Casting method for conductor joints of extra-high voltage cables

Abstract

The present invention discloses a casting method for a conductor joint of an extra-high voltage cable, which includes the following steps: taking two cables to be welded, retaining the conductor core wires at one end of the two cables to be welded, obliquely cutting the welding ends of the conductor core wires, taking a quartz tube, a quartz funnel is connected to the upper end of the middle part of the quartz tube, inserting the welding ends of the two conductor core wires into the quartz tube from both ends of the quartz tube respectively, and abutting against each other to form a V-shaped groove, pouring the welding metal liquid into the quartz funnel until the V-shaped groove is filled and saturated with the welding metal liquid, heating up to fuse the conductor core wires with the welding metal liquid, performing water cooling on the surface of the quartz tube, after completely cooling and shaping, knocking the quartz tube to pieces, grinding and processing the welded conductor core wires, and repairing the outer layer of the conductor core wires to complete the welding. The present invention provides a casting method for a conductor joint of an extra-high voltage cable with high connection quality, low operation difficulty and stable connection quality.

Description

Technical Field

[0001] The present invention relates to the field of cables, and more specifically to a casting method for the conductor joints of extra-high voltage cables. Background Art

[0002] With the rapid development of China's economy, the social goal of providing electricity for all has been achieved, and power supply is ensured even in some remote areas. During the process of long-distance power supply, it is necessary to lay extra-high voltage cables over long distances. However, due to the limitations in the production and transportation of extra-high voltage cables, the length of extra-high voltage cables is limited, making it difficult to achieve the goal of laying a single extra-high voltage cable throughout the entire route. Therefore, it is necessary to splice extra-high voltage cables; and during the use of extra-high voltage cables, factors such as high-voltage breakdown and environmental damage can easily cause cable damage. Therefore, cable repair operations are required. After cutting off the damaged area of the extra-high voltage cable, it is then necessary to make a connection.

[0003] Traditional methods for connecting extra-high voltage cables involve arranging two sections of extra-high voltage cables opposite each other and then using methods such as argon arc welding, oxyacetylene welding, or explosion welding for welding and fixing. However, these welding methods have the following disadvantages:

[0004] 1. Since the conductor core is composed of multiple metal conductor wires twisted together, there are many gaps between the metal conductor wires, so a large number of pores are likely to be generated during the welding process.

[0005] 2. During the welding process, the temperatures of these welding methods are relatively high, which easily causes overheating of the conductor, serious annealing of the metal conductor wires, and damage to both the semiconductive layer and the insulating layer of the extra-high voltage cable.

[0006] 3. In explosion welding, due to the limitations of the welding rod, cat's eyes are easily formed during the welding process, and impurities in the welding are likely to mix into the welded area; at the same time, it is difficult for the welding rod to meet the various electrical and mechanical properties of the extra-high voltage cable conductor.

[0007] 4. These welding methods have high requirements for operation. The operation level of the operator will directly affect the welding quality, and at the same time, the stability of the welding is difficult to guarantee, with large fluctuations. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a casting method for the conductor joints of extra-high voltage cables with high connection quality, low operation difficulty, and stable connection quality.

[0009] The technical solution adopted by the present invention to solve the above problems is a casting method for the conductor joints of extra-high voltage cables, which includes the following steps:

[0010] S1: Take two cables to be welded. Remove the outer structure of the conductor cores at the ends to be welded on the two cables, and only keep the conductor cores.

[0011] S2: Obliquely cut the welding ends of the conductor cores. When the welding ends of the two conductor cores are abutted, a V-shaped groove is formed.

[0012] S3: Take a quartz tube with a diameter equal to the wire diameter of the conductor core. A quartz funnel is connected to the upper end of the middle part of the quartz tube.

[0013] S4: Insert the welding ends of the two conductor cores into the quartz tube from both ends of the quartz tube respectively. The welding ends of the two conductor cores are abutted to form a V-shaped groove, and the V-shaped groove is located below the quartz funnel.

[0014] S5: Melt the welding metal liquid.

[0015] S6: Preheat the quartz tube and the quartz funnel.

[0016] S7: Pour the welding metal liquid into the quartz funnel until the V-shaped groove is filled and saturated with the welding metal liquid.

[0017] S8: Raise the temperature, heat the quartz tube and the quartz funnel, and melt the conductor cores at the welding ends to fuse the conductor cores with the welding metal liquid.

[0018] S9: Wait until the fusion of the conductor cores and the welding metal liquid is completed, and then stop heating.

[0019] S10: Cool down the surface of the quartz tube by water cooling.

[0020] S11: After the conductor cores and the welding metal liquid are completely cooled and shaped, break the quartz tube.

[0021] S12: Grind and process the welded conductor cores.

[0022] S13: Repair the outer layer of the conductor cores.

[0023] S14: Complete the cable welding.

[0024] Compared with the prior art, the advantages of the present invention are as follows: The welding method of the present invention uses a quartz tube as a connection mold. The structure finally formed by this welding method is stable, independent of the operation level of the operator. As long as the integrity of the operation is ensured, the welding quality can be guaranteed, thereby ensuring the connection quality of the cable.

[0025] In steps S2 - S4, it can not only ensure that the welding molten metal can smoothly flow into the quartz tube, but also enable the welding molten metal to make full contact with the metal conductor wires in the conductor cores at both ends, so that each metal conductor wire is connected. At the same time, the welding ends of the conductor cores are inclined cut to ensure that each metal conductor wire can be melted, guaranteeing the connection quality. If a planar structure is adopted, the metal conductor wires in the central region are less heated, and the melting condition will be significantly lower than that of the outer - ring metal conductor wires;

[0026] In step S5, the welding molten metal can directly use the same material as the metal conductor wire for welding, or a modifier can be added to the welding molten metal to increase the electrical and mechanical properties of the welding area, thereby ensuring the welding quality and even enhancing the forming quality of the cable at the welding point, avoiding repeated damage at this point;

[0027] In step S6, it can ensure the fluidity of the welding molten metal in the quartz funnel and the quartz tube, avoiding premature solidification and affecting the welding quality;

[0028] In steps S7 - S10, the welding operation of the two - section conductor cores is completed;

[0029] In step S11, the detachment of the quartz tube is completed. First, the price of the quartz tube is low and it can be used as a disposable mold without worrying about the reuse problem of the quartz tube. At the same time, the traditional split - type mold is prone to form a splicing seam at the joint. During the heating process, the splicing seam is prone to deformation, which is not conducive to the high - quality forming of the casting welding. Moreover, there are more processes and it is more complex, affecting the welding efficiency;

[0030] The reason for using the quartz tube as a mold is also that the melting point of the quartz tube is higher than that of the conventional metal conductor wire. While the conventional metal conductor wire is melted, the quartz tube will not deform. At the same time, the quartz tube is a transparent tube, which is easy to observe the melting connection state inside the quartz tube, better control the melting duration, and guarantee the welding quality.

[0031] As an improvement of the present invention, the material of the conductor core is copper, the raw material of the welding molten metal is purple copper. In step S6, the preheating temperature is 1000 - 1100 °C, and in step S8, the heating temperature is 1200 - 1300 °C. Through this improvement, the melting point of the quartz tube is 1713 °C, the softening temperature is 1630 °C, the melting point of copper is 1083 °C. The preheating temperature ensures the fluidity of the welding molten metal in the quartz funnel and the quartz tube, and the heating temperature ensures the melting and mixing connection of the welding molten metal and the conductor core. At the same time, the temperature is limited to avoid severe annealing of the conductor core.

[0032] As an improvement of the present invention, the conductor core wire material is aluminum, and the raw material of the welding metal liquid is conductive aluminum alloy. In step S6, the preheating temperature is 600 - 700 °C, and in step S8, the heating temperature is 1200 - 1300 °C. Through this improvement, the melting point of the quartz tube is 1713 °C, and the softening temperature is 1630 °C. Aluminum has a melting point of 660 °C. The preheating temperature ensures the fluidity of the welding metal liquid in the quartz funnel and the quartz tube, and the heating temperature ensures the melting and mixing connection of the welding metal liquid and the conductor core wire. At the same time, the temperature is limited to avoid serious annealing of the conductor core wire.

[0033] As an improvement of the present invention, in step S7, it further includes step S7.1: performing gap mud sealing between the quartz tube and the conductor core wire at both ends of the quartz tube. Through this improvement, when the quartz tube is sleeved on the conductor core wire, there is a dimensional deviation between the diameter of the quartz tube and the wire diameter of the conductor core wire, and the conductor core wire is composed of metal conductor wires twisted together, making it easy to form a gap between the quartz tube and the conductor core wire. The gap at the end is sealed by mud sealing, while the gap between the metal conductor wires does not need to be sealed. After twisting, the gap is small and long, and the welding metal liquid is not easy to penetrate through the gap between the metal conductor wires. Mud sealing not only has easily obtainable and cheap materials, or even costs nothing, but also has high sealing effectiveness. After the welding of the conductor core wire is completed, the mud sealing can be dried and cleaned, and it is not easy to have residues, which will not affect the use quality of the conductor core wire. It is the best material for short-term sealing with the conductor core wire.

[0034] As an improvement of the present invention, in step S7, it further includes step S7.2: there is an overflow amount of the welding metal liquid in the quartz funnel. Through this improvement, the fullness of the filling of the welding metal liquid is ensured.

[0035] As an improvement of the present invention, in step S7, it further includes step S7.3: using a tuning fork resonance to reciprocate around the outside of the quartz tube until no bubbles are generated. Through this improvement, the bubbles in the welding metal liquid are eliminated to ensure the welding quality. At the same time, the overflow welding metal liquid in the quartz funnel can fill the space of the bubbles.

[0036] As an improvement of the present invention, in step S8, it further includes step S8.1: using a tuning fork resonance to reciprocate around the outside of the quartz tube until no bubbles are generated. Through this improvement, the bubbles formed by the gaps between the original metal conductor wires in the molten state are eliminated to ensure the welding quality. At the same time, the overflow welding metal liquid in the quartz funnel can fill the space of the bubbles.

[0037] As an improvement of the present invention, after step S9 is completed, it further includes step S9.1: heating the mud sealing until the mud sealing is dried and cracked, and cleaning the mud sealing. Through this improvement, the removal of the mud sealing is realized.

[0038] As an improvement of the present invention, the length of the quartz tube is not less than eight times the wire diameter of the conductor core wire. Through this improvement, during the melting process, only the welding end needs to be melted, but the connection stability of the quartz tube still needs to be ensured. It is necessary to ensure the connection and fixation of the non-molten section of the quartz tube and the conductor core wire, so the length of the quartz tube needs to be relatively long.

[0039] As an improvement of the present invention, a water-cooled tube for cooling the quartz tube and the conductor core wire is wound around the connection part of the end of the quartz tube and the conductor core wire. Through this improvement, when the welding metal liquid or the molten metal conductor wire moves towards the end of the quartz tube, it can be solidified in time, and the diffusion of heat can also be blocked, restricting the heat in the welding area and preventing the metal conductor wire from heating up over a large area, causing damage to the semiconductive tape and the insulating layer of the cable. Brief Description of the Drawings

[0040] Figure 1 It is a schematic diagram of the overall sectional structure when injecting welding metal liquid into the quartz tube of the present invention.

[0041] Figure 2 It is a schematic diagram of the overall sectional structure when melting the welding end of the conductor core wire of the present invention.

[0042] Figure 3 It is a schematic diagram of the welded and formed structure of the conductor core wire of the present invention.

[0043] Figure 4 It is an enlarged schematic diagram of the connection part between the quartz tube and the quartz funnel of the present invention.

[0044] As shown in the figure: 1. Cable, 1.1 Conductor core wire, 2. V-shaped groove, 3. Quartz tube, 3.1 Exhaust slope, 4. Quartz funnel, 5. Clay seal, 6. Electromagnetic heater, 7. Tuning fork, 8. Water-cooled tube. Detailed Description of the Embodiment

[0045] The embodiments of the present invention will be further described below with reference to the drawings.

[0046] As Figures 1-3 shown, a casting method for a conductor joint of an extra-high voltage cable includes the following steps:

[0047] S1: Take two cables 1 to be welded, and remove the outer structure of the conductor core wire 1.1 at the welding ends of the two cables 1, only retaining the conductor core wire 1.1;

[0048] S2: Obliquely cut the welding ends of the conductor core wires 1.1. When the welding ends of the two conductor core wires 1.1 abut against each other, a V-shaped groove 2 is formed;

[0049] S3: Take a quartz tube with a diameter equal to that of the conductor core wire 1.1. A quartz funnel 4 is connected to the upper end of the middle part of the quartz tube;

[0050] S4: Insert the welding ends of the two sections of the conductor core wire 1.1 into the quartz tube 3 from both ends of the quartz tube 3 respectively. The welding ends of the two sections of the conductor core wire 1.1 abut against each other to form a V-shaped groove 2, and the V-shaped groove 2 is arranged below the quartz funnel 4;

[0051] S5: Melt the welding metal liquid;

[0052] S6: Preheat the quartz tube 3 and the quartz funnel 4;

[0053] S7: Pour the welding metal liquid into the quartz funnel 4 until the V-shaped groove 2 is filled and saturated with the welding metal liquid;

[0054] S7.1: Perform mud sealing 5 between the quartz tube 3 and the conductor core wire 1.1 at both ends of the quartz tube 3;

[0055] S7.2: There is an overflow amount of the welding metal liquid in the quartz funnel 4;

[0056] S7.3: Use a tuning fork 7 to resonate and reciprocate around the outside of the quartz tube 3 until no bubbles are generated;

[0057] S8: Raise the temperature, heat the quartz tube 3 and the quartz funnel 4, and melt the conductor core wire 1.1 at the welding end to fuse the conductor core wire 1.1 with the welding metal liquid;

[0058] S8.1: Use a tuning fork 7 to resonate and reciprocate around the outside of the quartz tube 3 until no bubbles are generated;

[0059] S9: Wait until the fusion of the conductor core wire 1.1 and the welding metal liquid is completed, and stop heating;

[0060] S9.1: Heat the mud sealing 5 until the mud sealing 5 is dried and cracked, and clean the mud sealing 5;

[0061] S10: Perform water cooling on the surface of the quartz tube 3;

[0062] S11: After the conductor core wire 1.1 and the welding metal liquid are completely cooled and shaped, break the quartz tube 3;

[0063] S12: Grind and process the welded conductor core wire 1.1;

[0064] S13: Repair the outer layer of the conductor core wire 1.1;

[0065] S14: Complete the welding of the cable 1.

[0066] When the material of the conductor core wire 1.1 is copper and the raw material of the welding metal liquid is red copper, in step S6, the preheating temperature is 1000~1100 °C, and in step S8, the heating temperature is 1200~1300 °C.

[0067] When the material of the conductor core wire 1.1 is aluminum and the raw material of the welding metal liquid is conductive aluminum alloy, in step S6, the preheating temperature is 600~700 °C, and in step S8, the heating temperature is 1200~1300 °C.

[0068] A welding device for implementing the casting method of the ultra-high voltage cable conductor joint includes a quartz tube 3, a quartz funnel 4, a mud seal 5, an electromagnetic heater 6 and a tuning fork 7.

[0069] The diameter of the quartz tube 3 is equal to the wire diameter of the conductor core wire 1.1, and the length of the quartz tube 3 is not less than eight times the wire diameter of the conductor core wire 1.1, that is, the end of the conductor core wire 1.1 to be welded needs to be inserted into the quartz tube 3 at least a distance of four times the wire diameter of the conductor core wire 1.1. The conductor core wire 1.1 inserted into the quartz tube 3 is divided into four processing sections. From the welding end of the conductor core wire 1.1 to the direction away from the other conductor core wire 1.1, they are the inclined cutting section, the melting section, the buffer section, and the cooling section in turn. The inclined cutting section is used to perform inclined cutting on the welding end of the conductor core wire 1.1 to ensure that the metal conductor wires in the conductor core wire 1.1 are in full contact with the welding metal liquid, so that each metal conductor wire is connected, and at the same time, it is ensured that each metal conductor wire can be melted to ensure the connection quality; the melting section melts the conductor core wire 1.1 through the electromagnetic heater 6 to ensure the full fusion of the conductor core wire 1.1 and the welding metal liquid to ensure the welding quality; the buffer section is arranged between the melting section and the cooling section to provide a temperature buffer space to avoid the conductor core wire 1.1 from undergoing a temperature change from extremely hot to extremely cold, causing a serious annealing reaction, which is not conducive to the electrical performance and mechanical performance stability of the conductor core wire 1.1; the cooling section is used to cool down the remaining temperature diffused from the welded melt, block the diffusion of heat, limit the heat in the welding area, avoid the large-scale temperature rise of the metal conductor wires, and cause damage to the semiconductive tape and insulation layer of the cable 1. At the same time, when the welding metal liquid or the molten metal conductor wire moves towards the end of the quartz tube 3, the cooling section can be solidified in time to avoid the long-distance diffusion of the molten welding metal liquid or the molten metal conductor wire.

[0070] As Figure 1 、 Figure 2As shown, a water-cooling pipe 8 for cooling the quartz tube 3 and the conductor core wire 1.1 is wound around the connection between the end of the quartz tube 3 and the conductor core wire 1.1 to form a cooling section inside the quartz tube 3. The water-cooling pipe 8 is wound around the end region of the quartz tube 3 and the region where the conductor core wire 1.1 just exits the quartz tube 3 respectively, and the water-cooling pipes 8 in the two regions are arranged at both ends of the mud seal 5. First, the water-cooling pipe 8 wound around the end region of the quartz tube 3 indirectly cools the conductor core wire 1.1 through the quartz tube 3 in the radial direction, while the water-cooling pipe 8 wound around the region where the conductor core wire 1.1 just exits the quartz tube 3 directly cools the conductor core wire 1.1 in the axial direction of the conductor core wire 1.1, thereby improving the effectiveness of cooling and ensuring the cooling effect. At the same time, because the water-cooling pipes 8 in the two regions are arranged at both ends of the mud seal 5 respectively, it can fully block the influence of high temperature on the mud seal 5 during steps S6 - S8, thereby slowing down the drying process of the mud seal 5 in steps S6 - S8 and ensuring the effectiveness of the mud seal 5. A blocking air pressure can be formed in the gap between the quartz tube 3 and the conductor core wire 1.1, effectively preventing the molten conductor core wire 1.1 of the welding metal liquid from leaking out through the gap between the quartz tube 3 and the conductor core wire 1.1. And in step S9.1, only low-temperature heating at 100 - 200 °C is required to clean the mud seal 5 structure layer by layer, and it will not affect the electrical performance and mechanical performance of the conductor core wire 1.1.

[0071] In step S10, the water-cooling process does not rely solely on the water-cooling pipe 8 wound around the quartz tube 3 and the conductor core wire 1.1 for water-cooling. Instead, after removing the electromagnetic heater 6, a new water-cooling pipe is wound around the quartz tube 3 for co-cooling with the water-cooling pipe 8.

[0072] The mud seal 5 is a structure fixed by soil.

[0073] The electromagnetic heater 6 is a conventional device. In the present invention, it only needs to ensure that the electromagnetic heater 6 fully covers the regions of the quartz tube 3 where the conductor core wire 1.1 is melted, the welding metal liquid, and the quartz funnel 4 for stable and uniform heating.

[0074] The tuning fork 7 is a conventional tuning fork. It only needs to select a tuning fork 7 closer to the resonance frequency of the conductor core wire 1.1 according to the material of the conductor core wire 1.1. Then, during the execution of steps S7.3 and 8.1, the main concentrated region is in the melting region of the conductor core wire 1.1. If there are bubbles in the welding metal liquid and the molten conductor core wire 1.1 metal liquid, the bubbles will float up during the resonance process and complete an exchange with the welding metal liquid overflowing from the quartz funnel 4, thereby ensuring the high-quality formation of the welded conductor without bubbles.

[0075] As Figure 4As shown, in order to ensure that the bubbles are quickly exchanged with the welding molten metal overflowing from the quartz funnel 4, an exhaust slope 3.1 is provided at the connection between the quartz tube 3 and the quartz funnel 4. When the bubbles float up and collide with the exhaust slope 3.1, the bubbles can quickly move toward the quartz funnel 4 with the vibration to complete the exchange with the welding molten metal overflowing from the quartz funnel 4. The conical structure formed by the exhaust slope 3.1 can be eliminated in step S12.

[0076] Through the design of the present invention, a method for casting a conductor joint of an ultra-high voltage cable is provided, which has high welding quality, low operation difficulty and stable connection quality for the conductor core wire 1.1 of the cable 1, eliminates welding pores, cat's eyes, impurities and other undesirable welding phenomena in the traditional welding process, and avoids severe annealing reaction caused by welding and damage to other structures of the cable 1. In addition, because the quartz tube 3 is a transparent tube, the melting state of the conductor core wire 1.1 and the welding progress can be monitored at any time, thereby ensuring efficient and high-quality completion of welding.

[0077] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. All changes made within the scope of protection of the independent claims of the present invention are within the scope of protection of the present invention.

Claims

1. A method for casting an ultra-high voltage cable conductor joint, characterized in that: The following steps are involved: S1: Take two sections of cable (1) to be welded, cut off the outer structure of the conductor core wire (1.1) at one end of the two sections of cable (1) to be welded, and only retain the conductor core wire (1.1); S2: The welding end of the conductor core wire (1.1) is cut obliquely, and when the welding ends of two sections of the conductor core wire (1.1) are butted against each other, a V-shaped groove (2) is formed; S3: Take a quartz tube (3) with a diameter equal to the diameter of the conductor core wire (1.1), a quartz funnel (4) is connected to the middle upper end of the quartz tube (3), and the length of the quartz tube (3) is not less than eight times the diameter of the conductor core wire (1.1); S4: inserting the welding ends of the two conductor core wires (1.1) into the quartz tube (3) from both ends of the quartz tube (3), respectively, the welding ends of the two conductor core wires (1.1) abut against each other to form a V-shaped groove (2), and the V-shaped groove (2) is arranged below the quartz funnel (4); S5: molten welding metal; S6: preheating the quartz tube (3) and the quartz funnel (4); S7: pouring the welding metal liquid into the quartz funnel (4) until the welding metal liquid fills the V-shaped groove (2) to saturation; S7.1: Seal the gap between the quartz tube (3) and the conductor core wire (1.1) with mud (5) at both ends of the quartz tube (3); S8: raising the temperature to heat the quartz tube (3) and the quartz funnel (4) and melt the conductor core wire (1.1) at the welding end, so that the conductor core wire (1.1) and the welding metal liquid are fused; S9: When the conductor core wire (1.1) and the welding metal liquid are completely fused, stop heating; S10: A water cooling tube (8) for cooling the quartz tube (3) and the conductor core wire (1.1) is wound around the connection between the end of the quartz tube (3) and the conductor core wire (1.1). The water cooling tube (8) is respectively wound around the end region of the quartz tube (3) and the region where the conductor core wire (1.1) has just left the quartz tube (3). The water cooling tubes (8) in the two regions are respectively arranged at both ends of the mud seal (5) to cool the surface of the quartz tube (3) by water. S11: After the conductor core wire (1.1) and the welding metal liquid are completely cooled and shaped, the quartz tube (3) is broken; S12: Grinding the welded conductor core wire (1.1); S13: Repair the outer layer of the conductor core wire (1.1); S14: Complete the welding of the cable (1).

2. The method for casting an ultra-high voltage cable conductor joint according to claim 1, characterized in that: The conductor core wire (1.1) is made of copper, the raw material of the welding molten metal is red copper, in step S6, the preheating temperature is 1000-1100° C., and in step S8, the heating temperature is 1200-1300° C.

3. The method for casting an ultra-high voltage cable conductor joint according to claim 1, characterized in that: The conductor core wire (1.1) is made of aluminum, the raw material of the welding molten metal is a conductive aluminum alloy, in step S6, the preheating temperature is 600-700° C., and in step S8, the heating temperature is 1200-1300° C.

4. The method for casting an ultra-high voltage cable conductor joint according to claim 1, characterized in that: Step S7 also includes step S7.2: the welding metal liquid overflows from the quartz funnel (4).

5. The method for casting an ultra-high voltage cable conductor joint according to claim 4, characterized in that: Step S7 also includes step S7.3: using the tuning fork (7) to resonate and move back and forth around the outside of the quartz tube (3) until no bubbles are generated.

6. The method for casting an ultra-high voltage cable conductor joint according to claim 4, characterized in that: Step S8 also includes step S8.1: using a tuning fork (7) to resonate and move back and forth around the outside of the quartz tube (3) until no bubbles are generated.

7. The method for casting an ultra-high voltage cable conductor joint according to claim 1, characterized in that: After completing step S9, the method further includes step S9.1: heating the mud seal (5) until the mud seal (5) is dried and cracked, and cleaning the mud seal (5).

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