MULTI-STAGE CENTRIFUGAL PUMP

POMPE CENTRIFUGE A ETAGES MULTIPLES

English Abstract

A multi-stage centrifugal pump with an axially split
casing (10) and a number of impellers (14) carried by a
drive shaft (12) has inter-stage bushings (24) and rings
(22) for sealing each side of each impeller. Each bushing
(24) or ring (22) is conventionally prevented from
rotating by a radial pin protruding from the lower half of
the casing (10) into an axial slot in the periphery of the
bushing or ring. The pin is necessarily small and is
liable to shear, difficult to engage in the slot and, in
cases where the bushing (24) or ring (22) is diametrically
split, does not allow rotation of the lower half for its
removal without lifting the shaft (12). To avoid all
these disadvantages, the exposed end (37) of a tangential
pin (32) fitted in the casing (10) is flush with the join
face (28) of the casing and abuts against a shoulder (44)
formed by a recess (38) in the periphery of the bushing
(24) or ring (22). This pin (32) can be larger than the
known radial pin and is subjected to compression, not
shear.

French Abstract

Cette invention concerne une pompe centrifuge multi-étagée à joint longitudinal (10) comportant un certain nombre de roues (14) montées sur un arbre d'entraînement (12) et des douilles (24) et bagues (22) inter-étages pour isoler lesdites roues des deux côtés. Les douilles (24) et bagues (22) sont normalement empêchées de tourner par des goupilles radiales faisant saillie de la demi-coquille inférieure de l'enveloppe (10) et se logeant dans une fente axiale prévue dans le pourtour extérieur des douilles et bagues. Ces goupilles sont nécessairement de faibles dimensions et risquent donc de céder par cisaillement, sont difficiles à insérer dans les fentes correspondantes et obligent, dans les cas où les douilles ou les bagues sont du type fendu, à soulever l'arbre d'entraînement (12) pour enlever la moitié inférieure desdites douilles ou bagues que l'on ne peut autrement dégager. Pour éviter tous ces inconvénients, l'invention propose que le bout exposé (37) d'une goupille tangentielle (32) logée dans l'enveloppe (10) soit d'affleurement avec le joint longitudinal (28) de celle-ci et appuyé contre un épaulement (44) formé par une encoche (38) dans le pourtour de la douille (24) ou de la bague (220. Cette goupille (32) peut être de dimensions plus généreuses que les goupilles radiales des antériorités et, de plus, travaille non pas en cisaillement, mais en compression.

Claims

CLAIMS:
1. Means for preventing rotation of an axial-fixed
multi-stage bushing or ring in a high pressure multi-stage
centrifugal pump with an axially split casing which houses a
shaft carrying impellers; comprising:
a tangential pin means fitted into a hole provided
in either half of the casing at its joint face, which hole
does not extend to the exterior of the casing in order to
prevent leakage of pressurized fluid pumped by said high
pressure multi-stage centrifugal pump, the center-line of
the pin means being normal to the joint face and the exposed
end of the pin means being flush with said face; and
a recess in which the pin means engages provided
in the periphery of the bushing or ring.
2. Means according to claim 1, in which the pin means
is positioned at that side of the casing which places it
under compression if the bushing or ring tends to rotate in
the same direction as the shaft.
3. Means according to claim 1, in which the recess is
machined in a flange of the bushing or ring which, by
engagement in an annular groove in the casing, hold the
bushing or ring axially fixed.
4. Means according to claim 1, in which the casing is
split in a horizontal plane, the bushing or ring is split in
a different plane, and the pin means is fitted in a hole
machined in the upper of the casing.

Description

2046~65
TITLE
Multi-Stage Centrifugal Pump
BACKGROUND TO THE INVENTION
This invention relates to multi-stage centrifugal
pumps, and more particularly to means for preventing
rotation of an inter-stage bushing or ring in a multi-
stage centrifugal pump with an axially split casing which
houses a shaft carrying impellers.
DESCRIPTION OF THE PRIOR ART
A multi-stage centrifugal pump has a number of inter-
stage bushings and rings, sometimes called stage pieces
and wear rings, which fit within the casing and have to be
accurately positioned radially and locked against axial
and rotational movement. These bushings and rings have
essentially the same function as one another, namely to
seal each side of each impeller, but the bushings have a
larger radial thickness and may carry integral guide vanes
for the incoming fluid whereas the rings have a smaller
radial thickness and lack guide vanes. Radial positioning
is by means of a close fit between the periphery of the
bushing or ring and a bore machined in the casing. Axial
location is by means of a flange on the bushing or ring
which engages in an annular groove machined in the casing.
Hitherto, each bushing or ring has been prevented
from rotating by means of a small pin fitted into a radial
hole drilled in the base of the annular groove, said pin
protruding into an axial slot machined in the flange. The
pins have been fitted in the lower half of the casing in
the vertical plane containing the pump axis, so that the
axial slots in the bushings and rings could be engaged
with the pins during the assembly of the shaft and

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-- 2
impellers into the lower half of the casing. This
arrangement has the disadvantages that the pin is
necessarily small and is liable to shear if large or
cyclic loads are applied to it during operation of the
pump; it can be difficult to ensure correct engagement of
the pin in the axial slot during assembly; and, in cases
where the bushing or ring has been diametrically split to
permit its easy removal, the pin does not allow rotation
of the lower half to enable it to be removed without
lifting the shaft.
OBJECT OF THE lNv~N.ION
The object of the present invention is to avoid the
aforesaid disadvantages.
SUMMARY OF THE lNv~ ION
According to the invention, means for preventing
rotation of an inter-stage bushing or ring in a multi-
stage centrifugal pump with an axially split casing which
houses a shaft carrying impellers are characterised by a
tangential pin fitted into a hole provided in either half
of the casing at its join face, the centre-line of the pin
being normal to the join face and the exposed end of the
pin being flush with said face, and a recess in which the
pin engages provided in the periphery of the bushing or
ring.
Other objects and advantages of the invention will
become appararent from the following description of an
embodiment of the invention, given way of example :-
BRIEF DESCRIPTION OF THE DRAWINGS

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Figure 1 is a sectional side elevation of a multi-
stage centrifugal pump with a casing which is split
axially in a horizontal plane;
Figure 2 is a cross-section through the upper half of
the casing on the line 2-2 in Figure 1;
Figure 3 is an end view of a diametrically split
inter-stage bushing;
Figure 4 is a view of one half of the bushing in the
direction of the arrow 4 in Figure 3;
Figure 5 is an end view of an inter-stage ring which
is not diametrically split; and
Figure 6 is a side elevation of the ring shown in
Figure 5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figures 1 to 4 of the drawings, in
a preferred embodiment of the invention a multi-stage
centrifugal pump has a casing indicated generally at 10
which is split axially in a horizontal plane and houses a
power-driven shaft 12 on which there are rigidly secured
a plurality of impellers 14. Each impeller 14 is disposed
in a chamber 16 having an axial inlet 18 and a radial
outlet 20, the chambers 16 being connected in series in
well-known manner. An inter-stage ring 22 is disposed at
the inlet side of each impeller 14, and an inter-stage
bushing 24 carrying integral guide means 25 for the
incoming fluid is disposed at the other side thereof. As
exemplified in Figures 3 and 4, each bushing 24 and ring
22 is diametrically split in a plane 26 incline at, say'

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10~ to the horizontal, the split being below the joint face
28 of the casing 10 at that side of the casing 10 where
the periphery of the rotating shaft 12 moves upwardly.
The two halves of each bushing 24 (and ring 22) are
located together by dowels 30. Each bushing 24 (and ring
22) is prevented from rotating by a tangenti/al pin 32 (see
Figure 2) driven into a hole 34 machined in the upper half
36 of the casing 10 at its joint face 28, the centre-line
29 of the pin 32 being normal to the joint face 28 and the
exposed end 37 of the pin 32 béing flush with the joint
face 28. The pin 32 engages in a recess 38 machlned in a
flange 40 on the upper half 42 of the bushing 24 (or ring
22) the recess 38 including a shoulder 44 against which
the exposed end 37 of the pin 32 abuts. The flange 40
engages in known manner in an annular groove 45 machined
in the casing 10. In practice, due to manufacturing
tolerances, the exposed end 37 of the pin 32 may be
slightly short of the joint face 28 of the casing 10
without departing from the scope of the invention, but it
must not protrude beyond said face. The pin 32 is
positioned at that side of the casing 10 which places said
pin under compression if the bushing 24 (or ring 22) tends
to rotate in the same direction as the shaft 12.
In a modification exemplified by the ring 22 shown in
Figures 5 and 6, the bushing 24 and rings 22 are not
diametrically split, in which case the pins 32 can equally
well be fitted in the lower half 46 of the casing 10.
In another modification, the recess 38 is machined in
a suitable part of the periphery of the bushing 24 (or
ring 22) other than the axial location flange 40 thereon.
Arrangements in accordance with the invention have
the advantages that the pin 32 can be much larger than the

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radial pin used hitherto and is in compression, not shear,
so that it will readily withstand all anticipated loadings;
there is a greater certainty of correct engagement of the
pin 32 in the recess 38, and if engagement is not achieved
further assembly of the pump is prevented; and, in cases
where the bushing 24 (or ring 22) is diametrically split and
the pin 32 is fitted in the upper half 36 of the casing 10,
the lower half 48 of the bushing 24 or ring 22 can be
rotated to enable it to be removed without lifting the
shaft.
All of the features disclosed in this
specification (including any accompanying claims, abstract
and drawings), and/or all of the steps of any method or
process so disclosed, may be combined in any combination,
except combinations where at least some of such features
and/or steps are mutually exclusive.
Each feature disclosed in this specification
(including any accompanying claims, abstract and drawings),
may be replaced by alternative features serving the same,
equivalent or similar purpose, unless expressly stated
otherwise. Thus, unless expressly stated otherwise, each
feature disclosed is one example only of a generic series of
equivalent or similar features.
The invention is not restricted to the details of
the foregoing embodiment(s). The invention extends to any
A

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novel one, or any novel combination, of the features
disclosed in this specification (including any
accompanying claims, abstract and drawings), or to any
novel one, or any novel combination, of the steps of any
method or process so disclosed.

Representative Drawing