GB2234553A

GB2234553A - A method of setting a working clearance in pumps

Info

Publication number: GB2234553A
Application number: GB9010548A
Authority: GB
Inventors: Graham Keith Lacy
Original assignee: APV Corp Ltd
Current assignee: SPX Flow Technology Crawley Ltd
Priority date: 1989-08-05
Filing date: 1990-05-10
Publication date: 1991-02-06
Anticipated expiration: 2010-05-10
Also published as: DE4024744C2; DE4024744A1; GB2234553B; GB9010548D0; GB8917971D0

Abstract

With reference to Figure 2, a device 1 for setting a working clearance between a centrifugal pump impeller 2 and an impeller casing 3 having an opening 4 aligned with the axis of rotation 5 of the impeller 2, comprises a flexible member 6 constructed so that it can overlay the impeller 2 with the casing 3 in place and then be drawn out of the casing 3 by way of the opening 4. The member 6 comprises a central portion with a plurality of finger portions 8 extending radially therefrom and spaced laterally from each other. A cord 15 is secured to the device 1, being wound around the finger portions 8 thereof. With the impeller 2 axially adjusted on its drive shaft so that a substantial clearance will exist when the casing 3 is re-fitted, the draw cord portions are passed through the opening 4 and the casing 3 replaced. The impeller 2 and its drive shaft are now pushed forward until the member 6 is clamped lightly between the impeller 2 and the casing 3. The casing 3 is now spaced from the impeller 2 by the thickness of the member 6. The axial position of the impeller 2 is next secured tightly, and the member 6 withdrawn, using a cord 15, by way of the opening 4. <IMAGE>

Description

1 IMPROVEMENTS IN OR RELATING TO CLEARANCE-SETTING DEVICES This invention

relates to clearance setting devices and provides a device for setting a working clearance between an impeller and an impeller casing, wherein the casing has an opening aligned with the axis of rotation of the impeller.

One method of setting the clearance comprises inserting a spacer plate behind the impeller. However, this method does not take account of possible variation of radial and/or axial clearance between the impeller and the casing, du[e'in part to manuracturing error. Consequently, rubbing could occur between the impeller and the casing.

Another method comprises fixing spacer tabs to the exterior of the impel 1 er. However this method, although theoretically more accurate, results in only a relatively smal 1 coverage of the impeller, and high spots could still exist (unless an excessive number of tabs is used).

According to one aspect of the present invention, a method of setting a working clearance between an impeller-and an impeller casing having an opening aligned with the axis of rotation of the impeller, comprises disposing a flexible member having the general shape of a disc between the impeller and the casing, adjusting the impeller axially so as to lightly clamp the member between the impeller and the casing and then withdrawing the member from the casing by way of the opening.

According to another aspect of the invention, a device for setting a working clearance between an impeller and an impeller casing having an opening aligned with the axis of rotation of the impeller, comprises a flexible member having the general shape of a disc and formed so that it can overlay the impeller with the casing in place i -2 and then be drawn out of the casing by way of the opening.

The disc-shaped member preferably comprises a plurality of radially extending portions spaced laterally from each other.

Where the impeller is mounted on a drive shaft and is secured in place by a nut to which access can be gained by way of the opening in the impeller casing, the aforementioned portions may extend radially from a central portion shaped to grip, in a resilient manner, the impeller securing nut.

The various aspects of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:

Figure 1 is a front view of the flexible member, Figure 2 is a view in perspective of the impeller with the flexible member in place, prior to fitting the impeller casing over the impeller, and Figure 3 is a view in perspective of the assembled impeller and casing, with the flexible member partly withdrawn.

With reference to the drawings, a device 1 for setting a working clearance between a centrifugal pump impeller 2 and an impeller casing 3 having an opening 4 aligned with the axis of rotation 5 of the impeller 2 is illustrated thereby.

The device 1 comprises a flexible member 6 having the general shape of a disc and formed and constructed so that it can overlay the impeller 2 with the casing 3 in place and then be drawn out of the casing 3 by way of the opening 4.

The device 1 is of resilient plastics material, and is of uniform thickness (0.5 mm in this example). The 0.5 mm thickness is the v n2 i same as the desired working clearance between the impeller 2 and the casing 3. As best shown in Figure 1, the disc-shaped member 6 comprises a central or hub portion 7 with a plurality of finger portions 8 extending radially therefrom. The finger portions 8 are spaced laterally from each other. The longitudinal edges of each finger portion 8 are substantially parallel to each other for the major part of their length.

The central portion 7 is formed with an oppositely-disposed pair of part-circular openings 9 spaced from each other by an oppositely disposed pair of flaps 10. The flaps 10 are spaced from each other by an opening 11 of elongate form, which interconnects the openings 9. The arrangement allows the central portion 7 to grip, in a resilient manner, the impeller securing nut 12 which is attached to the impeller drive shaft. The flaps are perforated by holes 14.

In use, with the impeller casing 3 removed (Figure 2) the device 1 is placed in position whereby the central portion grips the impeller securing nut 12.

A cord 15 is secured to the device, being wound around the finger portions 8 thereof, to form a harness, with two draw cord portions of substantial length extending away from the centre of the harness.

With the impeller 2 axially adjusted on its drive shaft so that a substantial clearance will exist when the casing 3 is re-fitted, the draw cord portions are passed through the opening 4 and the casing 3 replaced.

The impeller 2 and its drive shaft are now pushed forward until the member 6 is clamped lightly between the impeller 2 and the casing 3.

The casing 3 is now spaced from the impeller 2 by the thickness (0.5 mm) of the member 6. The axial position of the impeller 2 is next secured tightly, using locking bolts (not shown), and the member 6 withdrawn, using the cord 15, by way of the opening 4.

The member 6 flexes to overlay the impeller 2 when the casing 3 is in place, and also flexes to collapse when being drawn through the opening 4.

-1 c The holes 14 in the flaps 10 may be used instead of the fingers 8 to secure the cord 15 to the member 6.

It will be appreciated that the shape and/or thickness of the flexible member 6 can vary according to requirements.

1 ll i

Claims

1. A method of setting a working clearance between an impeller and an impeller casing having an opening aligned with the axis of rotation of the impeller, comprising disposing a flexible member having the general shape of a disc between the impeller and the casing, adjusting the impeller axially so as to lightly clamp the member between the impeller and the casing and then withdrawing the member from the casing by way of the opening.

2. The method of claim 1, wherein the flexible member comprises a plurality of radial ly-extending portions spaced laterally from each other.

3. The method of claim 2, wherein the flexible member comprises a central portion with a plurality of finger portions extending radially therefrom.

4. The method of claim 3, wherein the central portion is formed with an oppositely-disposed pair of openings spaced from each other by an oppositely-disposed pair of flaps.

5. holes.

The method of claim 4, wherein the flaps are perforated by

6. The method of any one of claims 1 to 5, wherein the flexible member is of resilient plastics material.

7. A device for setting a working clearance between an impeller and an impeller casing having an opening aligned with the axis of rotation of the impeller, comprising a flexible member having the general shape of a disc and formed so that it can overlay the impeller with the casing in place and then be drawn out of the casing by way of the opening.

8. A device as claimed in claim 7, wherein the flexible member comprises a plurality of radially-extending portions spaced laterally from each other.

i

9. A device as claimed in claim 8, wherein the flexible member comprises a central portion with a plurality of finger portions extending radially therefrom.

10. A device as claimed in claim 9, wherein the central portion is formed with an oppositely-disposed pair of openings spaced from each other by an opposite] y-di s posed pair of flaps.

11. A device as claimed in claim 10, wherein the flaps are perforated by holes.

12. A device as claimed in any one of claims 7 to 11, wherein the flexible member is of resilient plastics material..

13. A method of setting a working clearance between an impeller and an impeller casing having an opening aligned with the axis of rotation of the impeller, substantially as hereinbefore described with reference to Figures 1, 2 and 3 of the accompanying drawings.

14 A device for setting a working clearance between an impeller and an impeller casing having an opening aligned with the axis of rotation of the impeller, substantially as hereinbefore described with reference to Figures 1, 2 and 3 of the accompanying drawings.

Published 1991 atThe Patent Office. State House, 66/71 High Holborn. LondonWC I R47P. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach, Cross Keys. Ne-%, port. NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray. Kent