Fluid pump
The invention relates to a fluid pump having a pump priming system.
Most existing water pumps are primed by extracting the air from the pump from the top
of the pump suction tube. This has historically been the accepted as the best position
from which to prime a pump since it is fairly close to the centre line of the pump and
hence away from the pressure side of the impeller into which the water is centrifuged.
However, when the pump is partially primed with part water and part air there is a
tendency for water in the suction tube to start to rotate due to the motion of the impeller.
This water then tends to enter the priming port, along with any remaining air, causing it
to be sent through the priming system, thereby reducing its efficiency. This then extends
the "hand over" time, the time between water entering the pump and the pump
generating pressure, and sometimes results in unacceptably large quantities of water
passing through the priming system.
When priming a pump from the conventional top of the suction tube position there are
many occasions when water is drawn into the priming system in addition to air. The
relatively large quantities of water being pulled into the priming system can result in
consequently longer priming times, higher loads being imposed on priming components,
higher wear and higher corrosion due to the water presence. There is therefore a need
for there to be a reduced volume of water passed into the priming system and a quicker
conversion from the unprimed to the primed condition.
A solution which has been proposed when priming a pump from the top of the suction
tube is to provide disrupter blades within the suction tube, to prevent the water in the
suction tube from rotating. Although this solution has had some success it is not very
effective.
Another proposed solution has been to locate the priming port within the pump body,
towards the top and rear of the low pressure impeller, on the pressure side of the
impeller. However, this has the disadvantage that the pump is not being primed from an
area of suction pressure, which results in a relatively long hand over time.

According to an aspect of the present invention there is provided a fluid pump
comprising:
a pump body;
a fluid inlet;
a first impeller;
impeller seal means provided on the pressure side of the first impeller between
the first impeller and the pump body; and
a pump priming system;
and characterized by further comprising a pump priming conduit extending from
the inlet, suction, side of the first impeller, through the impeller, and through the pump
body to the pump priming system,
the pump priming conduit being provided through the first impeller radially
inboard of the impeller seal means, the impeller seal means separating the inlet side of
the impeller from its pressure side.
Connecting the pump priming system to an area of the pump inboard of the low
pressure impeller seal provides a quicker and more positive prime than is possible
connecting to the standard top of suction tube position.
The impeller seal means preferably comprises a rear wear ring provided on the
pressure side of the first impeller, between the pump body and the impeller. The pump
priming conduit preferably further extends through the rear wear ring.
The point where air is extracted from the pump is thereby as far inboard as possible and
inside the rear wear ring. Taking priming air from this position results in an almost
instantaneous hand over from unprimed to primed condition. This in turn results in only
very small quantities of water entering the priming system with subsequent reduced
loading in the priming system, reduced wear and quicker priming times to generate
pressure.
The fluid pump preferably further comprises a second impeller mounted for axial
rotation and provided after the first impeller. Preferably, the first impeller is a low
pressure impeller and the second impeller is a high pressure impeller. The second
impeller is preferably a regenerative high pressure impeller. The second impeller is
preferably provided within an impeller cavity defined by an impeller recess provided

within the pump body and a cover plate. The rear wear ring is preferably provided
between the first impeller and part of the cover plate.
Preferably, the high pressure impeller facing faces of the impeller recess and the cover
plate are provided with fluid channels around which fluid flows as its pressure is raised
by the high pressure impeller. The fluid channels are preferably part-annular in shape,
preferably extending in a part circular path from approximately 15 degrees to
approximately 345 degrees.
The pump priming conduit preferably extends through the cover plate. The pump
priming conduit preferably extends axially into the cover plate from one side, then
radially outwards through the cover plate, and axially out of the cover plate on its other
side. Preferably, the pump priming conduit extends axially out of the cover plate on its
other side between the ends of the cover plate fluid channel.
Routing the pump priming conduit through the cover plate enables the point where air is
extracted from the pump to remain as far inboard as possible, and inside the rear wear
ring.
Embodiments of the invention will now be described in detail, by way of example only,
with reference to the accompanying drawings, in which:
Figure 1 is a diagrammatic sectional view of part of a dual pressure water pump
according to a first embodiment of the invention;
Figure 2 is an enlarged view of part of Figure 1;
Figure 3 is a diagrammatic representation of part of the high pressure impeller facing
face of the cover plate of Figure 1; and
Figure 4 is a diagrammatic sectional view of part of a single pressure water pump
according to a second embodiment of the invention.
Referring to Figures 1 to 3, a first embodiment of the invention provides a dual pressure
water pump 10 comprising a pump body 12, a fluid inlet (shown generally at 14), a first,
low pressure, impeller 16, a second, high pressure, impeller 18, a pump priming system
20, a pump priming conduit 22 and a rear wear ring 24.

The pump body 12 is bolted onto a pump bearing housing 26, in which the pump motor
(not shown) is provided for driving a pump shaft 28 to which the impellers 16, 18 are
coupled.
The low pressure impeller 16 is provided within a first impeller cavity 30 defined by the
pump body 12. The high pressure impeller 18 is provided within a second impeller
cavity 32, defined by an impeller recess 34 formed in the pump body 12 and a cover
plate 36. The high pressure impeller 18 closely fits within the impeller recess 34.
The high pressure Impeller facing faces 34a, 36a of the impeller recess 34 and the
cover plate 36 have water channels 38 provided in them, as shown in Figure 3, around
which water spirals as it is driven through the high pressure impeller 18 and its pressure
is raised. The water channels 38 are part-annular in shape and extend in part circular
paths around the cover plate 36 and the impeller recess 34. The water channels 38
paths extend part-circularly from approximately 15 degrees to approximately 345
degrees (approximately 12.30 to 11.30 on a circular clock face), with a gap 40 being
provided between the water inlet 38a and water outlet 38b ends of the channels 38.
This gap 40 allows the water inlet 38a to be positively separated from the water outlet
38b.
The rear wear ring 24 is provided between the low pressure impeller 16 and the inboard
end of the high pressure impeller cover plate 36.
The pump priming system 20 of this example comprises a piston primer of a type which
will be well known the person skilled in the art and so will not be described in detail
here.
The pump priming conduit 22 comprises several sections, as follows. The first section
is provided through the pump body 12 and comprises first and second interconnecting
axial bores 42, 44. At their distal ends the first bore 42 is coupled to the pump priming
system 20 and the second bore 44 is coupled to the second section of the pump priming
conduit 22.
The second section of the pump priming conduit 22 is provided through the high
pressure impeller cover plate 36 and comprises a radial bore 46 and two axial holes 48,

50. The radial bore extends from the edge of the cover plate 36 towards its middle,
through the section of the cover plate at the gap 40 between the ends of the water
channel 38. The outer end of the radial bore 46 is blanked off by part of the pump body
12, or can alternatively be blanked of with a blanking plug.
The first axial hole 48 extends from the high pressure impeller side of the cover plate
36, through the gap 40, to the radial bore 46, and couples to the distal end of the
second axial bore 44 in the pump body 12. The second axial hole 50 extends from the
other side of the cover plate 36, at a position towards the centre of the cover plate 36,
through the cover plate 36 to the bottom of the radial bore 46. The second axial hole 50
is coupled to the third section of the pump priming conduit 22.
The third section of the pump priming conduit 22 extends through the rear wear ring 24,
and comprises an axial hole 52 provided through the rear wear ring 24. The axial hole
is coupled at one side to the axial hole 50 and at its other side to the fourth section of
the pump priming conduit 22, which comprises a cavity 54 between the rear wear ring
24 and the low pressure impeller 16.
The fourth section of the pump priming conduit 22 extends through the low pressure
impeller 16 and comprises a number of axial holes 56 provided through the low
pressure impeller 16, connecting the cavity 54 to the suction side of the low pressure
impeller 16. The axial holes 56 also act to balance the pressure across the low
pressure impeller 16. The rear wear ring 24 separates the suction side of the low
pressure impeller 16 from its pressure side.
The pump priming conduit 22 thereby connects the rear of the pump body 12,
connected to the priming system 20, to the cavity space inboard of the rear wear ring 24
of the low pressure impeller 16. The connecting axial holes 56 in the low pressure
impeller 16 connect the cavity 54, where priming occurs, to a pump suction tube (not
shown) coupled to the inlet 14.
In use, the pump priming system 20 draws air out of the pump 10, causing water within
a pump suction tube coupled to the inlet 14 to rise up into the pump 10. When the
pump 10 is almost primed, with the low pressure impeller 16 partially filled with water,
the centrifugal force of the impeller 16 throws the water outwards and the air remaining

within the pump 10 collects towards the centre of the impeller 16 from where it is taken
through the pump priming conduit 22 to the priming system 20.
Figure 4 shows a single pressure water pump 60 according to a second embodiment of
the invention. The single pressure water pump 60 is substantially the same as the dual
pressure water pump 10 of the first embodiment, but only has a low pressure impeller
16 and the following consequential modifications. The same reference numbers are
retained for corresponding features.
In this embodiment, the rear wear ring 62 is provided between the low pressure impeller
16 and the pump body 64.
The first section of the pump priming conduit 22, extending through the pump body 64,
comprises a first axial bore 42 and a second, generally radial bore 66 extending at an
angle downwards from the top of the pump body 64, through the axial bore 42, towards
the middle of the pump body 64 where it meets the rear wear ring 62. The bottom of the
radial bore 66 is coupled to an axial hole 68 provided through the rear wear ring 62.
The axial hole 68 is coupled to the cavity 54 between the rear wear ring 62 and the low
pressure impeller 16.
Various modifications may be made without departing from the scope of the present
invention. The impellers may be of a different size and type to those described. The
pump priming conduit may follow a different path from the pump priming system to the
rear of the low pressure impeller to those described.
The described embodiments provide various advantages, as follows. Connecting the
pump priming system to an area of the pump inboard of the low pressure impeller seal,
in these examples, within the diameter of the rear wear ring, provides a quicker and
more positive prime than is possible connecting to the standard top of suction tube
position. The point where air is extracted from the pump is as far inboard as possible
and inside the rear wear ring. Taking priming air from this position results in an almost
instantaneous hand over from unprimed to primed condition. This in turn results in only
very small quantities of water entering the priming system with subsequent reduced
loading in the priming system, reduced wear and quicker time to pressure generation.

Claims
1. A fluid pump (10, 60) comprising:
a pump body (12, 64);
a fluid inlet (14);
a first impeller (16);
impeller seal means (24) provided on the pressure side of the first impeller
between the first impeller and the pump body; and
a pump priming system (20);
and characterized by further comprising a pump priming conduit (22) extending
from the inlet, suction, side of the first impeller, through the impeller, and through the
pump body to the pump priming system,
the pump priming conduit being provided through the first impeller radially
inboard of the impeller seal means, the impeller seal means separating the inlet side
of the impeller from its pressure side.
2. A fluid pump as claimed in claim 1, wherein the impeller seal means comprises a
rear wear ring (24) provided on the pressure side of the first impeller, between the
pump body and the impeller and the pump priming conduit extends through the rear
wear ring.
3. A fluid pump as claimed in claims 1 or 2, wherein the fluid pump further comprises a
second impeller (18) mounted for axial rotation and provided after the first impeller.
4. A fluid pump as claimed in claim 3, wherein the first impeller is a low pressure
impeller and the second impeller is a high pressure impeller.
5. A fluid pump as claimed in claims 3 or 4, wherein the second impeller is provided
within an impeller cavity defined by an impeller recess (34) provided within the pump
body and a cover plate (36).
6. A fluid pump as claimed in claim 5, wherein the high pressure impeller facing faces
of the impeller recess and the cover plate are provided with fluid channels (38)
around which fluid flows as its pressure is raised by the high pressure impeller.

7. A fluid pump as claimed in claim 5, wherein the fluid channels are part-annular in
shape, extending in a part circular path from approximately 15 degrees to
approximately 345 degrees.
8. A fluid pump as claimed in claim 7, wherein the pump priming conduit extends
through the cover plate.
9. A fluid pump as claimed in claim 8, wherein the pump priming conduit extends
axially into the cover plate from one side, then radially outwards through the cover
plate, and axially out of the cover plate on its other side.
10. A fluid pump as claimed in claim 9, wherein the pump priming conduit extends
axially out of the cover plate on its other side between the ends of the cover plate
fluid channel.

A dual pressure
water pump (10) comprising a
pump body (12), a low pressure
impeller (16), a high pressure
impeller (18), a pump priming
system (20), a pump priming
conduit (22) and a rear wear ring
(24). The high pressure impeller
(18) is provided within a cavity
(32), defined by an impeller
recess (34) and a cover plate
(36). The rear wear ring (24)
is provided between the low
pressure impeller (16) and the
inboard end of the cover plate
(36). The pump priming conduit
(22) comprises: first and second
axial bores (42, 44) through the
pump body (12); a radial bore
(46) and two axial holes (48,
50) through the cover plate (36);
an axial hole (52) through the
rear wear ring (24); a cavity
(54) between the rear wear
ring (24) and the low pressure
impeller (16); and axial holes
(56) through the low pressure
impeller (16), connecting the
cavity (54) to the suction side of
the low pressure impeller (16).