US2978989A

US2978989A - Pumps

Info

Publication number: US2978989A
Application number: US633412A
Authority: US
Inventors: Kenneth R Lung
Original assignee: Tait Manufacturing Co
Current assignee: Tait Manufacturing Co
Priority date: 1957-01-10
Filing date: 1957-01-10
Publication date: 1961-04-11
Anticipated expiration: 1978-04-11

Description

April 11, 1961 LUN 2,978,989

PUMPS Filed Jan. 10, 1957 2 Sheets-Sheet 1 FlG-l IIIIA INVENTOR.

KENNETH R. LUNG ATTORNEYS K. R. LUNG PUMPS 2 Sheets-Sheet 2 Filed Jan. 10. 1957 3 67 Q0563 2 44 6532 i fl y tf w a WM 5 3. w \w MW w 3 5 WW MM w I I 6 2 3 mxw m FIG-I062 6/ FIG-7 FIG-ll INVENTOR. KENNETH R. LUNG ATTORNEYS PUMPS Kenneth R. Lung, Dayton, Ohio, assignor to The Tait Manufacturing Company, Dayton, Ohio, a corporation of Ohio Filed Jan. 10, 1957, Ser. No. 633,412

3 Claims. (Cl. 103-102) This invention relates to centrifugal pumps.

The invention has special relation to multistage centrifugal pumps, including such pumps of the type adapted to be entirely submerged in the water or other liquid to be pumped, and the invention is particularly concerned with problems frequently encountered in such pump installations as a result of the presence of abrasive materials in the water, and which for convenience may be generally referred to as sand. A major trouble with sandy water is that when the pump is temporarily shut off, some of the sand may settle between complementary nearing surfaces, and such sand may and often does create suificient friction to make it difficult or even impossible to restart the pump. Furthermore, even if the pump can start again, sand in metal bearings is capable of doing sufiicient damage by scoring and the like as ultimately to interfere with proper operation of the pump.

A further problem in the handling of sandy water with multistage submersible pumps derives from the necessity for maintaining sufficient sealing between adjacent stages to minimize inefliciency resulting from recirculation of water within the pump. Such pumps are of comparatively small size, with correspondingly reduced proportions of their component parts, and this tends to increase the difficulty of maintaining adequate sealing while at the same time also increasing the likelihood of accumulation of sand between relatively moving sealing parts. The end result of such accumulated sand is usually either to damage the seal, to bind the pump against restarting, or both. I

It has in the past been a common practice, in considerable measure because of the difiiculties outlined above, to apply special treatment to a new well for the purpose of eliminating at least a major part of the more or less free sand before a pump is installed. For example, one such treatment is to bail the well with a large bucket having a check valve in the bottom thereof until the sand content of the water is reduced to a safe level for installation of a pump. This treatment may require as much as two or three days, and thus correspondingly adds substantial cost to the well in terms of both labor and equipment.

It is broadly the primary object of the present invention to provide a multistage centrifugal pump which is capable of pumping water containing the relatively large amounts of sand found in new wells with minimum possibility of abrasive damage to any parts of the pump as well as minimum likelihood of interference with proper starting even under conditions of intermittent operation in a new well.

An additional object of the invention is to provide a multistage centrifugal pump which is so unaffected by the presence of sand in the water being pumped thereby that it can be employed for prelirninary use on successive new wells for the express purpose of eliminating the major part of the loose sand therein and then replaced use of the well.

297,9 Patented Apr. 11, 1961 Another object is to provide a multistage centrifugal pump having the above outlined features wherein each impeller and its associated diffuser have cooperating portions constructed to form a running seal against recirculation of Water around the impeller and wherein the impeller is of special proportions developing a downstream thrust thereon in operation to maintain the sealing portions of the impeller and diffuser in sealing engagement.

It is also an object of the invention to provide a multistage centrifugal pump which is free of bearing surfaces capable of being jammed or otherwise damaged by the entry of sand and which in addition operates to cause any sand present in the water to bepumped therethrou-gh along with the water.

A further object of the invention is to provide a multistage centrifugal pump having all the above outlined features and further characterized by the small number and simplicity of construction of its component parts and the ease of assembly of these parts in the complete pump.

Still further objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings:

Fig. 1 is a partial view generally in axial section and showing a submersible multistage centrifugal pump con structed in accordance with the invention;

Fig. 2 is a detail sectional view of one of the impellers in the pump in Fig. l, the View being taken on the line 22 of Fig. 3; I

Fig. 3 is a detail view showing the front or inlet side of the impeller of Fig. 2 with a portion of the front shroud broken away;

Fig. 4 is an enlarged fragmentary section on the line 44 of Fig. 3;

Fig. 5 is a detail view in radial section through the casing of one of the pumping units of Fig. 1;

Fig. 6 is a greatly enlarged view of a fragment of Fig. 1 taken in radial section;

Fig. 7 is a projection of a fragment of the outer periphery of the diffuser plate in one of the pumping units of Fig. 1;

Fig. 8 is a detail elevational view showing the back side of the diffuser plate;

Fig. 9 is a section through the diffuser plate taken on the line 9 of Fig. 8; and

Figs. 10 and 11 are fragmentary sections taken on the lines 10-10 and 11-11, respectively, of Fig. 8.

Referring to the drawings, which illustrate a preferred embodiment of the invention, the cylindrical shell 13 which forms the main pump housing has an upper end cap 14 threaded at its upper end for connection to the lower end of the usual down pipe 15 by which the entire apparatus is suspended in a well. At the lower end of the shell 13 is an intake end cap 16 which is shown fragmentarily and supports the drive motor (not shown) in the usual way. The drive shaft 17 of the motor is connected by a coupling 18 with the pump drive shaft 2b which extends through substantially the entire length of the shell 13 to drive the plurality of pumping units or stages therein.

These several pumping units are of identical construction, and the component parts of each unit are an impeller 21, a diffuser plate 22, and a casing 23 which encloses its associated impeller and dilfuser. These multiple pumping units are clamped between the end caps 14 and 16 in stacked relation along shaft 20 with the inlet of each unit arranged as described hereinafter to receive the output of the next lower unit. The main inlet of the pump is through the intake end cap 15 as indicated at 25, and the discharge from the uppermost unit reaches the downpipe 15 through a port 26 controlled by a check valve 27 and sealing washer 28. j

Since all of the impellers 21 are of identical structure, one is shown in detail in Figs. 24 as including a hub having internal splines 31 for driving engagement in a corresponding keyway 32 in shaft 26. The back shroud 33 of the impeller extends radially outwardly from the hub 3i), and a cylindrical sleeve 34 projects rearwardly from the hub beyond the back shroud. The front shroud 35 of the impeller is connected with the back shroud 33 by a plurality of impeller vanes 36, and it is of substantially greater diameter than the back shroud and preferably of an outer diameter just enough less than the inner diameter of casing 23 to assure running clearance therebetween.

A convenient manner of constructing this impeller is to cast it initially as two pieces of plastic material, one including the hub and back shroud and the other including the front shroud and vanes. Lugs 37 are included on each vane and are received through complementary holes 33 in the back shroud and then riveted over to secure the assembled parts together. This arrangement is shown in detail in Fig. 4, which also shows how the holes 38 are initially countersunk to assure riveting of the lugs 37 into flush relation with the outer surface of the back shroud 33. I

The front shroud 35 of the impeller includes an annular boss 49 which cooperates with the front end portion of the hub 30 to define an annular inlet 41 to the interior of the impeller. The interior of the boss 44) is provided with a .counterbore 42 which receives a complementary cylindrical flange 44 extending inwardly from the periphery of the corresponding inlet opening in the center of each casing 23, and the front or lower endof the boss 4% is adapted to engage an annular inner surface portion 4-5 of the associated casing. The remainder of each casing '23 is generally cup-shaped, and each casing is provided at the outer edge of the front thereof with a circumferential notch or shoulder 46 which forms a seat for the rearward edge for the adjacent casing upstream thereof. In addition, the rearward edge of each casing 23 is provided with a plurality of notches 47 for interlocking engagement with the associated diffuser 22 as described in more detail hereinafter.

Each diffuser 22 is a. single subassembly in which the major component is an annular web 50 shown as cast from a plastic material, and in the center of this web 50 is a bushing 51 of stainless steel or other suitable material. As shown in Fig. 9, the bushing 51 is provided with a circumferential groove 52 which assists in holding it in assembled relation within the center of web 50, and the downstream end of the bushing includes a fiat annular shoulder 53 which overlies the front of the web and projects forwardly of the surrounding area of the web to form an annular bearing surface for engagement with the back shroud 33 of the associated impeller.

With this construction, if the impeller can be maintained during operation with its back shroud in running engagement with the bearing surface 53, an adequate seal will be established against recirculation of liquid which at the same time will be effectively immune to damage by sand. This result is obtained in accordance with the invention by predetermined proportioning of the relative areas of the front and back shrouds of the impeller to produce a thrust force axially of the impeller in the upward or downstream diretcion while the pump is in operation. For example, satisfactory results from this standpoint have been obtained with an impeller wherein the front shroud has inner and outer diameters of 1.00 inch and 2.938 inches respectively as compared with inner and outer diameters for the back shroud of .658 inch and 2.3125 inches.

It is also important in order to obtain the maximum advantages of the invention that the relative proportions of the sleeve 34 on the impeller and thebushing 51 be such that there is always sufficient clearance'tliereb'etween to prevent possible interference with the free rotation of the impeller by the entry of sand between the relatively rotating surfaces of this sleeve and bushing. For example, with an impeller of the shroud dimensions noted above, satisfactory results have been obtained with an outer diameter of .658 inch for sleeve 34 and an inner diameter of .718 inch for the bushing 51. This provides an average radial clearance of .030 inch for the sleeve 34 in the bushing, which is ample to prevent possible binding action therebetween caused by the entry of sand even while the pump is shut off.

Desirable results are obtained in the performance of the pump of the invention if the impeller is formed from a plastic material such as a nylon resin which possesses good bearing qualities and will therefore run with minimum friction in sealing engagement with the surface 53. If in addition the material of the impeller possesses substantial resiliency, as is also the ease with nylon, this gives the further advantage that the parts have highly effective resistance to wear even if the shaft 26 should tend to wobble as a result of the large clearance between each impeller sleeve 34- and its associated bushing 51. It should also be noted that if the material of the impeller has a tendency to swell in water, the initial proportions of the impeller should be predetermined to assure that the difference between the maximum outer diameter of sleeve 34 and the inner diameter of bushing 51 will never be substantially less then in the above example.

With the impeller constructed as described, the web 59 of the diffuser 22 is of substantially greater diameter than the back shroud 33 of its associated impeller, and it approaches the diameter of the front shroud 35. The web 50 is accordingly provided at its periphery with a cylindrical rim 55 which overhangs the periphery of the shroud '33 and thus in effect forms a continuation of the back shroud for cooperation with the front shroud to guide the liquid flow outwardly from the impeller. The rim 55 is of sufliciently smaller outer diameter than the inner diameter of the associated casing 23 to provide a space therebetween, and in this space lie a plurality of generally helical fins 56 which project outwardly from rim 55 as best seen in Figs. 7 and 9. Each of these fins in turn terminates in a shoulder 57 proportioned toengage within one of the notches 47 in the back edge of the associated casing 23 in order to lock the diffuser and casing together.

The fins 55 cooperate with the outer periphery of the diffuser plate and the inner surface of the associated casing 23 to form a plurality of passageways 60 leading rearwardly from the outer periphery of the assoicated impelled along the inner surface of the casing 23 toward the back of the diffuser. Additionally, the diffuser includes a plurality of generally spiral vanes 61 on the back surface of web 54) which extend from a position near the hub 51 to the outer periphery of the web and include outer wall portions 62 which are cylindrically curved and angularly spaced with respect to each other and which merge with the rim 55. These vanes 61 thus cooperate with the inner surface of the casing 23 to define diffuser passageways which form continuations of passageways 60 and are of increasing flow area with respect to the passageway 60 for slowing down the velocity of the liquid with respect to its velocity through the passageway 60 before this liquid is conducted inwardly from the diffuser passageways for delivery to the inlet of the next casing and impeller.

This invention accordingly provides a pump wherein the only parts having relatively moving sealing engagement in operation are the bearing surfaces 53 and the adjacent surface portions of the associated impellers, and there is minimum tendency for sand to enter between these surfaces while the pump is running. Thus when the pump is stationary, each impeller is free to slip down the shaft until the boss 41 thereon seats on the inside of the associated casing, since the axial spacing between the bearing sunface 53 on each diffuser and the inner surface portion 45 of the associated casing is greater than the axial spacing between the surface of the back shroud 33 and the front end of the boss 40 to provide for corresponding free axial movement of the impeller with respect to the diffuser and casing through a predetermined distance equal to the difference between these two dimensions. It would therefore be possible then for sand to settle onto the back shroud while the pump is stationary, but as soon as the pump begins to rotate, centrifugal force would dislodge such sand even before sufficient upward thrust has been developed to move the impellers back upwardly to their positions in engagement with their associated bearing surfaces 53. This result is further assured by proportioning the hub of each impeller to provide a greater minimum axial clearance between the hubs of adjacent impellers than the distance each impeller can move individually with respect to its associated diffuser and casing as described, so that each impeller is prevented by engagement with its associated bearing surface 53 from engagement with the adjacent impeller downstream therefrom, and another result of this arrangement is that in operation, each impeller engages only one stationary surface and is free of engagement with its associated casing. It will also be noted that the parts are so constructed that when the boss 40 seats on the inside of the casing, it maintains space between the front shroud 35 and the inner surface of the casing open to the discharge pressure of the impeller when the pump again begins to operate, thus assuring that the desired upward thrust on the impeller will be established in operation. These structural features and this mode of operation in combination with the large clearance provided for the sleeve on each impeller in its associated bushing 51 as described has been found to give the pump the property of handling even the very sandy water present in a new well without appreciable wear of any of the pump parts.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that this invention is not limited to this precise form of apparatus and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. 'A multi-stage centrifugal pump of the character described comprising a housing, a drive shaft extending through said housing, a plurality of pumping units stacked axially within said housing and each including a casing of generally cup shape having a central opening in the front thereof, an impeller splined on said shaft for axial movement thereon within each said casing and including a hub and a back shroud extending generally radially therefrom, a front shroud on each said impeller, inlet means on each said front shroud for receiving liquid through said opening in the front of the associated casing and including an annular boss projecting forwardly and of larger diameter than said opening for engagement with the surface portion of said casing surrounding said opening when said pump is at rest to maintain space between said front shroud and said casing open to the discharge pressure of said impeller, a diffuser including an annular web received in each said casing behind said impeller therein, means maintaining said casings and said diffusers in axially and angularly fixed relation with said housing, means on the front of said diffuser web adjacent the inner periphery thereof forming an annular bearing surface for engagement with said back shroud, the axial spacing between said bearing surface of each said diffuser and said inner surface portion of the associated said casing being greater than the axial spacing between said back shroud and the front end of said boss on the associated said impeller to provide for free axial movement of said impeller with respect to said diffuser and casing through a predetermined distance, the area of said front shroud being greater than that of said back shroud to establish a greater efiective pressure axially of said impeller between said front shroud and said casing than between said back shroud and said diffuser web and thereby to cause said impeller to be moved out of engagement with the associatedsaid. casing in response to operation of said pump, and the axial length of said hub of each said impeller being proportioned to provide sufficiently greater axial clearance between said hubs of adjacent impellers than said predetermined distance of movement of each impeller to assure maintained running sealing engagement between said back shroud of each said impeller and the associated said bearing surface during operation of said pump.

2. A multi-stage centrifugal pump as defined in claim 1 wherein said hub of each said impeller includes a sleeve projecting axially rearwardly of said back shroud in telescoping relation with the associated said diffuser, the outer diameter of said sleeve being substantially less than the inner diameter of the surrounding portion of said diffuser to provide a correspondingly substantial annular clearance therebetween for preventing possible binding action therebetween resulting from the entry of sand.

3. A multi-stage centrifugal pump as defined in claim 1 wherein said hub of each said impeller includes a sleeve projecting axially rearwardly of said back shroud, a bushing secured in the center of each said diffuser web and including an annular shoulder projecting forwardly of said web and forming said annular bearing surface for engagement with said back shroud of the associated said impeller, said bearing surface being of substantially smaller outer diameter than said back shroud to maintain space between said web and said back shroud open to the discharge pressure of said impeller, and the inner diameter of said bushing being substantially greater than the outer diameter of said sleeve to receive said sleeve freely therethrough with a correspondingly substantial annular clearance therebetween for preventing possible binding action therebetween resulting from the entry of sand.

References Cited in the file of this patent UNITED STATES PATENTS 1,255,661 Stewart Feb. 5, 1918 1,495,167 Dixon May 27, 1924 1,902,431 Weis Mar. 21, 1933 2,753,807 Lung July 10, 1956 2,764,099 Wernert Sept. 25, 1956 2,775,945 Arutunofi? Jan. 1, 1957 2,791,182 Scheidl May 7, 1957 2,854,926 Haight et a1. Oct. 6, 1958 FOREIGN PATENTS 117,558 Great Britain July 25, 1918