US2678606A - Centrifugal pump or compressor - Google Patents

Description

May 18, 1954 R. M. WATSON 5 CENTRIFUGAL PUMP 0R COMPRESSOR Filed March 18, 1950 I 6 Sheets-Sheet 1 RALPH M. WATSON INVENTOR.

midi-1 May 18, 1954 R. M. WATSON CENTRIFUGAL PUMP OR COMPRESSOR 6 Sheets-Sheet 2 Filed March 18, 1950 INVENTOR.

RALPH mwATsoN M ER May 8. 1954 R. M. WATSON 2,678,606

TS O'N VENTOR.

May 18, 1 954 R. M. WATSON 2,678,606

CENTRIFUGAL PUMP OR COMPRESSOR Filed March 18, 1950 r 6 Sheets-Sheet 4 RALPH M.\/\/ATSON INVENTOR.

' May 18, 1954 R. M. WATSON CENTRIFUGAL PUMP 0R COMPRESSOR 6 Sheets-Sheet 5 Filed March 18, 1950 May 18, 1954 R. M. WATSON 2,678,606

CENTRIFUGAL PUMP 0 COMPRESSOR Filed March 18, 1950' 6 Sheets-Sheet 6 IN V EN TOR.

Patented May 18, 1954 UNITED STATES PATENT OFFICE Worthington Corporation,

Delaware a corporation of Application March 18, 1950, Serial No. 150,435

7 Claims.

This invention relates generally to multi-stage centrifugal pumps and compressors for fluids of high or Varying temperature, and especially for liquids of high delivery pressure, possibly in excess of a thousand pounds per square inch, and provides novel means for minimizing longitudinal forces in the casing and its end closure joints, in spite of differential thermal expansion of its members, and also for minimizing leakage at the shaft seals in each end of the casing, while minimizing first cost and promoting easy inspection, repair and replacement of parts.

While this invention will be described and shown in connection with pumps for high temperature liquid such as those for boiler feed in high efiiciency steam power plants, for petroleum products in oil refineries and other liquids in chemical industries, it is not intended to so limit this invention, which may be advantageously applied to multi-stage compressors in which the pressure ratio results in a substantial rise in temperature of discharge gases or vapors during compression.

My invention is preferably applied to those high pressure multi-stage pumps that are of double casing construction, in which there is an outer casing of generally cylindrical form Without longitudinal joints subjected to the delivery pressure of the fluid, and inside of it, an inner casing of horizontal split type enclosing all of the pump impellers, and fluid flow passages between the impellers. Such pumps must have at least one end of the outer casing open, with a bolted closure member to permit insertion and removal of the inner casing assembly, and there must be a connection between these two members that will permit of independent longitudinal expansion and contraction due to changes in the fluid temperature, to minimize longitudinal stresses in the outer casing and limit the load on its end closure member and its fastening, with prevention of leakage of fluid at the delivery pressure. It is recognized that an outer round casing without longitudinal joints, and an inner casing having a longitudinal joint, with the fluid delivery pressure between them, tending to burst the outer casing and to collapse the inner casing, and to tighten its longitudinal joint, are advantageous and in actual use.

However, this construction has developed two main problems. First, since the discharge pressure acts on the end closure of the outer casing, heavy flanges and bolts must be provided to prevent leakage as well as rupture. These heavy flanges and bolts increase the cost of manufacture and create an awkward and heavy structure to handle when repairs are necessary. Second, the sealing structures between the shaft and the outer casing end closure member will be expensive or unsatisfactory if subjected to the delivery pressure that acts on the end closure member.

The present invention in a single embodiment contemplates a construction wherein the delivery pressure, which acts between the inner and outer casing, does not act on an appreciable area of the end closure members of the outer casing, and thereby does not load it, or longitudinally load the outer casing, and at the same time prevents the delivery pressure from acting on the shaft seal in the end closure member, and permits com plete freedom of thermal expansion of one casing relative to the other.

Accordingly, it is an object of the present in vention to provide a double case multi-stage centrifugal pump with the discharge pressure acting inside of the outer, and outside of the inner case, without producing any opposing longitudinal forces in the outer casing, 0r substantially none, or loading its end closure members.

It is another object of the present invention to provide a novel construction of a double case multi-stage centrifugal high pressure pump or compressor wherein the function of the outer casing will be simply that of a cylindrical internal pressure resisting element carrying primarily hoop stress instead of a combined hoop stress and axial stress.

It is another object of the present invention to provide a novel construction of a double case multi-stage high pressure pump with the discharge pressure acting on the inside of the outer cylindrical case, but caused to act on a relatively small axially projected area of the end closure.

It is another object of the present invention to provide a novel construction of a double case multi-stage centrifugal pump with the discharge pressure acting between the two cases, and the suction pressure acting on both shaft stufiing boxes or seals.

It is another object of the present invention to provide a novel construction of a double case multi-stage high pressure pump Or compressor wherein the whole sub-assembly, including impellers, connecting passages and inner casing can be assembled with its bearings and checked for free rotation (before insertion into the outer casing or barrel).

It is another object of the present invention to provide a novel construction of a double case multi-stage centrifugal pump with the discharge pressure acting between the two cases for a longitudinal distance limited to the space between two cylindrical piston lilze extensions on the outside of the inner case contact with a bored internal cylindrical surface on the inside of the outer case.

It is a further object of the present invention to provide at least one or more slip joints between the contacting inner and outer cylindrical surfaces of the inner and outer casings, which permits relative axial thermal expansion, under vari ations in temperatures, between the inner and outer casing also permits easy assembly and disassembly.

With these and other objects in view, as may appear from the accompanying specification, the invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawings, showing a centrifugal pump or compressor of a preferred form embodying the invention, and the features forming the invention will be specifically pointed out in the claims.

In the drawings:

Figures 1A and 13 combined show a longitudinal section through a multi-stage centrifugal pump const noted in accordance with the present invention.

Figure 2 is a cross section through the pump casing taken on the line 22 of Figure 1, looking the direction of the arrows.

igure 3 is a cross section through the pump casing taken on the line 3-3 of Figure 1, looking inthe direction of the arrows.

Figure 4t is a cross section taken on the line 4-4 of Figure 1, looking in the direction of the arrows.

Figure 5 is a longitudinal section through a slightly modified form of the invention.

Figure 6 is a fragmentary longitudinal section through a modified form of the pump embodying packing at the slip joint.

Figure '7 is a fragmentary longitudinal section through a modified form of the pump embodying rings at the slip joint or joints.

Figure 8 and Figure 13 combined show a longitudinal section through a modified form of the invention.

Referring more particularly to the drawings. Figures 1A 13 combined. show a preferred form of the improved multi-stage centrifugal pump comprising an outer casing l which is preferably of the barrel type, that it is a cylindrical casing open at one end to receive the inner casing 2 of the ump and being without any longitudinal joint. It being understood that while this type of construction is called the preferred form, it is not intended to so limit the invention as the outer casing may be constructed with both ends open as is shown in the modified form of Figures 8 and 13 combined.

Thus. in the preferred form, outer casing is open at the discharge end of the pump so that the inner casin 2 carrying the various impellers 3, and i l and having various flow passages t formed therein may be inserted longitudinally into the outer casing l with the suction eye 5 of the first stage impeller 5 opening into the suction passage 1 formed in the end of the outer casing. A suitable sealing structure 8 for the impeller shaft 9 is carried by the outer casing l at the inlet end of the pump and a corresponding sealing structure I!) is detachably carried by the inner casing 2 at the discharge end of the pump. It is to be understood, of course, that bearings for the shaft 9 are provided beyond the sealings 8 and ill, but such bearings may be of any approved construction and are not shown in the present drawings.

The inner casing 2 is split longitudinally as is clearly shown in Figures 2, 3 and 4 of the drawings and its two sections H and i2 are connected final stage impeller It di charges through the discharge outlet of the inner casing 2 into and through the outlet [5' of the outer casing i, across a gap or open space H, in communication with the annular space is between the inner and outer casings. V

In the preferred form of the invention the inner casing 2 has one or more diametral enlargements l9 and 23 substantially piston-like in construction and disposed, so that there will be at least one of said pistondike members at each end of the inner casing 2. Thus the discharge outlets 15, and iii and the space or gap ll will be dis.- posed between the. piston-like enlargements l9 and 2G and the suction inlet 3' will be disposed outwardly thereof. so that the suction inlet 1 and the discharge outlets i5 and it will bev separated by at least one of said piston-like members, all of which is clearly shown in Figures 1A and 1B of the drawings.

The piston-like. enlargements l5 and 2B are machined to make a sliding fit with corresponding inner circumferential bores 2i and 22, formed in the bored interior'of the outer casing l. The bores 25: and 22 may be of equal diameters with respect to each other but of lesser diameter than the inner circumference of the outer casing I. However, in the preferred form, bore 22 at the open end of the outer casing will have a little larger diameter than bore 2 l to facilitate the insertion and removal of the inner casing as. a single self contained unit.

In addition, if the bores 22! and 22 are of equal diameters the delivery fluid acting between the piston members :9 and 2!! by reason of the gap i! cannot produce a longitudinal thrust in either direction. However, where the diameter of the bore 22 and correspondingly the piston 26 are of slightly larger diameter, there is a thrust force toward the open end of the outer casing as small as may be desired.

This unbalanced longitudinal end thrust may accordingly be adjusted to a predetermined limited magnitude whereby it will require only a relatively light flange and stud bolt to resist it. Figure 1B shows a relatively light flange 23 formed on the piston 29 which is substantially annular in shape and is adapted to engage studs 2 on the open end of the outer casing and to be held thereto by means of nuts 25, thus closing the outer casing both axially and longitudinally and providing means for fixing the inner casing and its sub-assembly parts at only one end. This allows the inner casing and its subassembly to be free to expand and contract longitudinally within the outer casing by the sliding of the piston l9 in the bore 2! formed in the outer casing between the suction inlet l and the discharge outlets I5 and I6 thereof, thus forming a relatively simple slip joint, all of which is clearly shown in Figures 1A and 1B of the drawings.

The finished outer surface of the piston l9 may be provided with pressure reducing grooves ,26 to reduce the fluid leakage from the annular s'pace'lB between the inner and outer casings which receives discharge fluid pressure therein by reason of gap H, to the suction I, it being understood that other suitable means may be utilized such as packing rings, rings or soft packing as is shown at 26a in Figure 6 and 26b in Figure 7 of the drawings.

This slip joint between the inner and outer casings is made possible, practical, and commercially acceptable, due to the recognition by the power and process industries that stainless steels around the waterways or liquid passages are preferable with present day boiler feedwaters and process industry liquids. Such stainless steels or materials are exceedingly resistant to corrosion and. erosion, and as the inner casing is made of stainless material, any slight leakage developing at the slip joint between the high pressure and low pressure side would have a very low rate of erosion and the life of the pump will accordingly be acceptable, and accumulation of corrosion products that might resist sliding is unlikely.

To prevent action of the discharge pressure on it, and to alternatively subject the packing structure iii to the lowest unit pressures in the interest of good operation, and also to aid the balance of the axial thrust on the rotating element, the inner casing 2 is provided with a chamber 21 at its discharge end outwardly of the piston 25). The chamber 21 has communication with the suction i through a plurality of internal conduits or pipes 23 which, as shown in Figures 1A and 13, extend longitudinally of the pump structure and have no communication with the fluid flow through the normal flow passages 4 of the pump excepting only the suction I, but it is understood that while this type of communication is shown that other means such as external conduits may be utilized for this purpose.

In some instances of multi-stage centrifugal pump construction, it may be desirable either to add outlets to remove fluid at a pressure low-- or than final discharge pressure of the pump, or to add inlets to introduce fluid into the pump from some source in the system in which the pump is employed where the pressure of the introduced fluid is in excess of the suction pressure. In either of such events, additional piston-like enlargements are formed on the inner casing to fit another outer casing bore to make a second slip joint and a second pressure chamher as more fully shown and described in my copending application, Serial No. 383,877, filed October 2, 1953.

Figure of the drawings shows a slight modification in the pump structure wherein the first stage of the multi-stage centrifugal pump is a double suction impeller 46, the suction eyes 41 at each. side of which receive the incoming liquid from the branches d2 of the inlet passage 43 formed in the inner casing 44. The inlet passage 53 in the inner casing 44 communicates with the inlet passage it in the outer casing 45 of the pump. An annular space 41 is provided between the outer casing 46 and the inner casing 44 and has communication with the discharge 48 of the inner casing to receive fluid under discharge pressure of the pump and a piston-bore slip joint construction 49 is provided between the outer casing 46 and the inner casing 44; The slip joint construction is identical in constructicn with the slip joint shown in Figure 1A of the drawings, and it will permit relative longitudinal movement of the outer and inner. casing on expansion or contraction thereof and will also provide a normal seal between the two casings. The inner casing 44 has a chamber 50 therein at its discharge end which has communication through suitable pipes or conduits 5| with the suction 43 so that the surface surrounding the chamber 56 will be subjected to suction pressures of the pump. Like the pump shown in Figures 1A and 1B, the inner casing M has a relatively light connection flange 52 at its discharge end which is connected with relatively light bolts 53 to its outer case 48. Such a construction is permitted due to the approximate counter-balancing of the forces whereby the net axial forces acting perpendicular to the longi tudinal axis will be relatively small as above described.

Figure 8 and Figure 13 combined show the modified form of the invention which permits complete external assembly of a complete operable pump carrying its own bearings by mere insertion of it in the outer casing and bolting up to be ready to function as a complete pump. This arrangement demonstrates clearly the versatility of this piston and bored cylinder construction for assembly and disassembly with a minimum amount of effort and allows for the complete re moval of one unit and replacement thereof by a completely new unit without the necessity of completely disassembling the entire pump structure.

The modified form changes in particular the suction side of the pump as is shown in Figure 8 of the drawings. This outer casing I is a substantially cylindrically-shaped casing open at either end to receive therein the inner casing 2' of the pump.

The outer casing I is now provided with a suction inlet 3 and discharge outlet shown in Figure 113 instead of a suction passage 1 as is shown in Figure 1A. It being understood that the suction inlet and discharge outlet may be varied in their respective positions to suit the particular design as is immediately evident to one skilled in the art.

Inner casing 2' is constructed so that is is complete in itself as it carries a suction passage 4' which communicates with the suction eye 5 of the first stage impeller 6 which discharges into the various flow passages 1' formed therein. Formed outwardly of the suction passage 4 is the sealing structure 8 for the impeller shaft 9 and a bearing support member [0 to carry the bearings (not shown) which support the impeller shaft 9' outwardly of the sealing'struc ture.

Thus, the inner casing 22 may be inserted longitudinally into the outer casing I with all of its assembled operative parts, so that the suction inlet 3 will communicate with the suction passage 4 to form a complete pump unit which is easily renewable by mere replacement of a new internal unit-completely assembled.

The inner casing is further provided with annular pistons ii and I2 on either side of the suction passage 4 which slidably engage cylindrical bored surfaces It formed in the o utercasing thus forming slip joints as is clearly shown in Figure 8 of the drawings. The pistons It and I2 and the cylindrical surfaces 83 forming the slip joints are substantially identical in construction with pistons [9 shown in Figure 1A of the drawings, above described. To efiect better sealing against fluid leakage, however, 0 rings it have beenadded. It being understood that ac'zaooc other types of packing structures may be utilized as, for example, that shown in Figure. 6 of the drawings.

By providing the piston-cylinder. slip joint between the outer barrel without longitudinal joints and the inner axially split casing of the pump, it is not necessary to provide. a complicated seal construction to prevent damage to the pump under fluid temperature changes in service, and the discharge end flange of the outer casing in the present pump does not need to be made sufficiently heavy to carry the force resulting from the discharge pressure of the pump against the full area of the discharge end closure member as above described.

It'will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown, but that these may be widely modified within the invention defined by the claims.

What is claimed is:

1. In a multi-stage centrifugal pump or the he, a hollow cylindrical outer casing, an inner casing including a plurality of pumping stages having flow passages and impellers, said casing provided with communicating inlet and communicating discharge outlets, said outer casing bored internally to provide finished bores on the inner surface thereof disposed on either side of said discharge outlets, said inner casing having diametral enlargements thereon corresponding to said. finished bores and mounted for sliding contact with said bores to form at least one slip joint for expansion and. contraction of said inner casing with respect to said outer casing, at least one of said diametral enlargements formed on the end of said inner casing outward- 1y of said discharge outlets and provided with means thereon for connecting said casing, at one end, a chamber formedbetween said casings when said casings are disposed to form said slip joint, said chamber located between said discharge outlets and at least one of said slip joints and open to receive fluid at discharge pressure from the discharge-outlet of said. inner casing whereby said slip joint will be responsive to pressure and temperature changes in said fluid being pumped, said inner casing having a second chamber therein at its discharge end formed outwardly of said diametral enlargement having the connecting means thereon, and means formed in said inner casing to establish communication between said second chamber and the inlet openings for said casings.

2. In a multi-stage centrifugal pump or the like as is claimed in claim 1 wherein said means providing communication between said second chamber and said inlet openings for said casings includes, a conduit formed integrally with said inner casing having an opening at one end into said inlets and at the other end into said second chamber.

3. In a multi-stage centrifugal pump, a hollow cylindrical outer casing, an inner casing including a plurality of pumping stages having flow passages and impellers, said casings provided with communicating inlets and communicating discharge outlets, said outer casing having circumferential sealing surfaces on the inner surface thereof disposed on opposite sides of the discharge outlet therein, said inner casing having continuous circumferential enlargements thereon corresponding to said sealing surfaces to form at least one slip joint and at least one seal therewith, said outer casing, inner casing. and circumferential enlargements forming a pressure chamber communicating with said discharge outlets, said slip joint and said seal having substantially equal diameters to present a relatively small net cross-sectional area subject to the full discharge pressure acting between said casing, and means for connecting said inner casing to said outer casing.

4. In a multi-stage centrifugal pump, a hollow cylindrical outer casing, an inner casing including a plurality of pumping stages having flow passages impellers, said casings provided with communicating inlets and communicating discharge outlets, said outer casing having circumferential sealing surfaces on the inner surface thereof disposed on opposite sides of the discharge outlet therein, said inner. casing having continuous circumferential enlargements thereon corresponding to said sealing surfaces to form at least one slip joint and at least one seal therewith, said outer casing, inner casing and circum' ferential enlargements forming a pressure chamber communicating with said discharge outlets, said slip joint and said seal having substantially equal diameters to present a relatively small net cross-sectional area subject to the full discharge pressure acting between said casing, and means continuous with said inner casing for connecting said inner casing to said outer casing.

5. In a multi-stage centrifugal pump as claimed in claim 4 wherein means to reduce leakage is provided on said slip joint between said communicating inlets and said pressure chamber.

6. In a multi-stage centrifugal pump, a hollow cylindrical outer casing having an inlet and a discharge outlet, said outer casing having at least onecircumferential sealing surface on the inner surface thereof disposed between said inlet and said discharge outlet, an inner casing including a plurality of pumping stages having flow passages and impellers and a suction inlet and discharge outlet for said inner casing communicating with said inlet and said discharge outlet of said outer casing, said inner casing having a continuous circumferential enlargement thereon for sliding contact with said circumferential sealing surface to form a slip joint therewith, a second circumferential enlargement on said inner casing for contact with the inner surface of said outer casing on the side of the discharge outlet thereof opposite from said slip joint to form a seal therewith, said outer casing, inner casing and circumferential enlargements forming a pressure chamber communicating with said discharge outlets, said slip joint and said formed seal having substantially equal diameters so that a relatively small. net cross-sectional area will be subject to the full discharge pressure acting between said casings, and means connecting said inner casing to said outer casing.

'7. In a multi-stage centrifugal pump, a hollow cylindrical outer casing having an inlet and a discharge outlet, 5 :id outer casing having at least one circumferential sealing surface on the inner surface thereof disposed between said inlet and said discharge outlet, an inner casing including a plurality of pumping stages having flow passages and impellers and a suction inlet and discharge outlet for said inner casing communicat ing with said inlet and said discharge. outlet of said outer casing, said inner casing having a continuous circumferential enlargement thereon for sliding contact with said circumferential sealing surface to form a slip joint therewith, a second circumferential enlargement on said inner casing for contact with the inner surface of said outer casing on the side of the discharge outlet thereof opposite from said slip joint to form a seal therewith, said outer casing, inner casing and circumferential enlargements forming a pressure chamber communicating with said discharge outlets, said slip joint and said formed seal having substantially equal diameters so that a relatively small net cross-sectional area will be subject to the full discharge pressure acting between 10 said casings, said second circumferential enlargement on said inner casing having means continuous therewith for connecting said inner casing to said outer casing.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Name Date Aisenstein Oct. 15, 1935 Hollander Oct. 20, 1936 Bigelow June 6, 1939 Nelson Apr. 17, 1945 Wislicenus Nov, 4, 1947 FOREIGN PATENTS Country Date Great Britain Nov. 16, 1922 Great Britain Jan. 17, 1939

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