S&B NOTES ON THE PUMPS, 086665 — * $M ^ ■' EDWARD C, R, MARKS, GJnraeU Inittcraity iCihrani 3tliara, Jfew Bnrk THE LIBRARY OF EMIL KUICHLING, C. E. ROCHESTER. NEW YORK THE GIFT OF SARAH L. KUICHLING 1919 Cornell University Library TJ 900.M34 Notes on the construction and working of 3 1924 004 980 094 a Cornell University sj Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924004980094 NOTES ON THE CONSTRUCTION and WORKING OF PUMPS. EDWARD C. R. MARKS, Associate Member of the Institution of Civil Engineers, Member of the Institution of Mechanical Engineers, Fellow of the Chartered Institute of Patent Agents ; Author of "Notes on the Construction of Cranes and Lifting Machinery,''' "Mecfuinical Engineering Materials," "The Manufacture of Iron and Steel Tubes," " The Evolution of Modern Smalt Arms and Ammunition." PRICE THREE SHILLINGS AND SIXPENCE NET. 1902. THE TECHNICAL PUBLISHING COMPANY LIMITED, 31, Whitwoeth Street, Manchester. JOHN HEYWOOD, 29 and 30, Shoe Lane, London; and Ridgefielp, Manchester. And all Booksellers. D. VAN NOSTRAND COMPANY, PREFACE. The Author has written the series of articles, now presented in book form, for users rather than for makers and students of pumping machinery. He has therefore considered the leading types of pumps and pumping engines as users receive them, or should receive them — i.e., in the finished state. But such particulars are given concerning construction anil capabilities, and as far as possible of results actually obtained, as will, it is hoped, be of assistance to engineers, manu- facturers and others, in the difficult task of making the best selection for their service from the many proposals they may have before them. The earlier chapters deal with matters common to all pumps, such as the conditions affecting the limit of suction lift, piston or plunger speeds, air vessels, pipes and other connections, and with types of valves, packings, and other details. The author desires to thank the various makers who have kindly supplied blocks, particulars as to tests, or other information concerning their machinery. E. C. II. M. 1.3, Temple Street, Birtnnvjltam, May 1st, 1002. V N T E N T S CHAPTER I. PAGE Introduction— Height of Suction and the Energy required to raise Water from a Lower to a Higher Level— Necessity for Vacuum or Suction Chamber— Limit of Suction Lift— The Effect of Air in a Pump Chamber. 1-8 CHAPTER II. Piston or Plunger Speeds— Pipe Areas— Examples uf Pipe Sizes— Air Vessels — Types of Air Vessels 9-16 CHAPTER III. Arrangement of Pipes and Connections -Position of the Vacuum Chamber — Strainer, Foot Valve and Charging Connections for Suction Pipe — Bell-mouth for Suction Pipe and Nozzle for Delivery Pipe 16-21 CHAPTER IV. Plungers and Plunder Packing— Ram Pumps and Piston Pattern Pumps and their Inherent Advantages aod Disadvantages — Packing for each Pattern— Types of Valves for Pump Chambers— Mechanically- operated Valves— The Riedler System 21-29 CHAPTER V.— Bl.ii.er Feed Pumps. The Selection of a Feed Pump— Ratio between Steam and Water Fistnns — Compound Feed Pumps— Steam Consumption 29-3S CHAPTER VI.— Types or Eoiler Feed Pumps. Flywheel Pumps— Non-Flywheel Pumps— Duplex Pumps— Worth in g- ton Pumps — Mumford and Anthony's Patent Duplex —Mum-ford's " Favourite"— Mumford's Cameron Type— Weir's Single Pumps— Results of Tests of a Weir Pump— The Pulsometcr Compound Feed Pump— Bailey- Davidson Pumps— Worthington Admiralty Pattern — Pcarn's Ram Pumps —Ream's Patent System of Packing— Green's Ram Pumps— Results of Tests of Green's Ram Pumps 3ti-5S VI. CONTENTS. PAG E CHAPTER VII.— Mine Pumps. Early Mine; Pumps — Duty of .Mine Pumps— Particulars concerning the Duty of Ancient and Modern Pumping Engines— Types of Mine Pumps— Pearn's Compound Ram Pumping Engine— Evans' "Cornish" Double- acting Ram Pumps— Evans' Duplex Pumping Engine— Evans' Hydraulic or Water Motor Pump— Worthington Mine Pumps— Arrangement of Con- densers in Mine Pumps— Dank or Surface Engines for Mine Pumping— Pearn's Well or Mine Pump — Davey Pumping Engines— Sinking Pumps— Evans' Differential Ram Sinking Pump S9-7S CHAPTER VIII. — Hydraulic-Pressure Pumps. Intensity of Pressures fur Varying Services — Action of High Pressures —Differential Ram— Ram and Piston Type— Hydraulic Pumping Engines, by Frank Pearn & Co., and Rice =velocity in feet per second, g = accelerating force of gravity, say 322 ft. per second. Taking the quantity of the water (in cubic feet) in the suction column simply as the product of the pipe area and the height of suction, we have (neglecting any horizontal distances) : 20 x 9o = 13 '2 cubic feet. 144 = 1 3'2x6 - 23 gallons. = 13-2x6-23x10 lb. = 822 lb. Therefore, by substituting the figures for the symbolic letters in the formula, we have as the energy of our moving suction column : 822 x 7-7 x 7-7 „.,, „ , , , = Tob'lt footpounds. 2 x 32-2 t With these figures before us, it is evident that unless some such provision as a vacuum or suction chamber is provided for the absorption of the energy of the suction column (as a flywheel absorbs the surplus energy of an engine^, it will set up a decided hammer action and impose a great shock on the pump at the end of eacli stroke when the flow of water is suddenly arrested. Limit of Suction Lift. As the pressure at the base of a column of water about 2 "3 ft. high is just 1 lb. per square inch, it follows that under the normal atmospheric pressure of 29'9 in. of mercury, or 14'7 1b. per square inch, the maximum G THE CONSTRUCTION AND WORKING OF PUMPS. theoretical height to which water can be raised by the atmosphere is : 2-3 x 147 = 338ft. But for such a suction lift a perfect vacuum in the pump chamber and throughout the suction main is an essential condition. Moreover, even if a perfect vacuum were obtainable the pump would not work with such a suction lift, as there would be no energy available to overcome the frictional resistance to the flow of water, and to provide that excess of force, beyond what is due to merely balance the column necessary to keep the supply to the water chamber equal to the rate of displacement therefrom. Satisfactory pumping is sometimes effected under a suction lift of 26 ft., but as a general rule it is advisable not to exceed 20 ft. It frequently happens that in addition to a heavy vertical lift, a pump must be so fixed in relation to the source of water that a great horizontal length of suction piping is necessitated. In such a case it must be remembered that the atmospheric pressure acting on the surface of the water to be raised will have to perform the additional work of driving such, water through the long - horizontal portions of the suction main, and will therefore be that much the less available for balancing the atmospheric pressure acting on the delivery side of the plunger. When pumping against heavy pressures such as are employed in many hydraulic services, it is advisable to work without suction lift, making the water to flow into the pump chambers under a sufficient head to ensure that, they shall at all times be fully charged with water. In a power pump working under a pressure of, say, a ton or more per square inch, it is particularly necessary that the incoming water shall never lag behind the displacing action of the plungers or rams ; if it does so, the resulting con- cussion will suggest the working of a steam hammer rather than a steam pump. When pumping hot liquid, it is also necessary to avoid suction lift, and thus ensure that the pressure in the upper part of the rising or suction main shall not fall below AIR IN PUMP CHAMBER. 7 atmosphere. At atmospheric pressure the boiling point of water is 212 deg. Fan., but, as is well known, a fall of pressure is accompanied by a fall in the boiling point, the latter being as low as 162 deg. Fah. under a pressure of 3 lb. absolute, or about J of an atmosphere. With water at a high temperature, and with a pump so fixed as to have a heavy suction lift, the machine may be run all day without raising a drop of water ; the displacing action of the pump plungers simply bring about an evaporation of the water in the suction main, and thus steam or vapour will be delivered instead of water. The Effect of Air in a Pump Chamber. It is unnecessary to dwell upon the importance of pre- venting access of air to a pump suction main and connections, for it is obvious that if air does get in, the maximum amount of water cannot rise through the suction main, and the pump will consequently fall short of its proper delivery. But in certain types of pumps in which, for reasons that will appear later, the capacity of the pump chamber is considerably in excess of the displacement of each pump stroke, it may happen that the air in such chamber will prevent the admission of water from the suction main. A reference to the adjoining sectional sketch diagram, fig. 2, will perhaps assist in making the matter clear. The piump barrel A is fixed centrally within the large double-acting pump chamber B, having suction valves a a at bottom and delivery valves b b at top. Let us assume that after the pump has been working for some time delivering water to a tank fixed at a considerable height above the pump chamber, it has become necessary to make an internal examination of the chamber. For that purpose the valve C in the delivery pipe D is closed to prevent return of water, and the necessary covers of the chamber are then opened. At the conclusion of the inspection, and of the repairs, if any, the chamber covers are securely jointed, the valve C reopened, and the pump started again. It will probably be found, however, that no water will be delivered, because the full pressure of 8 THE CONSTRUCTION AND WORKING OF PUMPS. water in the rising or discharge main or pipe D acting upon the valves b will keep them closed against the air, with which, of course, the chamber became charged when its covers were opened. It follows that the air will not be dislodged, but simply compressed by the reciprocatory motion of the plunger E. In all such cases provision should be made (in some such manner as will be explained in a future article) for the working of the pump with little or no head or pressure upon the delivery valves bb until all the air is expelled from the chamber. PISTON SPEEDS. CHAPTER II. Piston Speeds. The speed at which a pump piston or plunger may be safely driven varies with the conditions Tinder which it is working. For obvious reasons, no user will want to purchase a larger pump than is absolutely necessary, and as the capacity of the machine (measured by the amount of water it will deliver in a stated time) is directly proportional with the speed, it follows that a pump which one maker will offer as having a capacity of, say, 5,000 gallons per hour, may he advertised by a less cautious firm as being capable of delivering 0,1)01) gallons in the same time. The difference is simply that in the hitter case the pump must lie run 20 per cent faster than in the former', and, of course, the steam consumption, or the power required to drive it, will be increased by a like amount. Where the total resistance to be pumped against does not exceed about 370 ft. water head, or a pressure of 160 lb. per square inch, a piston speed of 60 ft. per minute is good practice for the steady dailv working of a steam pump. This speed is frequently exceeded, and, under certain conditions, with advantage. Many long-stroke pumps are working with a plunger speed as high as 200 ft. per minute, and large pumping engines have been built and are said to have done good service against a low water head or pressures when running at 450 ft. per minute plunger speed. On the other hand, with hydraulic-pressure pumps, a speed of 20 ft. per minute may, in some cases, be quite fast enough, or even too fast, for satisfactory working. With a quick-running pump it is very essential to provide large valve areas and water passages, and especially so uir the suction side, to ensure that the pump barrels shall be completely filled with water at each stroke. It must also be remembered that the frictional resistance increases very rapidly when the water is propelled through the pipes at a high speed. At velocities up to about 3 ft. 10 THE CONSTRUCTION AND WORKING OF PUMPS. per second, or 180 ft. per minute, the Motional resistance is simply proportional to the speed, but at higher velocities the friction may increase as much as the square of the speed, or even at a greater ratio. Thus it is calculated that when water is forced through a 4 in. iron pipe at the rate of 1{ ft. per second, or 75 ft. per minute, the loss in pressure due to friction is less than 1 10th Hi. per square inch per 100 ft. length of pipe, whereas at a velocity of 10 ft. per second, or 1,14-0 ft. per minute, the frictioual loss will rise to rather more than 14 Hi. per square inch for everv 100 ft. length. Pipe Areas. "When determining the dimensions of the pipe connections of a pump, regard must be had to the question of friction just referred to, and on the suction side we must also consider the laws relating to falling bodies. It is especially essential to consider the relationship between the velocity of the moving body and the height from which it has fallen to acquire such velocity. The said relationship is expressed by the formula — h = iL where v = velocity in speed per second, and g = accelerating force of gravity, say 32"2. It follows, therefore, that the velocity varies as the square root of the head, aud that the theoretical velocity of water tinder any given head can be thus expressed— Velocity in feet per second = J head m teet x 2 100 to 150 54 to so 1 1* '■> M 10 75 to 125 1 1 5 to ioo 2 21 4 10 6 io ; 75 to 125 150 to 250 2 .-.i 5 4 12 ^i 10 75 to 125 315 to £.00 2} 3 14 101 j 10 I 75 to 1 25 440 t.i 740 2 J 8 7 1(1 12 10 75 to 125 610 to l,00o 21 10 s 18£ 14 10 75 to 125 S20 to 1,380 ;; 31 12 10 area of the pipes employed for the conveyance of a liquid than that of the pipes conveying a gaseous body, we have included in the list the sizes of steam-supply and exhaust pipes recommended by the makers. In every case it will riPE AREAS. 13 1 ><_■ seen that although the area of the steam cylinders exceeds that of the water cylinders (or pump barrels), the pipes for the latter use are much larger than those employed at the steam end of the pump. In calculating the capacity of Worthington pumps (or the quantity of water they will deliver in a given time), it must be remembered that the Worthington pump lias two double-acting water plungers ; its capacity, therefore, is twice that of any ordinary or simplex double-acting pump of same size, but having only one steam and one water cylinder, and four times as large as a single-acting pump. Let us consider the first pump given in the list, when running at such a speed as to deliver 34 gallons per minute. As each plunger must then make 200 strokes per minute, and as the length of stroke is 4 in., or ,! ft., it follows that the piston speed must lie — — = bo i it. per minute. 3 l Now, the area of each 2-|-iu. water plunger is 5'93 square inches, and the area of the 2 in. suction pipe is 3 14 square inches. But though the pump has two water plungers, it has but one suction pipe, and thus the ratio between the combined areas of the water plungers and the area of the suction pipe will lie 2 x 5 93 : 314, or 3 77 : 1. Therefore, as the piston speed or plunger speed is 66 '7 per minute, it follows that if the water cylinders are to be kept fully charged, the velocity of the water through the suction pipe must be not less than GG -7 x 3 '7 7 = 25 1'5 ft. per minute, or nearly 4-J ft. per second. In the same manner it will be found that with the fourth pump on the list (the 10 x G x 10), the velocity of the water works out at about 54 ft. per second, and with the last pump on list at about G ft. per second. It should be noted that as the stated piston speeds represent the average in the given unit of time (one minute), so also the calculated figures will give the average, and not the maximum, velocities of the water through the suction pipe in each case. 14 THE CONSTRUCTION AND WORKING OF PUMPS. An; Vessels. The greater the variation between the maximum and the minimum speed of a pump throughout its stroke, the greater the necessity for an air ves.se] on the delivery side to equalise the flow of water. In the direct-acting pump the speed is fairly uniform throughout each stroke, though a slight pause occurs at each reversal of the motion. But with a crank ami flywheel pump, in which the reciprocatory motion of the plunger is obtained from the rotatory move- ment of the crank, the speed of the plunger is ever varying throughout its stroke A single-acting crank and flywheel pump is the type with which an air vessel is most needed, whereas with a Worthington type or duplex direct-acting pump an air vessel may, in many cases, lie entirely dispensed with, and the smooth, quiet, and steady working of the pump still be maintained. In his "Mechanics of Pumping Machinery," Weisbach, considering the size of an air chamber for a manual fire pump or tire engine, says that its capacity should be at least eight times that of the pump cylinder. In simplex or single-cylinder single-acting pumps, it is no doubt well to keep to some such ratio, large as it may seem to those accustomed only to the much smaller air vessels, which (if necessary at all) are found to be accompanied by a uniform water delivery in quite large duplex double-acting pumps. A pump may lie provided with an air vessel or chamber of more or less fanciful design and got up in burnished brass or copper, but whether it serves any useful purpose will depend upon what it contains. When the pump was first started the vessel was, of course, charged with the substance which gives its name, but after the pump has been working some time it is more than probable that all the air has been gradually absorbed, or withdrawn by the outflowing stream, and the vessel becomes completely waterlogged. To ensure that the air vessel of a pump is really a vessel containing air it should be fitted with a gauge glass, and stop valves should lie provided to permit of the ready withdrawal of the accumulated water and re-charging with air. AIR VESSHLS. 15 For the automatic charging of an air vessel with the ordinary working of the pump to which it is attached a snifting valve is sometimes provided to admit air into the pump chamber or barrel on each suction stroke. It is better practice to arrange an automatic air-charging device separate from the pump barrels, and so avoid the reduction of the capacity of the pump which results from the former system. Fig\ 4 is a sectional view of one type of air vessel suitable for direct attachment to a pump chamber. The lower end of the delivery pipe or discharge main A dips or passes into the interior of the vessel, as shown, and hence is termed the "dip pipe." The lower end, or water inlet end, of the a Fig. 4 Fin. 5. Fie. 0. vessel is provided with a narrow neck, as shown, whilst the upper part of the vessel is splayed, to give the advan- tage of a large water surface in contact with the air, such surface being less liable to disturbance by the flow of the water. To give a greater opportunity for the separation and lodgment in the vessel of any air brought in by the water, an arrangement such as is shown at fig. 5 may be adopted. in this case the incoming water must, as will be observed, fall towards the bottom of the vessel in order to enter the dip pipe, and during such descent the air has a good chance of rising to the upper part of the vessel. For the same 16 THE CONSTRUCTION AND WORKING OF PUMPS. reason air vessels are sometimes provided with double dip pipes, the incoming water being passed through one pipe, which discharges at the top of the vessel, whilst the out- going water is discharged through the other pipe, which has its open end near the bottom of the vessel. The pipes enter the vessel centrally, but are suitably curved to enable them to clear each other in its interior. Fig. 6 is an illustration of a convenient type of air vessel of a small capacity. It consists of a plain, narrow-necked chamber, closed at one end and bolted to a bend, which is itself mounted directly upon the top of the pump chamber. CHAPTER 111. Arrangement of Pipes and Connections. Evert pump maker knows how frequently it happens that the working of one of his machines, in every respect suitable for the service required of it, is much impaired or rendered altogether impossible through a bad arrangement of pipes and connections. With many users the provision of an extreme suction lift (to obtain the imaginary advantage referred to in our first chapter) is the chief error to be encountered. But though with better informed people, an excessive suction lift will not be adopted, other errors which result in considerable trouble and inconvenience are not always avoided. Makers of wide experience are careful to intimate in their catalogues that when a pump draws from a supply of water beneath it, no part of the suction main should rise above the level of the pump-chamber inlet. Or, to put it in other words, the entire length of the pipe or main should fall from the pump to the water supply. If this Warning lie acted upon, then, in a case such as illustrated at fig. 7, in which a pump chamber A (shown in end elevation), must of necessity be placed on the side of a wall B. away from the sump or source of the water supply C, the erector will ARRANGEMENT OF PIPES AND CONNECTIONS. 17 be careful to avoid carrying his suction pipe over the top of the wall (in the manner indicated by the dotted lines), even though the height of the wall above C is well within a moderate suction lift. But if, disregarding the warning, he does adopt the dotted line arrangement for his suction pipes, he may save himself trouble for the time being, but Fig. 7, Fig. 8. there will lie plenty of it subsequently from the accumu- lation of air in the elevated siphon so formed. The pipe should in this and similar cases be carried through the wall, as shown by the full line in the figure. Pump designers themselves are not, however, always careful to so arrange the delivery valves and outlet con- nections on their pump chambers as to avoid the lodgment of air within such chambers. Fig. 8 is an illustration of a single-acting ram pump, in which the branch or connection D, containing the suction and delivery valves, is arranged at the top of the chamber. As the delivery valve is, in this arrangement, above the chamber proper, any air coming in with the water through the suction valve will readily flow out on the down stroke of the ram, through the delivery valve. But if, instead of the valve branch being arranged as above described, it is disposed in a lower position on the purnp chamber, as indicated by dotted lines on the left 2cp 18 THE CONSTRUCTION AND WORKING OF PUMPS, hand of the figure, any air brought into the chamber may become lodged in the upper part of it, thereby limiting the capacity of the pump. Position of the Vacuum Chamber. We have previously considered the necessity for the pro- vision of a vacuum chamber, or suction chamber, to absorb the energy of a long suction column. But in order that it may properly perform such a function the vacuum chamber must be placed in a favourable position. At fig. 9 three positions for the suction chamber are indicated by dotted lines. The position A at right angles to the flow of water is a bad one, as the impact would be imposed on the pump before the water had time to alter ita course for the flow into the vacuum chamber. With the position B the water flowing up the vertical suction main can ascend into the vacuum chamber without any alteration of its course. The position C is a good one in the case of a long length of horizontal suction main. As will be seen, the vacuum chamber is arranged cm the side of the pump chamber D, opposite to the suction main E, so that the water can flow right through the lower part of the pump (beneath the suction valves), and by an easy bend pass into the vacuum chamber. CHARGING CONNECTIONS FOE SUCTION PIPE. 19 Strainer, Foot Valve, and Charging Connections for Suction Pipe. The general practice, in this country at any rate, is to fix the strainer (when such an attachment is necessary) upon the bottom of the suction pipe. The advantage of this position is that solid matter such as the strainer arrests is kept clear of the foot valve. It may be noted that in making a strainer care should be taken to have the combined areas of the strainer holes not less than two or three times in excess of the suction pipe area, in order to allow a sufficient inflow even though a number of holes may lie blocked. But the difficulty of getting at the strainer to free it from obstruction when it is fixed on the end of the suction pipe has led to the adoption of the arrangement indicated to the left hand in ficr. ID. The strainer S is arranged, as is shown, adjacent to the pump chamber, and thus it can bo very readily inspected and cleared as may be required. The strainer should comprise two main parts, viz., the strainer proper consisting of a wire basket or perforated diaphragms, and a box or casing' enclosing- the same, but permitting of ready insertion or withdrawal. 20 THE CONSTRUCTION AND WORKING OF PUMPS. Foot valves, like check or retaining valves generally, are made with the moving parts, or valves proper, arranged in various ways. The types to avoid are those in which wing like or other projections are formed on the valve itself to guide its movement, for such a valve is very liable to become clogged, and so stuck up off its seating. The valves should always be of the flat or disc type, having nothing below the surface which rests upon the fixed seating, and thereby forms the joint. A very satisfactory foot valve is made by the Worthington Pumping Engine Company ; it is of the multiple type, a number of small metal disc valves with leather faces being arranged in the one chamber or casing. The dotted lines at fig. 10 indicate a convenient arrange- ment of japes and connections for charging the pump chamber and suction main with water from the delivery main before restarting the pump after a stoppage. For after a stoppage it may lie, as explained in our first chapter, that the pump will not lift the water because the motion of the plungers simply compresses the air instead of com- pletely displacing or dislodging it. But on opening the valve in the pipe A, fig. 10, which connects the delivery main (beyond the check or retaining valve B) with the suction pipe or main C. the latter and also the pump itself can be readily charged with water. The waste deliveiy pipe D, when its valve is opened, permits of the escape of the air displaced from the pump chamber. The pipe I) may with advantage be left open during the first few strokes of the plungers, but it should, of course, be closed when the pump has fairly caught its water. Bell-mout[[ fob Suction Pipe, and Nozzle for Delivery Pipe. Just as a stream of water issuing from an orifice is contracted to an area less than the area of the orifice (such contraction being termed vena contracta), so a contraction of the stream occurs when water flows into a pipe. To diminish the effect of such contraction and to facilitate the inflow of water, the lower end of a large suction pipe is sometimes rounded or is provided with a bell-shaped mouth. And to give a steadv and full bore or solid dis- PLUNGERS AND PLUNGER PACKINI 21 charge from the delivery pipe the outlet end of such pipe is sometimes provided with a conical or curved discharge piece or nozzle. A. " fireman's nozzle " is a good example. CHAPTER IV. Plungers and Plunger Packing. Pump plungers may be either of the "externally-packed" or the "internally-packed" type. In general, externally- packed plungers are styled " rams,'' and pumps fitted with the same are frequently known as ram pumps. In like manner pumps fitted with internally-packed plungers are sometimes known as plunger pumps or piston-pattern pumps: Each type has inherent advantages and disadvantages, which we will briefly consider. The sketch diagrams, figs. 11 and 12, representing a rain and a piston-pattern pump respectively, will serve to keep the two types before us during such consideration. In the ram pump, fig. 11, there is simply a stuffing box to be kept packed, whereas in the piston-pattern pump, fyJmrri y . ' ^ I t~k; i r fio-. 12, we have both a stuffing box and the internal plunger or piston to attend to. A stuffing box can be very readily packed, but it is frequently a difficult and troublesome business to pack a plunger, for the end cover joint must be broken and subsequently re-made, and if the plunger, rod, and plunger cap are made of iron, the three parts will probably be so rusted together that the task of removing 22 THE CONSTRUCTION AND WORKING OF PUMPS. the cap to permit of the insertion of the packing may involve the expenditure of much time and temper. A man who has had such an experience will be a strong advocate for the adoption of brass plungers and rods. A ram pump can be used for dealing with gritty water, whereas, with a plunger or piston-pattern pump on such a service, waterways are speedily cut along the plunger and the barrel, with the result that a quantity of the liquid is simply churned back and forth in the barrel instead of being displaced from the same. Leakage of water through the gland of a ram pump is at once observed, but the leakage past a plunger cannot, of course, be seen. In the latter case, the leakage is revealed only when it has become so extensive as to seriously diminish the output or delivery of the machine. Turning now to the other .side of the question, we have to remember a ram is ordinarily single acting, delivering water only on every second stroke. A plunger or piston can be double acting, so that when running at the same speed it will deliver double the quantity of water discharged in an equal time by a ram of the same diameter and length of stroke. A ram-pattern pump can be made double acting", but two rams, or a single rani with divided chamber, must be employed. It is obvious, therefore, that in the matter of compactness and simplicity of outline the advantage is with the piston pattern. On many services it is of prime importance that the capacity of the water cylinder shall be but little in excess of the displacement effected on each pump' stroke, or, in other words, that the amount of air space or clearance in PLUNGERS ANIl PLUNGER PACKING. 23 the water cylinder shall lie reduced to a. minimum. For such services ram pumps are quite unstated, Unless the glands of ram pumps are most carefully packed, a very large proportion of the work put into the pump will be required simply to overcome the friction between the packing and the surface of the ram. It is a very easy matter to pull up a pump by tightly screwing down the gland, and, unless otherwise directed, an attendant, in his anxiety to prevent leakage through the stuffing box, may put in so much packing that he must perforce vigorously ply hammer and drift before the studs can be made to project through the face of the gland ; the latter is then screwed down till the perspiration rolls from the forehead of the honest but thoughtless workman. The packing that may give every satisfaction for the glands of steam piston rods is generally quite unfitted for the glands of pump rams and water pistons or pump rods. At the water end of the steam pump the gland packing should be soft and well greased throughout. For the rams of pumps for hydraulic presses and other high-pressare services, self-acting leather packings of the U or hat types may be employed with cold liquids, lint owing to iheir annular form they cannot lie so readily inserted as hemp or like packing', and hence the latter is more generally adopted. With a piston or plunger, a self-acting packing of the well-known cup leather type can lie fitted without great difficulty. The pump barrel should, however, be invariably brass lined, for self-acting packings are very rapidly destroyed unless the surfaces against which they work are quite smooth and free from corrosion. Pump water pistons or plungers may be packed with soft hemp or similar packing in the manner indicated at fig. 12. They are sometimes also packed with rings made of a non-corrosive metal. Plungers without any packing whatever give every satisfaction on services where there is but a moderate head or pressure (not exceeding about 1501b. per square inch) to be pumped against. In such cases, however, the plunger should be made somewhat longer than an ordinary packed piston to provide ample 24 THE CONSTRUCTION" AND WORKING OP PUMPS. wearing surface. The slight leakage of water past a plunger of this description is more than compensated i>y its freedom from the friction involved in the use of a. packed plunger. Valves. The provision of multiple valves on pump chambers is now a universal practice. In the veil-known flat-disc form they appear to have been first generally adopted in America upwards of 50 years ago. in connection with boiler-feeding and bilge pumps for steamships. "All pumps for this service," says an American writer, "were formerly provided with only one valve to each end of the pump chamber. The valve was flat and oblong, covering a port like that of a steam chest, and rocked open and shut on a half hinge on one side, governed by a flat .spring of hard brass. A small obstruction under the heel of this valve would throw that end of the pump out of commission. It was quite common to find pieces of wood, scraps of leather and rubber, and sometimes a fireman's cap and overalls in the valve chambers." " The multiple valve," proceeds the same writer, " scored a great success, as the valve plates acted as a coarse strainer, and all the debris and rubbish that came up from the bottom of the ship stopped in the large suction chamber, and could be removed from time to time as the pump showed signs of strangulation." Fig. 13 is a sectional elevation of the metal disc type of valve, several of which can be fitted, when the multiple valve system is adopted, to control the suction and delivery ports or apertures of a pump chamber; fig. 11 is a. plan VALVES 25 of the valve seating. The valve itself consists of a metal disc A, or a rubber disc may be employed for cold water. The guard B is screwed into the valve seat C, and the latter is itself screwed into position in the pump chamber. The spring D retains the valve on its seating. As there is no projection of the valve below its seating, it cannot become " stuck up " therein. As already stated, a number of valves of the type illustrated can be arranged on the one pump chamber, but in pumps for working against heavy pressures, though the disc type of valve can still be advantageously employed, each valve (or group of valves) should be disposed in a separate pot or valve chamber. The detachable head or cover of each valve pot or chamber can be provided with a hollow projection or socket to serve as the valve guard and stop, a corresponding central projecting stem being formed upon the upper side of the valve to enter the said socket. When rubber discs are used in place of the metal discs, as A, fig. 13, a metal plate or washer should be interposed between the back of the valve and the metal spring. Fig. 15 represents, in sectional elevation, a suction and a delivery valve arranged on one central stem. The valves are of the type sometimes known as " double-way," because the water can flow out under both the inner and outer edges of the ring-like bearing piece of the valve when the latter is raised from its seating, whereas in the valve shown at fig. 13 the water has but one annular space to 2C THE CONSTRUCTION AND WORKING OF PUMPS. flow through. A plan of one of the double-way valves is shown at fig. 16. Tubes or hollow buffers of indiarubber are sometimes employed instead of the valve springs ; and we here note that in all eases it is advantageous to employ Fio. 15 JO. w <-l l i l i p.v w^ Fig. 16. springs or buffers of such a normal length that the valves have a certain amount of free lift before commencing to compress the springs. The old form of flap or clack valves is still frequently adopted, especially for services where the water is gritty VALVES 27 or contains solid matter. The valve in its simplest form is readily made from a pad of leather which is secured on one side to the valve seat, such secured side serving as the hinge. The leather is topped with a metal plate or disc, the two parts being fastened together by means of copper rivets. Though suitable for low lifts and slow speeds, the objection to this type of valve is the necessity fur allowing them a large movement in order to obtain a free waterway ; the valves are. therefore, comparatively slow in closing, with the result that the " slip,'' or return of writer through them, is considerable. Large valves provided with several clacks or flaps, are termed " multiple- clack " valves. They are made in many forms; one type is shown in outline at fig. 17. A very simple type of valve suitable for small slow-speed pumps is shown in section at fig. IS. No guide is needed with such a valve, as it will always right itself in seating. The valve itself, or the " valve fall " as it is sometimes termed, consists of a cast-iron hollow cone, as illustrated at fig. 19, which has simply to be faced under the head and necked for the reception of the rubber ring K ; the latter is sprung into position on the fall. Perpendicular lift valves can lie provided with two or more seats, either in the same plane or one above the other, and for large pumps such ''double-beat," "treble-beat," i!8 THE CONSTEUCTION AND WORKING OF PUMPS. or " multiple-beat " valves in various forms are commonly employed. Fig. 20 illustrates a valve in which the" beats," or parts which come into contact with the seat, are arranged in the one horizontal plane. Such a valve may be termed a " quadruple-way valve," seeing that the water will escape through both the inner and outer annular spaces formed between each of the ring-like parts, A and B, when the valve is lifted from its seat. Many other varieties of multiple-beat valves are designed and produced to suit sundry requirements, fads, and fancies. i10ilkr feed pumps. 29 Mechanically-operated Valves. The valves previously considered are opened solely by the water pressure imposed upon them, and it is obvious that they cannot open until after the application of the pressure. In practice, no great difficulty is experienced with such valves, even when running at high speeds, if the pump is veil designed throughout and adapted to the required service. But in certain pumps of German origin the valves at the water end are, under the Riedler system, positively operated by mechanism worked by a moving part of the pump. The valves are said to "operate with a liberal lift, avoiding any throttling. The mechanism is exceedingly simple. Each valve is closed at the moment the stroke of the piston changes, and this closing is clone by means of a spindle projecting into the valve chamber. Near the end of the stroke a very small free lift is allowed to the valve, which can be regulated at will." Mine-pump- ing engines with the Riedler valve system were first built in 1884, and since that year a large number of such engines have been constructed for various countries, but especially for the deep mines of Bohemia, Silesia, Westphalia, and Belgium. CHAPTER V. Boiler Feed Pcmph. The advantage of employing a small steam pumping engine, or donkey pump, for the sole purpose of boiler feeding is now generally recognised by steam users. To meet the demand for such pumps, so man)- makers have entered the market that a purchaser may well find it difficult to make a. wis3 selection. It has been truly said that "the cheapness of an article depends on more things than price," and in the selection of a boiler feed pump it is of especial importance to bear such a statement in mind. First and foremost, a boiler feed pump must lie absolutely reliable. To that end its working parts must be few in i!l I THE CONSTRUCTION AND WOEKING OF PUMPS. number and of great simplicity and durability. There must be no risk of the steam controlling valve or any other part becoming " stuck up" or failing in action. The user must be assured that so long as he keeps steam supplied to the pump, so long will it continue to work steadily and uniformly, requiring no frantic manipulations of a starting lever from time to time, or any like assistance from the stoker or attendant. The water in a boiler should be maintained as nearly as possible at one constant level, and the pump should there- fore be capable, when running at a moderate speed, of making the feed keep pace with the maximum rate of evaporation in the I toiler. The surroundings of a feed pump are, more often than otherwise, anything but conducive to the sweet running of machinery of any kind, and hence any elaboration of working parts should lie carefully avoided. The feed pump may get a little oil now and again, but it seldom gets any other attention. When a feed pump is in a fair working condition the " slip " should not exceed 5 per cent; in other words, the pump should actually deliver an amount of water equal to 95 per cent of the measured displacement. But if the plungers or plunger packings are allowed to get into a bad condition the slip may be upwards of 25 per cent, in such a case the speed of the pump must, of course, Vie increased to maintain the water level, resulting in a proportionate increase in steam consumption and in the wear and tear of the working parts. Ratio Between Steam, ami Water Pistons. In the sketch diagram, fig. 21, A and B respectively represent the steam and water cylinders of a pump for feeding the boiler C, Each cylinder is fitted with a piston directly connected by a rod as indicated. If the pistons are of equal area, it is evident that they will fie in equilibrium when both steam and water connections are opened to the respective cylinders A and B, for whilst the steam pressure will tend to drive the pistons in the direction indicated bv the arrow 1, the water pressure will tend to drive them with equal force in the opposite direction. It is clear, therefore, BOILER FEED PUMPS. 31 that with such a pump the area of the steam piston must be in excess of the area of the water piston or plunger if the water is to be driven into the boiler. The ratio between the two must lie such as to provide sufficient force to overcome the friction of the moving parts of the pump, of the fluids in motion, and to effect the performance of the work of displacement. The general practice is to adopt a ratio of about 2 to 1 — that is, to employ steam ami water pistons of such diameters that the area of the former shall be double the area of the latter. With small feed pumps the ratio is somewhat greater, and with larger feed pumps frequently somewhat less, than 2 to 1, for we usually find that the friction is proportionate!}* more in small pumps. As examples, we will here refer to the standard sizes of leading types of feed pumps, of which, by the courtesy and special permission of the milkers, illustrations and particulars will lie given in the course of these articles. The ordinary list sizes of the " Favourite " double-acting donkey pumps (illustrated at fig. 22), by Mr. A. LI. Mumford, of Culver Street Engineering Works, Colchester, are as follow : — Diameter of steam cylinder.. Diameter of water plunger .. Length of stroke 4'. H t;2 THE CONSTRUCTION AND WORKING OF PUMPS. The " Cameron " type double-acting pumping engine (illustrated at tig. 23), by the same maker, is made to the following sizes : — Diameter of steam cylinder... 6 Diameter of water plunger ... 3^ Leo gth of stroke ti J 1 8 10 4 r K 6 7" 8 9 Fig. 22 BOILER FEED PVMPS. — / CITY C: Sep 34 THE CONSTRUCTION AND WORKING OF PUMPS. The following are some of the sizes adopted by the Pulsometer Engineering Co. Limited, of Nine Elms Ironworks, London, S.W., in their single-cylinder direct-acting " Deane " boiler feed pumps : — Diameter of steam cylinder. Diameter of water cylinder . Leneth of .stroke H 4 f>i 6 10 n 2 A H 4 ti K 10" 10 10 12 Messrs. G. and J. Weir Limited, of Cathcart, Glasgow, adopt the following ratios in their single direct-acting pumps for boiler feeding : — Diameter of steam cylinder.,. ?i 8 9i 10! 12 Diameter of i»umji cylinder ... rj_ 6 7" 8 9 1j~ IS 21 24 24 COMPOUND FEED PUMPS. 85 The following selection of ratios is from the lists of the Worthington Pumping Engine Co., of 153, Queen Victoria Street, London, E.C. : — Diameter of steam cylinder. Diameter of water plunger . Length of stroke li 4'. ti 10 12 3 -l. 1 , i 9| 4 6 10 10 Fig. 24 is a sectional illustration of a Worthington standard type horizontal feed pump, to which we shall again refer in another chapter. Messrs. W. H. Bailey and Co. Limited, of Albion Winks, Salford, adopt the following ratios in their " Davidson " patent boiler feed pumps : — Diameter of steam cylinder Diameter of water plunger . Length of stroke H in. in. m. i]i. 5i 1 12 14 H i / 8 8 10 12 14 ( 'ompouxd Feed Pumps. With the high steam pressures now so generally adopted on various services, a demand has arisen for boiler feed pumps having compound steam c}dinders. With such pumps a considerable saving of steam is effected ; in many cases the high-pressure cylinder can be made of less diameter than the pump barrel. The following ratios are adopted by the 1'ulsometer Engineering Co. Limited in their single type compound feed pump : — Diameter of high-pressure cylinder. Diameter of low-pressure cylinder. Diameter uf pump barrel. Length of stroke. Inches. Inches. Inches. Inches. 4 12 H IS 5 15 7'- IS -1 ■ THE CONSTRUCTION AND "WORKING OF PUMPS. The sizes hereunder are selected from the "N orthington Pumping Engine Co. 'a lists of Worthington or duplex type compound pumps suitable for boiler feeding : — Diameter of high -pressure cylinder. Diameter of low-pressure cylinder. Diameter of pump barrel. Length of stroke. Indies. Inches. Inches. Inches. 51 71 '■> 6 6 9 7 10 s 12 101 10 9 14 12 10 10 16 14 10 Messrs. \V. H. Bailey's "Davidson" patent compound pump has cylinders proportioned as indicated in the following selections : — Diameter of high-pressure cylinder. Diameter of low-pressure cylinder. Diameter of pump barrel. Length of stroke. Inches. Inches. Inches. Inches. 4 S 4 10 51 10 5.1 12 6 12 12 7 14 7 14 9 1 9 IS Steam Consumption iji Feed Pumfs. The steam consumption of a feed pump may lie stated as the quantity of steam used per horse power per hour, and for general comparative purposes such a statement is very convenient. But it is sometimes more advantageous to have the information expressed in terms giving the quantity of water delivered into the boiler for every pound of steam supplied to the pumps. STEAM CONSUMPTION IN FEED PUMPS. 37 Referring again to tig. 21, it will readily lie understood that if it were possible for a pump to work with steam and water pistons of equal areas, as therein shown, then, dis- regarding all condensation losses of ever}' kind, the ratio between the steam consumption and the water delivered into the boiler would be just the ratio between the weight of the steam and the weight of an equal volume of water. Seeing that the steam and water displacements are just equal to each other, it follows that the delivery of a cubic foot of water into the boiler will involve the withdrawal or expenditure of a cubic foot of steam. We thus have a very simple and very convenient ideal standard of reference. The weight of a cubic foot of water is about 62 '3 lb., wdiereas 1 Hi. of steam at 1001b. boiler pressure will occupy a volume of about 3'8 cubic feet. The ideal quantity of water deli- vered per pound of such steam is thus 02-3 x 3-8 = 236-7 lbs. The steam consumption per horse power per hour of our ideal or reference pump, with the aforesaid steam pressure, we can calculate as follows : — 33000 x 60 Hi x 100 137 '5 cubic feet 137-i 36'1 His. per hour. Now, although the ideal or reference pump on wdiich the foregoing calculations are based is assumed to work without expansion, yet, even in compound boiler feed pumps using considerable expansion, the results will not equal the figures we have given. In ordinary single-cylinder steam pumps ■working with little or no expansion, the steam consumption must of necessity be very much higher than our figures, for, as we have already seen, the steam piston must be about double the area of the water plunger, and, in addition, there is the consumption of steam on each pump stroke in the clearance spaces and ports ; the said addition may repre- sent more than 15 per cent of the total steam consumption of the pump. 38 THE CONSTRUCTION AND "WORKING OF PUMPS. lu a paper by Mr. Alexander Borodin on "The Working of Steam Pumps on the Russian South-Western Railways," read before the Institution of Mechanical Engineers in the year 1893, some extremely interesting particulars were given concerning tests conducted on quite a number of pumps of different makes, employed for the water supply at the principal stations. The value of the tests is much enhanced from the fact that the pumps were all tried in their ordinary working condition, without any special preparation with a view to the attainment of good results. W e may again have occasion to refer to these trials, In it for the present will simply note that the steam consumption ranged from 501b. per horse power per hour in a Worthington compound pump to the enormous quantity of 8551b. per horse power per hour in a small pump made by another maker. The latter pump was not tested by the author of the paper referred to, but full particulars are given of the figures obtained at the test. "Steam pump manufacturers," said an American writer, in the year 1897, "claim to run on as low as 75 lbs. of water (steam) per indicated horse power per hour, but it is not uncommon to find it double that amount." We may add that compound boiler feed pumps can now lie obtained with which the steam consumption is given by the makers as "less than 501b. per duty horse power per hour." As is well known, the injector is an extremely uneconomical appliance for pumping water. An ordinal')' injector will use about four times as much steam as an ordinary pump doing the same work. CHAPTER VI. Types of Boiler Feeh Pujips, In selecting a feed pump a buyer has first of all to decide between crank and flywheel and non-flywheel pumps. Non- flywheel pumps are frequently called "direct-acting," but inasmuch as many flywheel pumps have the steam and water pistons directly connected, the term is not sufficiently distinctive. FLYWHEEL PUMPS. 39 Each type has its advocates, from whom information may be obtained concerning the advantages of the one and the disadvantages of the other. Flywheel Pumps For crank and flywheel pumps the chief claim made is that they are more economical than non-flywheel pumps. Now, while it is perfectly true that many flywheel pumps are working with greater economy than non-flywheel pumps, it is equally true that steam pumping engines of the latter type can be and are made to equal the most economical fly- wheel pumping engines yet constructed. But the pumps or pumping engines (for we are now considering pumps having their own steam or motor cylinders) employed for boiler feeding are generally of small dimensions. A boiler supplying a hundred horse power engine can be fed by a pump having a steam supply pipe only three-eighths of an inch in diameter. With such small pumps and running at the slow speeds necessary if the water in the boiler is to be maintained, as it should be, at one constant level, it is obvious that the momentum of the flywheel must lie exceedingly moderate, and therefore that the amount of "cut-oft"' (or expansive working) permissible can lie very little, for the work is, of course, a constant quantity. in boiler feed pumps having the slide valve or steam controlling valve operated from a rotating crank shaft receiving its motion from the reciprocating piston rod, it is, of course, necessary to provide a flywheel to carry the crank over the " dead centres." ft is such carrying over that constitutes the chief function of the flywheel. When the pump is running at full speed a slight saving of steam may be effected by expansive working. A great objection, however, to the crank and flywheel pumps is to be found in the difficulty experienced in running them at slow speeds. As an illustration, it may here be mentioned that some of the hydraulic lifts or elevators of the Eiffel Tower were originally worked by flywheel pumps. After the experience gained at the Exposition of 1889 the authorities decided to increase the elevator capacity for the 40 THE CONSTRUCTION AND WORKING OF PUMFS. 1900 Exposition, and although they at first only con- templated additions to the existing pumping plant, they finally decided to take oat all the flywheel pumping engines, and do the whole elevator service for the tower with non- flywheel pumps. It was found that flywheel pumps were always noisy in action, and that they were continually stopping when it was attempted to run them at such a speed as was sufficient to maintain the amount of water required at certain periods. Xo such difficulty was experienced with the non-flywheel pumps. Non-flywheel Pumps. Non-flywheel pumps may be divided into two main classes, viz., single and duplex. Single non-flywheel pumps are usually associated with a steam operated slide valve, which, as frequently arranged, is anything but certain in its action, though, as we shall presently see, single non-flywheel pumps can be constructed with positive valve gear. Duplex Pumps. The duplex pump was invented by Henry R. Worthingtou> of New York. It was not until about 21 years ago that the pumps were generally introduced to this country by the company bearing the name of the inventor, but their good qualities gained speed}- recognition. Duplex pumps are now constructed by most leading makers in all manufacturing countries. The duplex pump comprises two single pumps arranged side by side on the one framing. The slide valve of each steam cylinder is actuated by a lever which is rocked by the movement of the piston rod of the adjacent cylinder. Each piston thus acts to give steam to the other, and on finishing its stroke it must wait for its own valve to be acted upon before it can renew its motion. This pause allows all the water valves to seat quietly and removes all harshness of motion. The pump is absolutely reliable in its action, for as one or the other of the steam valves must always be open, there can be no dead points. The machine starts directly the steam is turned on, and will continue to work until it is shut off. WORTHINGTON L10ILER FEED PUSH'S. 41 It is particularly necessary for the proper working of duplex pumps that the piston and gland packings should be uniform. If such packings in one cylinder are tighter than in another, the one piston will move sluggishly as compared with its neighbour, with the result that the motion of the slow piston will be reversed before it has completed its stroke. One side of the pump will thus exhibit the effect known as "short stroking." As the clearance remains constant whatever may be the length of the pump stroke, it will be readily understood that short stroking means waste of steam. WoETHIXGTON Bun. Eli FEED l'UMl'S. The sectional view through one side of a Worth ingtoii piston pattern feed pump, given at fig. 24 in our last chapter, clearly represents the arrangement of the separate admission and exhaust ports at each end of the steam cylinder, and the disposition of the suction and delivery valves above the water cylinder. In its motion each steam piston passes over its cylinder exhaust ports, and an efficient cushioning effect is thus obtained from the entrapped steam. Levers are pro- vided (with the pump illustrated), to permit of the operation of the machine by hand. I'urnps of the type shown are suitable for steam pressures up to 1601b. per square inch. Similar pumps are constructed with compound steam cylinders. Fig. 25 is an illustration of a Worthington ram pattern feed pump. A sectional view through one side of the pump is given at fig. 2G. It has a great advantage over piston or plunger pumps, in that leakage can be at once observed and readily taken up whilst the pump is in motion by simply screwing up the glands. The water end of the pump is so designed that there are no air pockets when it is placed in a vertical position, and thus the machine can lie fixed either horizontally or vertically as may be required. In the pressure pattern type Worthington ram pumps, for working against pressures up to .'1001b. per square inch, the water valves are located in separate valve boxes consisting of independent castings bolted to pump barrels. Such an arrangement permits of the ready inspection and renewal of the valves. 42 THE CONSTRUCTION AND WORKING OF PUMPS 1 Mumfoed and Anthony's Patent Duplex Pump. A sectional view through one side of the above-named pump (made by Mr. A. (J. Mumford, Culver Street Engi- neering Works, Colchester) is given at fig. 27. The maker's- general description is as follows : — " Tn the steam cylinder there is only one moving part, viz., the piston, in which steam passages are so constructed PATENT DUPLEX PUMP. 43 44 THE CONSTRUCTION AND WORKING OF PUMPS. that the usual slide valve is dispensed with, as well as levers, pins, and other small parts. The surfaces of the pistons are especially lengthened, so that their durability has become phenomenal. Each piston acts as a slide valve for the admission of steam to the opposite cylinder and (in due course of travel) its eduction passage, besides discharging its duty in the ordinary way of actuating the pump. The steam passages are carefully arranged, so that either piston will start from any position. There are no dead centres, and, throughout a course of severe tests and lengthened trials, these pumps have never been known to stick nor stop of their own accord. They are easy in working, and there is a complete freedom from shock. The pistons are perfectly balanced, and a certain steam cushion is provided at the end of each stroke. Full travel is always assured, and, in the event of pressure being withdrawn, the cushion is maintained.'' Mtjmfobd's "Favourite" Donkey Pump. We illustrated this well-known flywheel donkey pump (double acting) at fig. 22, in our last chapter. It is a very compact pump, and can be readily bolted to a boiler, to the side of a, vessel, or other vertical support. Mumford's Ca.mekox-tyfe 1'u.mp. An illustration of the above is given at fig. 23 of our last chapter. The valves and all parts of this self-contained pump are adapted for working against heavy pressures, and are readily accessible for easy inspection. The illustration shows a double-acting pump ; but they are also made single acting — that is, with rams instead of with plungers or water pistons. Weir's Sixgle Feed Pumps. The Weir patent direct-acting feed pumps, as they are termed, have been known for a number of years as high- class machines for marine work. Fig. 28 is an illustration of the Weir pump of the standard land-service type, whilst tisj-. 29 is a sectional view taken at right angles to fur. 28. WEIRS SINGLE FEED DUMPS. 45 ,, ^A», 46 THE CONSTRUCTION AND WORKING OF PUMPS. The makers (Messrs. <>. and J. Weir Limited, of Cathcart, Ulasgow) give the following specification of this machine : — "The Weir standard feed pump is single cylinder, double acting, and vertical. The steam cylinder is of close-grained cast iron, and covered with planished sheet steel. The pump end is of cast iron, fitted with best Admiralty gun metal liner. The pump rod consists of one piece of cold- rolled manganese bronze. The valve seats and valve are of the Weir pateut group type, which comprises a number of small valves in a circular trim metal seat, thus affording a large valve area with only a small lift. The valves are of special bronze, and the valve seats of Admiralty gun metal. The water pistons are also of gun metal, and fitted with ebonite packing rings. These pumps are suitable for boiler feeding up to 2001b. pressure, and can pump either ?iot or cold water. "The steam valve gear comprises a main and an auxiliary valve. The main valve is for distributing steam to the cylinders; the auxiliary for distributing steam to work the main valve. The main valve moves horizontally from side to side, being driven by steam admitted and exhausted from each end alternately. The auxiliary valve is actuated by lever gear from the rod of the pump, and moves on a face on the back of the main valve, and in a direction at right angles to the main valve. By this arrangement there is no dead centre, the action being absolutely positive, because the only possible position in which the main valve can rest is at full travel, either for an up or down stroke of the piston. Both the main and auxiliary valves are simply slide valves, but the former is half round, the round side working on the cylinder port face, which is bored out on one side to fit the valve. On the back of this main valve a flat face is formed for the auxiliary valve to work upon. Both ends of the main valve are lengthened so as to project beyond the port face, and are turned cylindrical with fiat ends. Caps are fitted on each of these ends forming cylinders, which are closed at the mouths by the flat ends of the main valve, which act as pistons. The function of the auxiliary valve is to admit steam through the ports on the back of the main valve to move the main valve from wide to side. The ports for WEIRS SINGLE FEED PUMPS. -13 47 Fio. 29 48 THE CONSTRUCTION AND WORKING OF PUMPS. admitting steam to the top and bottom of the cylinder are arranged to cut off before the end of the stroke, and so slow down the pump, thus permitting the water valves to to settle quietly and relieve the connections from any shock. On the last quarter of the stroke the steam is thus used expansively, so effecting a considerable economy in steam consumption. Provision is made, however, by turning- round the caps covering the end of the main valve for admitting live steam during the entire stroke, as, when the pumps are starting and the metal is cold, the steam condenses and it is necessary to clear out the chambers of water. These caps are turned by means of the gun-metal spindles with indicating pointers at each side of the steam-valve chest. When the pump is fairly started, these bye-passes — one for the up stroke and one for the down — are closed till the pump is working silently. The main and auxiliary valves are practically the only two moving parts in the valve chest. The stroke can be adjusted while the pump is working by the nuts on the valve spindle in accordance with the centre punch marks on the front stay, and is constant." Messrs. Weir give the following particulars of two trials of one of their boiler feed pumps having a. steam cylinder Sin. diameter, pump 6 in. diameter, stroke 15 in., double acting : — Steam pressure at pump 1101b. ... 1071b' Water pressure at pump 164K>. ... 164 lb- Revolutions (or double stroke) p>er minute 15'!* ... 6 Efficiency of pump S7'25% ••• 96'6% Pounds of water delivered per p>ound of steam... S4"6 ... 55*3 Pounds of steam per net W.H.P i'3'l ... 95'3 Foot-pounds of work per B.T.U. to 212 deg 311 ... 21 It should be noted that the "efficiency of pump" in the above particulars refers to the relation between the actual volume of water delivered and the theoretical displacement of the water piston. Thus, in the first trial the " slip of the pump was 2'75 per cent, and in the second trial 3'1 per cent. The Pvlsometer Co.'s Compound Feed Pump. Fig. 00 is an illustration of a pair of " Karoome " compound feed pumps, constructed by the l'ulsometer 50 THE CONSTRUCTION AND WORKING OF PUMPS. Engineering Company Limited, of Nine Elms Ironworks, London, S.W. The makers state that these pumps can be worked with any pressure from 50 lb. to 350 lb per square inch, that the steam used is less than 50 lb. per duty horse power per hour, and that, despite the fact of the water being in many cases delivered at a pressure 50 per cent above the steam pressure, the diameter of the high-pressure cylinder is considerably smaller than that of the pump barrel. Bailey-Davidson Pumps. Fig. 31 is a sectional elevation representing the "Davidson " double-acting pump, by Messrs. W. H. Bailey and Company, of the Albion Works, Salford The steam chest of the Davidson pump is bored out to receive the slide valve, which has a curved face, and also the double-headed trunk piece which assists in oparating the valve. The valve is oscillated (for controlling the pressure on the trunk heads) by a cam arranged in the exhaust port, the rocking of the cam being effected by linkage worked from the piston rod as shown. The linear movement of the valve 52 THE CONSTRUCTION AND WORKING OF PUMPS. (for controlling the admission of steam to the cylinder) does not, however, depend entirely upon the steam admitted to the back of the trunk heads, for should that not be quick enough to operate the valve with the pump under a high rate of speed, the cam will itself carry the valve mechanically, and thus prevent the piston from striking the cylinder heads. This, the makers claim, is one of the most important features of the pump, the slide valve being as much under the control of the piston rod as is the valve of the ordinary steam engine worked by an eccentric, instead of being independently controlled by a trunk or like part operated only by the direct application of steam thereto, as is usual with many pumps of this class. Fig. 32 is an illustration of Messrs. Bailey's latest vertical type of high-pressure boiler feed pump for marine or land service. As will be seen, it is of very compact and simple design, and the whole of the working parts can be readily got at for inspection and renewals. Davidson steam pumps can be made with compound steam cylinders, and when required the makers also supply boiler feed pumps with triple cylinders. WORTHINGTON ADMIRALTY PATTERN PUMP. Fig. 3.3 illustrates one type or model of the Worthington Admiralty pattern pump. This vertical pump, suitable for marine and for land boiler feed service, for working pressures up to 250 lb. per square inch, has balanced piston valves at the steam end. Each of the water valves is contained in a separate chamber, and thus can be very readily inspected. As the whole of the valve chambers are located in front, the pump may be placed close against the bulkhead, no space being required at the back or sides for examination. The valves are so disposed in relation to the water cylinders that the pump readily frees itself of vapour when pumping hot water. Couplings are provided on the rods between the steam and water pistons, so that the latter may be taken out for examination without disturbing either the steam cylinders or the valve motion ; they also permit of the reduction of the head room required for drawing the steam pistons and rods. Two pumps of this type were employed worthingxon's ADMIRALTY pattern pump. 53 for feeding Babcock and Wilcox marine boilers at the recent Paris Exhibition. Pearn's Ram Pumps. Fig. 34 illustrates a single ram Cameron type pump by Messrs. Frank Pearn and Company Limited, of West Gorton, Manchester. As is usual with this type of pump, the columns supporting the overhead steam cylinder are made to act also as air vessels. But the pump illustrated has its ram packed under what is known as Pearn's patent system of packing, which the makers describe as follows : — "The illustration (fig. 34) shows the pump chamber in section. The ram A is "of the ordinary type used in double- 54 THE CONSTRUCTION AND WORKING OF PUMPS PEA UN'S HAM POMPS. 55 acting externally packed pumps, but made much shorter, as it works through one stuffing box only, instead of two, as in ordinary double-acting ram pumps. " B, the pump gland, is the novel feature in this packing, as it not only performs the ordinary function of a gland, but is in addition the pump chamber F for one side of the pump. The collar for taking the gland bolts is screwed on after the gland is iuserted through the top chamber F. C is the ordinary stuffing box, in which may be used spun yarn or any other packing. D is a joint ring to make a joint round the gland chamber B, and is slackened when the glaud is required to be moved. " The great advantages of this packing are, that a straight external packing is obtained in much less length than where two glands and stuffing boxes are used. All leakage is external, and shows at once when requiring re-packing. Leakage from pump chambers E to F is impossible. There is only one stuffing box ; this reduces friction and is less expense and trouble in packing. The glaud is guided at each end, and cannot be twisted by screwing one side harder down than the other, so any friction or wear due to such a cause is obviated.' Green's Ram Pumps. Fig. 35 is a sectional view through the cylinder and steam chest of a ram pattern boiler feed pump fitted with Balkwill's patent slide valve, as made by Messrs. E. Green and Sons Limited, of 2, Exchange Street, Manchester, and of Wakefield. In the ordinary single-acting ram pumps, although water is delivered only on the down or in stroke of the ram, live steam is supplied to each side of the piston. Messrs. Green state that the valve illustrated is the outcome of a series of experiments made at their Wakefield works, having for their object a reduction in the steam consumption of ram donkey pumps of the flywheel type, which force water at the forward stroke only. With a pump fitted with this valve live steam is only used during the downward stroke in pumping the water, and the exhaust from the upper side of the piston is utilised to lift r.f; THE CONSTRUCTION AND WORKING OF PUMPS. the "dead" ram during the upward or return stroke, and to overcome frictional resistance. The valve works on a cylinder face having four ports, one to the top of the cylinder, one for exhaust, and two to the bottom end. Live steam from the boiler is admitted to the top of the piston, cut off and expanded as in the case of a common slide valve, but at release, instead of the steam exhausting into the atmosphere or the condenser, both ends of the cylinder are put into communication for a short period, and then the ports at the bottom are closed, and the top opened to exhaust. In this way a portion of the steam used during the downward stroke passes to the bottom end of the cylinder, and on expanding performs work on the piston during the upstroke. In addition to economy of steam, the patent valve has another great advantage over the one ordinarily used for the purpose. With the latter the speed of the piston and ram during the upstroke is considerably faster than at the down- stroke, with the result that the pump valves are brought GREEN S RAM TUMPS. 57 too quickly down on their seats, thus causing unnecessary wear and tear ; whereas with the patent valve the speed of both strokes is much more uniform, and the pump w r orks •with greater steadiness. The following is a condensed summary supplied by the makers of tests made on two single-ram pumps, one fitted with a common slide valve, and the other with the Balkwill valve, but in all other respects similar in size and construc- tion. Dimensions of pump : Diameter of ram, 6 in. ; diameter of steam cylinder, 8i-in. ; stroke, Sin. Test No. 1. Ordinary valve. Duration of trial minutes Total number of revolutions Revolutions per minute Total weight in j ounds of steam entering cylinder Steam pressure on boiler side of starting valve, lbs. persq. in. Water pressure on delivery side . . . .pounds per square inch Total quantity of water pumped gallons Water delivered per pound of steam pounds Steam per I. H. P. per hour pounds Efficiency of purnp Economy in favour of new patent valve 42 per cent in steam consumption per I.H.P. During the tests the steam cylinders were not lagged, or in any way covered, to prevent condensation. It should be observed that the " efficiency of pump" in the above table is the relation between the water delivered and the theoretical displacement of the ram. Thus in the first case the "slip" of the pump is 13 per cent, and in the second ± per cent. In comparing the above record of tests with that supplied by Messrs. Weir of tests on their own pumps, and which we have given in the description of the Weir feed pump, it will 58 THE CONSTRUCTION AND WOEKIIfG OF PUMPS. be seen that in the later record the steam consumption is stated in terms of the water horse power, or the external or useful work done by the pump ; whereas in the former it is stated in terms of the indicated hoi'se power, or the work done in the steam cylinder. From the data given by Messrs. Green, we can, however, readily calculate the steam consumption in terms of the horse power on the water, or delivery, or output side of the pump. Thus, on referring to the table, we find that the pump with the ordinary valve delivered 44'7 lb. of water against a pressure of 123 lb. per square inch. Xow, taking the pressure at the base of a column of water 2 '3 ft. high to lie 1 lb. per square inch, it will be seen that the units of useful work accomplished by the expenditure of 1 lb. of steam is 447 x 123 x 2'3 = 12645'63 foot-pounds. Therefore, the steam consumption per pump or water horse power will be 33000 x 60 ,,„,, ; — = lob lb. per hour. 12645-6:! L In the same manner it will be found that the steam consumption per useful or water horse power in the pump, fitted with a Balkwill valve, works out as follows : 33000 x 60 .. ■— = 09 lb. per hour. 104-2 x 119 Messrs. Green also supply compound ram pumps with the Balkwill valve, and we understand that such a feed pump, with 6 in. and 8iin. steam cylinders, 6 in. stroke, and a ram 4 in. diameter, shows a steam consumption of but 44 '2 lb. per pump or water horse power per hour. MINE PUMPS. 59 CHAPTER VII. Mine Pumps. As is well known, the first steam pumping engine was the first practical steam engine of any kind. For though the force of steam was referred to by ancient writers long before the Christian era, and though the Marquis of Worcester thanked Heaven for showing him "so great a secret of nature, beneficial to all mankind," it was reserved for Thomas Savery, a Cornish mining captain, to do the thing of which others had dreamed and written. He built his first " fire- engine," as it was termed, for mine drainage, rather more than two centuries ago, in the year 1698. In the Savery engine — as with the modern form of such engines very largely and advantageously used under certain conditions at the present day — a vacuum is created in a closed pump chamber by the condensation of steam admitted within it. By the atmospheric pressure the water to be raised is then forced into the pump chamber, from which it is expelled on the nest introduction of steam, and caused, by the direct pressure of such steam, to flow up and out of the discharge or delivery main. In the Newcomen pumping engine, by which the Savery engine was superseded, the condensation of the steam necessary for the formation of a vacuum is effected in a cylinder and beneath a piston connected to a beam. The unbalanced atmospheric pressure on the top of the piston then effects the elevation of the opposite end of the beam with the pump rods and bucket for the formation of the vacuum within the pump chamber fixed down in the mine or pit, within suction distance of the water. The subsecpaent descent of the backet and the duly weighted pump rods effects the discharge of the water through the rising main to the pit bank. James Watt's improvements on the Newcomen pumping engine, comprising the formation of the vacuum in a separate vessel (the condenser), the introduction of the air pump to improve the vacuum, the use of steam instead of atmo- spheric pressure on the upper side of the piston, the steam jacket, and other well-known features, need no description. 60 THE CONSTRUCTION AM) WOttKING OF PUMPS. The Saverv pumping engine had of necessity to be placed bodily in the pit and within suction lift of the surface of the water to be raised. But with both the Newcomen and the Watt pumping engine there is a distinct and widely separated "steam end'' and ''water end," the former (or the engine proper) being arranged at the surface, whilst the latter (or the pump proper) must be fixed in the mine or pit. In modern mine pumps we have, in the more general and ordinary practice, a steam and water end arranged to form the one complete machine, which, like the Savery engine, is placed entirely in the pit. But before proceeding to consider various types of modern mine pumps we will here refer to the Duty of Mine Pumps. For the purpose of comparing his engines with the best work obtainable from horses, James Watt fixed upon the unit mechanical horse power (33,000 ft. -lbs. per minute), which soon became and remains the recognised British standard. In like manner, to enable the mine owners to appreciate what he proposed to do fur them, he expressed the capability of a pumping plant (including both the pumping engine and boiler) in terms of the number of millions of foot pounds of work that could be performed by the expenditure of 1 cwt. of coal. The following particulars concerning the performances of ancient and modern pumping engines appeared in "Engineering" in the issue of Jane 15th, 1894 : — Savery engines 5,000,000 ft. -lbs. per cwt, of coal. Xewcomen engines 12,000,000 ft. -lbs. per cwt. of coal. Watt engines 80,000,000 ft, -lbs. per cwt. of coal. Present day (ordinary).. 120,000,000 ft.-lbs. per cwt, of coal. Present day (special) ... 152,630,000 ft.-lbs. per cwt. of coal. The last-named result, obtained with a pumping engine at Chicago, was, in the year 189-1, considered a record for actual commercial pumping. It appeared, however, that the work done was that measured in the steam cylinders, instead of the actual or pump horse power on the delivery side, as is usually taken, and which, of course, is less than the DUTY OF MINE PUMPS. 61 indicated horse power by the amount absorbed in overcoming the Motional resistance of the engine itself. But taking the figures as they stand, it will be seen that with the Savery engine the expenditure of coal per horse power per hour was — 33000 x 60 5000000 112 = 44-311.. With the last result given on list the coal consumption per horse power per hour works out as follows : 33000 x 60 , , „ , . K ,, <■„„- x 112 = T45 lb. 152630000 In comparing these results with those obtained with other engines, running, it may be, at high speeds, and with the boilers and the whole plant specially arranged for the attainment of exceptional results, it must be borne in mind that the comparatively slow speed at which pumping engines are generally run is not conducive to great economy in steam consumption. "We shall return again to the question of the results actually obtained from pumps, but we may here consider for a moment the total amount of heat energy available from the combustion of 1 cwt. of coal. The standard calorific value or the total heat of combustion of 1 lb. of best steam coal is generally taken at 14,700 British thermal units. The mechanical equivalent of one British thermal unit being taken at 772 foot-pounds, it follows that if the whole of the heat energy could be converted into useful work the quantity of coal required per horse power per hour would be — 33000 x 6 0^ =0 . 1751b- 14700 x 772 Thus the burning of but one pound of coal would yield nearly 6 horse power for one hour. Types of Mine Pumps. It has been well said that " it is very difficult to design and construct a steam pump that will satisfactorily meet the exacting requirements of mine pumping. The service <)2 THE CONSTRUCTION AND WORKING OF PUMPS. DOUBLE ACTING RAM TUMPS. 03 is generally rough, severe, aud continuous. Great care must be exercised both in the selection and adaption of the material used in construction, as the water to be pumped is often of a kind that will attack and quickly destroy it. The location of the mine is usually remote from supplies, and any necessity for renewals or repairs, unless they can be made with unskilled labour and with little delay, may be attended with serious consequences." Peakn's Compound Ram Pumping Engine. Fig. 36 illustrates the above-named crank and flywheel pump by Messrs. Frank Pearn and Co. Limited, of West Gorton, Manchester, suitable for use in collieries as an under- ground pumping engine. As will be seen, the external stutfmg boxes of the rams can be readily packed, and all parts are easily accessible. The pump valves are of gun metal, and each is accessible by a separate door or cover. The cylinders and pump end are fitted on the one base plate, ensuring the maintenance of accurate alignment of the working parts. Evans' " Cornjsh " Double-acting Ram Pumps. Fig. 37 is an illustration of the above-named pumps as made by Messrs. Joseph Evans and Sons, of Culwell Works, Wolverhampton. The "Cornish'' steam cylinder, as it is termed, which is adopted by Messrs. Evans for this and many other types of their pumps, is provided with a steam- operated controlling valve, but no tappets (or supplementary stalk valves which the main piston must operate on each stroke), are necessary, as with some other types of steam moved valves, and which are objectionable because of their liability to become stuck up or inoperative. Small ports are provided at each end of the cylinder which communicate with the back of a small plunger, working in a larger plunger arranged in the valve chest. As the main piston approaches the end of its stroke in either direction it uncovers one of the said ports to allow steam from the cylinder to act upon one end of the small plunger, and so move the same as to put the opposite end of the larger plunger in communication 64 THE CONSTRUCTION AND WORKING OF PUMPS. EVANS CORNISH DOUBLE-ACTING RAM PUMPS. 65 with the exhaust, and the adjacent end with the live steam in the valve chest. The large plunger, together with the slide valve, is thus carried over the main ports, thereby reversing the motion of the piston within the cylinder. The steam chest being placed on the side of the cylinder, and the bottom of the steam port on the same level as the bottom of the cylinder, the makers state that the whole of the condensed steam is carried out at every stroke of the piston, whereby the necessity for drain cocks is avoided. The pump end, as will be seen from the illustration, is provided with a ram working through a pair of stuffing boxes •arranged in separate chambers. As there is a suction in one chamber and a delivery from the other, a double action is 5c p 60 THE CONSTRUCTION AND WORKING OF PUMPS. obtained on every stroke of the single ram. The illustration shows both an air vessel on the delivery side and a vacuum chamber on the suction side. Though Messrs. Evans can also make this type of pump, with a piston or bucket in place of the outside-packed ram, as illustrated, their recommendation is in favour of the latter, and they do not in any case advise the adoption of a piston or bucket pump for a waterhead of m;>re than 300 ft, EVANS' HYDRAULIC OR WATER MOTOR POMP. 67 on account of the loss of efficiency due to slip, which may become very great before detection when working with an internally-packed piston. Evans' Duplex Pumping Engine. This pump is illustrated at fig. 38. The water end com- prises externally-packed rams with central stuffing boxes and cylindrical valve chambers, each valve having its own chamber. A sectional view through a pair of the valve boxes or chambers (one section and one delivery) is given at fig. 39. The slide valves at the steam end are operated under the well-known duplex-lever system. Evans' Hydraulic Water Motor Pump. This pump (illustrated by fig. -40) is constructed for working by water instead of steam. By utilising the motive power of a given head of water, a larger quantity of water may be thereby pumped to a relatively less height, or a relatively less quantity of water may be pumped to a greater L WORTHINGTON MINE PUMPS. 69 height than the head of motive column working the pump. It has been specially designed and constructed for draining " dip" workings in mines or collieries, and it will work quite satisfactorily when entirely submerged by water. The makers state that they " supply these motors chiefly for underground use, in mines where water has to be pumped up from dip workings to the shaft bottom, and they are found to be very convenient for the purpose." They farther state : " We have frequently applied these motors in positions where the water pipes have had to be carried 500 or 600 yards to the pumps, and we have them working in some cases under high pressures, up to nearly 2,000 feet head ; on the other hand, we have also applied them in cases where the head of water to drive them has been as low as 25 ft,, and forcing against a head of 300 ft. or 400 ft. During the colliery strike in the County of Durham, some years ago, a number of these pumps were left working down the pits for a period of three months ; the water rose over them from various causes, chiefly because the main pumping engines were not kept regularly at work, but they still con- tinned to work alone, and when the strike was over and the main engines set going these motors pumped themselves out." Worthington Mine Pumps. The Worthington compound mine pump, illustrated at fig. 41, is of the externally packed plunger or ram pattern. The two rams at the water end of the pump work through central stuffing boxes, as illustrated, into four separate and distinct water chambers, any one of which can thus be renewed. Pumps of this pattern are designed to safely withstand a working pressure of 300 lb. to the square inch, and the makers state that all the attachments are especially strengthened with a view to meeting the rough usage and hard work to which, in mine service, they are liable to be subjected. Fig. 42 illustrates the Worthington triple-expansion mine pump (pressure pattern). This pattern is designed for use in cases where the head to be pumped against exceeds 300 lb. per square inch. The sub-division of the parts at the water WORTHINGTON MINE PUMPS. 71 end is carried still further in this type, for, as will be seen, iu addition to the construction of two part pump chambers with flange joint connections, the valves are arranged in a series of valve boxes or pot chambers. Each box contains one or more small valves having a low lift, and which are easily accessible by screwing back the nuts on the eye bolts and removing the box covers. Special features in this pumping engine are the patented method of connecting the three steam pistons, and the semi-rotative or Corliss-type valves. Fig. 43 is a vertical Fig. 44. longitudinal section through one side of the steam end of the° engine, and tig. 44 a horizontal longitudinal section of the same showing the arrangement of the piston rods. Each cylinder is provided with a single valve placed centrally beneath it, but the high-pressure cylinder has, in addition, a pair of adjustable cut-off valves. The valves serve to drain the cylinders, and by their own weight and 72 THE CONSTRUCTION AND WORKING OF PUMPS. the pressure of steam on the unbalanced area, the valves are kept steam tight, and are free from the tendency t.o fall away from their seats which exists when inverted valves are employed, as is generally the case if they are placed beneath the steam cylinders. The two high- pressure cylinders (one on each side) are bolted directly to the cradles of the pump, with the intermediate cylinders next, but there is an intervening space between the adjacent covers of the high and intermediate pressure cylinders. The low-pressure cylinders are bolted directly to the intermediate cylinders, and are thus at one extreme end of the pump or pumping engine. The high-pressure piston rod is coupled directly to the pump rod. Between the high-pressure cylinder and the pump end there is a crosshead to which are attached two side rods connecting to the low-pressure piston, whilst the latter is connected by a central rod with the intermediate piston ; the said central rod works through a long metallic sleeve made an exact fit to the rod, whereby the use of a stuffing box is avoided. The makers claim the following advantages for their method of connecting the pistons : — 1. In this construction each of the three pistons and the interior of the cylinders are accessible by removing their respective cylinder heads, and each of these heads may be removed readily and without any interference with any piston rod or stuffing box. 2. That as each of the pistons is carried at the end of its rod, they may all be removed by simply slacking off their respective nuts. 3. In this construction the use of keys in the cylinder may be entirely avoided, and the effective area of the smaller pistons need not be reduced by rods larger than sufficient to carry their respective individual loads. 4. The direct course of steam between the high pressure and intermediate and low pressure cylinders in the order of expansion is retained, and in case of repairs, either the intermediate or the high pressure pistons and valves, or both, or the low pressure valves, can be removed and the engine run with the remaining cylinders or cylinder. In the construction of their triple expansion pumps such BANK OR SURFACE ENGINE FOR MINE PUMPING. 73 as illustrated, the usual practice of the Worthington Pumping Engine Company is to tit the low pressure cylinders with dash relief valves to regulate the length of stroke of the engine, and to steam jacket the intermediate and low pressure cylinders. With regard to economy the makers give the steam consumption of their triple expansion condensing mine pumps at about 22 lb. per useful or pump horse power per hour. Arrangement of Condensers in Mine Pumps. With pumps fixed in underground workings it is in man} r cases necessary to employ a condenser if only for the purpose of disposing of or " killing " the exhaust steam. For some services an air pump condenser either arranged independently or worked from the pump itself may be adopted. But it is frequently more convenient and sometimes essential to employ a surface condenser. In the water passing through the pump we have an ample supply of the condensing medium available. The surface condenser can be arranged either on the suction or the delivery side of the pump, so that the water flowing into or from the pump during its working is caused to pass through the condenser. The steam is thus effectually disposed of, and at the same time a vacuum is produced resulting in economical working of the plant. An air pump will be necessary and this may be either worked independently or be attached to and worked by the main pumping engine. Bank or Surface Engines for Mine Pumping. Both rotative and non-rotative pumping engines fixed at the ground level are employed for mine pumping. Of the former type the oldest and best known is the "Cornish." The name " Cornish," which is in these days adopted for quite small direct-acting non-rotative or non-flywheel pumps, was originally applied to the single-acting pumping engine invented and introduced by James Watt and his associates as an improvement upon the Newcomen. It comprises, as is w r ell known, a single cylinder containing a piston connected 74 THE CONSTRUCTION AND WORKING OF PUMPS. SURFACE PUMPING ENGINES. 75 to one end of an overhead beam ; to the opposite end of the beam the weighted pump rod is connected. The steam pressure acting upon the upper side of the piston raises the rods, whilst by the descent of the latter the water is forced through the rising main and the piston drawn to the top of the cylinder in readiness for the next cycle of operations. Such engines are still constructed, and by compounding Mr. Henry Davey (of Messrs. Hathorn Davey and Company of Leeds) states that he has successfull} 7 employed a steam pressure of 1501b. per square inch for working a Cornish engine. Fig. 45 illustrates a small mine pump or well pump, as made by Messrs. Frank Pearn and Co. Limited, of West Corton, Manchester, having the steam motor or engine at the ground level directly connected with the pumps fixed in the well or pit. The engine is of the " Cameron " type, whilst the pumps, which have externally packed rams, can be so arranged that their rods are in tension (instead of in compression, as is usual) during the delivery of the water. An old non-rotative type of mine pump is the "Bull" engine, in which there is no overhead beam, the cylinder at the bank or surface level being placed directly over the pump proper in the mine ; the piston rod can thus be directly connected to the pump rod. The system of work- ing, or the cycle of operations, is the "Cornish." Modern surface engines of the non-rotative type for mine pumping are frequently arranged horizontally, the motion of the piston being transmitted through a rod to one end of a rocker, angle bob, or quadrant pivoted adjacent to the pit, and having the rod from the pump fixed below connected to its opposite end. In the Davey pumping engine a pair of quadrants or angle bobs working separate pumps are employed, and these are so coupled together that the one serves to balance the other. Sinking Pumps. Sinking pumps for suspending in a shaft during construc- tion, for recovering flooded mines, and for similar services are made by most large pump makers. Such machines 76 THE CONSTRUCTION AND WORKING OF PUMPS s / % SINKING PUMPS. 77 must be very compact in design so that the space occupied shall be reduced to a minimum, and capable of withstanding the very rough handling they are sure to experience in service. Fig. 46 illustrates a differential ram (outside packed) sinking pump by Messrs. Joseph Evans and Sons, of Wolverhampton. A sectional view of the water end of 47. such a pump is given at fig. 47. The differential ram acts in the same way as the well-known bucket and plunger, or ram and bucket pump, in that although the pump is single acting on the suction side, it is double acting on the delivery side, for there is a discharge on each stroke. On the up or suction stroke of the ram the amount of water flowing into the lower pump chamber through the suction valve equals 78 THE CONSTRUCTION AND WORKING OF PUMPS. the area of displacement of the larger end of the ram. On the down stroke this water is displaced from the lower chamber and forced through the delivery valve into the upper chamber, where the displacement equals only the difference between the areas of the two ends of the ram, such difference being usually equal to one-half the area of the larger end, or one end of the ram has twice the cross sectional area of the opposite end. Thus one-half of the water is discharged from the upper chamber on the down stroke, and the other half on the up stroke of the ram, and the work is thereby equalised as in a double-acting pump. The pump illustrated is suitable for heads up to 600 ft., and the steam cylinder for steam pressures up to 1001b. per square inch. The valve motion at the steam end is the Evans' and Tonkins' Patent as previously described in connection with another pump by the same makers. CHAPTER VIII. Hydraulic-pressure Pumps. Hydraulic machinery may be worked with a pressure of but a few pounds, or as many tons per square inch. But the term "pressure pattern" or "hydraulic pressure" is not generally applied to pumps working at pressures under 2001b. per square inch. Pumps working at pressures of from 1 to 3 tons are generally described under the class or heading of "high-pressure hydraulic machinery." A greater intensity of pressure than 3 tons per square inch is seldom adopted in practice, owing chiefly to the cutting or erosive action of the water, due to the enormous velocity at which it will be propelled by such a pressure through the valve apertures and connections. When it is remembered that a pressure of 3 tons per square inch will produce a velocity of about 1,000 ft. per second, or 11 miles per minute, there will be no difficulty in appreciating the importance of keeping the water quite clean in high-pressure HYDRAULIC PRESSURE PUMPS. 70 hydraulic work. The presence of grit will set up a most destructive sand-blast action as the water rashes through the valve ports and the connections generally. And it must also be remembered that where cylinders are employed, having a great thickness of metal to resist the high pressure within, the stress is not equally distributed, for the metal nearer to the interior will bear a greater proportion of the load than that at the exterior. Cylinder castings, because Fig. 4S. of such unequal distribution of the stress set up by the internal pressure, have been known to fail by the gradual crackino- of the metal from the interior towards the exterior. When high pressures are employed only a very moderate quantity of water is usually required, and the cylinders and rams or plungers at the pump or water end of a steam pumping engine for such hydraulic services are, therefore, of but small dimensions. It may be, indeed, that the rams 80 THE CONSTRUCTION AND WORKING OF PUMPS. are so small as to render it somewhat difficult to provide sufficient rigidity, and to effectually pack the glands through which they work. A differential ram, such as illustrated in the sectional sketch diagram at tig. 48, may then be advantageously adopted. As will be seen, the ram has two diameters, so that on its up stroke, or its movement in the direction indicated by the arrow, a vacuous space is formed in the cylinder, and the water thus enters through the auction connection a ; whilst on the down stroke there is a corresponding displacement, whereby water is forced out from the cylinder through the delivery connection b. Both the suction and delivery connections are, of course, provided with suitable valves. With onlv a small difference in the LTT areas of the respective ends of the ram, there will be but a small discharge on each pump stroke, and thus we can provide ample cross-sectional area throughout the ram to resist any desired intensity of pressure, without affecting the quantity of water delivered. Fig 4'J is a sketch diagram of the ram and piston type of water end frequently employed in rotative hydraulic pumping engines, for the purpose of obtaining the advantages of the equalisation of the work, and a steady flow resulting from a double action on the delivery side, with the simplicity of a single action on the suction side. The same result is thus obtained as with the differential ram sinking pump, illustrated at fig. 47 in our last article. The piston must, of course, lie packed wilh hemp or the like, or with self- acting leathers. Our fourth chapter contains some particulars concerning packing. pearn s hydraulic pumping engines. 81 Pearn's Hydraulic Pompikg Engines. Figs. 50, 51, and 52 illustrate three types of hydraulic pumping engines, as constructed by Messrs. Frank Pearn and Co. Limited, of West Gorton, Manchester. In the type illustrated at fig. 50 there are three single- acting rams, each of which is directly connected by a yoke piece to the piston rod of the steam cylinder mounted above it. The crank shaft, which operates the steam slide valves, is driven from the yoke after the manner of the " Cameron " type boiler feed and general service pump. The makers give the following description : — ''This type of pump is largely used for working accumu- lators, etc. Having three rams, the delivery is very continuous when working direct without an accumulator. It is very suitable for presses, cranes, hoists, lead presses, ■etc., ifec. It is made in several sizes to work at pressures from 7001b. upwards. It is very compact, and all parts are easily accessible. The crank shaft is made of forged steel, anil works in gun-metal bearings, all adjustable ; the connecting rods are of best hammered iron, and are fitted with gun-metal bearings at each end, all adjustable." The horizontal type rotative or flywheel hydraulic pump- ing engine, illustrated at fig. 51, affords a practical example of the ram and piston type. The makers give the following description : — " This pumping engine is designed for working hydraulic presses, hoists, cranes, winches, capstans, &c, either direct or in connection with an accumulator. It is made in numerous sizes, either high pressure, compound, or con- densing, and to work against pressures up to 1,0001b. per square inch. The pumps are single acting on the suction, and double acting on the delivery. They are brass lined, and fitted with gun-metal pistons with cup leathers." Fig. 52 is an illustration of a hydraulic ram type pumping engine, suitable for very high-pressure work. Each pump or water end is provided with a pair of rams which are single acting, but being coupled together by outside rods, and" yoked to the one piston rod, a double action is obtained, for there is both a suction and a delivery action on each Gcp Fig. 50. PEAKN'S HYDEAULIC PUMPING ENGINES. 83 84 THE CONSTRUCTION AND WORKING OF PUMPS. stroke of the steam piston. The complete engine is made up of two steam cylinders, each connected with a water end carrying two rams. Thus on each revolution of the crank shaft we have four suction actions and as many deliveries, or in other words, we have a four-throw pump action ensuring a continuous flow through the discharge pipe. The makers give the following description : — "This is a very high-class type of engine, specially designed for high speeds and heavy pressures up to three tons per square inch. The pumps are made of solid forged steel ; all the passages, valve chambers, and pump barrels are bored out. The rams are made of phosphor bronze ; they are outside packed, of easy adjustment, and supported at each end by suitable crossheads. The steam cylinders are cleated with sheet steel, and fitted with sight-feed lubricators, steam stop valve, and drain cocks. The engine can be worked either direct or through an accumulator." Rice and Co.'s Hydraulic Pumping Engine. Fig. 53 is an illustration of a rotative hydraulic pumping engine, as constructed by Messrs. Rice and Co. (Leeds) Limited, of Neville Works, Elland Road, Leeds. The makers give the following description : — " The illustration shows our standard type of steam- driven pumping engine, driving direct on to four single- acting pump rams. These engines are strongly constructed to suit the heavy and continuous work they have to do. They are provided with ample bearing surfaces throughout, so that they run very smoothly, and the wear is inappreci- able. The bed plate is an iron casting of strong section, having the crank-shaft bearings cast solid with it, and for convenience of transport the larger sizes are made in halves, which are tongued and bolted together, making a very rigid connection. The crank arms are of mild cast steel, shrunk and keyed on to a forged steel shaft running in phosphor- bronze bearings. The crank-shaft bearings are made adjustable in the horizontal direction. The connecting rods, valve spindles, etc., are of mild steel. The cylinders are of hard close-cast iron, and the pistons are packed with cast- peaen's hydraulic pumping engine. 85 80 THE CONSTRUCTION AND WORKING OF PUMPS. iron rings and Oldham's patent steel spiral coils. The pump bodies are of a very strong mixture of cast iron, and are fitted with phosphor-bronze glands and bushes. The valve and valve cases are of phosphor bronze, and made with good free openings for the suction and delivery. These engines are controlled by a Porter loaded governor, which is coupled to the equilibrium valve lever. This lever is arranged so that, when pumping into an accumulator, the accumulator can be connected to it in such a way that the engine is stopped as soon as the loaded ram reaches the top of its stroke, and started again as soon as the ram begins to descend, thus keeping the supply of water completely under control and economising steam. The cylinders are covered with cold-rolled steel sheets, and fitted with drain cocks and lubricators, and the whole engine is well finished throughout. The pumps are supplied complete as shown, and are made suitable for a working pressure of 1,5001b. per square inch (100 atmospheres), but can also be made for am r working pressure required." WoRTHINGTOX HYDRAULIC Pl'MP. The non-rotative hydraulic-pressure pump, or pumping engine, as constructed by the Worthington Pumping Engine Company, is built on similar lines to the triple-expansion mine pumping engine by the same makers, described in our last chapter, and illustrated by the fig. 42 therein. Each pump or water end is provided with a pair of externally- connected rams, and with separate chambers for the valves. The engines are supplied for services up to 8,000 lb. (about oh tons) per square inch, and with simple, compound, or triple-expansion steam cylinders. Worthington hydraulic-pressure pumps are for certain purposes sometimes bolted directly to a steam accumulator. The accumulator consists of an ordinarv steam cylinder (such as would be used in a steam engine, but without the usual ports or valves), combined with a ram cylinder similar to that of a weighted accumulator. But no weights are employed, as the steam pressure acting on the piston within the first-named cylinder imposes the desired force on the ram, the latter being securely bolted to the piston. 8H THE CONSTRUCTION AND WORKING OF PUMPS The makers state that " the advantage of this accumulator over the ordinary weighted accumulator can be readily understood. The most important and marked difference is in the effect on the water pressure. The steam accumu- lator is not subject to the tremendous shocks and jars due to the momentum of the weights of the weighted accumu- lator. The moving parts of the steam accumulator are so light that momentum is not a factor. The machine is very sensitive, and the variations of the water pressure very slight. The steam accumulator can be adapted to any space, as it can be placed either horizontally or vertically, and as it is not heavy it can even be hung from roof beams if necessary.'' The makers further state that Worthington combined steam pumps and accumulators, as aforesaid, have been extensively used on the cruisers and battleships of the United States for general hydraulic service and for working the gun carriages and turrets. CHAPTK.il IX. Modern Savery-type Pumps. IvEPERENCE was made, in our article dealing with mine pumps, to the original Savery pumping engine of the year lf>98, in which the steam is employed for the creation of a vacuum in the pump chamber, and by its contact with and direct pressure on the water, subsequently entering the chamber, for forcing such water through the delivery or rising main. In the original Savery engine the condensation of the steam within the chamber was effected by the application of cold water to the exterior of the vessel, but in the modern form the water passing through the pump is the condensing medium. There is, therefore, no exhaust steam to lie dealt with, either in the original or the modern Savery engine. The Savery -type engine, as now made, is known by various fanciful names, and is sometimes described as pistonless, as THE PULSOMETER. 89 pulsating, and as a steam vacuum pump. But as pumps of a totally different type may have the same descriptive terms applied to them, the appropriation of such terms by makers to a particular pump of their own is productive of consider- able confusion. Just as "Otto-type" is the recognised name for gas engines working on the cycle originated by Dr. Otto, so should the type of pump in which the steam for performing the work is admitted into the pump chamber itself, to act directly upon the water, be associated with the name of the Cornish mining captain by whom it was invented and first applied more than two centuries ago. We give hereunder some particulars of the various forms of the Savery-type pumps, under the names and with the aid of the descriptions and illustrations supplied by the makers themselves : — The Pulsometek. A sectional view of this well-known pump, made by the Pulsometer Engineering Co. Limited, of Nine Elms Iron- works, London, S.W., is given at tig. 54. The makers describe it as consisting " of a single casting called the body, which is composed of two chambers A A joined side by side, with tapering necks bent towards each other, and surmounted by another casting called the neck J accurately fitted and bolted to it, in which the two passages terminate in a common steam chamber, wherein the ball valve I is fitted so as to be capable of oscillation between seats formed in the junction. Downwards, the chambers A A are connected with the suction passage C, wherein the inlet (a- suction valves E E are arranged. A discharge chamber, common to both working chambers, and leading to the discharge pipe, is also provided, and this contains one or two valves F F, according to the purpose to lie fulfilled by the pump. The air-chamber B communicates with the suction. The suction and dis- charge chambers are closed by covers HH accurately fitted to the outlets by planed joints, and readily removed when access to the valves is required ; in the larger sizes hand- holes are provided in these covers. GG are guards which control the amount of opening of the valves E E. Small air-cocks are screwed into the cylinders and air-chamber, for 90 THE CONSTRUCTION AND WORKING OF PUMPS. THE l'ULSOMETEE. 91 use as will be hereafter described. These are the general outlines of the construction of the apparatus, and they are sufficient for the understanding of the nature of its operations. •'The pump being filled with water, either by pouring the same through the plug-hole in the chamber, or by drawing the charge, as can readily be done by attention to the printed directions, is ready for work. Steam being admitted through the steam pipe K (by opening to a small extent the stop-valve), passes down that side of the steam neck which is left open to it by the position of the steam ball, and presses upon the small surface of water in the chamber which is exposed to it, depressing it without any agitation and, consequently, with but very slight condensation, and driving it through the discharge opening and valve into the rising main. ''The moment that the level of the water is as low as the horizontal orifice which leads to the discharge, the steam blows through with a certain amount of violence, and being brought into intimate contact with the water in the pipes leading to the discharge chamber, an instantaneous condensa- tion takes place, and a vacuum is in consequence so rapidly formed in the just-emptied chamber that the steam ball is pulled over into the seat opposite to that which it had occupied daring the emptying of the chamber, closing its upper orifice and preventing the farther admission of steam, so allowing the vacuum to lie completed ; water rashes in immediately through the suction pipe, lifting the inlet valve E, and rapidly fills the chamber A again. Matters are now in exactly the same state in the second chamber as they were in the first chamber when our description commenced, and the same results ensue." The makers farther state that the "change is so rapid that, even without an air vessel on the delivery, but little pause is visible in the flow of water, and the stream is, under favourable circumstances, very nearly continuous. The air-cocks are introduced to prevent the too rapid filling of the chambers on low lifts and for other purposes, and a very little practice will enable any unskilled workman or boy so to set them by the small nut that the best effect may be produced. The action of the 02 THE CONSTRUCTION AND WORKING OF PUMPS. THE PULSOMETER, 93 steam ball is certain, and no matter how long the pump may have been standing, it will start as soon as dry steam is admitted.'' In the illustration at fig. 54 the pump is shown fitted with grid valves having rubber discs. For services where the action of the water to be pumped is detrimental to rubber, the makers employ clack valves consisting of a hinged iron plate or body with hickory seats, though it is to lie noted that such valves are somewhat noisv. Fig. 55 is an external view of a later type pulsometer, having hinged doors to allow of more ready and convenient access to the valves. For attaining a more economical use of the steam the Pulsometer Company arrange their " Grel " cut-off valve at the upper end of the pump. A sectional illustration of the upper end of a pulsometer fitted with a Grel valve is given at fig. 56. The makers thus describe the arrangement: — "The operation of the combined valve is as follows: Commencing at the moment when the left-hand chamber D 94 THE CONSTRUCTION AND WORKING OF PUJIPS. is full of water, and the distributing valve C has moved to close the right-hand chamber E and open the left-hand chamber D, the expansion valve being open, the full steam pressure enters the left-hand chamber D and partially empties it. Daring this time, steam has been entering the special chamber F through the orifices G and G 1 , thereby increasing the pressure therein, and as the water in the body of the pump falls there is a reduction of pressure without this chamber, the effect of which is to cause the movable part F of the expansion valve to rise and cut off the steam by closing the steam pipe. The expansion of the steam and the expulsion of the water continues until the chamber is nearly emptied, when the difference of pressures in the pump chambers brings over the distributing valve C. By this time the escape of the steam from the chamber F permits the pressure of steam in the steam pipe B to depress the movable part of the valve, and the steam rushes in to expel in turn the water which has flowed into the right-hand chamber during the emptying of the left-hand chamber, the correct working of the valve depending on the proper manipulation of the regulating screws." The " Aqua-Thrusteh." Fig. 57 represents an external view, and fig. 58 a sectional view, of this pump, which is made by Messrs. W. H. Bailey and Co. Limited, of Albion Works, Salford. As will be observed, the spherical or ball valve for controlling the admission of steam in the pump last considered is in this machine replaced by a rocking plate or disc. In connection with the sectional vie\v, the makers suppl} T the following description : — " The left-hand chamber is filling whilst the right is being emptied by the steam which is being admitted by the valve in the head of the pump. By the time the right-band chamber is emptied the left one has filled ; the valve is drawn to the right, and the steam now forces the water out of the left-hand chamber and through the delivery valves, and water rushes into the right-hand chamber through the suction valves." Fig. 57 THE "fLUOMETEE." 97 In their trade lists, the makers give the capacity of their pumps in the number of gallons of water lifted a total height of 32 ft. with 60 lb. steam pressure per square inch, stating, however, that a lesser quantity can be raised to such a height with 251b. to 30 lb. steam pressure. The "Fluometer." This pump, by Messrs. Joseph Evans and Sons, of Wolver- hampton, is illustrated in its original form at fig. 59. Fig. 60 is a sectional view of a later pattern. In this pump the steam controlling valve is dispensed with. A is the working chamber, B the suction, and C the delivery valve. The action is described as follows : — '• The steam flowing in through the steam pipe depresses the water in the working chamber A, driving it through the delivery valve C, and up the delivery pipe ; this is done without disturbance of the level, consequently the top layer of water in immediate contacr, with the steam becomes heated, and by reason of its specific gravity remains at the top, thus preventing further condensation, a portion of the water passing into the injection chamber E through the inlet K, where it remains under a pressure equal to that in the working chambers. In this manner the water level falls uutil it arrives at the off-set J, when a violent disturbance takes place, and a reduction of pressure is in consequence brought about. The injection water now rushes in from the chamber E, and completes the vacuum, causing a fresh supply of water to enter from the suction pipe. The inrush of the suction water is so violent that it is necessary to restrict the passage way into the pump at the lower extremity of the working chamber and to take in a small amount of air through the snift valve G. This air serves the double purpose of cushioning the flow of the water, and, in subsequently mingling with the steam, prevents con- densation of the latter by reason of its low couductivity. The working chamber A being now filled again, the action is repeated as long as the steam remains on and there is water to pump." 7cp 08 THE CONSTRUCTION AND WORKING OF PUMPS. Steam Consumption in Savery-type Pumps. The great advantage of these pumps is their extreme simplicity of construction and their general handiuess. They will work as well hung from a chain as if permanently fixed, and pump mud, slurry, and water containing a con- siderable quantity of solid matter, such as would quickly &EIL.LVERY |'| 1 ISI a fig g 1 1 liiia llggpj III l, , «KPlfw^ render useless the wearing parts of other pumps. As a set- off against this, we have what is sometimes referred to as thej " steam-eating " power of these pumps. But though STEAM CONSUMPTION IN SAVERY-TYPE PUMPS. 99 they undoubtedly have a considerable appetite, the steam consumption of Savery-type pumps is not so enormous as is sometimes assumed, and indeed, under certain conditions, they will compare favourably in this respect with ordinary wmzzmIzmm pumps in which pistons and rams or plungers are interposed between the steam and the water which it raises. Preference was made in au earlier article to a paper read before the Institution of Mechanical Engineers in 1893, by 100 THE CONSTRUCTION AND WORKING OF PUMPS. Mr. A. Borodin, on the working of steam pumps in Russia. The author of that paper gives particulars of a test of a small Savery-type pump (of less than one-half actual horse power) showing a steam consumption of 860 lb. per pump or useful horse power per hour, or 2,300 foot-pounds per pound of steam. In the discussion on the paper, one member gave the steam consumption, obtained by a rough calculation from the performance of a Savery-type pump he had employed, as 4,300 foot-pounds per pound of steam, which is equal to 460 Hi. of steam per pump horse power per hour. From a test by another member, a steam consumption of 306 lb. per useful horse power per hour was given by a pump discharg- ing 70,000 gallons per hour. But from the result (also presented during the discussion) of a trial made by Professor T. H. Beare, on behalf of the Pulsometer Company, with a pulsometer fitted with the Grel controlling valve, a con- sumption of but 1481b. of steam per horse-power hour was obtained, or 13,415 foot-pounds of work done per pound of steam consumed. The conditions under which the test was made were described as follows : An unlagged vertical boiler standing in an open yard, and an unlagged steam pipe 62 ft. 'ong to the pulsometer ; mean boiler pressure 55 lb. per square inch, feed water supplied 361 lb. per hour; measured height of lift 73 ft., or by pressure guage 84'4 ft., including friction. The water pumped w r as 5,738 gallons per hour, which, against the head of 84'4 ft., represented 2'45 horse power. The Jesuits given above should be compared with the particulars we have previously given concerning the steam consumption of pumps of the boiler-feed type. It will be found that the pulsometer working expansively, as described, compares very favourably with many of such pumps. POWER PUMPS. 101 CHAPTER X. Power Pumps. The operation of every pump is effected by the application of a power or force of some kind, but the term " power punip " is employed both in this country and in America as descriptive of a pumping machine which is driven through belting or through gearing, or both. We have previously considered self-contained pumps, or pumping engines as they should properly be termed, in which the motor or motive power machine is formed integrally with the pump itself. But a power pump receives motion only by trans- mission from an independent motor, which may also be giving out power for several other purposes. The simplest power pump, and the most quiet in working, is made by connecting the pump rod or rods with a crank shaft which is driven by a belt without the intervention of gear wheels. The working of a geared pump is always attended with noisy rumbling, and if the gear wheels have their teeth cast with them, and are of the type generally turned out from an ordinary foundry, there will also be intermittent knocking so disturbing as to make the pump altogether inadmissible for some services. With accurately cut gear teeth — ensuring effectual contact of the engaging teeth throughout their entire width, and thus permitting of the employment of a fine pitch — the noise is much lessened. The improvements effected in recent years in wheel cutting machines, and machine tools generally, have made it possibie for makers to employ wheels of considerable size, having teeth cut from the solid metal, without putting a prohibitive price on their pumps. The practical incompreasibility of water is exemplified in a most unpleasant manner in the working of a power pump fitted with wheels having teeth which indifferently gear with each other, and have appreciable "back lash." Fig. 61 is a sectional sketch diagram representing a geared power pump. On the out-stroke of the water piston A (or its movement 102 THE CONSTRUCTION AND WORKING OF PUMPS. in the direction indicated by the arrow 1) the water pressure will act upon the front end of the piston, and the connecting rod B will be in tension. As the connecting rod approaches and passes over the " dead centre " C the piston will be brought to rest, and its out-stroke thus completed. But as the connecting rod moves away from its dead centre the piston B, on commencing its return stroke, impinges upon the water at the back of it. The pressure is thus suddenly transferred from the front to the back of the piston, and the connecting rod is relieved from the tensile aud subjected to a compressive stress. There is no cushioning effect ; the piston is as suddenly obstructed as though it had impinged upon an armour plate. A similar water hammer action m///////M/y Pig. 61. being set up at the end of every stroke, or twice in each revolution, it will be readily understood that a violent knocking must be set up if the pump gear wheels have much " back lash " between the engaging teeth. For pumping against heavy pressures, and for dealing with large quantities of w r ater, the use of gearing in a power pump is generally unavoidable, but unless the setting up of a noise rivalling that of a steam hammer is of no moment, every care must be taken to ensure that the wheels shall gear in a very efficient manner. Power Enquired. The theoretical horse power required to raise a given quantity of water in a certain time, through a stated height, is simply the product of such quantity in pounds delivered POWER PUMPS. 1 per minute and the height in feet, divided by the number of foot-pound units representing 1 horse power, viz., 33,000. Thus the theoretical horse power required to raise 100 gallons (1,000 lb.) of water per minute through a height of 100ft, is— 1000 * 1QQ = 303 H.P. 33000 It should be remembered, in referring to the catalogues of pumping machinery by both British and American makers, in which tables are frequently given, that whereas a British imperial gallon has a capacity of 0'16 cubic feet, and contains 101b. of water, the United States gallon has a capacity of but '133 cubic foot, and contains only 8'331b. of water. Thus the theoretical power required to raise 100 United States gallons per minute through a height of 100 ft. will be but 2 '50, as against the 3 '03 horse power for 100 British gallons. But in providing for the working of a power pump, we must remember that the friction of the moving parts of the pump itself, of the gearing, and of the water through the pipes will absorb a considerable amount of power. In some cases the power so absorbed may equal the power required to raise the water — in other words, the mechanical efficiency of the pump (or the ratio between the actual work obtained from the pump and the amount of power applied to it) may be as low as 50 per cent. In calculating the theoretical power, it is, of course, the full height of lift that must be taken, or the height from the surface of water to be pumped to the highest point in the rising main. The height of the suction lift of the pump must not be deducted. Size of Belting. A power pump, as sent from the makers, may or may not be provided with a belt or driving pulley. When a pulley is provided the makers are usually careful to employ one of such a width of face as will receive a belt of ample strength to transmit the necessary power. Good leather belting will safely withstand a working stress of 70 lb. per inch width of 104 THE CONSTRUCTION AND WORKING OF PUMPS. single belt. The ratio between the tension on the tight side of a flat belt and the pull transmitted thereby to the rim of a pulley will depend on the length of the arc of contact between the belt and the pulleys around which it passes. The greater the ratio between the diameters of a pair of pulleys, and the nearer they are together, the less will be the arc of contact between the belt and the smaller pulley, which is the one that must be considered. With equal pulleys the arc of contact on each will be the semi-circum- ference, and the ratio between the tensiou on the tight side of belt and the pull transmitted to the pulley will then be 5:3, so that with 701b tension per inch width on the tight side of belt the pull transmitted to the pulley rim will be 70 x | = 421b. With double belting we may transmit a pull of just double the intensity permissible with a single belt, or 84 lb. at the pulley rim, as against 42 per inch width of single belt. The width of belting required can be readily calculated when we know the rim speed at which the driving pulley must be run and the rate at which the water is to be pumped. As an example, let us assume that we have a power pump with a 6.Hn. double-acting ram or water piston, and a stroke of 12 in., which is supplied by a maker for a delivery of 5,000 gallons per hour, against a total head of 240 ft., when the crank shaft is run at 35 revolutions per minute. If we know that the belt pulley is 30 in. diameter, and that there is a set of single purchase gearing (or a single reduction of gearing, as the Americans term it), having a ratio of, say, 5 : 1, we can at once calculate the rim speed of pulley or the speed of the belt as follows : Speed of belt = 35 x 5 x 2J x 3i or of pulley rim = 1375 ft. per minute. 3-1- represents the ratio between the circumference and the diameter of the pulley. Now, the amount of work required to raise the water is — 5000 x 10 x 240 = 12,000,000 foot-pounds per hour. POWER PUMPS. 105 Taking the efficiency of the pump to be two-third a, or 6 6 '6 6 per cent, then the actual expenditure of work per hour must be — 12000000 + 1200 o 0QQ0 = 18000000 foot-pounds. The speed of the belt ami of the pulley rim is, as we have seen, 1,375 ft. per minute, and therefore the pull required at rim of pulley will be — 1800000 = . ng lb 1375 x 60 Thus, iu this case, the width of single belting required is — 218 K . = 5 in. 42 Such a width will give ample strength ; if care is taken to see that the belt is run with its lower side as the tight or driving side, and there is a considerable horizontal distance between the pulleys, then, as the belt may be worked with but a moderate initial tension, and the arc of contact with equal pulleys will exceed the semi-circumference, a narrower belt may be employed. Types of Power Pumps. Fig. 62 represents a vertical type double-ram power pump, by Messrs. Frank Pearn and Co. Limited, of West Gorton, Manchester. The pump has two single-acting rams, con- nected to a crank shaft, which is driven by belting without the intervention of spur gearing. The makers recommend it for lifts up to 80 ft. vertical. Fig. 63 illustrates a vertical treble-barrel geared ram pump, by Messrs. Joseph Evans and Sons, of Wolverhampton, suitable for heads up to 300 ft. vertical. As will be seen, the pump is kept very compact by the use of short con- necting rods and crosshead guides for the three single-acting rams. Fig. 64 represents the horizontal form of the same type of pump, also by Messrs. Evans. It is without gear, and is 100 THE CONSTRUCTION AND WORKING OF PUMPS TYPES OF POWER PUMPS. 107 designed for either belt or wire-rope driving. Each of the three rams is provided with a crosshead working in slipper guides. Fig. 65 illustrates a three-throw horizontal ram or plunger pump, by Messrs. Hayward, Tyler, and Co., of Whitecross Street, London, E.C., having cast-iron crossheads and slipper Flo. 61. guides. The pump shown has three 15 in. plungers, with a stroke of 36 in., and is provided with two sets of gearing with sliding pinions, so that it may be driven at two speeds, for the delivery of 60,000 and 40,000 gallons per hour respectively. The belt driving pulley, 10 ft. in diameter, and weighing five tons, acts also as a flywheel. Air and vacuum vessels are attached to the delivery and suction 108 THE CONSTRUCTION AND WORKING OF PUMPS. mains respectively ; the vessels are of riveted steel plates, and are fitted with gauge or sight glasses. ' --iSB&t" Fig. 66 is an illustration of another treble-barrel or three- throw pump, by Messrs. Ha} T ward, Tyler, and Co., to raise 10,000 gallons per hour against 500 ft. head. The pump has slotted-steel cranks, cast-iron plungers 8 in. diameter, TYPES OK POWER PUMPS. 109 cast-iron glands bushed with gun-metal, and gun-metal neck bushes. The valves are of indiarubber, on gun-metal grids, with copper stalks and gun-metal guards. The air vessel is of riveted steel plate, and is fitted with gauge glass and pressure gauge. The gear wheels are of steel, with double-helical teeth, and drive the crank shaft at 40 revolu- 110 THE CONSTRUCTION AND WORKING OF PUMPS. tions per minute. The counter shaft, or first-motion shaft, has a Rodger's wrought-iron double-arm pulley. The main plummer blocks are tied to the barrels by bright rods. A treble-hydraulic pump, by Messrs. Hayward, Tyler, and Co., to work against a pressure of 1,2001b. per square inch, is illustrated at fig. 67. The three plungers are each 5-J-in. diameter by 8 in. stroke, and with a crank speed of 36 revolutions per minute deliver 70 gallons in the same time. Mitre pattern gun-metal valves are employed working on gun-metal seats. The crank shaft is of slotted steel, 6 in. diameter in the bearings. There are two machine-cut steel spur wheels and pinions, and the makers state that each pair has ample strength to transmit the whole of the required power. The width of the gear is 6 in. Spring relief valves are provided. Fig. 68 represents a triplex-horizontal heavy-pressure boiler-feed or mine pump, by the Worthington Pumping Engine Co., of 153, Queen Victoria Street, London, provided with relief valves. Fig. 69 is an illustration of a vertical triplex "stuff" pump by the same makers, especially built for use in paper TYPES OF POWER PUMPS. m 112 THE CONSTRUCTION AND WORKING OF PUMPS. and pulp mills. The makers state that the castings are all very heavy and well proportioned, that the crank shaft and connecting rods are of steel, the gears of hard-gear iron accurately cut, and the bearings of extra size and length, lined with best deoxidised babbitt. The connecting rods have adjustable boxes at both ends, whilst the crossheads have adjustable shoes, and move in cylindrical ways. ELECTRIC PUMPS. 113 CHAPTER XI. Electric: Pumps. Ordinary power pumps, such as described and illustrated in our last chapter, may be electrically driven by connection through belting or gearing with suitable motors. But the term "electric pump'' is properly applicable only to the combination of a pump and its motor upon the one base or framing, or with a motor employed for no other service, just as the term ''steam pump" is descriptive only of a pump combined with its own exclusive engine. Both direct or continuous current motors and alternating- current motors may be employed for electric pumps, but motors and electric fittings that give satisfaction on other services may be quite unfitted for the work of pumping water. And as regards the pump itself, it is of extreme importance to select a type that will give a steady propulsion of the water column. A pump having but one single-acting ram or plunger is most unsuitable for operation by an electric motor, owing to the very irregular distribution of the w-ork. A duplex-type pump having two double-acting plungers, ami a triplex-type pump, are well adapted for electric service. In some electric generating stations electrically-driven pumps are employed instead of steam pumps for feeding the boilers. It has been suggested that the primary reason for this practice is that it affords an opportunity of showing to visitors the application of electricity — the power on sale — to the pumping of water. An electric pump is not, however, so well adapted for boiler feeding as a steam pump, chiefly because the former has not that " flexibility of regulation " by virtue of which the latter can be readily set to keep that verv desirable " constant water level " in the boiler under varying rates of evaporation. It is sometimes urged that a saving of fuel is effected by the use of electrically-driven as against steam pumps. Such a claim cannot, however, be sustained when the comparison is made with high-class pumps. As an example of the results that can be obtained 8CP 114 THE CONSTRUCTION AND WORKING OF PUMPS. with well designed and constructed steam pumps, we may here mention that in a paper on marine engineering, read by Mr. James McKechnie, at the recent summer meeting of the Institution of Mechanical Engineers at Barrow- in-Furness, he gave results of tests which he had made on Weir direct-acting (or non-crank and flywheel) steam pumps, showing in one case a mechanical efficiency (or ratio between the work performed by the steam on the steam piston and the work given out by the water plunger or piston) of 94 per cent, and a steam consumption, in the case of a com- pound pump, of 31 lb. per indicated horse power per hour, with a mechanical efficiency of 92 J per cent. The water output of electrically-driven pumps is some- times regulated by means of resistance coils or rheostats, but the electrical energy not required for pumping is then simply wasted by dissipation. An American writer has well described this and another system in the following terms : " The only method of controlling the speed of direct-current motors known to the average steam engiueer, who as likely as not finds that in spite of his protests a new electric pump has been added to the plant of which he is in charge, is to pile extra resistance in the main circuit, aud it is not unusual to see the rheostat quite as large as the motor itself. While this may answer in a few instances, it will never be an acceptable solution of the variable speed motor problem, as the speed is cut down at the expense of the efficiency, the electrical energy is expended in heat overcoming the resistance in the many extra coils of wire, and it takes just as many amperes from the dynamo to run at 1 revolution per minute pumping 1 gallon, as to run at 1,000 revolutions per minute pumping 1,000 gallons. The function of a rheostat is for stopping and starting only ; that is all that should lie expected of it. "Another method, which is only a degree better than the ' resistance rheostat,' is to adopt some intricate system of interchangeable gearing or clutches between the pump and motor. Such schemes often work out very prettily on paper, but in practice they prove too complicated. They add to the first cost and bulk of the machine, and render it liable to get out of order at the critical moment." ELECTRIC PUMPS. 115 A system of controlling the speed of electric pumps — with direct-current motors — that has given satisfaction where a variation of about 25 per cent will meet require- ments, consists in the employment of motors with specially- wound field coils, so that the amount of current flowing through the field magnets can lie varied (by means of a small rheostat) for the purpose of varying the speed of the armature, and consequently of the pump output. Within the aforesaid limits of variation the amount of current used is in proportion, with such motors, to the quantity of water pumped. In another sj'stem advantage is taken of the fact that. " when two electrical uuits are run in series the voltage or potential is divided between them, and the speed cut down one-half." Thus by employing two motors of equal horse power they can either be run in multiple, when the full available voltage will act upon each, and the pumps worked at full capacity, or in series for the purpose of reducing the voltage and therefore the speed and the output of the motor and pumps by one-half. To arrange the motors for such service nothing is required beyond a few additional wires, so that by the mere opening and closing of a switch they can be run in series or multiple at will. But though for boiler feeding a steam pump is preferable to an electric, for the reason already given, and also because of the greater handiness of having a pump) adjacent to the boiler, depending for its working only on the steam there- from, there are other services for which electric pumps are eminently adapted. Thus, for what is known as house tank service and also for hydraulic elevator or lift service, small electrically-driven pumps miy be employed where a steam pump would be altogether inadmissible. It is true that quick-running elevators or lifts in large office blocks and hotels may be with greater advantage directly worked by electricity, by connecting the car-winding mechanism with a motor, yet such a system involves the use of a much more piowerful motor than is necessary to operate a small pump supplying either a gravity (or elevated) tank or a pressure tank. In the one case the motor must be capable of raising the full load at the required speed, whereas with a 11G THE CONSTRUCTION AND WORKING OF PUMPS. hydraulic elevator or lift supplied from a tank of sufficient capacity to contain enough water for several car trips, the pump motor has simply to supply sufficient power to make np the tank water level between and during the lift trips or journeys. This system has been termed the " hydro-electric system." The plant is perfectly automatic in action, for by means of a suitable snap switch the pump is started and stopped as required by the rise and the fall of the water in the tank. When motors especially wound to run at low- speeds are- employed, no gearing is necessary with these small electric pumps ; disturbing noise is thus effectually avoided. An electric triplex-ram or plunger-type pump, for heavier services, as made by the Worthington Pumping Engine Company, of 153, Queen Victoria Street, London, is illustrated at fig. 70. The three single-acting rams or plungers are arranged horizontally and driven, through a single reduction of spur gears, by ;i direct-current motor. The Worthington Company also construct electric fire pumps. Such pumps they provide with triplex differential rams or plungers for obtaining a very uniform delivery, and with exceptionally large valve areas and water passages to ensure the complete filling of the ram chambers when the machine is running at a high speed. These pumps can be arranged to deliver direct into fire pipe lines and sprinkler pipes, and the makers state that they can be relied upon for maintaining at all times a pressure on the entire system. The electrical device for starting the pump automatically is practically the same as that which the makers have used successfully on elevator service. They describe it as follows : "A regular rheostat is placed in the circuit, the arm of the rheostat being operated by a small hydraulic piston and a weight, instead of operating it by hand. The water pressure in the tire line, acting on the top of the piston, holds the weight up with the arm thrown back and the circuit broken. If a hydrant is open, or a sprinkler lets go, the water pressure falls, the piston is relieved of pressure by means of a regulator, and the suspended weight draws the arm slowly across the face of the rheostat, making the circuit and gradually cutting out the resistance. In this way the pump ELECTRIC PUMPS. 117 118 THE CONSTRUCTION AND WORKING OF PUMPS. is started automatically, the action on the motor being precisely similar to the operation of starting by hand. Any excess in the quantity of water pumped will again raise the pressure in the system and stop the pump. By merely laying a wire this same mechanism can be made to ring an electric gong placed anywhere in the factor} 1 , thus giving the alarm as soon as the first sprinkler opens." Electric mine pumps, owing to the facility with which the current can be conducted down the pit, are finding increasing favour for services in mines equipped with modern plant throughout. With electric pumps we have no steam pipes to provide, no condensation to guard against, and no exhaust steam to deal with. As the work on the pumps is constant, that "flexibility of regulation" to which we have referred is not necessary ; electric mine pumps will therefore compare the more favourably with pumps worked either by steam, or, as is sometimes the practice, by compressed air. Fig. 71 is an illustration of a vertical electrical sinking pump as constructed by Messrs. Hay ward, T}*ler and Co., of 90 and 92, Whitecross Street, London, for the Oerlikon Machine Co., of Zurich. The makers state that these pumps have differential plungers — lO.Vin. and 15in. diameter by ISin. stroke — driven by an enclosed crank receiving its motion through a double reduction train of double helical gearing from a motor placed at the top of the pump, as illustrated. The gearing and motor arc protected by a sheet-iron case, and the whole machine is suspended by a chain and eye bolts. There is a bye-pass valve for starting, and a primary valve lor the suction pipe. The pump illustrated was constructed to raise 12,800 gallons of water per hour against a head of 400 ft., the motor being 36 horse power of the Oerlikon type. A very large electrically-driven horizontal double-acting triplex pump has been installed b} 7 the Worthington Pumping Engine Co., at Austin, Texas, concerning which they supply the following particulars : " The situation at Austin, Texas, where this pump is installed, is in many respects peculiar. The city has practically an unlimited volume of water, with a fall of 60 ft, and can afford to waste any amount necessarj 7 to raise the needed supply to the highest point required, and CENTRIFUGAL PUMPS. 119 k L IQ KM 120 THE CONSTRUCTION AND WORKING OF PUMPS. is therefore completely independent of steam as a motive power. The water power thus secured operates a power station of about 3,000 horse power, which furnishes light and power for the entire city. Electricity generated at this station is transmitted to the pumping station, where a 300 kilowatt three-phase synchronous motor is used to drive the pumping engine. The motor armature is about 18 ft. in diameter, runs at 100 revolutions, the voltage being 2,200, and the number of cycles 72 ; it is coupled directly to the pump counter shaft which carries a pinion gearing with a spur wheel on the crank shaft. As the synchronous motor cannot be started up against a full load, a 72 in. friction clutch is provided on the counter shaft on the opposite side of the pinion from the motor. This is made possible by the use of a quill or hollow shaft, the brake shoes of the clutch being mounted on the counter shaft, whilst the friction wheel of the clutch and the pinion are keyed to the quill. "The pump proper is a horizontal triplex having three centrally packed double-acting plungers 18 in. in diameter by 24 in. stroke. It lias a daily capacity of 6,000,000 U.S. gallons, and is designed for a working pressure of 1301b. to the square inch. The spur wheel is carried on a solid forged shaft with U-shaped cranks. It is 146 4 in. pitch diameter, with east-it on body, and mortised teeth made of seasoned maple. The pinion is steel, 36 'G in. pitch diameter and 26 in. face. There is only one reduction of gears. This is made possible by the slow speed of the motor, and is a marked improvement on previous plants which have high speed motors, double, and even triple reduction of gears, with the consequent high periphery velocities, noise, and wear and tear." CENTRIFUGAL PTJJIPS, 121 CHAPTER XII. CeNIHIITGAL Pt'Ml'S. These well-known machines, with which water is raised by the centrifugal force set up by a revolving disc or fan, were first brought prominently before the notice of engineers and pump users generally at 'the Great Exhibition of 1851. A crude form of centrifugal pump was known as early as the middle of the 18th century. Rather more than half a century later, in the year ISIS, a centrifugal pump was constructed at Massachusetts, U.S.A., and became known as the Massachusetts pump. It resembled an ordinary fan blower, and comprised a horizontal shaft having four straight blades enclose'! within a cylindrical casing. But the pump had to be placed below the level of the water to be raised, for it is stated that "the vacuum power" was small. At the Great Exhibition of 1851 Appold introduced his pumps having fans or impellers with curved blades or vanes (in place of vanes of the radial type shown at lig. 72), and with other improvements which enabled him to show an efficiency three times greater than could be obtained with the old machines. Appold's improvements established the position of the centrifugal pump as a most suitable machine 122 THE CONSTRUCTION AND WORKING OF PUMPS. for raising large quantities of water against a low heail or pressure. The friotional loss in the working of a reciprocating pump is practically constant, and independent of the useful head or pressure against which the water has to be delivered. Take the case of a reciprocating pump working against a pressure of, say, 601b. per square inch or 139 ft. vertical head, and requiring a pressure of, say, 15 lb. per square inch to overcome the factional resistance. Out of the total energy supplied to the machine I = ths, or 20 per cent, will be absorbed in friction ; the remaining SO per cent represents the useful work done, or the mechanical efficiency of the machine. But if the pump is set to work against a head of "but 101b. per square inch, the frictional resistance will still require a pressure of 151b. to overcome it, and thus out of the total energy supplied only ~ "ths, or -10 per cent, will be accounted for in useful work done, the remaining 60 per cent being absorbed by friction. It will thus lie seen that "the efficiency of reciprocating pumps diminishes with the lift." With centrifugal pumps there is no such diminution ; indeed, it has been stated, though not perhaps with strict accuracy, that they work to best advantage on services where the lift in feet can be repre- sented by a unit figure. An increase iu the head against which the water has to be delivered by a centrifugal pump necessitates an increase in the speed of the revolving disc, fan, or impeller. The theoretical ratio between the head of water and the speed of the pump, when the revolving disc of the latter has arms or vanes which are radial at the periphery, is expressed by the formula — h = T g where h - head in feet (measured from the surface of the water to be raised); V = velocity of periphery of pump disc or fan in feet per second ; 1 1 = accelerating force of gravity, say 32 - 2. CENTRIFUGAL PUMPS. 123 As the height through which any moving body must fall freely to attain a given velocity is expressed by the well- known formula — h = 2L (of which we made use in an earlier article dealing with pipe areas), it might be erroneously concluded that the same formula would also apply here and that V represents also the velocity of the water. But on reflection it will be seen that the water in passing through the centrifugal pump receives energy which tends to propel it in two directions, viz.. in an outward direction along the radial arms, and also in a direc- tion tangential to such arms or blades of the fan, disc, or impeller. At the instant of reaching the periphery of the impeller the velocity of the water in each direction will equal the peripheral velocity, so that the water will be discharged from the periphery in a direction which is the resultant of the two directions aforesaid, and its velocity will also be a resultant of what we may term the two com- ponent velocities. Thus it is that 2.9 9 As an example let us suppose that the rim velocity of a pump disc with radial arms is .'56 ft. per second. The maxi- mum theoretical head against which the water can lie delivered with the pump running at the given speed will then Vie 36 ^36 = iQ ; J >2-2 But the actual head against which the pump can deliver water will be considerably less than 40 ft., depending upon the care taken in the design and construction of the pump to prevent sudden changes in the direction and velocity of the water. With the old style of radial arms, as shown at fig. 72, there is much loss through useless churning of the water. It is, of course, also of great importance that the bearings upon which the fan shaft rotates and the means 124 THE CONSTRUCTION AND WORKING OF PUMPS. employed for driving the fan or disc be mechanically efficient. To utilise the energy which might otherwise be spent in the formation of eddies in the discharge pipe of a centrifugal pump, Professor James Thompson suggested, subsequent to the introduction of the Appold improvements, the use of what is termed the " diffusor " or "whirlpool chamber." Such chamber surrounds the revolving disc, and the water delivered into it from the latter is allowed to continue its whirl or rotation for effecting a more gradual and efficient conversion of the kinetic energy into the pressure energy required to force the water up through the delivery pipe. But in order to get full benefit from a diffusor or whirl- pool chamber it would in most cases require to lie so large as to cause more inconvenience than would be compensated for by the practical advantage obtained. Moreover, as the vanes of the disc are in British practice curved buck, and not made of the radial form previously referred to, the velocity of the water on leaving the fan, and consequently its kinetic energy, is diminished ; a further reduction of the kiuetic energy by its conversion into pressure energy before the water leaves the disc, impeller, or fan. is also effected in some centrifugal pumps by increasing the area of the water space towards the periphery of the disc. The whirlpool chamber or diffusor may therefore be greatly reduced in dimensions, and in some cases entirely dispensed with, in the construction of the pump, without loss of efficiency in its working. From the whirlpool chamber, or directly from the periphery of the disc, the water passes into the volute or spiral chamber, having a section uniformly increasing as it approaches the discharge or delivery pipe to receive the increasing volume of water from the disc. Conical suction and discharge pipes are sometimes employed with advantage. Figs. 73 to 76 represent four types of discs or impellers, as adopted by different makers. Figs. 73, 74, and 75 show (in side elevaton) three curved or sloping vane types by three different English makers, whilst fig. 76 represents (in plan) the modified radial vanes of a horizontal type centrifugal pump by French makers. CENTRIFUGAL PUMPS. 125 Unless a centrifugal pump can be fixed below the surface of the water to be raised, it is necessary to charge the casing with water before starting. For this purpose a steam ejector can be employed to exhaust the air from the pump casing andjpipes. 126 THE CONSTRUCTION AND WORKING OF PUMTS. Fig. 77 is an illustration of a centrifugal pump, for belt driving, by Messrs. Drysdale and Co. , of Bon-Accord Works, Glasgow. The makers state that " while these pumps will meet the requirements of all users for ordinary low lifts, CENTRIFUGAL PUMPS, 127 they will be found specially advantageous for irrigation, drainage, and similar work. The impellers or discs are specially wide to permit of the passage of any solid matter likely to he allowed inside, and a cleaning door is provided to meet the ease of any special obstruction." hi their lists, published with the pump as illustrated, the makers give the speeds necessary for lifts of 10 ft. and 18 ft. respectively. Thus a small pump, to deliver from 60 to 80 gallons per minute, must be run at about 1,000 revolutions per minute when working against a 10 ft. head, and 1,350 revolutions for a head of 18 ft. A larger pump, to deliver from 2,200 to 2,700 gallons per minute, is run at 315 revolutions per minute when working against a head of 10 ft., and 490 revolutions when working against an 18 ft. head. Pumps designed for high lifts (from 25 ft. to 50 ft. or more) are provided with fans of larger diameter than the low-lift types, in order to obtain the required peripheral velocity of the impellers or discs without driving the same at such a high rate of rotation as to cause inconvenience. Fig. 78 is an illustration of a combined centrifugal pump and electric motor, also by Messrs. Drysdale and Co. ; whilst 128 THE CONSTRUCTION AND WORKING OF PUMPS. tig. 79 represents a combined pump and vertical steam engine by the same makers, as employed for the circulation Fio. 79. of surface condensing water in the mercantile marine and for other services. CENTRIFUGAL PUMPS. 129 Messrs. Gwynue and Company, of Brooke Street Works, Holborn, London, E.G., who have manufactured such machinery for half a century, give the following terse summary of some advantages possessed by a centrifugal pump) : — '■ It can be erected with ease and celerity. " It works with an easy rotary motion, without valves, eccentrics, or other contrivances which consume power in friction. "It is economical in use, simple in construction, and of very great durability. " It discharges a continuous and steady stream without air vessels. "It is little affected by sand, mud, grit, or other foreign matter in the water ; in the larger sizes it will admit the passage of solid bodies 6 in. diameter, and the smaller sizes iu proportion, without injury." As compared with the full theoretical efficiency of 100 per cent, Messrs. Gwynue give the average efficiency of their centrifugal pumps as 75 per cent, and claim that so far back as 1862 a centrifugal pump of their manufacture gave, at the International Exhibition of that year, an etticienc}' of 83 per cent. As an example of the very accurate balancing of their machines, Messrs. Gwynue instance the experimental running with an empty pump of one of their centrifugal pumping engines, or centrifugal pump coupled direct to a vertical steam engine, at 550 revolutions per minute, when not fastened down but merely resting on timbers. The makers state that no vibration was experienced during such test. For emptying graving docks, and for other services where enormous quantities of water have to be rapidly discharged against a low head, the centrifugal pump is unrivalled. Messrs. Gwyune construct centrifugal pumps for such services with discharge pipes or branches as large as five feet iu diameter, and which on official trial have delivered over •82,000 gallons or 366 tons of water pier minute. Fig. 80 represents one of Messrs. Gwynne and Company's centrifugal pumps coupled direct to one of their enclosed silent high speed engines. 9cp 130 THE CONSTRUCTION AND WORKING OF PUMPS. Messrs. Gwynne and Company give the following particulars respecting their combined centrifugal pumping engine, as employed with surface condensers and for similar services, consisting of a vertical engine of the ordinary or open type having its crank shaft directly coupled to the spindle of the pump which is mounted on the engine bed : — CENTRIFUGAL PUMPS. 131 "The pump disc is of gun-metal and the spindle of steel, coated with gun-metal. All the bearings are of manganese bronze ami have large wearing surfaces carefully adjusted. In many eases, especially for the Admiralty, the pump casing, the disc, and the spindle are all of gun-metal. The pump disc and spindle can be removed and replaced without disturbing any pipe joint." Fig. 81 represents a centrifugal pump plant for high lifts, 102 THE CONSTRUCTION AND WORKING 01' PUMPS. by the same makers. A pair of pumps arranged in series are driven direct by a double-cylinder steam engine. The delivery from the one pump flows to the suction inlet of the other pump, which imparts more energy to the water to enable it to overcome a greater delivery head. This method of imparting the required energy to the water by means of two or more moderately sized pumps, arranged in series and rotating at the same speed, rather than by a single pump very large in diameter and running at a high velocity, may be sometimes adopted with advantage. In general, however, a reciprocating type pump would be employed for lifts above the economical capacity of ordinary centrifugal pumps. Fig. 82 is a sketch diagram representing an arrangement, recorded by C'ossier's Magazine, in which four pumps are coupled by a French maker (whose name is not given) direct to an electric motor A, all being arranged on the one bed plate, as indicated. It is stated that the plant was employed to raise water through a height of about 157 ft. No state- ment is made as to the efficiency of the arrangement, but in view of the many necessary changes in the direction of flow of the water, in passing from the suction pipe of the first pump to the discharge pipe of the last pump of the series, no great efficiency could be anticipated. Fig. S3 is an illustration of a centrifugal pumping engine fur circulating purposes, having twin delivery branches. CENTRIFUGAL PUMPS, 133 W. H. Allen, Son, and Company, of Works, Bedford, supply the following The makers, Messrs Queen's Engineeerinj particulars : — "The twin circulating pumping engine, patented by us, is of novel design, and is used for the purpose of limiting the machinery in the engine room of a twin-screw vessel, where every corner of the room is already tilled up. The object is to have one circulating engine for two condensers, having a common suction pipe to the sea in the usual way, but a double-delivery one to each condenser. The pump is divided by a central diaphragm and the disc is made of a new form in order to take the water from both sides and discharge equally from each of two distinct pipes. These pumps accomplish this work in an admirable way, discharging from each delivery pipe a solid body of water into each condenser. 134 THE CONSTRUCTION AND WORKING OF PUMPS. Iii manycises, where duplicate engines cannot be got in, this will be found an advantageous method of applying circulating engines to twin screws." Fig. 84 is an illustration of a combined circulating and air pump, or pumping engine, also by Messrs. Allen, who describe it as follows : — CENTRIFUGAL PUMPS. 135 "The illustration shows our combined circulating and air pump, which is the form we recommend for medium si/.es when the condenser is already fixed. As will be seen, the air pump is worked from the engine crosshead by steel connecting rods working in guides. The arrangement is particularly suitable where space is limited.'' In connection with their belt-driven centrifugal pumps, Messrs. Allen give the following particulars concerning one of large dimensions, as made for the irrigation of a large ;otton plantation in Egypt : — '"The discharge pipe is 36 in. diameter, and the pump is capable of throwing 90 tons of water per minute. The engine for driving it is a 130 horse power, passed through a treble leather belt, 21 in. wide and | in. thick. The pump is made m two pieces, and every facility is provided for getting at the interior without difficulty. The pulley is made extra large, so that there may be no slip on the belt ; the shaft is supported by two bearings bolted on to a massive bed plate. To charge the pump, a patent ejector is fitted on the top i if casing, and the pump is also provided with a gauge idass to enable the position of the water to be ascertained when starting the pump." For marine salvage purposes Messrs. Allen construct centrifugal pumping engines having the whole of the working parts id solid manganese bronze forgings. The following description of such engines is from the pages of Engineer inq : — "In these pumping engines the parts usually made of steel — that is, the piston rod, connecting rod, crosshead, crank shaft, pump spindle, eccentric rod, eccentric strap, and valves, as well as the bolts and nuts, — are of manganese bronze. The engines have been designed to prevent the loss of time which frequently occurs in raising ships which are only partially submerged at low tide. In such cases the machinery has sometimes to remain under water for several days together, until advantage can be taken of a low tide to pump out the ship. With steel working parts, great difficulty arises from the journals of the shaft becoming oxidised to such an extent as to cause a quantity of minute particles of steel rust to remain in the bearings. 136 THE CONSTRUCTION AND WORKING OF PUMPS. Immediately the engines are started, seizing takes place, and then a complete overhaul has to be made, during which time the opportunity is slipping away, and when matters are put right the rise of the tide stops the work. Great difficulty was experienced in obtaining a suitable metal to form the bearings for forged bronze to work in, and many alloys were tried before one was found which fully answered the require- ments. The alloy now used is a hard mixture which runs at high speeds without heating, and wears in a short time to a smooth and glassy surface. The strength of the forged bronze is about that of mild steel (29 to 30 tons per square inch), so that nothing is lost by the adoption of the new metal." Concerning the method of charging centrifugal pumps by exhausting the air Messrs. Allen give the following descrip- tion : — "Where the pumping engine is placed above the water it is first necessary to charge it before working. For this purpose we employ a patent ejector, which will exhaust the air and draw the water up from a depth of 25 ft. The arrangement is very simple, and yet perfect, the ejector being the smallest and most convenient contrivance that can possibly be devised for this work. It is screwed into the highest part of the pump, and also connected by a separate steam pipe to the upper part of the steam stop valve on the engine or boiler. In a few minutes after turning on steam the pump will be charged, the engine remaining stationary meanwhile. To prevent the air returning through the discharge pipe a flap valve is fitted on to end of the delivery pipe. For marine engine purposes the ordinary Kingston valve answers the purpose. For charging the large pumps we strongly recommend this method of flap valve and ejector as in every way most convenient and suitable, being much less costly and more efficient than any other means. It does away with the necessity of a foot valve, and is a. much neater arrangement than an air pump or mechanical exhauster, as it is always ready, and cannot get out of order. There are a number of instances, however, where the foot valve is indispensable, and where it is as useful and conve- nient as the ejector." ROTARY PUMPS. 137 Some centrifugal pump makers insert in their published lists particulars as to the alleged horse power required to raise a given quantity of water per foot of height. It would be of very great advantage if the actual horse power neces- sary to drive the pump were stated, but if the figures simply represent work performed in raising the given weight of water through the height named, with no allowance what- ever for factional losses, they are worse than useless. A buyer who relied 11)1011 such figures in arranging for the power t0 in., and 10 in. One piston rod* to each cylinder, 3J in. diameter. .Stroke, 36 in. Revolutions per minute duiing trial, 34114. Piston speed, 'J17 '84 ft. per minute. Head on pumps, i!S6'9 ft. Mean ttearn pressure in boilers, 1381b. per square iueh. Mean steam pressure in valve chest, 1361b. per square inch. Mean absolute pressure in valve chest, 1501b. per square inch. Mean vacuum, -11 79 in. Results ok Trial. Water pumped per hour, slip neglected 18,540 cubic feet. "Water pumped m 12 hours ' 1,388,100 gallons. Pump horse power by pressure gauge 167'6. Consumption of steam per hour 2,1881b. Steam per pump horse power hour 13'051b. Indicated horse power 1 bo 70. Steam per I.H.I', hour 1T91 lb. Mechanical efficiency of engine 0'913. As will Vie seen, the steam consumption came out at much less than specified in contract. 144 THE CONSTKCCTION AND WOEKIXG OF PUMPS. Professor Unwin summarises as follows : — " In this country the duty is estimated as the effective work of the engine in foot-pounds per 112 lb. of coal. The effective work in the trial was 107-6 x 1,980,000 = 331,^50,000 foot-pounds per hour. The actual coal con- sumption was 296-5 Hi. per hour. Hence the actual duty was 125, .'550,000 foot-pounds per 1121b. of coal. This is a very good, but not exceptional duty." "In this trial the efficiency of the boiler was not good, and the duty which depends on the performance of the boiler and engine is not so good as it would have been if steam had been supplied by a more efficient boiler. With a good boiler, hand tired, with Welsh coal, the evaporation might very well have been 9'5 lb. per pound of coal. Then the coal consumption would have been 240'8 lb. per hour. In that case the duty would have been 154,350,000 foot- pounds per 1121b. of coal. Tins is an exceptionally high duty." "In America it is common to reckon the duty of a pumping engine as the foot-pounds of effective work per 1,000 lb. of steam supplied to the engine. Taking this measure, the duty of the engine is 151,070,000 foot-pounds. This is almost as high a. duty as has ever been recorded. It involves no assumption as to the performance of the boiler." KIEDLEK PUMPING ENGINES. 145 In the illustration, at fig. 87, the letters F.L. indicate the engine room floor level. Riedler Pumping Engines. In a former article, when discussing pump valves generally, we referred briefly to the Reidler mechanically- operated valves for the water end of a pump. Figs. S8 and 89 represent in plan and elevation respec- tively a Riedler pump in direct connection with an electric motor. The general arrangement of the operating mechanism for the water valves is clearly indicated in the figures. The illustrations are from the catalogue of Messrs. Fraser and Chalmers Limited, the sole manufacturers Loth in this '/;//////,'/>'/////. Flo. 89. country and in America of the Riedler pumps. Their English works are at Erith, Kent, and their London office at 43, Threadneedle Street. The particulars given here- under are from the makers " description and argument : ' concerning the Riedler system : — "The principal feature of the Reidler pump is its mechanically-operated valve. The valve and valve seat are circular in form, and made of high grade bronze. The IOcp 1-tG THE CONSTRUCTION AND WORKING- OF PUMPS. valve has a lift of from 1 in. to 2 in., and an area of such amount as to reduce the speed of the water flowing through same to but a few feet per second. At the beginning of the stroke the valve opens automatically, controlled, however, by a very simple and effective mechanical device. It remains open practically the entire stroke. When near the end it is positively closed at the proper moment by the controller. The valve opening being large, all throttling of the water through the valve passages is avoided. The mechanical controller, closing the valve at the proper moment, prevents slip, and allows the pump to be run at any desired piston speed." " In ordinary pumps, owing to the large number of small valves required to get the desired valve opening, and the fact that these valves are closed by a spring, in conjunction with the reversal of pressure, in case it is desired to run the engine at a high number of revolutions, the lift of the valves would necessarily have to be reduced, or otherwise an enormous loss due to slip would result. Reducing the lift of these small valves would necessitate the use of a greater number. This would result in making the pump end much larger. As it is at present, the pump ends on the ordinary pumps are often built with large flat surfaces, the form least able to withstand water pressure. Or if the circular form of pump body is used, it would mean making this of much greater diameter, so as to be able to place in same a large number of so-called valve cages. In either case the strength of the pump body is reduced unless a large addition is allowed to the thickness of the same. This results, of course, in the ordinary direct-acting and fly- wheel pumps running at a low piston speed, otherwise the loss due to throttling of the water through the numerous valve passages, already great, is made greater, and loss by slip largely increased." " In the Riedler system, however, because of the circular form of the valve, and the fact that all pressure parts are built cylindrical or spherical in form, it is simply necessary to slightly increase the diameter of the valve and its lift, thus greatly increasing the valve opening, and but slightly decreasing the strength of the pump body." RLKDLEU PUMPING ENGINES. 147 " It should be borne in mind that the difficulty of running pumping engines at high speed is due to two things, namely: the small valve area, necessitating the travel of water through it at a high velocity ; and high lift, for unless valve is closed mechanically a great loss by slip will result. These difficulties are entirely overcome by the construction of the Riedler valve and its mechanically- controlled operations." A record of a test made in the year 1895 on a pair of double-acting Riedler pumps arranged at the rear of, and driven directly by, a cross-compound condensing Corliss engine, gives a duty of 125,824,903 foot-pounds per 1,0001b. of dry steam. The high-pressure cylinder of engine is 22 in. and the low-pressure cylinder 36 in. diameter; the pump plungers are 15^ in. diameter, and the common stroke 42 in. Steam pressure, 1201b. by gauge. The capacity at 75 revolutions per minute is 15.000,000 gallons (U.S.) per 24 hours (representing a mean piston speed of 525 ft. per minute) against a pressure of C2 lb. per square inch. At a test made by Professor Edward F. Miller, of the Massachusetts Institution of Technolgy, in May, 1895, on a Keidler pumping engine at Chestnut Hill Pumping Station, Poston, U.S.A., the extremely low figure of 1 1 '22 lb. of steam per indicated horse power per hour was recorded. The mechanical efficiency is given at 89 '46 per cent, so that the steam consumption per actual or pump horse power comes out at ll!'541b. per hour, or a duty of 158,147,000 foot- pounds per 1,0001b. of steam supplied to the engine. The following description is given concerning the above pumping engine : — " The engine proper is a vertical inverted beam engine of the Leavitt type, having cylinders 13'7, 24'3, and 39 in. in diameter, and a stroke of 6 ft. Steam is admitted to the high-pressure cylinder at 1851b. pressure (200 1b. abso- lute), directly from a separator which forms the inlet side pipe. Pie-heaters are placed between the high-pressure and intermediate, and betweeen the intermediate and low- pressure cylinders, and are supplied with steam at boiler pressure. The high-pressure and intermediate cylinder and cylinder heads are steam jacketed with the steam at boiler 148 THE CONSTRUCTION AND WORKING OF POMPS. pressure, and the low-pressure cylinder and cylinder heads are steam jacketed with the steam at 100 lb. pressure. The drains from the high- pressure and intermediate jackets, and from the re-heaters, are led directly back to the boiler, while the drains from the low-pressure jackets discharge into the feed- water heater. From the low-pressure cylinder the exhaust passes through a surface condenser, which is served with water from the discharge of the main pumps." " The pump end is of the Riedler type, with mechanically- operated valves, and consists of three double-acting pilunger pumps, each with its two inlet valves and two discharge valves. At the side of each pump there is a wrist plate, through which the valves are controlled by power derived from the engine. B} T this mechanism the spring pressure is removed from the valves previous to their opening, and is re-applied toward the end of the plunger stroke in such a manner as to bring the valves easily to their seats at a rate in proportion to the diminishing flow, thus preventing a back flow and the forcible closing of the valves with ihe reversal of the action. Suitable provision is made for elasticity in the connection to allow for any obstruction to ihe closure of the valve. The action of the valves is thus rendered so easy that the pump runs smoothh T , and easily, at over 50 per cent above its rated capacity." The average steam pressure in boiler during trial is given at 175'TIU, and the speed of engine and pump 50'59 revolutions per minute, being a piston speed of GOT ft. per minute. The record of water pumped during 2i hours' trial is 21,010,000 U.S. gallons against 137 ft. head. Comparing this Riedler triple-expansion vertical pumping engine with the foregoing vertical triple-expansion pumping engine by Messrs. Bathorn, Dave)', and Co., it will be noted that, although the cylinder diameters closely correspond, the Riedler engine works with a higher steam pressure, and has double the length of stroke, and runs at a piston speed two and three-quarter times greater than that of the llatborn-Davey engine. The tests show a 4 per cent advantage in steam consumption in favour of the Riedler engine, but we have no figures before us regarding the respective first costs of the engines, and the expense of maintaining the same in effective condition. KIEDLEK PUMPING ENGINES. 149 Referring again to the tigs. 88 and 89, the pump there shown in direct connection with the motor is described as a " duplex differential " type. As will be seen, the two water cylinders are each divided, and an externally-packed ram is reciprocated between them, stuffing boxes being arranged on the adjacent ends of the divided parts. There is but one suction and one delivery valve for each complete pump cylinder, the said valves being arranged in the rear division. On the movement of the ram in the direction indicated by the arrow at fig. 89, the water drawn in through the suction valve A on the preceding out-stroke is displaced, and whilst one portion of it is forced direct into the rising main, another portion flows along the pipe B, and into the forward division of the cylinder, to fill the void space resulting from the difference in area between the outgoing portion of the ram and the incoming portion of the rod C. On the next out-stroke the suction water flows into the rear division of the cylinder, and a delivery is effected from the forward division into the rising main. Messrs. Fraser and Chalmers state : " The cost of a direct-connected electric motor of a stated power, by reason of its low speed, is greater than that of a motor of same power but of higher speed ; by direct connecting, however, all gearing, belting, or rope transmission, with attendant evils, are avoided : thus the greater convenience, durability, and economy of the direct-eonnect»d electric motor in a very short time more than save the difference in the first cost." They also give the following figures as to the actual losses in the electric transmission of power : — "10 per cent loss due to friction of steam engine. " 3 per cent loss between engine and generator, due to belting. This loss does not appear if direct connected. " 10 per cent loss in electric generator. " From 10 to 20 per cent loss in line depending upon voltage, length, size of conductors, kind of installa- tion, and care of installation. ''12 to 20 per cent loss in the motors, depending upon the type and the service they are to perform. 1T0 THE CONSTRUCTION AND WORKING OF PUMPS. " 5 to 10 per cent loss between the brake horse power of the motors and the machinery that is to be driven. " Loss in the machine itself." This leaves a total efficiency of about 50 per cent. The results as obtained above are practical working results, for which we are indebted to several of the large mining com- panies that are using electricity, and who also have other machinery built by ourselves. No account has been taken in the above of losses due to step-up, step-down, and rotary transformers. Where distances are short, and great care is taken in the installation, the actual working efficiencies for electricity may be increased to 60 per cent, or, in ease of carelessness in installation, ma} 7 be decreased below 40 per cent." Fig. 90 represents in outline one of four compound- condensing beam type rotative pumping engines, as con- structed by Messrs. Gimson and Company, of Vulcan Street, Leicester, for the sewage pumping station of that borough. The engines afford an excellent example of what may lie accomplished with a comparatively low T steam pressure (8011).) by careful design and sound construction. The particulars given hereunder are from a report presented by Mr. E. (!. Mawbe} 7 , the surveyor of Leicester, to his Town Council in the year 1891. " The sewage is delivered from the pumping station through two 33 in. rising mains fir a distance of about a mile and a half into the distribution tanks at the farm, to a net height of about 163'66ft. above the invert of the outfall sewer at the pump wells. There are four engines of the independent rotative comi-ound-condensing beam type. The diameter of the high-pressure cylinder is 30 in., with a stroke of 5 ft. '.)\ in., and that of the low-pressure cylinder 48 in., with a stroke of 8 ft. fi in. The cylinders are steam jacketed, that of the high-pressure cylinder being fed with steam at the boiler pressure of about 801b. to the square inch, and that of the low-pressure cylinder at the pressure at which it leaves the high-pressure cylinder. The steam cylinder slide valves are of the double-piston type, arranged in a cylindrical casing, cast separately from the cylinder, through which the admission and escaping steam for both high and low RIEDLER rUJIl'ING ENGINES. 15] pressure cylinders passes. The high-pressure steam cylinders are fitted with expansion piston valves, arranged to cut oil the steam at any point from §■ to -J of the stroke by means of hand gear, which can be worked whilst the engines are running, the working rate of the expansion being clearly indicated by automatic arrangements of pointers and scales. The low-pressure cylinders are also fitted with expansion piston valves, arranged to allow of the cut-oft being varied between \ and J, the working point being automatically indicated as in the case of high-pressure cylinders. 152 THE CONSTRUCTION AND WORKING OF TUMPS. "To each engine there are two main pumps for the sewage of the piston and plunger type, one at each side of the beam, having a stroke of oft. 9 Jin., the diameter of the piston being 27-]- in. The suction and delivery valves are flaps, faced with indiarubber, and the hinges bushed with gun metal. The two main suction pipes are 3 ft. in diameter, leading from the pump well and screen chamber to each pair of engines. A large steel air vessel 25 ft. 9 in. by 5 ft. diameter is fixed to each rising main. The air pumps and condensers are of the single-acting jet type, the interna- valves and fittings being of gun metal, with flat indiarubber discs. "The flywheels are of cast iron, 21ft. in diameter; they weigh about 21 tons each. The beams are formed of double steel flitches, 2 in. in thickness and G ft. in depth at the centre." As will be seen from the illustration, the pump rod for the pump on one side or end of the beam is formed by a continuation of the high-pressure piston rod. The specification called for an effective duty of not less than 100,000,000 ft. -lb. per 112 11.. of coal, with the engine running at a speed of 12 revolutions per minute, and a boiler pressure of b0 lb. per square inch. The record of the official tests gives an average duty (measured by the weight of water actually pumped) as 115,913,333 ft -lb. per 1121b. of coal (Nixon's Navigation). As the average evaporation in the boilers per pound of coal (from actual temperature of feed water and at actual steam pressure: was 10'031b., the duty per 1,000 lb. of steam works out as follows : — 115,913,333 x ^- = 103,181,493 ft. -lb. 112 x 10-03 The average indicated horse power during the trials was 1 99"63, and the average pump or actual horse power lTS'lT ; the mechanical efficiency was thus 89'-! 1 per cent. Measured in horse power terms, the average coal con- sumption was 1 '7 12 lb. per indicated and T915 lb. per actual or pump horse power per hour. The steam consumption was 17T71b. per indicated and 19'21b. per pump horse power per hour. MINE PUMPING ENGINE, SURFACE TYPE. 15: It is interesting to note that the "slip" through the valves and the pistons of the pumps was but T27 per cent with one pair of the engines, and OS7 per cent with the other pair. By a separate test, the coal required for the boiler feed pumps was found to be 2'38 per cent of the whole quantity used, or 0'05 lb. per actual or pump horse power. The- steam used for the feed pumps during the trial was taken from a separate boiler, supplied with coal apart from that used for the pumping engines. Mine Pumping Engine, Surface Type. Figs. 91 and 92 represent, in elevation and plan respectively, a differential surface mine pumping engine by Messrs. Hathorn, Davey, and Company, of Leeds. Such Fig. 92. engines, which may be either single-cylinder, compound, or triple expansion, are fixed on the surface, and their reciprocating motion is transmitted to the pumps (fixed in the shaft) by means of quadrants mounted on beams across the shaft mouth. The particular type illustrated is termed by the makers the " South Staffordshire mine drainage type," and the engine is arranged in this instance for working 154 THE CONSTRUCTION AND WORKING OF PUMPS, bucket pumps in pairs. For lifts up to 200 ft. an engine capable of raising 1,400 gallons of water per minute will occupy the following (approximate) space: A, 28ft, 6 in.; B, loft.; C, 3 ft. 9 in.; D, 16 ft.; E, 7 ft. 3 in.; F, lift. 3 in.; G, C ft. 3 in. The pump shown in the illustration is a compound with jet condenser, the cylinders and condensers being disposed in a tandem arrangement as illustrated. The advantages claimed by Messrs. Hathorn, Davey, and Company for surface as against underground pumping engines are; Economy in steam, and therefore in coal; in boilers, and in stokers' wages ; also greater safety in cases where the mine is liable to be flooded. Mine Pumping Engine, Underground Type. Fig. 93 illustrates, in elevation and plan, a differential underground mine pumping engine, by Messrs. Hathorn, Davey, and Company. The engine is compound and jet condensing ; the two steam cylinders, the condenser, and the pumps (which in this case are of the piston type) are disposed in a tandem arrangement, as illustrated. The makers express their experience regarding piston pumps as follows: "Pumps of this class are less suitable for permanent colliery work than ram pumps, as, unless the water is practically free from grit, the piston packing is liable to give trouble ; lint, on the other hand, they occupy a rather smaller space longitudinally than a ram pump, and are somewhat less in first cost." For heads up to 150 ft a DAYEY S DIFFERENTIAL VALVE GEAE. 155 pumping engine of this type capable of raising 1,300 gallons per minute will occupy the following (approximate) space : -A, 43 ft, 6 in.; B, 31 ft". 6 in.; C, 7 ft. 9 in.; D, 5 ft G in. The makers give as the advantages of underground pump- ing engines, as compared with the surface type, that their capital cost is much less, probably about one half the amount for the same horse power, and that space is not taken up in the shaft with spear rods and guides. They are, therefore, very largely adopted where coal is cheap and capital cost an important consideration. As regards the duty of the two types, Messrs. Hathorn, Davey, ami Co. make the following statement: "As an .approximate estimate, the duty in pounds of water raised 1 ft. high per cwt. of ordinary engine coal burnt may, for single or duplex steam pumps, lie taken as from 12 to 2"> millions according to the size of pump, steam pressure, and conditions of work ; and for a compound steam pump from .30 to 40 millions : while a surface engine will in ordinary work give a duty of from 50 to CO millions." Whilst such statements from eminent firms setting forth their experience of the figures obtained in the daily working of pumps are of great practical value, insistence must again be laid on the importance of having before us particulars as to the respective services and conditions of the rival types before arriving at any definite conclusion. Davey's Differential Valve Gear. The valve gear from which the Hathorn-Davey pumping engines, above referred to, obtain the name of "differential" is illustrated at fig. 94. The makers' description is as follows : — " Davey's differential gear consists essentially of a small subsidiary engine, the speed of which can be regulated by means of a cataract cylinder to any desired rate, and of a pair of links having no fixed anchorage, but attached at one end to a rocking shaft (or other convenient part) driven from and moving with the main engine, and at the other to the small subsidiary engine above referred to. It is evident that, supposing the subsidiary engine and the main engine 150 THE CONSTRUCTION AND WORKING OF PUMPS. to be moving in opposite directions, a point at the centre of the links will not be moved exactly in accordance with either of them, but will have a mean or differential motion between the two. It is from this central point that the valves receive their motion, and the arrangement is such that the valves are opened when the links are moved in the direction in which the main engine tends to move them. As before noted, the subsidiary engine is controlled by a cataract cylinder, and can therefore be set to move at a rate which will give the necessary valve opening when the main engine is working at any required speed ; but directly the speed is exceeded, either from increase of steam pressure or decrease of load, the main engine gains upon the subsidiary engine, the closing of the valves is accelerated, and steam either throttled or entirely cut off. The gear therefore forms a sensitive governor acting directly upon the steam valves. The illustration shows a subsidiary engine of the kind above- davey's differential valve geak. 157 referred to, together with a second small subsidiary engine also regulated by a cataract. This second small engine is ■used to reverse the steam valve of the differential gear engine, which therefore pauses, and with it the main engine also, until the secondary engine has made its stroke. The •cataract regulation enables this pause to be adjusted to a nicety, from a mere dwell at the end of each stroke to a pause of 10 to 15 or more seconds when for any reason it is desired to run the main engine dead slow." The Worthington High-dutt Pumping Engine. Fig. 95 is an illustration of one of four Worthington horizontal triple-expansion high-duty pumping engines in- stalled for the entire water supply at the Paris Exhibition of 1900. The following particulars are from the published records of the Worthington Pumping Engine Company : — " Each engine has — Two high-pressure steam cylinders, each 12 in. in dia. Two intermediate ,, „ ,, 20 in. ,, Two low-pressure „ ,, ,, 34 in. „ Two double-acting water plungers ,, 26 in. ,, Ami all have a uniform stroke of 24 in. Size : 12 and 20 and 31 by 26 by 2L" The engine is capable of delivering 6,600 imperial 7 3600000 In comparing figures relating to the performance of rams, it must be carefully remembered that the higher the ratio between the fall and the height of lift, the lower the efficiency. The figures published on a list of ordinary type rams by another maker, for a 10 ft. fall and a 100 ft. lift, gives an efficienc}^ of but 50 per cent, as against the above- named G7 per cent for the Decceur ram ; but if the same rani is employed for a 50 ft. lift with the same fall, the efficiency rises from 50 to 79 per cent "Windmill Pumps. The application of windmills for the purpose of raising water, so largely practised in America, is steadily, if slowly, extending in this country. The annular sail type is that most generally used. Fig. 105 represents such a mill, 10 ft. diameter and 20 ft. high, as made by Messrs. Robert Warner and Co., of 97, Queen Victoria Street, London, and Walton- on-Naze, Essex. It is further described as "direct-acting," for no gearing is interposed between the sail shaft and the pump. The mill is provided with an automatic regulating arrangement for opening and closing the sails to allow the wind to pass through the same, in case of sudden gusts, without doing any damage. It can be stopped and started at any time. With a 10 mile wind the mill, as illustrated, and of dimensions above referred to, will raise 120 gallons of water per hour 100 ft. high. A mill having a sail 20 ft. diameter will raise 960 gallons under the same conditions. Respecting wind power, Messrs. Warner give the following particulars : — "We would remark that the quantities of water given in the lists, that our mills will raise, are less than those given by some other firms, but special attention should be paid WINDMILL PUMPS. 173 to the fact that the quantities we give are raised by a 10 mile wind, viz., just a pleasant breeze. This velocity of wind can generally be relied upon for 8 hours out of 24, while higher velocities cannot. It is therefore highly im- portant, especially where the storage capacity is limited, that the mills should, if possible, work every day. With a 20 mile wind, viz., a brisk breeze, windmills are four times more powerful than with a 10 mile wind, and our mills with 174 THE CONSTRUCTION" AND WORKING OF PUMPS. about a 15 mile wind blowing through the entire 24 hours have often raised from four to five times the quantities we give for a wind blowing at the rate of 10 miles per hour, reckon ing upon the latter being available for 8 hours out of the 21 only. The large quantities, however, that can be raised in strong winds are, in the majority of cases, of little or no value, owing to insufficient storage capacity obtainable." A wind velocity of 10 miles per hour, or 14'67ft. per second, gives a pressure of nearly .V lb. per square foot; 15 miles per hour gives a pressure of rather more than 1 lb. per square foot. The ratio between the pressures may be taken as about 2:5. The list diameters of the sails of direct-acting windmills by Messrs. Warner and Co. range from 7 ft. to 20 ft. The geared windmills have sails ranging from 16 ft. to 40 ft. in diameter. With the largest size, 0,000 gallons of water per hour can be raised against 100 ft. head with a 10 mile wind. CHAPTEP XV. Manual and Animal Power Pumps. James Watt, for the purpose of comparing his engines with animal power, adopted a rate of work equal to 33,000 foot- pounds per minute as his standard measure of the capacity of a horse. Though this remains the recognised standard in this country fur the expression of mechanical work, it must not be forgotten that Watt wisely adopted a high value. Any animal worthy of the name of a horse should be capable on emergencies, and with the judicious application by the driver of the recognised persuasive and coercive methods, to perform work, for a very short time, much in excess of the engineers' standard. But only a most power- ful cart horse will be able to keep up such standard rate of doing work for a lengthened period, as maj T be necessary on pumping service. Similarly, though a strong man working at "high pres- sure" ma} 7 be able for a short time, and by a special effort, MANUAL AND ANIMAL POWER PUMPS. 175 to exert ith of a horse power, or to do mechanical work at the rate of 5,500 foot-pounds per minute, the standard "man power'' as adopted by leading makers of hand pumps, viz., T \rth H.P., or 2,750 foot-pounds per minute, is doubtless high enough for any continued effort. And great care must be taken not to assume too high a figure in considering the force or pressure exerted by a man on a pump handle. It is possible for him to impose the entire weight of his bod}- upon the handle, but the force or pressure exerted by an ordinary man on continuous pumping should not be estimated at more than 25 lb. If the leverage of the handle is insufficient to give the required increase of such pressure (of course at the expense of the stroke), then gearing must be provided between a hand wheel and the pump rod to still further increase the pres- sure applied to the bucket or plunger, with a corresponding reduction in speed. A hand wheel, or flywheel as it is sometimes termed, is generally considered more pleasant to operate than an ordinary pump handle, as the former, especially if provided with a heavy rim, serves as an equaliser of the energy applied thereto. The following figures are from the catalogue of Messrs. Joseph Evans and Sons, of Wolverhampton : — Capacity of a powerful horse = 33,000 ft. -lb. per min. ,, pony or mule = 16,500 ,, ,, „ an ox = 11,000 „ ,, ,, a man = 2,750 „ ,, Fig. 106 is a typical hand pump for general outdoor service. The water is not forced through piping or subjected to pressure by the upstroke of the bucket, but is simply lifted by such stroke up to the level of the spout through which it is discharged. Such a pump is therefore known as a "lift pump." The makers of the pump, as illustrated — Messrs. Joseph Evans and Sons, of Wolver- hampton — also describe it as a "yard pump." As an anti- freezing arrangement the makers place the working barrel, 3 ft. long, under the ground level, instead of making the hollow standard itself serve as the barrel, as in the figure. 17C THE CONSTRUCTION AND WORKING OF PUMPS. Fig. 106. Fig. 107 Fig. 108. MANUAL AND ANIMAL POWER PUMPS. 177 Fig. 107 represents Messrs. Evans' " flywheel lift pump with compensating lever," which the makers state "will be found to work much easier than the ordinary crank-motion pump." 12CP 178 THE CONSTRUCTION AND WORKING OF PUMPS. In the " lift and force pump," by Messrs Evans, illustrated at fig. 108, the pump rod passes out of the delivery chamber through a stuffing box, and the said chamber is so closed as to permit of the application of such force upon the water therein as to discharge it through the outlet branch under the required pressure. Fig. 109 is a sectional view of a pump of this type, with the delivery branch provided with a MANUAL AND ANIMAL TOWER PUMPS. 170 180 THE CONSTRUCTION AND WORKING OF PUMPS. Fio. 113. MANUAL AND ANIMAL POWER PUMPS. 181 screwed end for hose connection, and delivery pipe connection with attached air vessel and dip pipe. Fig. 110 illustrates a lift and force pump, by Messrs. Evans, mounted on a hard wood plank. This well-known type of hand pump can be very compactly and conveniently fixed against a wall. The lift pump illustrated at rig. Ill is by Messrs. Robert Warner and Co., of 97, Queen Victoria Street, London, and Walton-on-Naze, Essex. They term it their "Pillar- frame" type. Fig. 112 illustrates combined manual and animal power well-pumping machinery by the same makers. Either side can be put in or out of gear as required by means of lever-operated clutches. Fig. 113 illustrates a double-barrel deep-well pump by Messrs. Evans, with what is termed an engine frame, carrying 182 THE CONSTRUCTION AND WORKING OF PUMPS. the operating crank shaft provided with handles and flywheel. Another type of hand pump is shown at fig. 114. This is known as the "Manchester" double-acting hand pump, by Messrs. Frank Team and Co. Limited, of West Gorton, in that City. Fie. 115. Fig. 115 represents a modern type of one of the most ancient of water-raising appliances — the chain pump. The particular machine here shown is by Messrs. Robert Warner and Co. Having no valves or packing of any kind, these extremely simple machines are employed with MANUAL AND ANIMAL POWER PUMPS. 183 advantage for pumping liquid manure, gas tar, thick muddy water, and for many other services that would speedily clog Fig. 110. an ordinary reciprocating pump. Messrs. Warner also make chain pumps arranged for animal or for engine power driving. 184 THE CONSTRUCTION AND WORKING OF PUMPS. Fig. 116 is an illustration of treble-barrel deep-well pumps, with bullock or horse gear, by Messrs. Joseph Evans and Sons. A centrifugal pump arranged with horse gear, by Messrs. W. H. Allen, Son, and Co., of Bedford, is illustrated at fig. 117. The makers recommend it for supplying country houses with water, for filling cattle tanks, and for similar purposes. They state: "It is very easily fixed and soon set to work, it is not likely to get out of order, and any ordinary labourer can attend to it. The horse gear can be used for driving chaff-cutting or turnip-cutting machines, and other tools when not 'pumping." Semi-rotary J Pumps A very neat and compact type of double-acting hand-power pump is obtained by the employment of fixed and movable radial brackets or valve plates within a circular casing. The DIAPHKAGM PUMPS. 185 brackets fire each provided with a pair of valves, serving for the suction and delivery respectively. The movable bracket, which carries the suction valves, has a rocking motion imparted to it by means of a lever fitted on the pro- jecting end of the central spindle to which the bracket is secured. The said rocking motion gives the displacing or pomp action. The pump can be readily bolted to a wall or plank. Diaphragm Pumps. In these pumps, which are used for dealing with thick and muddy liquids — indeed, " with anything that will flow," as is sometimes stated — the displacing action is obtained by the reciprocation of the central portion of a circular or other shaped diaphragm. Such diaphragm consists of a flexible disc of leather, indiarubber, or other material, having its edges fixed to the pump body. The space beneath or on the one side of the diaphragm forms the suction chamber, whilst the opposite side serves as the delivery chamber. A valve and its seating are fitted to the central portion of the diaphragm, and also a bridle or bridge piece, to which the pump rod is attached. The reciproca- tion of the pump rod with the attached central portion of the diaphragm is effected by a pump handle or lever in the ordinary manner. INDEX. Accumulators, Steam, SO Admiralty Pattern Pumps, 52 Air in Pump Chamber, 7 ,, Pump, 134 ., Vessels, 14, 107 Allen's Pumps, 133, 1S4 Ancient Centrifugal Pumps, 121 ,, Mine Pumps, 59 Animal Power Pumps, 174 An ti- freezing Arrangement, 175 Appold's Pumps, 121 Aqua-thruster, 04 B Backlash in Pump Gear, 102 Bailey's Pump*, 35, 50, 163 Balkwil Valve, 55 Bank Pumping Engines, 73, 153 Beam Pumping Engines, 150 Bell-mouth for Suction Pipe, 20 Belting for Power Pumps, 103 Boiler Feed Pumps, 129 Brass Lining, 23 ,, Plungers, 22 Caliban Ram, 1( ? 6 Cameron Type Pumps, 32, 75 Centrifugal 1'umps, 121 Chain Pumps, 182 Charging Connections, 19 Circulating Pumps, 128 Clack Valves, 26 Crank Pumps, 39 Coal Consumption, (30, 144, 155 Compensating Cylinders, 161 Compound Pumps, 48, 62, 68, 147, 150 Condensers, 73 Corliss Typo Valves, 159 Cornish Type Pumps, 63, 73 D Davey's Valve Gear, 155 Deceeur'a Ram, 160 Definition of Pump, 1 Diaphragm Pumps, 185 Differential Ram, 77, 79, 149 ,, Valve Gear, 155 Diffusor in Centrifugal Pump, 124 Dip Pipes. 15 Double Way Valves, 25 Beat Valves, 27 Drum Pump, 13S Drysdalc's Pumps, 126 Duplex Pumps, 84, 40, 6<5 t 69, 15S Duty of Pumping Engines, 60, 140, 155 Efficiency of Pumps, 4S, 129, 137 152, 171 Electric Pumps, 113, 1£8 ,, Transmission Losses, 149 Energy of Suction Columns, 5 Erosive Action, 78 Evans' Pumps, 63, 76, 97, 106, 181 Fire Pumps, Electric, 116 Flap Valves, 19 Fluometer, 97 Flywheel Pumps, 39 Foot Valves, 19 Force Pump, 178 Friction in Pipes, 10 Gear for Power Pumps, 101 Gland Packing, 23, 55 Gimsou's Pumping Engine, 150 Green's Pumps, 55 Grell Cut-off-valve, 93 Gwynnes' Pumps, 129 187 H Hand Pumps, 174 Hatkorn Pavey Pumps, 14], 153 Hay ward Tyler Pumps, 107 Height of Suction Lift, 1, 5 Horse-Power, 175 Hot Water Pumping, 6 Hydraulic Motor Pumps, 67 ,, Pressure Pumps, 78, 110 ,, Bams, 163 Hydro-Electric Lift System, 116 i Irrigation Pump, 135 Leather Packing, 23 Lift Pump, 175 Limit of Suction Lift, M Ram Pumps, 17, 21, 53, 63, 77, 81, 117, 112 Rains, Hydraulic, 163 Rice and Co. 'a Pumps, 84 Reidler Pumps, 29, 145 Rotary Pumps, 137 Rubber Valves, 25 Salvage Pump, 135 Savery Pumping Engine, 59 Tvpe Puu.pt, SS Semi-Rotary Pumps, 1S4 Sewage Pump, 151 Short Stroking, 41 Sinking Pump*, 75, 118 Slip, 27, 30, 48, 153 Steam Accumulator, 86 Steam Consumption, 36, 48, 57, 114, 143, 117, 152, 161 Strainer, 19 Suction Chamber, 4, IS, 107 ,, Lift, 1, 5 Pipes, 10, 12, 16 Surface Pumping Engines, 73 Man Power, 175 Manual Pumps, 174 Massachusetts Pumps, 174 Mechanically Operated Valves, 29, 145 Mine Pumps, 50, 110, US, 153 Multiple Valves, 24 Murnford's Pumps, 31 Kewcomen Pumping Engine, 59 Nozzle for Delivery Pipe, 20 Packing, 21, 55 Peam's Pumps, 53, 63, 75, 81, 105, IS Pipes, 10, 12, 16 Piston or Plunger Speeds, 9, 146 Plungers, 21 Power Pumps, 101, 120 ,, of Man, 175 ,, of Animals, 175 Pressure Pumps, 78, 110 Pulsometers, SO Pulsometer Co.'s Pumps, 34, 48, 89 Tests, 38, 4S, 57, 100, 114, 143, 147, 152, 161 Triple Expansion Pumps, 70, 141, 147* 153, 157 Vacuum Chamber, 4, IS, 107 Valves, 24, 145 Velocity of Water, 10 Vertical Pumps, 32, 45, 49, 51, 53, 82, 106, 112, 142 w Warner's Pumps, 166, 172, 1S1 Watt's Pumping Engines, 60 Waterworks Pumping Engines, US, 140, 157 Weir's Pumps, 34, 44 Well Pumps, 74, 183 Whirlpool Chamber, 124 Windmill Pumps, 172 Work Done in Pumping, 2 Worthington Pumps, 34, 42, 53, 68, 111, 117, 15S John Heywood, Excelsior Printing and Bookbinding Works, Manchester. FRANK PEARN & CO. Ltd WEST GORTON, ■1 PUMPING MACHINERY FOR ALL PURPOSES. SURFACE AND JET CONDENSERS. AIR COMPRESSORS AND VACUUM PUMPS. Telegrams : "PUMPS, MANCHESTER." VERTICAL TREBLE RAM ELECTRIC PUMP. HORIZONTAL TREBLE RAM ELECTRIC PUMP. 2d. Weekly. 2d. Weekly. Published Simultaneously in London and Manchester every Friday. THE BEST WEEKLY JOURNAL MECHANICAL AND MOTIVE POWER ENGINEERING WRITTEN BY PRACTICAL ENGINEERS FOR PRACTICAL ENGINEERS. The Journal has a large staff of Contributors, of special experience in every branch of Engineering to which it is devoted, so that its readers- are kept fully informed with respect to the latest improvements and moat modern practice in Steam and Gas Engines, Hydraulic Engineering, Electrical Engineering, Boiler Making, Machine Tool Making, &c. To the TECHNICAL PUBLISHING CO. LTD., 31, Whitworth Street, Manchester, England. 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