US2282765A - Pumping apparatus - Google Patents

Description

May 12, 1942. J, MANN PUMPING APPARATUS Filed May 23, 1941 Ara/472E! Patented May 12, 1942 UNITED STATES (PATENT oF F 2,282,765 ICE PUMPING APPARATUS Application Ma, 23,

16 Claims.

My invention relates to pumping apparatus or systems, and is a continuation in part of my copending application Serial Number 326,445 filed March 28, 1940.

The line of demarcation between a so-called shallow well pumping system and a deep well pumping system has usually been considered to be the practical suction lift of a centrifugal pump, in the neighborhood of 22 feet. While, of course, a properly designed centrifugal pump will draw water from a lower level than this, adequate margins of safety have limited the use of centrifugal pumps to wells where the draw down level of water in the well does not exceed approximately 22 feet. In fact most manufacturers will not recommend a centrifugal pump where the suction lift is in excess of feet. Beyond this depth of well it has been customary to employ a reciprocating type of pump wherein the plunger of the pump is located in the well and is connected by a plunger rod to operating mechanism usually located at the ground level. In more recent years the jet type of deep well pump has attained considerable commercial success.

The primary advantages of a jet type deep well pump are that no moving parts are located in the well and the centrifugal pump, together with its prime mover, need not be located directly .over the well. This permits all moving parts of the system to be located in the basement of the building which the pumping is to serve, or in any other convenient position.

While the jet type deep well pumps now commercially employed have distinct advantages over other types of deep well pumps, they also have serious disadvantages.

Among these disadvantages is the fact that a portion of the liquid discharged from the centrifugal pump is continuously recirculated through the system and through the centrifugal pump. Air leaks into the system with the water being pumped and leaks into the system through piping joints. This infiltration of air into the system and lack of any adequate means for its disposal causes the centrifugal pump eventually to become air bound.

In a jet type deep well pump a certain quantity of liquid discharged from the centrifugal pump iscontinuously recirculated through the jet pump to supply energy for lifting water from the well. This quantity, for convenience, we shall call Ql. The usual manner of connecting the centrifugal pump, pneumatic tank, and jet pump, is to have a single discharge pipe connecting the centrifugal pump to the tank. The water discharged from the centrifugal pump to the tank we will designate, for convenience, Q2. The quantity Ql which goes down the well to supply the necessary energy to the jet pump does not pass through the tank, but instead separates from the quantity Q2 at a branch fitting, preferably placed close to the centrifugal pump discharge. The pneumatic tank in this arrangement serves as an air sep- 1941, Serial No. 394,838

arator, but only for the air entrained with the quantity Q2 which flows from the centrifugal pump discharge to the pneumatic tank. The re-. mainder'of the liquid discharged from the centrifugal pump, the quantity Ql, recirculates through the jet pump. Air entering the system with the water being pumped or through piping joints, or other possible leaks in the system, does not readily separate from the water, but at least a portion of it continuously circulates in the system with the quantity Ql. Air entering the system is largely retained in the piping because it tends to cling to the inner side walls of the pipes. If there is a suflicient accumulation of air-in the system, the centrifugal pump will become air bound and fail to create a difference in pressure between the suction inlet and the discharge outlet, and therefore will not supply energy to the jet pump to enable the jet pump to pick up water from the well. When this condition obtains the only way to remove the air is to stop the centrifugal pump for a sufficient length of time for the air to rise through the piping and pass to the pneumatic tank. This method of clearing the system of air is, of course, possible only where the system is carefully designed to avoid air pockets.

In wells where the draw down level of the well is in excess of 22 feet, it has been customary, in the past, to employ a reciprocating type of deep well pump. I am aware, while centrifugal pumps are not capable of reliable operation with a suction lift in excess of 22 feet unless specially designed, that special types of pumps, such as the so-called regenerative turbine pumps, have been used for wells where the suction lift is between 22 and perhaps 28 feet in depth. With my system I contemplate employing the combination of a jet pump and a centrifugal or pressure pump with the jet pump located in the well where the draw down level is in excess of 31 feet, at sea level and with the jet pump located adjacent or at the level of the centrifugal or pressure pump when the draw down level is less than 31 feet.

The present invention relates in particular to means for preventing, or at least minimizing, the recirculation or leakage of air back to the suction of the centrifugal or pressure pump. While the use of the principles of my invention is important in connection with a deep well jet pump, the invention will be described in connection with a shallow well jet unit. In a shallow well system the vacuum which the unit is capable of developing is particularly important. I have course, proper conditions, water may be pumped perature conditions. Experiments have also been found that with my system water may be drawn,

almost until the vapor tension of the water.;; reached at the existing pressure and water tern-- conducted to determine the air handling properties of the unit. It has been found that the unit, when connected to a sealed tank, will quickly exhaust the air therefrom and create almost a perfect vacuum therein.

An object of my invention is to provide a jet type pumping system which is of simple construction, economical to build, inexpensive to erect, and more reliable in operation.

Another object of my invention is tolprovide a jet type pumping system which is more reliable in operation than existing commercial systems, due to the provision of means for minimizing the possibility of the centrifugal pump becoming air bound.

Another object of my invention is to provide a unitary, compact assembly for a jet type shallow well pumping unit in which the centrifugal pump and the jet pump are housed in a single casting, and which is particularly designed for wells of from 22 to 31 feet total suction lift.

A further object of my invention is to provide a jet type pumping unit which when once primed cannot lose its prime and is capable of exhausting air from a suction line should the line become filled with air.

My invention further contemplates a jet type pumping unit in which means are provided to insure the supply of substantially air free liquid to the jet and to prevent or minimize the recirculation of air through the centrifugal or pressure pump and the leakage of air to the suction thereof.

Other objects and advantages of my invention will be more particularly pointed out in the claims, and will be apparent from the following description, when taken in connection with the following drawing in which:

Fig. 1 is a sectional view through a shallow well pumping unit in accordance with my invention.

Fig. 2 is a sectional view taken substantially on the line 22 of Fig. 1.

The jet type pumping system of my invention comprises, in general, as shown in Fig. l a pressure pump housed in a casting generally indicated by the numeral II, an air-tight pneumatic pressure tank (not shown) and a jet pump, indicated as a whole by the numeral l3. While the arrangement may be similar to that shown in my abandoned application, Serial Number 224,149,

filed August 10, 1938, for the reasons set forth in the above mentioned copending application, I prefer to employ between the pressure pump and the pneumatic pressure tank an air separating chamber or compartment generally indicated by the numeral I4.

It' will be understood, as shown and described in the above-mentioned copending application, that the system may be employed for deep wells, in which case the jet pump I3 is located in the well and has connected therewith a pressure pipe from the air separating chamber II, or may be arranged as shown in the drawing for shallow well operation. The pneumatic pressure tank has not been shown in the drawing for the reason that the present invention primarily concerns the means employed for preventing the recirculation of air to' the centrifugal pump and the means for preventing the leakage of air back to the suction of the pump.

The casting H which houses the pressure pump and the jet pump 13 is connected by a suction pipe or conduit (not shown) to a well pipe (not shown) which extends downward into the convenience.

well. The suction pipe is connected to a cornpartment I5 formed in the casting II. It will be noted that the pressure pump, generally indicated by the numeral l8, and the jet pump I3 are mounted in a single housing which may be made up of several castings for manufacturing The arrangement shown provides an inexpensive, compact assembly.

The pressure pump it may be of any suitable type. In the drawing I have shown a pump of the centrifugal type although it will be appreciated that other types of pumps may be substituted therefor as, for example, a regenerative turbine pump. The impeller 26 of the centrifugal pump may be of conventional construction except that it is provided, for the purposes which will later appear, with a relatively long, substantially cylindrically shaped portion 21 defining the suction inlet 28. The casing of the centrifugal pump is defined by the cover plate 29 which is secured, as shown at 3|, to the casting ll. Bolted to the under side of the cover plate is a casting 32 which forms the other half of the centrifugal pump casing. The casting 32 is provided with a machined bore 33 which has a relatively close clearance with respect to the rotating cylindrical portion 21 of the suction inlet.

As shown more clearly in Fig. 2, adjacent the periphery of the casting 32 is a pair of discharge outlets or channels 34 which are formed partly by guide vanes or walls 36 and 31. The channels gradually increase in cross-sectional area toward their outlets and serve the same general function as the conventional volute of a centrifugal pump. The liquid from the impeller is thrown outward into the space indicated by the numeral 38 which gradually increases in crosssectional area, and flows'out by the guide vanes 35 and 31 from the enlarged portions 39 adjacent the periphery of the casing. The guide vanes serve to convert the velocity energy of the liquid after it is thrown from the impeller of the centrifugal pump into pressure energy. After the liquid is discharged from the guide vanes it enters the enlarged chamber or compartment 4| formed in the casting l I.

One of the important features of my invention is the provision of means for preventing the centrifugal pump from becoming air bound. It will be appreciated, in pumping systems of the type described herein, that air leaks are likely to develop in the piping and that a certain amount of air is likely to be entrained in the water drawn throughthe pump. This air accumulates in the system, and if precautions are not taken, it is likely to cause the centrifugal pump to become air bound. All of the liquid discharged from the centrifugal pump passes first to the chamber 4|. In this chamber partial liquid and air separation take place and particularly that portion of the liquid that flows to the wearing ring, later to be described, has the air separated from it. The liquid and air then pass to therair separating chamber I4 in which complete liquid and air separation may take place. It will be noted that the air-separating chamber has a baffle 40 which separates the liquid entrance to the air separating chamber from the outlet opening 42. The liquid for feeding the nozzle of the jet is supplied entirely from the air separating chamber through the liquid outlet 42 and the passage 43 formed in the casting .l l. Thus the liquid'supply to the jet pump is substantially air free.as fully described in the above mentioned eopending application, so that the air is prevented from recirculating through the centrifugal pump.

The compartment 4| is defined by a casting wall 44 which has an opening 4 through which the cylindrical suction inlet extends. The space between the margins of the opening 66 and the outer wall of the cylindrical suction inlet is substantially sealed by a sealing ring 4!;

In the above mentioned copending application a sealing ring is shown which is set on a bushing fixed to the wall as of the compartment M. The sealing ring is free floating and free to rotate. While this arrangement can be used, I have found, when the pump is employed with sandy water conditions, that particles of sand tend to lodge between the parts and the ring turns with the impeller. of friction between the bottom of the wearing ring and the top side of'the bushing and may cause the motor for driving the pump to become overloaded. In the arrangement shown a wearing ring is employed which has a projection 49 adapted to engage a projection 5| formed in the casting 82. This arrangement prevents the wearing ring 41 from rotating with the impeller but still permits the wearing ring to float and adjust itself with respect to the axis of the impeller.

-As shown in the drawing, the cylindrical part 21 of the impeller is provided with a sleeve 52 which may be accurately machined and shrunk on the impeller. Extremely close clearance between the inner surface of the wearing ring and the outer surface of the sleeve 52 may thus be obtained. The sealing ring is maintained against the wall 44 of the compartment M by the pressure differential on opposite sides of the sealing ring. The lower side of the sealing ring is exposed to, the pressure of the suction inlet, while the upper side of the ring is exposed to the greater pressure in the chamber or compartment 4|. To increase the effectiveness of this pressure difierential in sealing the surfaces between the ring and the wall 44, the lower side of the ring is somewhat countersunk, as shown, so that the surface of the ring bearing against the wall 44 is of limited annular area.

As previously mentioned, the guide vanes or channels 34 in the casting 32 serve to convert velocity into pressure energy. For this reason the pressure in the chamber 4| is greater than that in the pump casing defined between the cover plate 29 and the casting 32. As shown in the drawing, a small space 53 exists between the casting 32 and the floating ring 41 so that the cylindrical portion 21 of the suction inlet is subjected to the pressure in the chamber 4|.

. Thus the liquid from the chamber 4| will tend to flow through the clearance provided between the cylindrical sleeve 52 of the suction inlet and the sealing ring to the suction inlet and also from the chamber 4| through the space between the bore 33 in the casting 32 and the outer surface of the sleeve 52.

As previously mentioned, the chamber or compartment 4| is of sumcient volume and the velocities of the liquid therein are sufiiciently low so that liquid flowing from the pressure chamber 4| to the suction inlet is substantially air-free. Thus, not only is the liquid recirculated through the jet pump substantially air-free but also the leakage liquid from the compartment 4| is also substantially freed of air so that air cannot'accumulate in the centrifugal pump or its casing. Moreover, the casing of the centrifugal pump is effectively sealed from the suction inlet 28.

This results in the development The above sealing arrangement for preventingair from recirculating through the centrifugal pump is particularly important in a pumping system of the type with which my invention is concerned for the reason that the system is designed for relatively high suction lifts. With the suction lift approaching 31 feet, the vacuum produced at the suction inlet is extremely high, this high vacuum tends to draw all the air in the system to the suction inlet. Unless suihcient precautions are taken, the air may continuously recirculate through the centrifugal pump or, with leakage from other sources, suflicient accumulation of air may cause the centrifugal pump to become air bound. Moreover, any accumulation of air in the pump destroys or decreases the vacuum producing properties of the pump.

In addition, the most reliable and simplestfor replenishing the pneumatic tank quickly I passes through the centrifugal pump and is prevented, by the means above described, from recirculating therethrough and accumulating in the system.

One of the problems encountered in experimenting with the system of the above mentioned application was that, notwithstanding the precautions taken, air in sufficient quantities to affect the vacuum producing properties of the pump to a serious extent was circulating through the pump. The source of this air leakage was for a considerable time not discovered. It was finally found that the air tended to cling to the underside of the casting 32 forming half of the pump housing. This air, because of the vacuum produced at the suction inlet, tended to creep along the casting wall to the suction inlet. This condition particularly existed in connection with the liquid and air discharged from the righthand passage 34.

It was found that this creepage 'air could be substantialy entirely eliminated by providing the lower side of the casting with an annular depending skirt or baflle 6|; The skirt should preferably be located adjacent the suction inlet andshould,

ural tendency isfor the air to rise in the chamber 4|, the use of a baiiie or obstruction in the chamber 4| has been found very desirable for substantially eliminating the air recirculated to the suction above mentioned.

As previously mentioned some difliculties were encountered when pumping sandy water. These difficulties were partly eliminated by employing the sealing arrangement above mentioned. In addition, I have found it desirable to employ a screen between the discharge outlet from the pump casing and the suction inlet. The screen, indicated by the numeral 62, extends preferably completely around the suction inlet and may be supported by lugs 63 cast integral with the casting 32. Even under extremely sandy conditions the screen requires only infrequent cleaning.

One of the advantages of employing a screen is that the clearance between the sealing ring 41 and the cylindrical elementforming the suction opening may be made a minimum since sufficient clearance for the passage of large sand particles is not required. I have found a clearance between these parts of three-thousandths of an inch to be sufficient particularly when a screen is used.

On tests it has been found when this clearance is reduced from, for example, one-hundredth of an inch to three-thousandths of an inch, that the vacuum producing properties of the'unit are materially increased with this change in clearance. Thus, and with a small unit, the time required was reduced from 17 to 12 minutes to exhaust the air from a two-gallon tank and obtain a vacuum equivalent to a thirty foot suction lift.

Moreover, with sandy water conditions the water on the parts is excessive resulting in increased clearance at the wearing ring. This reduces the vacuum producing properties of the pump. When a screen is employed the wear is materially reduced. An increase in wearing ring clearance also causes an increase power consumed and a decrease in the shut off pressure which the pump is capable of developing.

Similar tests (.003 clearance) have showna reduction in time required to exhaust the tank to a pressure equivalent to a suction lift of thirty feet from twelve minutes, when no skirt or screen is employed, to only four minutes when the baflle in the chamber 4| is employed. It will of course be appreciated that the screen will, to a certain extent, serve the same function as the skirt GI and may permit elimination of the skirt. However, I believe that the best results will be obtained if both a screen and a skirt are employed.

While I have shown and described the preferred form of my invention, it will be appreciated that various changes and modifications may be made therein, particularly in the forms and relation of parts, without departing from the spirit of my invention as set forth in the appended claims.

I claim:

1. A unitary pumping system comprising a centrifugal pump having a rotatable impeller, a stationary casing having an outlet through which the impeller discharges, a stationary chamber into which that outlet empties and in which air and liquid separation may take place, said impeller having a suction inlet, and means for sealing said casing from said suction inlet comprising a sealing ring between the stationary chamber and the rotating impeller inlet.

2. A unitary pumping system comprising a centrifugal pump having a rotatable impeller, a stationary casing having an outlet through which the impeller discharges, said impeller having a substantially cylindrical suction inlet terminating in an opening, the outer rotating surfaces of which are closely adjacent the surrounding portion of the casing, a stationary chamber into which said outlet empties and in which air and liquid separation may take place, sealing means between the stationary chamber and said suction inlet, a portion of the cylindrical surface of the suction inlet between said sealing means and said casing being subjected to chamber pressure to prevent the passage of fluid from the casing to the suction inlet opening.

3. A pumping system comprising, in combination, a pressure pump, a chamber having an inlet into which the discharge of said pressure pump flows, a jet pump having a nozzle, said chamber having an outlet connected with the nozzle of the jet pump and said jetpump communicating with the pressure pump, the liquid flowing to said nozzle being removed from the chamber at a point with respect to the liquid inlet from the pressure pump such that liquid and air separation take place in the chamber and the liquid flowing to said nozzle is substantially air free, said pressure pump having a rotatable impeller with an inlet, a stationary casing having an outlet through which the impeller discharges, a stationary compartment into which said outlet empties prior to passage to said chamber, and means for sealing said casing from said suction inlet comprising a sealing ring between the stationary compartment and the rotating impeller inlet.

4. A pumping system comprising, in combination, a rotatable impeller having a suction inlet formed by a substantially cylindrical member, a stationary casing for said impeller having an outlet through which the impeller discharges, a stationary chamber into which said outlet empties and in which the liquid pressure is normally above that within the casing, the exterior surface of said cylindrical member between said casing and said inlet being subject to the pressure of said chamber to prevent the flow of liquid from said casing to said inlet.

5. A pumping system comprising, in combination, a rotatable impeller having a suction inlet formed by a substantially cylindrical rotatable member, a stationary casing for said impeller having an outlet through which the impeller discharges, said casing having an opening through which said cylindrical member extends, a chamber into which said outlet empties, the pressure of liquid in said chamber being above that in said casing and above that at said inlet and the exterior surface of said cylindrical member being exposed to the pressure of said chamber between the casing and the inlet whereby the leakage flow of liquid is from said chamber to said casing and to said inlet and said inlet is effectually sealed from said casing.

6. A pumping system comprising, in combination, a rotatable impeller having a suction inlet formed by a substantially cylindrical rotatable member, a stationary casing for said impeller having an outlet through which the impeller discharges, said casing having an opening through which said cylindrical member extends, a chamber into which said outlet empties, the

pressure of liquid in said chamber being above that in said casing and above that at said inlet and the exterior surface of said cylindrical member being exposed to the pressure of said chamber between the casing and the inlet whereby the leakage flow of liquid is from said chamber to said casing and to said inlet and said inlet is eflfectually sealed from said casing, and a sealing ring between said rotatable cylindrical member and said chamber.

7. A pumping system comprising, in combination, a rotatable impeller having a suction inlet formed by a. substantially cylindrical rotatable member, a stationary casing for said impeller having an outlet through which the impeller discharges, said casing having an opening through which said cylindrical member extends, a chamber into which said outlet empties, the pressure of liquid in said chamber being above that in said casing and above that at said inlet and the exterior surface of said cylindrical member being exposed to the pressure of said chamber between the casing and the inlet wherein said chamber beneath which the liquid said chamber to said inlet is substantially air free.

8. A pumping system comprising, in combination, a rotatable impeller having a suction inlet, a casing for said impeller having an outlet through which said impeller discharges, a chamber into which said outlet empties, said chamber being so constructed and arranged as to enable at least partial liquid and air separation to take place in the chamber, said chamber having a leakage opening to the suction inlet, and a baflie flows to gain access to the suction inlet.

9. A pumping system comprising, in combination, a rotatable impeller having a suction inlet, a casing for said impeller having an outlet through which the impeller discharges, a chamber into which said outlet empties, said chamber being so constructed and arranged as to enable at least partial liquid and air separation to take place in the chamber, said chamber having a leakage opening to the suction inlet, and a screen in said chamber between said casing outlet and the suction inlet.

10. A pumping system comprising, in com-- bination, a rotatable impeller having a suction inlet, a casing for said impeller having an outlet through which the impeller discharges, a chamber into which said outlet empties, said chamber being so constructed and arranged as to enable at least partial liquid and air separation to take place in the chamber, said chamber having a leakage opening to the suction inlet, a bafiie in said chamber beneath which the liquid flows to gain access to the suction inlet, and a screen in said chamber between said casing outlet and the suction inlet.

11. A pumping system comprising, in combination, a rotatable impeller having a suction inlet, a casingv for said impeller having an outlet through which the impeller discharges, a chamher into which said outlet empties, said chamber being so constructed and arranged as to enable at least partial liquid and air separation to take place in the chamber, said chamber having a leakage opening to the suction inlet, and means in said chamber between said casing outlet and the suction inlet for minimizing creepage flow of air along the walls of said chamber to the suction let.

12. A pumping system comprising, in combination, a rotatable impeller having a suction inlet formed by a substantially cylindrical rotatable member, a stationary casing for' said impeller having an outlet through which the impeller discharges, said casinghaving an opening through which said cylindrical member extends, a chamber into which said outlet empties. the pressure of liquid in said chamber being above that in said casing and above that at said inlet and the exterior-surface of said cylindrical member being exposed to the pressure of said chamber between the casing and the inlet whereby the leakage flow of liquid is from said chamber tosaid casing and to said inlet and said inlet is efiectually sealed from said casing, said chamber being so constructed and arranged as to permit at least partial liquid and air separation to take place therein, and means in said chamber between said casing outlet and the suction inlet for minimizing creepage flow of air along the walls'of said chamber to the suction inlet.

13. A pumping system comprising, in combination, a rotatable impeller having a suction inlet formed by a substantially cylindrical member, a stationary casing for said impeller having an outlet through which the impeller discharges, a stationary chamber through which said outlet empties and in which the liquid pressure is normally above that within the casing, the exterior surface of said cylindrical member between said casing and said inlet being subject to the pressure of said chamber to prevent the flow of liquid from said casing to said inlet, and means in said chamber between said casing outlet and the suction inlet for minimizing creepage flow of air along the walls of said chamber to the suction inlet.

14. A pumping system comprising, in combination, a rotatable impeller having a suction inlet, a casing for said impeller having an outlet, a chamber into which liquid flows from said outlet, a jet pump having a nozzle, the nozzle of the jet pump being supplied with liquid from said chamber and the jet pump discharging to the suction inlet of said impeller, and means in connection with said chamber for preventing flow of liquid from said casing to said inlet without passing through said chamber.

15. A pumping system comprising, in combination, a rotatable impeller having a suction inlet formed by a substantially cylindrical member, a stationary casing for said impeller hav ng an outlet through which the impeller discharges, a stationary chamber into which said outlet empties and in which the liquid pressure is normally above that within the casing, the exterior surface of said cylindrical member between said casing and said inlet being subject to the pressure of said chamber to prevent the flow of liquid 'from said casing to said inlet, and a jet pump having a nozzle, said nozzle receiving liquid from said chamber and said jet pump discharging into said suction inlet.

16. A pumping system comprising, in combination, a rotatable impeller having a suction inlet formed by a substantially cylindrical rotatable member, a stationary casing for said impeller having an outlet through which the impeller discharges, said casing having an opening through which said cylindrical member extends, a chamber into which said outlet empties, the pressure of liquid in said chamber being normally above that in said casing and above that at said inlet and the exterior surface of said cylindrical member being exposed to the pressure of said chamber between the casing and the inlet whereby the leakage flow of liquid is from said chamber to said casing and to said inlet and said inlet is efiectually sealed from said casing, said chamber being so constructed and arranged as to permit at least partial liquid and air separation to take place therein, and a jet pump arranged to receive liquid from said chamber and discharge said liquid together with the liquid pumped toward said suction inlet.

JOHN MANN.

Images