INTRODUCTION AND BACKGROUND

This invention relates to self-baking electrodes and more particularly to a casing segment, casing assembly and method of joining two casing segments for such an electrode.

Self-baking electrodes or Soderberg electrodes are well known in the art of electric furnaces. In use, these electrodes extend through a respective hole in a roof of a vessel of the furnace into the vessel. Each electrode comprises a solid carbon electrode core which is sheathed by an elongate tubular casing assembly with internal fins. The casing assembly is formed by welding two or more elongate casing segments together. As the electrode is consumed inside the vessel, a paste is fed from the top of the casing assembly into the casing assembly. The paste melts and then is baked into the solid carbon electrode core as it is lowered into the vessel. A part of the casing assembly inside the vessel is consumed with the electrode core and therefore, the casing assembly has to be regenerated from the top of the electrode by adding another segment in end to end relationship to a presently top-most segment.

In adding another segment to the top-most segment, temporary openings are provided in a sidewall between the upper and lower segments. The segments and their respective fins are welded to one another by an operator or a temporarily mounted robotic welder extending from the outside of the segment substantially radially through the openings to the inside of the segment. After the welding process, the openings are closed with steel closures and/or steel straps which are welded to the outside of the sidewalls. The closures, straps and welded regions need to be grinded on the outside of the assembly to ensure a smooth surface, so that the electrode may be lowered through the hole in the roof into the vessel as described above.

The above process is time and labour intensive, especially when taking into account that a furnace comprises three to six electrodes and that the process must be repeated for each electrode and, if a robotic welder is used, the welder needs to be relocated on the furnace from one electrode to a next, before the work on the next could commence.

OBJECT OF THE INVENTION

Accordingly, it is an object of the present invention to provide an alternative casing segment, casing assembly and a method of joining two casing segments with which the applicant believes the aforementioned disadvantages may at least be alleviated or which may provide a useful alternative for the known casing segments, casing assemblies and a method of joining two casing segments. SUMMARY OF THE INVENTION

According to the invention there is provided an electrode casing segment comprising:

- an elongate tubular sidewall having a first end and a second end;

- a plurality of elongate fins extending from the sidewall inwardly and between the first end and the second end, each fin having a first end towards the first end of the sidewall and a second end towards the second end of the sidewall; and

- at least one of the fins of the casing segment comprising a first formation at the first end of the fin and a second complementary formation at the second end of the fin, the second complementary formation, in use, cooperating with the first formation of a fin of another casing segment which is connected to the casing segment in end to end relationship to align the at least one fin of the casing segment with the fin of the other casing segment.

The first formation may comprise a region towards the first end of the fin and the second formation may define a recess configured for receiving the first formation of the fin of the other casing segment. The sidewall may have any suitable shape in transverse cross section, but preferably is circular in transverse cross section.

Each fin may be generally rectangular in shape having opposed first and second sides extending between the first and second ends of the fin, the first side being secured to the sidewall.

At least some of the fins may define at least one of a first notch in a first corner region between the first side of the fin and the first end of the fin and a second notch in a second corner region between the first side of the fin and the second end of the fin.

The segment may comprise an inner ring which is secured to an inside of the tubular sidewall at one of a) the second end of the tubular sidewall to extend beyond the second end of the tubular sidewall in a direction away from the first end of the tubular sidewall and b) the first end of the tubular sidewall to extend beyond the first end of the tubular sidewall in a direction away from the second end of the tubular sidewall.

Further according to the invention there is provided a casing assembly comprising at least a first casing segment and a second similar casing segment and wherein the ring of the first segment fits in spigot socket fashion into the first end of the second casing segment and with a first end of at least one fin of the second casing segment located in the recess of the second formation of a fin of the first casing segment.

In a presently preferred embodiment of the assembly, the first end of each fin of the second casing segment is located in a respective recess of the second formation of an aligned fin of the first casing segment.

The inner ring of the first casing segment may be welded to an inside of the tubular sidewall of the second casing segment and the first ends of the fins of the second casing segment may be welded to the second formation of the aligned fin of the first casing segment.

Still further according to the invention there is provided a method of joining first and second elongate tubular electrode casing segments in end to end relationship to one another, the method comprising the steps of:

- causing an arm of a robotic welder to extend axially into a casing assembly comprising the first and second casing segments in end to end relationship; and

- welding parts of the first and second casing segments together from the inside of the casing assembly.

The first and second electrode casing segments may be identical in configuration and each of the first and second casing segments may comprise: an elongate circular cylindrical sidewall having a first end and a second end; a plurality of elongate fins extending from the sidewall radially inwardly and between the first end and the second end; each fin having a first end towards the first end of the sidewall and a second end towards the second end of the sidewall; at least some of the fins comprising a first formation at the first end of the fin and a second complementary formation at the second end of the fin; at least some of the fins may define at least one of a first notch in a first corner region between the first side and the first end of the fin and a second notch in a second corner region between the first side and the second end of the fin; an inner ring secured to the second end of the tubular sidewall and extending beyond the second end of the tubular sidewall in a direction away from the first end of the tubular sidewall, the ring of the first casing segment may be received in spigot socket fashion into the first end of the second casing segment to form the casing assembly and the second complementary formations of the fins of the first casing segment cooperating with the first formations of the fins of the second casing segment, the method comprising: welding from the inside of the assembly the first formations of the fins of the second casing segment to the second formations of the fins of the first casing segment; and utilizing the notches to access and weld the inner ring of the first casing segment to an inside of the sidewall of the second casing segment. The invention still further extends to a furnace comprising at least two spaced electrode casing assemblies extending through a roof of the furnace and each comprising respective casing segments; and a robotic welder mounted permanently on the furnace intermediate the assemblies to weld segments of the casing assemblies to one another in end to end relationship.

BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS

The invention will now further be described, by way of example only, with reference to the accompanying diagrams wherein: figure 1 is a diagrammatic isometric view, partially broken away for better clarity, of an example embodiment of a self-baking electrode casing segment; figure 2 is a diagrammatic isometric view of an electric furnace having three self-baking electrodes each comprising an electrode casing assembly (one shown exploded) comprising respective casing segments extending through a roof of the furnace into a vessel of the furnace and a permanently mounted robotic welder; figure 3 is a view similar to figure 2, with the exploded segments of the one electrode casing assembly closer in position; figure 4 is a diagrammatic view of the one assembly in exploded form with one casing segment of the assembly in section; figure 5 is a view similar to figure 4 with both segments in section; figure 6 is an enlarged view of the encircled part in figure 5; figure 7 is an enlarged view of the encircled part in figure 5 when the two segments are in position in end to end relationship relative to one another; and figure 8 is a view similar to figure 2, but with the casing segments of the one electrode casing assembly in section and in position in end to end relationship with one another.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

An example embodiment of a casing segment of a casing assembly for a self-baking electrode of an electric furnace is generally designated by the reference numeral 10.1 in figures 1 to 7.

The casing segment 10.1 comprises elongate circular cylindrical sidewall 12 and a plurality of elongate fins 14.1 to 14.n extending radially inwardly from the sidewall 12. On manufacture of the segment 10.1 , the fins are welded to the inside of the sidewall 12 in known manner. The sidewall 12 has a first end 16 and a second end 18. An inner ring 20 is welded to the inside of the sidewall at the second end 18 to extend coaxially beyond the second end in a direction away from the first end 16. Each fin 14.1 to 14.n is rectangular in shape and has a first end 22 (best shown in figures 1 and 5) and a second end 24. Each fin, in a corner region thereof between a side thereof abutting the sidewall 12 and respectively the first end of the fin and the second end of the fin, defines a respective notch 26 and 28. Furthermore, each fin has a first formation 29 and a second complementary formation 30 at the first and second ends respectively.

The second complementary formation 30 (best shown in figures 6 and 7) of the first casing segment is configured to receive the first formation 29 of a fin of a second casing segment 10.2.

In the example embodiment shown, the second formation 30 comprises a member which is welded onto each fin upon manufacture of the casing segment 10.1. The member defines a V-shaped recess 32 configured to receive the first formation 29, in the form of a region towards the first end of the fin of another casing segment.

As will be explained in more detail below, in use, and at a furnace 100 (shown in figures 2, 3 and 8), the first segment 10.1 and the second segment 10.2 are welded together to form a casing assembly 34. Referring to figures 2, 3 and 8, the furnace 100 comprises a vessel 102 having a roof 104. Three self-baking electrodes 106, 108 and 110 extend vertically from the outside of the furnace through a respective hole in the roof into the vessel. Each electrode comprises an electrode casing assembly 34 comprising at least two segments 10.1 and 10.2 and a solid carbon electrode core (not shown). The core is formed in known manner by filling, from the top, the casing assembly with a paste (also not shown). The paste melts and, in the part of the casing assembly extending into the vessel, is baked to form the solid carbon electrode core. As explained in the introduction of this specification, in use, the electrode core together with the casing assembly 34 are consumed from their ends terminating in the vessel. To regenerate the casing assembly 34, another segment 10.2 needs to be added in end to end relationship at the top end of currently top segment 10.1 (see electrode 110 in figures 2, 3 and 8) of the assembly on the furnace.

As best shown in figures 2, 3 and 8, the furnace 100 further comprises a robotic welder 112. The welder 112 may have any suitable configuration, but in this example embodiment may comprise a vertically extending main shaft 114 which is telescopically manipulatable and which is permanently mounted on the furnace, in this case on the roof 104, in a region intermediate the electrodes 106, 108 and 110. The welder further comprises a telescopically manipulatable transverse arm 116 which is rotatable about the main shaft. A telescopically manipulatable pivotal arm 118 is provided at a free end of the transverse arm. A further telescopically manipulatable pivotal arm 120 is provided at a free end of the pivotal arm 120. A welding tool 122 is provided at a free end of the further pivotal arm.

The addition of the other segment 10.2 to the currently top segment 10.1 is best explained with reference to figures 2 to 8. As stated before, the segments 10.1 and 10.2 are identical in shape and configuration. As best shown in figure 4, segment 10.2 is brought into axial alignment with segment 10.1. Furthermore, as shown in figures 5 and 6, the fins of the segment 10.2 are brought into axial alignment with the fins of the first segment 10.1 .

As shown in figure 7, the ring 20 at the second end 18 of the first segment

10.1 is received in spigot socket fashion in the first end 16 of the second segment. Furthermore, the first formation 29 of each fin of the segment

10.2 is received by the second complementary formation 30 of each aligned fin of the first segment 10.1 , to form the assembly 34.

Referring to figure 8, the permanently mounted robotic welder 112 is used to weld parts of the segment 10.2. to parts of the segment 10.1. In this regard, access to the inside of the assembly 34 is obtained from an open top of the second segment 10.2 with the arm 118 extending axially downwards. The arms 118 and 120 are manipulated to bring the welding tool from the inside of the assembly into contact with parts of the assembly to be welded to one another. For example, the tool 122 is brought into contact with an interface between ring 20 of the first segment and an inside of sidewall 12 of the second segment 10.2. Adjacent notches 26 and 28 defined in aligned fins enable access to the full circumference of the ring, so that it may be welded to the sidewall on the inside of the assembly. The first formations 29 of the second segment 10.2 are also welded to the second formations 30 at the second ends of the aligned fins of the first segment 10.1.

It will be appreciated that with suitable manipulation of the telescopically manipulatable arms of the welder 112, the stationary welder may be used to weld new or replacement segments to any one of the casing assemblies of electrodes 106, 108 and 110. Furthermore, since access to the regions requiring welding is obtained from the open top end of the tubular sidewall 12 of the second segment, it is not required to make holes in the sidewalls of the segments 10.1 and 10.2 of the assembly 34 to obtain access to regions requiring welding.