THERMALLY INSULATING BLOCKS

Abstract: A thermally insulating block (1) for use in lining the roofs, walls, floors, doors and ducting in furnaces, kilns, ovens or the like, comprising a plurality of strips (2), prefer­ ably of U-shaped section, of a low thermal mass material, which are secured together under compression and in side-­ by-side realtionship, by retaining means (3) capable of with­ standing the operating temperature of a furnace, kiln, oven or the like in which the block (1) is used as at least part of an inner lining thereof. Preferably, the retaining means is in the form of a flexible thread or cord (3) extending through the interior of the block generally transversely with respect to the strips. The invention also includes methods of making the block, one preferred method comprising the steps of folding a layer of low thermal mass material to form a corrugated block of the material, truncating the so-formed corrugations on at least one major face of the block to form a series of strips in side-by-side relationship, transversely compressing the elongate strips together, and maintaining the so-compressed strips under compression with retaining means capable of withstanding the operating temperature of a furnace, kiln, oven or the like in which the manufac­ tured block is used as at least part of an inner lining thereof.

Description: THERMALLY INSULATING BLOCKS DESCI PTION This invention relates to thermally insulating blocks for use in lining the roofs, walls, floors, doors and ducting in furnaces, kilns, ovens and the like. A known furnace lining comprises an inner layer of a plurality of thermally insulating blocks each formed from individual rectangular strips of low thermal mass material stacked adjacent one another and wrapped, under compression, in cotton or other scrim cloth which burns up when the blocks are first used. A disadvantage associated with this known form of thermally insulating block is that the cotton or other scrim cloth is under tension, when wrapped around the block to retain the low thermal mass strips under compression, which does not permit sufficient flexing of the block when it is being secured to a curved or uneven surface of an inner wall of a furnace,kiln, oven or the like. Another disadvantage is that the cotton or other scrim cloth burns up when the block is first used, thereby eliminating or at least substantially reducing the compressive forces holding the low thermal mass strips together, thus resulting in the eventual break-up of the block. The present invention sets out to eliminate, or at least substantially avoid, these disadvantages associated with known thermally insulating blocks by providing, in accordance with one aspect thereof, a thermally insulating block comprising a plurality of strips of a low thermal mass material which are secured together, under compression and in side-by-side relationship, by retaining means which is capable of withstanding the operating temperature of a furnace, kiln, oven or the like in which the block is used as at least part of an inner lining thereof. Preferably, said retaining means is flexible, in which case, it may be in the form of a thread or cord made from the same low thermal mass material as that of the strips. Such flexible thread or cord may extend around the exterior of the block, to retain the strips under compression and in side-by-side relationship, or may be threaded transverselyF in a back and forward fashion, through the compressed strips, as long as the thread or cord is capable of withstanding the operating temperature of a furnace, kiln, oven or the like in which the block is installed as at least part of the inner liner thereof. In this latter embodiment, wherein the flexible thread or cord passes transversely through the block, its inherent flexibility permits the block to be flexed during installation, thus permitting it to be secured to the contour of a curved or uneven surface of an inner wall of a furnace, kiln, oven or the like. Alternatively, however, sad retaining means may be in the form of at least one "skewer" passing transversely through the compressed and side-by-side low thermal mass strips, such a skewer preferably being made of a metallic material which can withstand the operating temperature of the furnace, kiln, oven or the like In one preferred embodiment of the inventive thermally insulating block, the low thermal mass material, from which the strips are made, is a refractory fibre of alumina and silica suitable for continuous exposure to operating temperatures of 12600C (23000F). A suitable material for operating at a higher temperature of, say, 14250C (26000F) is a fibrous refractory material of an alumina, silica and chromia composition. As indicated above, said retaining means, and preferably when in the form of a thread or cord, can also be made of either fibrous refractory material. In a further preferred embodiment of the inventive thermally insulating block, the strips are U-shaped, thereby providing a block with one of its major surfaces corrugated and the other, planar. In accordance with another aspect of the invention, there is provided a method of manufacturing a thermally insulating block, comprising the steps of arranging a plurality of strips of low thermal mass material in sideby-side relationship, transversely compressing the strips together, and maintaining the so-compressed strips under compression with retaining means which is capable of withstanding the operating temperature of a furnace, kiln, oven or the like in which the manufactured block is used as at least part of an inner lining thereof. In a preferred embodiment of the inventive method, there is provided the steps of folding a layer of low thermal mass material to form a corrugated block of said material, truncating the so-formed corrugations on at least one major face of the block to form a series of strips in side-by-side relationship, transversely compressing the strips together, and maintaining the so-compressed strips under compression with retaining means which is capable of withstanding the operating temperature of a furnace, kiln, oven or the like in which the block is used as at least part of an inner lining thereof. As a modification of this method, the transverse compressing and maintaining under compression steps may precede the corrugation truncating step. The thermally insulating blocks, in accordance with the invention or when made by a method in accordance therewith, can be secured to the inner surfaces of, say, a furnace, by cementing one of the major surfaces thereof and then pressing this surface against the furnace wall in the required position. In the case of the corrugated block having U-shaped strips, it is the planar major surface which is preferably secured to the internal surface of the furnace wall. A preferred embodiment of thermally insulating block in accordance with the invention, as well as its inventive method of manufacture, will now be described by way of example and with reference to the accompanying drawing which shows a perspective view of the block. In the drawing, a thermally insulating block 1, for use in lining the inner surfaces of a furnace wall, comprises a plurality of U-shaped strips 2 of a low thermal mass material which are secured together under compression by a retaining thread 3. This retaining thread 3 passes along the outside surface of the U-shaped strip 2 at the left hand side of the block 1, through the block at four positions transversely with respect thereto, and along two portions of the outer surface of the U-shaped strip at the right hand end of the block The thread 3 retains the strips 2 under transverse compression and it is to be understood that any other suitable form of retaining means, such as, at least one transverse rod, may be used instead of the thread 3, as long as it is capable of withstanding the operating temperature of the furnace. In a modified form of the block 1, a scrim cloth of the same material as that from which the strips 2 are made, is wrapped around the block, preferably leaving the opposed end faces of the U-shaped strips 2 exposed. Such wrapping can be adhesively secured to the block 1. In themanufacture of the block 1, a single layer of low thermal mass material, such as either of those described above and capable of withstanding respective operating temperatures of 12600C (2300"F) and 14250C (26000F), has been folded to form an intermediate corrugated block. One major face of the intermediate block has then had its corrugations truncated, thereby forming the plurality of side-by-side, generally U-shaped strips 2 which are subsequently subjected to a transverse compressional force. Alternatively, and as also indicated above, this truncation step may follow the compression and retaining steps. In this compressed state, the thread 3 passes transversely through the strips 2 and is secured in a suitable manner to maintain the block 1 under compression. It will be appreciated that such a block 1 could also be made by forming two or more intermediate blocks, of equal thickness, which may then be secured together in side-by-side relationship under compression. The or each block 1 can then be fixed to the internal surface of a furnace wall by cementing the planar, truncated face thereto. Also, it will be appreciated that the transversely compressing and maintaining under compression steps can be formed simultaneously, and preferably when the retaining means is in the form of a flexible thread or cord passing transveresely through the side-by-side strips, whereby tightening or tensioning of the thread or cord 3 actually compresses the strips together and, then, subsequently retains them in the compressed state.

Claims: CLAIMS 1. A thermally insulating block (1) for use in lining the roofs, walls, floors, doors and ducting in furnaces, kilns,ovens or the like, comprising a plurality of strips (2) of a low thermal mass material, which are secured together, under compression and in side-by-side relationship, by retaining means (3), characterised in that said retaining means (3) is capable of withstanding the operating temperature of a furnace, kiln, oven or the like in which the block (1) is used as at least part of an inner lining thereof 2. A thermally insulating block (1) according to claim 1, wherein said retaining means (3) comprises a flexible thread or cord. 3. A thermally insulating block (1) according to claim 1 or 2, wherein said retaining means (3) extends through the interior of the block (1) generally transversely with respect to the plurality of strips (2) of low thermal mass material. 4. A thermally insulating block (1) according to any preceding claim, wherein the plurality of strips (2) are made of a fibrous refractory material containing alumina and silica. 5. A thermally insulating block (1) according to claim 4, wherein the fibrous refractory material also contains chromia. 6. A thermally insulating block (1) according to any preceding claim, wherein said retaining means (3) is of the same material as that of the strips (2). 7. A thermally insulating block (1) according to any preceding claim, wherein the strips (2) are generally U-shaped, whereby one major surface of the block is corrugated and the other major surface of the block (1) is planar. 8. A furnace, kiln, oven or the like having a lining of which part comprises one or more blocks (1) according to any preceding claim. 9. A method of manufacturing a thermally insulating block (1), comprising the steps of arranging a plurality of strips (2) of low thermal mass material in side-by-side relationship, transversely compressing the strips (2) together, and maintaining the so-compressed strips (2) under compression with retaining means (3), characterised in that said retaining means (3) is made of a material capable of withstanding the operating temperature of a furnace, kiln, oven or the like in which the manufactured block (1) is used as at least part of an inner lining thereof. 10. A method of manufacturing a thermally insulating block according to claim 9, wherein the plurality of strips (2) are formed by folding a layer of low thermal mass material to form a corrugated block (1) of the low thermal mass material and truncating the soformed corrugations on at least one major face of the block (1) to form said series of strips (2) in side-bvside relationship. 11. A method accordina to claim 9 or 10, wherein said retaininq means (3) is provided as a flexible thread or cord. 12. A method according to anv of claims 9 to 11, wherein said retaining means (3) is passed through the interior of the block (1), such that it extends generallv transversely with respect to the plurality of strips (2) of low thermal mass material. 13. A method according to any of claims 9 to 12, wherein the plurality of strips (2) are made of a fibrous refractory material containing alumina and silica. 14. A method according to claim 13, wherein the fibrous refractory material also contains chromia. 15. A modification of the method according to any of claims10to 14, wherein the transversely compressing and maintaining under compression steps performed upon the strips (2) precede the corrugation truncating step. 16. A method according to any of claims 9 to 14, cra a modified method according to claim 15, wherein the transversely compressing and maintaining under compression steps are performed simultaneously when said retaining means (3) is applied to the side-by-side strips (2).

Inventors: WATKINS, MELVYN ALAN
Applicants: FUEL CONSERVATION SERVICES LIMITED
Application year: 1983
Main classification: F27D1
IPC codes: F27D1