US2825285A - Centrifugal pump with discharge manifold - Google Patents

Description

March 4 1958 c. A. scHr-:LLENS 2,825,285

CENTRIFUGAL PUMP WITH DISCHARGE MANIFOLD Filednec. 2s, 1953 L3 ma,

United States Patent C) CENTRIFUGAL PUMP WITH DISCHARGE MANIFOLD Christopher A. Schellens, Tenants Harbor, Maine; Belton A. Copp, executor of said Christopher A. Schellens, deceased Application December 28, 1953, Serial No. 400,703

2 Claims. (Cl. 10S-103) This invention relates to centrifugal pumps and more particularly to pumps of the kind which are designed to deliver uids at high pressures. Such pumps are usually provided with housings composed of castings which are very heavy in order to withstand t-he high pressures which tend to distort the structure. Heavy castings are diiiicult to make and are expensive owing to the weight of metal required and the high percentage of rejects necessitated by blow-holes and other defects which are liable to occur in such castings.

An object of the present invention is to provide a casing so designed as to obviate the need for the usual heavy castings. My improved casing operates successfully with high pressures although the cast parts are comparatively light and therefore comparatively inexpensive. In my improved design, the overall diameter of the casing is reduced so that the necessary machining of the parts to make them lit together tightly can be done on a smaller and less costly machine, thus effecting a further economy.

In centrifugal pumps of the diffuser type for delivering fluid at high pressure, the fluid leaves the impeller at a comparatively high velocity and passes through diffuser passages having expanding cross-sectional areas with the result that the velocity of the fluid decreases and the pressure increases. In a pump of customary design the fluid passes from the diffuser into a scroll or collecting passage which extends around the circumference of the diffuser with a cross-sectional area which increases to a maximum at a point where the scroll empties into a discharge pipe the area of which is approximately the same as the maximum area of the scroll. The velocity of the fluid entering the pipe is only a small fraction of its velocity when it enters the diffuser. The area of the maximum scroll section and discharge pipe is therefore of substantial magnitude so that large unwieldy castings are necessary. An object of the invention is to avoid the necessity for such castings by providing a multiplicity of discharge passages to take fluid from the collecting passage. lf there are n such passages and the outlets to these discharge passages are uniformly distributed along the collecting passage, the section area of the latter can be l/n times the maximum section area of the scroll without imparting to the Huid a greater velocity than would exist in this scroll section. The discharge passages may be made to empty into a manifold conveniently located to collect the lluid from the discharge passages and conduct it to a single discharge pipe.

It is to be noted that the usual scroll section does not completely surround the liuid passing through it, but is open along a circumferentially disposed slot for receiving the fluid discharged from the impeller. lf the scroll is of large section and the pressure is high there is a pronounced tendency to spread the sides thereof, and the high bending stresses in the metal must be kept within safe limits by providing heavy sidewalls for the scroll. The manifold which l provide is preferably a tube of circular section which completely encloses the uid, and

the walls are therefore subjected substantially only totension stresses, without any tendency to bending. Furthermore in the construction, I employ bent tubes which are made by a drawing or rolling process, where the metal is worked in its solid state with a resulting dense and uniform structure. The wall thickness of the manifold is therefore a small fraction of the Wall thickness of the usual scroll of equal section area, while still providing ample strength. Y

For a more complete understanding of the invention, including various additional advantageous features, reference may be had to the following description thereof, and to the drawing, of which- Figure l is an elevation of an embodiment of the invention viewed as indicated by the line 1--1 of Figure 2;

Figure 2 is a section on the line 2-2 of Figure l;

Figure 3 is a fragmentary section, on a larger scale, on the line 3 3 of Figure 2;

Figure 4 is a fragmentary sectional view of a modified form of the invention; and

Figure 5 is a fragmentary elevational view of a modilied form of manifold.

.are arranged concentric with the axis of the pump.

The drawing shows a centrifugal pump comprising an ing which consists of a cylindrical member 14, a diaphragm 16 and a head 18, with bolts 20 to hold these parts in assembled relation. The shaft 12 extends through the diaphragm 16, the impeller being mounted on the end thereof. The head 18 has a central aperture 22 through which fluid is supplied from a pipe 24 to the inlet 26 of the impeller. Y

A diffuser 30, clamped between the head 18 and the diaphragm 16, surrounds the impeller circumferentially to receive fluid therefrom. The diffuser passages open into a collector passage 32 which in turn communicates with a multiplicity of radial discharge passages 34 through the casing member 14, four such passages being shown by way of example, it being understood that a greater or lesser number may be employed. Each passage opens into a pipe 36 the further end of which is welded to a discharge manifold. To minimize the overall diameter of the manifold, the pipes 36 are elbows the outer ends of which are welded to side walls of arcuate pipes 38 which In the embodiment of the invention illustrated in'Figure 1, two arcuate pipes 38 are shown, the interior cross-sectional area of each pipe being preferably equal to the sum of the areas of the pipes 36 which open into it. Each pipe 38 is blanked off at one end and welded at the other end to a T-tting 40 to which a discharge pipe 42 may be bolted. In order to prevent undue bending stresses inthe elbows 36 resulting from the weight of the manifold 38 and the piping 42 attached thereto, the T-tting 40 is preferably bolted to the casing 14 as at 44. The area of each pipe 38 need not be more than half that of the discharge pipe 42. Furthermore, portions of the manifold may be smaller than that. For example, if four elbows 36 open into the manifold, as in Figure 5, the portions 70 of the manifold which adjoin the T-itting 40 and each of which carries the liquid from two of the elbows 36 have a crosssectional area equal to half that of the discharge pipe 42, but the portions of the manifold which carry the liquid from the lowermost elbows 36 only can have crosssectional areas equal to one quarter of that of the discharge pipe 42. The use of a manifold as described offers an important practical advantage in comparison with centrifugal pumps of ordinary construction in that a smaller machine can be used to do the necessary machining on the casing. In constructing the pump shown on the drawing, the pipe elbows 36 are welded to the casing 14 and the assembly is annealed to remove welding strains. The casing is then machined to provide accurate seating surfaces for the diaphragm 16"and the head 18. The table of a machine for this purpose Vneed have a radius only as long Aas the radius from the `axis of the rotor to the outermost points of the pipe elbows 36, whereas a pump of corresponding size with a casing including a scroll surrounding the impeller would require a machine with a table having a `radius at least as great as the distance from the pump axis to the outermost point of the discharge member at the end of the scroll, such member corresponding to the T-fitting 40.

After the casing 14 with the pipe elbows 36 welded thereto has been annealed, the collecting pipes 38 which have previously been welded to a fitting 40 are welded to the ends of the elbows 36,V the heat of these welds being too far removed from the casting 14 to warp the machined surfaces thereof. It may be noted that since the pipe elbows 36 are uniformly spaced around the circumference of the casing 14, the collecting and discharge manifold consisting of the arcuate pipes 38 and the fitting 40 can be welded to theV elbows 36 with the fitting 40 projecting up (as shown in Figure 1) or down or to either side.

Figure 4 illustrates a pump with an intake manifold resembling the discharge manifold hereinbefore described. The pump casing 50 `'with the diaphragm 52 encloses the impeller and diffuser 30. Pipe elbows 54 are welded at one end to the circumference of the casing 50 and at the other end to arcuate collector pipes 56.` The latter open into a discharge fitting 58. A head member 60 is bolted to the forward edge of the casing member 50 to `enclose an inlet chamber 62.` Welded to the casing member 50 and opening into the chamber 62 are pipe elbows 64 the other ends of which are welded to arcuate pipes 66 which communicate with a fitting 68, the pipes 66 and fitting 68 constituting an inlet manifold. This results in an arrangement of inlet and outlet manifolds which may be helpful inconnecting the pump to supply and discharge pipes.

I claim:

1. A high pressure centrifugalpump having a casing, an impeller rotatably mounted therein, a diffuser having a series of fixed diffuser blades supported by said casing in a circular series adjacent tothe circumference of said impeller, said casing providing a collecting passage surrounding the circumference of said diffuser, an arcuate tubular discharge manifold outside of said casing, said manifold extending around approximately three quarters of the circumference of said casing, a discharge pipe communicating with said manifold at its mid point, the crosssectional area. of said pipe being approximately twice that of the manifold, and four ducts leading from said collecting passage to said manifold, said ducts being uniformly spaced apart, the crosssectional area of each said duct being approximately half that of the manifold.

2. A high pressure centrifugal pump having a casing, an impeller rotatably mounted therein, a diffuser having a series of fixed blades supported by said casing in a circular series adjacent to the circumference of said impeller, said casing providing a collecting passage surrounding the circumference of said diffuser, and a tubular discharge manifold separate from said casing and exposed to atmospheric` pressure, said discharge manifold communicating with said collecting passage only at a plurality of points uniformly spaced along the length of said passage and having inlet orifices of uniform size connecting it with said collecting passage at said spaced points, said discharge manifold including a plurality of arcuate pipes, and elbows, each elbow having one end welded to said casing at a circumferential point thereof and communicating with said collecting passage, said arcuate pipes around the periphery of said casing communicating with the other end of said elbows, and a T-fitting to which an end of each said arcuate pipes is welded.

References Cited in the file of this patent UNITED STATES PATENTS 347,227 Campbell Aug. l0, 1886 786,384 Richards Apr. 4, 1905 1,947,477 Lysholm Feb. 20, 1934 2,228,194 Birkigt Jan. 7, 1941 2,494,821 Lombard Jan. 17, 1950 2,631,815 Holzworth Mar. 17, 1953 2,672,013 Lundquist Mar. 16, 1954

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