Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF T~E INVENTION
The present invention relates to a self-priming
centrifugal pump for dangerous, particularly radio-
active liquids.
5BACKGRO~ND OF THE INVENTION
, Particular precautions should be taken when
transferring dangerous liquids, particularly r~dio-
~ active liquids, between two recipients (reservoirs,
; apparatus, etc... ), one being a lower recipient and
10 the other an upper recipient, by means of a pump,
namely:
a) the pump must be placed above the lower
recipient, any damage of the pump leading to a leakage
,' does not lead to spillage of all the liquid of the
,, lS recipient,
' b) the delivery pipe must not be immersed
in the liquid of the upper recipient, a stoppage
of the pump or a leakage must not siphon the contents
of the upper recipient,
c) the pump must be dismountable without inter-
rupting the pipe between the two recipients,
~ d) when the pump is used, more especially
¦ for radio'active liquids, it may be provided to place
~ the two recipients, the pump and the pipes in a "cell".
1,~ It is advantageous to place the pump on the
,~ ceiling of the cell, with the vertical drive shaft
passing through the ceiling slab, the electric motor
', of the pump thus being outside the cell, therefore
! , easily accessible.
A pump allowing such transfers of liquid and
presenting these various advantages has been described
in French Patent No. 76 24748.
The pump described in this Patent comprises,
~ on the outside, a bowl on which are welded the suction
'i 35 and delivery pipes and an inner hydraulic part which
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: is disposed (with seal) in said bowl and which may
be dismounted vertically with protection.
The present invention is a pump of which the
configura~ion is the same as that described in said
French Patent but which proposes a different inner
hydraulic part which is particularly better adapted
to the transfers of liqu.ids with low flowrates (for
example of the order of 2 m3/hr.3.
SVMMARY OF THE INVENTION
,. 10 The present invention therefore relates in one aspect to
a vertical self-priming centrifugal pump, placed
beneath a concrete slab, constituted by a fixed bowl
welded to suction and delivery pipes and fixed under
said slab and by an inner hydraulic part disposed
. 15 in tight manner in said bowl and adapted to be extrac-
:? ted via the top, characterized in that said hydraulic
part is constituted by a wheel with radial vanes
driven by a drive motor traversing said slab, said
wheel rotating between a lower plate provided with
20 a suction hole and an upper part.ition forming the
bottom of a chamber and having an oval groove hollowed
out therein on the wheel side, said groove passing
around said partition and being closed at one of
its ends and terminated by a hole at the other of
~5 its ends, said hole allowing ev~ouation of ~he liquid.
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Another aspect of the invention is as follows:
A vertical self-priming centrifugal pump, placed
beneath a concrete slab, constituted by a fixed bowl welded --
to a suction pipe and a delivery pipe and by a mobile
equipment adapted to be extracted via the top, said
equipment being tightly arranged in said bowl so as to form
a suction chamber and a delivery chamber isolated from each
other, characterized in that:
the hydraulic part of said pump is constituted by a
wheel with radial vanes driven by a drive shaft;
"J, 15 said wheel rotates between a lower plate provided with
a suction hole coming out in said suction chamber and an
upper partition having an oval groove hollowed out therein
on the wheel side, said oval groove terminating in a first
hole allowing evacuation of the liquid in said delivery
chamber; said upper partition being provided first with a
second hole located virtually on the same radius as said
first hole but nearest the axis and secondly on its face
;~ opposite said wheel with a plate separating said holes.
~ BRIEF DESCRIPTION OF T~E DRAWINGS
i 25 The invention will be more readily understood on
reading the following description with referenre to the
accompanying drawings, in which:
Fig. 1 is a general vertical section schematically
showing the positions of the pump and of its motor in a
concrete slab.
Fig. 2 iq a vertical section through the pump.
Fig. 3 is an exploded view in perspective of the
hydraulio part. ;;
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Fig. 4 is a perspective view of the lower
closure of the hydraulic part.
Fig. 5 is a vertical section through the dis-
mountable equipment.
5Fig. 6 is an enlarged vertical section of
the hydraulic part.
Fig. 7 is a seal design.
DETAILED DESC~IPTION OF THE DRAWINGS
Referring now to the drawings, and firstly
10 to Fig. 1 which shows the general arrangement, a
horizontal concrete slab 3 separates an upper cell
1 and a lower cell 2. Cell 2 containing dangerous
products is inaccessible to the personnel, whilst
J; cell 1 is intended to remain clean and accessible.
15The pump 4 is placed in the lower cell, whilst
, the drive motor 7 is located in cell 1.
q Assembly of the motor includes a cage element
8, the drive shaft 6 and a ball bearing housing 5.
A coupling is placed between the motor and the shaft.
20As to the general constitution of the pump,
it is constituted by an outer bowl with conduit,
a dismountable equipment, a rotating hydraulic equip-
! ment, ball bearings, fixed seals, rotating seals.
The pump is thus constituted by a bowl 15,
25 generally cylindrical in shape, of which the open
upper part forms a flange fixed to the concrete slab
3 and of which the lower part is closed.
The bowl comprises three welded conduits (and
welded to the pipes): a suction conduit 18, a delivery
30 conduit 24 and a ventilation conduit (not shown).
The suction conduit is welded to the pipe conducting
the fluid to be pumped.
The delivery conduit is welded to the pipe
conducting the pumped liquid~
35The ventilation conduit is connected to a
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general ventilation system.
The bowl must be considered as fixed and con-
stituting a whole with the pipes.
`In the bowl is located all the hydraulic part
5 of the pump; this part is adapted to be extracted
; and comprises a rotating equipment and a mobile equip-
1 ment (the adjective mobile being employed to recall
s that said mobile equipment is extractable but, in
the operation of the pump, said mobile equipment
10 is7 of course, fixed).
The rotating equipment is shown in Fig. 2
mounted in the bowl, and in exploded view for the
vaned wheel in Fig. 3.
Figs. 2 and 3 show the rotating equipment
¦ 15 which comprises:
- a drive shaft 6 guided in the upper part
¦ by the ball bearings 25,
- the packings (or rotating seals) 9,
- at 13, at the lower end of the shaft, a
~ 20 vaned wheel of which the radially disposed vanes
J, are rectangular and regularly spaced apart. The arc
of circumference between two consecutive vanes is
included between 10 and 30 and preferably close
to 15. It will be noted that the vaned wheel compri-
25 ses a solid central ring 34 (Fig. 6) (not vaned).
i Figs. 2, 3, 4, 5 and 6 also show the mobile
equipment which, to within a few details, is in the
;-~ form of a piece of revolution about the axis of the
;J (vertical) drive shaft 6.
The upper part of the mobile equipment compri-
ses flat parts which, abutting on corresponding flat
parts of the bowl, ensure tightness thanks to two
seals 30 and 32 (Fig. 5).
I The lower part of the mobile equipment forms
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a cylindrical box limited laterally by a wall 11,
downwardly by the removable base plate 14 (held in
place by screws 33 - Fig. 6) pierced wlth an orifice
provided with a nozzle ]6, and upwardly by a plate
perforated with holes 29. The central part of
this mobile equipment surrounds the drive shaft 6,
obviou~ly leaving the necessary space for the or
each packing 9. Inside the cylindrical box lies a
horizontal partition 20 which divides the interior
10 of the box into two parts, a lower part which will
contain the vaned wheel 13 and an upper part 12 (Fig.
7) forming delivery chamber.
Said partition 20 therefore defines the lower
chamber in which the vaned wheel 13 is disposed;
15 this partition and the role that it performs in the
invention are described hereinafter with reference
more particularly to Figs. 4 and 6.
This partition is in the form of a thick circu-
lar disc in which a groove 23 is made on the lower
20 face. (It is recalled that Fig. 4 shows the partition
turned over in order to show the groove).
The groove terminates in a hole 21 traversing
, the partition 20. A second hole 22 lying on the same
¦ radius as the first hole 21, but nearer the centre,
25 likewise traverses the partition 20.
In the upper part (cf. in particular Figs.
2 and 3), a small plate 17 separates the two holes
21 and 22.
The groove 23 is surrounded by a flat part
30 35.
Fig. 6 shows that the groove 23 is in the
form of a semi-oval, for example a "basket handle".
Similarly, Fig. 6 shows that the lateral wall
'~ 11 must, inside, present in the lower part, a concave
35 section 31 extending the section of the groove 23.
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The relative dimensions (in diameter) of the
groove 23 and of the vaned wheel 13 are clearly indi-
cated in Fig. 6: the vane must occupy between 3/4
and 2/3 of the groove.
With Ra being the maximum radius of the vaned
wheel, Re the outer radius of the groove, Ri its
inner radius, the following is preferable.
Re ~ (Re Ri) ~ a > Re ~ ~ (Re ~ Ri~-
On the contrary, the radius Rm of the hub
10 34 of the vaned wheel 13 must be notably smaller
than the inner radius Ri of the groove.
Fig. 6 shows that there is a clearance between
the vaned wheel 13 and the partition 20 on the one
hand, and the base plate 14, on the other hand. This
lS clearance must allow free rotation of the wheel,
but must be small enough for the capillary forces
I to ensure tightness of the two sides of the vaned
¦ wheel.
j A clearance of 0.1 mm may be proposed as pre-
s 20 ferred value.
Correct operation of the pump according to
! the invention involves, as the specialist will readily
1 appreciate, that there is independence, i.e. prefe-
1 rably tightness, between the suction chamber 19 (Figs.
25 2 and 7) comprised between the bowl and the mobile
equipment and the delivery chamber 12 (Fig. 7).
A seal may be placed between the wall 11 and
the boss 39 of the bowl, or metal segments 38 may
preferably be placed in grooves 36, 37 in the wall
' 30 11. The segments are preferably two in number.
¦ It will be noted that it is imperative to
3 leave a clearance between the diameter of the groove
~j bottom and the inner diameter of the segment, in
order to allow assembly of the pump.
A slight leakage may be tolerated at the level
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of the metal segments; the sole drawback thereof
is that the flowrate of the pump is reduced, but
only very slightly.
The mode of operation of the pump according
to the invention which, it is recalled, is a self-
priming centrifugal pump, will now be briefly des-
cribed.
The starting point is a stopped pump containing
;enough liquid for immersion of the wheel; there is
:10 air in the suction pipe and in the upper part of
the bowl.
Upon rotation, the liquid present in the groove
23 is driven, through hole 21, into chamber 12.
This volume of liquid is replaced by the same
volume of air coming from conduit 16.
`,Rotation of the wheel mixes water and air
and an unstable "emulsion" leaves via hole 21. In
zone 12 there is separation of the air which leaves
via holes 29 and of the water which drops via hole
22 towards the wheel.
The plate 17 separating the two holes prevents
the emulsion from dropping through hole 22 before
the separation of the water and air.
The same cycle is renewed until all the air
of the suction pipe has been evacuated towards deli-
very. The liquid to be sucked then fills the pump
which takes its normal hydraulic regime as peripheral
channel pump. Suction takes place in the bottom of
the bowl via conduit 16, delivery occurs via hole
21 in chamber 12 then via holes 29 in the delivery
chamber 12' and the delivery conduit 24.
A pump is therefore set into operation, which
is located above the reservoir of liquid to be dis-
placed, without any valve, this eliminating the risk
of leakage.
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For dismantling the pump, it will be noted
that, by removing the motor, then the coupling, the
whole interior of the pump: mobile equipment and
' rotating part, can be extracted through the hole
in the separating slab. The pump being placed abo~e
the reservoir and the pipes being welded to the bowl
which remains in place, there is no spilt liquid.
It is necessary to protect the personnel fro~
the liquid remaining on the extracted part of the
10 pump when said liquid is radio-active.
Finally, the dimensions and characteristics
of one of the pumps which may be made according to
the invention will be mentioned:
- vaned wheel with a diameter of 90 mm; thick-
15 ness 10 mm and comprising 24 vanes;
- speed of rotation of the drive shaft:
2900/rpm; with said pump and pumping cold water whose
; level is at 6.5 m below the pump, a flowrate of 1500
l/hr. is ensured if the delivery level of the water
20 is at 46 m, and of 2000 l/hr. if the delivery level
is at 25 m.
This same wheel, used in a known centrifugal
pump, would give a total manometric lift about 4
times lower.
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