[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 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 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 ^y 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 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 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. 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 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 hi or greater, starting said first pump and imposing a pumping speed vl≠0 on it;

if said liquid level is greater than h2<hl but less than or equal to hi, imposing said pumping speed vl on said first pump if the latter operation;

when said liquid level reaches h2<hl, imposing a pumping speed v2<vl on said first pump during a time interval ΔΤ, such that said liquid level is kept constant;

after said time interval ΔΤ, 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 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 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, 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 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 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 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 hi or greater, said regulation system is suitable for starting said first pump and for imposing a pumping speed vl on it;

when said liquid level is greater than h2<hl but less than or equal to hi, said regulation system is suitable for imposing said pumping speed vl on said first pump when it is operating;

when said liquid level reaches h2<hl, said regulation system is suitable for imposing a pumping speed v2 on said first pump such that v2<vl during a time interval ΔΤ such that said liquid level is kept constant;

after said time interval ΔΤ, 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 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, vl 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 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 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 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 [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. 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 lOin which communicates with the interior of the well 4 and a spent liquid outlet lOout. The spent liquid pipeline 10 is configured in such a way that liquid can flow from the spent liquid inlet lOin to the spent liquid outlet lOout by gravity. In the example shown in Figure 1, this is possible since the spent liquid outlet lOout is lower than the spent liquid inlet lOin. 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 lOin to the spent liquid outlet lOout by gravity without in any way requiring the spent liquid outlet lOout to be lower than the spent liquid inlet lOin. In this case, liquid will pass from the spent liquid inlet lOin to the spent liquid outlet lOout 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 lOin to the spent liquid outlet lOout 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 lOout 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 matching part making it possible to link a free end of the junction pipeline 15 to the spent liquid outlet lOout of the spent liquid pipeline 10. By virtue of this coupling means 20, liquid can pass from the spent liquid outlet lOout 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 lOout 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 lOout 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 lOout of the spent liquid pipeline 10. In another preferred embodiment, each of the first 501 and second 502 pumps is rather linked to the spent liquid outlet lOout 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 lOout 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 lOout 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 previously or another) . When a level of liquid to be pumped is hi or greater, said regulation system 70 starts said first pump 501 and imposes a pumping speed vl on it. The first pump 501 will therefore be triggered when the liquid level is hi and will then operate at the pumping speed (or speed of rotation of a centrifugal pump) vl, 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 vl represents the maximum pumping speed (or maximum flow rate) of the first pump 501. An example of speed vl is 1500 rpm. The time for said liquid level to change from hi 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 lOout 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 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<hl (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 ΔΤ, to within the tolerance of measurement errors and with a liquid level indication tolerance which is preferably between +/- 5%. Preferably, ΔΤ 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 ΔΤ, the flow rate of the first pump 501 is equal to the effluent intake flow rate.

[ 00048 ] Once the time interval ΔΤ 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 hi 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 the self-clearing of an inclined spent liquid pipeline 10 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 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 was stated that the spent liquid pipeline 10 will be filled once again to the level hi 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>hl in an upward vertical direction. Preferably, h4 is situated at a vertical distance from hi of between 20 and 80 cm. Even more preferably, h4 = hi + 40 cm. To illustrate 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 hi to h5 : hl=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 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. 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 lOout (that is to say, in a region situated at a distance less than 35 cm from said spent liquid outlet lOout 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 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 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 lOout 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 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 lOin is situated at a greater (or higher) level relative to the spent liquid outlet lOout 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 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 lOout. 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 lOin 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 lOout of the spent liquid pipeline 10, for example at less than 35 cm from said spent liquid outlet lOout. 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. [00068] The inventors also propose, according to another preferred embodiment, to position the spent liquid pipeline 10 such that its spent liquid inlet lOin 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 lOout 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 lOout 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 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 con ugations, 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.