N. Hawkins

Fig. 467.

Fig. 468. (See page 199.)

ROTARY PUMPS.

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

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

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

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

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

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

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

Fig. 469.

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

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

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

Fig. 470.

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

Note.—In the year 1825, one Mr. J. Eve, an American, took out a patent in England which was practically the beginning of the modern era of rotary engines and pumps. His pump consisted chiefly of a revolving cylinder having three teeth or projections and revolved within a case. A second and smaller cylinder was also placed within this case. The smaller cylinder had one side scooped out to permit each of the teeth upon the large cylinder to pass as they came opposite the small cylinder. The two shafts being geared together the small cylinder was caused to revolve three times to one of the large so that the teeth might pass the small cylinder without interruption.

Figs. 471 and 472.

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

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

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

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

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

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

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

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

Fig. 474.

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

Figs. 475-477.

Fig. 478.

Figs. 479-481.

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

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

Directions for setting and operating Taber pumps.

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

2nd. See that all parts are well oiled.

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

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

Note.—Many of the modern breweries are built with the hop-jack situated upon the upper floors of the brewery, to which the beer and hops mixed are pumped, and the beer allowed to flow directly to the coolers. This pump has been very successfully installed for the past five years, pumping in some breweries 90 feet in height above the pump. The handling of wet brewers’ grains by use of chain conveyors, which are seldom free from infection and which are a continual source of annoyance from breakage, is now overcome by this pump. All styles of these pumps can be washed out clean after use, thereby overcoming entirely the noxious smell so disagreeable to this part of the brewery when conveyors are used. There should be a fall of six to eight feet from the wash-tub into the pump and as nearly perpendicular as possible. Right angle bends in the discharge pipe should also be avoided. By using twenty-four-inch bends wet grains at 70% moisture can be pumped without additional water.

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

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

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

Open all drips in cold weather to prevent freezing.

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

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

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

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

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

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

Fig. 482.

Fig. 483.

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

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

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

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

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

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

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

Fig. 484.

Fig. 485.—See page 205.

Fig. 486.—See page 210.

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

Fig. 487.

Fig. 488.

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

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

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

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

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

Note.—The operation of these machines is very interesting. A long flexible tube 12 to 15 inches in diameter drops down from the side of the vessel 20 to 30 feet or more to the bottom of the river or harbor upon which the dredging operation is being performed. The upper end of this tube is connected to an immense rotative centrifugal pump revolving at several hundred revolutions per minute and capable of handling many hundreds of tons of water per hour. The lower end of the tube is manipulated from the vessel against the sand bars and mud banks and as the water is sucked upward by the centrifugal pumps a very large proportion of sand and mud goes with it. The centrifugal pumps discharge this water with its suspended material into the tanks on board the vessel or into scows, where the heavy material quickly settles to the bottom, the water flowing back into the sea.

The mixture of sand and water which is drawn up the suction pipe is forced a distance of 3,800 feet through a 30-inch pipe to the place where it is to be deposited; the water draining off allows the solid matter to remain.

CENTRIFUGAL PUMPS.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Table.

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

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

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

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

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

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

Table.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

TURBINE PUMPS.