately fitted steam engine valve gears may be used for compressors, observing only that the compressor is in every way a reversed steam engine.

Compressed air is already used in the operation of
1. Cranes, hoists and motors of all types and of all capacities.
2. Portable drilling, reaming and tapping machines.
3. Riveters and stay-bolt cutters, calking and chipping tools.
4. Shop tools of all kinds.
5. Air brakes.
6. Sand blasts.
7. Rock drills and coal mining machines.
8. Pneumatic locomotives and street cars.

58

Fig. 362.—see page 70.

59

and also for the following diversified uses,
1. Pumping water, sewage, oil and acids.
2. Raising sunken vessels.
3. Refrigerating and ice making.
4. Transmitting messages through pneumatic tubes.
5. Cleaning carpets and railroad cars and seats.
6. Sinking caissons and driving tunnels through silt and soft earth.
7. Tapping iron furnaces.
8. Transmitting power for all purposes.

The office of the air compressor is to store up air under high pressures, which can be utilized at a greater or less distance, without sustaining any loss by condensation in the pipes, as is the case of carrying steam in pipes long distances.

Air stored under pressure in a reservoir can be used expansively, in an ordinary steam engine returning an equivalent amount of work that was required to compress it—less the friction.

The admission of the air being through a single tube, it creates a constant flow of air in one direction only, thus filling the cylinder at each stroke with air at atmospheric pressure. This movement gives a momentum to the air which causes it to fill the cylinder to its fullest extent at each stroke.

Air compressors may be driven in various ways, but the most commonly used are those which are directly connected to a steam engine, thus doing away with intermediate machinery. When the air piston draws in a charge of air, the air fills the cylinder at atmospheric pressure, or a little below, and on the return stroke of the piston it has to be compressed to the same pressure as in the receiver before it can lift the delivery valve, and as the valve is held to its seat by a spring, and also by its own weight, the pressure has to be considerably above that of the receiver before the valve will lift. To overcome this the valves are operated by mechanical means, which lifts them at a point of the stroke, when the pressure in the cylinder corresponds with that of the receiver.

60

Fig. 363.—See page 71.

61

This arrangement avoids pounding of the valves as well as the noise caused by the air when rushing at much higher pressure from the cylinder into the receiver.

For the sake of economy, air compressors are compounded, as for example, by drawing the air into a large cylinder and compressing it to a certain stage, whence it passes into a smaller cylinder, which compresses it to a much higher pressure.

In a simple compressor, for very high pressures, there is at the end of the stroke a large volume of air left in the clearance space, which expands on the return stroke, to atmospheric pressure, before another charge of air can be drawn in.

But in the compound compressor, the air is delivered from the low pressure receiver to the high pressure cylinder far above atmospheric pressure, thus the remaining air need not expand so much and allows the cylinder to take a larger volume of air. The load is also distributed more evenly.

The following are valuable “points” relating to the care and management of air compressors.

As in a steam pipe line, elbows should be avoided in an air pipe line but unlike a steam pipe it should be larger.

A mistake is sometimes made in purchasing a compressor built for a low altitude and trying to run it in a higher elevation; the machine then experiences the same trouble that some people do, in not being able to get breath enough under the changed conditions.

The use of cheap oils, especially in an air cylinder is a most serious mistake, as the least tendency to gum will prevent the valves from properly seating, and even with the best of oils, it is well to use a small amount of mineral oil at times.

In localities where the water is bad, the water jacket will require extra attention, as it gets as badly scaled like steam boilers, principally due to a very slow or retarded circulation, which allows the sediment to settle, and should the water supply be shut off, even for a few minutes, the cylinder heat will bake it so hard as to give considerable trouble. It is a good plan to put a good boiler compound in the water jacket, and run the machine for some time without any circulation.

62

Fig. 364. (See page 71.)

63 In this case good judgment must be used not to run too long or too fast, as the cylinder will heat very quickly and is liable to be damaged.

There are many emergency ways of stopping small pipe leaks; any good sticky substance, such as tar, wax, tallow candles, or even chewing gum, melted and applied on narrow strips of cloth and wound as a bandage, will be found handy.

It should be remembered that leaks in an air pipe line are as bad as in a steam pipe line, and should receive as much care.

The theoretical operation of air compressors may be thus explained:

If a tight cylindrical vessel, containing one cubic foot of air at atmospheric pressure, be fitted with a piston which is free to move up and down but yet perfectly tight, the air in the vessel will have no means of escape, and the pressure within and without the vessel, both being atmospheric, are balanced.

Now, if the piston should be loaded with a weight, the pressure on the outside would be that due to the atmosphere, plus the weight, while the pressure from the inside is simply equal to atmospheric pressure; thus the piston is forced to descend, but as the air inside of the cylinder has no means of escape, the volume it fills being diminished, its pressure rises until the pressure under the piston balances that above it.

If, for example, the area of the piston should be 100 square inches, and the weight with which it is loaded be 100 pounds, assuming the piston to be without weight, the pressure below will have to react with an equal force to hold the piston stationary, which in this case would be 1 pound to the square inch above atmospheric pressure, and the piston would have to descend sufficiently to cause this increase of pressure, which descent would be equal to ¹⁄₁₆ of the total fall of the piston. By adding another 100 pounds above, the pressure would rise to 2 pounds to the square inch. The cylinder is thus charged with compressed air.

64

Fig. 365. (See page 71.)

65

If now the bottom of the cylinder should be connected by means of a pipe to another vessel of larger capacity called a receiver, the pipe having been closed by a valve in it during compression, and the valve should be opened, the piston would at once commence a further descent, the compressed air escaping into the receiver, until the pressure in the receiver and cylinder is equalized, or the piston reaches the bottom of the cylinder, which it will do, if the receiver is large enough. Then the valve closes, stopping communication between cylinder and receiver, and the piston is drawn upward; at the same time air is again admitted to the cylinder by another valve, which closes when the piston reaches the top, and the same operation is again repeated.

The receiver can thus be charged with compressed air and by loading the piston very heavy the pressure can be raised quite high.

Now, if the piston, instead of being loaded by weights, be connected to the piston rod of a steam engine, or by means of a connecting rod to a crank (which is rotated by a belt or some other driving mechanism, and the valves be operated automatically, as the valves on a water pump), the simple apparatus is converted into a perfect air compressor, which really is nothing else than an air pump, and the air can be pumped into the receiver against a high pressure the same as water is forced into an elevated reservoir by a pump.

As air is a compressible gas, it acts a little different in the air cylinder from the almost incompressible water in a pump.

To lift the valves of an air compressor by the compressed air pressure in the cylinder (added to the pressure of their springs besides the receiver pressure), the air would have to be compressed considerably above the receiver pressure before it would lift the valve which allows it to flow from the cylinder into the receiver, and then the valve would not open freely as a pump valve, but would chatter, causing a disagreeable noise, and damaging the valve.

To avoid this, the valves of an air compressor are operated by mechanical means. Some devices operate the valve directly as soon as the pressure in the cylinder reaches that of the receiver, while others simply release it of the spring pressure, the valve itself being lifted by the air itself. Such devices generally give the valves a full free opening, without noise.

66

Fig. 366.

67

The blowing engine is almost identical with the air compressor. The chief difference between them being the ratio of steam cylinder to air cylinder. While the air compressor furnishes a comparatively small amount of air at very high pressures, the blowing engine delivers a very large volume at lower pressures.

Blowing engines are mainly used in large blast furnaces, smelting works and foundries, to furnish the air pressure for cupolas, air furnaces and smelting ovens.

In Fig. 366 is shown a blowing engine of very large size; the steam cylinder is 42 inches in diameter, the air cylinder 84 inches, and the stroke 60 inches.

The valve gear is of the Reynolds-Corliss type. The piston rod is attached to a cross-head extending through the guides, which are formed by the frame, with wrist pins upon each end, from which the two connecting rods are suspended with their lower ends connected to the cranks, as shown in Fig. 366. There are two air piston rods attached to the main piston and held to the cross-head by nuts at points near the guides.

The crank shaft carrying the flywheels, which also form the cranks attached to the ends of this shaft, is located below the steam cylinder. This construction is of the return connecting rod engine design, to economize space.

Both the air and steam valve gears are worked from eccentrics on an auxiliary shaft, driven from the main shaft by bevel gears underneath the steam cylinder.

The “Imperial” air compressor is presented herewith in Figs. 367 and 368.

The “Imperial” compressor is especially designed for use in machine shops, foundries and other industrial establishments where it is not convenient to use a steam driven compressor.

The machine has two vertical, single-acting cylinders, each employing long trunk pistons that act as guides for the lower ends of the connecting rods. By this design, the height of the machine is reduced, stuffing-boxes and crossheads are eliminated, and a minimum number of bearings required. The68 cranks are set opposite to each other, so that when the piston on one side is ascending, the other side is descending.

Fig. 367.

The machine is made with duplex cylinders for the low pressures used in sand blast work and the like, and with either duplex or compound cylinders for higher pressures. In the compound type, an intercooler is supplied, through which the air passes from the low pressure to the high pressure cylinder.

69

The air cylinders are water-jacketed and provided with hooded heads, so that air may be supplied to them from outside the compressor-room; the cylinders are cast in one piece with the frame.

Fig. 368.

The air-valves, both inlet and outlet, are of the poppet type, fitted with light springs, and work vertically. On account of their position at the bottom of the cylinder, they are well70 lubricated, and, acting vertically, they have little tendency to wear out of line with their seats.

The air intake passage is tapped to receive a supply pipe leading from out-of-doors, or from some place where cool and clean air is obtainable. The compressed air is discharged into a passage which is tapped for a pipe to convey it to the air-receiver.

All parts of the compressor are easily accessible for inspection, adjustment, or repair. The air-heads may be removed without disturbing any of the pipe connections. The valves may be taken out by unscrewing the bonnets.

Table
of parts of the Imperial Compressor.

The Norwalk standard compressor is shown in Figs. 361 and 362, the latter being a longitudinal section; Fig. 361 is a perspective view; the two compressors are driven by a single steam71 cylinder having an adjustable cut-off. The air valves are operated by a positive crank motion.

A view of a Pelton water wheel operating a compressor it shown in Fig. 363. The cut represents a compound air compressor in which the valves are operated mechanically. The water which drives the wheel enters through the pipe and nozzle secured in the wheel pit, as represented.

Fig. 364 exhibits a belted duplex air compressor built by Allis-Chalmers & Co.

Fig. 365 shows a vertical duplex compressor driven by a belt.

Fig. 369.

All the latter, as may be seen by the engravings, have the positive valve motion operated by an eccentric. In selecting an air compressor the following points need consideration: 1, Number of cubic feet of free air required per minute; 2, Altitude, i.e., the number of feet above the sea level; 3, Steam pressure and air pressure.

The use of compressed air for operating mining pumps, while having advantages in some cases, is not to be recommended in all, particularly on account of the low efficiency of the plant as a whole. The loss due to leaks is serious, and the long line of piping with its numerous joints causes much trouble, delay and expense.

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In Fig. 369 is shown a direct acting steam single air compressor; simplicity in its construction is a leading feature and there are few parts in this pump that are liable to wear.

Figs. 370 and 371.

This apparatus is designed for working pressures up to twenty pounds; it is intended for use in oil refineries, smelting works, blast furnaces and in all situations where compressed air of medium pressure is required. They are variously used for sand blasts, ventilating purposes, and for pneumatic deliveries.

The steam end and valve motion are the regular Deane pattern, assuring positive operation. The air cylinder is provided with a water jacket.

Fig. 372.

A power wall or post air compressor is shown in Figs. 370-372. The machine is single acting and is recommended where little space is available, as it can be bolted to the wall or to a post, or on the under side of the ceiling. The crank shaft and connecting rod are of cast steel. The bearings are babbitted and adjustable. The piston is of the trunk form, carrying a pin for the connecting rod, and is of extra length to73 act as a guide for the lower end of the connecting rod. The valves are of the poppet type. These compressors are extensively used in electric power stations for supplying air for removing dust from electric machinery, in bicycle shops for inflating pneumatic tires, maintaining a supply of air in pressure tanks, and for various purposes where a limited supply of air is needed.

These compressors are of the “Blake” design and the following particulars will be of interest.

With increase in altitude the barometric or atmospheric pressure falls from 14.7 pounds per square inch at sea level to about 10 pounds at 10,000 feet above sea level. Since the density of the air decreases with its pressure it is obvious that at such an altitude the total weight of air handled by a given displacement is considerably less than at sea level; and that to fill any volume—a rock drill cylinder, for instance—with air compressed to 90 pounds, a greater free-air displacement will be necessary than would be required at sea level. The relative74 capacities of a given displacement to do work—as through rock drills or pumps—at varying altitudes are figured in the following table:

Capacities at Varying Heights above Sea Level.

The fact that the heating effect of compressing air from an initial pressure of 10 pounds absolute to 90 pounds gauge pressure is theoretically equivalent to that of compression to 132 pounds at sea level, makes a two-stage arrangement more imperative in high level work than under ordinary conditions.

Fig. 373.

The two-stage or multi-stage system of air compression is used generally for high pressure work. The system is most usefully employed between 40 and 120 pounds gauge pressure. For the moderate working pressure of 90 to 100 lbs., the two-stage compression has demonstrated its efficiency chiefly for the reason, that the heat generated in the last half of the stroke75 of a single compressor is by the two-stage process greatly reduced.

Further compounding, for pressures above 100 pounds, becomes quite necessary to secure the advantages named hereafter; the two-stage has proved advantageous up to 500 lbs., three-stage up to 1,000 lbs., and four-stage compression up to 3,000 lbs.

Fig. 374.

As the pressures increase, however, the machines become more and more complicated, owing not only to the greater power required, but also to the heating of the air during compression. The use of water-jackets for cooling the air in the compression cylinders is general, but this does not effect thorough cooling, as only a small portion of the air in the cylinder comes in contact with the jacketed parts. This difficulty has led to the use of compound machines, in which case inter-coolers are generally used between the different stages of compression, which cause the air to shrink in volume between the stages.

Briefly summed up, the chief advantages of multi-stage over single-stage compression are:

1. Lower average temperature, resulting in lower average pressure, and permitting the compression of the same volume of air with less expenditure of energy.

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2. Increased safety and ease of lubrication. When high final temperatures prevail, part of the lubricating oil vaporizes, and wear on the piston and cylinder becomes rapid. Under exceptional circumstances the combination of air and oil vapor may reach the proportions of an explosive mixture, and if the compression temperature passes its flash point damage may result. Such accidents are, however, very rare even in single-stage work; in multi-stage compression, with proper intercooling, they are impossible.

3. Greater effective capacity in free air. The final pressure in the low pressure cylinder is much lower than in a single-stage machine, and the air confined in the clearance spaces when expanded down to atmospheric pressure occupies comparatively little space. Consequently the inflow of air through the suction valves begins at an earlier point in the stroke.

4. The air delivered by a two-stage or multi-stage compressor is dryer than that furnished by a single cylinder. Under constant pressure the power of air to hold watery vapor decreases with its temperature, and during its passage through the inter-cooler much of the original moisture in the air is precipitated. Consequently less trouble is experienced from condensation in the discharge pipe.

A properly designed inter-cooler should reduce the air in the cylinders to the temperature of the outside air. The economy of compressing in several stages—or, in other words, compound compressors—is shown from the fact that in compressing air up to 100 lbs. the heat loss reaches about 30 per cent. By compressing in two stages, this loss is cut down to less than half; and in four stages, it is reduced to four or five per cent. It is evident, therefore, that the higher the pressure required the more essential is the use of compound machines.

The inter-cooler is the vital feature of the two-stage or multi-stage machine. In this construction the air is partially compressed in one cylinder; it is then passed through an inter-cooler where it is cooled and finally is compressed to the desired degree in the second or other additional cylinders.

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An inter-cooler is shown in Fig. 373. The cooling surface consists of a nest of small brass water tubes. These tubes break up the stream of air entering the cooler, while their thin walls insure rapid conduction. The receiver volume formed by the connecting pipes and inter-cooler body results in a nearly uniform discharge pressure in the low-pressure cylinder. The air being outside of the tubes encounters practically no frictional resistance, and its slow passage allows time for cooling. A pocket, with gauge glass attached, is so placed as to catch any precipitated moisture which might otherwise enter the high-pressure cylinder.

An after-cooler is shown in Fig. 374. This serves to reduce the temperature of the air after the final compression.

The heat of compression, as may be judged from the foregoing, relating to inter and after-coolers is a feature of interest. The temperature to which it finally attains depends, 1, upon the initial temperature; 2, upon the degree of compression, or in other words, the amount of work expended upon the compression.

The extent of this heating is shown in the following table, for dry air when compression is performed with no cooling.

The Norwalk compound compressor is shown in outline by the cut 375. The large air cylinder on the left determines the capacity of the compressor; for illustration assume its piston at 100 square inches area; the small air cylinder can have an area of thirty-three and one-third square inches.

The small piston only encounters the heaviest pressure; at 100 pounds pressure the resistance to its advance is 3,333 pounds. The resistance against the large piston is its area multiplied by the pressure which is caused by forcing the air from the large cylinder into the smaller cylinder. In this case78 it is thirty pounds per square inch. But as this thirty pounds pressure acts on the back of the small piston, and hence assists the machine, the net resistance to forcing the air from the large into the small cylinder is equal to the difference of the area of the two pistons multiplied by the thirty pounds pressure. This is sixty-six and two-thirds by thirty, and equals 2,000 pounds.

Hence 2,000 pounds, the resistance to forcing the air from the larger into the smaller cylinder, plus 3,333 pounds, the resistance in the smaller cylinder to compressing it to 100 pounds, is the sum of all the resistances in the compound cylinders at the time of greatest effort. This is 5,333 pounds. By thus reducing the work to be done at the end of the stroke, more work is done in the first part, and the resistance is made nearly uniform for the whole stroke.

Fig. 375.

The Air Lift is one of the simplest methods of raising water from underground sources. The main principle of its operation may be stated thus: air under pressure is conveyed into the lower end of the water pipe through a suitable foot piece.

Fig. 376.

Fig. 377.

City and town water works, asylums and hospitals, plantations, railway water tanks, irrigation, private country houses, pumping mines, ice manufactories, breweries, cold storage and packing houses, textile mills, dye works, bleacheries, sewerage installations, dry docks, seaside water works, stock farms; in fact, everywhere that clear and abundant water is needed are opportunities for the application of the Air Lift System of pumping water.

Nor is it alone for securing public water supplies that the Air Lift is of special value. Within recent years the question of an abundant[80] and pure water supply for manufacturing, irrigation and other uses has become one of equal importance. After an extensive experience, two general systems have been devised for utilizing the water which lies immediately below the surface of the ground. One, known as the Deep-well Pump System, for which a working pump is used, and the other the Air Lift System, which employs compressed air to raise the water, either by means of its inherent expansive force or the difference in specific gravity between compressed air and water.

Theory of the Air Lift. Opinions differ as to the true theory of the Air Lift. A common Air Lift case is one where there is a driven well in which the water has risen approximately near the surface. In this well is placed a large pipe for the discharge of the water, which is known as an “eduction pipe.”

Fig. 378.

This pipe does not touch the bottom of the well, but is elevated above it so as to freely admit the water through its lower open end. Alongside of this pipe, either on the outside or within, is a small pipe properly proportioned and intended to convey compressed air to a point near the bottom of the eduction pipe. It is usual81 to provide a “foot-piece,” see Fig. 378, which forms a nozzle connecting the air pipe with the water pipe, but in what is known as the “central pipe system” this foot-piece is not used, the air pipe being placed within the eduction-pipe to a point near the bottom, where it discharges the compressed air into the water column.

Many neighborhoods are dependent upon well water, and there are few districts where an ample supply is not to be secured from wells properly made; this water is generally pure and wholesome. It is also of uniform temperature the year round—cool and pleasant in the summer, because the underground pipe and earth temperature remain uniformly low. In winter, well water being warmer than that taken from ponds and rivers, is not so apt to freeze, and, from all considerations of temperature and purity, well water is greatly to be preferred. Many cities located on rivers having a gravel bed formation find that, by placing wells of suitable construction far enough back from the bank, there is a natural filter bed, leaving the water clear, even when the river itself is muddy. When river or other surface water is good the wells may be sunk close to the edge, the water flowing down from the top of the wells.

There are not many underground formations where wells should be located close together. Such wells may affect or rob each other, and it is usually best to spread them out on a line across what is known to be the underground flow. Some finely creviced or tight rock formations have a strong head with but little capacity, and wells in such formations, if pumped hard, yield but little additional water. They should be scattered and pumped moderately, maintaining a low and economical lift. In other cases, one well in a group will give as much water as all together, and more territory must be drawn on.

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Figs. 379-382.

The Pohle system of elevating liquids is shown in Fig. 377. The process “consists in submerging a portion of an open-ended eduction-pipe in a body of the liquid to be raised and continuously introducing into the liquid within the lower part of the pipe a series of bubbles of compressed gaseous fluid containing enough of the fluid to expand immediately across the83 pipe and fill the same from side to side, forming pipe-fitting piston-like layers at or just above the point of their entrance into the pipe, whereby the column of liquid rising in the pipe after the forcing out of the liquid first standing in the latter is subdivided by the gaseous fluid into small portions before it reaches the level of the liquid outside of the pipe, and a continuously upward-flowing series of well-defined alternate layers of gaseous fluid and short layers of liquid is formed and forced up the pipe.”

The figures represent the apparatus in a state of action pumping water, the shaded sections within the eduction-pipe, W, representing water-layers and the intervening blank spaces air-layers.

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The air pipe is connected with an air receiver on the surface, which is at or near the engine room, in which there is an air compressor. This air pipe is provided with a valve on the surface. Before turning on the air the conditions in the well show water at the same level on the outside and inside of the eduction-pipe. At the first operation there must be sufficient air pressure to discharge the column of water which stands in the eduction-pipe.

This goes out en masse, after which the pump assumes a normal condition, the air pressure being lowered and standing at such a point as corresponds with the normal conditions in the well. This is determined by the volume of water which the well will yield in a certain time and the elevation to which the water is discharged.

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After the standing water column has been thrown off by the pressure the air rises through the water reduces its weight, with the result that the water is expelled as fast as the well supplies it, the water outside the pipe, acting as a head, flows into the discharge pipe by the force of gravity.

The machinery necessary for a system of pumping comprises, 1, an air compressor; 2, a receiver to store and equalize the pressure; 3, the head piece and foot piece for the well; and, 4, the necessary piping for the air supply and water discharge.

Fig. 383.

With an available supply of air under pressure the pump proper consists of simply a water discharge and air pipe, the latter arranged and properly controlled to inject air into the former at the point of proper submersion. It is readily seen that the apparatus86 is so simple that as a pump it cannot get out of order; in cases, where mud, sand or gritty material is encountered, it will handle such matter with the water and without injury to the system, as nothing comes in contact with the moving parts.

Figs. 384, 385.

Absence of all obstructing mechanism in the wells allows each to be operated to its full capacity. Production, therefore, does not depend upon the pump, but rather upon the capacity of the well to yield water; the natural yield of wells is often increased by this process of using compressed air admitted87 close to the bottom of the discharge pipe, the water is set in motion at a considerable depth, and by this action the well is “cleaned.”

Purification is effected by aeration during the process of pumping, the absorption of air by the water preventing the formation of unsanitary growths.

Three styles of well heads are shown in Figs. 383, 384 and 385.

The deflector head, Fig. 383, is attached to the well casing or discharge pipe by standards. This form of head piece is generally used where the water is to be raised to the surface, or just below the surface into a tank, where the air is allowed to separate itself, and the water flows to some central collecting reservoir, where it is used or forced by means of an ordinary pump to a higher elevation. The head piece offers no obstruction to the discharged water.

The offset discharge, Fig. 384, is adapted to situations where the water is to be pumped by air direct from the well to some elevation above the well.

The elbow discharge, Fig. 385, shows the common form of well head known as the elbow head, adapted to be used either as a cap for the well casing itself, or used in connection with a suitable discharge pipe.

The foot piece, or nozzle, which regulates the admission of air to the discharge pipe at the point where the air comes in contact with the water, thereby makes it possible to carry air at full pressure to the end of the air pipe, and utilizes the energy due to the velocity of the discharged air.

After a well is once regulated or balanced there is but little occasion to move the adjusting wheel or valve, the starting and stopping of the flow of any particular well being accomplished by means of an ordinary valve or plug cock on the air pipe at or adjacent to the well.

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One Central Station of suitable capacity will operate several wells no matter how far apart. The necessity of maintaining a number of separate pumping plants is thus done away with, and in taking a supply of water from an underground source the wells can be located without reference to the power plant, and at such distances apart as will best maintain the highest average pumping level.

Although the principle of the action governing all pumps of this description is so simple, there are a number of factors having a direct influence upon the performance of the pump, which have been expressed in the following terms by a well-known expert:

It was at first supposed that in all Air Lift cases the water was discharged because of the aeration of the water in the eduction-pipe, due to the intimate co-mingling of air and water. Bubbles of air rising in a water column not only have a tendency to carry particles of water with the air, but the column is made lighter, and, with a submergence or weight of water on the outside of the eduction-pipe, there would naturally be a constant discharge of air and water. This is known as the Frizell System, and where the lifts are moderate—that is, where the water in the well reaches a point near the surface—it is very likely that the discharge is due to simple aeration.

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Most air lift propositions are deep-well cases—that is, the water is lifted a distance greater than 25 feet; and just in proportion as the lift is increased do we get away from the aerated form idea, and so when the air pressure is greater than the head of water, a certain volume of compressed air is received into the eduction-pipe, the water in this pipe is at that time moving rapidly upward; that is, its momentum has been established. Hence the air takes up this velocity and goes upward with the water from the energy received from the elasticity of the air due to its compressor.

A practical example of the successful working of an air compressor for raising water from a driven well 319 feet is described and illustrated by the Practical Engineer as shown in the sketch, Fig. 386.

Fig. 386.

The air compressor forces the air down the inside pipe, which is 1¹⁄₄″ in diameter. The outside pipe, which is 3″ in diameter, has its lower end submerged in the well. The compressed air forces a rising column of air mingled with water in the outer pipe to the supply tanks, which are situated at the top of the building.

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Direct Air Pressure Pumps. This term is applied to that class of pumps in which the liquid is taken into an air tight vessel and then driven out through pipes to a higher level by the application of compressed air directly on the surface of the liquid in the tank, thus dispensing with cylinders, pistons, valves, glands, etc., of the more common class of pumps.

Fig. 387.

Fig. 387 shows the parts of the pump; its operation is as follows: Suppose the compressor to be in operation and the switch set as in the figure; the air will be drawn out of the right tank and forced into the left tank, and in so doing will draw water into the former and force it out of the latter. The charge of air in the system is so adjusted that when one tank is emptied the other is filled, and at that moment the switch will be automatically thrown, reversing the pipe connections and thereby reversing the action in the tanks.

The Pneumatic Engineering Co. are the makers of this apparatus, named the Harris System of raising water by direct pressure.

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92

Fig. 388.

The steam fire engine is practically a portable pumping engine. It is in all respects a complete water works on a small scale, hence, a modern apparatus must, within itself, and each part working harmoniously with every other part, contain several complex mechanisms. This will readily appear by a study of the several succeeding illustrations; the first, which in the figure below exhibits a “view” of a complete machine.

Fig. 389.
(See page 109.)

Modern steam fire engines are classified as to “size,” as “double extra first,” etc.; their capacities and weights are given approximately in the following

Table.

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The foregoing list of the sizes, capacities, etc., of the fire apparatus now in general use, affords a very good comparison between it and that which has, little by little, progressed for two thousand years to its present high plane. The application of electric power to the operation of the pumps and the propulsion of the apparatus is yet in too elementary a stage for present discussion in a work of this scope for—

It is essential that the machinery relied upon for fire protection should at all times be ready for instantaneous and effective service; this, because both life and vast property interests are at stake, hence of all machines made, the modern steam fire engine is produced with a niceness of finish and accuracy of fit equaled by no other, when size is considered; it approaches towards the perfection seen in the mechanism of a fine watch.

Figs. 390, 391.

This degree of excellence has been arrived at by successive steps. The illustration on page 92, Fig. 388 exhibits the fire-fighting tools of the early Romans and similar apparatus was used in England as late as the fifteenth century. The implements shown are a syringe, a sledge hammer, two fire hooks and three leathern buckets conveniently arranged against a wall. The owners of houses or chimneys that took fire were fined; and men were appointed to watch for fires and give the alarm. In 1472 a night bellman was employed in Exeter to alarm the inhabitants in case of fire, and in 1558, leathern buckets, ladders and crooks, were ordered to be provided for the same city; no application of the pump seems to have been then thought of.

Syringes continued to be used in London till the latter part of the 17th century, when they were superseded by more improved machines. They were usually made of brass and held from two to four quarts. The smaller ones were about two feet and a half long, and an inch and a half in diameter; the95 bore of the nozzles being half an inch. Three men were required to work each, which they achieved in this manner: one man on each side, grasped the cylinder with one hand and the nozzle with the other; while the third man worked the piston! Those who held the instrument plunged the nozzle into a vessel of water, the operator then drew back the piston and thus charged the cylinder, and when it was raised by the bearers into the required position, he pushed in the piston and forced, or rather endeavored to force, the contents upon the fire.A

Fig. 392.

Figs. 390 and 391 show an early form of syringe. A description of it translated from the original Greek, written by Hero of the ancient city of Alexandria, reads thus—“A hollow tube of some length is made, A, B; into this another tube, C, D,96 is nicely fitted, to the extremity of which is fastened a small plate or piston; at, D, is a handle, E, F. Cover the orifice, A, of the tube, A, B, with a plate in which an extremely fine tube, G, H, is fixed, its bore communicating with A, B, through the plate—as a vacuum is thus produced in A, B, something else must enter to fill it, and as there is no other passage but through the mouth of the small tube we shall of necessity draw up through this any fluid that may be near.”

Fig. 392 is a copy of an old engraving (A. D. 1568) which shows an “engine” of this type sufficiently enlarged to contain a barrel or more of water and as a matter of necessity, placed on a carriage.

Fig. 393.

To eject the water uniformly, the inventor moved the piston by a screw; and when the cylinder was emptied, it was refilled through the funnel by an attendant, as the piston was drawn back by reversing the motion of the crank. When recharged, the stop cock in the pipe of the funnel was closed and the liquid forced out as before. As flexible pipes of leather, the “ball and socket” and “goose-neck” joints had not been introduced, some mode of changing the direction of the jet of this enormous syringe was necessary. To effect this, it is represented as suspended on pivots, fastened in two upright posts: to these are secured (see figure) two semi-circular straps of iron, whose centers coincide with the axis, or pivots, on which the syringe is balanced. A number of holes are made in each, and are so arranged as to be opposite each other. A bolt is passed through two of these, and also through a similar hole, in a piece of metal, that is firmly secured to the upper part of the open end of the cylinder; and thus holds the latter in any required position. The iron97 frame to which the box or female part of the screw is attached, is made fast to the cylinder; and it is through a projecting piece on the end of this frame that the bolt is passed. By these means, any elevation could be given to the nozzle, and the syringe could be secured by passing the bolt through the piece just mentioned, and through the corresponding holes in the straps. When a lateral change in the jet was required, the whole machine was moved by a man at the end of the pole, as in the figure. Jointed feet were attached to the frame which were let down when the engine was at work.

Fig. 393 shows an engine for extinguishing fires, which has come down to us from the times of Hero, who thus describes it:

98

Fig. 394.
(See page 109.)

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Heron or Hero was an Alexandrian mathematician of the 3d Century B. C. He was the inventor of “Hero’s Fountain” in which a jet of water was maintained by condensed air and of a machine acting upon the principle of Barker’s Mill, in which the motion was produced by steam. Fragments of his works on mechanics have been preserved for more than 2000 years.

Lack of space forbids following, as could be done, the growth of the modern steam fire engine from these primitive beginnings to its present high point of excellence and widely extended use. Wherever civilized men are gathered into towns and cities there can be found this admirable mechanism affording protection to both life and property.

The Working Parts,
The Boiler, and
Its facilities for Transportation are the three essential parts of the one mechanism which combined, form the steam fire engine. In brief reference to the last qualification, it may be said that these engines are drawn by hand, by one or more horses, or other animals and are self-propelled by both steam and electric power; again the hose carriage can be drawn by hand, by horses or can be attached to the engine.

The main working parts of the machine can be easily divided into two parts, the engine and the pump.

The boiler in all its details has been designed to meet the requirements peculiar to the fire service and needs a full explanation with illustrations.

The auxiliary appliances found necessary for the operation of the modern steam fire engine are large in number; this is owing to the fact that the machine combines within itself so complete a system for extinguishing fires. The supplies needed for its maintenance and use are also in proportion, as to quantity and variety, to its complex make up.

The boiler, which is generally of the upright semi-water tube type, is combined with the engine by means of a strong iron frame, which carries all the appliances as well as the driver’s seat, and also forms the body of the truck.

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Vertical Section.
Fig. 395.

The pumps may be of the reciprocating or rotary type, and are generally placed in front of the boiler. If of the reciprocating type, two pumps are placed alongside each other, and are operated either by a double slide valve or piston valve engine.

The piston rods connect directly with the plunger rods and are also connected to a crank shaft by means of either connecting rods or yokes, the cranks being set at right angles, so that one pump is always acting, while the other passes the dead center, thus giving a practically steady stream.

The engine exhausts into the stack, which gives the necessary draft. Some engines101 are equipped with a boiler feed pump, others only depend upon an injector, or feed directly from the main pump. The coal box, which also forms a platform for the engineer to stand upon while under way, is placed back of the boiler.

All engines are equipped with two suctions and two discharge openings, so that either side may be connected up. The tool box and driver’s seat are in front of the engine. The frame rests upon springs, to make the machine easy running.

Fig. 396.

The Fox Boiler with which the Metropolitan and other engines are equipped deserves an extended notice. It is shown in vertical section in Fig. 395, the arrows indicating the steam and water circulation. Its design, while simple, embodies some original ideas as to the arrangement of the tube surface method of circulation, etc.; it is a steam generator of the water tube type designed to meet102 the requirements peculiar to the fire service. The steam take-off and sectional view of shell with the tube system removed is shown in Fig. 397.

Plan showing Steam Take-Off.—Fig. 397.

Top View of Empty Shell, showing manifold Beam.—Fig. 398.

The boiler consists primarily of a simple annular shell heavily stay-bolted throughout, and constitutes a water-legged fire-box and steam reservoir; the principal heating surface of the boiler consists of straight water tubes, manifolded in sectional form and housed within the shell, the general scheme providing arrangements to make all connections readily accessible, and permitting the withdrawal from the boiler of any one or all of the several tube sections; the shell, being practically a permanent feature, need seldom be disturbed by reason of subsequent repairs or renewals of the tube systems.

It may be noted that the lower part, or water leg, of the shell is contracted for the purpose of facilitating the rapid generation of steam, and also providing the maximum grate area; at a point somewhat below the water line of the boiler, the inner shell is flanged inward, thereby enlarging the annular space between the inner and outer sheets for the purpose of providing a more copious reservoir.

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The water line being carried in this larger part of the shell, tends to prevent the rapid fluctuation of the water level, and the increased area of its surface at this point is favorable to the disengagement of the steam.

Sectional Unit
for Outer-Tube
System.
Fig. 399.

Sectional Unit for
Inner-Tube System.
Fig. 400.

When held at its normal point, the water line protects the flanged part of the inner shell; but no damage can occur, either from a willful or an accidental drawing down of the water, as the spray deflected through the nipples of the outer tubes is sufficient to protect the flange, although the actual water level is well down in the leg.

The steam in contact with the upper part of the shell is by no means dry, and the heat absorbed at this point is amply sufficient to protect it. To insure a delivery of dry steam to the cylinders, a peculiar “take-off” ring is provided at the highest part of the steam reservoir, the same encircling the inside sheet of the shell. The upper edge of the ring is perforated at a distant point from the throttle, and the steam entering the ring chamber in small streams is held in close contact with the hot shell at a point closely adjacent to the upper line of rivets; the steam by this means is dried during104 its passage to the throttle, and the heat thus absorbed serves as a protection to the rivets just referred to.

The principal heating surface of the boiler is contained in the vertical water tube sections, which comprise and will be referred to, as an inner and an outer tube system.

The outer system, embraces the short manifold sections which completely encircle the fire-box walls. The top end of each section is screwed and suspended from the flanged part of the shell, and the lower end is stayed by direct connection with the leg of the fire-box. The tubes are “staggered” in their manifolds, thereby exposing the greatest possible surface to the fire, and filling out the space due to the difference in the width of the water-leg and steam space of the shell.

The direct application of heat to the tubes causes a natural and active upward current therein, which in turn induces a corresponding downward movement of the water in the leg of the fire-box, and promotes the flow into the feed pipes.

Top View.—Fig. 401.

Bottom View.—Fig. 402.

The inner-tube system comprises those tube sections which extend to the upper limits of the boiler, their number and arrangement being such as to completely fill the interior of the shell above the space required for the combustion of the fuel. The construction of the vertical inner-tube system is simple, and consists of the required number of manifold sections, suitably arranged to conform to the circular space occupied, the flat inner end of each upper manifold being rigidly bolted to a heavy transverse beam, which in turn is supported in suitable pockets secured to the upper part of the shell.

At the top of the boiler, each section has its own connection with the steam space, and it is easy to remove either one of the sections separately without disturbing the others; or the entire inner-tube system can be raised out of the boiler as a whole, after breaking the proper connections, all of which are accessible. The current of steam and water carried over through the top connections of the inner system is generally sufficient to keep the tubes clear of scale; and the point of discharge and disengagement is brought down low, to prevent its mixture with the drier steam contained in the highest part of the shell.

105

When connected to a stationary boiler, as is now the general practice in fire departments, the circulative currents of water reach all parts of the boiler, hence its contents may be kept uniformly at any desirable temperature.

A stationary heater for the fire engine consists of a small boiler, placed at some convenient point near the same when in quarters. It is connected with the engine boiler by means of suitable circulating pipes, the entire arrangement being adapted to supply hot water through pipe connections which separate automatically as the engine leaves the house.

Although the best types of fire engine boilers require but a few minutes’ time to generate a working pressure from cold water, the general adoption of many improvements has made the stationary heater an essential part of a complete equipment.

Experience proves that the life of the boiler is prolonged by being kept constantly in a state of activity, and the elevated temperature of the water insures prompt and efficient work by the steamer at the very time when a few moments’ delay may breed disaster.

106

The pumps fitted and adapted to steam fire engines comprise two separate and distinct double acting piston pumps united in a single body and akin in many details to the duplex pump.

Fig. 403.

Calling in mind the well-known fact, that, in drawing a water supply the only power available to bring the fluid under forcing influence of the pump’s pistons is the limited pressure of the atmosphere, therefore the importance of all details concerned in first inducing an entry of the water will be readily conceded. Easy and unrestricted “suction ways” in direct communication with properly proportioned receiving valves (and these valves suitably arranged in close proximity to the working barrels of the pump), are the conditions that must always remain paramount, and to which all other features must give way, to safely attain the desirable high piston speeds. The value of perfect, simple and direct water ways, the passages, and all which they imply, has been studied in the design of this pumping engine. See Figs. 403-407.

The facilities provided for exposing the interior mechanism107 permits all such parts to be quickly reached for examination, or detached for renewal or repair, and this can be done without dismounting the entire pumps or greatly disturbing their exterior attachments. It will be seen, by reference to the cuts, that all of the valves can be easily and quickly examined, and also replaced, by removing the caps that enclose the chambers; all joints required for this purpose are made between flat surfaces planed true, as shown in Fig. 404; gun metal, or other suitable composition, is used and no part of the pump body is subject to wear, either by friction or corrosion. All valve seats are screwed into place, and either these or the working barrels of the pump may be readily replaced with new ones, in case the same should become worn. All stud bolts, nuts, etc., coming in contact with water, are made of drawn phosphor or Tobin bronze; nipples, piping, etc., are of brass.

Figs. 404, 405, 406 and 407.

108

Suction or hydrant connection may be made at either side of the engine; and, in operation, the central core of the pump body is practically a continuation of the suction hose, and serves to establish a direct communication with the receiving pump valves, arranged on opposite sides of the chamber. This chamber, as shown in the sectional view, Fig. 408, thus becomes the distributing center, from which the incoming water flows to the suction valves. The current from the suction is not required to change its general direction, and but little friction is encountered by the water in its diversion through the pump valves.

The position of the suction or receiving valves, in relation to the water cylinders, may be understood by reference to Fig. 408, which shows the same arranged in a cluster around the open ends of the barrels. The suction valve area is large, and the proportions adopted contribute largely to the smooth running of the pump, under conditions of speed seldom attempted in ordinary practice.

Fig. 408.

The valves in this pump are controlled by improved springs, the tension of which is at all times the same; and which are made of phosphor bronze; the force chambers in opposite ends of the pumps are practically equal, and, owing to the close proximity of the valves, the clearance is reduced to a minimum109 The discharging outlets are elevated above the highest point of the valve chambers, and the communicating passages are designed to prevent conflicting currents, and also to permit the pump to free itself promptly of air. The pistons are of a frictionless type, and in accordance with the usual practice of working double pumps in unison, the cranks controlling the movements of the pistons are placed at 90 degrees.

Fig. 409.

A convenient and effective arrangement of suction strainers is shown in Fig. 409. Perforated cages are introduced into the suction chambers through the inlets on opposite sides of the pump. The ends of these cages are open, and a short sleeve, which is permanently secured within the pump, serves to support and also to establish communication from one cage to the other.

The surface of both cages is, therefore, available as a strainer, and any obstruction entering with the water is carried to the opposite side, to a point where it can be removed, without first detaching the suction hose.

The driving mechanism supplied with the American Pump is shown by Figs. 389 and 394, which are perspective views engraved from photographs. It may be noted that the design is practically compact and well balanced, and embodies many excellent advantages found in no other type of fire engine.

110

The pumps, steam cylinders and driving parts are built as a unit, and have no direct connection with the boiler other than the necessary stays and pipe connections, all of which are readily accessible and visible for inspection at any time.

The steam cylinders used in connection with the pumps are of the ordinary slide valve type. The valve chests are easily opened from either side of the engine for examination, and the valve rods are made from a special composition and can not corrode. The valve motion is simple, and there is nothing connected with the steam ends that may not be quickly understood.

Fig. 410.

Maximum Dimensions of Steam Fire Engines.

111

Appurtenances. In addition to such special fixtures as may be necessary for their proper working, the following articles are a part of each engine:

112

Fig. 411.

The distinguishing feature of this engine will be found in the fact that, in both the cylinder and pump, the rotary type is substituted for the reciprocating or piston principle.

Fig. 412.

The larger sizes of these engines, Fig. 411, are hung on platform truck springs in front and on half-elliptic springs in the rear, and are braced and stayed to withstand violent shocks in the rapid driving over pavements. Although fitted to be drawn by horses only, they can be supplied with rope reel and drag rope.

Fig. 413.

The Silsby steam cylinder consists of two rotary pistons or cams, mounted on steel shafts and working together within an elliptical steam-tight case. Live steam from the boiler enters at the bottom of this case, and in its passage presses apart their long teeth or abutments, causes the two cams to rotate, and exhausts from the top into the tank and feed-water heater; these cams are provided with teeth or cogs, adapted114 to mesh with corresponding recesses in each other, so that a steam tight joint is maintained between them and leakage thereby prevented from passing directly upward into the exhaust.

The sides of these cams have their arcs turned to fit the heads of the case, and are so adjusted that, while being practically steam tight, allowance is made for expansion and contraction. In the ends of the longest teeth of the revolving cams are placed removable packing strips, which are forced outward into contact with the cylinder walls by means of springs. These packing strips may be removed through openings in the sides of the cylinder, and readjusted to take up the wear, which is confined to the ends of these adjustable strips. This can be done without taking the pump or cylinder apart.

Fig. 414.

Fig. 415.

The construction of the pump is similar to115 that of the cylinder; in this there are three long teeth in each cam instead of two. One shaft of the pump is coupled to the corresponding shaft of the cylinder, there being outside gears on both cylinder and pump to compel a uniform motion of the cams and to equalize the pressure. This construction secures a transmission of power at once direct and positive in Fig. 412.

The stuffing-boxes, used on both cylinder and pump, are self-adjusting, reduce friction and insure tightness. Valves are entirely absent from the pump and cylinder. The water ways being large, anything liable to enter the suction will pass through the pump without injury or interruption; the pump requires no priming, but when started will immediately without the aid of a check valve lift water vertically any required distance up to 29 feet.

The construction of the boiler ordinarily supplied with this engine is shown in Figs. 414-415. In the fire-box hangs a series of circulating water tubes arranged in concentric circles and securely screwed into the crown sheet. These drop tubes are closed at their lower ends by means of wrought-iron plugs welded in, and within each of them is placed a much smaller and thinner tube, which latter is open at both ends. The cooler water in the boiler descends through the inner tube and is thus brought directly into the hottest part of the furnace, whence, after being for the most part converted into steam, it ascends through the annular spaces between these inner and outer tubes.

The gases of combustion pass from the fire box to the stack through smoke flues, the lower ends of which are expanded into the crown sheet, and the upper ends into the top head of the boiler.

116

Fig. 416.

117

TABLE OF EFFECTIVE FIRE STREAMS.

USING 100 FEET OF 2¹⁄₂-INCH ORDINARY BEST QUALITY RUBBER-LINED HOSE BETWEEN NOZZLE AND HYDRANT, OR PUMP.

118

The Clapp & Jones piston engine in design has features peculiar to itself; Fig. 416 represents one of six sizes, adapted particularly to city service.

Fig. 417.

The illustrations, Figs. 417 and 418, show the vertical pump as built for the larger engines: namely, the sizes known as Extra First, First, Second, Third and Fourth. The complete engine corresponding to the detailed views is shown by Fig. 416 on the preceding page.

The principal details are very clear in this engraving. The steam and water ends, together with the crank and reciprocating mechanism, are compactly arranged and the complete structure which comprises these parts is rigidly self-contained. The steam cylinders and valve chest are cast in a single piece and while this part is firmly secured to the boiler, all steam and exhaust connections are entirely independent of these fastenings.

The Clapp boiler is represented in Fig. 419. Reference to the annexed illustration makes clear the special features of this boiler, which consist chiefly of a series of spiral water-tube coils arranged[119] within the fire-box. The coils are of copper and are produced by the seamless drawn process. Each coil is connected separately to the boiler, and the spiral form of these tubes permits freedom for expansion and contraction without strain on the terminal joints. The connections and the ends of the tubes are made by means of threaded nipples, jam nuts and corrugated copper washers, and the joints thus made insure tightness, yet admit of ready disconnection at any time.

Fig. 418.

The lower ends of the coil tubes are directly joined to the hollow fire-box walls and the upper terminals are arranged to discharge the circulated water over the crown sheet. This upward movement of the water within the spiral coils is caused120 by the application of heat to the outer surfaces of the tubes, and the circulation thus set up induces a corresponding downward action in the leg of the boiler. The circulation, therefore, continues without interruption so long as fire is maintained on the grate. In operating this boiler the water should be carried a few inches above the level of the crown sheet, but owing to the protection afforded by the constant distribution of water over the crown sheet, the limit of safety is not reached until the water is nearly out of the fire-box leg.

Fig. 419.

An improvement in the design of this boiler is the water-circulating deflector, which was devised to occupy the central space within the coil tubes. This deflector comprises an additional sectional[ 121] unit, and its action coincides with the functions served by the coil tubes. The prime object of this device is to break up and direct the gases of combustion in a manner that adds to the heat-absorbing qualities of the coil tubes. See Figs. 420, 421.

Fig. 420.

Extending from the crown sheet to the top head are the smoke flues, which are securely expanded at both ends, and through which the gases of combustion pass from the fire box to the stack.

The Clapp & Jones Village Engine. By the illustrations, Figs. 422, 423, 424, etc., it will be noted that the cylinders and pumps are disposed horizontally and are fitted in a self-contained manner between bars, which also serve as the main frame of the engine.

The steam cylinders are 8 inches diameter; the pumps 4³⁄₈ inches, and the stroke common to both is 7 inches. These sizes are properly proportioned for effective work and the boiler power provided is ample to drive the pumping mechanism to its rated capacity of 400 gallons per minute.

Fig. 421.

The pumps are fitted with gates permitting two lines of hose to be worked either independently or at the same time without interference. The machine is mounted on half-elliptic springs, front and rear, and the weight of the boiler and pumps is distributed equally over both axles. The front pair of wheels turn completely under the goose necks, and the engine can therefore be turned on either hind wheel as a pivot. The arch of the main frames under which the wheels pass in turning is immediately forward of the boiler, and the advantage to be noted in this connection is the reduction in the over-all length of the entire machine. The front122 axle is equipped with a rope reel, and the pole is arranged for either hand or horse draft. The wheels are fitted with brakes, which are operated from the rear footboard. The engine weighs about 4,400 pounds. A detail description of the pump and valve gear follows.

Fig. 422.

The valve gear of the Clapp & Jones village engine is simple yet controls the moving mechanism of the two pumps working in unison. Each pump is driven directly by its own steam cylinder, and the steam valves are actuated by the positive movement of the opposite piston rod. The principle is substantially the same as practiced in the “Duplex” pump construction, and may be readily understood by reference to the detailed views which are given of these parts in other portions of this work.

Fig. 423.

123

The steam cylinders and pump are self-contained, and aside from the distinctive difference in the reciprocating gear the design of the steam and water ends does not differ from the vertical engines of the Clapp & Jones type.

On these engines intended for use in cold climates a “thaw-pipe” is attached, at the engineer’s side, inside the frame, and is used in extremely cold weather to prevent the feed-pump, as well as the main pump and connecting pipes, from freezing. It is operated by means of a small globe valve. If it is desired to warm the main pump, the two-way cock used in feeding the boiler should be turned as when feeding directly from the main pump, when steam will have access both to the main pump and the feed-pump; but care must be observed not to heat the main pump too warm. When the two-way cock is closed, and also when it is open as when feeding from the tank, the steam goes only to the feed-pump.

After using it to warm the main pump, the two-way cock, should be closed; otherwise, if the check-valve should happen to stick fast, the water would pass out of the boiler through the main pump.

Fig. 424.

Always keep the globe valve closed when not in use. It will be observed that the vacuum chamber upon the suction pipe is located within the air chamber upon the discharge passage.

The valves of this pump are formed by heavy rubber rings which surround the pump barrel, as shown in Fig. 423, therefore there can be no hammering of these valves when the pump is at work.

The rubber rings have slots cut into them at each side of each valve so that each valve can open and close without stretching the rubber bands. The steam valve is of the well-known rocker type. The plungers have no packing excepting water.

124

Fig. 425.—See page 122.

The sizes of nozzles named below will give the most satisfactory results, those in italics being the ones best adapted for fire duty. Also see page 93 for standard sizes of steam fire engines and page 117 for table of effective Fire Streams.

1, Extra first size engine.—1,100 to 1,150 gallons capacity. Through short lines of hose: One 1¹⁄₂-inch smooth-bore nozzle, for one stream; one 1³⁄₄-inch ring nozzle, or one 2-inch ring: nozzle; 1⁵⁄₁₆-inch ring nozzles for two streams. With 1,000 feet of hose, one 1⁵⁄₁₆-inch ring nozzle.

2, First size engine.—900 to 1,000 gallons capacity. Through short lines of hose: One 1³⁄₈-inch smooth-bore nozzle, for one stream; one 1¹⁄₂-inch ring nozzle, or one 1⁵⁄₈-inch ring nozzle; 1¹⁄₄-inch ring nozzles for two streams. With 1,000 feet of hose, one 1¹⁄₄-inch ring nozzle.

3, Second size engine.—700 to 800 gallons capacity. Through short lines of hose: One 1¹⁄₄-inch smooth-bore nozzle, for one stream; one 1³⁄₈-inch ring nozzle, or one 1¹⁄₂-inch ring nozzle; 1¹⁄₈-inch ring nozzles for two streams. With 1,000 feet of hose, one 1¹⁄₈-inch ring nozzle.

4, Third size engine.—600 to 650 gallons capacity. Through, short lines of hose: One 1¹⁄₈-inch smooth-bore nozzle, for one stream; one 1¹⁄₄-inch ring nozzle, or one 1³⁄₈-inch ring nozzle; 1-inch ring nozzles for two streams. With 1,000 feet of hose, one 1-inch ring nozzle.

5, Fourth size engine.—500 to 550 gallons capacity. Through short lines of hose: One 1¹⁄₁₆-inch smooth-bore nozzle, for one stream; one 1¹⁄₈-inch ring nozzle, or one 1¹⁄₄-inch ring nozzle; ⁷⁄₈-inch ring nozzles for two streams. With 1,000 feet of hose, one 1-inch ring nozzle.

6, Fifth and sixth size engines.—300 to 450 gallons capacity. Through short lines of hose: One 1-inch smooth-bore nozzle, for one stream; one 1-inch ring nozzle, or one 1¹⁄₈-inch ring nozzle, ⁷⁄₈-inch ring nozzles for two streams. With 1,000 feet of hose, one ⁷⁄₈-inch ring nozzle.

126

The Ahrens steam fire engine is not presented as a whole, but Figs. 426-428 show parts of this interesting and widely known apparatus.

Fig. 426.

The boiler, Fig. 426, is radically different from others, and the special features making it so popular in the past are the127 absence of a crown sheet and smoke flues, coupled with the advantageous manner in which the water-tube coil sections can be withdrawn from the containing shell of the boiler. The peculiar arrangement of the tubes compels a forced circulation of the water, and for which purpose an independent steam pump is provided. Water drawn from the fire-box leg is forced through the water tubes, and this relation between the circulating pump and the other elements of the boiler will be more readily understood by reference to the illustrations, where Fig. 426 is a sectional, 427 a top, and 428 a bottom view.

Fig. 427.

Fig. 428.

128

Fig. 429.—See page 141.

The fire engine is essentially an apparatus adapted to emergencies, and owing to the intermittent nature of the duty performed, it is quite likely, unless the proper precautions are observed, that its several parts, more especially its interior mechanism, will suffer more deterioration while standing idle than from actual service.

130

Fig. 430.—See page 141.

131

132

Fig. 431.—See page 138.

133

Fig. 432.—See page 138.

134

Fig. 433.—See page 139.

135

136

137

The number of appliances and special devices used on and about a steam fire engine is not large, as it is the aim of both designers and builders to simplify the machine as much as possible without diminishing its efficiency.

Fig. 434 is an appliance known as the Siamese connection. It is used for stand pipes attached to the outside of buildings, etc., and also as a detail of the fire pump. Its use is to lead off two lines of hose.

The valve shown in the figure, closes automatically in case of stoppage of one of the engines or the bursting of the hose.

Figs. 434, 435.

Fig. 435 exhibits an approved form of strainer for the bottom of the suction pipe.

The American steam fire engine pump is shown in Figs. 431 and 432.

Fig. 431 being the front view, one side of it shown in section, exposing the interior parts for explanation, and Fig. 432, representing the side elevation, also in section.

The pumps, which are double acting, are united in a gun-metal casting, which forms a single body for both, and permits them to be placed much closer as to centers than could otherwise be done. This method provides an ample suction-chamber which is common to both.

In cross section the pump somewhat resembles a box girder. This peculiarity of the pump’s combined form furnishes a rigid139 base for the entire structure, simplifies the driving mechanism and enables it to endure extraordinary strains without vibration.

It will be seen by reference to the cuts that any of the valves can be easily and quickly examined, and, if necessary, replaced, by simply removing the caps and heads.

The pump barrels are provided with removable linings, which can readily be replaced with new ones in case the same should become worn after years of service. These, as well as the valve seats, are made of gun metal, no cast iron or other material subject to corrosion by water being used in any part of the pumps.

Both the suction and discharge valves are supplied with improved valve springs, the tension of which is, at all times, the same; and being made of phosphor bronze, the springs retain their elasticity and will not corrode.

The steam cylinders used in connection with this pump are of the ordinary slide-valve type, with which most mechanics are familiar, and are thus easily repaired when necessary. The cylinders and pumps are detached from the boiler, and are separated therefrom sufficiently to allow every facility for getting at each and every part. All connections, both steam and water, are made outside of the boiler.

The La France steam fire engine pump is shown in outline in Fig. 433, which consists of a double plain slide-valve engine, operating a double pump.

The steam piston rod of each side connects with its pump rod, by means of square bars, two of which are on each side of the crank shaft. The crank is operated by the cross-head through a connecting rod; the arrangement of these parts can be seen in Fig. 433. The cross-head guide is entirely done away with, as the stiffness of the connection between the two piston rods takes the thrust of the connecting rod.

The pump barrel is enclosed by an outer casing. The space between barrel and casing is always kept filled with water which is supplied through the suction pipe.

140

Fig. 436.

When the pump barrel is being filled with water the suction valves are lifted from their seats, which allows the water to141 pass into the space between the valve-seat plates and thence into the pump barrel.

When the pump barrel is being emptied the suction valves are closed while the discharge valves are open, which allows the water to pass into a triangular shaped space between the front plate and valve-seat plates thence upward to the discharge pipe.

The suction and discharge valve of this pump being all grouped together, it is only necessary to remove the plates which can be seen, Fig. 433, bolted to the front of the pumps and form part of the outer casing; these plates are in front of the pump and may be quickly unscrewed by a T wrench.

The Amoskeag steam fire engine is shown in the views (Figs. 429 and 430 on pages 128 and 130). This world widely known machine is made by the Manchester Locomotive Works at Manchester, New Hampshire, U. S. A.

The former cut represents the extra first, first, second, third and fourth size double steam fire engine of this make. They have “crane-neck” frames and are arranged for horse draft and are mounted upon Endicott’s patent platform springs. The effect of this improvement is that the draft strain is transmitted directly from the horses to the axles, the springs bearing no part of this draft strain.

Fig. 430 shows the “fifth” size, also with “crane-necked” frame and made for either horse or hand draft.

The boiler used is upright and tubular in style, is made of the best quality of steel plate, with seamless copper tubes, thoroughly riveted and stayed; it is simple in its construction, and for strength, durability, accessibility for repairs, and its capacity for generating steam, has passed a most critical test. For engines of the second size and larger, the boilers expand downwards at the crown sheet of the fire-box, thus increasing the grate surface and consequently the steaming capacity of the boiler.

The connections with the steam cylinders are simple, direct and of good capacity, peculiarly accessible for repairs, and have the great advantage of being entirely unexposed to the air.

142

The steam cylinders of the single engines are made in one casting; they are secured to the boiler framing, and covered with a lagging of wood, with a metallic jacket on the outside. The pump for the double engines is made entirely of composition, and its main shell is also in one casting. It is vertical double acting; its valves are vertical in their action; the water-ways are free and direct, and the valves accessible, so that examination or renewal of these parts may be quickly made. The pump is arranged for receiving suction hose on either side, and has outlets also on either side for receiving the leading hose.

Self-propelled steam fire engines are well adapted for city service. In Fig. 436 is shown a double extra, first size self-propelling engine of the Amoskeag pattern. The road driving power is applied from one end of the main crank shaft, through an equalizing compound and two endless chains running over sprocket-wheels on each of the main rear wheels, permitting these rear wheels to be driven at varying speeds as when turning corners.

The driving power is made reversible, so that the engine may be driven either forward or backward on the road at will.

The steering of the engine is effected by means of a steering hand wheel at the front, adjusting the front axle through a system of bevel and worm gearing, so arranged that the constant exertion of the steersman is not required to keep the wheels in line on the road. By the removal of a key the driving power may be disconnected from the road driving gearing, when it is desired to work the pumps when the engine is standing still.

143

144

Fig. 437. (See page 146.)

There are certain well-known difficulties and contingencies in installing and operating mine pumps: 1, The location of the mine is usually remote from supplies and any renewals or repairs which may be needed, are liable to be attended with excessive costs and delays; 2, The nature of the water in the mines is so highly acidulous that corrosion takes place in an incredibly small space of time. The action of sulphuric (diluted) acid which is found sometimes as high as two parts out of a hundred begins at once and continues until the iron or steel is destroyed; 3, The dust, grit, mud, etc., becomes mixed with the oil used to lubricate the pump; these ingredients find their way into the stuffing-boxes and cut the plungers.

Hence, ample and unusual precautions are made to overcome the foregoing conditions. Extreme care has to be used in securing all movable parts of the machine and the connecting pipes. The plungers are generally outside packed and handholes are arranged to permit free access to the water valves.

Fig. 438.—See page 148.

When pumps used in mining service assume large proportions, they are almost invariably described as pumping engines; there is no real difference between the two except the proportions. The same combination of engine and pump in the smaller sizes used for boiler feeding, etc., are called steam pumps.

146

The Cataract steam pump, Fig. 437, is largely used in mining operations. Many years service has proved its peculiar and curious merits. Large columns of water may be raised to great elevation or forced against heavy pressures without shock or jar of any kind and with safety to the machinery and connections; abrupt and violent action of the water is also avoided. The Cataract, it may be explained, is a regulator invented by Smeaton for single-acting steam engines. John Smeaton, the inventor, was an English civil engineer born in 1724 and died in 1792. The device derives its name from its similarity to the optical disease—a cataract—as it is a supplementary or sliding cylinder with its piston attached very curiously to the main valve stem of the engine.

This cylinder—called the Cataract cylinder—is filled with oil which flows back and forth through a port connecting its two ends. This port is controlled by a valve which increases and diminishes the flow of the oil through the port. By means of the Cataract, the movements of the main steam valve are automatically graduated and controlled, so the speed of the piston is reduced as it nears the end of its stroke, allowing the valves to seat themselves gently and quietly, and the moving column of water to come to a gradual and easy rest.

The claims of this construction of pumps have been thus summarized—

1st. The speed of the piston is automatically slowed down at the end of its stroke, giving time for the column of water to come gradually to rest, and for the valves to seat gently and quietly, avoiding all concussion, jar, or the slightest tremor.

2d. The speed of the engine can be adjusted and automatically maintained as desired under any pressure. Should it be working under full head of steam and against a heavy pressure, and the pressure be instantly removed the speed would continue unchanged.

3d. The piston works to the end of its stroke under all pressures, avoiding the waste of steam incident to the piston falling short of its stroke.

147

It will be understood that there is only a slight waste of oil caused by the use of this apparatus—all the waste that there is, being the small amount leaking through the stuffing boxes.

The term “Isochronal,” pump meaning equal spaces in equal times has been applied to both these pumps and their valve gear.

The sizes, capacities, etc., of the pump described on the opposite page are given in the following

Table.

The above table is based on a steam pressure of 45 to 50 pounds per square inch of steam piston, and the vertical height is from lower end of suction pipe to discharge.

Fig. 438 is designed to show a pump largely used by miners in prospecting. It is double levered so that four men or more can operate it, two to each lever. The plunger and valves are so designed that they will lift muddy or gritty water without injury to these parts.

An electric mining pump is shown on page 276, part one. This is a portable pump mounted on a car running on rails and is designed for the work appertaining to a mine in steady operation.

On page 340, part one, is illustrated a powerful pump with four outside packed plungers designed for mining purposes.

These special mining pumps are used to drain water from the shaft bottom, so that work in deepening or repairing may be carried on. As shown in the illustration they are made to be suspended by a chain or bail attached to eye-bolts in the upper cylinder head at points of support which will enable the pump to hang vertically and be raised and lowered at will.

Fig. 439.

The bail is so constructed that while the pump is suspended the cylinder head can, if necessary on the smaller sizes, be removed and the steam piston examined and adjusted. As the shaft gets deeper the chain may be lengthened out and an extra joint placed on the end of the delivery pipe.

The sinking pump is subjected to the hardest usage of any, hence any steam pump that is to be used in sinking a mine shaft must be strong, certain in operation, capable of handling gritty water and require little attention.

Fig. 438 exhibits a hand-power mining pump, designed especially for prospecting, etc., and made by the Edson Manufacturing Co., Boston, Mass. It is listed for three sizes:

The outfit which usually goes with this diaphragm lift and force pump includes special suction and conducting hose, brass149 coupling and strainer; these pumps will raise and force water containing gravel, sand, dirt or tailings without choking.

The Deane single vertical sinking pump is shown in Fig. 439; a table of dimensions and capacities of this pump is also given below.

The pump illustrated is double acting and of the differential plunger type; the water end is in three parts and consists of a water cylinder, a lower plunger and an upper plunger. The water passes directly up and through the plungers, both of which are hollow. These plungers are outside packed. The water valves are reached by hand holes provided for that purpose. Split pins are used in the ends of the bolts to prevent the nuts from working off.

These pumps are designed to stand a working pressure of 150 lbs. to the square inch. They have the regular Deane valve motion and will work under water.

Table.

This table refers to Fig. 439.

150

Fig. 440.

151

Fig. 441.

152

The Cameron vertical plunger sinking pump is shown in Figs. 440 and 441.

Fig. 442.

Fig. 443.

This is one of the most successful mine sinking pumps designed; there are no parts exposed to rust, and instances have occurred when this pump has started off and cleared a shaft of water when the pump itself had been buried for weeks under a mass of fallen rock and debris.

This pump has no outside valve gear, arms or levers; all movable parts are inside and enclosed, to prevent collision with the walls of the mine shaft nor is it likely to receive injury from blast explosions. Being fitted with special exhaust cut-off, it will continue to run as fast as steam will drive it (with an irregular or intermittent supply of water, or when the water fails entirely,) not only without danger of the piston striking the heads, but without injury to the valves. It is designed and intended to handle gritty water.

Telescopic pipe joint shown in Figs. 442 and 443, supplies a convenient means for lifting and lowering a sinking pump, and is usually made in lengths of sixteen feet. This enables the operator to drop the pump that distance without disturbing the rest of the pipe; by its use irregular lengths of pipe can be added, whereas, otherwise when the pump is lowered the pipe would have to be cut of equal length.

The inside pipe is brass tubing which freely slips through the packing and is non-corrosive.

Fig. 441 exhibits the sinking pump in practical operation; it is the same as that shown on the previous page.

153

The “Scranton” pattern of a mining pump is illustrated by the cuts shown below (Figs. 444 and 445).

Fig. 444.

Fig. 445.

The plungers of this machine work through middle, exterior stuffing-boxes, into four separate and distinct water cylinders. The valve areas and water ways are unusually large in proportion to the displacement of the plunger, so that the velocity and consequent destructive action of the water currents is decreased in passing through the pump.

154

These pumps are designed to withstand safely a working pressure of 250 pounds to the square inch, and all their attachments are especially strengthened with a view to meeting the rough usage and hard work to which they are liable to be subjected in mining operations.

Fig. 446.

Table.

155

The Worthington Pressure Pump. This pump, presented in Fig. 446, is specially designed for use in connection with hydraulic lifts and cranes, cotton presses, testing machines, hydraulic riveting and punching machines and hydraulic presses of all kinds. Also, for oil-pipe lines, mining purposes and services requiring the delivery of liquids under heavy pressures.

There are four, single-acting, outside-packed plungers, which work through the ends of the water cylinders, the latter having central partitions. The arrangement of compound steam cylinders shown in Fig. 445, or a triple expansion arrangement, can be applied to these pumps where a saving of fuel is desired. The water valves are easily accessible and are contained in small independent chambers, capable of resisting very heavy pressure.

These are made both horizontal and vertical; the prime consideration being in all cases the amount of floor space the pump will require. This is especially true in reference to small steam vessels, pleasure craft, etc.

Owing to the unusual corrosion, caused by galvanic action, salt and various impurities, marine pumps are built of iron with brass linings, but frequently with the entire water ends of bronze.

The arrangement of the water valves in the most approved forms of vertical pumps is such that the pistons are always submerged, and the water valves sealed, thereby securing immediate lift of water through the suction pipe, and steady, quiet operation of the pump; many horizontal pumps of the ordinary duplex design are also used on shipboard.

The ship’s pump is common to all vessels and used to keep the “hold” free from water. It is usually worked by hand but it is the law in certain countries that the “ship’s pump,” aside from steam vessels—shall be driven by windmill power; it is said to be an odd sight to see the practical working of these at sea.

156

Fig. 447.

157

The illustration on page 156 shows a marine vertical pump of the Davidson pattern, designed to work against a pressure of 250 pounds per square inch. The table given herewith will show the sizes and principal details of these pumps.

Table.

The capacity for boiler feeding in the table is based upon sixty single strokes for each pump per minute.

The suction and discharge openings, as will be seen in the figure, are on both sides. The water piston is packed for hot and cold water and special valves are furnished as may be necessary.

The Worthington wrecking pump, Fig. 448, was constructed many years ago, for wrecking, drainage, or irrigating purposes, and has proved itself to be remarkably well adapted to such service. It is used generally by the Wrecking Companies on the Atlantic and Pacific coasts and the lakes, and is constructed with special reference to reliability, portability and general efficiency.

It is also well adapted for other services requiring the delivery of large quantities of water within the range of lift by158 suction. It has no forcing power, the water being delivered over the top of the pump into the curb surrounding it. It is single-acting, although the discharge is practically constant, by reason of the quick return of the piston to the bottom of the cylinder, during which inactive stroke the water continues to flow by the momentum already acquired, thus the effect of a double-acting pump is almost produced.

Fig. 448.

159

The ordinary slide valve is employed, moved by an arm striking against tappets on the valve rod. No auxiliary valves are used in connection with it. The water valves are of rubber, the lower ones being upon a permanent plate at the bottom of the pump. The plunger also is covered with valves. These last open for the passage of water when the piston descends.

On account of its short stroke and large diameter, this pump is extremely efficient, running on comparatively low pressure of steam, and with a very small percentage of loss from friction or leakage. It is also simple and durable, with few parts.

The stated capacities of the pumps given in the table can be exceeded in cases of emergency.

Table.

This machine is constructed to meet the requirements of steamship builders and is recognized and adopted by marine engineers of this and of other countries as the standard design for this service and for oil tank steamer work.

It will be observed, see Fig. 449, that its proportions are such as to secure the advantages of large pumping capacity with unusual compactness and moderate weight.

This pump is of the packed piston type, and has the valves so arranged that the water pistons are always submerged, thus making it particularly well adapted for long and difficult suction lifts such as are met with in steamers carrying petroleum in bulk, and in steamers having extensive systems of water ballast tanks.

160

The demands for water ballast service are generally met by the following two sizes, as shown in the table below.

Fig. 449.

Table.

161

The purposes for which pumps are used on shipboard, aside from the air and circulating pumps for condensers, are:

(1.) Feeding the boiler.

(2.) Emptying the tanks and pumping out bilge.

(3.) Supplying water for washing down decks, extinguishing fires, filling evaporators and sanitary service.

A special pump for each separate purpose is not always supplied, but one pump may have the necessary pipe connections to serve alternately various duties.

Feeding the boilers is so important an operation that a supplemental special pump is always required. To make absolutely sure of an ample supply of feed water one of the other pumps is made strong enough to serve the same purpose, or sometimes an injector is fitted as an auxiliary feeding mechanism.

A bilge pump has special fittings, for the reason that it handles very dirty water, undesirable to be transmitted through any other pipe system. In small ships, however, one pump, the so-called “donkey,” often serves for nearly all other purposes, including auxiliary boiler feeding.

A special form of pump in use on Western river steamers is the so-called “doctor,” an independent pump with a walking beam, by which one steam cylinder drives a system of pumps for feed, fire and bilge pumping purposes (Fig. 450).

The feed pump should be of simple construction, great strength and ample capacity, to secure great regularity and reliability of service under the severe conditions of high pressure.

The main parts of auxiliary feed pumps are often duplicated. This is a desirable point, as one set of spare parts in piston, rings, valves, etc., is suitable for both pumps.

The main feed pump is, even in the independent type, often placed in the engine room, while the auxiliary pump, or the injector, is in the fire room. The feed pumps draw usually from the hot well, feed heater and feed tanks and discharge through main feed pipe into the boiler.

162

This “doctor” pump is a substantial piece of mechanism. The bases of columns and pump chamber flanges are accurately planed, the cylinder has spring piston packing and the plain slide valve is made of gun metal.

The hot water pumps, 3¹⁄₂″ diam. × 10″ stroke, have chambers bored and are fitted with a copper and tin composition for valves and scats; the latter are driven into their places and riveted over underneath.

Fig. 450.

These gauges are apt to get out of order for various reasons namely, there is no theoretical method of determining the motion of the pointer due to a given pressure; this is done by tests in which known pressures are employed, and accordingly the divisions on the graduated scale are usually unequal, hence these instruments are tested by attaching them either to a mercury column, or to a dead weight safety valve having for its seat an exact square inch surrounded by a knife edge, or a piston of standard area loaded with weights. This sharp edge is covered by a fibre washer of leather for moderate pressures, say 150 lbs. per square inch, or vulcanized fibre or its equivalent for higher pressures.

Fig. 451.

Fig. 451 represents a pump that can be used for pressures up to 10,000 lbs. per square inch. The Hand-Lever Pump shown at the right in cut is used for filling the Pressure Pump cylinder and connections with oil or glycerine, and may also serve for testing gauges of low pressures up to 15 or 20 lbs. The suction pipe a is connected with the reservoir containing the oil or glycerine, which after being used is discharged by valve d and returned into the reservoir by pipe c.

In filling the pump the cylinder spindle has to be screwed all the way out, and the valves b and d closed before it is put under pressure.

164

Fig. 452.

The handling of semi-liquids, commercially known as thick stuff, has always been considered more or less of a serious problem, and many designs of mechanism in the form of pumps have been invented for that purpose.

For pumping tar the improved forms of rotary pumps have recently come largely into use. These will be described later under their proper heads. Fig. 212, page 232, Part one, represents a very satisfactory design of plunger pump for handling the heavy stuff alluded to.

The Deane single sugar-house pump is shown in Fig. 452. These are largely used for pumping molasses, syrup, cane-juice, melter-pan products, etc., and are fitted with linings, valves, etc., to best suit the condition of the fluid to be pumped.

The valves are very large and the motion of the pumps is somewhat slower than for water. By removing one set of bolts all the valves are uncovered.

These products of the sugar-house when of a high temperature can be pumped nearly as fast as water; the following list gives the approved proportions of these pumps.

Table.

166

The Single Magma Pump. The term magma includes any crude mixture, especially of organic matters in the form of a thin paste, it also means “a confection,” hence, the name given to the pump illustrated in Figs. 453 and 454 is very appropriately applied to a sugar-house apparatus. It is designed for pumping various thick heavy mixtures and semi-liquids and for moving massecuite, second and third sugar.

Fig. 453.

Fig. 454.

The construction in Fig. 453 is such as to insure strength and certainty of operation; there are no intricate small parts, and the interior is readily accessible. These pumps are made with brass-lined cylinders, or cylinders and fittings entirely of composition when needed to overcome the difficulties appertaining to pumping acidulous and corrosive liquid substances.

167

The single fly-wheel magma pump as shown in Fig. 454 represents the highest type of machine for this class of work. The steam end is of the plain slide valve pattern. It is fitted with a heavy fly-wheel, perfectly balanced. The admission of steam is regulated by a throttling governor of approved design. The fly-wheel and governor insure a uniform speed of the pump under variations of load—hence the fly-wheel pump does not require adjustment of throttle for every variation in water pressure, as is necessary with direct acting pumps.

The following table applies to the two styles of the magma pumps—with and without the fly-wheel, as the pump ends are the same in both. Attention is called to the number of strokes per minute (thirty) shown in the table as compared with the number of strokes (100 and 125) called for in the previous table. This is caused by the different viscosity of the stuff to be handled by these machines.

Table.

The definition of the word circulation conveys the best idea of this mechanism—“The act of moving in a circle, or in a course which brings the moving body to the place where its motion began,” hence, a circulating pump is one which causes the water to flow through a series of pipes or conduits, as for example, the water in a steam boiler as in the Ahrens Fire Engine, see page 126, Fig. 426, or in marine boilers, or forces cooling water through a surface condenser.

A centrifugal pump driven by an independent engine, see page 219, Fig. 497, is generally used for the latter purpose.

Fig. 454A.

The annexed engraving, Fig. 454A, represents a circulating pump attached to a salt water evaporator and distiller for recovering fresh water at sea. The pump at the lower right-hand corner of the engraving takes salt water through the suction at the bottom and passes it upward through the condenser and overboard through the circulation discharge. Any steam pump having a sufficient capacity may be used as a circulating pump.

The Bliss-Heath Atmospheric Pumping Engine represented by Fig. 455 is novel in its construction, consisting of a low-pressure, upright, tubular steam boiler, having a safety valve loaded to carry 1¹⁄₂ lbs. steam pressure. The large cover lifts under 2 lbs. pressure, hence explosions cannot occur.

Fig. 455.

The motor is a simple atmospheric engine operating a plunger pump and a single acting air pump.

The operation of this motor is almost noiseless.

The motive power is the normal pressure of the atmosphere (14.7 lbs. to the square inch), utilized by the formation of a vacuum in the power cylinder.

170

The air is expelled from the cylinder by admitting steam without appreciable pressure, i.e., to balance that of the atmosphere, after which the steam exhausts into the surface condenser, in which a constant vacuum is maintained. Steam is then admitted automatically into the power cylinder, breaking the vacuum and imparting to the piston the required impetus. This principle is identical with that of the ordinary condensing steam engine, with the exception of the very low steam pressure in this connection.

Fig. 456.

This engine can be operated satisfactorily in combination with an ordinary house-heating boiler (low pressure), hence the expense of running it is very low during the steam-heating171 season. During the summer months the boiler connected with this engine can be used advantageously.

The bearings are self-oiling, and the cylinder condensation furnishes ample protection for the inside of the engine cylinder. There are no leather packings to burn out, and this is remarkably free from the objections to the older types of caloric engines.

These pumps when required will force a proportionate quantity of water to a greater height than fifty feet, upon which the following table is based:

Table of Approximate Dimensions and Capacities.

In pumping ammonia it is of the greatest importance that this mechanism be simple and compact owing to the peculiar properties—oftentimes dangerous—inherent to ammonia.

The plain slide valve with crank, shaft and fly-wheel probably is less liable to give trouble than many of the other styles of pumps, and a full stroke is always assured.

The pump here presented (Fig. 456) occupies little floor space and is easily accessible; the bucket plunger is used and also a slotted yoke in place of a connecting rod.

The column is in two parts bolted together. In case of accident to either part duplicates may be quickly substituted.

The pump shown herewith lifts the water by propeller screws or “runners,” each consisting of two half-circular inclined blades fastened to a shaft at intervals of 3 to 5 feet, and of slightly less diameter than the casing, so as to revolve freely within it.

Experiments have demonstrated that more water can be raised with a given speed by putting the runners close together near the bottom of the pump.

A bearing for the shaft is placed immediately underneath each of the runners, and held in position by a set of spring “guides” attached lengthwise to the well-casing. These guides interrupt the whirling motion of the water as it is thrown upward by the runners, and turns it back in the opposite direction, thereby delivering it into the revolving runners in a direction opposite their motion. By this method the whirling motion of the water is utilized and the capacity of the pump largely increased without a proportional increase of power to run it.

With this pump, water may be raised from several hundred feet below the surface by extending the shaft and runners down the well-casing to the desired depth; it being always necessary to submerge the lower runner. As the shaft rotates the lower runner lifts the water up to the runner above it, and so on to the next, until the water is delivered at or above the ground if desired; the distance depending upon the size and pitch of the runner, the number of runners, and the speed at which they are driven.

Speed is not increased for additional depth, because more runners are added, and this compounding of the runners increases the efficiency of the pump.

A ball bearing is placed over the stuffing-box to carry the entire weight of all the movable parts of the pump, and also the column of water. In deep wells cone roller bearings are used in place of the ball bearings.

173

The pumps are made to fit all sizes of wells and of any desired capacity. Runners of various pitches are made for the different sizes in order to suit the supply of water or the power available. If, after testing, the supply of water in the well is found to be limited, the runners are changed to raise the amount of water due to a given horse-power, then runners can be furnished with a pitch suited to lifting that particular amount of water.

Fig. 457.

For example, if one runner at a given speed, gives 10 pounds pressure per square inch, then two runners would give 20174 pounds; three, 30 pounds, and so on. For this reason water may be elevated higher above the discharge with this pump than with a centrifugal, for it would require a higher rate of speed to lift a given amount of water 20 feet with one runner, than to lift the same amount 5 feet. Hence the advantage of compounding the runners as the lift is increased. The compounding of runners is one of the main features of success and efficiency of this pump.

Fig. 458.

Where the water is beyond the suction limit this pump can be used to raise the water to the surface, discharging into the suction of the force pump. In this manner, whatever surplus of power the propeller pump might have in raising the water to the surface, would be utilized in helping the water through the force pump.

The speed of rotary pumps is generally high, ranging from 800 revolutions per minute for the small sizes to 250 revolutions for the larger sizes. In a number of experiments made upon this form of pump the highest efficiency was obtained with pressures ranging from 30 to 50 pounds per square inch, and speeds ranging from 475 to 575 revolutions per minute. The average efficiency of the rotary pump is from 48 to 52 per cent.

The engraving herewith, Fig. 458, exhibits the general construction of the Quimby screw pump. The four screws that act as pistons in propelling the water are mounted in pairs on parallel shafts, and are so arranged that in each pair the thread of one screw projects to the bottom of the space between the threads of the opposite screws. The screw threads have flat faces and peculiarly undercut sides; the width of the face and the base of the thread being one-half the pitch. The pump cylinder fits the perimeters of the threads. Space enough is left between the screws and the cylinder and between the faces of the intermeshing threads to allow a close running fit without actual contact. There is no end thrust of the screws in their bearings, because the back pressure of the column of liquid is delivered through the suction, S, at the middle of the cylinder, therefore the endwise pressure upon the screws in one direction is exactly counterbalanced by a like pressure in the opposite direction.

The suction connection opens into a chamber underneath the pump cylinder. The suction liquid passes through this chamber to the two ends of the cylinder and is forced from the ends toward the center by the action of the two pairs of intermeshing threads; the discharge being in the middle of the top of the cylinder, as shown at D. The power to drive the pump is applied to one of the shafts, and the second shaft is driven by means of a pair of gears, shown at G.

The pump has no internal packing, no valves and no small moving parts. The only packing is in the stuffing-boxes where the two shafts pass through the cylinder head.

Whether driven by a belt, an electric motor, or a steam engine, the driving power is applied directly and without the loss due to intermediate mechanism; as the screws are not in contact with the cylinder or with each other, the consequent absence of wearing surfaces gives the pump great durability.

176

These pumps have a high efficiency against a wide range of pressures: The power being applied direct, the thrust due to the back pressure of the column of liquid in the delivery pipe is balanced.

As the action of the screws on the liquid is continuous, the delivery is free from pulsation. By thus keeping the liquid in constant and uniform motion the efficiency of the pump is increased and the pump is made peculiarly suitable for certain specific purposes as there is no churning effect upon the liquids handled.

These pumps are much used in connection with hydraulic elevators by pumping directly into the elevator cylinders, as there is no pulsation. They are also used to pump oil into pipe lines and are driven by electric motors as well as by belts. For circulating pumps for brine and for fire purposes these pumps have certain peculiar advantages.

Table of Dimensions and Capacities of the Quimby Screw Pump.

177

178

Fig. 459.

Aer is the first element in many compound words of Greek origin meaning air, the air, atmosphere; in this connection it is combined with motor, defined as a machine which transforms the energy of water, steam, or electricity into mechanical energy—in this instance, is meant the changing of the power of moving air or wind into mechanical energy.

Wind is air put in motion. There are two ways in which the motion of the air may arise. It may be considered as an absolute motion of the air, rarefied by heat and condensed by cold; or it may be only an apparent motion, caused by the superior velocity of the earth in its daily revolution.

When any portion of the atmosphere is heated it becomes rarefied, its specific gravity is diminished, and it consequently rises. The adjacent portions immediately rush into its place to restore the equilibrium. This motion produces a current which rushes into the rarefied spot from all directions. This is what we call wind.

Meteorology is the science which treats of the atmosphere and its phenomena, particularly of its variations of heat and cold, of its winds, etc.

This is the great division of science to which one has to turn when searching for the first principles relating to the operation of aermotor pumps. The vast volumes of air which flow “hither and yon” are controlled by physical laws which act as accurately and unceasingly as those which control and hold in check the seemingly solid substance of the earth itself.

180

To sum up all observations, it can be said with truth that the sole force immediately concerned in causing the movements of the atmosphere, is gravitation.

So far as the prevailing winds are concerned it has been shown that where pressure is high, that is to say, where there is a surplus of air, out of such a region winds blow in all directions; and, on the other hand where pressure is low, or where there is a deficiency of air, towards such a region, winds blow from all directions in an in-moving special course.

This outflow of air currents from a region of air pressure upon a region of low pressure is reducible to a single principle, as already stated, viz., the principle of gravitation.

A regular east wind prevails about the equator, caused in part by the rarefaction of the air produced by the sun in his daily course from east to west. This wind, combining with that from the poles, causes a constant north-east wind for about thirty degrees north of the equator, and a south-east wind at the same distance south of the equator.

From what has now been said, it appears that there is a circulation in the atmosphere; the air in the lower strata flowing from the poles towards the equator, and in the upper strata flowing back from the equator towards the poles. It may be remarked, that the periodical winds are more regular at sea than on the land; and the reason of this is, that the land reflects into the atmosphere a much greater quantity of the sun’s rays than the water, therefore that part of the atmosphere which is over the land is more heated and rarefied than that which is over the sea. This occasions the wind to set in upon the land, as we find it regularly does on the coast of Guinea and other countries in the torrid zone. There are certain winds, called trade-winds, the theory of which may be easily explained on the principle of rarefaction, affected, as it is, by the relative position of the different parts of the earth with the sun at different seasons of the year, and at various parts of the day.

A knowledge of the laws by which these winds are controlled is of importance to the mariner. When the place of the181 sun with respect to the different positions of the earth at the different seasons of the year is understood, it will be seen that they all depend upon the same principle. The reason that the wind generally subsides at the going down of the sun is, that the rarefaction of the air, in the particular spot which produces the wind, diminishes as the sun declines, and, consequently, the force of the wind abates.

From its importance in practical meteorology Buys Ballot’s law may be stated in these two convenient forms. (1) Stand with your back to the wind, and the center of the depression or the place where the barometer is lowest will be to your left in the northern hemisphere, and to your right in the southern hemisphere. This is the rule for sailors by which they are guided to steer with reference to storms. (2) Stand with the high barometer to your right and the low barometer to your left, and the wind will blow on your back, these positions in the southern hemisphere being reversed. It is in this form that the prevailing wind of any part of the globe may be worked out from the charts.

It is as a source of energy, to be classified with heat, weight of liquids, electricity, etc., that air in motion (as in a windmill) has a place as a prime mover.

Prime movers, or receivers of power, are those pieces or combinations of pieces of mechanism which receive motion and force directly from some natural source of energy. The point where the mechanism belonging to the prime mover ends and that belonging to the train for modifying the force and motion begins may be held to include all pieces which regulate or assist in regulating the transmission of energy from the source of energy.

The useful work of the prime mover is the energy exerted by it upon that piece which it directly moves; and the ratio which this bears to the energy exerted by the source of energy is the efficiency of the prime mover.

182

In all prime movers the loss of energy may be divided into two parts, one being the unavoidable effect of the circumstances under which the machine necessarily works in the case under consideration; the other the effect of causes which are, or may be, capable of indefinite diminution by practical improvements. Those two parts may be denominated as necessary loss and waste.

The efficiency which a prime mover would have under given circumstances if the waste of energy were altogether prevented, and the loss reduced to necessary loss alone, is called the maximum or the theoretical efficiency under the given circumstances.

In windmills, the air, being in motion, presses against, and moves four or five radiating vanes or sails, whose surfaces are approximately helical or screw shape, their axis of rotation being parallel, or slightly inclined in a vertical plane, to the direction of the wind.

The velocity of the wind determines its pressure, and the pressure of the wind against the sails of the windmill determines the power developed by the mill. A mill of small diameter acted upon by a high pressure develops as much power as a large mill working under a lower pressure.

The mean average velocity of the wind for the entire United States is very nearly eight miles per hour. However, for large areas such as the great plains east of the Rocky Mountains, the mean average is about eleven miles per hour, and yet in certain small areas situated in the mountainous districts the mean average velocity is as low as five miles per hour. Therefore, in selecting and loading a mill, reference should be had to the wind velocity prevailing in that particular locality. In general, windmills loaded to operate in ten-mile winds can be depended upon to furnish a sufficient supply of water.

The variations in the velocity and pressure of the wind are considerable even within a brief time, and sometimes sudden and extreme. Winds of 100 miles per hour and upwards are on record. A very violent gale in Scotland registered by an excellent anemometer a pressure of 45 lbs. per square foot. During the severe storm at London, the anemometer at Lloyd183’s registered a pressure of 35 lbs. to the square foot. The gauge at Girard College, Philadelphia, broke under a strain of 42 lbs. per square foot, a tornado passing at the moment within a quarter of a mile. At the Central Park Observatory, a wind was recorded of 28.5 lbs. pressure per square foot.

If the wind were to blow continuously a very small windmill would suffice to do a large quantity of work and no storage capacity would be required, but when it does blow it is “free” and experience dictates that a mill shall be erected sufficiently large to pump enough water, when the wind does blow, to last over, with the assistance of ample storage capacity.

Average hourly velocity of the wind at following stations of the U. S. Weather Bureau, given in miles per hour:

184

Fig. 460.

Windmills can be divided into two general classes according to the inclination of the shaft: 1, Horizontal mills, in which sails are so placed as to turn by the impulse of the wind in a horizontal plane, and hence about an axis exactly vertical; and, 2, vertical mills, in which the sails turn in a nearly vertical plane, i.e., about an axis nearly horizontal.

On account of the many disadvantages connected with the horizontal windmill, it is seldom brought into use, being employed only in situations in which the height of the vertical sails would be objectionable, and this is liable to occur only in extraordinary cases. In this kind of mill six or more sails, consisting of plain boards, are set upright upon horizontal arms resting on a tower and attached to a vertical axis, passing through the tower at its middle part. If the sails are fixed in position, they are set obliquely to the direction in which the wind strikes them. Outside of the whole is then placed a screen or cylindrical arrangement of boards intended to revolve, the boards being set obliquely and in planes lying in opposite courses to those of the sails. The result is, from whatever direction the wind may blow against the tower, it is always admitted by the outer boards to act on the sails most freely in that half of the side it strikes, or from which the sails are turning away, and it is partly, though by no means entirely, broken from the sails which in the other quadrant of the side are approaching the middle line.

Fig. 461.

186

The illustration on page 184, Fig. 460, is a representation of the Corcoran windmill: it contrasts most interestingly with the same apparatus shown in Fig. 459—a windmill of the early part of the 17th century.

The figure below, 462, exhibits in detail the rear view of the Corcoran mill with the governor. As the speed of the wheel increases it swings the “tail” around, so as to bring the wheel at an angle with the direction of the wind; the latter failing to strike the blades squarely communicates less force, and in consequence the speed is diminished; in case of a very high wind the tail turns so as to present the wheel almost edgewise towards the direction of the blast.

Fig. 462.

Fig. 461 represents a Corcoran double action suction force pump. The base is hollow and contains the suction and discharge valves; a flange at the left-hand side receives the suction pipe while a corresponding flange on the right-hand side connects with the discharge pipe. An air chamber is attached to187 the discharge end. The valves may be reached by removing the bonnets on top of the base.

Fig. 463.

Fig. 463 is intended to represent an Ideal steel tank tower; the tank is herein located near the top. A force pump is used where water is delivered into an elevated tank as in this case; a lift pump is employed to discharge water at the spout and not to elevate above it.

The common term “Windmill pump” distinguishes a wind power pump from a hand pump, the difference being in an extension of the piston rod above the upper guide with a hole for connection with the pump rod from the windmill.

Such a pump, with the “pit-man” extending from the pump upwards into the tower, is shown in Fig. 465. This figure is introduced to show the tank connections with a regulator on the base of a four-post tower. The float in the water tank throws the mill in or out of gear according as the water rises or falls in the tank.

When the tank is filled with water it pulls the mill out of gear and stops the pump; as a result there can be no overflow or waste. The tank is thus not allowed to become empty and permit its drying apart, inducing leakage. But through the medium of the float in the tank, when the water has been lowered but a few inches, the mill is again put in gear and the tank refilled to the desired height, at which the float is set.

188

The syphon pump here illustrated, Fig. 464, is used to force water from shallow wells to elevations. The cylinder or barrel is situated within the standard and very convenient for inspection. It has an air chamber which is detachable.

Fig. 464.

The subject of tanks and cisterns is one almost vital to the successful operations of ordinary windmills, owing to the irregularity of the power to be utilized by the use of aermotors.

In another part of this work this important subject will be further explained and illustrated.

One of the most valuable special features of this windmill is its governor. It is so contrived that it insures immunity of the mill from injuries in destructive storms. It consists of a steel coiled spring of great resiliency, located at the base of the vane frame. Its strength is of such a character as to hold the wheel in the teeth of the wind under all ordinary conditions but is sure to yield under greater pressure.

Fig. 465.

189

USEFUL DATA
RELATING TO THE SIZES AND CAPACITIES OF PUMPING MILLS.

Table I.

Table II.

Table III.

Table IV.

Table V.

Table VI.

190

Table VII.

The preceding tables are based upon tests of the Sampson windmill as compiled by its makers, The Stover Manufacturing Co.; they deserve careful study by those planning the introduction of aermotors.

The power of a windmill depends—first, on the diameter of the wheel; and second, on the velocity of wind. To increase the diameter of the wheel is to increase its power in proportion to the area of the squares. Table I gives the horse-power of several sizes of mills working in a fifteen-mile wind: if the wind velocity be increased or diminished, the power of the windmill will increase or decrease in the ratio of the squares of the velocity. Table V will show the comparative power or force of the wind in velocities from eight to forty miles per hour for each square foot of surface.

Rules for approximately determining size of windmill to use.

The daily water consumption must be given as a basis for calculation. Divide this by 8 to find the hourly capacity of windmill, as if loaded aright the mill will pump on an average eight hours daily.

Multiply the quotient by total water lift in feet and with the co-efficient given in Table II.

The product will in Table I show what mill to use.

The size of the cylinder and discharge pipe will be found in Table III.

191

Fig. 466.

Table I gives the maker’s number of the pumping mill, and the number of gallons each will raise one foot high per hour, with a wind having a velocity of fifteen miles per hour. Example: No. 9 pump will raise 24,000 gallons of water one foot high in one hour. Now if the water is to be raised 50 feet then by dividing 24,000 by 50 the quantity raised becomes 480 gallons per hour.

From Table V it will be seen also that a wind velocity of fifteen miles per hour develops a power three times as great as an eight-mile wind, and a twenty-mile wind is twice as powerful as a fifteen-mile, or six times that of an eight-mile. Hence, a small increase in velocity greatly increases the power of the windmill, while a low velocity gives but little working force.

From Table VI it is seen that a twenty-five mile wind gives six times as much power as a ten-mile wind, but really gives twenty-six times the net efficient power of the ten-mile wind, therefore it will not be proper to calculate on using a power windmill in as low a velocity as ten miles.

From Table VII it is seen that the net efficient result is six times as great in a fifteen-mile wind as in a ten-mile wind, and sixteen times greater in a twenty-mile wind than in a ten-mile wind. Therefore, power windmills give best results when working in fifteen to twenty-five mile winds. A 12-foot power windmill working in a fifteen-mile wind will do more work than an average horse, and when working in a twenty-mile wind will do more work than two average horses.

192

A 14-foot windmill working in a fifteen-mile wind will do more work than two average horses, and when working in a twenty-mile wind will do more work than four good horses, while in a twenty-five mile wind it will do more work than six good horses.

Giving the above tables a practical application, a little thought will disclose what a wealth of power stands unappropriated and ready at hand to do many of the drudgeries of work for which large expenditures are annually made.

The uses of power windmills are so well understood that it seems out of place to elaborate upon them; the brief space allowed to giving information as to the power of this class of mills when working in different wind velocities, is best expressed in tabular form, Table VI.

Fig. 466 represents the working barrel of a deep well pump, such as are used frequently in connection with the larger sizes of aermotors.

The tube is usually made of heavy brass—this is drawn so perfectly, as to size and smoothness, that a re-boring is not needed.

The plunger is here shown with four cup leather packings, with one ball valve; the bottom valve is also a ball with the seat resting within a conical coupling at the bottom, this with a leather packing makes a water tight joint.

Should any accident happen to the bottom valve it may be withdrawn by lowering the sucker-rod until the threaded portion comes in contact with the nut underneath the plunger. By turning the sucker-rod the nut engages the thread on the top of the lower valve-cage. Then by withdrawing the sucker-rod both valves may be drawn up for examination or repairs.

194

Fig. 467.

Fig. 468. (See page 199.)

This class of pumps differs from the centrifugal pump, which is described and illustrated hereafter, in that it includes a revolving piston, while in the centrifugal pump there is a set of revolving blades which acts upon the liquid in the same way as a fan acts upon the air; the centrifugal pump receives the water in the center and throws it outward, while the rotary gathers the fluid up and leads it towards a central discharge.

The rotary pump substantially corresponds to the pressure blower, and in many cases is simply the rotary engine reversed; while the centrifugal pump is analogous to the fan-blower. The functions of a rotary are almost identical with those of piston and power plunger pumps.

The rotary pump on account of its cleanliness has been quite generally adopted for pumping all heavy liquids, such as starch, paint, soap, gummy oils, beer and hops, sewerage, bleachers, etc.

The rotary pump is used also in places where a piston or steam pump would be objectionable either on account of floor space occupied or for the reason that steam could not be had without too much expense for lifting and forcing water and other liquids which would not nor could not find their way through the tortuous and narrow passages of the average piston and plunger pumps.

For low heads of liquids the rotary is also somewhat more efficient than direct acting pumps and the absence of close fitting parts renders it possible to handle water containing a considerable quantity of impurities, such as silt, grain and gravel. This type of pump is compact and is generally self-contained, especially in the smaller sizes, and will deliver more water for a given weight and space occupied than the reciprocating types, while its simplicity of construction not only lessens the liability to derangement, but enables persons having a limited knowledge of machinery to set up and operate these pumps successfully.

196

Rotary pumps are driven by means of belts from line shafting and by wheel gearing, and also by direct connection to any prime mover such as a steam or gas engine, hydraulic or electric motor.

Rotary pumps may be divided into several classes according to the forms of, and methods of working the pistons or impellers, as they are usually called, that is, according to the construction and arrangement of the abutments. The abutment receives the force of the water when driven forward by the pistons or impellers and also prevents the water from being carried around the cylinder, thus compelling it to enter the delivery pipe. In the construction of the impellers or pistons, and of the abutments, lie the principal differences in rotary pumps. In some pumps the abutments are movable, and are arranged to draw back, as shown in Fig. 469, to allow the piston to pass. In others the pistons give way when passing fixed abutments, and in others the pistons are fitted with a movable wing, as in Fig. 472, which slides radially in and out when passing the abutment.

Fig. 469.

Pumps of this type having no packing and springs to prevent leakage and in which the pistons work in cylindrical casings or cylinders are quite durable and in many instances have been known to run for months without stopping. The later construction of this pump is shown in Fig. 470; this design of pump is more economical, as a rule, owing to the fact that the strain on the belt is uniform at all points in the revolution of the pistons.

Fig. 467, page 194, represents one of the oldest and most efficient forms of the rotary pump. Cog wheels, the teeth of which are fitted to work accurately into each other, are inclosed197 in an elliptical case. The sides of these wheels turn close to those of the case so that water cannot enter between them. The axle of one of the wheels is continued through one end of the case (which is removed in the figure to show the interior) and the opening made tight by a stuffing-box or collar of leather. A crank is applied at the end to turn it, and as one wheel revolves it necessarily turns the other, the direction of their motions being indicated by the arrows. The water that enters the lower part of the case is swept up by the ends of each cog in rotation; and as it cannot return between the wheels in consequence of the cogs being always in contact there, it must necessarily rise in the ascending or forcing pipe.

Fig. 468 represents a pump similarly constructed to the foregoing, but having cams shaped so as to reduce the wear.

Fig. 470.

In Eve’s pump, shown in Fig. 469, a solid or hollow drum, A, revolves in a cylindrical case. On the drum are three projecting pieces, which fit close to the inner periphery of the case. The surface of the drum revolves in contact with that of a smaller cylinder, B, from which a portion is cut off to form a groove or recess sufficiently deep to receive within it each piston as it moves past. The diameter of the small cylinder is just one-third that of the drum. The axles of both are continued198 through one or both ends of the case, and the openings made tight with stuffing-boxes. On one end of each axle is fixed a toothed wheel of the same diameter as its respective cylinder; and these are so geared into one another, that when the crank attached to the drum-axle is turned (in the direction of the arrow) the groove in the small cylinder receives successively each piston, thus affording room for its passage, and at the same time, by the contact of the edge of the piston with its curved part, preventing water from passing. As the machine is worked, the water that enters the lower part of the pump through the suction-pipe is forced round and compelled to rise in the discharging one, as indicated by the arrows. Other pumps of the same class have a portion of the small cylinder cut off, so that the concave surface of the remainder forms a continuation of the case in front of the recess while the pistons are passing; and then, by a similar movement to that in the figure described, the convex part is brought in contact with the periphery of the drum until the return of the piston.

Figs. 471 and 472.

The next improvement in rotary pumps is shown in Fig. 470, page 197. This type was used for many years as a fire pump. The Silsby fire engine of the present day is practically this pump in design although it has packing strips in the center of each of the long teeth of the elliptical gears.

199

Following Eve’s invention were a series of claims which embodied the design shown in the engraving, see Fig. 471, where a sliding partition or abutment, A, was used to imprison the steam. As the piston or inside cylinder turned around, the abutment was pushed up and fell of its own gravity. A strip of metal supported this abutment and furnished a suitable wearing surface upon the surface of a revolving cylinder and also accommodated itself to the tilting motion introduced by the eccentricity of the revolving cylinder.

In Fig. 472 the sliding abutment has been placed in the side of revolving cylinders and the axis of this cylinder is in its center. In this case the abutment is pushed in by its pressure upon the inside of the case and is thrown out by its centrifugal force assisted by spiral springs.

The engraving, Fig. 468, gives a view of Gould’s rotary pump, with the case removed; long practical experience has demonstrated that the revolving cams or pistons are of such a shape as to produce the minimum of friction and wear with the greatest results.

The cases which receive these cams are engine lathe turned and bored and so true and smooth that the cams when in operation create almost a perfect vacuum and will “pick up” water for a long distance and hold it efficiently. The cams are carefully and accurately planed to mesh into each other to fit their case.

It is a point worth noting that if a little good oil be put into the case of these pumps before and after using at first, or simply to pump air with the oil a few times, the cams become as hard upon the surface as tempered steel, and are almost unaffected by long use afterwards. Drip plugs are provided for draining pumps in cold weather. To do this, turn the cams backward a single revolution to release all water.

The Taber pump is one of the best known of the rotary class. It consists of three parts only, that is to say, (1) the outside shell or case, (2) the piston, and (3) the valves.

Referring to the engravings herewith (Figs. 474 to 481), the200 outside case or shell, A, is made either of brass or iron as the case may be, Fig. 476, bored out at F to receive the piston, C, Fig. 478, to which power is applied at G.

Fig. 474.

This cylinder has two heads or covers, BB, Figs. 475 and 477, which close the cylinder and has journal bearings to carry the piston combined with packing boxes to prevent leakage of the liquid passing through the pump. The valves, Figs. 479, 480 and 481, DDD, are plates of composition which slip through the piston fitting neatly into the slots, EE, Fig. 478.

201

Figs. 475-477.

Fig. 478.

Figs. 479-481.

These valves really perform the work of pumping. It will be observed that substances which would easily clog up an ordinary pump with clack valves, will pass through this pump202 without difficulty; there are no springs in this pump, nor will it get out of order with the average treatment, and it pumps all kinds of liquids, either thick or thin, such as are found between the two extremes of water, and brewers’ grains.

It is designed to handle a large amount of fluids and semi-fluids under a medium pressure, and being well balanced it may be run fast or slow as desired.

Directions for setting and operating Taber pumps.

1st. Bolt pump firmly to the floor, and if possible set it so that the liquid runs into it, which will add very much to the life and duty of the pump.

2nd. See that all parts are well oiled.

3rd. Experience has proved that common candle wick soaked in tallow is the best material with which to pack rotary pumps. The wick should be double and twisted into a compact rope and driven into the boxes as tightly as possible with a piece of hard wood tapered to fit the box. Such a tool as described is furnished with each pump. Do not under any circumstances use iron calking tools which mar the bearing and causes them to quickly cut out the packing.

4th. If from any cause the pump should become clogged, do not use a lever in starting it. Remove the plug from bottom and work the pulley back and forth till the pump is relieved. If this does not free it, remove the outside head and all parts will be accessible.

203

When putting heads back on the pump use ordinary newspaper for packing, nothing thicker, as thicker packing destroys the suction.

Prevent all leaks in suction pipe which would impair the vacuum.

The suction should furnish an uninterrupted supply to the pump, to enable the pump to throw its full capacity. Never use pipes smaller than the openings in pump.

Open all drips in cold weather to prevent freezing.

All packing boxes should be kept in order and never allowed to leak.

The illustration, Fig. 482, page 204, represents a rotary pump of the Holyoke pattern to be attached by a clutch to a line shaft—the gears, as shown, are merely to transmit the power to the impellers. The safety valve with lever and weight, shown in the cut, are designed to be attached to the discharge pipe to guard against over pressure, which might occur through the closing of valves.

Fig. 483 shows an emergency pump of the Holyoke rotary pattern. It is of the same general design as the one previously alluded to. It is driven directly from the line shaft by friction gearing instead of toothed wheels. The hand wheel attached to the end of a screw is used to press the smaller friction wheel against the larger and thus transmit the power to drive the pump.

This mechanism is not liable to injury by being thrown instantly into gear in case of fire, as would be the case if gear wheels were used.

These pumps are largely used in mills located in the Eastern United States, as they may be started up in a few moments at full speed without slowing down the engine or motor driving the line shaft.

The shaft bearings are all made of large proportions to avoid heating and excessive wear when suddenly put under full load.

204

Fig. 482.

Fig. 483.

205

Figs. 484 and 485 are views of a rotary pump driven by steam and largely used for fire apparatus. These pumps are in general use in mills and factories, and can be installed wherever the necessary steam and water supply are available.

The pump is built on a rigid iron base plate, and is furnished with air chamber, water-pressure gauge, oil feeders and everything necessary to make it complete and ready for permanent steam and water connections. The discharge outlets can be adapted for forcing water through either pipe or hose.

A perspective view of this pump is given in Fig. 484 and a sectional plan of the same appliance appears in Fig. 485.

Both engine and pump are of the rotary type and the construction of these parts is precisely as described in connection with its adaptation to use in the Silsby steam fire engine.

These pumps can be thoroughly drained and, with their interior surface well coated with oil and No. 2 pure Graphite, they can be “laid up” indefinitely and with certainty as to their starting promptly when wanted in an emergency. Water accumulated in the steam pipe will pass through this cylinder without causing damage, and the free action of the pump will not be defeated by the “sticking” of valves or the corrosion of exposed parts.

In the operation of rotary pumps trouble is often experienced through an improper adjustment of the ends of the case. If the case is too long there will be leaks of water pass the ends of the impellers and on the other hand if the case is too short the ends of the impellers will bind and cut, through excessive friction. Hence great care is necessary in adjusting the ends of the case so that the pump may run freely yet without leaks. The packing boxes around the shafts must not be screwed up too tight otherwise the shaft will be injured.

It has been found by costly experience that for emergency fire pumps leather belts are unreliable, hence these two pumps, Figs. 482 and 483, are driven by direct connection with the shaft in the first instance and through cast iron friction gearing in the second.

206

Fig. 484.

207

Fig. 485.—See page 205.

208

Fig. 486.—See page 210.

209

The engraving, Fig. 487, shows Root’s rotary pump. This has two impellers which are geared together and each turn at equal speeds towards one another at the top. The engraving, Fig. 488, also shows a Root pump with two impellers each having three wings or lobes. The pump proper consists of half circles, AA, with air chambers, DD, cast with them, the head plates, B, carrying the bearings, and the revolvers, CC, together with shafts, EE. The shafts carry involute gears at each end which keep the lobes of the two impellers in their relative positions, and rotate them. Either shaft may be made the driving shaft and to deliver water, as shown by the arrows in the cross section, the shafts revolve so that the tops move toward one another.—Same as in the preceding case.

Fig. 487.

Fig. 488.

The action of this pump is as follows: the suction pipe on starting, being full of air, the first few revolutions of the pump expel the air until the required vacuum is formed, which allows atmospheric pressure to raise water into the pump. It then flows between the case and the lobes into the space, F, and is carried by the impellers to the discharge edge of the case, point, G, where it enters the discharge pipe. Each succeeding lobe brings up an amount of water equal to spaces, FF, thus delivering the contents of the six at each revolution. The irregular form of210 the lobes keeps them in contact at the center line, thus preventing the return of water into the suction below.

Heads of water from 10 to 250 feet are successfully handled by this type of pump, with a slip of from 5 to 15 per cent., according to the discharge pressure.

The three-lobe impellers provide a double lock against the return of water between the case and impellers, at the same time allowing a very free inlet and outlet for the water. The delivery of water from this pump is smooth and continuous.

The large engraving, Fig. 486, page 208, shows the exterior of this same pump with journal bearings and gears encased at each end. This pump may be driven by motor or engine.

Large rotary pumps for dredging purposes with their engine equipment for salt water service, include surface condenser outfits with air pumps, feed pumps, fire pumps, etc. The dredges for fresh water are very large cross-compound engines, double-acting air pumps and jet condensers with the usual complement of vertical duplex feed pumps, fire pumps, etc. The air pumps are of a very novel arrangement, inasmuch as it is possible by the manipulation of valves and cocks provided for the purpose to separate the pumps and run one side entirely independent of the other side. These dredges are self-propelling and sea-going; some of them are fitted with immense bins in which the dredged material is deposited, and when full, the vessel propels herself out to deep water, dumps the sand or mud and steams back to repeat the operation.

The centrifugal pump raises the liquid to be displaced, by means of a rapidly revolving fan having two or more blades straight or curved, fastened upon a shaft and fitting closely into a case having an inlet for water at the end center and an outlet at one side or on top of the case tangent to the circle described by the fan.

Most people are practically acquainted with the principle of the centrifugal pump, viz., that by which a body revolving round a center tends to recede from it, and with a force proportioned to its velocity: thus mud is thrown from the rims of carriage wheels, when they move rapidly over wet roads; a stone in a sling darts off the moment it is released; a bucket of water may be whirled like a stone in a sling and the contents retained even when the bottom is upwards.

The earliest history of the centrifugal pump cannot be traced, but it is known that centrifugal machines for lifting liquids were in use during the latter part of the seventeenth century. About 1703, Denis Papin, the famous French engineer, designed his “Hessian Suck,” a form of centrifugal pump embodying nearly all of the essential features of the present-day machine. Drawings of this pump are in existence which show that Papin was not only a designer of no mean ability, but that he had a good comprehension of the principles with which he was dealing. After Papin there seems to have been no further development of his ideas until 1818, when the earliest prototype of the present form of centrifugal was brought out in Massachusetts and has since been known as the “Massachusetts pump.” This pump was of the type designated “volute,” and was provided with double suction openings and an open impeller. It was re-invented by Andrews and others in 1846, and was shortly afterwards introduced into England by Mr. John Gwynne.

212

Centrifugal pumps have now attained a degree of perfection, which makes them a serious rival of the plunger pumps. The high-class turbine pumps of to-day are simply machines in which the water is given a velocity which is partially changed to pressure before discharge, and the pump is designed so that the well-known actions, outlined above, proceed along natural lines, which are, to use the common phrase, lines of least resistance. It is simply a question of careful design.

The modern pump causes the water to flow along paths naturally due to the forces acting and to guide the stream in such a way as to avoid the production of eddies and whirls within itself which so enormously cut down the efficiency.

Fig. 489.

The blades now take the form of “impellers” which have warped surfaces whose form is the result of careful calculation, and the water, after leaving the impellers, is guided by vanes of equally and carefully calculated form. It is owing to the correct form of the guide vanes that the nearly perfect conversion of velocity into pressure head is possible, and this is the principal factor which produces the high efficiency shown in tests.

When pumping against high heads, the units are arranged in stages or series. The discharge from one is led to the inlet of the next in series, the separate units being usually mounted on one shaft, and the whole really forms one machine. In this manner heads approaching 2,000 feet are worked, still preserving the high efficiency which in some cases reaches between 80 and 90 per cent.

The ability to generate such pressures enables them to be used for feeding boilers, and their efficiency particularly commends them for this purpose.

213

Fig. 490.

The centrifugal pump is the converse of the turbine water-wheel. Its development has been analogous to that of the steam turbine in that both were abandoned in favor of reciprocating machines before having been thoroughly exploited; the pump because the principles of its action were not clearly understood, and the steam turbine because of mechanical difficulties in its construction.

Opposite the title page of this book can be seen a representation of a centrifugal wheel of ten thousand horse power; it will repay the careful student to consult also page 133 of part one of this work for the details of this enormous machine; the curious will also be interested in an early form of the centrifugal pump to be seen in Fig. 489 and its description in the Note on page 214.

Fig. 491.

Fig. 492.

214

Where large quantities of water are to be moved quickly and more especially in cases where the water is impure and contains floating matter, as well as sand, mud, coal and the like, as in wreckage, the centrifugal pump has its peculiar advantages. It is suited particularly for use in tanneries, paper mills, dry docks, corporation work such as building sewers, sand dredging, and with water that contains large quantities of solid matter held in suspension. Pumps used for these purposes have to be primed on starting, and the suction pipe should be as short as possible. Long suction pipes very much impair the efficiency of this type of pump. They will draw water upwards of twenty feet but nothing like the full capacity of the pump can be realized under such circumstances. It is always better to lower the pump as much as possible and force the water instead of trying to suck it.

Centrifugal pumps designed to raise clean water alone should not be used for any other purpose, that is to say, pumps for handling more or less solid matter mixed with the water have much more clearance in the case than those for pumping215 clean water. The fan is also made differently so that it cannot be clogged up by lumps of coal, gravel, and sticks of wood. The accompanying engravings, Figs. 490, 491 and 492, illustrate these ideas, showing the three progressive grades of fans for the kinds of work alluded to.

Fig. 490 shows a fan with hollow arms for clean water only.

Fig. 491 shows the disc type of fan for water containing grit, pulp, etc.

Fig. 492 exhibits a fan used in dredging pumps used for all sorts of stuff that will pass through the connecting pipes.

Fig. 493.

There are two general types of centrifugal pumps, viz., 1, single suction, Fig. 493, in which the suction pipe enters the end of case parallel to, and in line with its center; 2, the double suction, Fig. 494, in which the suction pipe is divided forming a U shape and enters the case at both sides of the center.

The single suction is used for clear water only, while the double suction will pass everything that enters the suction pipe—see engravings.

216

When the pump is located above the water, it has to be primed before it will raise water. For these purposes an ejector, or exhauster, is frequently employed, which will exhaust the air and draw water up from the required depth. The arrangement of the ejector is illustrated at A, in Fig. 496, and is the smallest and most convenient contrivance that can be used for this work. It is screwed into the highest part of the pump, and is connected by a separate steam pipe to boiler. In a short time after turning on steam, the pump will be primed, the pump remaining stationary during the operation of priming.

Fig. 494.

To prevent air returning through the discharge pipe, a check valve, B, is used. For larger pumps a gate valve is generally employed here.

A foot valve fitted with a strainer to keep out obstructions likely to clog the pump should be used as it keeps the pump primed and ready for immediate use.

The general form of the blades is of great importance in this type of pump, because the water is driven through the fan partly by the pressure of the blades on the water and partly by centrifugal force. The ratio which each of these forces bears to the other varies in the same pump, depending upon the proportion the speed bears to the height of it. With low lifts and high speed the water is discharged with but little rotary motion, the resistance to the outward motion of the water being so small that the oblique action of the blades is sufficient to effect the discharge without imparting to the water the same speed of rotation as is given to the fan. The principal object in217 this type of pump is to effect the discharge of as large a volume of water as possible with the least rotary motion. The power absorbed in imparting the latter motion is not given up later on and consequently is lost, while the rotary motion tends to impede the flow of water.

Fig. 495.

The passage through the pump should be so timed as to produce a gradually increasing velocity in the water until it reaches the circumference of the fan, then a gradually decreasing velocity until it is discharged from the pipe. These conditions218 are met by having a conical end to the suction pipe, and a spiral casing surrounding the fan. The form of the casing should be such that the water flowing round the casing will move with the same velocity as that issuing from the fan; the casing enlarges from that locality into the discharge pipe.

A small increase in the number of revolutions of the fan after the pump commences to discharge produces a large increase in the volume of water delivered.

Fig. 496.—For description see page 216.

Fig. 495, upon the previous page, is intended to show a Boggs & Clarke hydraulic dredging or sand centrifugal pump. This is a heavy strong pump fitted with flap valve, without close fitting joints, but with ample room for the water to wash away the sand from the working parts. The cut shows the pump with ejector for priming and large elbow to discharge through. The pump is lined with sheet steel fitted so that it can be easily and cheaply replaced. The diameters in which these pumps are made run from 4 to 12 inches inclusive.

Table.

219

Fig. 497.

Smaller sizes for pumping sand and gravel are made with cast chilled linings with chilled piston, and brass covered shaft especially adapted for stone and marble mills to carry the sand to the saws, or for mining where there is a large quantity of sand to be pumped with water.

The table will convey an idea of the capacity, sizes, etc.

For pumping sand or heavy material the speed of pump should be increased 25% more than for water.

220

Fig. 498.

221

The engraving Fig. 497 exhibits a steam-driven centrifugal pump of an approved design constructed by the Morris Machine Works.

This pump is directly connected to the engine and has a double suction. Pumps directly connected to engines are to be preferred over belt-driven pumps when conditions of elevation, etc., will allow, as they are self-contained, take up less space and are more economical.

The figure 498 shows a 20-inch hydraulic dredge, directly connected to a 450 horse-power triple-expansion engine. A hydraulic dredge consists mainly of a centrifugal pump with its driving engine and boiler, and hoisting machinery for handling suction pipe and boat; the pump in operation creates a strong suction flow in the suction pipe, sufficient to pick up the material and draw it into the pump, from which it is again delivered through the discharge pipe any distance to point of delivery, and can at same time be elevated to reasonable heights. Sand, mud, silt, etc., are readily picked up by the suction force only, but where material is packed it must first be agitated.

Table.

222

The steam shovel, bucket or elevator dredge will do efficient service in raising material, but none are capable of delivering the material except within a very short radius of the dredging operation. The centrifugal dredge not only raises the material, but also delivers it at the place wanted, at one operation. Besides, it is practically impossible to build any other type with the enormous capacity that some hydraulic dredges have.

Fig. 499.

Fig. 499 is a perspective view of a centrifugal vertical pump of the submerged type. This pump is used largely by contractors in excavations and coffer dam work and for keeping pits drained.

A double suction centrifugal pump, driven directly by a steam engine, is shown in Fig. 497; these are generally and very satisfactorily used for circulating water through surface223 condensers and the cooling pipes in refrigerating systems. The engine and pump thus combined occupy small floor space and consequently little masonry is required for a foundation.

Fig. 500.

The Buffalo centrifugal pump is shown in Fig. 500. These are built by the Buffalo Forge Co. in two types, viz., the submerged and the suction; the latter is the one shown in the cut. The suction type is employed for pumping from mines, pits, etc., and all places where the supply will not allow of a horizontal pump to be used, or in others where the supply is either below the pump, or sometimes above and at other times below. This type possesses merit above the submerged design in that it will work equally well, when set either above or below the liquid to be pumped.

Multi-stage centrifugal pumps. Experience has demonstrated that by placing several pumps together and discharging from one into the other, water can be delivered to almost any224 height. For a long time after the introduction of centrifugal pumps, it was supposed that about sixty feet was the limit for their economical working, owing to the high speed at which they had to be run to accomplish the results desired.

It was a discovery of importance, that by coupling two or more pumps in series, so that each pump worked against only a part of the total delivery head, water could easily be raised to even two thousand feet or any reasonably high head with satisfactory efficiency. Pumps connected in this way will throw more water at a given speed than when operated separately, and are therefore attended by less wear and tear.

Fig. 501.

Pumps worked in series are built compound, triple or quadruple as required by service either belt driven or directly connected to engines. Owing to the fact that they have no valves or absolutely close-parts, they are able to pump muddy or gritty water with sand in suspension, and are, therefore, especially in the vertical type, the only ones that can be successfully used for draining deep mines.

Fig. 501 is designed to illustrate a four stage centrifugal pump, or a quadruple compound pump capable of lifting water 250 feet.

225

Fig. 502.

226

Explanation of diagram page 225. In determining the requirements best suited as regards rotation of shaft and connection with the suction and discharge pipes, in installing a pump, the figure 502, will be found a convenience. It is important to run the most direct pipes with the least number of elbows or bends.

The diagram relates particularly to the centrifugal pumps made by the Morris Machine Works of Baldwinsville, N. Y.; the principle is, however, of general application. In making use of the diagram each number represents a particular design. See Note.

How to determine right-or left-hand pumps. If, when standing at the suction end of pump, looking over the pump shell toward the pulley, the top of the shaft revolves from right to left, or against the hands of clock, the pump is right-hand, and from left to right, or with the hands of clock, it is left-hand.

Directions for erecting and running centrifugal pumps. Place the pump as near suction water as possible, and limit suction lift to 20 feet or 25 feet.

Erect the pump so that the pump shaft is level; in bolting to foundation be careful that the frame is not sprung. See that the bearings are clean and well oiled. The suction pipe and stuffing-boxes must be air-tight.

Never use pipes smaller than those represented by the flanges on the pump; avoid elbows or bends as much as possible; if discharging long distances, use pipes one or two sizes larger than ordinary.

Whether a foot valve is used or not, a strainer should be attached to the suction pipe to prevent large substances from entering, that might choke or clog the pump, but be careful that suction area is not contracted.

227

Run the pump in proper direction, as indicated by arrows cast on the pump shell.

If the combined length of suction and discharge pipe is more than 50 feet, the speed must be increased to overcome friction.

Before starting, prime the pump so that suction pipe and pump are filled with water.

Warm water can only be raised by suction to moderate heights, and if very hot it must flow to the pump. To prevent freezing in cold weather, drain by unscrewing plug provided in the bottom of the pump shell.

Sometimes a pump when first started will deliver a good stream of water, which gradually diminishes in volume until it stops entirely. One reason for this is a leak in suction pipes or stuffing-box of pump, or, when suction primer is used, in the hand pump stuffing-box. Another reason might be that the pump lowers the suction supply, thus increasing the lift until there is not sufficient speed for the elevation. If the pump works indifferently, delivering a stream obviously too small, it is generally because the pump was not properly primed and some air remains in the top part of pump shell. Unless primed by steam ejector, the pet cock or plug found on top of pump shell should always be open while priming, and the pump must not be started until water flows out of same.

A pump with horizontal top discharge and short length of discharge pipe is sometimes difficult to start, especially if suction lift is high, owing to the fact that the water is thrown228 out of the pump shell before the water in the suction pipe has got fairly started, thus allowing air to rush back into the pump. If the pump is to work under this condition, it is better to use a pump with a vertical discharge and deliver through an elbow, or else lead the discharge pipe upward for a short distance so as to keep a slight pressure, or head on the pump, and after priming as high as possible start quickly.

Generally nothing is gained by running a pump above the proper speed required for a given elevation.

In addition to what is said in connection with the priming device illustrated on page 218, numerous other methods have been adopted to suit pumps of various designs. The accompanying engravings represent those largely used.

Fig. 1 illustrates a multi-stage turbine pump with ejector for priming. The ejector is connected to the highest point on the pump casing, and either steam, air or water under pressure may be employed in it to produce a vacuum.

Fig. 2 shows an auxiliary hand pump mounted on top of the discharge casing. When the pump is ready to start, the gate valve on the discharge is closed, and by operating the hand pump a vacuum is produced and water drawn in, filling the suction pipe and casing.

The method of priming shown in Fig. 3 may be resorted to where a foot valve is used on the suction pipe. Water is allowed to run into the pump until it reaches the discharge flange, when the supply is shut off, and the pump may be started.

After the pump has been properly primed, it should be started before the gate valve on the discharge is opened. When full speed is reached, the discharge gate may be slowly opened, and the pump will perform its work.

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It is always best to use a foot valve in connection with centrifugal pumps where the lift is more than three to four feet, and even under these low lifts where long suction pipes are used to conduct water long distances, foot valves should always be used to keep the pump and suction pipe charged.

Figs. 1, 2 and 3.

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Fig. 503.

The Turbine Pump is suited to very high lifts, even exceeding 2,000 feet. An admirable example of this class of pumps is described in the following paragraphs:

The Worthington turbine pump has been developed by a long series of experiments. The diffusion vanes which form the distinguishing feature, take the place of the usual whirlpool chamber and assist in bringing the water to rest without internal commotion or shock. They correspond in function to the guide vanes of turbine water-wheels. One of the difficulties presented by high-lift centrifugal pumps has been the great peripheral speed required when only a single impeller is employed. This has been overcome by mounting a number of discs or impellers, each operating in a separate chamber, upon a single shaft and passing the water through the impeller chambers in succession. The lift can thus be multiplied three, four or five times, while the number of revolutions is kept within bounds. It has been demonstrated that on the same work and within reasonable limits, multi-stage centrifugals are more efficient than single-stage pumps, the increased efficiency being due to a decrease in the frictional losses coincident with the reduced peripheral speed of the impeller.

It is well known that the turbine water wheel was perfected less by mathematical processes than by intelligent cut and try methods. It has been the same with the turbine pump, whereby the vanes and passages have been shaped and tested by practical experiments, followed in each case by comparison of results. The constant aim has been to avoid eddies and secure a favorable discharge of the water.

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Fig. 504.

233 The ills. on the opposite page (Fig. 503), which represents in outline a Worthington turbine pump, indicates the difficulty of exactly and mathematically designing such a mechanism. In the system shown only suction and discharge pipes are employed, the water entering axially and issuing radially. The impellers remain in perfect longitudinal balance regardless of their number or the head against which the pump is operated, this balancing of the impeller being secured by an ingenious system of “triple vanes.”

The diffusion vanes. In the Worthington turbine pump the efficient conversion of energy is assured by an original system of diffusion vanes disposed in the throat opening between the periphery of the impeller and the annular casing, in much the same manner that guide vanes are placed in a reaction turbine water-wheel. These vanes form tangential, expanding ducts from which the fluid emerges at about the velocity existing in the chamber. They also eliminate all drag and friction between the periphery of the rapidly revolving impeller and the slowly moving water in the discharge chamber.

The turbine pump has created an entirely new field of application for centrifugal pumps, embracing mine drainage, water-works, and numerous other services where rotary pumps are desirable but have not been employed, owing to their former limited efficiency at high heads.

As a sinking or station pump for mine service, the turbine pump is ideal. There are no valves, guards or springs, no reciprocating parts, and, most important of all, there is no contact surface in the machine except the shaft and its bearings. The design is such that parts subjected to the action of mine water may be made of acid-resisting metal, and, when desired, lead-lined.

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Fig. 505.

235

Fig. 506.

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Fig. 507.—See page 241.

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Turbine pumps of excellent design (Fig. 507) of high efficiency are built by the Byron Jackson Machine Works of San Francisco, California. The operating elements of these pumps are rotating impellers containing spirally-curved water passages, and fixed guide passage between successive impellers. The water enters the passages of each impeller at the center and by the rotation is forced out into a collecting chamber surrounding the periphery of the impeller. The ducts which lead the water from there back to the center of the next impeller are suitably curved to act as guide passages, similar in action to the guide buckets of a turbine. The water then enters the next impeller parallel with the shaft, its rotary motion having been transformed by the guide passages into rectilinear motion.

Fig. 509, a drawing of a vertical pump in section, shows the relative arrangement of impellers (marked A) and guide passages (B). This pump has the suction entrance at the top; the discharge leaves the collecting chamber of the last (lowest) impeller tangent to the circle. The shaft rests in a thrust bearing at the top, and is further held by bearings formed in the successive sections of the case. At the bottom it is provided with a special balancing arrangement, described here after.

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Fig. 508.

Each impeller, where it joins the guide passages of the preceding case section, is fitted into the case so as to form as tight a joint as possible without introducing any great frictional resistance to rotation. With the exception of the entrance opening, the external surface of the impeller is exposed to the delivery pressure, so that there is a resultant upward pressure on each impeller, equal to the area of its entrance multiplied by the difference between the entrance and discharge pressures of that stage. If all the impellers are alike, the total upward thrust is equal to the product of entrance area multiplied by the total head on the pump. The pumps are so proportioned that this upward thrust slightly exceeds the weight of the rotating portion, consisting of impellers and shaft. The excess of upward pressure, however, is relieved by the balancing device located at the lower end of the shaft, with the result that the239 rotating part is precisely balanced, thus relieving the thrust bearing of all load while the pump is running.

The balancing device referred to consists of two chambers, C and D, formed centrally in the bottom of the lowest section of the pump case. The large chamber, C, encloses a projecting hub, E, on the lower surface of the impeller. This hub of course rotates with the impeller, and the joint between the hub and the walls of the chamber is, therefore, loose enough to allow water from the delivery side of the last impeller to leak into chamber, C, and establish the full discharge pressure in that chamber. The small lower chamber, D, contains a plug, H, which may be adjusted endways by means of screws. The forward end of this plug fits closely into a recess in the face of the hub, E, which recess, communicates, by way of the hollow central part of the hub and the passage, g, with the entrance side of the last impeller.

The action of the device is as follows: when chamber, C, becomes filled with water, or rather when leakage through the joint around the tube, E, has raised the pressure in the chamber, C, to the delivery pressure, the total upward pressure on the impellers is greater than the total weight of the rotating part of the pump. The rotating element is therefore lifted until the recess in hub, E, is raised clear of the plug, H. In this position the pressure in chamber, C, is relieved through the passage, g, with the result that the rotating element again settles down over the adjusting plug, H. As this action tends to recur, a position of equilibrium is established near the point where the plug just enters the recess in the hub, E. The precise position of this point may be altered by the adjusting screws of the plug, H, thereby adjusting the endwise position of the impellers in the casing. When the pump is not in operation, of course the upward pressure of the water does not act, and the weight of the rotating part must be carried by the thrust bearing.

Fig. 509.

When these pumps are built with horizontal shaft, the unbalanced pressure which is thus turned to account in the vertical pump becomes harmful and must be avoided. The arrangement240 by which this is accomplished is shown in Fig. 510, where the letters, A and B, designate respectively the impellers and the guide passages as before. The rear of each impeller, that is, the side opposite the entrance opening, bears a short annular projection, S, fitting within a similar ring, t, projecting from the casing. The circular chamber formed by these two rings communicates, through holes, V, in the web of the impeller, with the entrance side of the impeller. The chamber being241 slightly larger than the entrance opening of the impeller, it serves to eliminate all thrust on the impeller in the direction of the suction (since the remainder of the external surface is exposed to the discharge pressure), and produces instead a small thrust directed toward the discharge end.

This small resultant thrust is taken up by a balancing device at the end of the shaft precisely similar to that used in the vertical type of pump, as previously described. The balancing action thus secured serves to fix the endwise position of the rotating part; moreover, it affords sufficient margin to compensate for longitudinal thrusts which may result from causes such as slightly non-central position of the impellers in their casing.

Pumps of this design are built for heads of from 100 to 2,000 ft., the number of separate impellers or “stages” being properly proportioned to the head. About 100 to 250 ft. head per stage appears to be allowed. A high efficiency of working, from 70 to 80%, is said to be realized.

The horizontal two-stage pump shown in Fig. 507 is one built for the water-works of the city of Stockton, Cal., to deliver 1,500 gallons per minute against a head of 140 ft., at 690 r. p. m. It is driven by a 75-HP. induction motor of the Westinghouse Electric & Mfg. Co. type, of Pittsburg, Pa. Pump and motor are mounted on a common base, and their shafts are solidly coupled. This pump was guaranteed to have an efficiency of at least 75%, but we are informed by the manufacturers that the official test showed it to have an efficiency of 82%.

The vertical pump of four stages, shown in Fig. 508, has a discharge capacity of 450 gallons per minute and delivers against a head of 500 ft. The same type of pump, however, will work against heads up to 800 ft. The mounting of the pump in the present instance is at the bottom of a 200-ft. pit; the pump shaft leads vertically to the surface, where it is driven by belt. A closely similar installation has been made, where two vertical three-stage pumps operate under a head of 310 ft. The pumps are located in a 30-ft. pit, and their shafts are extended242 to the surface, where they carry each a 200-HP. induction motor mounted directly on the shaft. The balancing action of the pump was in this case designed to be sufficient to carry the entire weight of the rotating part, that is, motor, shaft and pump impellers.

Fig. 510.

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Fig. 511.—See page 251.

Fig. 512.—See page 251.

This consists, in its most simple form, of a steam nozzle, the end of which extends somewhat into the second nozzle, called the combining or mixing nozzle; this connects with, or rather terminates in, a third nozzle or tube, termed “the forcer.” At the end of the combining tube, and before entering the forcer, is an opening connecting the interior of the nozzle at this point with the surrounding space. This space is connected with the outside air through a check valve, opening outward in the automatic injectors, and by a valve termed the overflow valve. The injector nozzles are tubes, with ends trumpet mouthed to receive and deliver the fluids with the least possible loss by friction and eddies.

As a thermodynamical machine, the injector is nearly perfect, since all the heat received by it is returned to the boiler, except a very small part which is lost by radiation; consequently its thermal efficiency should be in every case nearly 100 per cent.

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Fig. 513.—See page 252.

Fig. 514.—See page 251.

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All injectors are similar in their operation. They are designed to bring a jet of live steam from the boiler in contact with a jet of water so as to cause it to flow continuously in the direction taken by the steam, the velocity of which it in part assumes, back into the boiler and against its own pressure.

There are three distinct types of live steam injectors, the “simple fixed nozzle,” the “adjustable nozzle,” and the “double.” The first has one steam and one water nozzle which are fixed in position but are so proportioned as to yield good results. There is a steam pressure for every instrument of this type at which it will give a maximum delivery, greater than the maximum delivery for any other steam pressure either higher or lower.

The second type has but one set of nozzles, but they can be so adjusted relative to each other as to produce the best results throughout a long range of action; that is to say, it so adjusts itself that its maximum delivery continually increases with the increase of steam pressure. The third type, double injectors, are those in which the delivery from one injector is made the supply of a second, and they will handle water at a somewhat higher temperature than single ones with fixed nozzles. The double injector makes use of two sets of nozzles, the “lifter” and “forcer.” The lifter draws the water from the reservoir and delivers it to the forcer, which sends it into the boiler. All double injectors have fixed nozzles.

The action of the injector is as follows: Steam being turned on, it rushes with great velocity through the steam nozzle into and through the combining tube. This action causes air to flow from the suction pipe, which is connected to the combining tube, with the result that more or less vacuum is formed, thus inducing a flow of water.

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