US2294946A - Skewback - Google Patents

Description

- Sept 3, 1942- c. H. ALDRlcH SKEWBACK Filed Oct. 6, 1959 @fr w QNNMAQNN Patented Sept. 8, 1942 UNITED STATES arg1 orric sKEwBAcK Application October 6, 1939, Serial No. 298,172

7 Claims.

This invention relates to improvements in skewbacks for reverberatory refining furnaces and for other furnaces having arched roofs, and relates more particularly to skewbacks which include means for circulating therethrough a cooling medium such, for example, as water or other fluid.

The eicacy of skewbacks in furnace structures resides chieiiy in their capacity for withstanding the heat of the furnace over relatively long periods of use without burningr away, and for withstanding the end thrusts of the furnace roof without becoming deformed. Skewbacks lacking either of these qualities quickly fail of their purpose and make it necessary to frequently shut down the furnace for repairs with consequent attendant expense.

It has heretofore been the practice to employ water-cooled skewbacks of metal in place of specially-shaped skewback bricks of refractory material. Such prior Water-cooled skewbacks, however, have been formed of iron or other metals of sufficient strength that, either in the form of castings, or as hollow sections with stays incorporated therein, the skewbacks were strong enough to withstand the stress -of the enormous end thrust of the furnace roof.

Iron and other common metals, capable of withstanding such stresses when in a heated con- ,3.0

dition, possess certain characteristics which are decidedly disadvantageous with respect to watercooled skewbacks. One disadvantage is that iron, steel and other simila1` metals heretofore used in skewbacks do not possess a Very high` degree of heat conductivity and, hence, where such metals are employed, the transfer of heat from a part of a skewback, subjected to the furnace heat, to water passing through the skewback, is not as rapid as may be desired.

Further serious disadvantages, encountered in using such metals, are that they are subject to corrosion and that rust, scale and residue from water adheres to water passage surfaces of such metals, thus seriously impairing heat transfer f even cooling or sudden temperature changes,

thus causing water leaks and failure of back.

It has been proposed to imbed iron pipes into a skewback casting in the formation thereof so that if the casting were to crack there would be no leakage of the cooling medium. Under this expedient, however, the heat transfer from the the skewcasting to the cooling liquid within the pipes is greatly diminished by reason of the fact that the said pipes are not homogeneously formed with the skewback casting.

It has also been proposed to form water-cooled skewbacks of sheet metal, suitably trussed interiorly and welded together, but the water passages in such structures are relatively large in cross-section and hence, the cooling medium, practically, may only be circulated therethrough at a relatively low velocity. Thus, such sheet metal skewback structures, lacking the flushing effect of high Velocity of the cleaning medium, permit serious accumulation therein of rust, scale and residue from the water. At places where such accumulation occurs, heat transfer is inadequate, and the skewback soon burns away, whereupon leaks develop and repair or replacement becomes necessary.

An important object of the present invention is the provision of a water-cooled rskewback structure which is of sucient strength to withstand roof stresses and wherein there is afforded rapid and substantially uniform dissipation of heat whereby to -prevent the skewback or portions thereof from burning away. Other objects will be apparent from the following specification.

I achieve the foregoing and other objects by forming the skewback of a metal member of relatively high heat conductivity, such, for example, as a copper casting, and by providing one or more passages therein through which a cooling medium, preferably water, may be passed at sufficient velocity to effectively cool the skewback whereby to enable it to withstand the heat to which it is subjected.

Where the copper casting or other cooled metal member, in which water passages are provided, is of such a character that it would not alone be adapted to receive the end thrusts from the furnace roof without becoming deformed, a reinforcing member may be provided and may be suitably fastened to one or more of the cooled metal members if it is desired to have a unitary skewback structure. The water-cooled metal member and the reinforcing member are preferably so arranged that the former member completely protects the latter from the furnace heat.

The present invention may best be understood by reference to the illustrative embodiments shown in the accompanying drawing, in which:

Figure 1 is a transverse vertical section of the upper part of a furnace, showing one embodiment of my invention employed at the rear (left side) of the arched roof, and another embodiment employed at the front (right side) of said rOOf.

Fig. 2 is an enlarged detail view, in transverse vertical section, of one embodiment of my invention shown in Fig. 1.

Fig. 3 is an elevational view of an upper portion of the furnace as viewed fromA the front thereof, parts being broken away to show details.

Fig. 4 is an enlarged detail view, in transverse vertical section, of the other embodiment of my invention shown in Fig. 1.

Referring first to Fig. 1, the furnace may comprise a rear wall I9 and a front wall II, both of suitable refractory material. These walls may be surmounted by an arched roof I2, preferably formed of a plurality of specially shaped refractory blocks, and the outer side surfaces of the marginal blocks of the roof may rest against skewbacks, generally indicated as I3 and I4, at the rear and front, respectively, of the furnace. The said skewbacks may be restricted against moving apart by vertical buckstays I5, which may be in the form of steel I-beams, connected by transversely arranged tie rods I6 (only one being shown), extending over the roof of the furnace and by similar tie rods (not shown), extending underneath the furnace hearth. In this way the front and rear buckstays are prevented fromspreading apart and thus, through the skewbacks I3 and I4, receive the thrust of the roof I2. Doorways I1 (only one being shown) are ordinarily provided in the front wall I I of the furnace, and a suitable door (not shown) is provided to close said doorway.

The horizontal thrust generated by the weight of the roof is quite substantial, and any failure of the skewbacks which receive such thrust renders it necessary to shut down the furnace for repairs. If a skewback becomes distorted under the force of this thrust, orif it burns away to any appreciable extent, the roof will sag and collapse if not promptly serviced.

According to my invention, the skewback is of ample strength and rigidity to carry the thrust of the roof without objectionable distortion and is effectively cooled so that it will resist the burning effect of the heat within the furnace and will yield relatively long service and minimize repairs.

Describing first the embodiment illustrated in Figs. 2 and 3, skevvbacks, according to my present invention, may preferably be made in a number of separate sections I8, which, as best seen in Fig. 3, may be arranged end to end and extend throughout the lengthV of the furnace. Each such skewback section may comprise two cooled members I9 of metal of high conductivity, such, for example, as copper castings. These members I9 may be arranged end to end and may be in the shape of an acute angle in crosssection with a substantially horizontal base por-tion 2l! which extends over the front wall II and the doorways I1. The members I9 also may have an angularly-disposed upstanding portion 2|, having an outer angular face 22, upon which the marginal blocks of the roof I2 rest whereby to derive support. The faces 22 may be formed in a rough finish, or may be given a rough finish after formation, whereby to provide a rm engagement with the marginal blocks of the roof and prevent relative movement between the two. The rough finish, referred to, preferably should be such as is produced by a coarse planer cut and, in any event, must not be rough enough to injure the marginal blocks of the roof.

Each cooled member I9 is preferably provided with a plurality of longitudinal fluid pas sages 23, which may extend substantially throughout the entire length of said member and may be interconnected in parallel relationship by horizontal transverse passages 24 near each end of the base portion 2D and by upwardlyextending passages 25 in the upstanding portion 2I near each end thereof.

The passages hereinbefore referred to ma preferably be formed by drilling, the longitudinal passages 23 preferably being so drilled that they terminate a short distance from one end of the member I9, and the horizontal transverse passages 24v and the upwardly-extending passages 25 preferably being drilled from the free edges of the portions 20 and 2l, respectively, to an intersecting point near the heel of the member I9. The passages 24 and 25 are so drilled that they pass through and connect the ends of the longitudinal passages 23. The open ends of the passages 23 and 24 may be closed by screw plugs 26, and the open upper ends of the passages 25 may be screw-threaded to receive inlet and outlet pipes 2'! and 28, respectively. The said pipes are preferably connected to separate inlet and outlet manifolds (not shown) in a well understood manner. Although the several longitudinal passages are hereinbefore described as being connected in parallel, they, nevertheless, may, if desired, be so connected as to form a single continuous passage extending throughout the cooled member I9 in any embodiment of the invention.

As a cooled member I9 of copper or other material of relatively high conductivity may not in itself have suflcient strength to withstand the stresses incident to supporting the roof of the furnace, I provide a reinforcing member 29 which is strong enough to afford adequate rigidity to the roof-supporting structure. As illustrated in Fig. 2, this `reinforcing member 29 may be channel-shaped somewhat complementally to the inside angle of the cooled member I 9, and may be securely bolted inside the said inside angle of two endwisely arranged cooled members I9 by bolts 39, which extend through suitable holes provided for the purpose in the said members. Recesses 3| are provided in the members I9 to accommodate the heads of the bolts 30 so that the latter will lie below the surface of the face 22 of said member.

The length of the reinforcing member 29 of each skewback section I8 may advantageously be equal to the combined lengths of two endwisely arranged cooled members I9, and flanges 3| and 32 of the member 29 preferably extend throughout the length of the latter and may also be integrated by end flanges 33 which afford additional rigidity to the skewback structure. Such a skewback section, thus, may be of sufcient length to bridge the doorway II while the length of the cooled members I9 and of the horizontal passages 23 therein may be sufliciently restricted that the drilling of said passages is rendered practicable. The reinforcing member 29 may be of cast steel or other suitably strong metal and preferably is completely shielded or protected from the furnace heat by the cooled members I9.

The skewback sections I8 are preferably' hung by rods 40 from suitable brackets il which are riveted or otherwise iixed to the buckstays I5. Each of said rods passes through suitable holes in a flange of the bracket 4I and in the flange 3l (Fig. 2) of the reinforcing member, nuts 42 being threaded onto each end of said rod whereby to support the skewback. The threads on the ends of the rods 40 are long enough to permit desired vertical adjustment of the skewbacks. By this arrangement the furnace walls may be relieved of the weight of the furnace roof. The ends of the several skewback sections I8 maysubstantially abut at points behind the buckstays I5, as best seen in Fig. 3, and thus be held securely, by the latter, against displacement. Under this arrangement it will be seen that the skewbacks along the front of the furnace may serve as lintels for the doorways, and as the cooled base portion 20 of the cooled member I9 can withstand the furnace heat, the need for brickwork doorway arches is obviated.

In practice, water may be passed through the skewback members I 9 at a sufciently high velocity to eiectively carry olf heat therefrom, and the high conductivity of said members permits them to be maintained at a substantially uniform and low enough temperature to enable them to resist the burning effect of the heat. This is true even though, as shown in Figs. 2 and 3, the base portion 29 may be fully exposed to such furnace heat at the doorways of the furnace.

In the embodiment illustrated in Fig. fl, the cooled member 34 is substantially rectangular in cross-section and, in the particular form used for the purpose of illustration, is only provided with two horizontal water passages 23, connected at each end by vertical passages 35 into the upper ends of which may be screwed the water pipes connecting the skewback to the water manifolds. A specially-shaped skewback brick Sii may be interposed between the coole-d member 35 and the adjacent marginal roof blocks. The inner face of the member 34 is preferably offset as at 3l to prevent downward shifting of the brick 3S, and, to this end also, the inner face of the member 34 may be given a rough finish, as already explained with reference to the face 22 in the embodiment iV f Fig. 2.

A reinforcing member (serving a similar purpose to that served by the member 29 of Fig. 2), is provided, and may comprise a heavy, horizontal, steel plate 38, having horizontal stiffening i" beams 39 riveted to the outside thereof. The reinforcing member and the cooled member 3l! may be bolted together similarly to comparable parts of the structure shown in Fig. 2. The beams 39 are preferably shorter than the plate 38 and the structure is so arranged that the ends of said beams substantially abut the edges of the inner flanges of the buckstays I while the plates 38 of skewback sections extend and substantially abut behind said buckstays whereby they are restrained against outward movement. The skewbacks illustrated in Fig. 4 similarly to those illustrated in Fig. 2, may be hung upon brackets 4I on the buckstays, by rods 40, the latter, however, being connected to the skewback through the medium of angle brackets 43, riveted to or otherwise suitably secured to an upper marginal portion of the reinforcing member 3S.

lIt should be observed that, in both illustrated embodiments, a cooled skewback portion is disposed nearest to or exposed to the furnace heat and is of metal of relatively high conductivity. It is provided with water passages which are relatively small in cross-section so that water may be passed therethrough at sufficient velocity to rapidly and effectively carry olf heat, whereby to keep the temperature of the said metal portion low enough to enable it to resist the burning effect of the furnace heat. lAlso, in both said embodiments, the said cooled portion constitutes a shield which protects the reinforcing members against the furnace heat. By thus combining such cooled members and reinforcing members, a sturdy skewback structure is derived which resists distortion, cracking, burning away, leaks, etc., and is highly economical to maintain.

Without foreclosing other materials and eX- pedients, I have hereinbefore recommended that the so-called cooled members be of copper and that the various water passages be drilled therein. Copper has suflicient conductivity for all practical purposes of the present invention, and, by its use, corrosion and scaling are eliminated. Copper, also, will not crack when used as described herein, and thus thewater passages may be formed directly in the copper without incurring the danger of leaks from cracks. Thus, by using copper instead of metals of lower conductivity, I obviate the necessity of employing separate pipes as water conduits in the skewback and avoid the losses in heat exchange between such separate members which, in constructing the furnace, may be assembled in proper relationship and thereafter held together by forces communicated from the adjacent roof, furnace walls and buckstays. Under the latter arrangement the several parts may be arranged, in various ways, to interlock, whereby to Ymaintain their proper relationship.

It will be 'apparent from the foregoing that the principles involved may be employed in various ways without, however, departing from the spirit of the invention as deiined in the accompanying claims.

What I claim is:

1. A skewback structure for furnaces comprising a cooled member, having one or more fluidlcarrying passages therein adapted for connection to a circulating fluid supply system, and a reinforcing member for augmenting the strength of the cooled member, the latter being of metal of relatively high heat conductivity whereby to effect rapid heat transfer to fluid passing through said passages -but of insuicient strength to withstand the thrust of a 'furnace roof, intended to be supported thereby, without appreciable deformation, and said reinforcing member .being of material of suicient strength to enable the skewback structure to withstand the thrust of the roof of the furnace without appreciable deformation.

2. A skewback structure for furnaces comprising a .cooled member of metal of relatively high heat conductivity, having one or more fluid-carrying passages therein adapted for connection to a 'circulating fluid supply system, `and a reinforcing member fastened to said cooled member for augmenting the strength of the latter, the said cooled member having insufficient strength in itself to withstand theY thrust of the roof of the furnace and the said reinforcing member being of metal of sufficient strength to enable the skewback structure to withstand the thrust of the roof of the furnace without appreciable deformation.

3.I A skewback structure for furnaces, comprising an elongated cooled lmember of non-corrosive metal of relatively high heat conductivity and of insufficient strength in itself to withstand the thrust of a :furnace roof without material deformation and an elongated reinforcing member, -for reinforcing the cooled member, the latter having a bottom face, and also an upwardly-extending face adapted for engaging a marginal portion of a furnace roof, and said cooled member also having therewithin one or more fluid-carrying passages disposed near to both said faces..

4. A skewback structure lfor furnaces, comprising a cooled member `formed of copper, and having one or more fluid passages therein adapted for connection to a `circulating fluid supply system, and la reinforcing member formed of a dift ferent and less easily deformable metal than said pooled member, the said cooled member having insufcient strength in itself to withstand the thrust of a furnace roof and the said reinforcing member being fastened to the cooled member and being adapted to back the cooled member whereby to enable the latter to receive the thrust of Y an arched furnace roof without substantial deformation.

5. A skewback structure for furnaces, comprising an elongated cooled member of metal of substantially high heat conductivity, having a substantially horizontal base flange and an upright flange extending upwardly at an acute angle from the inner margin of the said base flange, an elongated, channel-shaped reinforcing member, of less easily deformable metal than that of the lcooled member, having a web and flange engaging the inner sides of the flanges of the 'cooled member and being secured to the latter whereby to strengthen it, the horizontal and upright flanges of the cooled member being adapted, respectively, to rest upon a furnace Wall and to receive the thrust of aan arched furnace roof and the said reinforcing member being adapted to engage furnace stays and transmit the roof thrust thereto..

Y 6, In combination in furnaces, side wall sections defining opposite sides of a charging doorway, upright buckstays disposed outside of and adjacent to each of said wall sections, an arched roof, and a skewback structure disposed between the buckstays and the roof for supporting the latter, the skewback structure comprising a unitary structure extending behind said buckstays and over the charging doorway and constituting a lintel for the latter, the said unitary structure comprising a plurality of endwisely disposed, elongated cooled memlbers, of copper, each having a fluid-cooled flange defining a portion of the top of said doorway, a huid-cooled flange adapted to engage the furnace roof, and a reinforcing member secured to and connecting said cooled members together as a unit of sufficient length to extend completely across said doorway and partially behind said buckstays.

7. A skewback structure according to claim 1, yfurther [characterized in that said cooled member is disposed between the interior of the furnace :and the said reinforcing member, whereby to shield the latter from the furnace heat.

CHARLES H. ALDRICH.

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