AU637939B2 - Device for injecting preheated air into a shaft furnace and process for manufacturing ball-and-socket joints - Google Patents

Abstract

The device for injecting preheated air into a shaft furnace consists of a number of tubular members provided with a refractory lining, which are connected together by a spherical joint (94; 96) and a compensator. The spherical joints are made up of a convex ball formed in one segment and of a concave socket formed in the refractory of the adjacent segment. They comprise a protective sheath made of refractory steel extending around the convex part as far as the base of the ball. The radius of curvature of each spherical joint is of the order of magnitude of one half of the diameter of the tubular members. <IMAGE>

Description

P/00/01 1 (A3 3 9ReguLation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPEC IFICATION FOR A STANDARD PATENT

ORIGINAL

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Th folwn5*tmn safl dsrpino hsivninicuigtebs ehdo pefrmn it knw om: P-PWU-235 la DEVICE FOR INJECTING PREHEATED AIR INTO A SHAFT FURNACE AND PROCESS FOR MANUFACTURING BALL-AND-SOCKET JOINTS The present invention relates to a device for injecting preheated air into a shaft furnace, consisting of a plurality of separate cylindrical elements, each consisting of an external steel easing and an internal refractory lining and comprising at least one central tubular element connected, on one side, by a first ball-and-socket articulation and a first expansion joint to an upper connection piece integral with a preheated air feeding bustle pipe surrounding the furnace and, on the other or opposite side, by a second ball-and-socket articulation and a second expansion joint to a lower connection piece p extended by an elbow and a blast nozzle, the latter being articulated on a tuyere installed in the wall of the furnace, and in which device the ball-and-socket joints comprise a convex ball-part formed by the end of one of the connection segments and pivoting in a concave socket-part formed by the end of the adjacent connection segment and a soft refractory joint interposed therebetween.

These devices, more generally known under the name of "tuyere-stock", are subject to problems of mobility and sealing. In fact, as a result of high temperature of the preheated air (a temperature of the order of 1200 0 C or 25 more) and of the high temperature prevailing inside the furnace, the wall of the latter and the bustle pipe and the tuyere-stock are subject to thermal expansions and deformations which cause significant relative displacements between the bustle p-pe and the wall of the furnace. The tuyere-stock must therefore be capable of compensating for these relative displacements, whilst at the same time preventing leaks of gas or preheated air.

To meet these requirements, US Patent r'66,868 provides a tuyere-stock of the type described in the introduction. This tuyere-stock has since been improved by the design of universal ball-and-socket joints like those described in the German patent specification DE-C2-2218331.

The three joints of this tuyere-stock make it possible to compensate all the relative movements between the bustle pipe and the wall of the furnace. Sealing in the region of the joints is obtained by means of bellows expansion joints, whilst mechanical stability is ensured by means of cardan connections associated with the two opposite ends of the central tubular element in the region of the two universal joints.

The most stressed and most critical part is always located in the place of the joints. In fact, the mobility of the ball-part with respect to its socket often leads to irreversible distortions of the soft joints and to frictions among refractory materials. In addition, given ee 15 the difficulties to machine refractory steel, it is not possible to extend the armouring, forming the casing of the ball-part, to the tip of the latter. That is the main reason why microcracks are often formed in the refractory of the tip of the ball-part, causing disturbing circulations and whirls.

To these quality criteria of a reliable tuyere-stock are added the concern for a competitive manufacturing price, for the possibility of easy and rapid dismounting, for the possibility to easily renew the refractory material 25 if necessary, etc. It is obvious that all those criteria often tend to oppose each other, thus forcing the designer and manufacturer to ioose a reasonable compromise.

The object of the present invention is to provide a new device of the type described in the introduction, which is more resistant to wear at the place of the joints, which owing to its numerous alternative solutions, adapts itself perfectly to the requirements of the user, while permitting a reasonable manufacturing price.

In order to achieve this object, the device according to the present invention is characterized essentially in that the radius of curvature of each ball-and-socket joint ctpp oeiae 4 oL44.e is in an ordor of magnitude of half the 4 diameter of the different connection elements and in that the convex ballparts of the ball-and-socket joints comprise a protective sheath or sleeve made of refractory steel and which extends to the diametrical base of the ball-part. The reduction of the radius of curvature of the ball-and-socket joints allows a better guiding of the ball-parts in their sockets, while reducing the risks of shock and wear of the soft joints by permmitting to keep always the same width for a joint.

The reduction of the radius of curvature of the joints and the fact that the metallic armouring or casing, which at this place, forms the sheath of the ball and extends to the base of the latter, allows to maintain a uniform width of the joint slot or groove during the pivotments.

The present inventic;i also provides a new process for Smanufacturing a convex ball-part of ball-and-socket joints of a device for injecting preheated air into a shaft furnace, said process consisting in first fabricating the ball sheath or sleeve of refractory steel and to provide it with an inner refractory lining, and being characterized in that the end of a refractory steel pipe is distorted until it has the form of a convex dome with a central opening and a convex spherical surface extending between 25 the central opening and the cylindrical surface of the pipe, in that the sheath thus formed is placed on a support, in that a cylinder having a diameter slightly inferior to the diameter of said central opening, is placed axially inside, and in that refractory material is cast between the cylinder and said sheath by using the latter as a mould.

According to a first embodiment of a tuyere-stock according to the invention, the ball-parts are formed by the lower ends of the upper connection element and of the central tubular element.

The ball-part of the central tubular element can either be an integral part of this element, or be separated from the latter by a transverse junction filled with an annular joint.

The armouring of the central tubular element and the one of the lower connection pipe can be connected directly to each other through an expansion joint, or by means of a flange or an detachable weld.

The socket of the lower joint can be formed into the refractory lining cast in a cylindrical sheath made of refractory steel and arranged coaxially inside the armouring of the lower connection piece.

600 The soft refractory joint can be fixed partially to the armouring and partially to the rim of the socket. It can also be partially fixed to an inner seat of the cylindrical sheath and partially to the refractory material.

Alternatively, it can also be attached partially to the .0 refractory material and partially to a seat delimited by the upper part of the sheath and by a ring welded inside the armouring.

According to a second embodiment, the sockets of both ball-and-socket joints are arranged at the two opposite O* ends of the central tubular element, whilst the convex ball-parts are arranged in the upper and lower connection 25 pieces.

Other particular features and adavantages of the invention will be appreciated and understood by those skilled in the art from the following detailed description :of several embodiments, with reference to the accompanying drawings in which: Figure 1 shows a view, in vertical section, of a conventional tuyere-stock according to US Patent 3,766,867; Figure la shows an alternative embodiment of the lower joint of the tuyere-stock according to Figure 1; Figure 2 shows the details of a joint of a tuyerestock as disclosed in German Patent DE-C2-2218331; Figures 3 and 3a illustrate in juxtaposition and in axial section a ball-and-socket joint according to the present invention; Figure 4 illustrates schematically the process making a sheath of refractory steel, for a ball-part of a joint connection according to the present invention; Figure 5 shows diagrammatically an axial section through the vertical section of a first embodiment of a tuyere-stock according to the present invention; Figure 5a illustrates schematically an alternate execution of the lower joint of the tuyere-stock according to Figure Figures 6a, 6b and 6c illustrate schematically the different manufacturing steps of the refractory lining of 15 the different elements of the tuyere-stock depicted in Figure A 4 S- Figure 7 is a similar view to that of Figure 5 of a second embodiment of a tuyere-stock according to the

S.

present invention; Figures 8, 9 and 9a illustrate different alternate embodiments of the lower joint connection of the tuyere- *e stock according to Figure 7; Figures 10a, 10b and 10c illustrate schematically the different manufacturing steps of the refractory lining of 25 the different elements of the tuyere-stock depicted in Figure 7; -Figure 11 illustrates schematically a third embodiment of a tuyere-stock according to the present invention; Figures 12a, 12b et 12c illustrate schematically the different manufacturing steps of the refractory lining of the tuyere-stock depicted in Figure 11; Figure 13 illustrates schematically a fourth embodiment of a tuyere-stock according to the present invention and Figures 13a, 13b and 13c illustrate schematically the different manufacturing steps of the refractory lining of the tuyere-stock depicted in Figure 13.

The known tuyere-stock, designated by the reference in Figure 1, connects a main bustle pipe 22, arranged around a blast furnace, to the wall 24 of the blast furnace. This tuyere-stock 20 comprises a straight oblique section consisting of a central tubular element 26 articulated with its upper end on a connection piece 28 fixed to the bustle pipe 22 and at its lower end on a connection piece 30 flanged to an elbow 32. This elbow 32 is extended by a nozzle 34, the end of which is articulated O on a tuyere 36 fastened in the wall 24 of the furnace. The upper joints 38 and lower joints 40 between the central 15 tubular element 26 and the two connection pieces 28 and are universal joints allowing relative shifts or movements between the bustle pipe 22 and the wall of the furnace 24.

a, Sealing in the region of the joints 38 and 40 is obtained by means of bellows expansion joints 44, 46 fixed respectively to the tubular element 26 and the adjacent coinection pieces 28 and 30. Mechanical stability is ensured by means of cardan joints 48, 50 likewise connecting the central element 26 to the adjacent connection pieces 28 and 30. All these elements of the 25 tuyere-stock consist of an outer-metal armouring or housing 52 provided with an inner refractory lining 54, through which passes a supply channel or conduit 56 ensuring the passage of the preheated air.

Each one of the two joints 38, 40 consists of a convex part called ball and of a concave part called socket. In the upper joint 38, the ball is part of the upper connection piece 28 and penetrates into the socket formed by the upper end of the central element 26. The lower part of the latter constitutes the ball-part of joint 40 and penetrates into the socket formed by the upper part of the lower connection piece In the embodiment of Figure 1, the ball-part of the joint 40 is integral with the central element 26, that is, its refractory lining extends, without interruption, from the upper end to the tip of the ball-part. This design of the central element 26 makes its manufacture easier, compared with the alternative solution illustrated in Figure la, where the ball-part is separated from the rest of the central element and is connected to the latter in the region of the flange, which is provided for the fastening of the cardan 50a. The alternative solution illustrated on figure la presents however the advantage of allowing the separate dismounting of the lower part, which consists of the tubular connection piece 30 and the joint 40a, from the upper part consisting of the rest of the central element 26 and the upper joint 38 with the tubular connection piece 28. It shall be noted that the S, upper joint 38 must necessarily be designed as shown in Figure la, so that the tuyere-stock can be disconnected from the bustle pipe 22.

20 Figure 2 shows a known embodiment of a joint coi. ,ction as disclosed in the German patent DE-C2-2218331. This to embodiment is different essentially from that one depicted in Figure 1 in that the joints are spherical, as shown by the joint between the ball part 58 and the socket of the 25 connection piece 30. In this embodiment, the ball-part 58 is also separated from the central element 26, following the example of Figure la. The embodiment according to Figure 1 is, nevertheless, also feasable here.

Another difference as compared with the embodiment of Figure 1 is the arrangement of soft resilient joints in the region of the ball-and-socket joint. A first sealing ring 62 consisting, for example, of ceramic fibers is 5 incorporated in the refractory of the socket 60 and closes the pasage way between the socket 60 and the tip of the ball-part 58. Another soft seal 64, also made of ceramic fibers, is arranged in the annular space between the lower 8 end of the metallic sheath 68 of the ball-part 58 and the cylindrical connection sleeve of the expansion joint 44.

This seal 64 is wedged between the edge of the socket and a peripheral collar 66 welded to the sheath 68.

The purpose of these joints 62 and 64 is essentially to stop or to reduce the penetration of hot air inside the expansion joints 44 in order to provide them a better protection against high temperatures. When the ball-part 58 is subjected to an axial shift relative to the connection piece 30, the lower edge of the sheath 68 may distort or even crush the seal 64 on one side, whereas on the opposite side, the collar 66 tends to compress the seal 64 in the axial direction. Given that the refractory joints are lacking elasticity, there is a risk that these shifts cause irreversible distortions, thus reducing their efficiency, The device according to Figure 2 shows another handicap, in so far as the refractory-steel sheath 68 is only extending to the limit of the cylindrical part of the ball-part 58. The refractory tip of the ball-part 58 is, 20 therefore, rapidly overladen with micro-cracks which are at the origin of a rapid wear and a breaking of the tip of the ball-part. The lack of support for the refractory of the tip of the ball-part 58 needs, furthermore, a relatively large radius of curvature R to avoid that the convex tip, 25 which is not supported by the sheath 68, has been tapezed too much. This, on its turn, is at the origin of the sharp edge between the cylindrical part and the convex part of the ball-part 58, and which risks to crush the seal 64 during the angular movements of the articulat 4 on.

Figures 3 and 3a show each one half of an articulation according to the present invention, the Figures being shown close to each other, so as to show an entire joint, of which the left part shows the version with the ball-part separated from the central conduit segment and of which the right part shows the ball-part being part of the cental conduit segment.

The Figures 3 and 3a show that the ball-part of the articulation according to the present invention 70, 70a is completely envelopped by its refractory-steel sheath 72, 72a, which extends to the base of the ball-part around its convex section. The manufacture of such a refractory sheath 72, 72a, in a single piece with a convex section is rendered possible by an artful manufacturing process, explained more in detail hereinafter. Compared to the state of the art examplified in Figure 2, the ball-part of the present invention has a less important radius of curvature, in the order of magnitude of half a diameter of the connection conduit segments of the tuyere-stock, which improves its mobility. A seal 74, for example made of ceramic fibers, is provided between the ball-part 70, and the refractory of the tubular connection piece 76. This seal can, for example, be cemented to the armouring of the tubular connection piece 76 between two support rings 78, 80. The seal 74 adapts perfectly to the shape of the tip of the ball-part and extends to the major part of 20 the convex section of the latter. In case the tuyere-stock is designed to accomodate to a maximum axial misalignement of 70, the ball-part 72, 71 can deviate of 3,50 on both sides from its neutral position illustrated on the Figures 3 and 3a by the angles a and B. During such pn 25 extreme pivoting movement, the seal 74 always forms a thick sealing pad or cushion without being compressed by the ball-part 70, 70a, owing to the fact that the width of the S slot or grap remains constant during the relative swivelling.

i With reference to Figure 4, the process according to the present invention for making the refractory-steel sheath of a ball-part, will now be described. To this effect, a cylindrical pipe 82 made of refractory steel is used, which might be provided with a small peripheral flange 84, in the case of the embodiment shown in Figure 3.

All around the opposite side of the flange 84, at regular distances, cuttings following the generating line are made, with a depth corresponding to the length of the convex section of the ball-part to be made. These cuttings 86 thus define identical tongues 88, These tongues 88 are then folded down towards the axis of the pipe 82 until the cuttings 86 are completely closed, in order to define a spherical dome with a central opening 90 formed by the frontal bevels 92 of the tongues 88 juxtaposed to each other. This crimping of the tongues 88 can be carried out in a mould with a spherical bottom. The sheath 72 is then finished by welding the different tongues 88 one to the other over the whole length of the cuttings.

Figure 5 illustrates a first embodiment of the oblique section of a tuyere-stock with two identical ball-andsocket joints 94 and 96, each of which comprising a ballpart enveloped by a sheath made of refractory steel

E

manufactured according to the process described with :ceference to Figure 4. Figure 5 as well as the following S* Figures do not show, for reasons of simplicity, the means *0 20 for obtaining mechanical stability to the joints 94 and 96.

These means, although present in a specific embodiment, can .be means known per se, like cardan-joints or tension rods as disclosed in the European Patent EP-A1-0363576.

Figure 5a shows an alternative embodiment already 25 described hereinbefore, according to which the ball-part of the lower joint 96a is separated from the central tubular conduit element 98ao In both the embodiments of Figures 5 and Sa the seled connection between the central element 98 and the lower 30 tubular connection piece 100 is performed by means of a 50 flange 102 at the upper end of the sheath of the ball-part.

The central element 98 comprises also an upper flange 104 beyond the expansion joint of the upper articulation 94 to conect the tuyere-stock to the bustle pipe (not shown).

In the embodiment of Figure 5 these flanges 102 and 104 are, moreover, necessary for manufacturing the three 11 elements separately, namely the central element 98, the lower connection piece 100 and the upper connection piece 106, which consists simply of the ball-part of the balland-socket joint 94. This manufacturing will now be described and illustrated with reference to Figures 6a, 6b and 6c.

Figure 6a shows the manufacturing of the refractory of the ball-part 106. For this purpose, the sheath 72 manufactured according to the process described with reference to Figure 4, is overturned onto a support 108, made for example of wood, the central opening preferably directed downwards. A cylindrical form 110, made for example of expanded synthetic material, is then introduced into the sheath 72 and hold in place, for example, by a plug 112 fastened to the support 108 and penetrating into an axial channel of the form 110. The only thing that remains to be done is casting the refractory material 114 into the annular space delimited by the S form 110 and the sheath 72, by using the latter as a mould.

20 Figure 6b shows the manufarturing of the central 0@ conduit element 98. Fo.C this purpose, the assembly formed by the armouring 116 of the central element with the sheath of the lower ball-part and the upper expansion joint is overturned, the flange 104 to the bottom, onto a 25 support 118; the ring 120 which delimits the placement of the joint of the upper articulation 94 closing the opening around the support. The upper profile of the support 118 is complementary to the form of the socket of the articulation 94. Thereupon a cylindrical form 122 madle of expanded synthetic material is axially placed c,.:to the .o support 118, and held in place by a plug 124. The only thing that remains to be done is to fill the annular space around the form 122 with refractory material.

Figure 6c shows the manufacturing of the lower connection piece. As in the case of Figure 6b, the armouring 126 of this tubular connection piece, including the expansion joint of the lower articulation, is overturned, the upper flange to the bottom, onto a support 128 identical to the support 118 used previously.

Then a form made of expanded synthetic material 130, of which the outer form corresponds to the inner channel of the finished tubular connection piece 100, is placed axially onto the support 128, and the space around the form 130 is filled with refractory material. It shall be noted that the three forms made of synthetic material 110, 122 and 130 may remain in place when assembling the tuyere-stock, since they will be consumed automatically when the tuyere-stck is put into operation.

Figure 7 shows a second embodiment of a tuyere-stock with a central tubular element 132, a lower connection ;E piece 134 and a ball-part 136. However, unlike the embodiment of Figure 5, the armouring of the central element 132 is connected by means of the expansion joint of the lower articulation to the armouring of the tubular connection piece 134. The flange 102 of the embodiment of 20 Figu:?e 5a consequently dil appeared, which allows a reduction of the manufacturing costs of the tuyere-stock.

On the other hand, since the tubular connection piece 134 cannot be separated from the central element 132, the manufacturing step shown by Figure 6c is no more possible 25 and other ingenious methods have to be employed in order to be able to cast the socket of the lower joint. To this effect, the refractory of the connection piece 134 is cast, in the example shown, in two successive operations, symbolized by the interruption 138. This will also affect 30 the design of the lower joint, particular of the socket of the tubular connection piece 134. Figures 8 and 9 show several embodiments.

Figure 8 shows the details of the ball-and-socket joint 140 between the central element 132 and the lower connection piece 134. The ball-part 142 is identical with the one of the previous embodiment, that is, provided with a refractory sheath made according to Figure 4. On the other hand, the socket 144 of the articulation 140 formed by the upper part of the refractory lining of the connection piece 134 is modified. In fact, as shown in Figure 8, the refractory lining forming the socket 144 is cast inside the cylindrical sheath 146 made of refractory steel and fitted coaxially inside the metal armouring of the tubular connection piece 134. The sheath 146 can be held in place by means of two rings 148 and 150 fixed respectively to the inner wall of the armouring and to the outer wall of the sleeve 146. The thermal insulation is obtained by means of a thick seal 152 made of ceramic fibers which is cemented to the inner surface of the armouring of the connection piece 134 and extends to the bottom between the ball-part 142 and the socket 144. Two annular supports 154 and 156, which are welded to the armouring or housing, ensure the support of the seal.

e" In the alternative embodiment according to Figure 9, the socket 144 is also arranged inside a sheath 158 made of 20 refractory steel, which compared to the embodiment of Figure 8 is longer than the sheath 146. The part of the sheath 158 which exceeds the refractory lining, is designed as a housing for the seal 160 made of ceramic fibers. The embodiment of Figure 9 in relation to that of Figure 8, has 25 the advantage that the seal 160 can be put in place before assembling the tuyere-stock, and can be inserted together with the socket 144. On the other hand, the embodiment of Figure 8, compared to that of, Figure 9, has the advantage of a better thermal insulation because of a seal_ 152 that is thicker than the seal 160.

Figure 9a shows a compromn.se solution between the :embodiments of Figures 8 and 9 in that the sheath 162 is also used as a housing for the seal 164, but is associated with an annular collar 160, which is welded to the inner surface of the armouring. The seal 164 can thus also be put in place onto the socket before assembling of the tuyere- 14 stock, as is the case in Figure 9, but unlike the latter the collar 166 forms a thermal bridge contributing to the heat dissipation from the seal 164 to the outer armouring.

With reference to Figures 10a, 10b and 10c, the manufacturing steps of the different elements of the tuyere-stock of Figure 7 will now be described, as it has been done previously with Figure 5, by also refering to Figures 6a to 6c. By way of example, it will be referred to the use of the embodiment shown in Figure 9.

Figure 10a shows the casting of the refractory into a sheath according to Figure 4 to make the upper ball-part 136. This step is identical to the one described with reference to Figure 6a and does not have to be explained further.

At this instant however the intermediary step 0*00:0 illustrated in Figure 10b is applied. This Figure shows the separated casting of the socket 144 of the lower articulation joint 140. First, the sheath 158 is placed onto a mould 168 made of wood, the housing provided for the 20 seal 160 (Figure 9) being directed to the bottom. The profile of the upper front of this mould 168 is complementary to that of the refractory lining of the socket 144. Then a form 169 made of expanded synthetic material corresponding to the opening of the socket 144 is 25 placed axially inside the sheath 158 onto the support 168, and the refractory material is cast between this form 169 and the sheath 158. Following the casting and the removal *av of the mould 168, the seal 160 (Figure 9) can be cemented 6. in its housing inside the sheath 158.

With a view to the casting of the central element 132, its metal armouring which is fixed to that of the connection piece 134 by means of the expansion joint, is overturned onto the upper flange. The casting itself of the element 132 is identical to the casting described with reference to Figure 6b, and the same moulds and forms will be used. When this casting is completed, the socket 144 cast as explained with reference to Figure 1 Ob and after the seal has been put in place, is introduced into the armouring of the connection piece 134 in order to place it on the ball-part 142 where it is held by the abutments 148 and 150. When the socket 144 is in place a form, not shown, defining the channel of the tubular connection piece 134, is placed on this socket 144, and the casting of the connection piece 134 is finished by filling the annular space between said form and the armouring of the tubular connection piece 134 with refractory material.

Figure 11 shows a third embodiment similar to the one shown in Figure 7 which comprises a central tubular conduit element 170 connected through an upper ball-and-socket articulation 176 to a ball-part 172 and thourgh a lower ball-and-socket articulation 178 to a tubular connection piece 174. The lower connection piece 174 and the lower articulation 178 are identical with the embodiment of Figure 5 and, thus, do not have to be described further.

The central element 170 is analogous to the one of the 0.

embodiment of Figure 7 insofar as it does not comprise a flange for its connection to the tubular connection piece 174. In order to solve, in the embodiment of Figure 11, the manufacturing and assembly problems as explained with reference to Figure 7, a removable or 25 detachable link or connecting piece is provided between the armouring of the central element 170 and that of the e0 0 tubular connection piece 174. As shown by Figure 11, an upper end 180 of the expansion joint 182 is welded to the 6 armouring of the central conduit element 170 through a metallic shoulder member 184 onto which is also welded the sheath of the ball-part of articulation 178. The solidity of the welding of the met er 180 to the shoulder 184 must be a compromise between the necessity to be able to remove the welding in case of dismounting, on the one hand, and the necessity to ensure the sealing and to restrain the internal pressure, on the other hand.

The embodiment of Figure 11 has the advantage of the same simplicity in manufacture as the embodiment of Figure 5, that is, there is no need to cast the lower connection piece in two steps, and it also has the *advantage the advantage of the embodiment of Figure 7, to save the linking flange between the central element and the lower connection piece. However, the embodiment of Figure 11 needs a welding that must resist the internal pressure.

The different casting steps of the elements of the embodiment of Figure 11 as illustrated by Figures 12a, 12b and 12c, correspond exactly to those disclosed with reference to Figures 6a, 6b and 6c, and thus do not have to be explained further; the same forms and moulds being used.

The only difference lies in the absence of a flange on the connecting element 180 of the expansion joint 182 and in 0:4 the absence of a flange on the central element 170, which is replaced by shoulder 184. Following the casting of the three elements 170, 172 and 174 according to Figures 12a, 12b and 12c, the seal of the lower 4 ,articulation 178 is put in place by cementing it to the housing provided at the inner surface of the armouring of the connection piece 174 above the expansion joint 182.

Then the connection piece 174 is attached to the ball-part 25 of the central element 170 and the peripheral welding between the connecting element 180 and the shoulder 184 is made.

With reference to Figure 13 a fourth embodiment will now be described, which combines all the advantages of the three previous embodiments. The embodiment according to Figure 13 also comprises a central tubular element 200 MI. I. connected through an upper ball-and-socket joint to a ballpart 202 and through a lower ball-and-socket joint 208 to a lower connection piece 204. However, contrary to the previous embodiments, the two sockets of the articulations 206 and 208 are provided at opposite ends of the central element 200, the ball-part of the lower articulation 208 forming a part of the connection piece '204. The upper and lower articulations are thus positioned in opposite directions, as disclosed in the European Patent EP-A1-0363576, which also gives the advantages described in this document.

As shown in Figure 13, this embodiment saves the flange of the central element 200, without having to provide a removable weld between the armouring of the latter and the armouring of the lower connection piece 204 and without having to cast the tubular connection piece 204 in two steps as indicated in the description of the different manufacturing steps, which will be described hereinafter with reference to Figures 13a, 13b and 13c.

The manufacture of the ball-part 202 illustrated by Figure 13a is in accordance with the manufacture of the ball-parts of the previous embodiments.

Figure 13b shows the manufacture of the central element 200. The metal armouring of the element 200, which S. 20 makes part of the one of the lower tubular connection piece 204, is placed onto a mould made of wood which hol s it through the housing of the seal of the lower articulation 208. The mould 210 is supported by a base 212 which is, preferably, provided with a base element 25 supporting the armouring of the connection piece 204 through an inner stop 216 which will thereafter serve as a fixing support for the sheath of the ball-part. The profile of the upper front of the mould 210 is complementary to that of the socket of the lower articulation. Thus, a form 218 made of expanded synthetic material and corresponding to the inner channel of the central eleent 200, has merely to be placed axially inside the 0 armouring of the element 200 and on the mould 210. Then the annular space between the form 218 and the armouring has to be filled to the brim of the housing of the seal of the upper articulation 206. The profile of the socket 220 of 18 the upper articulation is formed in the cast refractory material by removing the cast material before it hardens, for example with a strickle having a profile complementary to the one of the socket 220. The structure thus made in accordance with Figure 13b is then turned over and placed on a base 222 which consists preferably of a mould made of wood used to model the socket of the articulations. The structure is carried by the socket 220 on the mould 222.

The seal 224 is subsequently put in place by cementing it in its housing provided to this effect on the inner surface of the armouring of the element 200. A disc 226 made of expanded synthetic material is then placed at the bottom of the socket-part previously formed by the mould 210 in Figure 13b, the thickness of the disc corresponding to the axial width of the transverse slot of the articulation 208 between its ball-part and socket. The sheath of ball-part 72 is then introduced from above into the armouring of the connection piece 204 by placing it and •welding it by its edge 84 onto the stop device 216 provided on the inner surface of the armouring. A form made of *expanded synthetic material is then placed axially on the disc 226, the configuration of the form corresponding to the passage channel of the tubular connection piece 204.

All that needs to be done then is to cast the refractory 25 material into the annular space around that form, by using the sheath 72 as a mould. After the removal of the mould 222 and of the plugs 228 and 330 used to maintain the inner forhms during the casting, the central element 200 and the tubular connection piece 204 are ready for assembly, 30 the inner forms as well as the disc 226 can stay in place c* given that they will be used up automatically when the tuyere-stock is put into operation.

A

Claims (13)

1. A device for injecting preheated air into a shaft furnace, consisting of a plurality of separate cylindrical elements, each consisting of an external steel armouring and an inner refractory lining, and including at least one central tubular element connected, on one side, by a first ball-and-socket articulation and a first expansion joint to an upper tubular connection piece firmly attached to a preheated air feeding bustle pipe encircling the furnace and, on the opposite side, by a second ball-and-socket articulation and a second expansion joint to a lower tubular connection piece extended by an elbow member and a nozzle, the latter being articulated on a tuyere fixed to the wall of the furnace, and in which the ball-and-socket articulations include a convex ball-part formed by the end of one of the elements pivoting in a concave socket formed by the end of the adjacent element and a soft refractory seal insert, wherein the radius of curvatur ef each OVfoLAAe.( oysi of the ball-and-socket joints isn t r f magnitude of half of theAdiameter of the different tubular elements and wherein the convex ball-parts of the ball-and- S socket articulations include a protective sheath made of refractory steel which extends around the convex part of the diametral base of the ball. 11*

2. The device according to claim 1, wherein the ball-parts are formed by the lower ends of the upper tubular connection piece and of the central tubular element. 0

3. The device according to claim 1 or claim 2, wherein the ball-part of the S central tubular element is an integral part thereof.

4. The device according to claim 1 or claim 2, wherein the ball-part of the central tubular element is separated from it by a transverse junction filled with an annular seal. S

5. The device according to any one of the preceding claims, wherein the metal armouring of the central tubular element is connected to a lower tubular connection piece by freans of the mnsion joint and a flange.

6. The device accordirg tc 1 or claim 2, wherein the armouring of the central tubular element and one of the lower tubular connection pieces are directly connected to each other through the expansion joint.

7. The device according to claim 1 or claim 2, wherein the armouring of the central tubular element and the lower tubular connection piece are connected to earh other by a detachable weld between the connecting element of the expansion joint and a peripheral shoulder.

8. The device according to any one of claims 1 to 6, wherein the socket of the second articulation is formea In the refractory lining cast in a cylindrical sheath made of refractory steel, which sheath is arranged coaxially inside the armouring of the lower tubular connection piece.

9. The device according to claim 8, wherein the refractory seal is fixed partially to the armouring of the tubular connection piece and partially to the edge of the socket. The device according to claim 8, wherein the refractory seal is fixed S partially to an inner housing of the cylindrical sheath and partially to the S refractory.

S.t

11. The device according to claim 8, wherein the al is attached partially to the refractory and partially to a housing delimited by the upper part of the sheath and by a ring welded to the inside of the armouring of the tubular connection piece.

12. The device according to any one of the preceding claimsi, wherein the socket-parts of the two ball-and-socket articulations are provided spectively at both opposite ends of the central tubular element, whilst the convex ball-parts are provided on the upper tubular connection piece and the lower tubular connection piece. S.26 A-peess-for-manufacturing-enV articulations of a device for injecting preheated air into a shaft consisting of first making the ball-part sheath of refract e -s and providing it with an inner refractory lining, wher 'end of a tubular element made of refractory steel is forrtir it has the shape of a convex dome with a central opening and a convex spherical surface extendg between the cenal- .opening- and the 21

13. A device for injecting preheated air into a shaft furnace, substantially as described herein with reference to the accompanying drawings. DATED this day of April 1993. PAUL WURTH S.A. By their Patent Attorneys: CALLINAN LAWRIE I. 9* 6* @0 @999 @9 99 9 9 9 *999 9 9@9@