WO2011063426A1

WO2011063426A1 - An arc furnace electrode clamp assembly

Info

Publication number: WO2011063426A1
Application number: PCT/ZA2009/000100
Authority: WO
Inventors: Malcolm Christian Theron; Riander Faurie Botha
Original assignee: Allied Furnace Consultants (Pty) Limited
Priority date: 2009-11-17
Filing date: 2009-11-17
Publication date: 2011-05-26
Also published as: ZA201203520B

Abstract

The invention provides an arc furnace electrode clamp assembly 10. The assembly includes two semi circular clamp segments 12 hingedly connectable along opposed edges to define closable tubular jaws 14 of a clamp. The assembly further includes an opening and closing arrangement 18 for opening and closing the jaws 14, which arrangement includes a pair of opposed connection points 20 arranged outside and along the length of the tubular jaws 14 for connecting to a pair of pivotably connected members 22, which pivotably connected members 22 are configured to be pivoted to each other by means of a wedge 24.

Description

09 000100

Title: An Arc Furnace Electrode Clamp Assembly

Technical field of the invention

This invention relates to an assembly for an arc furnace electrode clamp.

Background to the invention

Arc furnaces are used in the melting and smelting industry. The energy of an electrical arc between a vertically orientated electrode and the ore, reductant and flux and/ or metal smelts and/ or melts the ore, reductant and flux and/ or metal inside the furnace to form molten slag and molten metal. In use, certain parameters are continuously monitored. Accordingly, the height of the electrode above the slag and molten metal is continually adjusted to provide an optimum arc and power input. During use, the

electrode is consumed and is intermittently lowered towards the slag and molten metal.

It is well known in the art that normally, the height adjustment and lowering of the electrode is achieved with an electrode column. The electrode column includes an upper electrode clamp and a lower electrode clamp. Normally, the upper clamp is fixed in position and is connected to the lower clamp with a hydraulic push-pull arrangement, to move the lower clamp relative to the fixed upper clamp. During operation of the furnace the bottom clamp is in the closed position clamping the electrode and the upper clamp is in the open position. The height of the electrode above the slag and molten metal is controlled by means of the hydraulic push-pull arrangement in

response to continually monitored process parameters such as the current flowing through the electrode.

When the electrode is consumed close to the point to the point where the optimum position of the electrode cannot be reached the electrode 0100 is lowered by means of a slipping cycle. A slipping cycle means lowering relative to the lower clamp. A slipping cycle includes the steps of first closing the upper clamp to clamp the electrode in a fixed position and then by

opening the lower clamp. The lower clamp is then slid upwards over the electrode toward the upper clamp by retracting the hydraulic push-pull

arrangement. Once in the retracted position, the bottom clamp is closed to clamp the electrode and the upper clamp is opened and normal operation can continue. It will be appreciated that there is a need for short slipping cycles since the electrode is in a fixed position during a slipping cycle and its height cannot be optimally adjusted as in normal operation. It will further be

appreciated that the electrode must not be allowed to slip into the furnace through the bottom clamp during operation of the furnace. It will also be appreciated that it is a costly to shut the furnace down and that it will be an advantage not to shut the furnace down when a part of the upper or lower clamp needs to be replaced. It will further be appreciated that the bulk of the slipping device should be limited. It will also be appreciated that the slipping device should preferably be able to be scaled up for large electrode diameters of more than .55 meters for large furnace plants.

The inventor is aware of electro mechanically controlled clamps. These clamps are complex and need after installation lubrication and

maintenance due to high wear and require high operator involvement due to its complexity. These clamps require a relatively long time to complete a slipping cycle.

The inventor is further aware of a spring and hydraulically controlled clamp. This clamp includes a single unit comprising a single spring and single hydraulic cylinder in axial alignment. The inventor is also aware of a slipping device with an electrode clamp, which clamp includes two semi circular clamp segments hingedly connectable along opposed edges to define closable tubular jaws of a clamp. This arrangement is well known in the art. This clamp further includes a lever arrangement for opening and closing the jaws, which lever arrangement includes opposed connection points arranged along the length of the tubular jaws for connecting to non aligned opening means and closing means. This solves the problem of maintenance without shut down of the furnace since the opening means and closing means is separated and separately maintainable. However, it will be appreciated by those skilled in the art that this clamping arrangement, due to lack of travel has impractical space requirements limiting its application to electrodes having a diameter of less than 1 .5 meters. It is an object of this invention to provide a clamping arrangement for an assembly for an arc furnace electrode clamp with all the above advantages, which allows for use for electrode diameters up to 1.55m and higher. General description of the invention

According to the invention, there is provided an assembly for an arc furnace electrode clamp, which assembly includes:

two semi circular clamp segments hingedly connectable along opposed edges to define closable tubular jaws of a clamp; and

an opening and closing arrangement for opening and closing the jaws, which arrangement includes a pair of opposed connection points arranged outside and along the length of the tubular jaws for connecting to a pair of pivotably connected members, which pivotably connected members are configured to be pivoted relative to each other by means of a wedge.

The term, length, of the clamp segments will be understood to be parallel to the axis of the tubular jaws. The assembly may include a third semi circular clamp segment to be fitted between the free ends of the two semi circular clamp segments and the segment may also include a pair of opposed connection points arranged outside along the length of the segment for connecting, respectively, to the pair of pivotably connected members.

The connection points will be understood to be a point in plan view and may be series of connection points in a line along the length of the segment, in side view.

One series of connection points of one jaw member may correspond to one of the series of connection points on the third clamp segment while the series of connection points of the other jaw member may correspond to the other series of connection points on the third clamp segment, closest to each other, in each case. The connection points of the jaw members and the third clamp segments are connected to the ends of the pivotably connected members by means of connection rods or linking members. The lengths, configuration and connection points of the connection rods are selected such that, when the free ends of the pair of pivotably connected members are wedged apart from each other, the three clamp segments move in concert towards the axis of the tubular jaws, to apply a uniform clamping force, in use.

The clamp assembly in accordance with the invention can be used in open and submerged furnaces. It can also be used in AC and DC furnaces, preferably AC furnaces. The clamps may also be used for any ferro alloy or chromium furnace. The clamp may further be used for pre-baked electrodes such as graphite electrodes or preferably for Soderberg electrodes. The invention also extends to an electrode column and furnace fitted with an electrode clamp in accordance with the invention.

The applicant believes that the clamp assembly in accordance with the invention is compact and allows it to be used in slipping devices for electrodes in excess of 1.55 meters. The invention can also be.

advantageously used for both upper and lower clamping assemblies of a slipping device. The wedge like opening and closing means minimises moving parts and increases reliability, and is maintainable with minimum down time and costs.

Detailed description of the invention

The invention is now described by way of example with reference to the accompanying drawings.

In the drawings:

Figure 1 shows diagrammatically a plan view of a clamp assembly for an electrode column, in accordance with the invention;

Figure 2 shows diagrammatically an end view of the opening and closing arrangement for opening and closing the jaws, in a clamping state; and Figure 3 shows diagrammatically an end view of the opening and closing arrangement for opening and closing the jaws, in a release state.

Referring now to the drawings, the clamp assembly for an electrode clamp, in accordance with the invention, is generally indicated by reference numeral 10. An arc furnace electrode clamp assembly 10 includes two semi circular clamp segments 12 hingedly connectable along opposed edges 13 to define closable tubular jaws 14 of a clamp. The assembly 10 also includes a third semi circular clamp segment 16 to be fitted between the free ends of the two semi circular clamp segments 12.

The assembly 0 further includes an opening and closing arrangement 18 for opening and closing the jaws of the segments 12, which arrangement includes a pair of opposed connection points 20 arranged outside and along the length of the tubular jaws for connecting to a pair of pivotably connected members 22, which pivotably connected members are configured to be pivoted relative to each other by means of a wedge 24 shown in figures 2 and 3. The third semi circular clamp segment 16 also includes a pair of opposed connection points 26 arranged outside along the length of the segment 16 for connecting, respectively, to the pair of pivotably connected members 22. One series of connection points of one jaw member, 20.1 or 20.2, corresponds to one of the series of connection points, 26.1 or 26.2, respectively, on the third clamp segment 16. The connection points 20 of the jaw members 12 and the third clamp segments are connected to the ends of the pivotably connected members 22 by means of a pair of sets of connection rods or linking members 28.1 and 28.2. The lengths, configuration and connection points of the connection rods 28 are selected such that, when the free ends 22.2 of the pair of pivotably connected members 22 are wedged apart from each other, the three clamp segments 12 and 16 move in concert towards the axis 30 of the tubular jaws, to apply a uniform clamping force, in use.

With reference to figures 2 and 3 a set of coils springs urges the wedge shaped free ends 24 of the pair of pivotably connected members 22 into a closed , clamping state and a pair of hydraulically operable wedge shaped opening wedge members 34 can operably force the free ends 24 into an open, non clamping states. Figure 2 shows the forces by means of the arrows of the clamping state and Figure 3 shows the forces by means of the arrows of the non clamping state. It shall be understood that the examples are provided for illustrating the invention further and to assist a person skilled in the art with understanding the invention and are not meant to be construed as unduly limiting the reasonable scope of the invention.

Claims

1. An arc furnace electrode clamp assembly, which assembly includes:

2. An assembly as claimed in Claim 1 , which includes a third semi circular clamp segment to be fitted between the free ends of the two semi circular clamp segments and wherein the segment also include a pair of opposed connection points arranged outside along the length of the segment for connecting, respectively, to the pair of pivotably connected members.

3. An assembly as claimed in Claim 2, wherein each connection point is in the form of a series of connection points in a line along the length of the segment and one series of connection points of one jaw member corresponds to one of the series of connection points on the third clamp segment while the series of connection points of the other jaw member corresponds to the other series of connection points on the third clamp segment, closest to each other, in each case.

4. An assembly as claimed in Claim 3, wherein the connection points of the jaw members and the third clamp segments are connected to the ends of the pivotably connected members by means of connection rods or linking members.

5. An assembly as claimed in Claim 4, wherein the lengths, configuration and connection points of the connection rods are selected such that, when the free ends of the pair of pivotably connected members are wedged apart from each other, the three clamp segments move in concert towards the axis of the tubular jaws, to apply a uniform clamping force, in use.

6. An electrode column fitted with an electrode clamp as claimed in any one of the claims 1 to 5.

7. An arc furnace electrode clamp assembly substantially as described herein with reference to the accompanying drawings.

8. An electrode column substantially as described herein with reference to the accompanying drawings.