GB2129494A

GB2129494A - Casings for multi-stage centrifugal pumps

Info

Publication number: GB2129494A
Application number: GB08328702A
Authority: GB
Inventors: Detelef Prokasky; Wolfgang Scharffenberger
Original assignee: Klein Schanzlin and Becker AG
Current assignee: Klein Schanzlin and Becker AG
Priority date: 1982-10-30
Filing date: 1983-10-27
Publication date: 1984-05-16
Also published as: FR2535412B1; IT1169860B; FR2535412A1; DE3240259C1; IT8323380A0; GB2129494B; GB8328702D0; JPH04103286U; JPS5999090A

Abstract

A casing member 4 of the pump is cut from a steel sheet and has an interior 18 formed by machining. The member is provided with holes 12 through which tie rods 9 pass to clamp the pump stages between an outlet casing 10 and the member. Bolts 15 secure an inlet casing 7 to the member 4. <IMAGE>

Description

SPECIFICATION An eye for multi-stage centrifugal pump This invention relates to an eye for a multi-stage pump and motor assembly in which the pump part consisting of a series of identical stage casings is held together by external tie rods, the latter being secured to the delivery casing and the eye. Such an assembly is herein referred to as being "of the kind specified".

A known six-stage pump construction of this type having the KSB type designation WKT300, is shown in Figure 1. The pump shown in Figure lisa six-stage vertical condensate pump of tank type construction, in which the eye containing a twindelivery impeller takes the tie rod forces by means of which the next five pump stages are held together.

An inlet port is also flanged on the eye casing.

A similar construction shown in Figure 2 is known from KSB Type sheet No. 1754.21 concerning axialinlet high-pressure centrifugal pumps WK. This construction comprises an inlet casing 102 which takes the tie rod forces by means of which the next pump stages are held together and on which an inlet port is again flanged.

These constructions enable multi-stage motor and pump assemblies to be constructed using the same stage casings and impellers in each case on the prefabricated assembly principle. The casing required in each case for the eye or the inlet casing is the only one that has to be separately devised - an expensive matter - to enable the tie rod forces required for sealing the entire assembly to be taken up and to enable the pump to be adapted to the pipeline system concerned, by means of a separate inlet port.

An object of the invention is to provide an easily manufactured eye for a motor and pump assembly, of the kind specified, said eye being able to take the tie rod forces and also form a fixing point for the pump.

According to one aspect of the invention, there is provided an eye for a multi-stage motor and pump assembly, in which the pump part consisting of a plurality of identical stage casings is held together by external tie rods, the latter being secured to the delivery casing and to the eye, and wherein the eye casing is cut from a steel sheet and its interior which accommodates the part or parts carrying the flow is brought to the desired configuration by machining.

By this means it is possible to make considerable savings in the manufacture of complex flow-carrying casing geometries. The reason for this is that prior art casings for the eyes of multi-stage motor and pump assemblies constructed in the form of cast ings, forgings, stampings or plastics extrusions always require the manufacture of models or special forming tools to enable the casing to be produced.

According to another aspect of the invention, there is provided a multi-stage motor and pump assembly, having an eye and a delivery casing and in which the pump part consisting of a plurality of identical stage casings is held together be external tie rods, the latter being secured to the delivery casing and to the eye, and wherein the eye casing is cut from a steel sheet and its interior which accommodates the part or parts carrying the flow is brought to the desired configuration by machining.

Since the eye casing has to take all the tie-rod forces required for sealing the pump, the known constructions are more strongly dimensioned than would be necessary in view of the fluid forces inside this part of the pump. In embodiments of the invention the eye casing can extremely simply be cut, e.g. by flame cutting, from a steel sheet while the space required for the flow-carrying part can very easily be produced on a production machine.

The impellers used in the other pump stages can also be accommodated in this space. This eye casing takes all the pump tie rod forces and all that is required is for the connecting spigot for the intake line to be very easily secured to this casing.

In one embodiment of the invention, the eye casing has an angular or polygonal outer contour. In this way it is possible for the casing to rest or be secured directly on steel members at the pump site by appropriate length dimensions, e.g. in a rectangular construction. There is then no need for additional members for supporting or bracing the pump. This also allows optimum utilization of the steel sheet used in the manufacture.

In another embodiment of the invention, fixings and/or guides provided on the eye casing are cut out in one operation together with the outer contour. All that is then required is subsequentlyforthe actual support surface of the guide or the fixing to be brought to the required dimensions in one operation in order thus easily to provide a fixing pointforthe pump.

In another embodiment of the invention, the axial length of the casing corresponds to the individual axial lengths of each of the subsequent stage casings. Thus if, for example, space conditions at the site of use of the pump necessitate a large distance between the inlet port and the pump fixing point, the eye casing can be used as a second stage for the pump and conversely the second stage casing can be used as the eye casing. The pressure inside the first stage casing is then so low that only short necked-down bolts or small tie-rods are required to clamp the original second stage casing between the inlet spigot and the offset eye casing, for the tie-rod forces which seal off the pump are determined by the end pressure of the pump so that the slight pressure of the first stage or of the first two stages can be taken with small screws.This step is known in principle from German Patent 10 72 100, but in this case the anchor bolts used and the intermediate clamping member do not allow any subsequent free choice in respect of the arrangement of the latter.

In another embodiment of the invention, the casing interior accommodating the part or parts carrying the flow is provided with an anti-corrosion and/or anti-erosion coating. In this way it is possible for the eye casing made from ordinary steel sheet to be used even for aggressive media, such as corrosive fluids of fluids carrying abrasive particles. All that is required in such cases is for the surfaces exposed to the medium to be lined with appropriate ly resistent materials.

Embodiments of the invention are described below by way of example with reference to the accompanying drawings, in which: Figures 1 and 2 show prior-art constuctions, Figure 3 is a schematic side elevation view of a pump and motor assembly embodying the invention, Figure 4 is a plan view of an eye forming part of the assembly of Figure 3, Figures 5to 8 show different forms of an eye embodying the invention, Figures9and 10 are views, in axial section showing centrifugal pumps embodying the invention, and each having an eye and an axial inlet, and Figure 11 is a side view showing a centrifugal pump embodying the invention in which the eye is used as the second stage and for the first stage there is used a stage corresponding to the remaining stages.

Figure 1 illustrates the six-stage type WKT 300 KSB centrifugal pump mentioned in the introduction while Figure 2 shows the pump construction according to KSB Type sheet No. 1754.21, also mentioned in the introduction.

Figure 3 shows a pump and motor assembly embodying the invention. Motor 1 drives a centrifugal pump 3 via a coupling 2, an arrangement with a vertical shaft having been selected for this exemplified embodiment. The centrifugal pump and motor are suspended by the eye 4, which is of a size such that it can rest on a support frame 5 while taking the weight of the motor 1 via a lantern 6. The inlet port 7 flanged on the eye 4 has a radia[ feed for the medium being pumped and is provided with a flanged-on bearing 8. The forces required to hold the centrifugal pump 3 together are provided by tie rods 9 which draw the delivery casing 10 and the eye 4towards each other.

Figure 4 is a plan view on the line IV-IV in Figure 3, showing a rectangular outside contourforthe eye.

The latter can therefore be very simply cut from a steel sheet, e.g. by flame cutting. All that is then required is to provide the holes for the fixings, the holes 11 being used for fixing to support frames or a foundation while holes 12 are used to accommodate the corresponding number of tie rods and holes 13 are used to fix the inlet port 7 to the eye casing 4.

Figures 5 to 8 show other possible shapes of the outer contour of the eye suitable for different applications. In Figures 5 and 6 fixings 14 have been cut out at the same time and contain the holes 11.

This type of construction enables the centrifugal pump to be assembled with the shaft horizontal or vertical. The different number of holes 12, 13 depend on the pressures in the centrifugal pump construction concerned. Figure 7 illustrates an eye outer contour starting from a square basic shape and intended to rest on a baseplate 15 shown in broken lines. Figure 8 illustrates a contour intended for a similar arrangement except that it is based on a rectangular shape. Figure 8 shows, on the left, half of one possible configuration and, on the right, half of another, the only difference between the two being the construction ofthe fixings 14 which are small in the left-hand half of the drawing and large in the right-hand half. The latter arrangement allows better material utilization in the manufacture of the eye.

In the pump assembly of Figure 3, the pump assemblies incorporating the eyes of Figures 4to 8 and the pump assemblies of Figures 9 to 11, the axial length of the eye 4 is the same as that of each of the other stage casings.

Figure 9 shows a finished eye 4 assembled with other pump stages and with the inlet number 7 flanged on eye 4 having an axial inlet. Fixing of member 7 to eye 4 is by means of small stay bolts 15 screwed into blind holes 13.

The tie rods 9 fitted through the holes 12 and carrying at their ends nuts bearing against the delivery casing 10 and the eye 4 respectively hold the individual stages together. The interior 18 chamber required in the eye 4 to accommodate the impellers 16 and any diffuser devices 17 isformed by machine tools, such as turning or milling machines.

Figure 10 shows a construction similar to that of Figure 9 except that the inlet member 7 is in the form of a spigot welded to the eye 4, preferably prior to machining of the eye. This arrangement is adopted because of the reverse arrangement of the stage casings, as compared with Figure 9.

Figure 11 shows a construction in which the eye is situated in the area of the second stage, e.g. because space conditions so dictate, and a casing 19 identical with the remaining stage casings takes over, as regards fluid flow, the function of the eye in the embodiments previously described, i.e. that of accommodating the pump inlet stage. This is possible because the eye and the other stage casings have the same axial length and because the pressures are still low in the region of the first two stages.

Claims

1. An eye for a multi-stage motor and pump assembly, in which the pump part consisting of a plurality of identical stage casings is held together by external tie rods, the latter being secured to the delivery casing and to the eye, and wherein the eye casing is cut from a steel sheet and its interior which accommodates the part or parts carrying the flow is brought to the desired configuration by machining.

2. An eye according to claim 1, in which the eye casing has an angular or polygonal outer contour.

3. An eye according to claim 1 or claim 2, in which fixings and/or guides provided on the eye casing are cut out in one operation together with the outer contour.

4. An eye according to any one of claims 1 to 3, in which the axial length of the casing corresponds to the axial length of each of the subsequent stage casings of the pump.

5. An eye according to any one of claims 1 to 4, in which the casing interior accommodating the part or parts carrying the flow is provided with an anticorrosion and/or anti-erosion coating.

6. A multi-stage motor and pump assembly, having an eye and a delivery casing and in which the pump part consisting of a plurality of identical stage casings is held together be external tie rods, the latter being secured to the delivery casing and to the eye, and wherein the eye casing is cut from a steel sheet and its interior which accommodates the part or parts carrying the flow is brought to the desired configuration by machining.

7. An eye for a multi-stage motor and pump assembly, substantially as hereinbefore described with reference to, and as shown in, any of Figures 3 to 10 of the accompanying drawings.

8. A multi-stage motor and pump assembly, substantially as hereinbefore described with reference to any of Figures 3 to 10 of the accompanying drawings.

9. Any novel feature or combination of features disclosed herein.