GB2072748A

GB2072748A - Multistage condensate pump

Info

Publication number: GB2072748A
Application number: GB8108153A
Authority: GB
Original assignee: Klein Schanzlin and Becker AG
Current assignee: Klein Schanzlin and Becker AG
Priority date: 1980-03-27
Filing date: 1981-03-16
Publication date: 1981-10-07
Also published as: FR2479346A1; GB2072748B; IT8120698A0; DE3011865A1

Abstract

The pump has a double suction intake stage with a double-suction rotor 4 arranged to deliver fluid to a second stage disposed axially above the intake stage, the double-suction rotor 4 being surrounded by a casing, affording two volutes (5, 6), Fig. 2 (not shown), which are disposed opposite one another and into which, in operation, fluid is discharged by the rotor 4. Each volute (5, 6) leads to a respective flow duct 12, 13 which extends spirally around the rotor axis towards said second stage. The pump further includes two slit-like intake passages 9 and 10 extending from the exterior of the pump casing to the rotor intake 11 nearer said second stage. The flow ducts 12 and 13 extend past the slit-like intake passages 9 and 10 without intersection therewith. <IMAGE>

Description

SPECIFICATION Multistage condensate pump THIS INVENTION relates to a multistage condensate pump having an intake stage with a doublesuction rotor surrounded by a double volute casing whose volutes are disposed opposite one another and have at their ends flow ducts for further conveyance of the medium being pumped.

To improve cavitation conditions in multistage condensate pumps with a low inflow (small NPSH), it has been found advantageous for the first rotor stage, also known as the intake stage, to be of the double suction kind. The space between an intake stage having a double-suction rotor and the subsequent stages of the pump as a source of difficulties as regards flow and also as regards casting, for the reason that the medium being pumped must be conveyed from the intake stage through the inflow zone of the double-suction rotor half nearer the next pump stage.

This problem may be solved, for instance, as in German Offenlegungsschrift 2,450,611, by the medium pumped being guided at the end of the volute by bends into piping in which the medium is conveyed through further bends to a delivery line.

It is an object of the invention so as to provide a multi-stage condensate pump in which the intake stage has such a form to minimize the radial size of the construction and the flow losses of the flowguiding elements after the intake stage and before a subsequent stage.

In accordance with the invention there is provided a multi-stage condensate pump having a double suction intake stage with a double-suction rotor arranged to deliver fluid to a second stage displaced axially from said intake stage, the double suction rotor being surrounded by a casing, affording two volutes which are disposed opposite one another and into which, in operation, fluid is discharged by the rotor, each said volute extending to a respective flow duct for further conveyance of the medium being pumped, each of said flow ducts extending spirally around the rotor axis from the end of the respective volute towards said second stage, the two flow ducts being disposed diametrally opposite one another in cross-section perpendiculartothe pump axis, the pump further including two slit-like intake passages extending from the exterior of the pump casing to the intake, nearer said second stage, of said double suction rotor, said flow ducts extending past said slit-like intake passages without intersection with the latter.

This guidance of fluid flow from the volutes in a pump embodying the invention provides a very gentle transition from the volute ends into the guide ducts and very iow-loss guidance of the flow in the guide ducts.

In accordance with a preferred feature, each flow duct changes steplessly from its cross-sectional shape at the volute exit to a semicircular or semiannular cross-section. Abrupt changes in crosssection or bends in the flow ducts are thereby avoided in a very simple manner. To further improve flow guidance the flow ducts preferably extend into a concentric annular chamber disposed before the next pumpstage or partitions and/or guide ribs are disposed in the exit region of the guide ducts and/or in the annular chamber. Extending the guide ducts around the slit-like passages facilitates very good flow guidance in the flow ducts, permits optimum construction of said intake passages and also provides an intake zone clear of piping or the like. Integrating these flow-guiding parts into the intake casing provides the additional advantage of a very compact item of reduced external diameter.

An embodiment of the invention is described below with reference to the accompanying drawings in which: Figure lisa partial longitudinal section view of a pump embodying the invention, and Figure 2 is a view in cross-section through the intake stage of the pump of Figure 1, along the line Il-Il.

Referring to the drawings, the intake stage 2 of a multistage vertical condensate pump is disposed in a pot casing 1. A double-suction rotor 4 driven by pump shaft 3 is disposed in stage 2 and delivers fluid pumped to the volutes 5, 6 of a double volute casing part surrounding rotor4. Fluid medium to be pumped enters the bottom rotor half 7 through a suction orifice 8 and enters the top rotor half 11 through two slit-like intake passages 9, 10. Respective flow ducts 12, 13 which extend spirally from the ends of the two volutes, so as to approach one another and the pump axis progressively with increasing distance upwardly along the pump axis, while winding around the pump axis, convey the fluid medium from the volutes 5 and 6 to an annular chamber 14 which lies axially below, and precedes, a second pump stage (not shown).

Figure 2 shows the two volutes 5,6 in section; chain lines show how the flow ducts 12, 13 extend in the manner just described.

It will be appreciated that, like the two volutes 5 and 6, the two spiral flow ducts 12, 13 are disposed diametrally opposite one another with respect to the rotary axis of the pump, so that, in cross section perpendicular to the pump axis at any position over the range over which the sections of the ducts 12, 13 in the cross-sectional plane are diametrally opposite one another.

Each of the slit-like passages 9, 10 extends radially through a respective region between one of the spiral ducts 12, 13 and the other of said ducts, so that the flow ducts 12, 13 extend past the passages 9, 10 without intersection with the flow passages.

Each of the flow ducts 12,13 changessteplessly from its cross-sectional shape at the volute exit to a semi-circular (or semi-annular, taking into account the shaft 3) cross-section immediately upstream the annular chamber 14 (i.e. immediately below chamber 14 in Figure 2). Abrupt changes in crosssection or abrupt bends in the flow ducts are thereby avoided in a very simple manner. To further improve flow guidance, partitions and/or guide ribs are disposed in the exit region of the ducts 12, 13 and/or in the annular chamber 14.

It will be appreciated from a comparison of Figures 1 and 2 that Figure 1 is somewhat diagrammatic in that as regards the region of the two volutes the parts of Figure 1 on opposite sides of the pump axis are not actually sections in the same plane, while the planes of the sections in the regions of the passages 9, 10 are in effect, rotated about the pump axis rela- tive to the planes of the sections in the region of the two volutes, as compared with Figure 2. The diagrammatic nature of Figure 1 is in the interests of ease of understanding, and the configuration to be adopted in practice will be clear to the person skilled in the art from the foregoing description.

Claims

1. A multistage condensate pump having a double suction intake stage with a double-suction rotor arranged to deliver fluid to a second stage dispiaced axially from said intake stage, the double suction rotor being surrounded by a casing, affording two volutes which are disposed opposite one another and into which, in operation, fluid is discharged by the rotor, each said volute extending, to a respective flow duct for further conveyance of the medium being pumped, each of said flow ducts extending spirally around the rotor axis from the end of the respective volute towards said second stage, the two flow ducts being disposed diametrally opposite one another in cross-section perpendicular to the pump axis, the pump further including two slit-like intake passages extending from m the exterior of thepump casing to the intake, nearer said second stage, of said double suction rotor, said flow ducts extending past said slit-like intake passages without intersection with the latter.

2. A condensate pump according to claim 1, in which each said flow duct changes steplessly from its cross-sectional shape at the volute exit to a semicircular cross-section centred on the pump axis.

3. Acondensate pump according to claim 1 or claim 2, in which said flow ducts extend into an annular chamber coaxial with said double suction rotor, said annular chamber being disposed upstream of the next pump stage.

4. A condensate pump according to any of claims 1 to 3, in which partitions and/or guide ribs are disposed in the exit region of said flow ducts.

5. A condensate pump according to claim 3 in which partitions andior guide ribs are disposed in said annular chamber.

6. A multistage condensate pump substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

7. Any novel feature or combination of features described herein.