Device and method for electric cleaning

Abstract

The invention relates to a device for electric cleaning in which ducts are tackled indirectly, comprising: - two electrodes (2, 4) facing each other, applied against an insulating surface (6); - means (14) for generating high-voltage electrical pulses; and - means (12) for transmitting and applying said pulses between the two electrodes.

Description

[0001] DESCRIPTION

[0002] Title of the invention: ELECTROCLEANING DEVICE AND METHOD

[0003] TECHNICAL FIELD AND STATE OF THE PRIOR ART

[0004] The present invention relates to a system or device for cleaning a pipe or conduit, for example in a drainage network.

[0005] The principle of groundwater drainage aims to reduce the hydraulic load applied to human-made structures or natural areas intended for agricultural use. It consists of a network of pipes (the drains) with fine perforations allowing water to enter the said pipes. These pipes can have a sufficient slope for the flow of water towards an outlet characterized by a hydraulic load significantly lower than that of the volume to be drained. The material constituting the drains generally has corrosion-resistant qualities to guarantee their durability. Modern drains are generally made of flexible plastic tubes. But a drainage network often gradually clogs.

[0006] Indeed, a set of physicochemical phenomena occur at the interface between the surrounding environment and the inside of the drains. These phenomena result in deposits of solid matter not only inside the pipes but also in the perforations of their wall as well as on the external surface of these drains (the extrados). The extent of these phenomena sometimes leads to a total loss of efficiency of the drainage system.

[0007] The phenomena which lead to this clogging are of two types:

[0008] The first phenomenon is linked to the entrainment of soil particles (the "fines") by the flow of water heading towards the drains; the fines, whose size is equal to or greater than that of the perforations in the pipes, tend to accumulate on the extrados of the drains. This accumulation results in the clogging of some of the perforations and creates hydraulic head losses along the path of the drainage water. This results in a reduction in the flow of water entering the pipes and an overall reduction in the efficiency of the drainage system. The second phenomenon is linked to the crystallization, upon contact with the drains, of elements dissolved in the water. Indeed, from a hydraulic point of view, the interior of the drains is subject to frequent load variations, particularly depending on seasonal fluctuations. These fluctuations result in an altimetric variation of the water-air interface.Drainage water therefore passes from an environment characterized by a continuous liquid phase (the ground to be drained) to an environment presenting a liquid phase in contact with a gaseous phase (the interior of the drains). The existence of this interface causes a modification of the natural chemical balances. This is particularly the case for the calcium-carbonic balance. In a naturally acidic environment with an excess of carbon dioxide, natural carbonates (limestone from geological formations) or anthropogenic carbonates (structural concrete of structures) are partially dissolved in the form of calcium bicarbonate (Ca(HCO3h). When CO2 degassing occurs at the water-air interface, the calcium-carbonic balance shifts and the calcium bicarbonate crystallizes in the form of calcite (CaCOs).Calcite is a hard crystalline mineral species that adheres to all physical supports present: the interior surface of drains, the thickness of their walls at the perforations, the exterior of drains and the piles of fines. The continuous nature of this phenomenon results in a progressive clogging of drainage systems. Beyond the example of calco-carbonic equilibrium, there are other physicochemical phenomena that lead to the same result.

[0009] To eliminate the effects of clogging phenomena, several cleaning techniques are traditionally implemented: hydro-cleaning, mechanical milling, chemical descaling and biological descaling. Hydro-cleaning is the most commonly used technique. This technique consists of injecting water under high pressure (100 to 500 bars) through nozzles mounted on an injection head itself attached to the end of an umbilical. Water jets are divided into two categories: axial or lateral jets which aim to destroy deposits and rear jets which aim to both remove detached products and propel the probe forward.

[0010] Mechanical milling involves using a robot, generally consisting of a rigid body (usually about 0.4 m long) mounted on a wheel and equipped with an articulated arm carrying a cutter. The cutter is driven in rotation electrically or hydraulically.

[0011] Chemical descaling involves injecting acid into drains to dissolve the carbonate component of the deposits. This technique is only possible if access to the drains is possible upstream. This method has the disadvantage of releasing pollutants into the natural environment.

[0012] The biological cleaning technique involves injecting a solution containing a colony of bacteria that secrete an organic acid capable of attacking the carbonate components of the deposits. However, as in the previous case, this technique requires access upstream of the drains. Furthermore, its effectiveness is moderate. A problem with all these techniques is that they only treat deposits inside the drains. On the other hand, deposits that obstruct the perforations in the walls and those that accumulate on the extrados are only very little or not at all removed by these methods. In addition, since most modern drains are made of plastic, their mechanical strength is often lower than that of the deposits obstructing them.Thus, hydro-cleaning techniques (particularly high pressure) or mechanical milling often result in destruction of the drain walls because these methods do not allow the material of the deposits to be distinguished from that constituting the drain walls.

[0013] Identical or similar problems may arise in any other pipe or conduit in which a fluid or liquid circulates leading to a deposit of material on the inner surface of this pipe or conduit and / or which at least partially blocks one or more orifice(s) made in this conduit and / or the flow section of this conduit, for example at the intersection with another conduit which connects to the 1 er; similarly, deposits, which may originate from the environment in which the pipe or conduit is installed, may occur on a surface external to this pipe or conduit, which may lead to a reduction in its permeability and / or to poorer performance of the entire system for the evacuation of liquid (for example, for a drainage system, the development of concretion, particularly calcite, in the drainage base reduces its permeability by closing the free space through which water circulates between the aggregates of the base; in the long term, the drainage base becomes less efficient upstream of the drains for evacuating water).

[0014] More generally, the problem arises of finding a new device and a new process for cleaning or clearing a pipe or conduit in which a liquid circulates.

[0015] Preferably, this new method or this new device is more effective than the known methods or devices and allows better elimination of solid deposits produced in the conduit or the pipe or against the interior and / or exterior surface of the wall which delimits this conduit or this pipe.

[0016] Also preferably, it allows better removal of solid deposits made in a conduit or pipe, such as a drain made of a material such as a plastic material, or around such a drain.

[0017] STATEMENT OF THE INVENTION

[0018] The invention firstly relates to a conduit electro-cleaning device comprising electrodes, which can for example be applied against an insulating surface, so as to allow the creation of an electric arc on the surface of the insulator which separates the electrodes.

[0019] These electrodes allow the creation of an electric arc between them, in a liquid medium in which the device can be brought. In the case of the presence of an insulating surface (so-called "surface" configuration), the arc is generated on the surface of the insulator, between the two electrodes and in contact with the liquid medium. In the case of a so-called "volume" configuration, the arc is generated in the liquid medium along the shortest path between the 2 electrodes and the shock wave propagates in this medium.

[0020] The surface configuration is advantageous because the so-called “gap” tension is lower than that of the volume configuration.

[0021] The invention allows for an indirect attack to be implemented, in which an arc is created outside the material to be fractured: it is the shock wave, which impacts the surface of the material to be fractured, which acts against the latter. The energy is deposited on the surface of the material via the aqueous medium.

[0022] In contrast, a direct attack involves creating an arc in the material to be fragmented. Plasma is created within the material and causes it to explode from within. The energy is deposited within the material.

[0023] According to the invention, an indirect attack is carried out, which is more interesting than a direct attack; in fact the latter is more difficult to implement because it requires good quality contact between the electrodes of the probe and the material to be fragmented, which is impossible in the case of anarchic growth of the material.

[0024] The electrodes are preferably arranged opposite each other and / or face each other. A device according to the invention may further comprise, or be associated with:

[0025] - means for generating electrical pulses, for example pulses of power between 10 MW and 60 MW and / or of voltage between 10 kV and 60 kV;

[0026] - means for transmitting, or for transmitting and applying, said pulses to the electrodes or between the two electrodes.

[0027] The technique according to the invention preferably uses High Pulsed Power (HPP) technology, which makes it possible to compress energy from a quasi-static source into controlled pulses, preferably very dense and very short, more preferably delivering very high power, for example between 10 MW and 60 MW. High Pulsed Power refers to the compression of energy, coming from a "quasi-static" source, into single-shot pulses or pulses with controlled repetition rates, which are very dense and very short, thus delivering very high power.

[0028] The pulses can be generated at a frequency of the order of Hz, or at a higher frequency, which allows the deposited material not to relax sufficiently after each pulse. In other words, the relaxation time is less than the firing frequency, for example it is several orders of magnitude lower. A device or method according to the invention makes it possible to implement a hydrodynamic effect, where the electric arc creates a pressure or shock wave in the liquid which will then fracture the solids deposited in or against the wall which delimits the pipe or conduit. The electrodes and the medium to be fragmented are bathed by a continuous aqueous liquid phase, except for the case of a medium to be fragmented located against the pipe or conduit, but outside of it (but the continuous aqueous liquid phase is still necessary for the shock wave to be able to propagate).This operation is more suitable than the electrohydraulic effect, in which the electric arc fractures solids by penetration, because the operation according to the invention does not require close physical contact between the electrodes and the substrate to be fragmented. A device according to the invention can have various geometric shapes.

[0029] It may have a major axis (XX'), which may be aligned with a flow axis of a fluid in a pipe. The insulating surface against which the electrodes are applied may be:

[0030] - plane and perpendicular to said axis (XX');

[0031] - or of revolution around said axis.

[0032] Preferably this surface is of high resistivity (for example between 10 12 MCQ and 10 15 QCM).

[0033] Furthermore, the geometric shape of the device according to the invention can be designed to allow progression of this device in both directions, in a conduit on which deposits, for example concretions, may have formed in a very irregular, or even pseudo-chaotic, manner. For example, the probe has on its front face (in the direction of movement of the device in a conduit) a rounded shape and / or angles and / or on its rear face (cable side) a shape, for example conical, facilitating its removal even in the case of piles of debris resulting from the fracturing of the concretions.

[0034] Preferably:

[0035] - a device according to the invention has a generally cylindrical shape, with a total external diameter less than that of a pipe of a conduit into which it is to be introduced;

[0036] - and / or has an electrode configuration: -called “axial”, to treat deposits or concretions which tend to close or block the lumen or the flow section of the conduit to be unblocked;

[0037] - and / or a so-called “parietal” configuration to treat deposits of concretions developing on the walls of the conduit to be unblocked.

[0038] Preferably, the spacing between the electrodes is adjustable, which makes it possible to adjust the threshold voltage and thus the energy of the electric arc which is generated. For example, means are provided for dismantling one and / or the other of the electrodes and for replacing it with an electrode of a different size or diameter, leading to a different inter-electrode spacing.

[0039] A device according to the invention may comprise an external profile comprising, for example, at least one groove for discharging gas formed by an arc established between the two electrodes. Thus, gases generated by the electric arc do not remain blocked at the inter-electrode space, which would impair the operation of the device.

[0040] In a device according to the invention, the means for generating high voltage electrical pulses make it possible to, or are capable of, generating pulses:

[0041] - voltage which can be between 10 kV and 60 kV.

[0042] - of intensity for example between 5 kA and 20 kA,

[0043] - over a period of, for example, less than 50 ps.

[0044] - power between 0.1 and 10 GW;

[0045] The electrodes may be spaced a uniform distance apart and / or the device may include means for adjusting this distance (d).

[0046] A device according to the invention may further comprise;

[0047] - means for damping shock waves;

[0048] - and / or reflector means for directing shock waves.

[0049] A method for electro-cleaning a conduit according to the invention may implement a device according to the invention as defined above and / or in this application. It may therefore be applied to a conduit delimited by at least one wall and containing a liquid, said wall having a surface partly covered by one or more deposits of solid material to be removed and / or said conduit being at least partially obstructed by at least one deposit of solid material to be removed; a method according to the invention may comprise: - the positioning of a device according to the invention, as defined above and / or in this application, in said conduit;

[0050] - the generation of electrical pulses, preferably at high voltage, to obtain for example a power of between 10 MW and 60 MW and / or a voltage of between 10 kV and 60 kV between the electrodes;

[0051] - the formation of an electric arc between the electrodes, on the insulating surface and in the liquid, for example in at least one direction parallel to one or more deposits of solid material to be eliminated, preferably as close as possible to the concretion to be eliminated.

[0052] Electrical pulses are for example generated by means of an energy bench, then transmitted via a coaxial cable to a probe to obtain for example the power and / or voltage mentioned above between the electrodes of the probe.

[0053] For example :

[0054] - at the probe level, the voltage is between 10 kV and 60 kV and the energy delivered is between 100 J and 600 J;

[0055] - the time before breakdown (i.e. before the instant of formation of the arc between the electrodes of the probe) is for example of the order of 10 ps, ​​the complete duration of the arc to evacuate the energy can be of the order of 40 ps.

[0056] On this basis, the power, in the sense of the energy flow delivered between the electrodes, may well be between 10 MW and 60 MW.

[0057] Preferably, gases formed as a result of the interaction between the liquid and the electric arc are evacuated from the surface of the electro-cleaning device.

[0058] According to an application example, the solid matter deposits to be removed are calcite deposits.

[0059] The deposits of solid matter to be removed are, for example, on an inner surface of the conduit and / or on an outer surface of the conduit and / or at least partially obstruct a flow of fluid in the conduit.

[0060] The conduit is made of plastic, cast iron or ceramic, for example.

[0061] The material of the insulating surface has, for example, a dielectric constant greater than that of the liquid. In one or more implementations of a method according to the invention, the voltage pulses:

[0062] - can be generated at a rate of at least 0.2 Hz to 1 Hertz;

[0063] - and / or are high power pulses.

[0064] A method according to the invention makes it possible to eliminate deposits or concretions using electrical pulses of a duration of between, for example, 1 ps and 10 ps for an energy of, for example, between 0.5 kJ and 10 kJ. The voltage applied between the electrodes can be between 10 kV and 50 kV.

[0065] These pulses are transmitted by a cable to a probe inserted into the drain to be cleaned. The drain is immersed in a continuous liquid phase. The probe is equipped with two electrodes between which an electric arc is produced. This arc travels from one electrode to the other, following the surface of the insulation that separates them.

[0066] This electric arc causes a pressure wave in the water which, in turn, fractures and fragments the materials of the deposits and / or concretions to be removed, in particular at the planes separating the substrates of different mechanical impedance. This mechanism causes detachment of the deposits from the wall of the drains not only at the intrados (inside) and extrados (outside) but also at the perforations of the walls and / or the fluid flow section in the pipe, a section which is generally perpendicular to a longitudinal mean axis of the pipe. Overall, thanks to the device and the method according to the invention, all the deposits which obstruct the pipes are fragmented and detached from the walls. Those which are located inside the drains can then be easily eliminated. Those which are outside remain in place but their fragmentation restores the initial permeability of the natural environment.Thanks to this technique, the efficiency of a drainage system can therefore be restored without degradation of the drain walls.

[0067] In a variant, an electrocleaning system according to the invention is implemented in a so-called volume configuration. The arc is generated in the liquid medium along the shortest path between the two electrodes and the shock wave propagates in this medium. The voltage / energy / pulse duration parameters given above and in the remainder of this description can be adapted to this configuration. Several diameters and several probe geometries can be used depending on the diameter of the drain to be unblocked and the nature of the deposit to be destroyed. The probe, whatever its shape or diameter, comprises two electrodes separated by an insulator against which they are applied. The space between the electrodes is adjustable so as to vary the energy level of the arc. The greater this spacing, the greater the energy of the arc.This setting allows you to choose an arc power high enough to fracture the calcite or any material obstructing the drain without destroying the drain itself.

[0068] BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 schematically illustrates one embodiment of a probe according to the present invention.

[0070] Figure 2 represents an example of a probe according to the invention, equipped with its high voltage cable, and connected to an energy bench.

[0071] [Fig.BA], [Fig.3B], [Fig.3C] and [Fig.3D] represent an example of a probe structure according to the invention, called axial type (Figures 3A-3B), and an example of a probe structure according to the invention, called parietal type (Figures 3C - 3D);

[0072] Figure 4 represents an embodiment of an energy bench 14 which can be implemented within the framework of the present invention.

[0073] Figure 5 represents an exemplary embodiment of means making it possible to carry out the charging of a power supply device to be applied to a probe according to the invention.

[0074] Figure 6 schematically represents a coaxial cable, connected on the one hand to power supply means and, on the other hand, to an electro-cleaning probe, for example according to the invention.

[0075] Figures 7A and 7B represent an embodiment of a probe according to the invention of the axial geometry type.

[0076] Figure 7C represents an embodiment of a removable electrode for a probe according to the invention of the axial geometry type;

[0077] Figure 8 represents a view of a mechanical flange of a probe according to the invention. [Fig.9A] and [Fig.9B] represent an embodiment of a probe according to the invention, of the parietal geometry type.

[0078] Figure 9C represents an embodiment of a removable electrode for a probe according to the invention of the parietal geometry type;

[0079] [Fig.10A] and [Fig.10B] represent an embodiment of a probe according to the invention, in a so-called volume configuration.

[0080] Figures 11A and 11B represent a view of a device according to the invention, in a surface configuration, with claw-shaped electrodes;

[0081] Figure 12 represents a view of a device according to the invention, in a surface configuration, with a difference in altitude or level between the ends of the electrodes;

[0082] Figure 13 represents an example of implementation of a device according to the invention, in a drain in which concretions have formed.

[0083] Figure 14 represents the principle of high pulsed powers.

[0084] Figures 15A - 15D illustrate the relationship between firing frequency, power bank charging voltage, and HV power supply power.

[0085] [Fig.16A] and [Fig.16B] respectively represent the evolution of the voltage and current at the cable input, without the probe;

[0086] Figure 16C represents the evolution of the voltage at the cable input, with the probe;

[0087] Figure 16D represents the evolution of the probe's energy discharge.

[0088] Figure 17 shows a horseshoe-shaped drain.

[0089] Figure 18 represents a view of a device according to the invention, in a surface configuration, provided with a reflector.

[0090] DETAILED DESCRIPTION OF THE INVENTION

[0091] Figure 1 schematically illustrates a sectional view of a probe 10 that can be used in an embodiment according to the present invention.

[0092] 2 electrodes 2, 4 are arranged facing each other (their ends face each other at a distance d) and on the surface of an insulating material 6. These electrodes can have various geometries and / or symmetries, as explained below in connection with figures 3A-3D and 7A-9C. Those of figure 2 can extend in the direction perpendicular to the figure while maintaining the distance between them. They are arranged against the insulating material 6 and so that electric arcs can be generated between them and on the surface of this insulating material. For example, they can have points 3, 5 positioned against the surface of the insulating material 6 and between which the arcs can be generated. The embodiment of figure 1 concerns a so-called “surface” configuration. We present later, in connection with [Fig.lOA] and [Fig.lOB], another configuration, called “volume”.For the production of the electrodes, a stainless material should preferably be chosen, for example stainless steel, for example type 316 L steel.

[0093] The distance d between these 2 electrodes is for example between a few mm and 1 or 2 cm, for example between 5 mm and 1 cm. This distance can be variable in order to take into account different voltage values ​​and / or in order to vary the energy or voltage level or threshold from which the arc will be triggered between the electrodes: for example, at least one of the electrodes can be mounted in a removable manner in order to be able to replace it with another electrode of a different geometric shape so that the distance d is different. This can be very useful if, for example, more energy is available (for example due to more powerful means 14, described below in connection with Figure 4) to be applied between the electrodes: it will then be possible to increase the distance d between them to form an arc whose energy is sufficiently high to fracture the materials deposited on the wall to be cleaned, without however damaging the latter.This concern not to damage the wall can be particularly sensitive in the case where it is made of a material such as a plastic material (this can be the case in particular for a drain). In other words, the adjustment of the distance d between the electrodes can take into account both the energy available to be applied between them and the mechanical resistance of the wall which is to be cleaned.

[0094] One of the electrodes (4) can be connected to ground while a high voltage can be applied to the other electrode (2), for example via a high voltage cable 12, for example a coaxial cable; preferably, this cable also allows the electrode 4 to be grounded. This cable can be intended to be connected, on the other side (opposite the electrodes 2, 4), to a high voltage (HV) source 14, or high voltage (HV) energy bank, which makes it possible to generate high voltage pulses.

[0095] The probe is connected to its power cable 12 which transmits the high voltage and which is generally not very flexible. This HT cable can therefore be pushed or pulled manually or mechanically in order to move the probe into the pipe or drain to be treated. If the cable is too flexible, any other means can be associated (needle, water jet thruster, robot, etc.) to move the probe into a pipe or drain. According to another aspect, it may be preferable, before any cleaning operation of a device according to the invention, to carry out an inspection, for example by a video camera, of the pipe or the drain to be treated to identify the position of the deposits to be destroyed. This makes it possible to determine at what depth in the drain the area to be treated is located. Then, the probe can be introduced to the previously identified locations. Generally speaking, the probe can be propelled and pulled by means of the HT cable which is semi-rigid.The action is done either manually or with the help of a remotely controlled mechanical device which acts on the cable.

[0096] For example (see the curves in Figures 15A to 15B), the electrical pulses are voltage pulses between 10 kV and 60 kV or even between 10 kV and 100 kV, for example still of the order of 20 kV (note that these are the voltages between the electrodes). The values ​​to be selected are chosen according, in particular, to the nature of the drain in which the probe must operate and its resistance (too high a voltage or power can result in degradation of the drain). The pulses can have:

[0097] - a duration of the order of a few microseconds, for example 5 ps, more generally for example between 1 ps and 10 ps,

[0098] - and / or the energy delivered per pulse can be between 100 J and 600 J. From a temporal point of view, it can also be indicated that:

[0099] - the time between the application of the voltage and the breakdown (i.e. the formation of the arc between the electrodes of the probe) can be for example of the order of 10 ps; - and / or the complete duration of the arc to evacuate the energy can be of the order of 40 ps;

[0100] - and / or the arc can be effective within 10 ps after breakdown.

[0101] The pulses can therefore have a power which will be between, for example, 10 MW and 60 MW.

[0102] The invention preferably implements the High Power Pulsed (HPP) technology, which makes it possible to compress energy from a quasi-static source into controlled pulses, preferably very dense and very short, more preferably delivering very high power, for example between 10 MW and 60 MW. High Power Pulsed means the compression of energy, coming from a so-called "quasi-static" source, into single-shot pulses or pulses with controlled repetition rates, very dense and very short, thus delivering very high power. Figure 14 illustrates this aspect; in this figure:

[0103] - slow storage of 1 kW of power for 10 seconds is equivalent to 1 kJ of energy;

[0104] - when this energy is restored for a very short time, of the order of 10 ps, ​​the power restored is 1 GW.

[0105] As explained later, the pulse generator includes a capacitor that stores energy in capacitive form. Its charging is slow, from a thousandth of a second to a few tens of seconds. It is carried out via a high-voltage power supply and means (or "tank") of charging. The charging tank protects the high-voltage (HV) power supply from power returns. Once the capacitor is charged, it decouples the low-voltage part from the high-voltage part. The stored energy is then switched through a controlled air spark gap. It allows rapid restitution of energy to the electrodes connected by a coaxial cable.

[0106] In fact, the firing frequency depends on the ability of the HV power supply to charge the power bank sustainably (without reducing the life of the HV power supply). The curves in Figures 15A - 15D illustrate the relationship between firing frequency, power bank charging voltage, and HV power supply power.

[0107] Thus, we see in figures 15A-15B that: - figure 15A: the repetition frequency is between a value slightly greater than 0 Hz (for example 0.1 Hz), and 1 Hz, the power required from the charger evolving between a value slightly greater than 0 kJ / s and 10 kJ / s, for an energy successively worth 2 kJ (22.1 kV, curve la), 5 kJ (35 kV, curve lia), 10 kJ (49.4 kV, curve Ilia);

[0108] - figure 15B: the repetition frequency is between a value slightly greater than 0 Hz (for example 0.1 Hz), and 1 Hz, the power required from the charger varying between a value slightly greater than 0 kJ / s and 10 kJ / s, for an energy successively worth 1.3 kJ (18kV, curve Ib), 5.3 kJ (36kV, curve IIb), 9.5 kJ (48kV, curve II Ib).

[0109] Figures 15C and 15D also give the firing repetition frequency, here between approximately 0.3 Hz and 5 Hz, as a function of the stored energy (figure 15C) and the charging voltage (figure 15D), for a charger power ranging from 25% to 100%.

[0110] The insulator 6 preferably has a dielectric constant greater than that of the medium in which the arc will be produced. The material constituting this insulator 6 is for example based on polymer(s) (polyurethane resistivity range between 10 12 10-minute multiple choice questions 15Qcm). This same material can be used for HT cables.

[0111] Generally speaking, so that the arc occurs on the surface of the insulator, the breakdown voltage of the insulator 6 is chosen to be higher than the maximum "gap" voltage (minimum voltage which allows an arc to be created between the electrodes) of 60 kV or even 100 kV. Therefore, preferably, the breakdown voltage is chosen so that the arc does not form in the insulator; more preferably, it is higher than that of the liquid in which the probe is immersed so that the arc forms in the liquid and not in the insulator.

[0112] Figure 2 schematically represents a probe according to the invention, in a continuous liquid medium 13, for example water. It is equipped with its high-voltage cable 12, for example a coaxial cable, and connected to the HT energy bench 14 (the latter being located outside the liquid medium). As indicated above, this cable 12 will also make it possible to push or pull the probe in the medium 13. The probe is here located facing a wall 1 of a conduit (only the upper part of the longitudinal section of the conduit is shown), for example a drain, on the inner surface of which deposits II1, II2, H3 of solid material, for example calcite, have formed over time. These deposits Hi, H2, H3 are here represented inside the conduit, but deposits II4 can also be made on the outer surface; as already indicated above, these deposits can reduce the permeability of the drainage medium in which the conduit is placed (for example a drain).Deposits (not shown) may also be made in perforations of the wall, for example at the intersection between two conduits, for example perpendicular to each other. According to another aspect, openings, for example slots, may be pierced in the surface of the conduit (particularly in the case of a drain) to allow the flow of liquid, for example water, from the medium to be drained into the drain: if these slots are obstructed, the effectiveness of the drain is reduced accordingly.

[0113] Generally speaking, as we understand from Figure 2, for efficiency reasons, we seek to have the arc as close as possible to the material to be fractured. This is why the electrodes of the probe are preferably provided in a position as far outside as possible of the probe casing (see the configurations described below in connection with Figures 7A-9C). In practice, the probe is brought as close as possible to the material and fired. According to one example, the range of a probe implemented made it possible, in 180 successive high-voltage shots, to fracture calcite to a depth ranging from 5 to 15 cm.

[0114] The application of the voltage pulses will generate an electric arc 18 between the two electrodes 2 and 4, more precisely between the tips 3 and 5. This arc travels from one electrode to the other following the surface of the insulator 6, in the liquid medium 13 which separates them. In the case of a so-called "volume" configuration, the arc is created between the electrodes 2, 4 following the shortest path (an example of this configuration is given below, in connection with figures 10A - 10B). The advantage of the surface configuration is to allow the use of a more moderate arc formation voltage and to reduce the risks of destruction of the insulating material 6 which separates the cathode from the anode: the risk is, in fact, that the "gap" voltage in the water is higher than that at the water / insulator surface; as a result, the insulation throughout the electrical circuit is then designed to have higher resistivity (in order to prevent the arc from forming in the insulation and destroying it).Indeed, this phenomenon is likely to occur at any point presenting a potential insulation weakness from generator 14 to probe 10.

[0115] The electric arc 18 thus created causes vaporization of a portion of the liquid, which creates a pressure wave 19 in the liquid 13, which, in turn, fractures and fragments the material of the deposit(s) Hi, II2, II3, 114 of solid material towards which it is directed, in particular at the planes separating the substrates of different mechanical impedance; this may be the case in particular when the material to be removed has a mechanical impedance different from that of the substrate on which it is deposited or formed, for example, in the case of a calcite concretion formed on a plastic drain (which is flexible): the shock wave can then deform the flexible drain, this deformation detaching the calcite, which will therefore not be fractured, but detached.By moving the probe in the pipe (movement symbolized by arrow 17, for example by the semi-rigid nature of the cable which allows the probe to be pushed), the probe will be positioned successively in front of the different deposits and will be able to fragment them in the manner explained above. This treatment therefore causes a detachment of the deposits Hi, II2, II3, 114 from the wall of the drains not only at the intrados (inside) and extrados (outside) but also at the perforations (not shown in the figure) of the walls 1. The walls 1 do not suffer any damage. In addition, the detached deposits can be fragmented due to their heterogeneous structure, for example linked to seasonal fluctuations which affect the kinetics of their crystallization.

[0116] Thus, the deposits that obstruct a pipe or a drain can be fragmented and detached from the walls 1. The material of the deposits, such as the deposits Hi, II2, II3, which are located inside, on the side of the liquid 13, can then be easily eliminated, for example by the circulation of the liquid 13. Those (II4) which are outside the wall 1 can remain in place but their fragmentation can make it possible to restore the initial permeability of the natural environment. Thanks to this technique, the efficiency of a pipe system, in particular a drainage system, can therefore be restored without degradation of the wall(s) 1.

[0117] Figures 3A - 3B represent an example of a structure of a probe according to the invention, a structure in which the insulating element 6 has a substantially planar shape, the electrodes 2, 4, deposited on a surface of this element 6 having, for their part, a substantially circular shape; more precisely, the electrode 2 has the shape of a disc, while the electrode 4 has the shape of a circular crown whose center is occupied by the electrode 2. This structure will emit pressure waves 19 from a crown-shaped zone (of width d as indicated in Figure 3A) and in a direction substantially perpendicular to the plane of the insulating element 6, parallel to an axis AA' and following a substantially cylindrical distribution around this axis.

[0118] Figures 3C - 3D represent another example of a structure of a probe according to the invention, a structure in which the insulating element 6 has a substantially cylindrical shape, with axis BB', the electrodes 2, 4, deposited on a surface of this element 6 also having this cylindrical shape. This structure will emit pressure waves 19 from a cylinder-shaped zone (with a width d as indicated in Figure 3C) in a direction substantially perpendicular to an axis AA' and in a substantially cylindrical distribution around this axis.

[0119] A probe according to the invention is not limited to these structures of figures 3A-3D, other geometries can be implemented depending on the needs; for example, the element 6 can have a cone-shaped surface (see the example described below in connection with figure 12), as well as the electrodes deposited on this surface, thus producing shock waves equally distributed along a cone.

[0120] More generally, various shapes can be used to direct the shock wave in the desired manner. For example, the profile of the probe can be given a shape comprising one or more concavities or convexities. A reflector 150 can also be provided to direct the waves towards the desired surface, as illustrated in Figure 18. In this figure, the element 6 has a cone-shaped surface, but inverted compared to that of Figure 12. The electrodes deposited on this surface have the same shape. The reflector 150 has, for example, a parabolic generator 151. It makes it possible to direct the shock waves perpendicular to the axis of the probe.

[0121] In the various configurations illustrated, the electrodes are parallel to each other: their ends face each other at a distance d which remains constant over their entire extension. According to one embodiment, illustrated in Figure 4, the HT generator 14 may comprise a high voltage generator 22 connected to an HT capacitor 24. The capacitor 24 is itself part of an RLC circuit (see resistor R sc and inductance L sc ) connected to an HT spark gap 26 fulfilling a switch function. Means 28, for example a relay, forming a short circuit, may be provided in order to ensure safety, to evacuate the energy from the capacitor in the event of a problem, for example linked to a safety issue; the resistor 30 is a leakage resistor.

[0122] The energy bank 14 can be connected to the HT cable 12.

[0123] Figure 5 represents an exemplary embodiment of generator 22, comprising a high voltage charger 32 (for example of the BASIS EUROFEEDBACK brand, ACRX Series model), which makes it possible to charge a capacitor 36. A switch 37 can connect it to a load shedding resistor 38 (Rdump, or “dump load”), the role of which is, if necessary, to discharge the energy bank without causing damage to the capacitors.

[0124] Generator 22 allows:

[0125] - a transfer of electrical energy from the HT 32 charger to the HT 24 capacitor, which allows the capacitors to be charged to voltage Ue. This function is carried out via the charging resistors Rchi (ref 39) and Rch2 (ref 41);

[0126] - to dampen the reverse voltage coming from the load to protect the HT 35 charger. This function is carried out via the RC filter comprising Rch2 and CBdc (ref 36), then the RC filter comprising Rchi and CBdc.

[0127] - dump the energy from the HT capacitor through a dump resistor (Rdump) when a pneumatic cylinder is activated.

[0128] This assembly provides a voltage U e (t) to the capacitor 24 during charging. Figure 6 schematically represents the coaxial cable 12, connected on the one hand to the pulse generator 22, 24 and, on the other hand, to a probe 10, which may be of the type according to the invention.

[0129] Examples of values ​​used are: a) simulation parameters:

[0130] - charging voltage Ue: 18-48 kV;

[0131] - Inter-electrode resistance of the liquid: dx 10 Q;

[0132] - generator inductance: Lg = 1.05 pH;

[0133] - generator resistance: Rg=50mQ; b) cable parameters:

[0134] - cable inductance: Le = 0.094 pH / m;

[0135] - cable resistance: Rc = 3.1 mQ / m;

[0136] - parasitic capacitance: cc= 361 pF / m;

[0137] - arc assistance: 12 mQ / mm (for a 5 mm gap);

[0138] - time before breakdown: Tb = 10 ps.

[0139] When using a device according to the invention:

[0140] - the capacitor 24 is charged by each high voltage pulse generated by the means 22;

[0141] - the means 26 make it possible to discharge the capacity 24 into the coaxial cable 12.

[0142] All of the means described above can be connected to a processing and / or control unit which makes it possible in particular to control the triggering of the high voltage pulses and the triggering of the spark gap 26. This unit also makes it possible to carry out measurements, for example of current and / or voltage, in order to better control the latter. The processing and / or control unit comprises for example a computer or a microcomputer or a microprocessor which makes it possible to implement processing and / or control functions of a device and a method according to the invention. Figures 16A to 16B represent simulations of discharge curves, (at the level of the anergy bench (see figure 6) respectively in voltage Ue and in current i(t) with a coaxial cable 12 of 150 ml, of 8 pF, for voltages ranging from 10 kV to 48 kV (more exactly: 18 kV, 24 kV, 30 kV, 36 kV, 42 kV, 48 kV).

[0143] We can see in these figures that the voltage Ue at the terminal of the energy bench and Ugap at the terminals of the probe are not the same. They are out of phase (RLC circuit between the two measurement points) before the creation of the arc.

[0144] Figure 16C shows the evolution of the Ugap voltage at the probe, again with a 150 ml coaxial cable 12, 8 pF; we see that the voltage decreases abruptly when the arc is triggered, which occurs here at t = 10 ps.

[0145] Figure 16D represents the evolution of the energy discharge of the probe (Earc(t) = Uga p(t)-l (t)-t-Ec(t)): after the end of the arc, there is still signal; in fact, on the basis of the equivalent electrical diagram of the circuit (figure 6), we understand that, once the arc has disappeared (the “arc switch” open), there is still the resistance of the water (Reau with switch closed) which allows the residual energy accumulated in the system to be evacuated.

[0146] Figures 7A and 7B represent an embodiment of a probe according to the invention, of the so-called axial geometry type, Figure 7B representing a view of the disassembled device. This is an embodiment in which each of the electrodes 2, 4 as well as the surface of the insulator 6 which separates these 2 electrodes, have a symmetry of revolution around an axis XX'. An arc triggered between these 2 electrodes also generally has this symmetry around the axis XX'.

[0147] According to this embodiment, the probe comprises a body 50 which can be decomposed into a central part, or body 56, with symmetry of revolution around an axis XX' and one or more other parts 52, which can be removable (they can be fixed, for example by screwing, against or onto the central body 56). The high voltage cable 12 (not visible in these figures) can be introduced into the central part of the body of the probe.

[0148] Electrode 2 faces electrode 4, which can be connected to a ground connection. The device can be equipped with one or more shock wave dampers (which, generated by the probe, propagate both in the liquid and in the body of the probe and can therefore damage the internal components of the latter). A practical solution is to choose the material of the insulator 6 so that it dampens all or part of these shock waves.

[0149] Electrode 2 and / or 4 may be removable; it can therefore be removed and replaced by an electrode having a different diameter, in order to increase or reduce the distance between electrodes 2, 4. Figure 7C shows such a removable electrode 2. The adjustment of the gap voltage for an axial probe configuration can be obtained by modifying the diameter of this central electrode 2.

[0150] The arcs that will be generated between the electrodes 2 and 4 of such a probe will make it possible to generate shock waves in the liquid that will be more particularly emitted in the direction of the axis XX' of the probe. For this reason, this configuration is called "axial" type: the surface of the insulator 6 in contact with the liquid medium is substantially perpendicular to the axis XX'.

[0151] Advantageously, grooves 141, 143 can be made in the electrode 4, between the screwing points 142, 144 of the latter against the central body. These grooves extend radially, from the part of the electrode 4 which is in contact with the insulator 6 to the outside of the probe: these grooves make it possible to eliminate gas, which would result from the interaction between any arc 18 and the liquid 13 in which the probe is immersed. If residual gas, for example in the form of bubbles, stagnated in the inter-electrode zone, it would disturb the operation of the probe because it would modify the electrical properties of the entire system between the electrodes; for this reason, it is preferable to provide one or more lateral grooves 141, 143 for evacuating these gases. Preferably, several of these lateral grooves 141, 143 are provided, arranged symmetrically around the axis XX'.

[0152] As seen in this figure, the probe may have, on the front face, a rounded shape and / or rounded angles which facilitate its movement in a liquid. Figure 8 represents the mechanical flange 52 fixed to the central body 56 (opposite the electrodes 2, 4). This flange makes it possible, for example, to mechanically hold the cable to the probe. The conical shape which it presents at least in part facilitates the withdrawal of the probe from a conduit into which it has been introduced. Figure 9A represents an embodiment of a probe according to the invention of the so-called “parietal” geometry type. This is an embodiment in which each of the electrodes 2, 4, as well as the surface of the insulator 6 which separates these 2 electrodes, are arranged laterally to the probe, while presenting a symmetry of revolution around the axis XX' of the latter.An arc triggered between these two electrodes extends over a certain distance, parallel to the XX' axis and with this symmetry around it.

[0153] References identical to those of figures 7A - 7B designate in these figures 9A-9B elements identical or similar to those already described above. But the electrodes 2, 4 are arranged on the cylindrical lateral part of the body, in the front part and terminate in a dome 58, for example made of polymer material. Here again the electrode 2 and / or 4 may be removable; it can therefore be removed and replaced by an electrode having a different lateral extension, in order to increase or reduce the distance between the electrodes 2, 4. Figure 9C represents such a removable electrode 2. The adjustment of the gap voltage for a parietal probe configuration can be done by modifying the thickness E of this terminal electrode 2.

[0154] The arcs that will be generated between the electrodes 2 and 4 of such a probe will make it possible to generate shock waves in the liquid that will be more particularly emitted perpendicular to the axis XX' of the probe. For this reason, this configuration is called "parietal" type: the surface of the insulator 6 in contact with the liquid medium is substantially cylindrical or conical, or of revolution around XX', parallel or coaxial to the axis XX'.

[0155] In such a structure, the flow of liquid, which flows substantially parallel to the axis XX', makes it possible to eliminate the gases which may result from the interaction between the arc 18, generated between the electrodes 2, 4, and the liquid 13, in which the probe is immersed. But, as in the previous case, grooves may be provided in order to improve the evacuation of these gases. For example, such lateral grooves (not shown in FIGS. 9A-9B) are made in the electrode 4, between the screwing zones 141, 143; they may extend over a part of the central body 56.

[0156] A probe according to the invention is not limited to the configurations described above in connection with Figures 7A - 9C. Such a probe may comprise differently oriented electrodes, in order to reach surfaces which may have a particular orientation in a liquid circulation conduit.

[0157] The distance between the probe and the drain is not controlled. The probe rests on the drain's waterline and is held laterally by the drain. Here, the drain, shaped like a horseshoe (illustrated in Figure 17), has a diameter D of between 11 cm and 15 cm. The probe has a diameter of 10 cm.

[0158] The invention has been described above in the context of a so-called "surface" configuration, in which the electrodes are directly in contact with an insulating surface 6. In another configuration, shown schematically in Figure 10A (side view, in section) and 10B (top view), the ends 3, 5 of the electrodes 2, 4, between which an arc can occur, are not in direct contact with the insulating surface 6: the latter is set back relative to the electrodes. In the configuration shown in Figure 10A, an electrode 2 is in the form of a ring or crown, and another electrode 4, central, is in the form of a pad or disc, arranged in the center of the ring or crown. But other variants can be implemented, without departing from the scope of the present invention. This volume configuration can be applied to the different variants described above in connection with Figures 4-9.

[0159] Whatever the configuration chosen, surface or volume, the ends of the electrodes 2, 4 can have a claw shape, as shown in figure 11A for a surface configuration (top view in [Fig. 11B]): in 2 or 3 directions of space, they extend towards a point-shaped end 3, 5. Electrodes having this shape promote the formation of the arc. The same shape can be applied to the volume configuration.

[0160] As a further variant, shown in Figure 12, the electrodes can be located at different levels, with an insulating material having for example a conical shape. In this figure, the end of the cone has a concave shape, but a convex shape could be produced, allowing the formation of waves with a direction of propagation oblique to the axis of the device. Finally, Figure 13 shows a probe 10 according to the invention, positioned in a drain 1 in which both parietal concretions 111 and axial concretions 11 have formed, which can be eliminated by the probe. The other numerical references are those of the figures previously described.The invention applies to any pipe or conduit in which a fluid or liquid circulates, leading to a deposit of material on the inner and / or outer surface of this pipe or conduit and / or which at least partially blocks one or more orifice(s) made in this conduit and / or the flow section of this conduit, for example at the intersection with another conduit which connects to the 1. er; similarly, the invention applies in the case of deposits, which may originate from the environment in which the pipe or conduit is installed and which may occur on a surface external to this pipe or conduit, which may lead to a reduction in its permeability and / or to a poorer performance of the entire system for the evacuation of the liquid (for example, for a drainage system, the development of concretion in the matrix of the drainage base reduces the permeability thereof; ultimately, the drainage base becomes less efficient upstream of the drains for evacuating water).

Claims

CLAIMS 1. Device for electro-cleaning conduits by indirect attack, comprising: - two electrodes (2, 4) facing each other, applied against an insulating surface (6); - means (14, 22, 24, 26) for generating high voltage electrical pulses; - means (12) for transmitting and applying said pulses between the two electrodes.

2. Device according to claim 1 in which the electrodes (2, 4) are applied against an insulating surface (6) so as to allow the creation of an electric arc (18) on the surface of the insulator which separates the electrodes.

3. Device according to claim 2, comprising a major axis (XX') and in which the insulating surface against which the electrodes are applied is flat and perpendicular to said axis (XX').

4. Device according to claim 2, comprising a major axis (XX') and in which the insulating surface against which the electrodes are applied is of revolution around said axis.

5. Device according to one of claims 1 to 4, the electrodes being spaced apart by a uniform distance or the device comprising means for adjusting this distance (d).

6. Device according to one of claims 1 to 5, further comprising at least one groove (141, 143) for evacuating gas formed by an arc (18) established between the 2 electrodes. L 7. Device according to one of claims 1 to 6, in which means (14, 22, 24, 26) for generating high voltage electrical pulses make it possible to generate power pulses of between 10 MW and 60 MW.

8. Device according to one of claims 1 to 7, in which the means (14, 22, 24, 26) for generating high voltage electrical pulses make it possible to generate high power pulses and / or voltage pulses between 10 kV and 60 kV.

9. Device according to one of claims 1 to 8, further comprising means (6) for damping shock waves.

10. Device according to one of claims 1 to 9, further comprising means (151) forming a reflector for directing the shock waves.

11. Method for electro-cleaning a conduit delimited by at least one wall (1) and containing a liquid (13), said wall having a surface partly covered by at least one deposit (Hi, Hz, H3, H4) of solid material to be eliminated and / or said conduit being at least partially obstructed by at least one deposit of solid material to be eliminated, said method comprising: - positioning a device according to one of claims 1 to 10 in said conduit; - the generation of high voltage electrical pulses and their transmission to the electrodes (2,4), - the formation of an electric arc (18) between the electrodes, on the insulating surface and in the liquid (13), in at least one direction parallel to at least one of the deposits of material to be eliminated.

12. The method of claim 11, wherein the pulses have a power of between 10 MW and 60 MW.

13. Method according to one of claims 11 or 12, in which the electrical pulses are voltage pulses between 10 kV and 60 kV.

14. Method according to one of claims 11 to 13, in which gases formed following the interaction between the liquid (13) and the electric arc (18) are evacuated from the surface of the electro-cleaning device.

15. Method according to one of claims 11 to 14, in which the deposits (Hi, II2, H3, II4) of solid material to be removed are calcite deposits.

16. Method according to one of claims 11 to 15, in which at least one deposit (lli, II2, H3, H4) of solid material to be removed is on an inner surface of the conduit or on an outer surface of the conduit and / or blocks at least part of a flow section of said conduit.

17. Method according to one of claims 11 to 16, in which the conduit is made of plastic or cast iron or ceramic.

18. Method according to one of claims 11 to 17, in which the material of the insulating surface (6) has a dielectric constant greater than that of the liquid (13).

19. Method according to one of claims 11 to 18, wherein the voltage pulses are generated at a rate of at least 0.2 Hz to 1 Hertz.

20. Method according to one of claims 11 to 19, in which the voltage pulses are high power pulses.

Images