WO2007016709A2

WO2007016709A2 - A furnace electrode seal arrangement

Info

Publication number: WO2007016709A2
Application number: PCT/ZA2006/000092
Authority: WO
Inventors: Hugo Joubert
Original assignee: Pyromet Technologies (Pty) Ltd
Priority date: 2005-08-01
Filing date: 2006-07-31
Publication date: 2007-02-08
Also published as: WO2007016709A3; ZA200801121B

Abstract

A furnace electrode seal (10) which includes a base (22), a lower jaw member (24) which is attached to the base and which has an inclined lower surface (36), an upper jaw member (26) which is movably engaged with the base and which has an inclined upper surface (44), a bias (28) which acts between the lower jaw member and the upper jaw member, a rigid insert (30) which is movably engaged with and at least partially trapped between the lower jaw member and the upper jaw member and at least a first compressible packing member (68) located between the lower jaw member, the upper jaw member and the insert.

Description

A FURNACE ELECTRODE SEAL ARRANGEMENT

BACKGROUND OF THE INVENTION

[0001] This invention relates to a furnace electrode seal arrangement for use in an electrical furnace.

[0002] The term "furnace" is used in this specification with reference to any electrical- powered furnace which makes use of an electrode such as for example a DC Arc furnace or an AC furnace.

[0003] During operations the environment inside a furnace is hostile and all components which are exposed to the environment inside the furnace are exposed to extreme conditions which exposure results in limited working life and escalated maintenance costs.

[0004] Furnace electrodes are often suspended from above and are movable by structure over or on the furnace roofs or smoke hoods. Such an electrode depends downwardly from its support structure through an opening in the roof and is vertically movable by the support structure. The electrode and roof are spaced apart to allow for horizontal movement and misalignment of the electrode during use. The support structure from which the electrode is suspended is exposed to the extreme conditions in the furnace during use as a result of the opening between the electrode and the roof.

[0005] It is known to seal the space between the electrode and roof by way of an annular seal arrangement which circumscribes the electrode. A seal packing made from a soft, flexible and compressible material is in this type of arrangement forced into close contact with the electrode.

[0006] Vertical movement of the electrode, variable diameters of the electrode and the abrasive surface of the electrode cause damage to such packing. In many cases extreme temperatures and fumes to which the packing is exposed result in the early breakdown of the packing.

[0007] The replacement costs and production loss as a result of maintenance requirements on the packing are a concern.

[0008] In applications where an annular seal arrangement with a hard, inflexible packing of a fixed diameter is used, the seal does not compensate for movement of the electrode or changes in diameter of the electrode. Additionally these fixed seals do not provide a positive gas seal around the electrode.

SUMMARY OF THE INVENTION

[0009] This invention aims to provide an alternative furnace electrode seal arrangement which might alleviate some of the aforementioned problems.

[0010] The invention provides a furnace electrode seal arrangement which includes an annular base formation which is engageable with a furnace roof through which an electrode extends, at least one jaw member which is engaged with the base formation, a bias means which acts on the jaw member and a rigid, circular insert of variable diameter which is movably engaged with the jaw member. [0011] The base formation may include a plurality of segments.

[0012] The seal arrangement may include at least one water cooling passage which extends through the base formation and preferably the seal arrangement includes a plurality of water cooling passages which extend through the base formation.

[0013] Preferably the seal arrangement includes a lower jaw member which is attached to the base formation and an upper jaw member which is engaged with the base formation. The bias means may act between the upper jaw member and the lower jaw member and the insert may be at least partially trapped between the upper jaw member and the lower jaw member. The lower jaw member and the upper jaw member are preferably movable relatively to one another.

[0014] The lower jaw member may include an inclined lower surface which abuts the insert. The upper jaw member may include an inclined upper surface which abuts the insert.

[0015] The insert may include a first side which is vertical and which abuts the electrode in use and a second, opposite side which is tapered and which abuts the upper jaw member and lower jaw member. The insert may be of a two-part construction and may include a top member and an identical and opposing bottom member.

[0016] The insert may be made from any appropriate rigid, heat resistant material and is preferably made from graphite. [0017] The seal arrangement may include a first compressible packing member which is positioned between the jaw member and the insert.

[0018] The seal arrangement may include a second compressible packing member which is located between the base formation and the jaw member.

[0019] The invention also extends to a furnace electrode seal arrangement which includes a base formation, a lower jaw member which is attached to the base formation and which has an inclined lower surface, an upper jaw member which is movably engaged with the base formation and which has an inclined upper surface, a bias means which acts between the lower jaw member and the upper jaw member, a rigid insert which is movably engaged with and at least partially trapped between the lower jaw member and the upper jaw member and at least a first compressible packing member located between the lower jaw member, the upper jaw member and the insert.

[0020] The insert may include a plurality of insert blocks.

[0021] The seal arrangement may include a second compressible packing member which is located between the base formation, the lower jaw member and the upper jaw member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention is further described by way of example with reference to the accompanying drawings in which : Figure 1 is a side view of a furnace electrode seal arrangement according to the invention;

Figure 2 is a perspective view of the arrangement of Figure 1 with a number of components removed for clarity;

Figure 3 is a sectioned side view of a portion of the seal arrangement of Figure 1 ; and

Figure 4 is an exploded view of the sectioned side view of the seal arrangement shown in Figure 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] Figures 1 to 4 show a furnace electrode seal arrangement or seal 10 which is fitted over an opening 12 in a roof 14 where through an electrode 16 extends.

[0024] The seal 10, roof 14 and electrode 16 form part of a known electrical furnace 18 which is not described herein in detail. The roof 14 and electrode 16 are also of known construction.

[0025] An annular pedestal or housing 20 is fitted to the roof 14 to define the opening 12. The seal 10 is engaged with and lies on the housing 20. In this example the seal 10 is free floating on the housing 20 to allow at least limited horizontal movement of the seal 10 on the housing 20 to compensate for horizontal movement of the electrode 16. Alternatively the seal 10 can be fixed to the housing 20 or the roof 14.

[0026] The seal 10 has an annular base 22 which surrounds the electrode 16 and which abuts the housing 20, a lower jaw 24 which is attached to or engaged with the base 22, an upper jaw 26 which is movably engaged with the base 22, a bias 28 which acts between the base 22 and the lower jaw 24 and the upper jaw 26 and a rigid insert 30 which is circular in shape and has a variable diameter. The insert 30 is movably engaged with and at least partially trapped between the lower jaw 24 and the upper jaw 26.

[0027] The base 22 is made from copper or any other suitable heat conductive material. An air passage 32 is formed between the base 22 and the housing 20 and a plurality of water cooling passages 34 are formed in the base 22. The cooling passages 34 are connected to a water cooling system in a known manner. Depending on requirements one or more cooling passages 34 can be used.

[0028] The lower jaw 24 faces towards the opening 12 and the electrode 16 and has an inclined lower surface 36.

[0029] The upper jaw 26 has a skirt 38 wherethrough the bias 28 extends, a flange 40 which extends inwardly away from the skirt 38 towards the opening 12 and the electrode 16 and a plurality of brackets 42 which attach the flange 40 to the skirt 38. The upper jaw 26 has an inclined upper surface 44 on the flange 40 which faces towards the opening 12 and the electrode 16. A tapered and open mouth 46 is formed between the lower surface 36 and the upper surface 44.

[0030] The lower jaw 24 and the upper jaw 26 are made from any appropriate metal material.

[0031] The bias 28 has a plurality of bolts 48 which are fixed to and extend from the base 22. A nut 50 is threaded on to each of the bolts 48 and the skirt 38 is trapped on the bolts 48 and between the nuts 50 and the base 22. A number of spring washers 52 are trapped on each bolt 48 between the nut 50 and the skirt 38.

[0032] The insert 30 is of a multi-part construction and has a first set of lower blocks 54 which are arranged around the electrode 16 and between the lower surface 36 and the electrode 16 and a second set of upper blocks 56 which are arranged around the electrode 16 and between the upper surface 44 and the electrode 16.

[0033] As is evident from Figure 2 each of the upper blocks 56 overlay and abut two underlying lower blocks 54. In this manner the insert 30 is constructed from a plurality of lower blocks 54 and upper blocks 56 which lay on the lower blocks 54. The lower blocks 54 and the upper blocks 56 are identical and each block 54, 56 has a first, vertical side 58 and a second, opposite side 60. The first side 58 abuts the electrode 60 and the second side 60 has an inclined abutment surface 62. The abutment surface 62 of each of the lower blocks 54 abuts and rides on the lower surface 36 and the abutment surface 62 of each of the upper blocks 56 abuts and rides on the upper surface 44. The second side 60 of each block 54, 56 has a vertically extending seal surface 64 which extends from the abutment surface 62.

[0034] In combination and in cross-section each pair of overlaying lower block 54 and upper block 56 results in the insert 30 having a vertical face 66 which abuts the electrode 16 and a tapered face 67 which has an outwards reducing taper and which abuts the lower jaw 24 and upper jaw 26.

[0035] Each block 54, 56 is made from graphite or any other rigid, abrasion resistant and heat resistant material. The multi-part constructions of the insert 30 allows radial and horizontal movement of the blocks 54, 56 so that the insert 30 can, to at least a limited extent, increase and decrease in diameter against the biasing action of the bias 28.

[0036] A first, flexible and compressible ring seal 68 is used as packing between the seal surfaces 64 of the blocks 54, 56, the lower surface 36 and the upper surface 44.

[0037] A second, flexible and compressible ring seal 70 is used as packing between the base 22, lower jaw 24 and upper jaw 26.

[0038] The base 22 and lower jaw 24 are in this example integrally formed and depending on requirements can be made separately and attached to one another. The base 22 and lower jaw 24 and the upper jaw 26 are formed as segments which are attached to one another to form the annular seal 10.

[0039] In use the segments of the base 22 and lower jaw 24 are placed on the housing 20 and around the electrode 16 and attached to one another in an appropriate manner. The cooling passages 34 are connected to water supply.

[0040] The plurality of lower blocks 54 are packed between the lower jaw 24 and the electrode 16 in order for each first side 58 to abut the electrode 16 and for each abutment surface 62 to abut the lower surface 36. Thereafter the first ring seal 68 is fitted between the lower surface 36 and the seal surfaces 64 of the lower blocks 54.

[0041] Next the plurality of upper blocks 56 are packed on to the lower blocks 54 in an overlying manner and with the first side 58 of each block 56 engaged with the electrode 16 and the abutment surface 62 of each block 56 facing outwardly. The first ring seal 68 is compressed and remains between the lower surface 36 and the seal surfaces 64 of the lower blocks 54 and the upper blocks 56. The second ring seal 70 is located at an interface between the base 22 and the lower jaw 24 and adjacent the bolts 48. The segments of the upper jaw 26 are engaged with the bolts 48 and attached to one another in order for the lower and upper blocks 54, 56 to become trapped between the lower jaw 24 and the upper jaw 26, the first ring seal 68 to become trapped between the lower jaw 24, the upper jaw 26 and the lower and the upper blocks 54, 56 and the second ring seal 70 to become trapped between the base 22, the lower jaw 24 and the upper jaw 26 in the manner shown in Figure 3. The required number of spring washers 52 are fitted to each bolt 48 and a nut 50 is threaded on each bolt 48.

[0042] By tightening the nuts 50 the upper jaw 26 is forced into close contact with the base 32 and towards the lower jaw 24. The first and second ring seals 68, 70 are compressed and the upper surface 44 comes into contact with the abutment surface 62 of the upper blocks 56.

[0043] By varying the tightness of the nuts 50 the upper and the lower jaws 24, 26 are moved towards one another or apart. As a result of the tapered shape of tapered face 67 of the insert 30 relative movement between the lower and the upper jaws 24, 26 towards the electrode 16 is encouraged. By adjusting the force at which the upper and the lower jaws 24, 26 are forced towards one another the force with which the insert 30 abuts against the electrode 16 is controlled.

[0044] During use of the furnace 18 the escape of heat and fumes from the furnace 18 through the opening 12 is obstructed by the base 22, the lower jaw 24 and the insert 30. The base 22 and lower jaw 24 are made from a heat conductive material and are cooled by cooling fluid which passes through the cooling passages 34. The insert 30 is made from a heat-resistant material and limits the exposure of the upper jaw 26 to heat generated in the furnace 18. The first and second ring seals 68, 70 act as fluid seals to limit the escape of fumes from the furnace 18. These ring seals 68, 70 are however remote from the opening 12 and are protected from heat generated in the furnace 18 by the base 22, lower jaw 24 and insert 30.

[0045] As the electrode 16 moves vertically it rides on the vertical face 66. Limited horizontal movement of the electrode 16 is allowed as the insert 30 is in such a case forced towards the lower and the upper jaws 24, 26 and the lower and the upper jaws 26 are forced apart against the biasing action of the bias 28. Movement of the electrode 16 away from the insert 30 results in at least the partial closure of the upper and the lower jaws 24, 26 as a result of the biasing action of the bias 28. The partial closure of the upper and the lower jaws 24, 26 forces the insert 30 towards the electrode 16. Changes in the diameter of the electrode 16 as a result of wear or manufacturing is compensated for by the varying of the diameter of the insert 30 against the biasing action of the bias 28. In this manner the integrity of the seal 10 is maintained in a dynamic way.

[0046] As the electrode 16 passes through the opening 12 the electrode 16 rides on the vertical face 66 of the insert 30 which results in abrasion of the blocks 54, 56. As the blocks 54, 56 wears down the upper and the lower jaws 24, 26 close against the biasing action of the bias 28 and the insert 30 is forced towards the electrode 16. For this reason it is necessary to allow limited spaces between adjacent blocks 54, 56 in the first set of lower blocks 54 and the second set of upper blocks 56.

[0047] In the seal 10 the insert 30 forms a rigid packing between the electrode 16 and the lower and the upper jaws 24, 26 which is abrasion and heat resistant. The soft seals created by the first and second ring seals 68, 70 are remote from the opening 12 and are protected. The seal 10 thus provides a physical barrier against heat generated in the furnace 18 and the electrode 16 as well as a gas seal against fumes generated in the furnace 18.

[0048] Alternatively to using blocks 54, 56 of which the interface between the respective upper blocks 54 and lower blocks 56 is flat, the opposing surfaces can have complimentary keying formations on the respective and opposing blocks 54, 56. These keying formations allow the upper and the lower blocks 54, 56 to inter-engage but allows relative movement in a radial direction. The keying formations can have any appropriate shape. Each opposing surface can for example have a shallow V-shape in cross-section (as is shown in dotted outlines in Figure 2), to ensure that the blocks 54, 56 can move radially relatively to one another and that horizontal, sideways movement between the upper blocks 54 and the lower blocks 56 is restricted.

Claims

1. A furnace electrode seal arrangement which includes an annular base formation which is engageable with a furnace roof through which an electrode extends, at least one jaw member which is engaged with the base formation, a bias means which acts on the jaw member and a rigid, circular insert of variable diameter which is movably engaged with the jaw member.

2. A furnace electrode seal arrangement according to claim 1 wherein the base formation includes a plurality of segments.

3. A furnace electrode seal arrangement according to claim 1 or 2 which includes at least one water cooling passage which extends through the base formation.

4. A furnace electrode seal arrangement according to claim 3 which includes a plurality of water cooling passages which extend through the base formation.

5. A furnace electrode seal arrangement according to any one of claims 1 to 4 which includes a lower jaw member which is attached to the base formation and an upper jaw member which is engaged with the base formation.

6. A furnace electrode seal arrangement according to claim 6 wherein the bias means acts between the upper jaw member and the lower jaw member.

7. A furnace electrode seal arrangement according to claim 5 or 6 wherein the insert is at least partially trapped between the upper jaw member and the lower jaw member.

8. A furnace electrode seal arrangement according to claim 5, 6 or 7 wherein the lower jaw member and the upper jaw member are movable relatively to one another.

9. A furnace electrode seal arrangement according to any one of claims 5 to 9 wherein the lower jaw member includes an inclined lower surface which abuts the insert.

10. A furnace electrode seal arrangement according to any one of claims 5 to 9 wherein the upper jaw member includes an inclined upper surface which abuts the insert.

11. A furnace electrode seal arrangement according to any one of claims 1 to 10 wherein the insert includes a first side which is vertical and which abuts the electrode in use and a second, opposite side which is tapered.

12. A furnace electrode seal arrangement according to any one of claims 1 to 11 wherein the insert includes a top member and an identical and opposing bottom member.

13. A furnace electrode seal arrangement according to any one of claims 1 to 12 which includes a first compressible packing member which is positioned between the jaw member and the insert.

14. A furnace electrode seal arrangement according to any one of claims 1 to 13 which includes a second compressible packing member which is located between the base formation and the jaw member.

15. A furnace electrode seal arrangement which includes a base formation, a lower jaw member which is attached to the base formation and which has an inclined lower surface, an upper jaw member which is movably engaged with the base formation and which has an inclined upper surface, a bias means which acts between the lower jaw member and the upper jaw member, a rigid insert which is movabiy engaged with and at least partially trapped between the lower jaw member and the upper jaw member and at least a first compressible packing member located between the lower jaw member, the upper jaw member and the insert.

16. A furnace electrode seal arrangement according to claim 14 wherein the insert includes a plurality of insert blocks.

17. A furnace electrode seal arrangement according to claim 14 or 18 which includes a second compressible packing member which is located between the base formation, the lower jaw member and the upper jaw member.