US2677328A - Centrifugal pump for high temperature liquids - Google Patents

Description

y 4, 1954 E. F. VITEK 2,677,328

CENTRIFUGAL PUMP FOR HIGH TEMPERATURE LIQUIDS Filed Dec. 30, 1949 3 Sheets-Sheet 1 F@./.

Inventor:

by Z M His Attorney Edwahd F. ViteK,

May 4, 1954 E. F. VITEK CENTRIFUGAL pum FOR HIGH TEMPERATURE LIQUIDS 3 Sheets-Sheet 2 Filed Dec. 30, 1 949 Inventor: Edward F. Vite by His Attorney.

May 4, 1954. E. F. VITEK 2,677,328

CENTRIFUGAL PUMP FOR HIGH TEMPERATURE LIQUIDS Filed Dec. 50. 1949 Fig.3.

3 Sheets-Sheet 3 Inventor: Edward FiVitek,

by 4f M His Attovney Patented May 4, 1954 CENTRIFUGAL PUMP FOR HIGH TEMPERATURE LIQUIDS Edward F. Vitek, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 30, 1949, Serial No. 135,997

2 Claims. 1

This invention relates to a centrifugal pump especially adapted for handling unstable, corrosive, or otherwise dangerous liquids at extremely high temperatures, on the Order of 800 F.

The object of the invention is to provide an improved centrifugal pump of the type described which is fully protected against leakage of the liquid being pumped yet at the same time is so arranged as to facilitate access to the pump casing and impeller for inspection and servicing.

Another object is to provide an improved high temperature pump construction having a novel combination of sealing and cooling means for pre venting leakage of the liquid being pumped at the place where the pump shaft projects through the casing, while at the same time reducing the transfer of heat along the pump shaft and safely dissipating what heat is conducted therealong.

Other objects and advantages will be apparent from the following description taken in connection with the accompanying drawings, in which Fig. 1 is a vertical sectional view of the complete pump assembly; Fig. 2 is a top view of the pump assembly of Fig. 1; Fig. 3 is an enlarged sectional view of the shaft sealing and cooling assembly;

and Fig. 4 is a plan view of a shaft seal and packing assembly taken on the plane 4-4 in Fig. 3.

Referring now more particularly to Fig. 1, this improved pump assembly consists of a motor indicated generally at l bolted to the top of a motor stand 2, the bottom end of which is secured by bolts to a "floor plate 3, which forms the main frame member of the assembly. The shaft of motor I is secured by a suitable flexible coupling i to a pump impeller shaft 5 carried in; a pair of suitable axially spaced anti-friction bearings shown generally at 6, 'l. The structural details of the coupling 4 and bearings t, i are not material to an understanding of the present invention and are therefore not described more particularly hereinafter. Associated with the central opening in the floor plate 3 through which the shaft 5 projects, is a packing and cooling assembly indicated generally at 8, the details of which will be described more particularly hereinafter in connection with Fig. 3.

The frame and housing assembly of the centrifugal pump proper consists of three main components. Secured to the under side of the floor plate 3 by a circumferential row of studs 9 is'a pump frame member 10, which is cylindrical in shape with a lower end portion defining a circumferential flange II to which the discharge scroll casing i2 is secured by a plurality of circumferentially spaced studs 8. Projecting radially 2 inward from the flange II is a wall or web portion [4 carrying a central cylindrical portion 15, which forms the housing for a shaft cooling arrangement described more particularly hereinafter.

Secured to the bottom of the discharge scroll l2 by a circumferential row of threaded fastenings i6 is the pump intake casing indicated generally at I1 as being an elbow-shaped pipe having at the pump end a flange [8 forming a closure for the bottom of the pump casing, and having at the other end an intake conduit flange lg to which is bolted the intake pipe 20. As will be apparent from Fig. 1, suction pipe 20 turns upwardly and projects through an opening 2| in the floor plate. This opening is substantially larger in diameter than the suction pipe 20, the intervening annular space being closed by a flexible joint 22 comprising an annular member Eta of U-shaped cross-section welded at its outer edge to the circumference of the opening 2i in the door plate, the inner circumference being welded to a collar 22b which is in turn welded to the outside of the pipe 20. This flexible joint is provided so that differential thermal expansion between the conduits, pump casing, and floor plate, may be accompanied by transverse shifting of the conduit 20 within the opening 2! without imposing unduestresses on any of the components.

As will be obvious from Fig. 1, the conventional centrifugal impeller 23 is secured by impeller nut 24 to the reduced end portion of shaft 5. The discharge scroll l2 terminates at a discharge flange 25a,- to which is secured by bolts 25 a flanged discharge elbow 2t. Conduit 26 likewise projects upwardly through an opening in the floor plate 3 and is sealed thereto by an annular flexible member similar to the ring 22a. The relation of the suction and discharge pipes may be seen more clearly from the top view of Fig. 2,

the flexible sealing ring for the discharge'pipe being indicated at 21. r p

Since in handling dangerous liquids of the type for which the present pump was designed it is necessary to be able to completely drain the whole system, special valved drain conduits are provided for the intake and discharge pipes. The lowermost portion of the U-shaped bend'in the intake pipe is provided with a drain tube 21 with a valve shownin dotted lines at 28. Similarly, the lowermost part of the discharge conduit 28 is provided with a drain tube 29 having a suitablevalve 30. Asmay be seen in Fig; 2, the drain conduits 21,29 simply discharge into the enclosing casing 3 l .j as may bes'ee'n in Fig. 1, this outer 3 tank 3| is imperforate except for a single drain port communicating with conduit 32, which may deliver to a suitable closed storage tank shown diagrammatically at 320..

In order that the drain valves 28, may be operated from outside the enclosure defined by the floor plate 3 and tank 3|, suitable operating extensions are provided for the hand wheels of the valves. One such extension is shown diagrammatically in Fig. 1 in the form Of an actuating rod having at the lower end thereof a yoke 36 adapted to engage the spokes of the hand wheel 30a. The upper end of rod 35 passes through a suitable stuffing box 31 and carries an actuating hand wheel 38.

It will be seen in Fig. 1 that the cylindrical casing 3| is provided with a bolting flange 33 by which it is tightly secured to the bottom surface of the floor plate 3 with a suitable fluid sealing gasket 34 between. Thus it will be ap-' parent that any leakage from the pump casing, for instance through the gaskets Ha, |2a at either side of the discharge scroll l2, or past the gaskets at the flanged suction joint I9, or the intentional leakage of cooling fluid described hereinafter, will all be collected in the bottom of tank 3| and drained through conduit 32. It will also be observed that this arrangement of the pump permits the suction and discharge conduits 20, 26 to be securely welded at the exterior side of floor plate 3 into the piping system with which the pump is associated. Thus the system for circulating a potentially dangerous liquid may be almost completely sealed by welded joints, all the bolted flanged joints with gaskets being located within the leakage collecting tank 3|. At the same time, access to the pump is made possible simply by removing the tank 3|, unbolting the intake flange |9 and removing the inlet elbow H by removing the bolts Hi. This gives free access to the impeller 23, which may be removed from the discharge scroll |2 simply by removing nut 24.

In order to prevent contamination of the liquid by oxides or other decomposition products resulting from contact with the air, the tank 3| is pressurized with a suitable inert gas, as illustrated diagrammatically by a storage bottle 3|a from which an inert gas such as nitrogen is supplied by conduit 3|b having a pressure regulating valve 3|c adapted to maintain the gas pressure within the tank 3| at about 5 to 15 pounds per square inch, gage. This insures that there will be no infiltration of air from the leakage path which might exist through the gasket 34, etc.

Because of the dangerous nature of the liquids to be pumped, and the fact that they are at an extremely high temperature, it is necessary to make absolutely sure that there is no leakage from the pump enclosure, and that the transfer of heat from the hot liquid along the shaft to the bearings is prevented, since anti-friction bearings cannot operate over long periods at temperatures much in excess of 300 F. The various means for preventing this transfer of heat and eliminating the possibility of leakage are as follows.

In order to prevent the transfer of heat by radiation from the pump casing to the floor plate 3, a plurality of spaced radiation shields are provided, in the form of annular plates 39 .secured by machine screws 40 to the floor plate 3 with suitable washers between so that there ambient atmosphere through any.

4 is an air space between the respective radiation shields and between the shields and the floor plate. These shield plates are preferably highly polished on both sides in order to resist the transfer of heat by radiation. As may be better seen in Fig. 3, a similar radiation shield assembly is secured to the floor plate 3 within the cylindrical member I0. This inner shield assembly is indicated generally at 4|. This radiation shield arrangement is found to be so effective that the floor plate may be left without heat insulation on the exposed top surface thereof, for convenience of access for inspection of the various valves, packing assemblies, flexible joints, etc. associated with the floor plate.

The first barrier to the conduction of heat along the impeller shaft 5 is in the form of a cooling coil contained within the cylindrical member I5 and having helical cooling passages 42a machined in the bore of a cylindrical bushing 42. At its lower end, bushing 42 is provided with an annular lip 43 defining a close clearance 43a with the shaft. Similarly at its upper end, the bushing 42 is provided with a lip 44 forming a close clearance 44a. These clearances are made as small as practicable, consistent with the necessity for preventing mechanical interference with the shaft. This is a difficult problem since, with a single outlet impeller of this type, the hydraulic forces on the impeller deflect the shaft sideways, with the result that the clearances 43a, 44a must be on the order of .012 inch with a shaft diameter of 2% inches. The coolant used is a portion of the liquid being pumped taken from the discharge conduit, as for instance by the conduit 45, whence it passes through a suitable air-cooled heat exchanger indicated diagrammatically at 46, from which the cooled liquid passes through a conduit 41. Conduit 41 is coupled by a pipe union 48 with another conduit 49 welded into a flange at the top of cylindrical member |5. Conduit 49 communicates by way of port 50 with the upper end of the helical cooling passage 42a.

It will be obvious that the comparatively cool liquid in cooling passage 42a readily extracts any heat which may be conducted along the shaft. Spent coolant is discharged through the clearance 43a into the annular chamber 5| defined between the lower end of cylindrical member i5 and the adjacent surface of impeller 23. This coolant fluid may readily pass through the pressure balancing holes 23a in the impeller into the fluid pumping passages thereof. It will be obvious that some cooling fluid also escapes upwardly through the clearance 44a. To prevent this liquid creeping up the shaft toward the sealing means described hereinafter, a centrifugal slinger disk 52 is threaded or otherwise secured to the shaft. It will be apparent that any leakage fluid passing through the clearance 440. will be thrown radially outward in the manner indicated by the arrow 53 in Fig. 1. This liquid will run down the inside of the cylinder Ill and drain through one or more ports 54. As indicated above, this spent coolant fluid is collected in the bottom of the tank 3| and removed through the drain line 32.

Surrounding the shaft immediately above the cooling coil, is a complex sealing and cooling assembly 8, the details of which may be seen by reference to Fig. 3.

As shown in the enlarged section of Fig. 3, the central opening in the floor plate is closed by an annularplate member 55, whichis actually fabricated in two portions, the lower one a having a circumferential portion adapted to be secured between the floor plate 3 and the bolting flange of housing portion Ill by the threaded fastenings 9. It will be apparent that the multiple radiation shields 4| are secured to this lower plate member 55a. Welded to the lower plate 55a is an upper plate member 55b having an annular recess 56 machined in its lower surface. This cooperates with plate 550. to form coolant passages, to which cooling fluid is admitted through an inlet conduit 51 and exhausted through conduit 58. The function of this cooling channel is of course to make doubly surethat heat from the pump assembly will not be transferred by radiation and conduction throughthe comparatively heavy sections of the housing to the housing portion enclosing the shaft seal assembly.

The plate member 5517 has an upwardly extending flanged cylindrical portion 550 defining a stepped internal bore 59 closed by a top plate 60 secured in place by a plurality of circumferentially spaced threaded fastenings 61. A suitable high temperature gasket 62 is located in an annular recess in plate ti! and clamped against the upper surface of the end flange of member 55c by the threaded fastenings 6i.

Carried on shaft '5', and secured thereto by means of a threaded portion 5a with a lock. washer 5b is a sealing sleeve member 63 having a central annular recess in which is located a resilient ring '65 for preventing leakage through the threaded joint, and a depending cylindrical skirt portion 65 of an inside diameter such as to be spaced a substantial distance radially from the surface of the shaft. Into this space projects cylindrical shield member 66' welded at its lower end to the circumference of the central shaft opening in plate member 55b. The shield 66 cooperates with the bore portion 59a to define an annular drain chamber 51 communicating by way of a port 68 with a drain conduit 69 having a valve "i5. Threadedly secured to the extreme lower end of skirt portion Eli is a nut H which engages a spacer ring 12, which in turn retains a rotating seal ring '23 in place against a shoulder 14. Both the upper and lower annular surfaces of seal ring '13 are carefully finished, as by a suitable lapping process, to have extremely smooth and perfectly flat surfaces. Cooperating with these fiat sealing surfaces on the rotating ring 13 are an upper and a lower sealing assembly. These are indicated generally at 15, Hi and the precise mechanical details of these seal assemblies are not material to an understanding of the present invention. However, for purposes of illustration, the lower assembly 'l-Sis represented diagrammatically as consisting of an inner cylinder ll having an upper flanged end portion '58 arranged in telescopic relation with an outer sleeve member it. Sleeve 19 has an'inwardly extending flange E-G defining an upper and" lower annular chamber between the sleeves ll, 19. The'upper chamber houses one or more spring members, indicated as being a coil spring 81, which is arranged to bias the inner sleeve "upwardly relative to the outer sleeve 19. The lower chamber,- below the flange 89, houses suitable fluid sealing members, indicateddiagrammatically as being a pair of resilient rings 82, which are'of course made of a suitable temperature resisting material and are of such a size and shapeas'to be compressed somewhat so as to be in good fluid" sealing engagement with both inner and" outer sleeves. The flanged end portion it of theinner' sleeve defines an annular recess in which islocateda carbon packing ring 83 biased upwardly by spring 8| into sealing engagement with the lower lapped surface of the rotating sealing ring 13. Thus it will be apparent that resilient rings 82 prevent fluid leakage between inner sleeve 1! and adjacent stationary members, while'the' rubbing ring 83' prevents leakage between sleeve ll and the adjacent ring 13. Friction between the sealing rings 82' and the sleeves H, Hlmay be relied on to prevent the inner sleeve H and the" stationary packing ring 83 from rotating, or any'suitable' interlocking or key arrangement (not shown) between rings 11, 19 may be provided. The upper seal assembly may be similar in construction and has a carbon ring, the projecting end portion of which is shown' at 125a, contacting the up per lapped surface of the rotating ring l3.

The flanged housing portion 550, the topclosure plate 60, the rotating ring 13, and the two seal assemblies 15, 16 define a closed annular space 8 to which a suitable cooling, sealing, and lubricating oil is supplied byway of an inlet conduit 85. This oil serves not only to lubricate the rubbing surfaces of seal ring 13, but is supplied in such quantity as to give an appreciable cooling action. The principal portion of this cooling oil leaves-through an exit conduit 85a, but some finds its way between the respective carbon packing rings 15a, 83 so as tolubricate'their rubbing engagement with the rotating ring 13'. That oil which leaks past the upper ring 75a escapes through the annular clearance space between seal assembly 75 and the member 63 and flows radially outward overthe upper surface of top plate 60 and drops into the annular space de' fined between the flange 55c and the lower end portion of the motor stand 2. This leakage may be permitted to drain away through one or more holes or grooves 86 formed in the lower end face of the mounting flange of motor stand 2.

The lubricating oil which leaksbetween the rubbing surfaces of ring 13 and the lower carbon ring 83 drains downwardly through the an-- nular space between the inner sealed ring Ti and the nut H and collects in the drain space 61. Periodically, this leakage can be blown out of the space 61 by opening the drain valve it, whereupon the pressure of the inert gas maintained within the pump tank will cause the leakage oil in space- 6!- to be evacuated through conduit 69. This arrangement insures that no oil can enterthe' pump tank 3|.

Located immediately above the sealing assembly is an additional heat dissipating member in the form of a centrifugal impeller 86: This may be pressed, keyed, or'otherwise secured to shaft 5 and defines a plurality-of radially extending air pumping passages 81 having down wardly opening inlet' portions 88. The upper portion of impeller 85' defines a circumferential portion 89 extending radially beyond the discharge" portion 'ofth'e pumping passages" 81' and having'an outwardly and downwardly" extending sharp-edged circumference 96, the function of which will be seen hereinafter. It will be apparent'from' Fig.- 3, that the action of impeller 86 is to'draw cooling air in as indicated by arrow 9i and discharge it forcefully past the sharp edge 90, as indicated by arrow 92. Any lubricating oil leaking downwardly from the bearing assembly I will run radially outward along the curved upper surface of impeller 8Buntil it reachesthe sharp-dischargeedge 90-. At this point, centrif ugal' force will throw it off the impeller; and thablast' of air '92 will-carry away the oil parti- 7 cles so they cannot land on the upper surface of plate 60.

The primary function of the circulating air 9|, 92 is to further extract any heat passing by conduction along the shaft 5, but, as indicated above, it also serves the function of carrying away oil leaking down from the bearing assembly 1. Oil thrown from the sharp discharge edge 90 of impeller 86 will drain down the irmer surfaces of the motor stand 2 and leave through the slots 86.

It will be apparent from the above description of the structure that the flow of heat from the pump housing upwardly into the seal and bearing assemblies is resisted first by the radiation shields 39, 4|, then by the coolant liquid in the chamber 56, some of the heat which passes these barriers being extracted in the lubricating oil leaking past the sealing ring I3, and a last increment of heat being extracted by the air-cooled impeller 86. These expedients cooperate to insure that a comparatively small amount of heat reaches the shaft sealing assemblies, and that an even smaller amount of heat will reach the lower bearing assembly 1. Thus, both the seal and bearings are permitted to operate at temperatures well within their safe operating range.

In operation, cooling and lubricating oil is supplied to the port 85 at a pressure on the order of 2 pounds per square inch less than the gas pressure maintained within tank 3!. This is to prevent excessive leakage of oil into tank 3! in the event of seal failure. Also cooling fluid is circulated at an appropriate rate to the inlet conduit 51. Then when the pump impeller shaft rotates, cooled liquid at substantially pump discharge pressure circulates through the bleed line 45 and heat exchanger 46 to the shaft cooling coil 42a, while the centrifugal air impeller 86 removes whatever increment of heat may travel along the shaft before it can reach the lower bearing 1. All leakage of the hazardous liquid being pumped is collected within the tank 3! and returned to the closed storage tank 3211, from which it may be drawn off at intervals, purified if necessary, and returned to the pumping circuit. The inert pressurizing gas from the reservoir 3|a prevents in-leakage of air from the ambient atmosphere and provides the pressure for periodically blowing out the oil collecting in the annular passage 61', by actuation of the hand valve 10.

With the construction described, the extremely complex cooling and shaft seal assemblies just above the floor plate 3 are in the open and readily accessible for inspection and servicing. The plate 60 is conveniently made in two or more segments so that by removing threaded. fastenings 6! the plate 66 may be removed for access to the upper seal assembly 15. When it becomes necessary to inspect or service the pump impeller, casing, or shaft cooling coil, the tank 3| is readi 1y removed for access to the flanged joints securing the inlet elbow I! to the inlet pipe and pump discharge scroll respectively.

Thus it will be seen that the invention provides a novel pump construction particularly adapted to be incorporated in a sealed system handling a dangerous. liquid, the escape of which must be absolutely prevented, while at the same time preventing excessive heat from the liquid reaching the shaft seal and bearing assembles.

While only one specific embodiment of the invention has been described herein, it will be obvious to those skilled in the art that many modifications may be made, and mechanical equivalents substituted for the components disclosed herein, and it is desired to cover by the appended claims all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A centrifugal pump comprising bearing means supporting a vertically disposed shaft having an impeller at the extreme lower end thereof in overhung relation to the bearing and axially spaced therefrom, a floor plate member disposed in a plane normal to the shaft between impeller and bearing and having a central opening through which the shaft projects, shaft seal means surrounding the shaft and closing the radial clearance space between shaft and plate, a substantially cylindrical pump frame member having an upper open end portion with a radially extending bolting flange secured to the impeller side of the floor plate, an impeller discharge scroll member secured to the lower end of the pump frame member and surrounding the impeller, the inner' diameter of the scroll being greater than the tip diameter of the impeller, a pump intake casing member comprising an annular disk member forming the inlet side of the impeller chamber and secured at its circumference to the discharge scroll, the intake casing also having an elbow conduit connected to the annular disk member with a bolting flange at the end remote from the impeller, said last-mentioned flange being disposed parallel to the axis of the impeller and spaced transversely therefrom, an intake pipe having at the lower end thereof an elbow portion with a bolting flange adapted to be secured to the intake casing flange, the other end portion of the intake pipe extending vertically through an opening in the floor plate with substantial radial clearance therebetween, flexible sealing means disposed in said last-mentioned clearance space and secured to floor plate and pipe whereby differential thermal expansion between pipe and casing may take place relative to the floor plate without imposing excessive bending stresses on the pipe, a. discharge pipe member having at the lower end thereof a bolting flange secured to the discharge flange of the pump scroll, the other end of the discharge pipe extending vertically upward through an opening in the floor plate with substantial radial clearance and having flexible annular sealing means for permitting differential thermal expansion between pipe and floor plate, and an open-topped tank surrounding the pump casing and associated conduits, the upper portion of the tank defining a flange secured to the floor plate and the lower portion of the tank defining a sump for collecting any leakage fluid draining from the pump casing and conduits.

2. In a machine having a sealed housing with means for maintaining a super-ambient pressure within the housing and a vertically disposed rotatable shaft projecting through an opening in one wall thereof, the combination of a shaft seal assembly comprising a cylindrical wall portion having at the lower end thereof a radially extending wall with a circumferental portion adapted to be secured to a wall of the machine housing, the upper cylindrical portion of the shaft seal housing being radially spaced from the shaft to define an annular chamber, axially spaced upper and lower shaft seal ring assem blies disposed in said annular chamber and having at the adjacent sides thereof parallel opposed carbon packing rings, a sealing sleeve member having an upper end portion secured to the shaft and a lower cylindrical skirt portion defining an annular clearance space with the shaft and extending downwardly below the lower seal ring, a cylindrical shield member having a lower end portion secured to the inner circumference of said radially extending wall, the shield member extending upwardly in telescopic relation Within said skirt and being radially spaced therefrom and from the shaft, the shield member cooperating with the shaft seal housing to define an annular drain chamber into which projects the lower end portion of the sealing sleeve skirt, a rotating seal ring member secured to the sealing sleeve and having parallel upper and lower radially extending surfaces engaged by the respective carbon rings of the seal ring assemblies, means for supplying cooling and lubricating oil to the annular chamber between the seal ring assemblies, drain conduit means communicating with said annular chamber whereby oil may be circulated for removing a substantial amount of heat from the shaft and seal assemblies, the annular drain chamber defined by the cylindrical shield serving to collect the oil which passes the lower carbon ring, drain conduit means communicating with the lowermost portion of said annular drain chamber and having valve means for removing oil therefrom by the action of the gas pressure within the pump enclosure tank, which pressure is communicated through the clearance spaces between the shaft and the cooperating shield and skirt portions of the seal assembly.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,876,520 Newkirk et a1 Sept. 6, 1932 1,898,278 Weis Feb. 21, 1933 1,910,811 Peterson May 23, 1933 1,999,163 Allen Apr. 23, 1935 2,017,026 Forrest et al Oct. 8, 1935 2,075,895 Harmon Apr. 6, 1937 2,215,449 Alexander et a1. Sept. 24, 1940 2,246,868 Trask June 24, 1941 2,320,708 Yost June 1, 1943 2,461,821 Howard et al Feb. 15, 1949

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