EP2867416B1 - Automatic flushing device for controlling the operation of a drain trap - Google Patents

Description

Technical area :

The present invention relates to an automatic flushing device for regulating the operation of a drain-siphon comprising at least one vertical drain implanted in a ground to be stabilized, this drain being pumped by a main siphon whose upstream and downstream ends are immersed each in a liquid reservoir whose level is defined by a reference plane, said automatic flushing device comprising at least one vertical charge accumulator containing said reservoir into which the downstream end of said main siphon opens, this charge accumulator being pumped by a secondary siphon whose downstream end terminates in a main outlet, said secondary siphon being partially isolated inside a bell connected to said charge accumulator by a perforated lower part and the upstream end of said secondary siphon communicating with the atmosphere through a control duct.

Prior art:

In known manner, the deep drainage of the soil is carried out by discharging the liquid captured, mainly water, by means of one or more vertical drains arranged in the ground. This drainage can be carried out by various techniques such as pumping, gravity evacuation, siphoning. The invention applies to the latter technique namely to perform a pumping by a siphoning pipe or siphon set up in a drain located near a vertical drop geometrically allowing siphoning. This technique of drain-siphon DS is described in particular in the publication FR 2 593 203 from the same inventor, illustrated in figure 1 and can be applied to various fields such as pumping, tablecloth deep excavations or compressible areas, embankment drainage, stabilization of landslides.

It consists in equipping drains 1, extending vertically inside boreholes 10 made in a ground 2 to drain and opening at the top in manholes 11, a pumping siphon 3 provided with a branch ascending 30 housed inside each drain 1 and ending with an upstream end 31 permanently immersed in a reservoir 32 of liquid whose level is set on a reference plane PR, and a descending branch 33 inclined according to the slope 20 of the land 2 and ending with a downstream end 34 whose outlet 35 forms an outlet. The downstream end 34 can be immersed in a reservoir 36 of liquid whose level is set on the reference plane PR. It can also be in the open air and have in this case a curved end terminated by the outlet orifice 35 rising at said reference plane PR. The downward branch 33 of the siphon 3 is placed in the slope 20 of the ground 2 so that it is frost-free and out of the effects of the sun. It is also protected by tubes 37.

One of the recurring problems of this technique is the risk of defusing the siphon 3. Indeed, when the equilibrium water at atmospheric pressure rises in the ascending branch 30 of the siphon 3, it lowers pressure. As a corollary, it releases a portion of the dissolved gas in the form of microbubbles. Moreover, at the level of the descending branch 33 of the siphon 3, a phenomenon of coalescence occurs, that is to say that the microbubbles assemble to form bubbles of larger diameter. They are then subjected to opposing forces: on the one hand to the Archimedes push tending to raise bubbles inside the siphon 3 and on the other hand to a hydraulic force inherent in the flow of water to the outlet 35 of the siphon 3. In fact, if the flow rate is sufficient, the bubbles are conveyed to the outlet 35. On the other hand, if this flow reaches a critical value also called critical flow, the thrust of Archimedes tends to prevail over the hydraulic force and the bubbles go back to the high point PH of the siphon 3 where they accumulate and can cause the defusing thereof.

To solve this problem, it is sought to stop the flow of the siphon 3 when it reaches said critical value and to reboot said siphon 3 when the renewed hydraulic load in the bore 10 at which the drain 1 is installed becomes sufficient to cause at the siphon 3 a turbulent regime to remove the air bubble that has accumulated there.

The publication FR 2,719,085 of the same inventor proposes to equip the downstream end 34 of the siphon 3 with an automatic flushing device CA, as illustrated in FIG. figure 2 this device being arranged in a work of art represented by a wall 12.

The upstream end 31 of the main siphon 3 is immersed permanently in a reservoir 32 of liquid placed in the lower part of the drain 1, the upper level of said reservoir 32 being keyed on the reference plane PR. The reservoir 32 extends above said reference plane PR by a portion of perforated tube 38 allowing the penetration of water into said reservoir 32 and may constitute an additional filter.

Où

• pa : est la pression la plus basse envisageable au zéro de la mer en mètres d'eau
• x : est l'altitude du lieu considéré en mètres
• f(θ) : est fonction de la température θ la plus élevée que peut atteindre l'eau dans le siphon et correspond à la pression de vaporisation de l'eau à la température de l'eau dans ledit siphon exprimée en mètres d'eau.

The reference plane PR is wedged below the high point PH of the main siphon 3 at a depth P given by the relation: $$\mathit{P}=\mathit{pa}-\mathit{1},{\mathit{16}}_{\frac{\mathit{x}}{\mathit{1000}}}-\mathit{f}\left(\mathit{\theta }\right)$$

Or

• pa : is the lowest possible pressure at zero of the sea in meters of water
• x : is the altitude of the place in meters
• f (θ) : is a function of the highest temperature θ that can reach the water in the siphon and corresponds to the vaporization pressure of the water at the water temperature in said siphon expressed in meters of water .

The downstream end 34 of the main siphon 3 descends below said reference plane PR, is curved and ends with an outlet orifice 35 at said reference plane PR connected to a charge accumulator 4 in the form of a vertical tube , open in its upper part 40 and closed in its lower part 41 by a plug 42. This plug 42 is traversed by a tube forming a secondary siphon 5 provided with a descending branch 50 housed in the charge accumulator 4 and a U-shaped downstream end 51 always full of water in normal operation. The descending branch 50 of the secondary siphon 5 is enclosed in a bell 6, closed in its upper part 60 and perforated in its lower part 61 at its junction with the plug 42, the upper part of the perforations being at the level of the PR reference. The outlet orifice 52 of the secondary siphon 5 forms an outlet and ends at a level below the reference plane PR below the perforated lower portion 61 of the bell 6.

A control duct 7 communicates the downstream branch 50 of the secondary siphon 5 with the atmosphere and is connected thereto at a connection point 70 located in the lower part 41 of the charge accumulator 4 and more particularly in the plug 42. The free end 71 of the regulating conduit 7 has a stick shape which penetrates inside the upper part 40 of the charge accumulator 4, its outlet orifice 72 going down below the level of the inlet port 53 of the secondary siphon 5.

When the flow rate of the main siphon 3 reaches the critical flow rate, the water in the charge accumulator 4 passes below the perforated lower portion 61 of the bell 6 creating an air inlet defusing the hunting device. automatic AC The downstream end 51 in U secondary siphon 5 remains full of water after defusing.

When the upstream hydraulic load increases by the rise of the water in the drain 1 or the borehole 10, the water rises in the charge accumulator 4 fed by the main siphon 3. The water goes up in parallel in the bell 6 to reach the outlet orifice 72 of the control duct 7. The gas contained at the top of the bell 6 and in the descending branch 50 of the secondary siphon 5 rises in pressure and imbalances the water contained in the downstream end 51 U U secondary siphon 5. The upstream level descends into the U-shaped downstream end 51 and the plane of contact between the pressurized air and the discharged water becomes vertical. Then this plane is smashed by the air that escapes through the outlet 52 and the secondary siphon 5 begins with the thrust of the water in the bell 6 allowing the main siphon 3 to activate through the decline fast water in the charge accumulator 4.

The operation of the automatic flushing device CA as described above still has drawbacks. When the degassing bubbles arrive through the main siphon 3 in the charge accumulator 4, they can be sucked inside the bell 6 in depression and can prematurely defuse the bell 6. When the automatic flush device CA s' primer, the main siphon 3 has an inertia which is a function of its length and the amount of accumulated bubbles. The automatic flushing device CA can enter the defoaming phase too quickly, that is to say before all the degassing bubbles have been able to escape from the main siphon 3. When the liquids from the drainage, the water in majority, pose problems of deposition of calcite or clusters of iron bacteria, pipes and orifices can become clogged. Finally, when the atmospheric pressure varies, in particular during climatic changes, or when the upstream hydraulic load decreases, for example when a neighboring drilling has started, the downstream end 51 in U of the secondary siphon 5 is partially emptied of a certain amount of water having the effect of disrupting the operation of the automatic flushing device CA.

Presentation of the invention

The present invention aims to overcome these disadvantages by proposing to improve the current automatic flushing device by a simple device, economical, easy to implement, to prevent its defusing by the presence of degassing bubbles, to prevent its fouling by the deposition of calcite or iron oxides, and to guarantee a constant operation of the drain-siphon keel whatever the climatic conditions and / or the conditions of hydraulic load in the drilling.

For this purpose, the invention relates to a device of the type indicated in the preamble, characterized in that said secondary siphon comprises, in addition to said main outlet, at least one auxiliary outlet smaller than the main outlet, located at a level below that of said main outlet and arranged to generate a slow flow regime, in that said charge accumulator comprises an enlarged zone integrating said reservoir in which opens the downstream end of said main siphon, said enlarged zone constituting a buffer reserve which s' adds to said reservoir and extends above said reference plane to a so-called buffer level, and in that said main outlet is located at the same level as said buffer level and said auxiliary outlet is located below said buffer plane. reference.

Thanks to this new construction, the automatic flushing device allows the drain to be drained in two stages: a short operating cycle generating a rapid hydraulic load downstream of the main siphon, followed by a slow operating cycle allowing time for the bubbles to degassing to escape from said main siphon.

In a preferred embodiment, the perforated lower end of said bell connected to said charge accumulator and the inlet of the downstream end of said main siphon in said enlarged zone are remote thereby avoiding degassing bubbles from being sucked by the bell in depression.

Similarly, the perforations of the lower end of said bell which is connected to the lower part of said charge accumulator are located just above said reference plane and delimit said liquid reserve.

The downstream end of said secondary siphon advantageously has a U-shape which terminates in said main outlet and has a lateral branch terminated by said auxiliary outlet.

In the preferred embodiment, the downstream end of said secondary siphon is coupled to a safety tank connected to said lateral branch, said safety tank having a lateral outlet opening forming said auxiliary outlet and being filled with liquid up to the level of said secondary outlet. said auxiliary outlet ensuring the filling of the U-shaped downstream end of said secondary siphon to a level called reserve level.

Said safety tank may comprise permanent liquid supply means arranged to maintain said reserve level, these means may comprise a Mariotte vessel connected to said safety tank and coupled to a filling valve.

In addition, said device may comprise means for treating the liquid pumped by said main siphon arranged to prevent fouling of said automatic flushing device by deposits, these means possibly comprising a liquid reservoir containing at least one treatment additive connected to said charge accumulator, which may advantageously consist of a Mariotte vessel connected to said enlarged zone and coupled to a filling valve.

Brief description of the drawings:

• la figure 1 est un schéma de principe d'un drain-siphon de l'art antérieur, la figure 2 représente schématiquement un dispositif de chasse automatique associé à un drain-siphon de l'art antérieur, et
• la figure 3 représente schématiquement le dispositif de chasse automatique perfectionné selon l'invention.

The present invention and its advantages will appear better in the following description of an embodiment given by way of non-limiting example, with reference to the appended drawings, in which:

• the figure 1 is a schematic diagram of a drain-siphon of the prior art, the figure 2 schematically represents an automatic flushing device associated with a drain-siphon of the prior art, and
• the figure 3 schematically represents the improved automatic flushing device according to the invention.

Illustrations of invention and best way to make it:

With reference to the figure 3 , the automatic flushing device CA for regulating the operation of a drain-siphon DS according to the invention constitutes an improvement of the known device according to the figure 2 and the publication FR 2 719 085 which relates to an automatic flushing device CA connected to the downstream end 34 of the main siphon 3. In these figures, the parts which are identical bear the same reference number and are not described again. The charge accumulator 4, which is formed of a vertical tube open in its upper part 40 and closed in its lower part 41 by a plug 42, has an enlarged zone 43 in its lower part 41. This enlarged zone 43 is extends above the plug 42 and beyond the reference plane PR and forms a buffer reserve up to a level called NT buffer level. The volume of this enlarged zone 43 is calculated to allow the total draining of the descending branch 33 of the main siphon 3 and the evacuation of the degassing bubbles before the defusing of the automatic flushing device CA. The outlet orifice 35 of the main siphon 3 enters said enlarged zone 43 by an inlet orifice 44 located just below the reference plane PR while the perforations of the lower part 61 of the bell 6 are located just above the reference plane PR. In this way, the bottom of the enlarged zone 43 contains a reserve of water 36 extending between the plug 42 and the reference plane PR in which opens the downstream end 34 of the main siphon 3 now the main siphon 3 still in water. Owing to the presence of the enlarged zone 43, the outlet orifice 35 of the main siphon 3 is remote from the perforations of the lower part 61 of the bell 6 preventing the degassing bubbles from being sucked by the bell 6 under vacuum.

The automatic flushing device CA according to the invention is provided with two outlets 52, 54 of different diameters, located downstream of the secondary siphon 5: a main outlet 52 vertical corresponding to the outlet orifice of the secondary siphon 5 located above of the reference plane PR, and more precisely at the buffer level NT of the widened zone 43, and a lateral auxiliary outlet 54, of smaller diameter, situated on a bypass 55 of the secondary siphon 5 below the reference plane PR at a distance of NR reserve level. This reserve level NR defines the level of water contained in the lower part 51 in U secondary siphon 5 that seeks to maintain water. The presence of these two outlets 52, 54 makes it possible to generate a drain of the drain 1 in two stages: a short operating cycle generating a rapid hydraulic load downstream of the main siphon 3 by the main outlet 52, followed by a cycle of slow operation allowing the degassing bubbles time to escape from the main siphon 3 through the auxiliary outlet 54. The diameter of the auxiliary outlet 54 is calibrated so that the flow it generates is slightly greater than the critical flow of the siphon main 3, when the hydraulic load on the bell 6 reaches the upper part of the perforations 61 causing the defusing.

In order to keep the lower U-shaped portion 51 of the secondary siphon 5 in water and prevent its defusing, which can be caused in particular by the imbalance of the atmospheric pressure as a function of the climate and / or by the priming of a neighboring borehole, the device according to the invention comprises a safety tank 8 which is connected to the bypass 55 of the secondary siphon 5 and is provided with a lateral outlet opening forming the auxiliary outlet 54. The vertical position of the auxiliary outlet 54 defines the level of water contained in this safety tank 8, called the reserve level NR, which corresponds to the level of water contained in the lower portion 51 of the secondary siphon 5. The level of reserve NR is kept constant by means in the example shown, consist of a Mariotte vase 80 filled with water by a filling valve 81. It comprises an upper portion 82 closed and a lower portion 83 closed which communicates with the reservoir of safety 8 by two ducts 84, 85 parallel stopping at NR reserve level, including a short conduit 84 opening at the base of the vase 80 and a long conduit 85 opening to the top of the vase 80 to put the top of the vase Mariotte 80 at atmospheric pressure when the NR reserve level tends to fall. When the reserve level NR decreases, the short duct 84 replenishes water by emptying part of the Mariotte 80 vessel until the reserve level NR rises and closes the short ducts 84 and 85. Mariotte 80 may be supplemented with water by the filling valve 81 connected to a water network and controlled manually or automatically according to a signal provided by a level detector or the like.

The automatic flushing device CA according to the invention also comprises means 9 for treating the water pumped into the soil through the drain 1 via the main siphon 3 in order to avoid the risk of clogging of the automatic flushing device CA by means of deposits of calcite, iron oxide bacteria or the like. In the example shown, the processing means 9 comprise a Mariotte vessel 90 filled with water containing at least one chemical treatment additive adapted as a function of the possible deposits by a filling valve 91. This treatment additive may be for example, sulfamic acid for calcite, hexametaphosphate of soda or oxalic acid for iron bacteria, or any other additive depending on the type of fouling to be feared. It comprises an upper portion 92 closed and a closed lower portion 93 which communicates with the enlarged region 43 of the charge accumulator 4 by two parallel conduits 94, 95 stopping at the same level above the reference plane PR, including a short duct 94 opening at the base of the vase 90 and a long duct 95 opening at the top of the vase 90. The principle of the Mariotte vase 90 provides a constant flow, in particular a drop by drop, by acting on the atmospheric pressure and on the diameter of the short duct 94. The Mariotte 90 can be filled with liquid supplemented with chemical product (s) by the filling valve 91 manually or automatically. Of course, any other equivalent means may be suitable such as for example a simple exchange system obtained by osmosis.

Possibilities of industrial application:

The operation of the automatic flushing device CA according to the invention is now described. When the critical flow is reached, it is defused. The water level in the charge accumulator 4 is lowered at the reference plane PR under the perforated lower part 61 of the bell 6 and the secondary siphon 5 keeps a water level in its lower part 51 U wedged on the reserve level NR defined by the auxiliary outlet 54 and the safety tank 8. When the drain 1 is hydraulically recharged upstream, there is a rise in the water in the charge accumulator 4, the incoming water through the outlet 35 of the main siphon 3 in the enlarged zone 43. If degassing bubbles entrained by the flow of water in the main siphon 3 open into the enlarged zone 43, they can be evacuated automatically by the upper part 40 open to the atmosphere of the charge accumulator 4. Unlike the known device, they are not sucked into the bell 6 by its perforated lower part 61, the latter being remote from the outlet orifice 35. The ascent water in the charge accumulator 4, simultaneously enters the bell 6 by its perforated lower part 61 and generates the increase in pressure of the air contained in the bell 6 and in the descending branch 50 of the secondary siphon 5. When under the air pressure, the secondary siphon 5 discharges the water contained in its U-shaped downstream portion 51 by the main outlet 52, the air pressure contained in the bell 6 and in the descending branch 50 relaxes starting the bell 6 and the secondary siphon 5 thus creating a rapid and brutal emptying of the charge accumulator 4 up to the buffer level NT corresponding to the first operating cycle. This creates a hydraulic load on the main siphon 3 between the hydraulically loaded drain 1 and the downstream of the main siphon 3 suddenly discharged by the flushing effect.

The purpose of the regulation duct 7 is to reinitiate the secondary siphon 5. In fact, it allows the water to be allowed to rise in the bell 6 when it goes up into the charge accumulator 4, since the air driven in front of it can escape through the control duct 7 by taking the descending branch 50 of the secondary siphon 5. When the level of the water in the charge accumulator 4 reaches the outlet orifice 72 of the free end 71 of said duct 7, the air can no longer escape and increases in pressure at the top of the bell 6 and in the descending branch 50 of the secondary siphon 5. By adjusting the value of the rebooting load by the distance between the orifice of output 72 of the control duct 7 and the reference plane PR, a hydraulic head is created on the main siphon 3 generating the expected turbulence regime and causing the complete bleeding or partial degassing bubbles accumulated at the high point PH of the main siphon 3 and by so much his reboot.

• un cycle court par l'exutoire principal 52 pour vidanger le siphon principal 3 par une différence de charge entre l'amont et l'aval qui baisse rapidement, de façon à créer un régime turbulent dans le siphon principal 3 entraînant les bulles de dégazage accumulées et stagnantes à l'arrêt du débit du siphon 3,
• un cycle lent par l'exutoire auxiliaire 54, qui entre en action lorsque l'exutoire principal 52 s'arrête, le niveau d'eau dans le dispositif de chasse automatique CA ayant atteint le niveau tampon NT, pour purger le siphon principal 3 de toutes les bulles accumulées grâce à la réserve tampon au sein de la zone élargie 43 de l'accumulateur de charge 4. Le débit en fin de cycle de vidange doit toujours être supérieur (par exemple de 1,1 fois) au débit critique du siphon principal 3.

Thanks to the design of the automatic flushing device CA according to the invention, this flush is created in two stages:

• a cycle runs through the main outlet 52 to drain the main siphon 3 by a difference in charge between the upstream and downstream which rapidly decreases, so as to create a turbulent regime in the main siphon 3 causing accumulated degassing bubbles and stagnant when the flow of the siphon 3 is stopped,
• a slow cycle by the auxiliary outlet 54, which comes into action when the main outlet 52 stops, the water level in the automatic flushing device CA having reached the buffer level NT, to purge the main siphon 3 of all the bubbles accumulated thanks to the buffer reservoir within the enlarged zone 43 of the charge accumulator 4. The flow rate at the end of the emptying cycle must always be greater (for example by 1.1 times) than the critical flow of the siphon principal 3.

The automatic flushing device CA can occur in a dysfunctional situation if, when it was going to be put into action, there is a drop in the surrounding atmospheric pressure related to climate change or the initiation of neighboring drilling disturbing the level of water in the drilling that would begin. The secondary siphon 5 can be started without the bell 6 starting. The next cycle can not be rebooted. The presence of the safety tank 8 avoids this risk and allows the U-shaped downstream portion 51 of the secondary siphon 5 to always be in water so that it is ready to be rebooted.

Likewise, the increase in atmospheric pressure can also be a source of dysfunction. It results in a decrease in the volume of air under pressure inside the bell 6 and the secondary siphon 5. The water level in the descending branch 50 of the secondary siphon 5 and in the bell 6 rises and can find at the inlet port 53 of said secondary siphon 5 and cause a drip situation. It must therefore be ensured that there is a sufficient difference in level between the level of the water in the bell 6, determined by the geometry of the regulation pipe 7 and the inlet orifice 53 of the secondary siphon 5.

It is clear from this description that the invention achieves the goals. The present invention is not limited to the embodiment described but extends to any modification and variation obvious to a person skilled in the art while remaining within the scope of protection defined in the appended claims.

Claims (10)

1. Automatic flushing device (CA) for regulating the operation of a drain trap (DS) comprising at least one vertical drain (1) located in a soil to be stabilized, this drain being pumped by a main siphon (3) whose upstream (31) and downstream (34) ends are immersed each in a tank (32, 36) of liquid whose level is defined by a reference plane (PR), said automatic flushing device (CA) comprising at least one vertical charge accumulator (4) containing said tank (36) into which the downstream end (34) of said main siphon (3) opens, this charge accumulator (4) being pumped by a secondary siphon (5) whose downstream end (51) ends with a main outlet (52), said secondary siphon (5) being partly isolated inside of a bell (6) connected to said charge accumulator (4) through a perforated lower section (61) and the upstream end (50) of said secondary siphon (5) communicating with the atmosphere by means of a regulation tube (7), characterized in that said secondary siphon (5) comprises, in addition to said main outlet (52), at least one auxiliary outlet (54) that is smaller than the main outlet (52), located at a lower level that that of said main outlet (52) and arranged to generate a slow flow regime, in that said charge accumulator (4) comprises a wider area (43) including said tank (36) into which the downstream end (34) of said main siphon (3) opens, said wider area (43) forming a butter reserve adding itself to said tank (36) and extending above said reference plane (PR) up to a level called buffer level (NT), and in that said main outlet (52) is located at the same level as said buffer level (NT) and said auxiliary outlet (54) is located below said reference plane (PR).
2. Device according to claim 1, characterized in that the perforated lower end (61) of said bell (6) connected to said charge accumulator (4) and the inlet opening (44) of the downstream end (34) of said main siphon (3) in said wider area (43) are distant from each other.
3. Device according to claim 1, characterized in that the perforations of the lower end (61) of said bell (6) that is connected to the lower section (41) of said charge accumulator (4) are located just above said reference plane (PR) and delimit said reserve (36) of liquid.
4. Device according to claim 1, characterized in that the downstream end (51) of said secondary siphon (5) has a U-shape that ends with said main outlet (52) and comprises a lateral branch (55) ending with said auxiliary outlet (54).
5. Device according to claim 4, characterized in that the downstream end (51) of said secondary siphon (5) is coupled to a safety tank (8) connected to said lateral branch (55), this safety tank (8) comprising a lateral outlet opening forming said auxiliary outlet (54) and being filled with liquid up to the level of said auxiliary outlet (54) ensuring the filling of the U-shape of the downstream end (51) of said secondary siphon (5) up to a level called reserve level (NR).
6. Device according to claim 5, characterized in that said safety tank (8) comprises permanent liquid supply means (80) arranged to maintain said reserve level (NR).
7. Device according to claim 6, characterized in that said supply means comprise a Mariotte vessel (80) connected to said safety tank (8) and coupled to a filling valve (81).
8. Device according to claim 1, characterized in that it comprises means (9) for treating the liquid pumped by said main siphon (3) arranged for limiting the fouling of said automatic flushing device (CA).
9. Device according to claim 8, characterized in that said treatment means (9) comprise a liquid tank containing at least one treatment additive connected to said charge accumulator (4).
10. Device according to claim 9, characterized in that said liquid tank containing at least one treatment additive is made of a Mariotte vessel (90) connected to said wider area (43) and coupled to a filling valve (91).

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