By a power-driven pump is meant one actuated by Belt, Rope-transmission, Gear, Shafting, Electric-motor, Water-wheel, Friction, or by direct connection to a power shaft. It thus becomes very frequently a question which apparatus is most desirable. These are classified, thus— Where power can be had from a shaft in motion there is no pump so economical as the power or belt driven pump. This fact is shown by the rapid increase in the number of applications of this type of pump: the reduced cost of manufacture in making the teeth of the gear wheels, the use of automatic machinery, the production of interchangeable parts have tended to produce a high grade of machine at an attractive price. The energy expended in operating the power driven pump is obtained at the same economy as that required by the machinery in the mill or factory, and as a modern automatic cutoff engine will develop a horse power with considerable less steam than the direct acting steam pump the cost of the power required by the power driven pump is correspondingly less; it participates in the economy of the steam engine using from one and a half pounds of coal to five or six pounds per H. P. per hour. For this reason the power driven pump is oftentimes the more economical, and especially where shafting is adjacent to the location of the pump, or can be conveniently arranged by simply adding another length of shafting with the necessary pulleys, or even by cutting suitable openings through the walls for the belts. Single, duplex and triplex power pumps are described and illustrated upon the succeeding pages; power pumps are built with one, two, three, four or five cylinders and for either high or low pressure or general service, and their sizes, capacities, and the materials they handle are no more numerous than their combinations in erection. The portion of this work devoted to power pumps should be especially interesting and instructive to the attendants operating steam, compressed air and power driven pumps. Particular attention has been given to single-cylinder steam pumps because of the great variety of steam-actuated valves to be found in practice, each differing from the other in one or more essential features. It is due very largely to the numerous designs of steam valves, that difficulty has been encountered in managing single-cylinder pumps as successfully as those of the duplex type, the similarity of construction in the latter type, even in minor details, being much more marked. The successful operation of a pump depends to a great extent upon the intelligence displayed in its management, and an engineer can scarcely hope to obtain quiet and smooth running pumps and freedom from breakdowns and perplexing delays except by a thorough knowledge of the details of construction and operation. It must be remembered that power pumps are to be illustrated and explained in a class entirely excluding steam pumps; the latter are pumps in which the moving force is steam. Electric Pumps are properly power pumps in which the moving force is electricity which is conducted to the pumps by wires. PUMP PARTS.Fig. 181. Water Ends. There are properly speaking four kinds of water ends to steam and power pumps: 1, A solid plunger, with a stuffing box used for heavy pressings in hydraulic apparatus, or as shown in Fig. 182, for larger plungers. 2, A piston packed with fibrous material within the cylinder. See Fig. 181. The letter P in Fig. 182 and the following cuts indicates the plunger. 3, A plunger packed with a metal ring around the outside, as illustrated in Fig. 183. 4, Two plungers, Fig. 184, connected outside of the cylinder with a stuffing box in two cylinder heads, through which the plungers work. These are more fully explained and illustrated as they occur in many examples as they are referred to in the oncoming chapters of this work. The construction of the water ends of single cylinder and duplex pumps is practically the same; any slight differences which may be found are confined to minor details, which in no way affect the general design or operation of the pump. The steam or power ends of numerous and varied makes of pumps are also as shown in the following pages of this work; all pumps actuated by power—steam, electric, etc.—are possessed of these two distinguishing features—1, a steam or power end, and 2, the water end. Note.—This statement has exception in the cases of large pumping engines having a fly wheel or supplemental cylinders attached to an accumulator, in which case the steam is worked expansively. Fig. 182. Fig. 183. The steam end of the ordinary single steam pump, and also of the duplex pump, differs from the steam cylinder of the steam engine in that the former has four ports to each cylinder, i. e., two steam ports and two cushioning ports as shown hereafter in figures. Under the division of the work allotted to the “Steam Pump” will be found all necessary further notice of the steam ends of Pumps. Pump Valves. The valve apparatus is perhaps the most important part of any form of pump and its design has a material bearing upon its efficiency. Fig. 184. Fig. 185. The valves shown in Fig. 181 are carried by two plates or decks, the suction valves being attached to the lower plate and the delivery valves to the upper one. The upper deck, and sometimes both decks, are removable. The valves are secured to the plates by means of bolts or long machine screws, which, in turn, are screwed into the bridge across the board in the plate, as shown in Figs. 185 and 186 or capped as in Fig. 187. The valves in all pumps except the large sizes, which may properly be classed with pumping engines, are of the flat rubber disc type Certain improvements in pump-valves have been made which tend to increase the durability and to prevent the liability of sticking, which is not an uncommon occurrence after the valves have become badly worn. The improved forms of pump valves are shown in Figs. 186 and 187. Fig. 186. Fig. 187. When these valves leak through wear the disc may be reversed, using the upper side of the disc next to the valve seat. This can be done with ordinary valves also, provided the spring has not injured the upper surface of the disc. Valve seats are generally pressed into the plates, although instances may be found where they are screwed. When pressed in they may be withdrawn by substituting a bolt having longer screw threads than the regular bolt, and provided with a nut, as shown in Fig. 188. The bolt is slipped through a yoke and screwed into the bridge. By turning the nut the seat can generally be started without difficulty. Fig. 188. Fig. 189 represents the customary gland and stuffing-box in which the gland is adjusted by the nuts C and D upon two studs. After the adjustment has been properly made lock-nuts are tightened which leaves the gland free yet preserves the alignment. It has been proven by practice—after long and costly experiments—that a number of small valves instead of one large one are far the most durable; durability being the question. Corliss, Leavitt, Holly and other leading pump builders had occasion to find the truth of this statement early in their careers. The “slamming” of large valves under moderate speeds proved itself an almost insurmountable difficulty until the principle of keeping the valve area as low as possible within reasonable limits had been fully demonstrated. Fig. 189. To illustrate the advantage of having a number of comparatively small valves instead of one large one, suppose a pump to be fitted with four 31/2-inch delivery valves at each end, the valves covering ports 21/2 inches in diameter. The area of each port is 4·9 square inches. In order to provide an equal area between the valve and the seat the valve must rise a distance equal to one-fourth the diameter of the port. The combined area of the four ports is 19·6 square inches, which corresponds to the area of a circular opening 5 inches in diameter, one-fourth of which is 11/4 inches. It will be understood that the smaller valves can seat much more quickly and with less jar than the larger one, hence a larger number of small valves is not only better because of the great reduction in slippage, but they are also more economical, being subjected to less wear and tear. The lift of valves for moderate or low speed pumps is seen in Fig. 190 and those for higher speeds in Fig. 191. These engravings clearly show the relative position of the suction and discharge valves during the movements of the piston. Fig. 190. Fig. 191. Pump slip or slippage is a term used to denote the difference between the calculated and the actual discharge of a pump, and is generally expressed as a percentage of the calculated discharge. Thus, when the slippage is given as 15 per cent. it indicates that the loss due to slip amounts to 15 When pumps run very fast the piston speed is so high that the water cannot enter the pump fast enough to completely fill the cylinder and consequently a partial cylinder full of water is delivered at each stroke. High speeds also increase slippage, due to the seating of the valves. Fig. 191 represents a sectional view of the water end of a pump, showing the position of the valves during a quick reversal in the direction of the arrows, which illustrates the position of the valves corresponding to high speed. The valves in a pump, like almost every other detail in the operation of machinery, do not act instantaneously, but require time to reach the seats. When pumps run at high speed the piston will move a considerable distance, while the valves are descending to their seats, and water flows back into the pump cylinder until the valves are tightly closed. The valves will remain in the raised position shown in Fig. 191 until the piston stops at the end of the stroke, and under high speed the piston will reach the position on the return stroke indicated by the dotted line L by the time the valves are closed. The cylinder will be filled up to this point with water from the delivery chamber so that no vacuum can be formed until after the piston reaches this position. The volume of water that can be drawn into the cylinder must necessarily be represented by the cubic inches cf space, minus the quantity which flows back during the time the valves are closing. It will thus be seen that the actual volume of water discharged is considerably less than a cylinderful, and the difference, whatever it may prove to be, is called, and is due to slippage. Fig. 192. Fig. 190 represents the same pump running at a comparatively low speed. It will be noticed that the valves have not been raised as high as in Fig. 191, because a longer time being allowed for the discharge of the water, a smaller orifice is sufficient. It will be seen also that the piston, moving at a lower velocity, cannot travel as far in Fig. 190 before the valves In order to reduce the loss by slippage several valves are used instead of a single valve of equal area. A flat disc valve will rise a distance equal to one-fourth the diameter of the port or of the opening in the seat to discharge the same volume of water that can flow through the port in the same time. In practice the rise exceeds this proportion of one-fourth a trifle, owing to the friction of the water, and this is especially true at high speeds. Fig. 193. Reinforced pump valves. Where pure gum has been used for pump valves it has always proved too soft and when it has been compounded with other substances it has been found too hard to withstand the severe duty to which it is subjected as a material for pump valves. In the accompanying Fig. 192 is shown the Braden pump valve, which is made of composition of rubber having wire rings embedded in the center of the disc. The composition has been removed from a section to show these rings. A ferrule of Its wire coil frame work clothed with rubber maintains a due amount of stiffness, with a degree of flexibility which prevents its bulging into the holes in the seats, or sticking therein, and thus impairing the suction and discharge. Both sides, the upper as well as the lower, are made available for service. These qualities of stiffness and flexibility combined, permit this valve to adjust itself to form a water-tight seat. Figs. 194, 195, 198. Figs. 196, 197. Armored pump valves. As represented in Fig. 193 this is a valve made by stamping a metal disc out of steel which is then plated with copper to protect the surface and secure the adhesion of the rubber. Marginal notches are left on the inside and outside edges of the plate and rubber is moulded around these, and vulcanized to the required hardness; a brass or copper plate may be used instead of steel and the plates may be corrugated radially to increase their stiffness when the area of the valve is large. Experience proves that the water valve adopted together with its location, has a material bearing upon the efficiency Note.—The screwed seat is shown in Fig. 194, Stud Fig. 195, Metal Valve Fig. 196, Spring Fig. 197, and all put together in Fig. 198. Fig. 199. Valve seats, bolts and springs should be of the best composition or gun-metal; and valves of composition, or hard or soft rubber, to suit the duty such pump is required to perform. These valve seats are screwed into the valve plate, and valves may be changed from composition to rubber by merely removing bolt, and substituting one for the other without removing the seat. This is of great advantage where a pump is to be used for hot water after being used for cold water. Fig. 200. Fig. 201. Air chambers are placed upon the top of a pump, see Figs. 199 and 200, and contain air for the purpose of introducing an air cushion to counteract the solidity of the water, thus preventing shocks as the water flows through the valves; and also for the purpose of securing a steady discharge of water. The water being under pressure in the discharge chamber, compresses the air in the air chamber during each stroke of the water piston and, when the piston stops momentarily at the end of the stroke, the air expands to a certain extent and tends to produce a gradual stopping of the flow of water, thus permitting the valves to seat easily and without shock or jar. The capacity of the air chamber varies in different makes of pumps from 2 to 31/2 times the volume of the water cylinder in single cylinder pumps, and from 1 to 21/2 times the volume of the water cylinder in the duplex type. The volume of the water cylinder is represented by the area of the water piston multiplied by the length of stroke. For single-cylinder, boiler-feed pumps and those employed for elevator and similar service the volume of the air chamber should be 3 times the volume of the water cylinder, and for duplex pumps, not less than twice the volume of the water cylinder. High speed pumps, such as fire pumps, should be provided with air chambers containing from 5 to 6 times the volume of the water cylinder. The diameter of the neck should not exceed one-third the diameter of the chamber. When the pumps work under pressure exceeding 85 or 90 pounds per square inch, it is frequently found that the air gradually disappears from the air chamber, the air passing off with the water by absorption. In this case air should be supplied to the air chamber unless the pump runs at very low speeds, say, from 10 to 20 strokes for the smaller sizes and from 3 to 5 strokes per minute for pumping engines. At higher speed and with no air in the air chamber the valves Note.—In large pumping plants small air pumps are employed for keeping the air chambers properly charged. In smaller plants an ordinary bicycle pump and a piece of rubber tubing are used to good advantage. Vacuum chambers are shown in Figs. 199, 200 and 201. These devices are attached to the suction pipe. When the column of water in the suction pipe of a pump is once set in motion, it is quite important, especially under high speeds, to keep the water in full motion, and when it is stopped, to stop it gradually and easily. This is accomplished by placing a vacuum chamber on the suction pipe, as shown in the figures. The location of the vacuum chamber may be varied to suit the convenience of the engine room arrangements. Fig. 199 represents the vacuum chamber at the side of the pump, Fig. 200 shows it opposite the suction and Fig. 201 represents its position at the end of the pump. Fig. 202. Fig. 203. Vacuum chambers are practically of two designs, as shown in Figs. 202 and 203. The one shown in Fig. 203 should be placed in such position as to receive the impact of the column of water in the suction pipe. In order to do this effectively it should be placed in the position shown in Figs. 199, 200 or 201. The chamber illustrated in Fig. 202 is placed in the suction pipe below, but close to the pump. The action of the vacuum chamber is practically the reverse of that of the air chamber. The object of the vacuum chamber is to facilitate changing continuous into intermittent motion. The moving column of water compresses the air in the vacuum chamber at the ends of the stroke of the piston, and when the piston starts the air expands (thus creating a partial vacuum Thus the flow of water into the suction chamber of the pump is much more uniform during each stroke of the piston than without the vacuum chamber, and consequently the pump can be run at higher speeds without increasing the loss due to slippage and without “slamming” of the valves. Vacuum chambers should be slightly larger than the suction pipe and of considerable length rather than of large diameter and short. The size of the neck is substantially the same as in the air chamber. Fig. 204. PIPING A PUMP.Fig. 204 on the opposite page represents the pipe connections, etc., of a pump with the delivery opening on the opposite side. D represents the foot valve and strainer placed on the lower end of the suction, which should be not less than a foot from the bottom of the well; the distance named provides for the gradual filling of the well. C is the suction pipe proper, screwed into the elbow, E, which changes its direction into the suction chamber, which contains the strainer, A. This strainer can be removed for cleaning by lifting the bonnet secured by stud bolts on top. In connecting large pumps it is customary to attach a vacuum chamber, F, which in the absence of any regular pattern, may be made of a piece of pipe of the same diameter as the suction and screwed into a T, instead of the elbow, E, with a regulation screwed cap on top as shown in the dotted lines. A priming pipe is shown by the letter J, often used to fill the pump on starting. The discharge pipe connection is shown at G with the air chamber attached. This figure is introduced for the purpose of showing an approved method of piping a pump. It may be observed that the flange joints in this design are so arranged that they may be disconnected without unscrewing any part of the suction pipe; this feature is almost essential in view of needed repairs. The foregoing description of the parts of a pump relate to the water end solely; there remain the more complex and widely differing parts of the steam-end which constitute the distinguishing characteristics of the pumps built by the different makers. There remain also the particular parts belonging to the large pumping engines, air-pumps, etc. These will be described under their respective chapters with much added and essential matter. Particular details as to the conditions of service under which it is proposed to operate pumps are to be found on the next page. CONDITIONS OF SERVICE REQUIRED OF A PUMP.It is especially important that the makers and also the sellers of pumps and pumping machinery should be informed regarding the proper type, size, pattern and proportion of parts for any peculiar service, as well as to the plan of their connections and the kind of material to be used in their construction. This information regarding the conditions of the service under which the pump is to be worked is quite pertinent to the foregoing pages regarding the parts of pumps. The following questions are extracted from the catalogue of an extensive manufacturer. First—To what service is it to be applied? Second—The quality of the liquid to be pumped, whether salt, fresh, acid, clear or gritty, and whether cold or hot? Third—To what height is the water to be lifted by suction, and what are the length and diameter of the suction and discharge pipes? Fourth—Of what material is the suction pipe, and what is its general arrangement as regards other pipes leading into it, etc.? Fifth—Will the supply be taken from a driven well? If not, from what source? Sixth—To what height, or against what pressure, is the water to be pumped? Seventh—What is the greatest quantity of water to be delivered per hour? Eighth—What boiler pressure of steam is carried? Ninth—Will the pump exhaust into the atmosphere, into a condenser, or against a back pressure? If the latter, how much? BELTED PUMPS.Fig. 205. Fig. 205 represents an approved form of steam boiler feed pump, single acting. It has a crank shaft and a tight and loose pulley. It may be driven direct from any line shaft, a countershaft being unnecessary. This is a compact form of a boiler feed pump; formerly the pump crank shaft was attached to floor beams or timbers above and connected by a long pitman to the pump which stood upon the floor; the objections to the older system of apparatus were found to be the vibration of the long pitman and the springing of the floors. To obviate these two difficulties the pump and countershaft were attached to a post bringing them nearer together but finally resulting in the design of pump here shown. The broad base insures great stability in the operation of the pump especially when fixed to a rigid floor or timber foundation. In the Table below are given some details furnished by the makers relating to six sizes of this style of pump, to which may be added that the speed ordinarily used varies from 100 revolutions per minute for the small sizes, to 20 revolutions for the larger sizes. Table.
Fig. 206. Fig. 206 exhibits two independent pumps. The description of the pump shown in Fig. 205 will apply to the left-hand pump which is a boiler feed pump. The improvement consists in the addition of another pump at the right-hand side; this is a suction force pump with an air chamber and is used to draw water from a well and discharge it into a tank from which it is taken by the other pump and forced into the boiler, as occasion requires. These two pumps work simultaneously, being driven from the same shaft with cranks set opposite each other. Like the pump previously described this has a tight and loose pulley. The larger sizes are geared, having a pinion on the pulley shaft and a spur wheel on the crank shaft. These two pumps represent a high service and a low service, the left-hand pump working under high pressure, against that in the boiler and the right one against the head of water in the tank. Each pump has its own separate connections—one or more—to suit the required conditions. The right-hand pump is double acting; the plunger-rod is guided by a steadiment which holds it in line and preserves this alignment and the power is transmitted through a forked connecting rod. The Table below refers to both these pumps. Table.
In Fig. 207 is shown a double acting power pump used principally for feeding boilers but may be employed for any purpose in forcing water or other liquids against pressure. This pump is double acting, is made with four check valves, as shown in engraving, and will draw water through 25 feet of suction pipe. On a high lift like the foregoing a foot valve (as shown at D in Fig. 204) should be used. Straight Wings. Spiral Wings. Fig. 207. The form of valves used in this type of pump are the regular commercial check valves, made of steam-metal, extra heavy; the valve proper is of the wing pattern as shown in the small cuts. There are four of these wings on each valve, at right angles to one another forming a cross with arms of equal lengths. The seat of the valve has an angle of 45° to which the valve is adjusted. A part of this valve projects above the top and has a slot, shown by the dotted line in it to receive the edge of a screw-driver, held in a bit stock to grind the valve seat in refitting. The lift of the valve is regulated by the distance between the top of the stem and the bottom of the covering nut or cap. In hydraulic pumps it is found to be good practice to give the wings of these valves a twist, or pitch, so that the water in passing through will cause the valve to rotate and fall in a new position every time it comes in contact with the seat. Fig. 208 represents a very compact design of double acting low service belt driven pump. The water cylinder is bored and has a piston fitted to it; both ends of this cylinder are covered with “heads,” one of which has a stuffing box through which the piston operates; the outer end of this piston rod is fitted to a slotted yoke which slides upon a guide at the bottom. This mechanism, just described, takes the place of a pitman connection and occupies very much less space. The crank shaft is supported at each end in pillow blocks and is driven by a belt having a tight and loose pulley; larger sizes are geared. Access to the two sets of valves can be had by slacking up four nuts upon the long belts, two of which are shown in the engraving. The broad base secures great stability for this size pump. Fig. 208. Fig. 209. Fig. 210. Fig. 209 exhibits two single acting plunger pumps actuated by one shaft having a crank upon each end with crank pins opposite to one another. This shaft is supported on the top of two pillars which form a part of the solid cast iron frame. The boxes are babbited. The crank shaft has a cast iron spur gear keyed to it and meshes into a pinion upon the pulley shaft. The teeth are cut to insure smooth and quiet running. The power is transmitted through a belt upon a tight and loose pulley. Each pump is secured to the frame by four bolts. The lower end of the pitman has an arrangement to take up the wear by means of two set screws with lock-nuts as shown in the figure Duplex Power Pump. This engraving, Fig. 210, shows a special boiler feed pump having ball valves, as shown in section, and which is also intended for use in pulp mills and in other places where it is necessary to pump sandy or muddy water, or chemicals, soap and other heavy bodied liquids. These pumps have composition ball valves, composition plungers and composition lined cylinders and glands. The two barrels or cylinders of this pump are brought together so as to occupy as little space as possible. Instead of cranks eccentrics are used having very large wearing surfaces. Each pitman has a ball at its lower extremity forming a “ball and socket” joint, which is adjustable to compensate for wear. All the bearings are Babbitted and like the last pump described the gears have cut teeth. It is belt driven. If there are two cranks as in the duplex power pump they are placed opposite to one another or 180° apart, the circle described by the crank-pin containing 360 degrees. In the triplex pump this circle is divided into three equal parts of 120° each which is represented by the position of the cranks; a quadruplex or two duplex pumps attached to the same shaft the cranks will be 90° apart. This arrangement effects a uniform distribution of load on the crank shaft and one of the pumps is continuously discharging at its maximum capacity. This duplex power pump should not be confounded with the “Duplex Pump” so called. The latter has two steam cylinders and two water cylinders and is double acting while the former is single acting. The successful operation and durability of these, as of all power pumps, depends largely upon the judicious selection and application of a proper packing to the stuffing boxes. As for example, plaited flax dipped in a mixture of warm graphite and tallow, braided rawhide, Selden’s packing, etc., have proved by long service to have a low co-efficient of friction and are not liable to cut the plungers. The triplex power gang pump is shown in Fig. 211. The engraving represents two triplex pumps bolted to one bed, and having an extended pulley shaft with pinions near each end to drive all of the pumps. Fig. 211. Table.
* Teeth in Pinion.# Teeth in Spur Gear. The description of the duplex power pump just given, applies to this type also. The exception is that the triplex has three plungers and barrels instead of two. There are two spur wheels and two pinions on each pump to equalize the power to better advantage, as by this arrangement one eccentric is placed between each pair of spur wheels and two eccentrics outside. The pinion shaft is in one piece having tight and loose pulleys. Fig. 212. The eccentrics—six in number—are set at 60°, and an even strain on the belt at all points of the stroke is thus obtained, and connecting both discharges together insures a steady flow without shock. Where light duty only is required, these pumps are made without gears to run with the belt over pulleys. Fig. 212 represents a single acting triplex plunger pump actuated by a belt over a tight and loose pulley. The principal characteristic of this pump is the long connecting rods. These have at their upper ends regular connecting rod straps with brasses fitted to them and adjusted by wedges and set screws. At the plunger or lower ends of these rods bronze bushings and steel pins are used. These pumps are largely employed for pumping semi-liquids such as tar, soap, mud, tan-liquor, oils, chemicals, sewage, etc. The teeth of the pinion and the meshing part of the two gears are protected by a shield to prevent clothing being caught or parts of the body from being injured. For these various materials different valves are necessary to be used each suited to the substance to be elevated or conveyed. The removal of one cover, in this pump, exposes all the discharge valves and a plate uncovers each of the three groups of suction valves, as shown. The suction pipe may be attached at either end of the suction chamber while the discharge pipe may be connected with one or both ends of the discharge chamber. The pump here represented has barrels 8-inch in diameter by 10-inch stroke. The air chamber is very large in proportion to the pump. Table.
The Deane single acting triplex power pump is shown in Fig. 213. Pumps of this type are used for general service in places where a large quantity of water is to be obtained in a short time and delivered under high pressure; they are adapted for tank service, water works, boiler feed, etc. Fig. 213. The pillar, or column design of frame is employed in this pump which secures great strength with the least weight of material, and at the same time is accessible for adjustment or repairs. The bearings for both the steel shafts are unusually long, which reduces the pressure per square inch below the factor of The connecting rods have solid ends with adjustable boxes, with adjustment by means of wedge and screws. The brasses are lined with a special anti-friction metal bored to exact size. The crossheads are of the box design with adjustable shoes having large wearing surfaces in bored guides. These guides are secured to the frame by studs and nuts. The plungers are outside packed, the cylinders are submerged, thus keeping the pump primed at all times. The plungers are bolted to the crossheads and are readily removed when necessary. The cylinders are single acting and are cast separate from the base and other parts of the machine, so that repairs can be made at small cost, and, furthermore, should it be desirable to use the pump for moving liquids which would be injurious to cast iron, cylinders of other metals are substituted. The water chest is cast separate from the cylinders and is provided with large handholes, affording easy access to the interior and to the valves for inspection and cleaning. The handholes are located so that one valve may be removed independent of the others. Improved grease cups are placed on all the bearings. This pump is very popular with the users of power driven pumps and is generally selected for high pressures and for hot or gritty water. Its simplicity of design and construction, together with the convenient arrangement of working parts, renders it desirable in isolated places where little attention is given to any kind of pumps. Fig. 214. Fig. 214 represents the Gould triplex single acting power pump and is one of many designs of this class of power pumps. The frame consists of two standards, which contain the two end cylinders, and the seats to which the outside crosshead guides are bolted. These are held together by two castings, one containing the center crosshead guide, and the other The gear wheels are machine cut, the pinion and the adjacent teeth of the large gear are covered by suitable guards. The crossheads are provided with adjustable shoes or gibs, which work in bored guides. The connecting rods are fitted with straps and bronze boxes, which are adjustable for wear by means of wedge and set screws, the wristpin brasses being of the marine type. The cylinders are provided with bronze liners, which are readily removable when necessary for repairs, the plungers being ground to size, present a smooth polished surface to resist the wear. The valve boxes are separate castings, and each contains a set of suction and discharge valves. These valves are rubber discs, held firmly against the bronze seats by cylindrically wound springs. All of these pumps are furnished with air chambers, and vacuum chambers are provided when the nature of the service demands it. All valves and other working parts of the pump are accessible for inspection, cleaning and repairs, all internal parts being arranged within easy reach through the large handholes. The pumps here shown are intended for moderately light pressures as for example not to exceed 150 lbs. per square inch, but they are also made in heavier proportions for very high pressures (5,000 lbs. to 15,000 lbs.) such as is necessary to operate hydraulic presses, draw benches for brass and copper tubing and that class of work. A very simple automatic regulator and by-pass connection (shown in the chapter on accessories) can be attached to these pumps in situations where a constant pressure is to be maintained and allow the pump to run continuously at its maximum speed. This regulator is adjusted to open the by-pass valve whenever the pressure in the compression tank or pipe system exceeds the limit pressure, and so fills the office of a safety valve by allowing the surplus water to return to the tank. The Riedler belt driven pump is shown in Fig. 215. The principal feature of this pump is its valve; there is but one valve for the suction and one for the discharge, which greatly simplifies the pump end. When working against high pressures, the ordinary rubber or leather faced valves are oftentimes pounded to pieces, but in this pump, on account of the mechanical control, the valves work well under all pressures. Fig. 215. This valve and valve seat are circular in form, and made of bronze, as shown in Fig. 216. The valve has a lift of from 1 to 2 inches, and an area sufficiently large to reduce the velocity of the water flowing through it to 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, and it remains open practically during the entire stroke. When near the end, it is positively closed at the proper moment by the controller. This valve, see Fig. 216, may be briefly described as follows. The seat, A, is turned to slip into its place in the pump and is made tight by a round rubber hydraulic packing, B, in a groove near the bottom. A spindle or stud, C, in the center of this seat supports and guides the valve, D, which is made tight by a leather seal, E. The rubber collar or buffer spring holds the valve above its seat, and this valve unlike ordinary pump valves, always remains open except when pressure is brought to bear to close it. The valve bonnet, G, also forms the bearing for the valve stem with fork, which spans the spindle, C, at one end and having the valve lever and pin, H, for operating at the other end. The valve stem is made tight by a stuffing-box and gland as shown. The operation of this valve is substantially as follows. Fig. 216. At the beginning of the suction stroke the valve is opened by the rubber spring, F, the pressure upon the collar being relieved by lifting of the valve fork arms through motion of the eccentric. It will be observed from an inspection of Fig. 215 that both the suction valve and the discharge valve are controlled by an eccentric—rock arm—and valve levers similar to the motion of Corliss valves. As the plunger nears the end of its stroke and before it starts on the return stroke, the valve fork closes the valve, and thus prevents slip and avoids pounding, so common in pumps having valves that close by their own weight. In case of any obstruction between the valve and its seat the rubber buffer spring will be compressed thus preventing all injury to mechanism. The lost work expended in closing the valves is hardly worth any consideration as it is practically the friction only of the eccentric and the members of the valve gearing, the bearings of which are all small. The motion for these valve gears is usually taken from an eccentric on the main shaft. The standard speed of the Riedler pumps is about 150 revolutions per minute. Smaller pumps run even faster than this. It may be desired to connect a pump directly to a high speed electric motor or water wheel already installed. To meet these conditions, a special design known as the Riedler Express pump, is built. The chief feature of this pump, is its suction valve. This valve is concentric with, and outside of the plunger, and lifts in the opposite direction to that of the plunger when on its suction stroke. At the end of the suction stroke, the plunger presses the valve to its seat, thus making it certain that the valve is seated when the plunger starts on its delivery stroke, allowing practically no slip. A high air suction chamber containing a column of water is placed immediately before the suction valve, so it is certain that the pump will fill as the plunger moves. Ordinarily the pump would not completely fill, owing to the high speed of the plunger. These pumps are also built with steam cylinders both of the plain slide valve and Corliss designs. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
