Centrifugal pump with an annular shroud

Details Centrifugal pump with an annular shroud Centrifugal pump with an annular shroud

1990-12-13

1992-12-15

Denion, Thomas E.

Rotary kinetic fluid motors or pumps

With separating means or guard for solid matter in working...

4151721, 4151701, 277 47, 277152, 384130, F03B 1108

Patent

active

051711265

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a fluid flow machine.
In fluid flow machines subjected to the action of a flowing, solids-containing medium, there is the danger of erosion inside the fluid flow machine. Although this can be counteracted by appropriate lining of the housing, a particularly susceptible location nevertheless exists in the region of the shaft seal. The solids contained in the flowing medium, which can have a particle size of up to 1 mm, can destroy the shaft seal itself or the parts of the housing which hold the shaft seal. This can result in premature failure of the fluid flow machine.


OBJECT OF THE INVENTION

It is an object of the invention to provide a means which, in a fluid flow machine subjected to the action of a flowing medium containing solids in the above-mentioned size range, can protect a chamber surrounding the shaft seal, and the shaft seal itself, against erosion.


SUMMARY OF THE INVENTION

The invention is embodied in a fluid flow machine, particularly in a centrifugal pump, which comprises a housing, a shaft member rotatably mounted in the housing, an impeller member on the shaft member, a shaft seal between the shaft member and the housing downstream of the impeller member, and an annular shroud which is disposed in the housing and surrounds at least a portion of the shaft seal with spacing. The shroud has a first end which is carried by the housing and a second end which confronts the impeller member. The second end of the shroud is spaced from the shaft member and/or from the impeller member.
Practical tests with a solids concentration of up to 100 mg per cubic decimeter have surprisingly shown that, with an annular element designed according to the main claim, erosion by solids contained in the flowing medium can be arrested.
In tests with an impeller having a floating ring seal on the side thereof facing the shaft seal, the floating ring seal was damaged within a very short period of time in the absence of the annular element. When, instead, an annular element in accordance with the invention was arranged in the chamber accommodating the shaft seal, no erosion marks were detectable after an extended test period even on the floating ring seal.


BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1 to 5 show differently formed annular elements.
FIG. 4 shows a non-contact type seal 16 between the impeller 2 and the housing 1. The seal 16 is integral with the shroud 12.
FIG. 5 shows a shroud 12 which has an undercut portion 18 facing away from the impeller 2.


DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a housing 1 of a flow machine, which is here constructed as a centrifugal pump, as well as an impeller 2 inside the housing 1. In the illustrated embodiment, the impeller is equipped with floating ring seals 3,4 on the suction and pressure sides. The impeller 2 is affixed to a shaft 5 as are a protective sleeve 6 for the shaft and a shaft seal in the form of a mechanical seal 7. Furthermore, in the region of the impeller hub 8, the impeller 2 has bores 9 for the equalization of axial thrust, and the bores 9 are located on the pressure side in the cover disc of the impeller.
An annular element 12 secured to the housing 1, and here to a housing cover 11 on the pressure side, is disposed in the chamber 10 surrounding the shaft seal 7. It extends in the region between the floating ring 13 affixed to the impeller, and the impeller hub 8 and shaft seal 7. The free end face of the annular element 12 has a surface 14 running radially of the shaft, and a tube 15 oriented axially of the shaft seal 7 is applied to the location of the surface 14 at which the diameter of the latter is a minimum. The annular element 12, which is here constructed as a shaped part of sheet material, can also be in the form of a thick shaped part having an undercut on the side thereof facing the shaft seal. Moreover, it can be integral with the floating ring 16 affixed to the housing.
The embodiment of FIG. 2 largely corresponds to that of FIG. 1. A difference is that, at its free end face, the annular element 1

REFERENCES:
patent: 2270054 (1942-01-01), Hogan
patent: 2407218 (1946-09-01), Beier
patent: 2649050 (1953-08-01), Dibdin
patent: 2722439 (1955-11-01), Brummer
patent: 2798438 (1957-07-01), Greathouse
patent: 3213798 (1965-10-01), Carswell
patent: 3677659 (1972-07-01), Williams
patent: 3881840 (1975-05-01), Bunjes

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