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North Metropolitan Sewage Pumping Station
| Name | North Metropolitan Sewage Pumping Station |
| Ortssitz | Boston (Mass.) |
| Straße | Chelsea Stree t600 |
| Art des Unternehmens | Abwasserpumpwerk |
| Anmerkungen | Erbaut in den 1890erm. Behandelte Abwasser aus East Boston und den benachbarten Städten wie Woburn, Arlington, Chelsea, Revere, Cambridge und Somerville. Seit 2002 von der Massachusetts Water Resources Authority (MWRA) auf die "Division of Capital Asset Management" DCAM übertragen. |
| Quellenangaben | [East Boston Preservation Priorities Report, XII.2011, S. 16} |
| Zeit |
Ereignis |
| 1908 |
Das Werk wird bei dem Feuer in Chelsea stark beschädigt |
| Produkt |
ab |
Bem. |
bis |
Bem. |
Kommentar |
| Abwasserförderung |
|
seit den 1890ern |
1989 |
Ende |
|
| ZEIT | 1876 |
| THEMA | Brief an Charles E. Emery (Vors. Unter-Komitee WA Philadelphia) |
| TEXT | CHARLES E. EMERY,Esq., Chairman Sub-Committee of Centennial Commission, American Society of Civil Engineers, No. 4, East 23rd Street, New York.
Dear Sir
My answer to your circular letter asking for information on the subject intrusted to your committee, will not be carefully arranged,as I suppos eyou want only the facts,to be used in your own way and set forthin your own language.I shall endeavor to sketc hmy labors in hydraulic engineering from the very first, hoping thus to set before you their growth from an insignificant beginning to a condition of importance and usefulness. Somewhere about the year 1840, I was engaged in experiments with a steamboat designed for canal navigation. It frequently happened that the boat was suddenly stopped by unexpected impediments in navigation or detention at locks.This often brought a handpump into lively requisition for keeping up the boiler supply,and naturally turned my thoughts toward a labor-saving method. The result was the independent feeding pump, patented on the 7th day of September,1844, and which I will now describe, referringto drawing No. 1 in illustration. It is shown as attached to a boiler, and is a simple form of steam pump, with a single-acting plunger and ordinary conical valves to the pump proper. The steam cylinder is supplied with steam through a pipe, which has a valve at the other end within the boiler. This valve is controlled by a float, whichby its rising or falling supplies more or less steam, and allows the pump to run faster or slower according to the height of the water. I made many of these, and their action was satisfactory to a surprising degree, maintaining an almost absolute uniformity of water level without alteration or adjustment. But it proved to be dangerous, just in proportion as it seemed to be reliable. It would perform its duty so long and so well as to full the attention of the attendant to sleep and almost insure an accident, if per chance someone of the numerous infirmities of machinery should render the apparatus inoperative. It was here I learned to dread and condemn all automatic contrivances for superseding the attention and responsibility of attendants. As applied to boilers I am convinced that they tend to danger. The drawing shows a spring which acts upon the steam valve. Its effectis thus describedand claimed in the patent: "My improvement in the auxiliary engine consists in the manner of rendering the action of the slide valve certain, without its being necessary to depend upon the momentum of the engine therefor. The momentum is frequently insufficient for this purpose, and the valve is then liable to stop in such position as to cover both of the steam ports or openings into the steam cylinder. By my improvement the danger of the stopping of the valve in such a position as to prevent the motion of the engine, is obviated. "The claim of the patent is in these words: "What I claim as new and desire to secure by Letters Patent, is the employment of a spring in combination with the steam valve of an auxiliary engine for supplying a boiler with water, so arranged,substantially as herein described,as to admit of its being properly armed or compressed by the action of the engine upon an intermediate piece or lever, while the steam valvere mains at rest until, at the proper time, by the further motion of the engine,the spring is released and acts to draw said valve independently of the momentum of the engine, in the manner and for the purposes above setforth. "This, so far as I know, was the beginning of that numerous class of following inventions for storing power to act upon the steam valve, when the momentum of the moving parts was insufficient to throw it through its full distance of travel. In the cours eof my experience I made many arrangements for using the spring, other than that exhibited in the patent of 1844. One was the employmentof a tube in place of the valve rod, with a spiral feather acted upon by an arm on the piston, whichin its motion back and forth compressed the spiral spring within the tube. In this case the steam valve instead of working in line with the piston rod, passed in a transverse direction over the openings. For the ordinary arrangements, the B valve, shown in Fig. 3, was invented and used. The step from this spring motion to the use of a small steam piston for driving the valve, was obvious enough,and very soon made. The first and simplest arrangement is shown in drawing No. 2. They have since been constructed in almost every conceivable way. In my first arrangement a rod protruded from the main steam valve as well as from the auxiliary. The object of this was either to compel the full motion of the main steam valve, or else the stoppage of the engine in case the auxiliary piston failed to work promptly. An obvious difficulty resulted from the large size of piston required to hand lean ordinary slide valve. This suggested the balancing of the slide valve, which was accomplished in the way shown in Fig.4, while retaining the general arrangement of the auxiliary piston. In this balanced valve the direction of steam was changed, so as to have it entered at the exhaust port and escape into the steam chest, which was thus converted into an exhaust chest. Plates were fitted over the blocks, or cheek pieces at each end,thus forming a tight cavity or dashpot, where in the steam valve would be brought up by the compression of steam within the cavity. A small valve was so arranged as to be opened at the proper time and destroy the tightness of the dash pot, so that the valve could be withdrawn more readily. In the course of my protracted experience with auxiliary pistons, I adopted numerous arrangements not necessary to exhibit in this narration,involving numerous forms of steam, water, and air dash pots for restraining their motion. I have still in my possession an old steam pumpused on the steamer "Bay State" for some years, commencing in 1849, and afterwards replaced by one of more modern form. I offer a sketch of it in Fig. 5, exhibiting an arbitrary water valve motion, combined with the steam valve,and moving simultaneously therewith. This, while operating as a water dash pot to arrest the motion of the steam valve, also made the movement of the pump valve positive and certain. I have since adopted the same form of valve upon air pumps, notably in the case of the war vessel "Dunderburg". There is much to be said in favor of this arrangement, although for many reasons I am not prepared to advocate its adoption upon ordinary pumps. A fine example of an arbitrary water valve motion was given by Engineer Erastus W. Smith,on the large engines designed by him for the New Orleans Waterworks in 1847. An interesting and efficient modification of the auxiliary valve throw, and which I call the exhaust valve throw, was made the subject of a patent in 1856. It is illustrated in drawing No. 6. The steam valve was constructed in the form of a piston working in a small cylinder constituting the steam chest, the steam being admitted at the center and escaping at either end. A brief extract from the patent will fully explain this modification: "As represented in the drawing, the main pistonhas just completed a stroke from left to right, the steam, admitted through the central opening C, is just on the point of passing to the right hand end of the cylinder through the opening A 1, while the exhaust from the left hand side, already commencing to escape through the port A 2, fills the space D, but from this space or cavity it has no escape until,by its elastic force, it crowds or forces the piston valve A, towards the right, far enough to uncover the opening D 1, which communicates with the escape pipe or condenser. By this time the steam port A 1 of the main cylinder is also open for steam. Thus the necessary motion of the steam valve is produced by the effort of the steam to escape from the small cylinder or valve chest so called. "I should weary you by undertaking to set forth any considerable partof the numerous engines made on the general basis here indicated. I believe almost every change was rung upon a steam valve throw, but in those days the amount of refinement and complication attending their construction and management seemed to be an insuperable bar to their rapid introduction. Upon the smallest provocation the use of a steam pump would be abandoned and the old well-tried arrangements resumed; for no work was fitted up with reference to the exclusive use of a steam pump it was always secondary. Even so good an authority as the late Mr. James P. Allaire nearly reduced me to hopeless inaction, by saying he considered it his duty to tell me that I was trying to invent a machine that was not wanted; that no part of the machinery, either of steamboats or for factory purposes, was moresatisfactory and complete than that for pumping. And this appeared to be the opinion of almost every engineer. Another opinion expressed by a prominent engineer of the day, Mr. Alfred Stillman, of the Novelty Works, was sufficiently discouraging at the time, yet of great value, as compelling me to look still further. He came to my works one day to inspect the last and best arrangement of piston valve throw. After a careful and quiet consideration of the case for a few minutes,instead of the approval which I not only expected but needed, he said: "This is all very well and very ingenious, but, if you expect to bring these things into general use, you must contrive to have a man see something he has seen before in his life, when he takes the cover off from a steam chest. "There was no appeal in those days from the decision of the Novelty Works, and this one might well be called conclusive. I was then working with Mr. Wm. H. Baker, as a partner, and we sat down together to achieve the desideratum of a direct-acting steam pump with a simple ordinary slide valve. This we at last accomplished, and from its discovery may date the real introduction and popularity of a class of machines which now covers the length and breadth of the land. We called it the relief valve motion. It was patented Apri l3d, 1849, in the name of H. R. Worthington and Wm. H. Baker, and afterward extended to H. R. Worthington for seven years,from the 3d of April, 1863, Mr. Baker having died before that time. I here offer you, in drawing No. 7, the original arrangement as presented at the patent office, combined with a pump fitted with radial water valves. Its modifications, preserving the characteristic of relief, have been numerous in my practice. In this arrangement the momentum and expansion of the steam are made to conspire to carry the valve through its full distance in the following manner: "Two opening smay be made into each end of the cylinder, coming together in one as seen in the drawing, Fig. 1, at A A. When the piston moving from right to left arrives, as shown, nearly at the end of the stroke, the resistance is suddenly reduced, for the reason that the piston passes between the two openings and allows the fluid pressed before it to pass, with little or no obstruction, behind it in the direction of the arrow. The resistance being thus suddenly relieved, the momentum of the moving parts and the expansion of the steam in the cylinder acting through the arm B, serves to push the steam valve C with quickness and certainty entirely over the opening. Several ways of thus relieving the resistance will occur to a mechanic. For example, the cutting of longitudinal grooves or recesses in the pump cylinder over which the piston may pass; or connecting the two ends of the pump chamber together by a pipe, in which a cock shall be opened and shut at the proper time by the motion of the engine; or a valve may be put in the piston itself; or when the water valves are so constructed as to be moved by the machine in an arbitrary manner, independent of gravity, this valve may be so made as to allow the water to pass around it. The claim is for thus reducing or removing the resistance and operating the steam valve. "A subsequent patent for a particular way of accomplishing this effect was granted me, July 31st, 1855,the claim being restricted to the described mode. Steam pumps involving this principle were extensively introducedand received with much favor. Their elementary simplicity, facility of repairs by the most inexperienced hands in a word,their exemption from any derangement or trouble tending to produce permanent stoppage, give tem so many points of advantage as to induce me still to offer them for many kinds of service in preference to any other pumping machine I construct. I would now call attention to a principle of construction first adopted in a pump used on board the steamer "Washington" in 1850. Up to that time my practice, and I believe the concurrent practice of the day, was to make a large water valve with considerable lift. A moment's reflection will show that when the motion of a pump changes, the valves are in the wrong relation there to, and must be immediately changed. For an instant of time, therefore,the resistance is suspended much as in the case of a gear suddenly reversed and producing back lash. My idea was, by the employment of a large number of diminutive valves, eachone insignificant, and withbut a small fraction of an inch of lift, but aggregating in an ample water way, to reduce this lost interval and keep the valves nearer to their seats,thus enabling them to get home in less time. The valvea dopted was a plain india-rubber disk, half an inch thick, and working upon a central stem over a series of half-inch holes, with a lift of not over a quarter of an inch. There were nine of these in each chambe rof the Washington pump, making 36 in all. I offer a drawing of this pump with its valve arrangement, not only as marking the time of its introduction,but because it represents my present views in the construction of all pumps designedf or important purposes. (See plate7.) I come next to a point in my experience of great importance, involving new considerations and justifying much greater cost and complication of engineering than any hitherto called for in my business. I refer to the department of waterworks for cities and towns. My first connection with any important enterpris eof this kind was at the city of Savannah, where the second compound condensing engine, under the patent of Worthington and Baker, was erected in the year 1854. There were three in all, arranged to deliver water into a wrought iron tank of 35 feet in diameter, placed upon mason work about 80 feet from the surface of the ground. And let me say that this arrangement seems to be a valuable compromise between the two openings and allows the fluid pressed before it to pass, with little or no obstruction, behind it in the direction of the arrow. The costly storage reservoir. The duplication of the pumps gives reasonable warrant for their uninterrupted performance, and the contents of the elevated tank allows the storage of a night's supply, or for a sufficient quantity to be drawn upon, in case of a sudden fire, without calling upon the pumps. I can say that, for all the years ensuing, no complaints from Savannah have reached me, but on the contrary their order for a much larger pump, given two year sago, when they decided to enlarge their supply, was accompanied by a letter of unqualified commendation of what had hitherto been done. The works were erected under the personal supervision and direction of Mr. James O. Morse, C.E., and in accordance with his designs and plans. A very interesting modification of this idea of tank supply is now being carried into effect by J. D. Cook, Esq., C. E., Constructing Engineer of Sandusky Waterworks. He employs a stand-pipe 25 feet in diameter and 200 feet high.I append a sectional drawingof the engine employed at Savannah. The valve is thrown by relief motion, and the compound cylinders are annular in their arrangement. A single slide valve performs the somewhat complicated function of giving steam to the high pressure piston and of making a communication with the expanding piston on the one side, and with the condenser on the other. This valve is balanced, or rather the superincumbent pressure upon it is reduced by a piston, working in a small cylinder upon its back, and attached by a suspension bar to a permanent point in the dome of the steam chest. (See plate 8.) It will be seen at a glance that this arrangement does not balance the valve in any proper sense of the term, but only suspends as much weight as is received on the area of the piston, which swings back and forth as the valve travels. All the weight thus suspended costs but little in the way of friction, as the motion at the pointof support is scarcely appreciable. I patented this manner of relieving the valve of pressure, in 1856, and have used it ever since upon all my large engines. The arrangement of pump is that before referred to, as first introduced upon the steamship "Washington." It has also been the basis of my subsequent practice, and for the following important reasons: First. It offers large area for the accommodation of the water valves above and below it, and thus allows the use of the numerous small valves befor ereferred to, and which I still continue to use in preference to large valves for the reasonsal ready given. Second. The ample recess which surrounds the plunger constitutes a subsiding chamber into which foreign and hurtful material may settle out of the way of the plunger packing. Third. The constant protrusion of the plunger into the forcing side tends to carry out and away from the packing-joint any foreign substance which would otherwise be forced therein by the pressure, and act to abrade the surfaces. The difference between its actiton in this respeckt and that of an ordinary poston is important. The piston rod tends to run over and hold the particles of dirt or foreign matter that may be in its way, while the plunger tends constantly to eject them. Fourth. This construction makes it easy to renovate the working parts, at short notice, or, within reasonable limits, to change the size of theplungers with no inconvenient delay. The change is accomplished by the withdrawal of the plnnger and packing ring, and the substitution of another. The withdrawn plunger, if it happens to need repairs, can be trued off in a lathe and fitted with a new ring, conveniently and inexpensively. The packing ring is very deep, without elasticity or provision for adjustment; being merely a solid ring carefullyfitted to the plunger. Let it be noticed that engines, of the character we are considering, have little or no momentum to help out the stroke,they therefore will not allow of any inequalities or tight places in the packing. Now, as a cylinder or plunger, always wears fastest at the middle of the stroke, if the packing were adjusted to fit the middle, it would bind enough at the ends to embarrass the motion. I have, moreover, at times detected a tendency in elastic pump packings to collapse upon a plunger, or expand against a cylinder, with such force as to produce much unnecessary friction. After a diversified experience with pump packings, I have concluded, for large and important services, where the water is supposed to be reasonably clear, to depend exclusively upon well-fitted inelastic surfaces, except for glands and outside boxes. Fifth. The deflection of the water currents,or their change of direction, is less in this arrangement of double-acting pump,than in almost any other; notablyless than in the single-acting Cornish Pump. The force valves lie directly above the supply valves, and the water passes from one through the other, only slightly deflected around the plunger. Numerous experiments with gauges show that the losses due to friction through this pump, when working at its proper speed, are practically inappreciable. Sixth. In this arrangement, the valves are unusually accessible, eitherfor repairs or inspection. Seventh. The system of smallsub-divided valves, working over a close grating, forms a strainer in construction, and offers a barrier to the passage of any foreign substance of sufficient size to produce mischief. Eighth. The temporary or permanent interruption of the functions of one, two, or even three valves, although producing irregularity of motion, to a greater or less degree, is not sufficient either to destroy the whole actionof the pump, or all of the resistance to its motion, so that no danger of a breakage is thereby produced. The case is very differentif a large valve happens to fail. Resuming the description of the Savannah Engine, please observe that the exhaust passed through the side shears into a condenser located above the force valves and making part of the force main. All the water delivered by the pumps was thus carried around the condenser or through the pipes with which it was perforated. It thus became a surface condenser and obviated the use of a considerable part of the injection water ordinarily required. The Air Pump is shown attached to the end of the pump, and its construction has a passing interest as being the only horizontal pump I had heard of at the time which could be called efficient or reliable. The principle upon which it acted was the alternate elevation and depression of vertical water columns formed at each end of the pump chamber. As the piston receded from one end, this vertical column followed; while on the driving side it was elevated. The piston, in this arrangement, did not need to be tight,as no aeriform fluid ever touched it. Its leakage was only water from one side to the other. The watercolumns were, in effect,two pistons working with almost absolute tightness. The practical efficiency of the Engine, was due, in no inconsiderable part,to the efficiency of its condensing apparatus. While adverting to condensing apparatus, let me record the fact that, in the year 1850, I furnished a steam pump for raising the water from a deep well at Oatlands, L.I., the estate of De Forest Maurice, Esq. In order to avail of the partial vacuum due to the height of the pump above the supply, the exhaust of the engine was connected to the supply chamber of the pump, thus converting the engine into a condensing one with considerable increase of power, and this I have done several times since, although, as the arrangementis only efficient when applied to pumpsworking on a high supplycolumn, it is not always, nor indeed often, applicable. It is, however, sometimes desirable to get rid of the exhaust steam in a quiet way, as in mines, which would justify the arrangement, even if no increase of power resulted. A duplicate of the Savannah Engine was erected at Cambridge, Mass., in the year 1856. Its dimensions were: High Pressure, Cylinder 12 inches diameter, low pressure cylinder 25 inches, Plunger 14 inches, length of stroke 25 inches. Its contract guarantee was to deliver 300.000 gallons in 24 hours, one hundred feet high. Another of similar size was soon afterwards placed beside it. This Cambridge engine has some importanc eas having been concerned in one of the most important and extensive trials of duty made, up to that time,or perhaps since, in this country. It was conducted by Messrs. C. W. Copelandand, W. E. Worthen, underthe direction of Jas. P. Kirkwood, Esq.,Chief Engineer of the Brooklyn Waterworks. The results were published in 1860, by order of the Brooklyn Water Commissioners,entitled, Reports of Mechanical Engineerson trials of duty made in 1857 and 1859, upon the Brooklyn, Hartford, Belleville, and Cambridge Pumping Engines. The proposals for engines for that city, whil ecalling for those of the Cornish type, stipulated that any other plan of engine might be submitted which would perform the same duty as efficiently and economically, Under this clause the contractors offered to build any other engine selected by the Commissioners, who for their own information, proceeded to make the protracted, thorough, and extensive tests referred to. The Cambridge engine was first tested by Messrs. W. E. Morris and Samuel McElroy, with the result of 70,463,750 pounds duty. A subsequent impeachment of his own reportby Mr. McElroy, led to the appointment of another committee of experts, Messrs. F. Graffand, E. W. Smith, for the testing of the same engine. They reported a duty of 71.278,486 pounds. The results of all the different trials were tabulated in a preface to the main report signed by Mr. James P. Kirkwood, Chief Engineer's Office, Brooklyn, Feb. 1860. To meet his own views, Mr. Kirkwood made some discreet deductions for losses in pumps, etc. These allowances amounted to 5 percent in the case of the Cambridge engine. With these deductions it stood at the head of the list. I present the table for your inspection:
Date of experiment: April,1877;
Name of engine: Worthington Engine,at Cambridge
Duty in foot pounds: 669,411
Date of experiment: June 1877:
Name of engine: Worthington Engine,at Cambridge
Duty in foot pounds: 675.746
Date of experiment: January 1857
Name of engine: Cornis engine at Jersey City
Duty in foot pounds: 628.233
Date of experiment: July 1857
Name of engine: Hartford crank engine
Duty in foot pounds: 646.994
Date of experiment: Juli 1857
Name of engine: Hartford crank engine
Duty in foot pounds: 614.428
Date of experiment: Januray 1860
Name of engine: Brooklyn new rotative engine
Duty in foot pounds: 601.407
Date of experiment: June 1856
Name of engine: Cornish engine, Philadelphia
Duty in foot pounds: 589.908
The result of these duty trials induced teh Water Commissioners of Brookly to nominate my engnine as the one to take in plce of the Cornish engine called for in the contract, the having meanwile agreed to accept the modification of die Cambridge engine, called the Duplex engine which I was just then perfecting an endeavoring to introduce into important works From taht time of its first indtorduktion the progreess of this engine toward ist presend popularity has been steady and rapid. They are now found in more than fifty waterworks stations in this contry and Canada, numbering eigty-seven engines, and aggregating, in a delivering capacity, 275.000,000 gallons per day. It may be said, without fear of contradiction, that they have been successful and well approved. Nothing approaching even an inconvenient stoppage of a water supply has yet been traced to their failure. While trivial breakages, or the necessity for larger or more permanent repairs have occurred, no breakdown or disaster has ever taken place. The nearest approach to anything of the kind was the fracture of a piston, produced by shrinkage in the casting. It followed an attempt to use a new form of box piston, which proved a failure. The remarkable exemption of these engines from the numerous accidents to which ordinary pumping engines are liable, leads to a consideration of the philosophy of their action and cause of this immunity. It soonbecame evident to my mind, that the small engine at Cambridge, economical in the use of coal, and durable as it proved itself, was fully as large as it was desirable to build an engine of its character. The sudden reciprocation produced a jar and recoil, which, while comparatively insignificanton this small engine, threatened to be distressing if not destructive upon a larger one. The problem was plainly indicated. How should a pumping engine be made to reciprocate quietly? A careful consideration of the causes at work, suggested the answer. To think of the difficultyw as almost to find the remedy. It required no large departure from ordinary practice, no great invention, no remarkable exhibition of mechanical skill, to apply it. Very little was to be done, but that little was of vital consequence. Like a leak in the ship, it was a small thing to obviate, but a destroying agent if neglected. Let us for a moment follow a stroke of a double-acting pump piston, from one end of its cylinder to the other one single stroke and no more. Behind it is an open supply valve through which the water is pouring,to meet the demands made by the receding piston. Before it an open force-valve, through whicht he water is pressed by the advancing piston. It reaches the end of its stroke and stops, for we are only dealing with one single stroke. What follows? The water continues to press by its momentum into the chamber, filling every inch of space. As the current gradually ceases, the supply valve gradually and quietly settles to its seat; at the same time the delivery valve falls quietly through the water, which fails to keep it lifted. Both valves are now atrest, having fallen by their gravity through the gradually subsiding currents which tended to open and hold them open, while the chamber behind the piston is thoroughly supplied with water.After this interval of time let us make the return stroke. The piston, met by its full resistance, takes up its work quietly, while the delivery valves before, and the supply valves behind it, open under gradual pressure. We need follow the motion no further to see that the remedy for concussion is rest for the piston at the end of the stroke. Contrast this with the action of a pump compelled to reciprocate in the manner commonto most engines. There the reverse motion takes place so suddenly that the supply and delivery valves of the preceding stroke are caught almost at their highest lift, not having had sufficient time for closing. The water of supply has not been able to fill up behind the rapidly retreating piston, which,as a consequence, meets a vacuous space at the instant of return, with every valve in wrong position. Before one set can be seated and the other lifted, the engine by a sudden jump, strikes the water heavily, and pounds the valves to their seats. Hence the noise, which always has, and always will, to a greater or less degree, mark the self-destructive action of an ordinary reciprocating pump. I claim that it should be accepted a sproved, that the cessation of motion at the end of the stroke, for a length of time sufficient to allow the seating of the valves by gravity, instead of by the action of the return currents, will completely obviate this noisy, imperfect, and injurious action. To this extent,the desideratum is accomplished. Another requisition remains, and that is for uniform,unbroken movement of the water into and through the delivery pipe. The Cornish engine most conspicuously exhibits the bad effects of not fulfilling this requisition. Except for this, it might perhaps still stand upon the eminence it so long occupied, but from which of late years it has been slowly and inevitably descending. As, in the comparison you are now called upon to make,the claims of this celebrat edengine will undoubtedly receive complete attention, allow me to say why I venture to make the declaration that its supremacy as a pumpingengine is by no means undisputed at the presentday, as it was but a few years ago. Within the last ten years, the cases of its adoption as the preferable engine for water works purposes,have been so few as to be scarcely noticeable. And this declaration is true, not only of this country, but for the one of its nativity and development, where formany years, since the time of Watt, whose great geniusas a mechanical philosopher was conspicuously marked upon it, this engine was the exponent of the highest triumphs in the use of steam as a motor, achieving results which, until recently, were considered unattainable in any other department of work,or with any other form of engine. This celebrated engine still has its intelligent advocates, and is, perhaps,unrivaled as yet for deep mine pumping. It originated in this department, and owes many of its mechanical peculiarities to the peculiar demands of this service. Its honors were never qualified until it was transplanted from the home of its usefulness to do duty in a service where the water was to be discharged through a long main to a great height above the pump, and under the requisition of continuous and uniform delivery. This wast he very requirement, which, from its nature,the Cornish engine was unfitted to meet, and a stand-pipe was the outgrowth of this inability. It has proved to be an expensive and in many cases a troublesome expedient for relieving the main of the shocks consequent upon repeated stopping and starting of the column of water. Its alleviating effect was remarkably exhibited at the Jersey City Waterworks, where, without the stand-pipe, the Cornish engine erected there, would only make five strokes per minute, and even that with difficulty; with it, the strokes were increased to eight per minute, and the general running of the engine in every way improved. The Cornish engine is, moreover,an expensive engine. Its movements are verys low, and it has but one effective, for every two working strokes. This brings great enlargement, within creased weight and cost of part sper horse-power. It is, also, a lofty engine, requiring massive beam supports, at a great height from the ground. The arrangement of its pumps entails great depth of foundation; so that it is not unusual to find the cost of the masonwork greater than the cost of the engine itself. And it is a complicated engine. Its valve motion, though beautiful, and expressing the thought and practice almost of a century, is intricate, composed of many parts, and difficult for an ordinary person to adjust, or even to thoroughly understand. The motions are more or less harsh, being of the tappet, or striking character. The principle upon which it operates, at once confirms and explains the declaration that it is a precarious engine. The steam acts, not directly upon the pump, but upon a weight, which, by its descent,is to accomplish the pumping.It is startling to see a weight of eighty or ninety tons lifted ten feet, and then deserted by the steam which upheld it, with nothing to insure its safe descent but the resistance offered by the water within the pump chamber. And safe it will be, so long as all parts of the machine properly perform their functions, for then the mass will be deliberately lowered to the bottom. But not so, in case of fracture,imperfect working of valves, or failure of water supply. Then the unopposed weight descends with velocity, producing effect more or less disastrous. Accidents of the kind indicated, and varying only in severity, are numerously recorded. It is, however, an economical engine, as regards fuel, and herein lies its great renown. Strange to say, however, the peculiarities of construction to which this economy is due, constitute the most important objection to its use as a water works engine. The use of steam under high rates of expansion, obligates the employment of the large mass of metal, before mentioned, which shall receive the excess of pressure and power at the commencement of a stroke, and again communicate it, when, by reason of expansive action, the pressure at the latter part of the stroke becomes feeble. This system of giving and taking, through the agency of inertia and momentum, generates irregularity of motion, which increases as the higher economic values of expansive steam are approached. In the Cornish engine this irregularity is all thrown into the inactive stroke, during which the power is stored in the uplifting weight, whichby its equable and gradual descent, is made to act upon the water column. But these long intervals of inaction are objectionable for several reasons. In an economical point of view, the resulting demand for a stand-pipe and the necessity of employing a very large engine, as compared with its pumping capacity, more than neutralizes the saving of the fuel. With our modern ideas, it seems surprising to read as we do in Pole, Wicksteed, and other authorities, that engines of fifty inches in diameter and nine feet stroke were tested for highduty when exhibiting a power of only twenty-six and one-half horses. The celebrated Fowey Consols engine, whose record is still quoted as conclusive and almost unapproachable, with a cylinder of eighty inches diameter, and a stroke of ten and one-half feet, was only exhibiting sixty-two horse-power, when accomplishing its remarkable duty. A glance at the condition of this engine in the mines where it originated, will explain the otherwise unaccountable fact that a pumping engine without a rival in one place, has an equivocal or failing reputation in another. "At the mines the engine is located at the surface, near to the shaft, down which the long rods, connectingt he steam cylinder to the pumps, are carried sometimes to a depth of 2.000 feet. The necessary weight involved in this connection, becomes a natural part of the engine as weight to be raised, and the lift is divided into several intermediate ones of comparatively insignificant height. This subdivision almost completely protects the engine against disastrous failure of resistance. The water is also delivered at the surface with no forcing main, and no demand for uniform flow. The engines are inordinately large for the work, making a casual stroke now and then, as demanded by the flow of water into the mine. Their history is not only that of a good engine, but of one of the very best adaptations ever made to a peculiar requirement. Their record of "duty," as it is technically called,high, as it properly should be, has, without doubt, been the frequent subject of error or exaggeration; at any rate, the engines built here (and nobody will claim that they have not been most carefully designed and constructed), have not yet reached a duty of seventy-five millions in any well authenticated trial. In 1837, Mr. Wicksteed decided to transplant a Cornish mine engine to the East London Water Works. It was started in 1838, and the results are thus recorded by Mr. Wicksteed: "The engine worked very satisfactorily, a great saving in fuel being immediately effected. The pump-valves, however, being of extraordinary dimensions, caused so great a blow upon closing, that the concussion shook the whole of the engine house. Several valves, variously modified, but similar in principal to those in use in the Cornish mines, were made at grea texpense to the contractors, but without remedying the defect. At last, however, Messrs. Harvey & West invented the self-acting double-beat valves, which were made and set to work in July, 1839; the blow caused by the shutting of these valves is so muchless than that caused by the former ones, that there is no necessity of the admission of any air under them, no loss of water through them, and consequently a great saving by the use of them."One of Mr. Wicksteed's tests was of the Holmsbush engine, which I give in his own words:. "The diameter of the cylinde rwas fifty inches,and of the pump eleven inches, lifting water 535,5 feet. The chief points wo which my attention was directed, were the quantity of coal consumed, and the actual quantity of water lifted. I saw ninety-four pounds (a Cornish bushel of coals) weighed and had the stoke-hole cleared, and the coal bins and stoke-hole doors sealed. In addition to these precautions, beside my own observations, I had one of my young men stationed in the boiler house duringt he trial; so that I am quite satisfied that not more than ninety-four pounds were used. At the end oftwo and one-quarter hours, the ninety-four pounds of coal having been consumed,the engine was stopped, and the counter again taken. It had made 622 strokes. The weight multiplied by the height in feet, is equal to 102.721.322 pounds of water, lifted one foot high with ninety-four pounds of coal. The result, however, does not show the duty of the engine which would be 117.906.992 pounds (equal to 125.500.000, by American standard of 100 pounds of coal). "The honest way in which the precautions taken to guard that "ninety-four pounds of coals,"are set before the reader, and the deduction of an unparalleled duty from an experiment of two and one-quarter hours duration,with a fifty-inch cylinder, eight foot stroke, exhibiting only twenty-three horses power, would be amusing, had it not introduced false conclusions, which, even to this day, are not eradicated. The trial of a steam ship for a quarter of a mile, to prove speed and boiler capacity, would be sensible, as compared to the foregoing.It is but just to Mr. Wicksteed to say, that in the year 1861, he candidly admitted the impropriety of his conclusions, in the following words: "When I first undertook these experiments, I imagined that several trials of short duration would answer the purpose, but I soon found that nor eliance whatever could be placed upon them. "Again he says " When a mining engine is first erected, the load to be lifted is very trifling in proportion to the capabilities of the engine, and consequently, the steam may be cut off, even at one-tenth of the whole stroke, as I am informed has been the case. In some instances, under such circumstances, the duty performed by the engine would be very great. The obvious reasons for the falling off of the large duties after some years working of the engine, is not that the engine itself has deteriorated, but that its actual power, when working so very expansively, is so small in proportion to the size, that the interest upon the outlay and cost of working, and increased number of engines that would be required to preserve the same rate of duty, would counterbalance, if not far exceed, the value in the saving of fuel. It must be remembered that the trials made at Holmsbush, and with the Fowey Consols, were upon engines that had not been long erected, and where the load to be lifted was light, in proportion to the size of the engine. "Without pursuing the question of Cornish duty, through its almost interminable statements and counter-statements, it may very safely be assumed that Water works practice with the engine in this country, has been as good as it ever has been, or can be, any where else. This celebrated engine is fully befor ethe world for its final opinion. It can expect little or nothing from future inventors. If its practical status were equal to its theoretical one, its preeminence would still stand undisputed; but when it is reduced to reasonable dimensions, its advantages, in point of economy, aren ot great, and there is, therefore but little to compensate for its dangerous tendencies. No one stroke can with certainty, be relied upon to be the same as its predecessor. It may be short and waste steam, or over-long and make injurious contact. The arrangement of ponderons buffer-beams to catch the engine when it overruns; the Engineer's hand constantly upon the throttle, his eye following the motion with incessant vigilance; and the significant admonition, "no conversation allowed with the Engineer," speak plainly of conditions too precarious for the Water work sof the present day. It is not to be wondered at, that these manifestationson the part of the Cornish engine induced numerous attempts to produce an engine, which, while emulating its economy, would be positive in its motions, and safe in its character. The crank and fly-wheel engine,the first and most obvious alternative, may be said to stand today as the most acceptable one in the minds of a large number of experienced engineers. It is therefore in contrast and competition with this form that I think the claims of the Worthington engine are to be compared. Let us briefly notice one or two intermediate attempts in this country to construct new forms of pumping engines, which had their short day and speedy condemnation. The Cornish Bull engine, applied to the Buffalo Waterworks, in the year 1850, was arranged with the cylinder directly over the pumps, working without the intervention of a beam, and possessing the defects of its prototype, with a good many additional ones peculiar to itself. It would be hard to find a recent example of this engine. In the year 1856, Messrs. Dickerson & Sickles erected a very peculiar and ingenious engine, at the Hartford Waterworks. It was a crank engine, with single cylinder, cutting off at about one-twelfth of the stroke, and with four sets of pumps, two in each set, driven by cams so arranged as to equalize the natural irregularity of the crank motion, and produce a steady delivery of water, such as might be expected from a rotary pump. It was described as follows: "The engine was a crank and beam condensing engine, cylinder thirty-two and three-eighth inches diameter; strokefive feet, with Wright's patentad justable cut-off; fly-wheel twenty-two feet in diameter and unusually heavy. The power was communicated through a pinionon the crank-shaft, engaging with a spur-wheel on either side of it. On each spur-wheel shaft were two cams: each cam gave motionto a set of pumps, by means of bell-cranks; each set of pumps was composed of two pistons,or boxes,in one chamber,or cylinder, one above the other, and moving independently of each other. The piston rod of the lower box passed through the upper piston rod, which was made tubular. By the cam motion they were so contrived that each piston commenced before the other had completed its motion. They commenced the stroke slowly, increasing to the uniform velocity, and then decreased for a little distance before stopping. "This was a very ingenious, and at the same time a very hopeful and interesting attempt to rectify the inequality of a crank motion as applied to pumping. Here were eight water pistons distributed through the circle of rotation, and acted upon by cams of peculiar shapes, in a manner that seemed almost sure of producing the desired result. That it did not, may be attributed in part to the fact that the high rate of expansion used in a single cylinder, produced a greater irregularity than could be subsequently correctedy any mechanical subdivision, and adjustment of the total resistance. The indicator card shows at once the satisfactory character of the cut-off gear, and the high rate of expansion. Practically, the action upon the water column proved to be percussive and irregular, making it difficult to connect it with an unthrottled gauge or indicator. The duty of this engine was not by any means as high as the advocates of great expansion expected. It stands in the record at 55.000,000 and 62.661.000,the power exerted upon the steam piston being 67.171.000 and 71.889.000. This engine was never duplicated, but a modification of it was built for Detroit, in the year 1857; Messrs. Dickerson & Sickles beingt he contractors. Their offers werebased on the trial at Hartford, the same kind of pumps beingemployed in both cases. The arrangement of steam cylinders was, however, very different. The duty guaranteed was 100.000.000. Considering this an extraordinary proposition, the Board authorized their Chief Engineer, Mr. Jacob Houghton, to visit Hartford and such other places as might be necessary, to obtain reliable data of different pumping engines. His report was unfavorable to the Hartford engine, but Mr. Dickerson reviewed this communication, claiming "that by the use of his pump the water could be raised in a continuous current in one direction, with uniform and equal velocity, to great heights, and through long mains,without the use of stand-pipes or air vessels, there being no concussion,and less friction,than with any other pump. "I quote this to show that already the battle was begun for the true principle of pumping. They finally got the contract, which resulted in an utter commercial if not an engineering failure; a complete condemnation and abandonment of the engine, and a suit at law against the contractors. I must go back somewhat in my dates to state that in the year 1847, Erastus W. Smith, Esq.,then Superintendent of the Allaire Works of New York, designed an engine for the New Orleans Waterworks, involving the very important and unusual modification of arbitrary motion to the valves in the pump. The engine was erected and performed successfully. In the year 1861, a non-rotating pumping engine of unusual size, having a capacity of 800.000 gallons per hour against a head of 170 feet, was erected at the Cincinnati Waterworks, from the design of Mr. George Shields, Chief Engineer in charge. This engine was very bold in its designs, and, as it proved, uncertain, if not dangerous in its operation.It is yet in its place, most imposing piece of enginery, and finished in the highest style. Many improvements have been made since its erection, which make it tolerably serviceable. But it has proved enormously expensive, not capable of high duty, and liable to accidents. It has never been repeated or even imitated. Another almost startling plan of pumping engine was tried in Brooklyn, at the commencement of their Waterworks, about the year 1857. The Board proceeded circumspectly in making selection of an engine,and if they did not succeed in getting even a tolerably good one, as they certainly did not, it should be taken as proof that even, so few years ago, the subject was still undeveloped, and the minds of Engineer sat fault as to the merits of that kind of machinery. This is an instructive incident and worthy of som eelaboration. Some reference has been made to the doings of this Brooklyn Board in my remarks about the Cambridge engine. As there instated,their contractors began under a contract to furnish the Cornish engine, which, up to that time, was the standard object of preference for all important works, with scarcely a dissenting voice. But, before reaching the end of the work, the Board consented to the adoption of some other engine, if, after investigation, they could find one which they would be willing to accept in placeof the Cornish. This produced the celebrated trials made in 1857, onthe Cornish, Belleville, Hartford, and other engines before referred to, an dpublished in reports on pumping engines, 1858 and 1859. It happened, however, that the contractors were able to carry their point,despite the conclusions of the commissioners, and furnished the engine known as the Brooklyn direct-acting pumping engine. Its paternity was neve rexactly decided, but this pointis of small consequence as it did not prove a child to be proud of. Its dimensions will be found in the aforesaid report with a plate showing its construction. Considering its pretensions, and the time, care, and money bestowed so lavishly upon it, no engine could have failed more completely than did this one. If it involved any idea, it was that of endeavoring to make a double-acting Cornish engine. In fact it was frequently thus styled by its advocates. The bare statement is so absurd as to require no comments. As might have been foreseen, the steam not having adequate weight interposed between it and the pumps, as in the Cornish or fly-wheel engines, for storing and distributing energy, could not be worked expansively to any extent. One of the make-shifts was the interposition of a diaphragm below the air-chamber for producing an increase of the resistance, but, as the fallacy of creating work in order to overcome it was soon manifest,the diaphragm was abandoned, and a vibrating quadrantal arc of a fly-wheel was appended to the engine. After two or three years' experience and fruitless experiment, the Board put in still another engine, of almost the same kind and size, and at last they contracted for a vertical crank and beam engine, which was erected by Messrs. Hubbard & Whittaker, in the year 1869, and has since proved itself a first-class engine in all respects. The Board then altered one of the two direct engines, by attaching it to a crank and fly-wheel, and with greatly improved results. The other may still be seen in its original shape. We have now glanced at the more prominent experimental engines which have been tried and found wanting. So uniform was the failure of all attempts to introduce a new type of pumping engine, that it became almost a proverb that a pumping engine was a machine without a duplicate. During this period of costly experiments and signal failures, the city of Philadelphia, which might be styled the home of American Hydraulics, alone kept the even tenor of her way, moderate, conservative, and safe in her practice, with but few exceptions, the most prominent one being a pair of Bull-Cornish engines similar to those in use at Buffalo, which were always troublesome and unsatisfactory. While their arrangements at Fairmount for the use of water-power had been gradually brought to a satisfactory point of efficiency, their extensive steam practice at the four or five different stations, was distributed among Cornish engines and different formsf crankand fly-wheel engines. Their present equipment comprises a double cylinder compound engine; a side lever Cornish engine; and old style Cornish engine; a high pressure engine; another Cornish engine at Roxborough; a crank engine at Chestnut Hill; and six Worthington engines. Let us return now to consider what may be called the more recent developments in pumping machinery, consisting mainly of compound engines under various modified forms. From this classification, however, the novel and interesting engine, constructed by George H. Corliss, Esq., for the highservice work sat Providence, should be excluded. In his arrangement no less than five steam cylinders surround a single central crank, upon which they act in concert through radial connecting rods, no fly-wheel being used. It exerts a steady, propulsive energy upon the water, with capacity to run at remarkably slow speeds. As it is required to deliver water directly into the mains, in quantity to suit the varying demands of the consumption, this peculiarity becomes important. The engine was subjected to public test on the question of fulfillment of contract, the decision being in favor of Mr. Corliss. The duty exhibited was unusually low, but on this point it has been properly claimed by Mr. Corliss that no engine capable at steady work of elevating five millions of gallons, can be expected to stand idle for a good part of the time, now running and now stopping, as the casual demands of a direct service may require, without losing so much by radiation and in other ways, as to put economic results out of the question in comparison with reservoir service. Yet with all respect for the great reputation and successful practice of Mr. Corliss, I venture to say that the engine in question presents an inordinate amount of frictional, leaking, and radiating surface, compared to the power exhibited. Its great beauty and interesting character of movement, make it, however, well worth inspection. Returning to compound engines, we find the first most important example thereof erected at the Schuylkill Works, Philadelphia,in the year 1872, from designs by Frederic Graff, Esq., Chief Engineer of Water Department. This gentleman had visited the English and other principal pumping works on the continent, and this engine expressed the result of his investigation.It merits particular description, as beingt he first American example of the class of compound engines, which have lately attracted much notice for having achieved a very high rate of duty. They were first erected by Messrs. Simpson & Co., of the Grosvenor Works, Pimlico, England, at the Bristol and Richmond Waterworksin 1848, and have since been occasionally repeated, both in England and in this country. They may be considered the most prominent, if not the standard pumping engine of the present day. It is not necessary to describe the general arrangement for using steam expansively in two cylinders. More particular description of the pump may be desirable. It is now well-known under the nameof the Thames-Ditton pump, at which pumping station they were erected by Messrs. Simpson & Co. They may be called bucket and plunger pumps; single-acting as regards the supply side, but double-actingon the delivery. This last effect is producedby the displacement of the pole or plunger, which on the downstroke enters the chamber and displaces its bulk. The chamber is therefore supplied intermittently, but delivers continuously. A comparison of the frictional surface in this pump as compared to its capacity, will be to its disadvantage, for it may be said that the frictionis that of a double-acting pump, while the action is that of a single one, in as much as it only delivers the contents of the pump chamber once in a revolution. This intermission in the flow of the supply is undoubtedly a hurtful characteristic. The introduction of the pole or plunger is a valuable correction of the same trouble which otherwise would occur in its delivery. On one side it secures,as closely as can be done with a crank engine, the uniform flow of water which the case demands, but on the other, it is entirely intermittent. This may be one reason for the imperfection of their performance, as regards smoothness and sweetness of motion. The first of the kind erected in this country at Spring Garden Waterworks, Philadelphia, has always been objectionable on this account. More recently a very fine engine of the kind has been erected at Lowell, Mass. Apart from the massiveness and thoroughness of this engine in designand construction,it does not depart noticeably from precedent. It was tested by a board of experts,and was credited with a duty of 93.000.000. It has since been in regular performance, exhibiting a total yearly duty, according to report of the Board of Water Commisioners, of 72.935.000. In the year 1873, a modification of this engine was erected at the town of Lynn, Mass., under the patent of E. D. Leavitt, Jr., which, in its theoretical condition,is nearly the same, but conspicuously different in its mechanical arrangements. The steam cylinders are brought close together at the lower end, and inclined at the properangle for attachment to the working beam on each side of its center. This arrangement is considered, by the inventor, to distribute the steam, upon the moving parts, to better advantage. He also claims,as the result of the peculiar arrangement of the steam cylinders, a shortening of the passage between the high and low pressure cylinder which deems of much advantage. Im view, however of the practice with tanks placed intermediately between these two cylinders it may be doubted, wehther this ist, in all respects as great an advantage as it has heretofore been considered. Before adverting to the performance of this class of engines, a word as to the value of results obtained by special duty trials, as offering a basis of comparison between engines of the present and past times, may not be misplaced. A special duty trial has lost much of its value. At the best, they have been more or less unreliable, either from the difficulty of getting accurate results or from the possibility of distorting them. To illustrate this we may advert again to Mr. Wicksteed's celebrated trial of the Cornish engine, only lasting hours,with the consumption of ninety-four pounds. But the resulting duty of 118.000.000 bids fair to endure indefinitely in the minds of men as a reliable result, for it is not unfrequently quoted at this day.
The growing importance of this subject makes it of imminent necessity that some standard rule should be adopted for trials of this kind, which might also be applied as corrections to cases already upon the record; thus producing fair comparison between one engine and another, or between the results of the same engine at different times. Superadded to this there should be some agreement as to the way in which the yearly records of a waterworks engine are to be kept, so that a simple tabular statement of annual results would immediately declare the true state of the case without the numerous deductions and allowances at present required. Returning, after this digression, to the duty of the compound crank engines, we would state that the engine sat Lynn and Lowell have an exceptionally high record, perhaps equal, if not superior to that made in England. The English engines at Stoke Newington, were first credited with a duty of 113.000.000 on 112 pounds of coal, and several other similar highduties are on the English records. The Lynn engine stands credited with a special duty of 103.000.000 on 100 pounds of coal, and with a current annual duty of more than 75.000.000. The claims, therefore, that I hope to establish upon your attention,for the invention and introduction of a pumping engine entitled to a permanent placea nd value, seem to be narrowed down to a comparison with those of the compound crank engine in someone of its modified forms, on the points of first cost, economy of operation, few repairs, simplicity of construction, durability, and exemption from serious accidents, and character and cost of buildings required. I appeal to the record as being unequivocally in favor of my engine. As yet, I have neither achieved so high a trial duty nor so good a yearly result in point of mere coal consumed, as have been credited to the compound crank engines. Let me now, however, entermy objection to the expert trials at Lynn and Lowell, not as materially bearing upon my argument, which I prefer to base upon the established results of years; but as not being consonent with the ordinary rules of a duty trial, and therefore unjust to all concerned. I will not stop to say how much this departure from established rules alters the result; suffice it to say, the reports should not be taken as standard,and for the following reasons: First. The resistance against the pumps was not estimated according to the usual rule, proved by the fact that the pressure allowed, was superior to the total indication of the watercard. This is corroborated by the fact that the allowance for friction of water in the main exceeds all precedent. Second. The coal was selected and picked over by hand, thus reducing the percentage of refuse at least six per cent, lower than that contained in ordinary merchantable coal, such as is used on other duty trials. Third. An amount of air was admitted into the pump chambers, which could not in the nature of the case be properly allowed for, and which might or might not have been constant in quantity.Fourth. The steam taken (at Lynn) for driving the steampump which fed the boilers, was not charged to the experiment. There are other questionable circumstances attending the trial at Lynn, and, by implication,that at Lowell (although the particulars of this last have not been made public), as the same parties superintended both trials, and have stated that they were both conducted on the same basis. A recent careful investigator, Mr. Theron Skeel, has published a communication (see Engineering and Mining Journal,March 11, 1876), in which he has undertaken to show the effect of these false allowances upon the duty, which,by his calculation, is reducedfrom 103.000.000, as rendered by the experts, to 87.500.000. I have long been convinced that the only way to eliminate the errors which seem unavoidably to creep into short duty trials, is to get long average records. More over,it is necessary to include in the charge against the engine, every pound of fuel used at the engine house, whether for heating, kindling, banking, firing, orrunning, either the principal engineer its auxiliary, in order to cut off every opportunity or temptation for improper divisions under different heads. This way of estimating performance has the advantage of mercantile value, as it takes notice of elements of gain or loss which a short duty trial does not involve. As the comparative value of different forms of engines, in a commercial and practical view, is the object of all our investigations, allow me to set forth my views as to the proper way of making such comparison. The question of interest in cost is one of paramount importance, and yet most strangely neglected. To put the case in plain phrase, a dollar and one-half in interest is often spent in endeavoring to save a dollar's worth of fuel. As my engines do not aspire to extraordinary duties, I am much interested in having this part of the subjectvery thoroughly presented. It is not unusual for me in some cases to advise the use of a plain high-pressure engine in preference to a more expensive and refined form, simply because the saving in fuel will not compensate for amount of interest on extra investment. It would be startling to present the frequent contraventions of this rule of good sense,in some of the most important Waterworks constructions in this country. Will a better time ever come for the presentation of this question to the minds of the public than is offered by the Centennial Exposition? May we not hope to reach, through your candid, thorough consideration, rules for estimate and comparison which no engineer can afford either to gainsay or disregard? The result of my special and protracted experience presents no point of more importance. The promulgation and adoption by the Society of American Engineers of plain, practical views on this subject, would in my opinion do much to reform and perfect our practice. The time must be nearly at end when we are to be allowed to build monuments of ingenuity or engineering skill without regard to the cost of investment. With this preamble, which I make in the earnest hope of commanding your attention, I would offer one or two cardinal principles underlying the calculation. For illustration, let us take the case of two engines of equal size, one exhibiting an annual duty of seventy millions, the other of fifty. Their working capacity, five million gallons each, in twenty-four hours, against a working head of 200 feet. The amount of fuel used, is the first point to be considered; and we assume that all other expenses of running, attendance, etc., are the same, and that the boilers have equal evaporative value. If we look at records it will appear that, for sundry practical reasons, no well appointed Waterworks relies upon an engine for more than forty percent of its capacity, a duplicate being needed before that point is reached. Admitting this, the saving of coal is to be calculated, not upon five millions per day, but upon a delivery commencing with perhaps one million per day and terminating with forty per cent of the maximum, or two millions. This somewhat unusual view receive sunbroken corroboration from the records. It obviously qualifies the calculation in a very important manner. Again, there is a large percentage of inevitable, loss in the managementof any Waterworks pumping station liberally organized and provided to meet contingencies. The engines cannot be moving all the time, nor at best speeds. This percentage of loss cannot be saved by adopting a more economical form of engine. Let me illustrate this by one or two examples afforded by the careful records of the celebrated engines at Lynn and Lowell. At Lynn, with a capacity of 5.000.000 of gallons in twenty-four hours, the engine in the third year of its existence, was called upon to pump an average of 1.307.000 gallons per day. It ran 190 days, at an average of 11,5 hours sper day, with a total consumption of 789.820 pounds of coal; of this 184.500 pounds,or 23,36%, was inevitably lost in firing and banking, thus reducing the duty which the engine would have claimed on a special duty trial, 26.220.000,or from 112.250.000 to 86.000.000. In 1875, at Lowell, 273.062 pounds were consumed in firing and banking, out of a total of 864.860,or 31 per cent.This is also a 5.000.000 engine, running nine hours per day for 275 days, an average of 1.220.000 gallons per day. This engine was started about four years ago.But we need not expatiate on the patent fact that the saving due to higher duty is to be made on the amount of coal utilized in pumping, and not on the gross amount consumed. We will now go a step further. Our 70.000.000 engine cost us 60.000,00, and our 50.000,000enginecost us 40.000,00, both erected with everything furnished and ready to run. We have therefore an extra investment of 20.000,00 to be justified by the saving in fuel. And now comes the important question of percentage of interest to be charged on this extra investment. Much discussion has arisen on this point, and I beg to present it in the most conclusive form which occurs to my mind. Suppose that, being about to build a pumping engine for your own use, you apply to a capitalist for a loan of the necessary money. He asks upon what security, and you offer him the boilers and engine. He asks if you will keep them in repair, and you tell him that he is expected to pay for repairs himself. He asks you if you will give him guarantee against accident to engine and boilers. You answer, No. He asks how long you will want the money, and you answer for as long as the engine is useful to you. He asks if, at the end of that time, he is to pay himself out of what he can find remaining,and you tell him that he is. He asks if, during its lifetime,the engine may not be superseded by improved forms which will put it out of date, and reduce its value, and you say it is possible. He asks if this may not happen within ten or fifteen years, and you say, that, judging from experience, you think it may. With the sequestions and answers before us, it does not need much financial skill to say at once that six per cent will not produce the loan, although some recent important calculations in this direction have been based upon it. Now let us try to approximate to a fair rate for a loan made on such terms, assuming six per cent as the yearly valueo f money loaned upon good security. Take first, a percentage to cover such repairs as may be necessary for maintaining the engine in good working condition. I have been in the habit of taking this at four per cent per annum, as the lowest assessment that will suffice, when distributed through the lifetime of an engine, before the expiration of which new boilers will be required, as also large engine repairs amounting almost to renewals. And even this proceeds on the hazardous assumption that no accident will occur meanwhile to either engine or boilers. If the risk of such accidents were to be taken fairly into account, I believe that for the majority of engine sat least two per cent should be added to the above. Let us, however, retain the rate of four cent and escape cavil. It is plain that, in addition to this, a sinking or renewal fund must be established, which,when added to the value of the old machinery at the end of its usefulness, shall equal the original amount invested. Without arguing for its absolute correctness, I suggest thirty years as a liberal lifetime for machinery of this class, and doubt if the lender could calculate upon finding more than fifteen per cent of original value at the end of that time. Thirty years would equal three and three-tenths per cent per year. Deduct the fifteen per cent as the value of material remaining, and this percentage will be reduced to two and eight-tenths,or say three per cent. To sum up, therefore, we have 6 + 4 + 3 = 13 per cent as the lowest rate of interest to be charged on money invested in such property. Returning to the case supposed, and making a summary on the preceding bases,we have, 2 Engines delivering 2.000.000 of gallon sper day to a height of 200 feet, one showing an annual rate of duty of 70.000.000, and using 870 tons of coal per year; the other showing 50.000.000 and using 1.218 tons. This saving of 348 tons of coal is all we have to compensate for an annual expenditure of 2.600on extra investment. In many cases, however,the bare allowance of simple interest is sufficient to carry the argument,as shown by the following prominent illustrations: Under the date of January 1, 1876,the annual reportof the city of Lynn Water Board published the following statement of total fuel used and water delivered by the Leavitt Compound Engine during the year 1875: 715.650 pounds coal for pumping. 5,75 cords = 11,500 pounds wood for kindling, 64,168 pounds coal for heating = 791.318 pounds total, delivering 458.249.741 gallons to an average height of 164.485 feet. This equals a total yearly duty of 79.428.000. Let us suppose a Worthington Engine to be doing the same work and exhibiting a total yearly duty of fifty-eight millions, which is not in excess of its well authenticated performances. At fifty-eight millions duty, the above amount of utilized coal would beincreased from 715.650 to 980.000 pounds, or 132 net tons. At 7,2 per ton, the price paid,this would have cost the works 957, which only justifies an investment of 13.680,at seven per cent interest. We will now apply the same calculation to the Compound Engine at Lowell, using their report, dated 1876,in which the engine is charged with 864.860 pounds of fuel, delivering 445.017,090 gallons to an average heightof 163,14 feet, which equals a total yearly duty of 70.015.801. At fifty-eight millions duty, the amount of utilized coal, by which I mean the proportion of total coal used for pumping only,would be increased from 556.625 to 671.903 pounds, equal to 57,5 tons. This,at 7,8 per ton, the price paid, would equal 449,38 per year,justifying an investment of 6.418,at seven per cent. The Lowell Engine was delivering an average of 1,3 [?] millions gallons per day, the Lynn 1,33 million. Their capacity is five millions,so that the assumption of forty per cent is not quite realized, but it is near enough for corroborative testimony in any case where the differences are so large as in the present. The Cornish Engine need not be brought into the calculation, for they early records at the Jersey City Waterworks,where the comparisonis most thoroughly and accurately made between the two engines, on the same service,show the Worthington Engine achieving a total duty of fifty-six millions in one year and sixty millions in another, as against forty-six and forty-four of the Cornish. An examination of the numerous annual records will show, that it is as easy for the Worthington Engine to attain an average annual duty of sixty millions, as for the crank engines above mentioned to exhibit the duties for which their reports give them credit. We have the facts therefore before us, and can easily make the required comparison. It is known that the extra cost of either one of those engines was much more than the above calculations warrant, and here I leave the subject to your decision.I have endeavored to touch upon every point upon which I depend to prove that I have made an important, radical, and permanent improvement in the hydraulic machinery, upon which towns and cities depend for their water supply. If the question were only to decide between a durable and reliable engine, or one of opposite characteristics, it would be without doubt speedily answered in favor of the first-named engine, regardless of relative cost. On these points, I trust I have shown that the engine which bear smy name has taken and maintained the highest ground,and unless the calculations which I have offered as to cost of investmen tbe impeached, I may claim to have further shown that the engine is also superior in point of economy, commercially and practically considered. In addition, the size and cost of the requisite building sare reduced at least twenty-five per cent, and the cost of foundations in much larger proportion. The necessity for stand-pipes, or similarprovision for softening the shock, is obviated. In a word, I am able to point to a record of almost unqualified success in the performance of more than seventy large and important Waterworks stations, unbroken by disaster or change. No Waterworks engine of mine has yet been superseded by one of another form of construction, either for fault, or by the demand for increased supply. I therefore respectfully ask that my case may be considered with care and candor, hoping that you will substantiate my claim to the high honor of having originated a pumping engine worthy to be mentioned as constituting a part of American progress in this most useful and arduous department of mechanical engineering.
HENRYR. WORTHINGTON, 239 Broadway, New York. |
| QUELLE | [Worthington steam pumping engine (1876)] |
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