Note: Descriptions are shown in the official language in which they were submitted.
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Method for pumping a liquid, pumping station, and
pumping area
[0001] The invention relates to the technical field of
pumping stations and pumping areas for liquid. More
specifically, the invention relates, according to a
first aspect, to a method for pumping liquid. According
to a second aspect, the invention relates to a pumping
station, and according to a third aspect, to a pumping
area.
State of the art
[0002] FR2837244 describes a pumping station which can
be used to pump or raise spent waters from connecting
underground pipelines to the surface of the ground.
This pumping station comprises one (or more) pump(s)
which is (are) housed in a tank. This tank comprises an
inlet opening into which is introduced an intake
pipeline (or spent liquid pipeline) conveying, for
example, spent waters from a gravity network. The spent
waters leaving the intake pipeline are poured into a
main duct towards the pump or pumps which can direct
these waters by pumping to an outlet pipeline.
[0003] The pumping method and the pumping station of
FR2837244 present some drawbacks. It is fairly complex
to use; its incorporation in a pumping area is also
fairly complex; finally, its incorporation in a pumping
area is costly.
Summary of the invention
[0004] According to a first aspect, one aim of the
invention is to provide a method for pumping liquid
that is simpler, that is less costly, and whose
implementation in a pumping area is simpler. To this
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end, the inventors propose a method for pumping liquid
from a spent liquid pipeline comprising a spent liquid
inlet and a spent liquid outlet and configured in such
a way that said liquid can flow from said spent liquid
inlet to said spent liquid outlet by gravity, said
method comprising the following steps:
providing a first pump for pumping said liquid,
comprising an inlet for liquid to be pumped and an
outlet for pumped liquid;
- providing a junction pipeline comprising a first
and a second end;
mechanically coupling said first end of said
junction pipeline to said inlet of said first pump
and mechanically coupling said second end of said
junction pipeline to said spent liquid outlet of
said spent liquid pipeline such that said inlet
for liquid to be pumped of said first pump is
connected to said spent liquid pipeline via said
junction pipeline;
said method being characterized in that said first pump
is a self-priming pump.
[0005] The first pump is a self-priming liquid pump.
Preferably, this first pump is a self-priming
centrifugal pump. That makes it possible to have high
pumping flow rates which is often required for raising
spent waters. A self-priming centrifugal pump is also
less costly than other types of self-priming pumps
which makes it possible to reduce the costs. Another
example of a first self-priming pump is a positive
displacement self-priming pump. Preferably, said first
pump is then a peristaltic pump or a lobe pump.
[0006] A self-priming pump is known by the one skilled
in the art. It is differentiated from load pumps as
described in FR2837244. A self-priming pump is equipped
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with an automatic mechanism which enables the pump to
be automatically primed. Examples of self-priming pumps
are wet priming centrifugal pumps and dry priming
centrifugal pumps. Commercial examples of self-priming
pumps are the CORNELL brand 'Redi-prime' and 'venturi-
prime' pumps, the Godwin brand 'dri-prime' pumps or
even the Gorman-Rupp brand 'priming assist' pumps. For
the wet priming centrifugal pumps, the volute of the
pump is surrounded by an outer jacket which serves as a
liquid tank. There is a passage between the volute and
the liquid tank which is used to create the vacuum in
the suction piping. For the dry priming centrifugal
pumps, the liquid centrifugal pump is twinned with a
vacuum pump which makes it possible to create the
vacuum in the suction piping, thus enabling the liquid
pump to be primed.
[0007] The priming of a pump for liquid is a concept
known to those skilled in the art. The priming is
necessary to enable the liquid to be pumped by a pump
for liquid. It describes the filling of a pump by the
liquid to be pumped after removal of air from the body
of the pump and in the upstream piping (or suction
duct) which should bring the liquid to be pumped to the
pump. A pump without automatic priming cannot on its
own discharge the air from the suction duct.
[0008] The pump of FR2837244 is not self-priming. In
fact, line 11 of page 12 reads as follows: the priming
of the pumps takes place automatically as soon as the
liquid/gas mixture reaches a sufficient density, by
virtue of degassing chambers, not represented, situated
behind the impellers. Thus, it is essential for the
liquid/gas mixture to reach a sufficient density for
the priming of the pump of FR2837244 which is not the
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case with the first self-priming pump of the invention.
By using the method of the invention, there is no need
for degassing chambers because the first pump is a
self-priming pump. Thus, the method of the invention is
simpler.
[0009] The first pump is self-priming. Priming is
therefore possible even if the first pump is located at
a higher level than the level of liquid to be pumped.
This is not possible with the pump of FR2837244 which
is a non self-priming dry bilge pump. This explains why
the pump of FR2837244 is housed in a bottom portion of
a tank to make it possible to create the conditions
necessary for the priming of the pump, namely that the
level of water in the suction manifold of the impeller
of the pump of FR2837244 is higher than the level at
which the centrifugal impeller of the pump is located.
In particular, this document teaches placing the pump
in the low part of said tank (that could also be called
dry dock), at the level of the inlet opening through
which the intake pipeline arrives and therefore the
liquid to be pumped. Thus, in normal conditions of use,
the priming of the pump is possible by virtue of the
weight exerted by the column of water upstream of the
pump. 'Normal conditions of use' should be understood
to mean conditions corresponding to the case where the
water flows from the intake pipeline to the tank by
gravity.
[00010] Since the priming of the first pump is possible
even if the latter is located at a higher level than
the level of liquid to be pumped, incorporating it in a
pumping area is simplified: the constraint on the
vertical positioning of the pumps of FR2837244 is
eliminated (the pumps of FR2837244 have to be located
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under the level of water to be pumped to enable them to
be primed). Furthermore, it is possible to position the
first pump of the invention on the surface of the
ground even if the spent liquid pipeline is underground
(which is generally the case). This also facilitates
the implementation of the method of the invention in a
pumping area; it is then no longer necessary to provide
and construct a tank or dry dock to house the pump or
pumps. There is therefore a significant reduction in
the cost because this civil engineering work is no
longer necessary (this tank can be eliminated which is
not mentioned in FR2837244 because the set which is
described therein does not comprise any self-priming
pump; the tank is therefore necessary). Also, the
maintenance of the pumps is easier when they are
incorporated in an 'above-ground' pumping area, because
it is more accessible if it is located on the surface
of the ground (compared to a configuration where the
pumps are located in a tank). The maintenance costs are
therefore also reduced with the method of the
invention. In particular, it is not necessary to
provide a ladder to descend to the bottom of such a
tank and it is not necessary to descend to the bottom
of a tank to inspect the condition of the pump or
pumps. In some places (for example very rocky places),
hollowing out such a tank can be particularly
complicated and costly.
[00011] By using a self-priming pump like the first
pump of the method of the invention, it is also
possible to position the pump further away from the
spent liquid outlet of the spent liquid pipeline
(intake pipeline of FR2837244). The pump of FR2837244
has to be positioned as close as possible to the inlet
opening into which the intake pipeline is introduced.
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This constraint is eliminated with the method of the
invention. This aspect also facilitates its
implementation in a pumping area.
[00012] The junction pipeline can consist of a single
part, for example a pipe. In another preferred version,
the junction pipeline comprises a number of parts, for
example several pipes.
[00013] The method of the invention has other
advantages. By virtue of the junction pipeline and the
coupling means, it is possible to link the inlet of the
first pump to the spent liquid outlet of the spent
liquid pipeline. This allows the spent liquid to pass
from said spent liquid outlet to the inlet of the first
pump without passing through a wet pit. This particular
feature is quite original and runs counter to the usual
practice which has been followed in the field of
pumping areas for many years.
[00014] A wet pit is known to those skilled in the art:
it describes a well in which spent liquid is stored
(such as spent waters) before being pumped to the
surface of the ground. Generally, a wet pit is
cylindrical with a diameter that is generally between
1.5 and 5 metres, and with a height (or depth) that is
generally between 2 and 8 metres. A wet pit can also
take the form of a hollow prism with square or
rectangular base.
[00015] The method of the invention makes it possible
to eliminate a wet pit from a pumping area. There are
various advantages that result from this. The
implementation of the method of the invention in a
pumping area and the construction of a pumping area
relying on the principles of the method of the
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invention are easier because it is not necessary to
provide and create this civil engineering work. The
costs linked to the implementation of the method of the
invention in a pumping area and the construction of a
pumping area relying on the method of the invention are
consequently reduced. The absence of wet pit in which
spent liquid such as spent waters stagnate also makes
it possible to reduce the putrid odours rising to the
surface. The comfort of adjoining landowners can
therefore be enhanced by virtue of the method of the
invention. Since there is no longer a need for a wet
pit in a pumping area, it is no longer necessary to
provide a ladder (or hatch covers) for access thereto.
This also generates a cost reduction. The absence of
wet pit also makes it possible to increase the number
of terrains likely to be able to accommodate a pumping
area: the constraints on the ground that has to
accommodate the pumping area are reduced. Along the
same lines, it is possible, by virtue of the method of
the invention, to provide for the construction of a
pumping area even in demanding places which is not
possible with a pumping area requiring a wet pit.
[00016] Preferably, said spent liquid pipeline is an
underground pipeline. Preferably, said underground
spent liquid pipeline is a pipeline for discharging
spent liquid from a well. Preferably, said well is a
pebble trap. Preferably, said first pump is controlled
as follows:
when a level of liquid to be pumped is hl or
greater, starting said first pump and imposing a
pumping speed v10 on it;
if said liquid level is greater than h2<hl but
less than or equal to hl, imposing said pumping
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speed v1 on said first pump if the latter is in
operation;
when said liquid level reaches h2<h1, imposing a
pumping speed v2<v1 on said first pump during a
time interval AT, such that said liquid level is
kept constant;
after said time interval AT, imposing a pumping
speed v3 on said first pump such that said liquid
level reaches a value h3<h2;
- when said liquid level reaches h3<h2, stopping the
first pump.
[00017] Preferably, the spent liquid pipeline has a
mean inclination of between 10 and 50 relative to a
horizontal plane such that said spent liquid inlet is
situated at a higher level relative to said spent
liquid outlet in a vertical direction. Preferably, the
spent liquid pipeline has a mean inclination of between
30 and 45 relative to a horizontal plane such that
said spent liquid inlet is situated at a higher level
relative to said spent liquid outlet in a vertical
direction. By imposing such inclinations on the spent
liquid pipeline (between 10 and 50 relative to a
horizontal plane, or more preferably between 30 and
45 relative to a horizontal plane), problems of
decantation of solid particles present in the liquid to
be pumped can be reduced, even avoided. When the spent
liquid pipeline is horizontal, there are risks of
decantation, notably when the pump or pumps is (are)
stopped. These decantation problems reduce the pumping
capacity and can, ultimately, block said spent liquid
pipeline subsequently preventing any liquid pumping. By
imposing an inclination of said spent liquid pipeline
that is greater than or equal to 10 , and
preferentially, greater than 25 , it is possible to
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reduce such risks and provide what the inventors call a
self-clearing of the pumping station. Imposing such an
inclination of said spent liquid pipeline also makes it
possible to increase the reliability of a liquid level
regulation.
[00018] Preferably, the method comprises a step of
positioning the first pump on the surface of the
ground. Then, said first pump is readily accessible,
facilitating maintenance. This preferred embodiment
also has the advantage of cancelling the need of an
underground dry dock where to place the first pump.
[00019] According to a second aspect, the invention
relates to a pumping station comprising:
- a spent liquid pipeline comprising a spent liquid
inlet and a spent liquid outlet, and configured in
such a way that liquid can flow (into it) from
said spent liquid inlet to said spent liquid
outlet by gravity,
- a pumping set for pumping said liquid from said
spent liquid pipeline and comprising:
= a first pump for pumping said liquid,
comprising an inlet for liquid to be pumped and
an outlet for pumped liquid;
= a junction pipeline mechanically coupled to
said inlet of said first pump;
= coupling means mechanically coupled to said
junction pipeline and suitable for mechanically
coupling said junction pipeline to said spent
liquid outlet of said spent liquid pipeline,
said pumping station being configured such that said
spent liquid pipeline is mechanically coupled
(preferably linked) to said junction pipeline by said
coupling means, allowing a flow of spent liquid from
the spent liquid inlet of said spent liquid pipeline to
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its spent liquid outlet then to said junction pipeline
and then to said inlet for liquid to be pumped of said
first pump when the latter is operating.
The pumping station of the invention is characterized
in that said first pump is a self-priming pump.
[00020] Examples of coupling means are: glue, weld,
soldered joint, a flange, a bend, a collar, or any
matching part making it possible to link a free end of
the junction pipeline to the spent liquid outlet of the
spent liquid pipeline. Other examples of coupling means
are nevertheless possible.
[00021] Generally, the advantages mentioned in relation
to the method according to the first aspect of the
invention apply also to the pumping station, mutatis
mutandis. In particular, the pumping station of the
invention is simpler to use and simpler to maintain.
Since the first pump is a self-priming pump, there is
no need to place it at the bottom of a tank or dry
dock. It can notably be placed on the surface which
simplifies the use and maintenance of the pumping
station. Since it is not necessary to provide a tank or
dry dock, the pumping station of the invention is also
less costly. This pumping station does not require the
presence of a wet pit because the first pump is
directly connected to the spent liquid outlet of the
spent liquid pipeline. The cost associated with the
pumping station can therefore also be reduced for this
reason, as was explained previously. The absence of wet
pit also makes it possible to reduce the quantity of
putrid odours. The incorporation of the pumping station
according to the invention in a pumping area is less
complex compared with existing pumping stations for the
following reasons. Neither a wet pit, nor a dry dock
for placing the pump(s) is required. For these reasons,
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incorporation of the pumping station of the invention
in a pumping area is also less expensive.
[00022] Preferably, the spent liquid pipeline has a
mean inclination of between 10 and 50 relative to a
horizontal plane such that said spent liquid inlet is
situated at a higher level relative to said spent
liquid outlet in a vertical direction. Preferably, the
spent liquid pipeline has a mean inclination of between
30 and 45 relative to a horizontal plane such that
said spent liquid inlet is situated at a higher level
relative to said spent liquid outlet in a vertical
direction.
[00023] By imposing such inclinations on the spent
liquid pipeline, problems of decantation of solid
particles present in the liquid to be pumped can be
reduced, even avoided. When the spent liquid pipeline
is horizontal, there are risks of decantation, notably
when the pump or pumps is (are) stopped. These
decantation problems reduce the pumping capacity and
can, ultimately, block said spent liquid pipeline
subsequently preventing any liquid pumping. By imposing
an inclination of said spent liquid pipeline that is
greater than or equal to 10 , and preferentially,
greater than 25 , it is possible to reduce such risks
and provide what the inventors call a self-clearing of
the pumping station. Imposing such an inclination of
said spent liquid pipeline also makes it possible to
increase the reliability of a liquid level regulation.
Mean inclination of the spent liquid pipeline is
generally determined as follows. The spent liquid
pipeline generally has a cylinder shape. It is then
possible to define a main axis, for instance an axis of
revolution. Means inclination of the spent liquid
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pipeline is then defined as the inclination of this
main axis relative to a local horizontal plane.
[00024] Preferably, said spent liquid pipeline is
located underground and the pump or pumps is/are
located on the surface of the ground. Access to the
pump or pumps is then easier while having a pumping
station for pumping waters flowing underground.
[00025] Preferably, the pumping set of the pumping
satation comprises:
- a self-priming second pump for pumping said
liquid, comprising an inlet for liquid to be
pumped and an outlet for pumped liquid;
a junction pipeline mechanically coupled to said
inlet of said second pump;
- a coupling means mechanically coupled to said
junction pipeline to mechanically couple said
junction pipeline to said spent liquid outlet of
said spent liquid pipeline.
[00026] In this preferred embodiment, the pumping set
therefore comprises two self-priming pumps. Thus, the
maximum pumping capacity, that is to say the maximum
volume of liquid that can be pumped per unit of time is
greater by using the same type of self-priming pump.
This is particularly useful when large quantities of
liquid have to be pumped or when liquid flowing at a
high flow rate has to be pumped. This preferred
embodiment presents other advantages. In particular,
the pumping capacity of the pumping set is assured even
if a pump is stopped. One of the two pumps can be
stopped for different reasons such as, for example:
maintenance servicing of said pump requiring its
shutdown; shutdown because of failure of said pump or
of associated auxiliary services (for example, power
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supply outage for said pump). Using two pumps rather
than just one also makes it possible to increase the
life of the pumps because it is possible to operate
them alternately, which reduces the stresses imposed on
the pumps. To this end, the pumping set of the
invention preferentially comprises a regulation system
for alternating the operation of the first and second
pumps. Having the first and second pumps operate
alternately also makes it possible for them to be worn
in a noticeably similar manner (they ultimately run for
substantially equivalent times) which also facilitates
the management of maintenance of the pumps. When the
first and second pumps are made to operate alternately,
there are significant pump rotation speed peaks or
gradients. These speed peaks make it possible to have
sufficient speeds (preferentially greater than 0.6 m/s)
in the discharge piping (that is to say the piping
connected to the outlets for pumped liquid of the
pumps) to carry off sand and other solid particles.
Thus, the alternate operation of the pumps allows for
cleaning of the piping.
[00027] Preferentially, the junction pipeline has a
length of between two and nine metres. Also
preferentially, it has a length of between four and six
metres. Even more preferentially, it has a length of
seven metres. By using a length greater than or equal
to two metres for the junction pipeline, it is possible
to reduce the risks associated with cavitation, even
eliminate them. By using a length greater than or equal
to two metres for the junction pipeline, it is also
possible to remotely site the pump or pumps at fairly
great distances from the spent liquid outlet of the
spent liquid pipeline. This makes it possible to place
the pump or pumps at readily accessible places making
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maintenance of the pumping set even easier. In
particular, with such lengths for the junction
pipeline, it is generally possible to place the pump or
pumps on the surface while providing a connection
between them and at the place where the effluents
arrive. Preferably, the junction pipeline is vertical.
[00028] Preferably, the pumping set
comprises a
regulation system for controlling the operation of said
first pump as follows:
- when a level of liquid to be pumped is h1 or
greater, said regulation system is suitable for
starting said first pump and for imposing a
pumping speed v1 on it;
when said liquid level is greater than h2<h1 but
less than or equal to h1, said regulation system
is suitable for imposing said pumping speed v1 on
said first pump when it is operating;
when said liquid level reaches h2<h1, said
regulation system is suitable for imposing a
pumping speed v2 on said first pump such that
v2<v1 during a time interval AT such that said
liquid level is kept constant;
after said time interval AT, said regulation
system is suitable for imposing a pumping speed v3
on said first pump such that said liquid level
reaches a value h3<h2;
when said liquid level reaches h3<h2, said
regulation system is suitable for stopping the
first pump.
With this preferred embodiment, it is possible to
provide self-clearing or self-cleaning of said spent
liquid pipeline, in particular when the latter is
inclined relative to a horizontal plane such that the
spent liquid inlet is at a higher level relative to the
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spent liquid outlet in a vertical direction. By virtue
of this preferred embodiment, it is in fact possible to
remove floats and decantation residues from said spent
liquid pipeline. The stopping of the first pump at the
level h3 makes it possible to avoid introducing air
during the pumping which is damaging to the pumps both
mechanically and hydraulically (because air pockets can
form in the discharge duct), which will result in the
formation of water hammer (pressure impact upon the
stopping of the pumps). Preferably, v1 and v3 are equal
to the maximum pumping speed of said first pump.
[00029] Preferably, the pumping set of the pumping
station comprises a bypass pipeline coupled to said
first pump to allow for cleaning of a region situated
in said spent liquid pipeline by diverting at least a
portion of liquid pumped by said first pump to said
region.
[00030] There are various advantages of using such a
bypass pipeline. Said bypass pipeline can first of all
be used to discharge air when the first pump is being
primed. Also, said bypass pipeline can be used to clean
an internal region of the spent liquid pipeline by
placing one of its ends in said region; the cleaning is
ensured by the diversion of at least a portion of
liquid pumped by the first pump through said bypass
pipeline. Finally, when the first pump is stopped, the
bypass pipeline can be opened by a user to drain the
entire discharge column in order, for example, to carry
out a maintenance intervention on the discharge duct
(which can sometimes cover several kilometres). The
discharge duct is positioned downstream of the first
pump (that is to say connected to the outlet for pumped
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liquid of the first pump) and is used to discharge the
pumped liquid.
[00031] Preferably, the pumping set of the pumping
station comprises a level sensor for measuring a liquid
level. Preferably, this liquid level is a level of
liquid in the spent liquid pipeline. In another
preferred variant, the liquid level could be a level of
liquid in a well (for example a pebble trap) located
upstream of the spent liquid pipeline. By using such a
level sensor, it is possible to regulate the pump or
pumps by knowing such a level and to provide closed
loop regulation. Preferably, said level sensor is a
bubbling level sensor comprising a bubbling tube.
[00032] By controlling the level of liquid to be
pumped, for example in the spent liquid pipeline, it is
possible to avoid pumping air by stopping the operation
of any self-priming pump when said level becomes lower
than a certain low threshold which is to be determined.
Controlling a level of liquid in the spent liquid
pipeline allows further improving self-cleaning and
self-clearing of the pumping station.
[00033] Preferably, the pumping station comprises at
least two spent liquid pipelines. Said first pump can
then be connected to each of the spent liquid outlets
of said spent liquid pipelines. In an embodiment
corresponding to the case where there are a first and a
second self-priming pumps and two spent liquid
pipelines, it is preferable to connect each of said
first and one second pumps to a spent liquid pipeline.
[00034] The rate of flow of liquid in the spent liquid
pipeline is preferably greater than or equal to
0.4 m/s, even more preferably, greater than or equal to
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0.6 m/s and even more preferably, greater than or equal
to 1 m/s. With these three preferred variants, the
risks of decantation in the spent liquid pipeline are
reduced and all the more so as said rate of liquid flow
increases. Such liquid flow rates can be obtained in
the spent liquid pipeline by imposing on it a certain
inclination relative to a horizontal plane, see above.
Generally, an inclination greater than or equal to 30
relative to a horizontal plane has to be imposed to
ensure that the rate of liquid flow in the spent liquid
pipeline is at least equal to 0.4 m/s.
[00035] According to a third aspect, the invention
relates to a pumping area comprising a pumping station
as described previously, and a well connected with the
spent liquid pipeline via its spent liquid inlet. This
pumping area can comprise any preferred embodiment of
the pumping station of the second aspect of the
invention.
[00036] Generally, the advantages mentioned in relation
to the pumping method of the first aspect of the
invention and the pumping station of the second aspect
of the invention apply also to the pumping area,
mutatis mutandis. In particular, the pumping area of
the invention is simpler to use and simpler to
maintain. Since the first pump is a self-priming pump,
it is not necessary to place it at the bottom of a tank
or dry dock. It can in particular be placed on the
surface which facilitates the use and maintenance of
the pumping area. Since it is not necessary to provide
a tank or dry dock, the pumping area of the invention
is also less costly. This pumping area does not require
the presence of a wet pit because the first pump is
directly connected to the spent liquid outlet of the
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spent liquid pipeline. The cost associated with the
pumping area can therefore also be reduced for this
reason, as it has been explained previously. The
absence of a wet pit also makes it possible to reduce
the quantity of putrid odours. The advantages linked to
the preferred embodiments of the pumping method of the
first aspect of the invention and of the pumping
station of the second aspect of the invention also
apply for pumping areas comprising such preferred
embodiments.
[00037] With the pumping station or the pumping area of
the invention, a screening basket is no longer
necessary. In preferred variants of the pumping station
or of the pumping area, it would nevertheless be
possible to incorporate one. A screening basket is
known to those skilled in the art. It makes it possible
to retain and therefore filter objects floating on the
surface of the liquid to be pumped, for example pieces
of wood.
[00038] For the third aspects of the invention, said
spent liquid pipeline can be connected to a recovery
pipeline without using a well such as a pebble trap.
Liquid can therefore pass from said recovery pipeline
to said spent liquid pipeline without passing through
such a well. The associated costs are then all the more
reduced. Thus, according to this preferred variant, the
invention relates to a configuration comprising the
pumping station of the invention, a recovery pipeline
and coupling means for coupling said spent liquid
pipeline and said recovery pipeline.
Brief description of the figures
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[00039] These aspects and other aspects of the
invention will be clarified in the detailed description
of particular embodiments of the invention, reference
being made to the drawings of the figures, in which:
Fig. 1 shows an example of pumping station of the
invention incorporated in a pumping area;
Fig. 2 shows a possible example of configuration for
the spent liquid pipeline;
Fig. 3 shows a preferred embodiment of junction
pipelines when the pumping set comprises two
pumps;
Fig. 4 shows an example of operating mode of pumps
when the pumping station comprises two pumps;
Fig. 5 shows a part of a preferred embodiment of the
pumping station of the invention;
Fig. 6 shows a part of a preferred embodiment of the
pumping station of the invention;
Fig. 7 shows a part of a preferred embodiment of the
pumping station of the invention;
Fig. 8 shows a part of a preferred embodiment of the
pumping station of the invention;
Fig. 9 shows a part of a preferred embodiment of the
pumping station of the invention;
Fig. 10 shows an example of a spent liquid pipeline
having a non-zero mean inclination relative to
a horizontal plane;
Fig. 11 shows an example of pumping station of the
invention incorporated in a pumping area;
Fig. 12 shows a preferred embodiment of a well of a
pumping area according to the invention.
The drawings of the figures are neither to scale nor in
proportion. Generally, similar elements are denoted by
similar references in the figures.
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Detailed description of embodiments of the invention
[00040] Figure 1 shows a preferred version of the
pumping station 3 according to the invention,
incorporated in a pumping area 8. This pumping area 8
comprises a well 4 such as a pebble trap. A pebble trap
is known to those skilled in the art. It is generally a
cylindrical cavity with a diameter generally between
50 cm and 2 metres (with a preferred value of 1 metre)
and with a height that is generally between 50 cm and 9
metres (with a preferred value of 5 metres). Spent
liquid (for example spent waters) is generally brought
to a pebble trap 4 via one or more recovery pipeline(s)
40. Preferably, the bottom of the pebble trap 4 is
situated approximately 1 metre below the intake of said
recovery pipeline 40 situated at the level of said
pebble trap 4. Spent liquid can convey stones, pebbles
or particles with a density that is higher than the
liquid transporting them. When this spent liquid
reaches the pebble trap 4, these higher density
particles have a tendency to fall to the bottom by
gravity. The function of the pebble trap 4 is therefore
to eliminate the high density particles from the spent
liquid. Generally, an overflow pipeline 30 is present
to allow liquid to be discharged from the well 4 should
it overflow.
[00041] A spent liquid pipeline 10 makes it possible to
discharge liquid from the well 4. Preferably, this
spent liquid pipeline 10 is a spent water pipeline. It
comprises a spent liquid inlet 10in which communicates
with the interior of the well 4 and a spent liquid
outlet 10out. The spent liquid pipeline 10 is
configured in such a way that liquid can flow from the
spent liquid inlet 10in to the spent liquid outlet
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this is possible since the spent liquid outlet 10out is
lower than the spent liquid inlet 10in. This is not
however necessary. Figure 2 shows a case where the
spent liquid pipeline 10 is configured in such a way
that liquid can flow from the spent liquid inlet 10in
to the spent liquid outlet 10out by gravity without in
any way requiring the spent liquid outlet 10out to be
lower than the spent liquid inlet 10in. In this case,
liquid will pass from the spent liquid inlet 10in to
the spent liquid outlet 10out through a communicating
vessel. The arrows indicate the direction of flow of
the liquid in the configuration shown in figure 2. The
force of gravity which is exerted on the liquid present
in the well 4 forces it to flow according to the arrows
shown in figure 2. This spent liquid pipeline 10 is
therefore equally configured to allow a flow of liquid
from the spent liquid inlet 10in to the spent liquid
outlet 10out by gravity.
[00042] The pumping station 3 of the invention
comprises a pumping set 1 comprising a first self-
priming pump 501. The latter comprises an inlet 501in
for liquid to be pumped and an outlet 501out for pumped
liquid. The pumping set 1 of the invention also
comprises a junction pipeline 15 comprising a first 15a
and a second 15b ends. The junction pipeline 15 is
mechanically coupled (preferably fixed) to the inlet
501in for liquid to be pumped of the first pump 501 by
its first end 15a. Coupling means 20 makes it possible
to mechanically couple (or link) said junction pipeline
15 to the spent liquid outlet 10out of the spent liquid
pipeline 10 by its second end 15b. Examples of coupling
means 20 are: glue, soldering, a flange, a bend
(example represented in Figure 1), a collar, or any
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matching part making it possible to link a free end of
the junction pipeline 15 to the spent liquid outlet
10out of the spent liquid pipeline 10. By virtue of
this coupling means 20, liquid can pass from the spent
liquid outlet 10out of the spent liquid pipeline 10 to
the inlet 501in for liquid to be pumped of the first
pump 501 without passing through a wet pit. Preferably,
the junction pipeline 15 has a length of between two
and nine metres. An example of internal diameter for
the junction pipeline 15 is 150 mm. Other internal
diameter values such as 80 mm to 300 mm could
nevertheless be chosen.
[00043] As is illustrated in Figure 1, the pumping area
8 preferably comprises a stabilized 85 to support the
spent liquid outlet 10out of the spent liquid pipeline
10. Preferably, this stabilized 85 is made of concrete.
Generally, the outlet 501out for pumped liquid of the
first pump 501 is linked to a discharge pipeline 45
making it possible to discharge the pumped liquid.
Preferably, this discharge pipeline 45 is partly
underground. As is illustrated in Figure 1, the first
pump 501 is preferably housed in an enclosure 80 such
as a hut.
[00044] In a preferred embodiment, the pumping set 1 of
the pumping station 3 comprises a first 501 and a
second 502 pump. A junction pipeline 15 makes it
possible to link the inlet of the second pump 502 to
the spent liquid outlet 10out of the spent liquid
pipeline 10. This can be the same junction pipeline 15
as that used to link the inlet 501in of the first pump
501 to the spent liquid outlet 10out of the spent
liquid pipeline 10. In another preferred embodiment,
each of the first 501 and second 502 pumps is rather
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linked to the spent liquid outlet 10out of the spent
liquid pipeline 10 by a different junction pipeline
(151, 152): see figure 3. Preferably, these two
junction pipelines (151, 152) are then housed in one
and the same external pipe 16. Coupling means 20 such
as a bend for example makes it possible to link each
junction pipeline (151, 152) to the spent liquid outlet
10out of the spent liquid pipeline 10. Either a single
coupling means 20 can be used to make these two
connections or two different coupling means can be used
to link the two junction pipelines (151, 152) to the
spent liquid outlet 10out of the spent liquid pipeline
10.
[00045] Preferably, the pumping set 1 (and so the
pumping station 3) comprises a regulation system 70 (a
programmable logic controller for example) to alternate
the operation of the first 501 and second 502 self-
priming pumps when said pumping set 1 comprises two
such pumps (501, 502). This mode of operation is
illustrated in figure 4. This figure shows a time trend
of the state 100 of the first and second pumps (501,
502) according to this preferred mode of operation. The
state of the first pump 501 (respectively second pump
502) is plotted by dotted lines (respectively by solid
lines). During one alternation period 5f, the first
pump 501 is in operation (state 100 at level 1) while
the second pump 502 is stopped (state 100 at level 0).
Then, the reverse applies.
[00046] In a preferred embodiment, the pumping set 1 of
the pumping station 3 comprises a regulation system 70
(a programmable logic controller for example) to impose
the following operation on the first pump 501 (it can
be the same regulation system 70 as that described
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previously or another). When a level of liquid to be
pumped is hl or greater, said regulation system 70
starts said first pump 501 and imposes a pumping speed
vi on it. The first pump 501 will therefore be
triggered when the liquid level is hl and will then
operate at the pumping speed (or speed of rotation of a
centrifugal pump) vi, the time for the first pump 501
to be primed and then to provoke a reduction in the
liquid level to h2<hl. Preferably, this pumping speed
vi represents the maximum pumping speed (or maximum
flow rate) of the first pump 501. An example of speed
vi is 1500 rpm. The time for said liquid level to
change from hl to h2 depends on the one hand on the
priming time (which depends on the speed of the first
pump 501) and on the liquid intake flow rate at that
moment. Preferably, said liquid level represents the
level of liquid in the well 4 (which is preferably a
pebble trap). This is illustrated in Figure 5 which
shows two two-dimensional cross sections of the pumping
set of the invention according to a preferred
embodiment in combination with a spent liquid pipeline
10 and a well 4. Preferably, said liquid level is
measured using a level sensor such as a bubbling sensor
(example illustrated in Figure 5). In this case, the
level sensor comprises a bubbling tube 61, the end 61a
of which is preferably situated in proximity to the
spent liquid outlet 10out in the spent liquid pipeline
10. Preferably, a zero liquid level then corresponds to
a liquid level which is located at the same height as
said end 61a of the bubbling tube 61. A positive liquid
level then corresponds to a liquid level situated above
said end 61a of the bubbling tube 61; in other words,
and from a general point of view, a zero liquid level
therefore corresponds to a liquid level located at the
same height as that at which the level is measured by
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the level sensor. The dimensions mentioned in Figure 5
and in the subsequent figures are purely illustrative
for certain exemplary preferred embodiments. Other
dimensions can be used.
[00047] When said liquid level reaches h2<h1 (see
Figure 6), the regulation system 70 imposes a speed on
the first pump 501 such that said liquid level is kept
constant (therefore at h2) during a time interval AT,
to within the tolerance of measurement errors and with
a liquid level indication tolerance which is preferably
between +/- 5%. Preferably, AT is five minutes. The
pumping speed variation of the first pump 501 is
preferably made possible by virtue of the use of one or
more variable frequency drive(s). Preferably, such a
variable frequency drive is installed in a control unit
on the surface of the ground. During AT, the flow rate
of the first pump 501 is equal to the effluent intake
flow rate.
[00048] Once the time interval AT has ended, the
regulation system 70 imposes a pumping speed v3 on the
first pump 501. Preferably, v3 is equal to the maximum
pumping speed of the first pump 501. This will enable
the first pump 501 to exceed the effluent intake flow
rate and to empty an inclined spent liquid pipeline 10
as illustrated in Figure 7 to a level h3. When said
liquid level reaches h3, the regulation system 70 stops
the first pump 501 (h3=0 in Figure 7). Subsequently,
the spent liquid pipeline 10 will be filled once again
to the level h1 following the intake of effluent or
liquid.
[00049] The sequence of operations of the first pump
501 imposed by the regulation system 70 which has just
been described in relation to Figures 5 to 7 allows for
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the self-clearing of an inclined spent liquid pipeline
by carrying away floats and decantations. The
stopping of the first pump 501 at the level h3 makes it
possible to avoid the introduction of air during the
5 pumping, which is damaging to the pumps. The pumping of
liquid and air initiates significant vibrations of the
pump and can result in premature mechanical breakdowns
of the mechanical bearings and packings. At the end of
the sequence of operations of the first pump 501, it
10 was stated that the spent liquid pipeline 10 will be
filled once again to the level h1 following the intake
of effluent or liquid. It is then possible to repeat
this sequence of operations. In another preferred
embodiment, this sequence will be imposed rather on a
second pump 502 when the pumping set 1 comprises at
least two pumps. The latter will then complete the same
cycle of operations as described previously. This makes
it possible to have the first 501 and second 502 pumps
wear in the same way. This makes it easier to schedule
pump maintenance.
[00050] Preferably, the following procedure is chosen
for monitoring the malfunctioning of the first 501 and
second 502 pumps when the pumping set 1 of the pumping
station 3 comprises two such pumps. This monitoring
procedure can be applied by a regulation system 70, for
example, the same as that described previously in
relation to Figures 5 to 7. In this procedure, there
are two additional thresholds for the liquid level,
which preferably represents a level of liquid in a well
4 upstream of the spent liquid pipeline 10 (see above):
h4 and h5. The threshold h4 is such that h4>h1 in an
upward vertical direction. Preferably, h4 is situated
at a vertical distance from h1 of between 20 and 80 cm.
Even more preferably, h4 = h1 + 40 cm. To illustrate
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the monitoring procedure for which the associated
liquid levels are shown in Figures 8 and 9, it is
assumed that the first pump 501 is in operation to pump
liquid but that the second pump 502 is stopped (the
monitoring procedure nevertheless applies in the
contrary case, mutatis mutandis). When a liquid level
reaches h4, the second pump 502 is started, whereas the
first pump 501 is stopped. This procedure is followed
because, if a level h4 is reached, that means that the
first pump 501 is not giving its nominal flow rate.
Simultaneously with the stopping of the first pump 501,
an alarm is triggered. Subsequently, the second pump
502 is the only one to operate pending the intervention
of a maintenance department which will have to
intervene on the first pump 501 to repair it. It may be
that the first 501 and second 502 pumps are both
damaged. In this case, the liquid level will continue
to rise up to a high general alarm level called h5.
Preferably, this level h5 corresponds to the overflow
level of a well 4. When the liquid reaches this
overflow level, the liquid can preferably flow through
an overflow pipeline 30, see for example in Figure 9.
Preferably, an alarm is generated when the liquid level
reaches h5. Thus, the users can be alerted thereof.
Preferably, the following values are used for hl to h5:
h1=80%, h2=40%, h3=0%, h4=90%, and h5=100%.
[00051] Preferably, the pumping set 1 (and so the
pumping station 3) comprises a bypass pipeline 50 (see
Figures 5 to 9). The bypass pipeline 50 can, for
example, be a DN50, DN65 or DN80 tube (DN denotes the
nominal diameter which is a concept known to those
skilled in the art). The choice of a particular type
will depend on the size and the pumping power of the
first pump 501. This bypass pipeline 50 is mechanically
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coupled to the first pump 501. More specifically, the
bypass pipeline 50 is connected to the pumped liquid
outlet 501out of the first pump 501. In a preferred
embodiment comprising two pumps, the bypass pipeline 50
is preferentially connected to both pumps: in this
preferred variant, there is therefore a bypass pipeline
50 for both pumps. It is, however, possible to provide
two bypass pipelines 50, one for each pump (501, 502).
[00052] Hereinafter in the description of the preferred
embodiment comprising a bypass pipeline 50, it will be
assumed that there is only a single pump, called first
pump 501. The elements described below nevertheless
apply to a preferred embodiment comprising two pumps
(501, 502). Preferably, a valve is inserted between the
outlet for pumped liquid 501out of the first pump 501
and the bypass pipeline 50. The latter can have three
functions.
[00053] The bypass pipeline 50 can be used to discharge
air when the first self-priming pump 501 is priming. In
practice, when the first pump 501 creates the vacuum in
the suction piping (that is to say in particular the
junction pipeline 15) for the atmospheric pressure to
be able to then push the liquid to be pumped into the
suction piping, the sucked air has to be discharged.
The bypass pipeline 50 can be used to discharge this
sucked air during the priming.
[00054] Also, the bypass pipeline 50 can be used to
clean a part of the liquid circuit, for example an
internal region of the spent liquid pipeline 10. In
normal use of the first pump 501, the valve situated
between the outlet for pumped liquid 501out of the
first pump 501 and the bypass pipeline 50 is closed,
preventing the passage of liquid into this pipeline.
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When the user wants, he or she can open this valve
while the first pump 501 is operating. At least a
portion of pumped liquid which is under pressure is
outgoing from the outlet for pumped liquid 501out is
then diverted to this bypass pipeline 50 and is driven
to the place where the end of the bypass pipeline 50
which is not connected to the first pump 501 is
located. This point corresponds, for example, to an
internal region of the spent liquid pipeline 10, in
proximity to the spent liquid outlet 10out (that is to
say, in a region situated at a distance less than 35 cm
from said spent liquid outlet 10out along the main axis
of the spent liquid pipeline 10). Sand and decanted
particles can therefore be returned to suspension while
continuing to pump. This function is very effective
since it takes its feed immediately at the discharge
(or at the outlet) of the pumps (at the point where the
pressure is maximum). The valve situated between the
outlet for pumped liquid 501out of the first pump 501
and the bypass pipeline 50 can be manual or automatic,
electric for example. An electric automatic valve can
be opened via a regulation system 70 or a control
system such as a programmable logic controller for
example. Such a programmable logic controller can be
housed in the electrical cabinet which is located on
the surface of the ground, in proximity to the pump or
pumps (501, 502). Preferably, the valve is open two
minutes every hour.
[00055] Finally, when the pump or pumps is/are stopped,
the bypass pipeline 50 can be opened (via the valve
described above for example) by the user to drain the
entire discharge column (located downstream of the
outlet for pumped liquid 501 of the pumps) in order,
for example, to carry out a maintenance intervention on
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the discharge duct (which can sometimes be several
kilometres).
[00056] Preferably, the pumping set 1 (and so the
pumping station 3) of the invention comprises a
discharge non-return valve between the outlet for
pumped liquid 501 of the pump or pumps and the
discharge pipeline(s) through which the pumped liquid
is discharged. Such a valve makes it possible to avoid,
on the one hand, water hammer, and, on the other hand,
having the discharge column empty when the pump or
pumps is/are stopped.
[00057] Preferably, the pumping set 1 (and so the
pumping station 3) of the invention comprises an air
venting valve between the pump or pumps (501, 502) and
said discharge non-return valve. This air venting valve
is closed automatically when the pump or pumps (501,
502) is/are primed by virtue of the pressure that the
pumped liquid then exerts at this level.
[00058] Preferably, the end 50a of the bypass pipeline
50 which is not connected to an outlet for pumped
liquid 501out of a pump is immersed in a bottom part of
the spent liquid pipeline 10 which generally comprises
liquid: see for example Figures 5 to 9. This makes it
possible to avoid the unpriming of the pump or pumps
once stopped. In practice, since this piping is
immersed, air cannot reenter into it. Also, the
discharge non-return valve also prevents the ingress of
air into the piping.
[00059] Preferably, the pumping set 1 (and so the
pumping station 3) comprises a level sensor for
measuring a liquid level. Preferably, this liquid level
represents a level of liquid in the spent liquid
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pipeline 10. It can also, in another preferred variant,
be a level of liquid in a well 4 (for example a pebble
trap) upstream of the spent liquid pipeline 10. It is
then possible to regulate the pump or pumps by knowing
such a level and applying a closed loop regulation.
Preferably, said level sensor is a bubbling level
sensor comprising a bubbling tube 61. This type of
sensor is known to those skilled in the art.
Preferably, the bubbling tube 61 is a DN25 pipe.
Preferably, two level sensors such as two bubbling
sensors are used in order to increase the reliability
of the liquid level measurement. Compressed air is
injected into the bubbling tube or tubes 61 (for
example at a rate of one bubble per second) by means of
a bubble-maker which is preferably situated on the
surface of the ground, for example inside a hut housing
the pump or pumps (501, 502). One end of the bubbling
tube(s) 61 is preferably positioned in the spent liquid
pipeline 10 as is illustrated in Figures 5 to 9,
preferably at a distance less than 35 cm from the spent
liquid outlet 10out of said spent liquid pipeline 10.
This distance is preferably measured along the main
axis of the spent liquid pipeline 10. When said spent
liquid pipeline 10 is in the form of a hollow cylinder,
this main axis corresponds to the axis of revolution of
said hollow cylinder. Preferably, the bubbling tube(s)
61 is/are terminated by bubbling bells at the end
located in the spent liquid pipeline 10.
[00060] The spent liquid pipeline 10 of the pumping
station 3 of the invention generally takes the form of
a hollow cylinder. Preferably, the spent liquid
pipeline 10 is linked to a well 4 such as a pebble trap
(see Figure 1). In another preferred embodiment, the
spent liquid pipeline 10 is directly linked to a
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recovery pipeline 40 (see figure 11). In this case, the
use of a well 4 such as a pebble trap is not necessary.
The inventors therefore also propose the following
original set: the pumping station 3 according to the
invention, and one or more recovery pipelines 40, such
that the spent liquid pipeline 10 of the pumping
station 3 is directly linked to the recovery
pipeline(s) 40. Then, liquid can flow directly from the
recovery pipeline(s) 40 to the first pump 501 without
passing by a well (4) (pebble trap for instance) or by
a wet pit.
[00061] Preferably, the spent liquid pipeline 10 has a
mean inclination 11 of between 10 and 50 (with an
even more preferred value of 45 ) relative to a
horizontal plane such that said spent liquid inlet 10in
is situated at a greater (or higher) level relative to
the spent liquid outlet 10out in a vertical direction.
This is illustrated in Figure 10 for a preferred
embodiment in which the spent liquid pipeline 10 takes
the form of a hollow cylinder. In such a case, the
corresponding axis of revolution (shown in broken lines
in Figure 10) has an inclination 11 of between 10 and
50 (with an even more preferred value of 45 ) relative
to a horizontal plane in this preferred embodiment. In
Figures 5 to 9, the spent liquid pipeline 10 has a mean
inclination 11 of 30 relative to a horizontal plane.
[00062] Preferably, the spent liquid pipeline 10 is
located underground and makes it possible to pour water
by gravity from a well 4 (pebble trap for example).
Preferably, the pump(s) is/are located on the surface
which means that they can be easily accessed, which
makes their maintenance easier. These preferred
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variants are illustrated in Figure 1 in which the
reference sign 2 represents the ground.
[00063] Preferably, when the pumping station 3
comprises a first 501 and a second 502 pump, they are
suitable for operating alternately with an alternation
period 5f of between four and six minutes, including a
more preferred value of five minutes. To this end, the
pumping station 3 preferentially comprises a regulation
system 70 as described previously, making it possible
to control said first 501 and a second 502 pump in this
way.
[00064] Preferably, the pumping station 3 comprises a
bypass pipeline 50. This bypass pipeline 50 is linked
to the first pump 501 by one of its ends. The other end
of the bypass pipeline 50 is preferably situated in the
spent liquid pipeline 10, preferably at a distance less
than 35 cm from the spent liquid outlet 10out. This
distance is preferably measured along the main axis of
the spent liquid pipeline 10. When the spent liquid
pipeline 10 is in the form of a hollow cylinder, its
main axis corresponds to the axis of revolution of the
hollow cylinder (see dashed inclined line of figure
10).
[00065] Preferably, the pumping station 3 comprises a
level sensor for measuring a liquid level. Preferably,
this liquid level is the level of liquid in a well 4
such as a pebble trap to which the spent liquid inlet
10in of the spent liquid pipeline 10 is linked.
Preferably, this level sensor is a bubbling level
sensor. In this preferred variant, the bubbling tube 61
is preferably positioned in the spent liquid pipeline
10 in such a way that one of its ends is situated in
proximity to the spent liquid outlet 10out of the spent
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liquid pipeline 10, for example at less than 35 cm from
said spent liquid outlet 10out. This distance is
preferably measured along the main axis of the spent
liquid pipeline 10. When the spent liquid pipeline 10
is in the form of a hollow cylinder, its main axis
corresponds to the axis of revolution of the hollow
cylinder (see dashed inclined line of figure 10).
[00066] According to another aspect, the invention
relates to a pumping area 8 comprising a pumping
station 3 as described previously. This pumping area 8
can comprise any preferred embodiment of the pumping
station 3 described previously. An exemplary pumping
area 8 is illustrated in Figure 1. In another preferred
example, the pumping area 8 does not comprise a well 4
such as a pebble trap (see figure 11). In this last
case, the spent liquid pipeline 10 is connected
directly to the recovery pipeline 40. This makes it
possible to reduce the bulk and the manufacturing
costs. Such a pumping area 8 is also simpler to
construct and can be constructed in more different
places because there is no need to provide the space
for such a well 4.
[00067] When the pumping area 8 comprises a well 4, the
inventors propose the following preferred embodiment.
The inventors propose that the bottom surface 4b of the
well 4 is inclined with respect to a horizontal plane
(see figure 12). Preferably, the mean inclination or
slope of the bottom surface 4b of the well is then
comprised between 10 and 50 , with a preferred value
equal to 30 . This preferred embodiment is preferably
used when the well 4 is a manhole. This preferred
embodiment allows an even better self cleaning and
clearing of the pumping area 8.
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[00068] The inventors also propose, according to
another preferred embodiment, to position the spent
liquid pipeline 10 such that its spent liquid inlet 10in
is located at the bottom of the well 4 that is
preferably a manhole in this case (see figure 12). This
preferred embodiment further allows a better self
cleaning and clearing of the well 4, and so of the
pumping area 8. When this preferred embodiment is used,
the well 4 is preferably a manhole.
[00069] The invention also relates to a method for
pumping liquid from a spent liquid pipeline 10 as
described previously. The inventors
propose
mechanically coupling (or fixing, linking), for example
using glue, soldering or a collar, a junction pipeline
15 between the spent liquid outlet 10out of said spent
liquid pipeline 10 and the inlet for liquid to be
pumped 501in of a first self-priming pump 501. This
makes it possible to form a passage for liquid to be
pumped from the spent liquid pipeline 10 to the inlet
for liquid to be pumped 501in of the first pump 501
without having to pass through a wet pit.
[00070] The preferred embodiments described in relation
to the pumping station 3 of the invention apply for the
method of the invention, mutatis mutandis. This means
that the method of the invention enjoys the same
advantages. Thus, it is, for example, possible to link
a first 501 and a second 502 self-priming pump to the
spent liquid outlet 10out of a spent liquid pipeline 10
by using one or more junction pipeline(s) (15; 151,
152).
[00071] The present invention has been described in
relation to specific embodiments, which have a purely
illustrative value and should not be considered to be
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limiting. Generally, it will appear evident to a person
skilled in the art that the present invention is not
limited to the examples illustrated and/or described
above. The presence of reference numbers in the
drawings cannot be considered to be limiting, including
when these numbers are indicated in the claims. The use
of the verbs "comprise", "include" or any other
variant, and their conjugations, cannot in any way
preclude the presence of elements other than those
mentioned. The use of the indefinite article "a", "an",
or of the definite article "the", to introduce an
element does not preclude the presence of a plurality
of these elements.
[00072] The invention can also be described as follows.
Method for pumping liquid from a spent liquid pipeline
and comprising the steps of: providing a first pump,
providing a junction pipeline, mechanically coupling
said junction pipeline to said first pump and to said
spent liquid pipeline for allowing liquid to flow from
said spent liquid pipeline to said first pump. The
method is characterized in that said first pump 501 is
a self-priming pump.
