METHOD FOR REPAIRING A CONDUCTOR BAR

Abstract

The present invention relates to the field of industrial mechanical maintenance, and more specifically to a method for repairing conductive bars in a system of electrolysis cells arranged in series. The invention relates to a method for repairing conductive bars comprising: - a step of electrically isolating two of the cells (C1, C2) from the electrical circuit (EC), - a step of reducing the intensity of the electric current flowing through said electrical circuit (EC) and all the cells so as to reduce the magnetic field at the conductive bar to be repaired (CBR) to a flux density less than or equal to 0.01 T while continuing electrolysis in the other electrolysis cells besides the first and second electrolysis cells, and - a step of repairing the conductive bar to be repaired (CBR) by welding.The present invention is useful, for example, for repairing conductive bars in an electrical circuit supplying successive electrolysis cells in series, for example, metal synthesis cells, for example, aluminum. Abbreviated figure: [Fig. 2].

Description

Title of the invention: METHOD FOR REPAIRING A CONDUCTIVE BAR Technical field of the invention

[0001] The present invention relates to the field of industrial mechanical maintenance, and more precisely to a method of repairing conductive bars in a system of electrolysis tanks arranged in series.

[0002] The present invention is useful, for example, for the repair of conductive bars of an electrical circuit supplying successive electrolysis tanks in series, for example metal synthesis tanks, for example aluminum. Prior art

[0003] Electrolysis is a process commonly used in the production of metals.

[0004] For economic reasons, the implementation of such a process on an industrial scale may involve the use of several electrolysis tanks connected together by an electrical circuit carrying a high-intensity direct current. For this, the electrical circuit is connected to an electrical substation which transforms the alternating current into direct current so that the electrolysis tanks are functional. The same electrical circuit therefore generally supplies several electrolysis tanks.

[0005] When implementing an electrolysis process, it may happen that one of the electrolysis cells begins to leak, thus projecting a liquid, for example a metal in liquid form, at high temperature onto one of the conductive bars of the electrical circuit. Following such an incident, the conductive bar may be affected by the high-temperature liquid, which may lead to degradation of the conductive bar, or even rupture, which has the effect of disrupting the flow of current in the entire electrical circuit and therefore in the electrolysis cells.

[0006] Welding is generally the technique used to repair metal bars, particularly conductive bars. However, repairing a defective conductive bar is a source of many difficulties, the two main ones being the presence of electric current in the electrical circuit and the magnetic field generated by this current.

[0007] Indeed, although the current may be disturbed, or even not flow through a conductive bar including damage or a break, the intervention of a repairer can be very dangerous because the current can flow through the conductive bar again during the repair if the flow of current is not interrupted. In addition, repair by welding remains extremely difficult because of the magnetic field induced by the passage of current.

[0008] In order to avoid the dangers and the very unlikely success of the welding for the repairer, the repair of a conductive bar included in an electrical circuit carrying a current requires the stopping of the electric current in the circuit, in particular by the complete stopping of the electrical substation supplying the electrical circuit, which therefore causes the stopping of all the electrolysis tanks in series. This stoppage has a very negative economic and industrial impact, for example on the production of metal. The maintenance and restarting operations of the electrolysis tanks are in fact long and laborious and the stopping of electrolysis in all the tanks leads to significant production losses.Furthermore, the complete shutdown of the electrical substation to repair one or more conductor bars also presents a significant risk of explosion associated with the shutdown and restart of transformers in the electrical substation generating high intensity direct current in such a system.

[0009] It has been envisaged in the prior art to stop only the electrolytic cell at which the conductive bar is to be repaired. Unfortunately, this does not allow any repair method to be implemented on the electrical circuit which supplies the set of electrolytic cells in series. Indeed, the adjacent cells always carrying a current generate a magnetic field which disrupts the repair operations of the conductive bar and which leads to poor quality of the repair, in particular when it is a repair by welding.

[0010] There is currently another way to repair conductor bars in the presence of a magnetic field, i.e. without having to shut down the electrical substation, this is laser welding. This technique allows for high quality welding even in strong magnetic fields, and a reduction in the maximum voltage drop evaluated at 10mV per electrolysis cell, i.e. an energy saving of approximately €350k / year. On the other hand, the implementation time compared to normal welding is multiplied by three, i.e. approximately eight hours more compared to the present invention set out below. In addition, the implementation costs are greater than €600k just in direct costs, indirect costs to be expected of €40k, operational costs related to the time for setting up the equipment and its use + €2k / cell, i.e. approximately €100k / year.

[0011] Thus, to date, no method for repairing a conductive bar of an electrical circuit of a series electrolysis cell that is satisfactory in terms of cost or safety for the repair has been proposed. There is therefore a real need to find a method that is both safe for the repairer and does not have the drawbacks of the prior art. Statement of the invention

[0012] The present invention has the precise aim of solving the problems and drawbacks of the prior art by providing a method for repairing a conductive bar, an electrical circuit supplying successive electrolytic cells with a direct electric current in series. The method of the invention advantageously makes it possible to secure the intervention of the repairer, not to shut down the electrical substation, to reduce the repair time of the conductive bar(s) while allowing electrolysis to continue in the majority of the other electrolytic cells. The method according to the invention also allows rapid return to service of the cells adjacent to said conductive bar to be repaired. The method according to the invention is also very easy to implement and very economically advantageous.

[0013] A first object of the present invention is a method for repairing a conductive bar to be repaired of an electrical circuit supplying successive electrolytic cells with a direct electric current in series via conductive bars, said conductive bars being located outside said cells and in contact with them, said electric current generating a magnetic field in particular at the cells and the conductive bars, in which each electrolytic cell is installed in a cell location and each cell comprising: - an electrolysis bath, - an anode connected to the electrical circuit and partially immersed in the electrolysis bath, - a cathode in contact with liquid aluminum - a cathode bar in contact on the one hand with the cathode and on the other hand with a conductive bar, method in which the conductive bar to be repaired in contact with a first tank is adjacent to a second tank which precedes the first tank in the electrical circuit, the first and second tanks themselves being adjacent, said method comprising: - a step of electrical isolation of the first and second tanks of the electrical circuit, - a step of reducing the intensity of the electric current flowing through said electric circuit and all of the tanks so as to reduce the magnetic field at the level of the conductive bar to be repaired to a flux density less than or equal to 0.01 T while continuing the electrolysis in the electrolysis tanks other than the first and second electrolysis tanks, and - a repair step of the conductive bar to be repaired by welding.

[0014] By "an electrical circuit supplying [...] tanks in series" is meant an electrical circuit supplying several tanks positioned successively and carrying the same current.

[0015] By "magnetic field" is meant a region of space subjected to the action of a force originating from magnets, an electric current, as well as the temporal variation of an electric field by electromagnetic induction. In the presence of such a field, various phenomena are observable on materials, such as paramagnetism; diamagnetism and / or ferromagnetism.

[0016] By "electrical isolation step" is meant the breaking of the electrical connection between the electrical circuit and the isolated element of the electrical circuit, for example the first and second electrolytic cell. For example, this may involve the addition and / or removal of short-circuiting or equipotential aluminum shims between the conductive bars of the electrical circuit. These shims allow the current to be diverted so that it no longer passes through the first and second cells. Thus, the current is diverted to the cell that follows the second electrolytic cell.

[0017] By "welding" is meant an operation consisting of assembling at least two elements permanently, while ensuring functional continuity between these elements. The assembly can be carried out by heating causing the fusion of these two elements, by pressure or the combination of the latter. The assembly can be carried out with or without a filler product, for example a material whose melting temperature is of the same order of magnitude as that of the material of the conductive bar to be repaired. This can be, for example, an aluminum wire or equivalent.

[0018] Advantageously, the welding can be carried out by any means known to those skilled in the art, depending in particular on the chemical composition of the conductive bar to be repaired. This may be, for example, a method chosen from oxyacetylene welding, aluminothermic welding, electric resistance welding, electric arc welding with coated electrodes, submerged arc welding, arc welding with non-consumable electrodes, arc welding with consumable electrode wire, semi-automatic welding, orbital welding, laser welding, plasma welding, electron beam welding, friction welding, friction stir welding, thixotropic welding, hybrid welding, electro-gas welding, diffusion welding, explosion welding, magnetic pulse welding, ultrasonic welding and “demineralized water” welding.Preferably, the welding can be carried out by a semi-automatic welding method, more preferably by semi-automatic metal inert gas (MIG) welding.

[0019] Advantageously, the welding repair step can be carried out with a welding pad of a material compatible with the conductive bar to be repaired. Advantageously, the welding pad can comprise at least one metal chosen from steel, copper, chromium, nickel, aluminum, titanium, magnesium, zirconium and any alloy thereof. Preferably, the solder pad may comprise an aluminum alloy.

[0020] Advantageously, the welding plate may comprise an aluminum alloy having a coefficient of linear expansion of from 20.106 to 25.106 °K ', preferably from 23.5.106 to 24.106 “K1. It may be an aluminum marketed by the company Clauser based in Loon Plage in France.

[0021] Advantageously, the welding repair step can be carried out in a time less than or equal to 50 minutes, preferably less than 45 minutes, even more preferably less than 30 minutes.

[0022] Advantageously, during the repair step, the magnetic field at the level of the conductive bar to be repaired can have a flux density less than or equal to 0.01 T.

[0023] Advantageously, the step of isolating the first and second tanks from the electrical circuit can be carried out by adding and / or removing one or more short-circuiting shims and / or one or more equipotential shims in the electrical circuit.

[0024] By "short-circuiting wedge" is meant a wedge allowing a diversion of the electric current. When such a wedge is added or removed in an electrical circuit comprising conductive bars, it is possible to divert the current so that it does not flow through one of these conductive bars, for example, by adding or removing short-circuiting wedges.

[0025] By "equipotential shim" is meant a shim allowing a distribution of the current in an electrical circuit. When such a shim is added in an electrical circuit comprising conductive bars, it is possible to influence and therefore distribute the flux density of the magnetic field at a point in the electrical circuit. Such a shim also makes it possible to avoid instability of the devices, for example electrolytic cells, supplied with current by the electrical circuit comprising said shim.

[0026] The selective addition and / or removal of one or more shims makes it possible to electrically isolate the conductive bar to be repaired and to direct the electric current towards sections of the electrical circuit making it possible to supply the other electrolytic cells. Thus, it is possible to produce one or more welds of better quality since the magnetic field at the conductive bar to be repaired has a low flux density and therefore has less influence on the behavior of the liquid metal when the weld is produced.

[0027] Advantageously, the addition of one or more shims can be carried out in several sub-steps. For example, such an addition can comprise the addition of a first series of one or more shims and the addition of a second series of one or more shims. The second series may have been added as a result of the modifications imposed on the circulation of the current in the electrical circuit by the addition of the first series. Such an addition may be followed by the removal of the first series of one or more shims.

[0028] Advantageously, the step of reducing the intensity of the electric current may comprise a progressive reduction in the intensity of the current to a value less than or equal to 270 kA, preferably less than or equal to 250 kA.

[0029] By "progressive" is meant a controlled decrease in the current intensity, for example, for the fastest possible decrease, for example, in 5 to 10 minutes to reach a value less than or equal to 270 kA. For example, a slower decrease can be achieved in 30 to 45 min to reach a value less than or equal to 270 kA.

[0030] Advantageously, the electrolysis tanks may be aluminum synthesis electrolysis tanks and the electrolysis baths may be aluminum synthesis electrolysis baths. These may be, for example, electrolysis tanks marketed by the company Aluminium Péchiney under the commercial reference AD41.

[0031] Advantageously, the electrolysis baths may comprise cryolite, an excess of aluminum fluoride (A1F3) and calcium fluoride (CaF2). These may be, for example, electrolysis baths described in the book “Understanding the Hall-Heroult Process for Production of Aluminum”, edited by Kai Grjotheim and Halvor Kvande, published by Aluminium-Verlag, Dusseldorf in 1986 (Reference 1).

[0032] Advantageously, the repair method according to the invention may further comprise, between the steps of isolating the first and second tanks and reducing the intensity of the electric current, the following steps in order: - a step of removing the electrolysis bath from the first electrolysis tank; - a step of removing the first electrolysis tank from the tank location; - a step of complete immersion of the anode of the second tank in the electrolysis bath so that it comes into contact with the synthesized metal present at the cathode in said second electrolysis tank, which causes a short circuit isolating the second tank from the electrical circuit.

[0033] Advantageously, the step of removing the electrolysis bath from the first electrolysis cell is implemented for a so-called "pierced" electrolysis cell. For example, it may be a cell for which a flow of aluminum is observed on one of the walls of said cell.

[0034] Advantageously, the repair method according to the invention may further comprise, after the step of repairing the conductive bar to be repaired by welding, the following steps in order: - a step of progressive increase in the current intensity up to a nominal intensity of the electrolysis tanks, - a step of partial emersion of the anode of the second electrolysis tank of the bath electrolysis, - a step of installing a first electrolysis tank in tank replacements, - a step of removing the short-circuiting wedge(s) and / or the equipotential wedge(s) from the electrical circuit, and - a step of reintroducing the electrolysis bath inside the first electrolysis tank.

[0035] The step of removing the shim(s) may be carried out, according to the invention, in several sub-steps. For example, such an addition may comprise the addition of a new series of one or more shims and the removal of the shim(s) added during the step of isolating the first and second tanks. The new series may be added to modify the flow of current in the electrical circuit and allow the removal of the shim(s) added during the step of isolating the first and second tanks. Such removal may be followed by the removal of the new series of one or more shims.

[0036] By "nominal intensity" is meant a maximum current intensity that can be supported by the electrolysis cells in normal operation, without its internal components suffering damage. In particular, the nominal intensity is, preferably, an intensity at which the electrolysis operates, for a given period. This may also be above or below this intensity, within reasonable proportions, so that the internal components of the cell do not suffer damage.

[0037] Advantageously, the repair method according to the invention may further comprise, between the steps of partial emersion of the anode of the second electrolytic cell and of installation of a first electrolytic cell, a step of removal of the short-circuiting shim(s) and / or the equipotential shim(s) of the electrical circuit, so that the second electrolytic cell is no longer isolated from the electrical circuit and the first electrolytic cell remains isolated from the electrical circuit.

[0038] Advantageously, the repair method according to the invention may further comprise, before the step of completely immersing the anode of the second cell in the electrolysis bath, a preliminary step of removing part or all of the electrolysis bath from the second electrolysis cell.

[0039] By "a portion of the electrolysis bath" is meant a sufficient quantity of electrolysis bath to prevent the electrolysis bath from overflowing from the second tank as a result of the anode of the second tank being completely immersed in the electrolysis bath.

[0040] Advantageously, the repair method according to the invention may further comprise, after the step of partial emersion of the anode of the second electrolysis tank from the electrolysis bath, a subsequent step of reintroduction of the bath electrolysis inside the second electrolysis tank.

[0041] Advantageously, all of the steps from the step of removing the electrolysis bath from the first electrolysis cell to the step of reintroducing the electrolysis bath into the first electrolysis cell can be carried out in a time of less than or equal to 120 minutes, preferably 90 minutes.

[0042] Advantageously, all of the steps ranging from the step of reducing the intensity of the electric current flowing through said electric circuit to the step of progressively increasing the intensity of the current up to a nominal intensity of the electrolysis cells can be carried out in a duration of less than or equal to 90 minutes, preferably 80 minutes. Brief description of the figures

[0043] [Fig.l] schematically represents a sectional view of an electrolysis cell (C) comprising aluminum (Al).

[0044] [Fig.2] schematically represents an electrical circuit (CE) comprising a conductive bar to be repaired (BCR) and supplying a system of four cell locations (E0, El, E2, E3) in series comprising the electrolysis cells C0, C2 and C3, the cell Cl having been removed. Said circuit comprising six short-circuiting / equipotential wedges (ccc / cep) to electrically isolate the parts of the electrical circuit (CE) in contact with the cell locations El and E2. EXAMPLES

[0045] Other advantages, aims and particular characteristics of the present invention will emerge from the following examples, given for illustrative and non-limiting purposes.

[0046] In the following examples, the different parameters were measured using the techniques detailed below:

[0047] Measurement of current intensity

[0048] The measurements are carried out using the TORE device from the company ABB, Switzerland / Sweden.

[0049] Measurement of the flux density of a magnetic field

[0050] The measurements are carried out using the VGM (“Vector Gaussmeter Model”) device marketed by the company AlphaLab INC. (USA).

[0051] Example 1: Example of a set of successive electrolysis tanks arranged in series and supplied with current by the same electrical circuit

[0052] This example describes a set of electrolysis tanks supplied by the same electrical circuit comprising conductive bars which can be repaired according to the method of the invention.

[0053] Said conductive bars are located outside said tanks and in contact with them. Said conductive bars are made of 1370-50 aluminum. (marketed by the company Aluminium Pechiney).

[0054] The electrical circuit, supplying successive electrolysis tanks (C) with a high intensity direct electric current, described in this example comprises a conductive bar to be repaired (BCR).

[0055] The series of electrolysis tanks comprising 264 aluminium synthesis electrolysis tanks (marketed by the company Aluminium Pechiney, France, under the commercial reference AP Technology) with a capacity of 25000 L and each tank comprising: - 5T electrolytic bath (be); - 20 anodes (an) connected to the electrical circuit (CE) and partially immersed in the electrolysis bath (be), - 20 cathodes (ca) in contact with liquid aluminum, - Cathode bars (bca) in contact on the one hand with a cathode (ca) and on the other hand with a conductive bar.

[0056] The anodes are held together by a steel structure.

[0057] Each electrolysis bath comprises, in % by weight relative to the total weight of the electrolysis bath, 80% cryolite (marketed by the company Aluminium Dunkerque under the reference Bain Broyé Lingoté), 11% excess aluminium fluoride (marketed by the company Fluorsid under the commercial reference Aluminium Fluoride) and 4.5% calcium fluoride (marketed by the company EMSA Technologia Quimica under the commercial reference Bricoal).

[0058] The conductive bar to be repaired (BCR) in contact with a first tank (Cl) is adjacent to a second tank (C2) which precedes the first tank in the electrical circuit, the first and second tanks themselves being adjacent.

[0059] Example 2: Example of implementation of the method of the invention on a device as described in example 1

[0060] This example describes a method which can be implemented for the repair of a conductive bar to be repaired (BCR) in an electrical circuit (CE) supplying a set of electrolysis cells (C).

[0061] The repair method implemented comprises the following steps: - a step of removing the electrolysis bath from the first electrolysis tank (Cl). The withdrawal is carried out in a pocket to receive the electrolysis bath, by creating a vacuum in the pocket, - a step of removing the first electrolysis tank (Cl) from the tank location (El). This removal is done by means of an overhead crane. - a step of complete immersion of the anodes of the second tank (C2) in the electrolysis bath by lowering the steel structure so that they come into contact with the synthesized aluminum present at the level of the cathodes in said second tank electrolysis (C2) which causes a short circuit isolating the second tank (C2) from the electrical circuit (CE), - addition of 6 short-circuiting shims (ccc) and 2 equipotential shims (cep) in the electrical circuit (CE) at the level of the adjacent conductive bars preceding the first and second tanks (Cl, C2) so as to electrically isolate the first and second tanks (Cl, C2) from the electrical circuit (CE), - a step of reducing the intensity of the electric current flowing through said electric circuit (CE) to a value equal to 250 kA, thus reducing the magnetic field at the level of the conductive bar to be repaired (BCR) to a flux density equal to 0.01 T while continuing the electrolysis in the electrolysis tanks other than the first and second electrolysis tanks, and - a step of repairing the conductive bar to be repaired (BCR) by semi-automatic MIG welding (metal under inert gas) with welding plates comprising an aluminum alloy 1370-50, marketed by PCP ALUMINIUM (Canada) having a linear expansion coefficient of 23.8.106 °K ', - a step of progressive increase in current intensity up to a value equal to 390 kA, - a step of partial emergence of the anodes of the second electrolysis tank (C2) from the electrolysis bath (be) by raising the steel superstructure, - a step of removing the short-circuiting shims (ccc) and the equipotential shims (cep) from the electrical circuit (CE), so that the second electrolytic cell (C2) is no longer isolated from the electrical circuit (CE) and the first electrolytic cell (Cl) remains isolated from the electrical circuit, - a step of installing a new first electrolysis cell (Cl) in cell replacements (El) implemented using a rolling point allowing the deposit of the new first electrolysis cell (Cl), the production of welds to connect said first cell to the electrical circuit, and the installation of a steel superstructure also transported by overhead crane, - a step of removing the short-circuiting wedges (ccc) and the equipotential wedges (cep) remaining from the electrical circuit (CE), and - a step of reintroducing the electrolysis bath (be) inside the first electrolysis tank (Cl), from the pockets.

[0062] This process has been implemented on several occasions, and has notably made it possible to successfully repair the following three bars: Bl, B2 and B3.

[0063] Table 1: Duration of implementation of a method for repairing a conductive bar to be repaired (BCR) according to the invention. [Tables 1] Conductor bars to be repaired Tl (min) T2 (min) B1 50 80 B2 35 56 B3 46 61 Tl: Implementation time of the welding repair step described in Example 1; and T2: Implementation time of all the steps described in example 1, ranging from the step of reducing the intensity of the electric current flowing through said electric circuit (CE) to the step of progressively increasing the intensity of the current up to a nominal intensity of the electrolysis cells (CE).

[0064] This process has an average repair time per weld in the presence of a magnetic field of 45 minutes.

[0065] Furthermore, this method has an average duration of implementation of a method for repairing a conductive bar in the presence of a magnetic field ranging from the step of reducing the intensity of the electric current flowing through said electric circuit to the step of progressively increasing the intensity of the current up to a nominal intensity of the electrolysis cells of 66 minutes.

[0066] The method of the invention makes it possible to repair damaged conductive bars in a very short time, while ensuring the safety of the repairer, avoiding the shutdown of the electrical substation and allowing electrolysis to continue in the majority of other electrolysis tanks. In addition, the method according to the invention is also very easy to implement and very economically attractive. Bibliographic references

[0067] Référence 1: K. Grjotheim, H. Kvande, Understanding the Hall-Heroult Process for Production of Aluminium ; Aluminium-Verlag, Dusseldorf, 1986

Claims

Claims

1. Method for repairing a conductive bar to be repaired (BCR) of an electrical circuit (CE) supplying successive electrolysis cells (C) with a direct electric current in series via conductive bars, said conductive bars being located outside said cells and in contact with them, said electric current generating a magnetic field in particular at the level of the cells and the conductive bars, in which each electrolysis cell is installed in a cell location (EO, El, E2, E3) and each cell comprising: - an electrolysis bath (be), - an anode (an) connected to the electrical circuit (CE) and partially immersed in the electrolysis bath (be), - a cathode (ca) in contact with the liquid aluminum, - a cathode bar (bca) in contact on the one hand with the cathode (ca) and on the other hand with a conductive bar,method in which the conductive bar to be repaired (BCR) in contact with a first tank (Cl) is adjacent to a second tank which precedes the first tank in the electrical circuit, the first and second tanks themselves being adjacent, said method comprising: - a step of electrically isolating the first and second tanks (Cl, C2) from the electrical circuit (CE), - a step of reducing the intensity of the electric current flowing through said electrical circuit (CE) and all the tanks so as to reduce the magnetic field at the conductive bar to be repaired (BCR) to a flux density less than or equal to 0.01 T while continuing the electrolysis in the electrolysis tanks other than the first and second electrolysis tanks, and - a step of repairing the conductive bar to be repaired (BCR) by welding.,

2. A repair method according to claim 1, wherein the soldering repair step is carried out with a solder pad of a material compatible with the conductive bar to be repaired (BCR).

3. A repair method according to claim 2, wherein the solder pad comprises an aluminum alloy having a coefficient of linear expansion of 20.106 to 25.106 °K '.

4. A repair method according to any one of claims 1 to 3, in which the step of isolating the first and second tanks (Cl, C2) from the electrical circuit (CE) is carried out by adding and / or removing one or more short-circuiting shims (ccc) and / or one or more equipotential shims (cep) in the electrical circuit (CE).

5. A repair method according to any one of claims 1 to 4, wherein the step of reducing the intensity of the electric current comprises a progressive decrease in the intensity of the current to a value less than or equal to 270 kA.

6. A repair method according to any one of claims 1 to 5, wherein the electrolytic cells (C) are aluminum synthesis electrolytic cells and the electrolytic baths (be) are aluminum synthesis electrolytic baths.

7. A repair method according to any one of claims 1 to 6, wherein the electrolysis baths (be) comprise cryolite, excess aluminum fluoride (A1F3) and calcium fluoride (CaF2).

8. A repair method according to claim 6 or 7 further comprising, between the steps of isolating the first and second tanks (Cl, C2) and reducing the intensity of the electric current, in order the following steps: - a step of removing the electrolysis bath (be) from the first electrolysis tank (Cl), - a step of removing the first electrolysis tank (Cl) from the tank location (El), - a step of completely immersing the anode (an) of the second tank (C2) in the electrolysis bath (be) so that it comes into contact with the synthesized metal present at the cathode (ca) in said second electrolysis tank (C2) which causes a short circuit isolating the second tank (C2) from the electrical circuit (CE).

9. Repair method according to claim 8 further comprising, after the step of repairing the conductive bar to be repaired (BCR) by welding, in order the following steps: - a step of progressively increasing the intensity of the current up to a nominal intensity of the electrolytic cells (C), - a step of partial emergence of the anode (an) of the second electrolytic cell (C2) from the electrolytic bath (be), - a step of placing a first electrolytic cell (Cl) in cell replacements (El), - a step of removing the short-circuiting shim(s) (ccc) and / or the equipotential wedge(s) (cep) of the electrical circuit (CE), and - a step of reintroducing the electrolysis bath (be) inside the first electrolysis tank (Cl).

10. Repair method according to claim 9, further comprising, between the steps of partial emersion of the anode (an) of the second electrolytic cell (C2) and of placing a first electrolytic cell (Cl), a step of removing the short-circuiting shim(s) (ccc) and / or the equipotential shim(s) (cep) from the electrical circuit (CE), so that the second electrolytic cell (C2) is no longer isolated from the electrical circuit (CE) and the first electrolytic cell (Cl) remains isolated from the electrical circuit.

11. A repair method according to any one of claims 8 to 10, further comprising, before the step of completely immersing the anode (an) of the second cell (C2) in the electrolysis bath (be), a preliminary step of removing part or all of the electrolysis bath (be) from the second electrolysis cell (C2).

12. Repair method according to claim 11, further comprising, after the step of partially emerging the anode (an) of the second electrolysis tank (C2) from the electrolysis bath (be), a subsequent step of reintroducing the electrolysis bath (be) inside the second electrolysis tank (C2).

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