US2389753A - High pressure centrifugal pump - Google Patents

Description

Nov. 27, 1945. BABE HIGH PRESSURE CENTRIFUGAL PUMP 2 Sheets-Sheet 1 Filed Sept. ll, 1943 w A, I l( d I., a m I Ivy/J, A/

With/1.1.1 7

Nov. 27, 1945. C. L, BABE HIGH PRESSURE CENTRIFUGAL PUMP 2 Sheet-.Sheet 2 Filed Sept. ll, 1945 internal passages.

I. Patented Nov. 27, 19.45-

`HIGH PRESSURE CENTBIFUGAL PUMP Charles L. Babb, Wauwat-osa, Wis., assignor 4to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application September 11, 1943, Serial No. 501,910

8 Claims.

This invention relates to improvements in centrifugal pumps and particularly to centrifugal Dumps which are required to handle relatively small quantities of liquid at very high pressures.

In the usual centrifugal pumps, the pump casing is divided on a horizontal plane through the horizontal axis of the pump for conveniencein manufacture and maintenance. And the volutes which produce conversion of the impeller discharge from velocity'into pressure, are normally cast as parts of the casing. The high velocities produced in such high pressure pumps require that the volute passages be carefully shaped to secure the area and contour which will produce the most effective velocity-pressure conversion and that such passages be so finished as to avoid local turbulences and to minimize friction. The volute passages in high pressure pumps handling relatively small quantities of liquid are however very small in cross-sectional area and relatively complicated in shape thus making it very diilicult to secure the proper iinishing of the passage surfaces by chipping and grinding which are the l only metal surfacing processes available.

When such pumps are used to supply a relatively small quantity of water such as 1000 g. p. m.

at pressures of the order of 1800' pounds per square inch as in present day boiler feed pumps, the high velocities encountered cause erosion particularly in the volute passages receiving the discharge from the impellers where the velocity is highest. The cavities formed by such erosion must be illed by welding 'proper material into the cavities and must then be ground to the proper contour and finish. The operations required for repairing erosion in pump volutesy'are always expensive and frequently the erosin takes place in locations in which it is extremely diiilcult to do satisfactory welding or grinding.

In high pressure centrifugal pumps .it was also found that it is exceedingly diiiicult to provide sumcient bolting to keep the horizontal joint tight, Prior constructions have been provided with two rows of bolts to hold the upper and lower casing parts together at the pressure mentioned. 'I'he inner row of bolts was located in portions of the pump casing between the several pump impellers as close to the horizontal axis of the pump as Apossible without interference with thev various 'I'he inner row of bolts was accordingly placed in portions of the casing surrounded atleast in part by internal passages and projecting from the outer wall of the casing inwardly toward the center thereof. And the outer row of bolts was necessarily placed outside of the outer walls of the internal passages. However, even the inner roW of bolts was still a considerable distance from the center line of the pump and it was difcult to exert suiilcient pressure thereon to produce a tight joint. Consequently at the high velocities encountered in pumps producing high pressures, erosion takes place at those portions of the joint projecting into the 'regions of high velocity and continues to such extent as to cause leakage to the exterior of the joint regardless of the pressure exerted by the outer row of bolts.

If the pump casing is bored out to such diameter as to permit the formation of volute passages within the bore with solid interstage diaphragms extending from the casing to support the pump shaft and the impellers, casing projections between the several impeller stages of the pump are eliminated and a single row of bolts can be provided which are placed at substantially uniform distances from the center line of the pump which was impossible heretofore. It is accordingly possible to secure a uniform distribution of pressure over the entire joint surface and to avoid points at which erosion may occur in the joint. The volute passages may then be formed as separate castings or may be made as a built up construction which may be individually nished to the contour and finish required and may then be secured in the bore of the casing. Any single volute may then be removed for repair and replacement whenever desired.

'It is therefore an object of the present invention to provide a centrifugal pump in which at least the high velocity receiving portions of the volute passages are formed and finished separately and are then secured within the pump casing.

Another object of the invention is to provide a centrifugal pumpin which the casing is bored out as a cylinder to receive at least the high velocity portions of the volute passages as structures to he inserted and seated in such bore.

Another object of the invention is to provide a centrifugal pump in which the volute passages are formed from separate diaphragms extending into a bore within the casing from the wall thereof with separate volute pieces placed between the diaphragms and shaped to provide the desired volute passage cross section.

Another objectof the invention is to provide a. y

"centrifugal pump with separate diaphragms between the several impeller stages and extending inwardly from the outer wall of the pump casing to form supports for the pump shaft and pump impellers. l

Another object of the invention is to provide a centrifugal pump for producing high pressure in which the horizontal joint in the pump casing is kept tightly closed by a single row of bolts providing a uniform distribution of pressure over the entire casing joint' area.

'Objects and advantages other than those above set forth will be apparent from the following de. scription when read in connection with the accompanying drawings, in which: l

Fig. 1 is a vertical cross-sectional view of a pump constructed according to the present invention, the view being taken on a vertical plane through the longitudinal axis of the pump;

Fig. 2 is a vertical cross-sectional view taken on the plane of line II-lI of Fig. l;

Fig. 3 is a vertical cross-sectional view taken on the plane of line III-III of Fig. 1;

Fig. 4 is an enlarged fragmentary view taken on the plane of line IV-IV of Fig. 5 to show in detail, the manner in which the several separate portions forming the circumferential volute pieces are mounted and fastened in the casing of the pump;

Fig. 5 is a horizontal cross-sectional view taken on the plane of line V-V of Fig. 4 to illustrate the manner of mounting and securing the several volute forming diaphragms in the pump casing and to the circumferential volute portions to prevent both axial and rotational movement of such diaphragms, and

Fig. 6 is a view taken on the plane of line VI-VI of Fig. 4 to illustrate the p ,rticular configuration of the water conducting surface of the several portions forming one of the volutes.

Referring more particularly to the drawings by characters of reference, the reference numeral I I designates the lower portion of a pump casing and reference numeral I2 designates the upper portion o'ffa pump casing, the portions being formed by divisionv of the casing on a horizontal planeV through vthe longitudinal axis of the pump. Each of the casing halves is cast with the appropriate .portions of the various internal passages so that joining of the casing halves completes the inlet passage I3, the interstage passages I4 and I5 and the discharge passage I6. The two casing halves are joined and are bored out on the axis of the pump to provide a cylindrical space somewhat larger than the diameter of the pump impellers. Such boring out of the casing provides a smooth finish on the interior of the casing and allows access to all `portions of the above mentioned casing passages to provide for finishing of the surfaces thereof. All of the bolts I1 joining the two casing halves are set in a straight line in the casing flanges and relatively closely to the edges of such flanges thus providing considerable simplification in the -bolt arrangement and placing the bolts in the best possible positions to secure uniform distribution of the pressure over the entire casing joint surfaces thereby preventing separation of such flanges.

A shaft 2| extends through casing II, I2 and is sealed in the casing at the ends thereof by a pressure reducing bushing 22 spaced from the usual packing 23 and packing glands 24. A plug rality of double inlet impellers 26 are mounted on the shaft in spaced relation to be severally supplied by a liquid to be pumped by way of passages I3, I4and I5. As shown, the impellers are preferably of the double inlet type which are inherently balanced in the axial direction. Shaft 2| of course is protected against contact with the liquid by sleeves 21 made of non-corrosive material.

With the interior of the pump casing formed as a smooth cylinder, the usual volute passages into which the impellers discharge, are formed by separate pieces mounted in the bore in the casing halves. As is shown in the drawings, 'each volute passage is made of the circumferential volute pieces 3|, 32 and 33 set into and secured in the casing and enclosed at the sides by the daphragms 4| and 42. The circumferential portions of the volutes are substantially segr. ents of a hollow cylinder and are necessarily made in three pieces because the casing is horizontally split and because a passage of the full cross-sectional area of the volute passageway must be provided to allow flow of the liquid from the volute into the passage leading to the inlet of the next stage. And the several circumferential volute pieces Yare also nec-J essarily made with inner surfaces of different degrees of concavity and with increasingly greater depth from the so-ca'lled lip or cut-off point to the point of discharge from the volute. Thus the contour of the volute piece 3| varies from a substantially fiat surface at the cut-off end to a concave surface of material depth at the end joining the volute piece" 32, the depth of the volute piece 32 increases toward its end adjacent the volute piece 33 and even though the volute piece 33 is very short, the depth of its concave surface increases from the end adjacent the piece 32 to the discharge passage. Such constant change of depth and degree of concavity provides volute passages of constantly increasingv area from the 'cut-oli' point to the discharge passage thus providing for uniform conversion of velocity to pressure throughout the entire volute. The circumferential volute pieces are individually held in position by pins 34, 35, 36, 31 and 38 extending through such volute pieces and threaded into the casing and the inner ends of the pins are fastened by welding to the volute pieces. It will be understood that the inner ends of the pins are ground to conform with the adjacent volute surfaces.

The diaphragms 4I, 42 are each made as separate plates and extend 4from the interior surface of the casing bore to adjacent the inlet edges of each of the double inlet impellers 2B where suitable wearing rings are provided. Each of the diaphragms is accordingly annular in shape and each pair of diaphragms together with the circumferential volute pieces as described above. combine to forma complete volute inciosure for the discharge edge of an impeller 26 and'for converting the velocity of the discharged liquid into pressure. The diaphragms 4| and 42 are provided on the outer periphery thereof with tongues 43 fitting into matching grooves 44 in the casing. the grooves being so located that the inner surfaces of the diaphragms contact with the sides of the volute pieces 3|, 32 and 33. The diaphragms are accordingly held against lateral displacement by their tongue and groove joints with the casing and are held against rotational movement by pins 46 threaded into the diaphragms from the inner surface thereof and extending into matching apertures between the volute portions 3| and 32 formed by matching semi-circular grooves in the circumferential volute pieces on the horizontal division plane of the casing. The diaphragms are assembled on the shaft in their proper relation to the impellers and placed in thelower casing half ings. The diaphragms are then locked in place Patent:

.seated in grooves provided therefor in split sleeves i 53 fitting on the impeller shaft 2|. and forming i bushings between impeller stages which reduce interstage leakage to a minimum. 'I'he grooves in the casing and in the bushings l53 prevent lateral displacement of the interstage diaphragms and bushings. Each of the diaphragmsl is provided with one or more ns 54 extending into the space adjacent the volute inclosures and pins 55 are fixed in the casing adjacent the diaphragms.V The diaphragms may rotate until one or the other fins is stopped by the pin which then prevents further rotational movement of the diaphragm.

The interstage diaphragms are therefore held4 against both lateral and rotational displacement after seating in the grooves and against the pin respectively. 'I'he diaphragms 5l are integral and hence must be mounted on the shaft 2| at the time the several impellers 26 and the volute diaphragms di, 62 are mounted thereon.

In the manufacture and assembly of the various parts of the pump, the flanges ofthe two casing halves are faced and drilled to receive the bolts. A boring bar and tool are inserted through the opening in the end of the casing for the bearings and extension of shafts therethrough and the casing is bored out on a given diameter. The interior of the pumpA casing is accordingly formed as a finished hollow cylinder and the grooves are likewise formed for receiving the tongues of the several diaphragms. The inlet, interstage and outlet passages are now finished by chipping and grinding to minimize resistance to the flow therethrough. Properly shaped and nished circumferential volute pieces are set into the casing on the surface of the bore and are fixed therein by pins extending through such pieces. The impellers and the interstage and volute diaphragms are assembled on the shaft and are lowered into the lower half of the casing to seat the tongues on the lower half of the interstage and volute diaphragms into the grooves provided therefor. ered on the lower casing half thus setting the tongues of all of the diaphragms into the grooves provided therefor in the upper casing half. The casing halves are then bolted together and the pump is completely assembled.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or the scope of the appended claims.

It is claimed and desired to secure by` Letters l. In a centrifugal pump, a casing divided through the longitudinal axis thereof, a shaft extending through said casing, an impeller mounted on said shaft, and an enclosure comprising volute pieces extending circumferentially about said impeller and divided into-a plurality of segments individually mounted in said casing and diaphragm plates extending at right angles to the axis of said shaft from adjacent said casing along opposite sides of said volute pieces and individually circumferentially mounted in said The upper casing half is lowcasing said enclosure being positioned within said casing about Asaid impeller and forming a volute passage receiving the uid discharged therefrom.

2. In a centrifugal pump, .a casing divided through thev longitudinal axis thereof, a shaft extending through said casing, an impeller mounted on said shaft, and an enclosure c`om prising volute pieces extending circumferentially about said impeller and mounted directly in saidv casing and diaphragm plates adjacent to and cooperating with said volute pieces and having circumferential tongues entering grooves in said casing to prevent lateral displacement of said plates, said enclosure being mounted in said casing about said impeller and forming a volute passage receiving the uid discharged therefrom.

3. In a centrifugal pump, a casing divided through the longitudinal axis thereof, a shaft Vextending through said casing, an impeller mounted on said shaft, and an enclosure coinprising volute pieces extending circumferentially about said impeller and mounted in said casing and diaphragm plates having circumferential tongues entering-grooves in said casing and having pins extending into said volute pieces from said plates to prevent lateral and rotational lmovements thereof respectively, said enclosure being mounted in said c'asing about said impeller and forming a volute passage receiving the uid discharged therefrom.

4. In a centrifugal pump; a casing divided through the longitudinal axis thereof, a. shaft extending through said casing, an impeller mounted on said shaft, and an enclosure comprising volute pieces extending circumferentially about said impeller and divided into a plurality of segments individually mounted in said casing and annular diaphragm plates peripherallyl mounted individually in said casing adjacent opposite sides of said volute pieces, said enclosure being mounted in said casing about said impeller and forming'a volute passage receiving the fluid discharged therefrom.

5. In a centrifugal pump, a casing divided through the longitudinal axis thereof, ashaft extending throughA said easing, -a plurality of impellers mounted on said shaft, sleeves on said shaft between said impellers, an enclosure mounted in said casing and forming a volute passage for receiving the fluid Adischarged therefrom, and an interstage diaphragm mounted in a groove in each of said sleeves, said diaphragms having tongues formed circumferentially thereon to enter grooves in said casing for preventing lateral displacement of said diaphragms.

6. In a centrifugal pump, a casing divided through the longitudinal axis thereof, a shaft extending through said casing, a plurality of impellers mounted on said shaft, an enclosure mounted in said casing and forming a volute passage for receiving the uid discharged therefrom, and interstage diaphragms severally mounted on said shaft between said impellers, said diaphragms having a n extending therefrom into engagement with a pin extending from said casing for preventing rotational displace-A ment of said diaphragms.

'7. In a centrifugal pump, a casing divided through the longitudinal axis thereof, a shaft extending through said casing, a plurality` of diaphragms having tongues formed circumferentially thereof to enter grooves in said casing and having a n extending therefrom into engagement with a pin extending from said casing for preventing lateral and rotational displacement, respectively, of said diaphrag'ms.

8. In a centrifugal pump, a. casing divided through the longitudinal axis, thereof, a shaft extending through said casing, a plurality of impellers mounted on said shaft, and enclosures each comprising volute pieces extending circumferentially about said impellers and diaphragm plates extending at right angles to the axis of said shaft, said enclosures being severally mounted in said casing and severally forming volute passages for receiving the fluid discharged from lthe several said impellers, and interstage diaphragms having tongues formed circumferentially thereof to enter grooves in said casing and fins extending therefrom into engagement with pins extending from said casing for preventing lateral and rotational displacement of said diaphrag'ms, said interstage diaphragms being severally mounted on said shaft between said impellers. v CHARLES L. BABB.

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