Method for providing high temperature internal insulation

Abstract

A ceramic fiber mat attached to the interior wall or surface of a high temperature chamber of furnace or adapted to overlie an intermediate insulating member positioned between the mat and a furnace wall, the fibers in the mat lying in planes generally perpendicular to the wall, the mat constituting an improved insulation for the wall where the interior of the chamber or furnace will be operating at temperatures in excess of 1600° F.

Description

This is a continuation of a divisional application, Ser. No. 445,807, filed Feb. 25, 1974 now abandoned, divided from parent application Ser. No. 157,433, filed June 28, 1971, now U.S. Pat. No. 3,819,468.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application briefly describes, but does not claim, a method and apparaus for welding which is more fully described and claimed in U.S. Pat. No. nxt next step in the assembly of the insulating member involves the installation of the stud which will now be described. The stud comprises a central shank 38 having nut 40 threadedly mounted at the upper end thereof. A washer 42 is provided on the shank 38 immediately below the nut 40. When installed, the washer 42 will rest against the upper surface of the block 28. The lower end of the shank 38 is provided with a stud tip 44 of relatively smaller cross sectional area. Also mounted on the lower end of the shank 38 are a ring retainer 46 received in the groove 48 and a ring-shaped ceramic arc shield 50 which is secured to the ring 46 by cement or in any other suitable manner. The purposes of the forgoing elements will be described hereinafter in greater detail.

At any event, after the stud (with associated elements attached) is inserted into the hole 36 in the manner described above, the prior assembly of parts 22', 34 and 24 are placed over the block 28 with the lower parts of the side strips 34 overlying the two longitudinal side edges of the block 28. Four hairpin-type stainless steel fasteners 30 (two for each wire 24) are now inserted into the seams between the strips 22' so as to engage the wires 24. These fasteners 30 are driven through and clenched against the back surface of the block 28. By providing a hard surface, preferably steel, below the block 28 when the fasteners 30 are inserted, the lower ends of these fasteners will clench towards each other as shown in FIG. 5. When the tool (not shown) for inserting the fasteners 30 is withdrawn from the seams, the strips 22' will return to their original position without leaving any gap or aperture because of the inherent resiliency of these strips.

The resulting insulation member, now complete, is ready for installation against a furnace wall 32 by means of a stud welding process which is more fully described and claimed in copending application "Method and Apparatus for Stud Welding" referred to above. The method and apparatus for stud welding (as described in the aforementioned copending application) forms no part of the present invention but is described briefly hereinafter merely to show one manner of attachment of the insulating member 20' to a furnace wall. A stud welding gun 52 is inserted into the central seam between the middle strips 22' until the lower end of the gun engages the nut 40 of the stud. The stud gun is triggered and current flows into the shank 38 and into the tip 44. The tip 44, because of its relatively small cross sectional area burns away and thus starts an arc. The stud shank 38 does not itself move at first because it is supported by the self-locking ring retainer 46 which is retained in the groove 48 as indicated heretofore. As best shown in FIG. 10, the ring retainer 46 is provided with a plurality of radial fingers 54 which project into the recess 48 to hold the ring 46 in position. As the welding operation continues, the intense heat of the arc burns away the fingers 54, thus allowing the stud shank 38 to plunge into the molten metal formed by the arc. At this point, the weld is completed and the gun can be withdrawn. It should be mentioned, however, that the ring retainer 46 and the fingers 54 thereon are carefully sized so that the fingers will burn away, melt, or soften in approximately two tenths of a second, or within whatever period of time is deemed appropriate, all as set forth more fully in the aforementioned copending application.

Now, it may be desirable to tighten the nut 40 on the shank 38. This can be done by merely rotating the gun about the vertical axis of the shank. It might be mentioned that the lower end of the gun (or extension thereof, if desired) is provided with a hexagonal opening corresponding to the size of the nut 40 and of sufficient depth to accommodate for the upper end of the shank 38 after the nut is tightened thereon. Thus the gun 52 serves a secondary function as a wrench for the nut. When the stud gun is withdrawn, the resiliency of the ceramic fiber strips will cause the strips to return to their original position thus concealing and protecting the studs from the severe heat in the furnace.

Returning now to further consideration of FIGS. 4 and 5, it should be noted that the end strips 34 of the insulating member 20' are preferably provided with a plurality of one inch deep cuts 56 spaced approximately one inch apart from each other so as to relieve possible shrinkage stresses on parts 34 only.

As shown in FIG. 11, it may be desirable to arrange the blocks 20' of FIGS. 4 through 6 in such a manner that the strips of adjacent members are at right angles to each other to give a resulting criss-cross appearance similar to that of parquet flooring. As indicated heretofore, the arrangement of the fibers is such that they are oriented essentially in planes which are perpendicular to the furnace wall. This tends to eliminate or minimize the occurance of cracks which result from heat shrinkage of ceramic fibers. The arrangement shown in FIG. 11 tends to minimize or offset lineal shrinkage of the strips themselves.

The method and apparaus for insulating a furnace wall must be adaptable to walls which do not correspond, dimensionally, to the usage of nominal twelve inch by twelve inch insulating members. Also, it is recognized that the method and apparatus for insulating a furnace should be adaptable to furnaces which have irregularly shaped burner blocks and flue openings. As shown in FIG. 12, it is possible to arrange and attach a plurality of insulating members 20' to the surface 32' of a furnace not readily adaptable for the close end-to-end, side-to-side, arrangement shown in FIG. 11. In the case of FIG. 12, spaces 58 are provided between adjacent insulating members 20' in longitudinal or transverse or both, directions, depending upon the dimensional limitations of the furnace. The resulting spaces 58 can now be filled with specially folded ceramic fiber blankets such as shown in FIGS. 13, 14 and 15. The three fillers shown in the latter three figures are constructed in substantially the same way as the strips 22; that is, they are cut from a one inch thickness of four pound density ceramic fiber blanket and folded over.

In FIG. 15, there would be a single sheet 60 which is folded once so that its upper edges 62 provide the same type of end or edge fiber exposure referred to herein. If the resulting space is larger than two inches wide, then it is possible to go to the configuration shown in FIG. 13 which is comprised of two strips 64 and 66, which are cut in the same manner described above. The central strip 66 is relatively narrow in a vertical direction and the outer strip 64 is sufficiently wide that it can be folded around the central strip 66 as shown, the upper surfaces of strips 64 and 66 both providing the end or edge fiber arrangement referred to above.

Again, if the resulting space between adjacent insulating members 20 or between an insulating member 20 and a duct, etc. is greater than three inches, then it might be desirable to use the configuration shown in FIG. 14 where an additional central strip 68 is provided. This strip 68 will lie adjacent the strip 66 and an outer strip 70, slightly greater in width than the strip 64 will be folded over the central strips 66 and 68 to provide the arrangement shown.

The different embodiments shown in FIGS. 13, 14 and 15 can be held in place by ceramic cement, stainless steel wire or by the friction between the fibers alone.

FURTHER EMBODIMENTS AND MODIFICATIONS

Whereas the method of assembling the mat as described in relation to FIGS. 1 to 3 has been set forth in terms of wires 24, fasteners 30, etc. it should be understood that other methods could be employed to hold the strips together and to attach them to the backing insulation block. For example, the ceramic fiber strips could be attached to each other by means of suitable ceramic cements or mortar materials which are preferably utilized in the area adjacent the cold face of the fiber mat. Also, although the mats have been shown as being connected to a backing insulation block prior to application to a furnace wall, the mats could be applied directly to the furnace wall.

As far as the manner of fastening is concerned, the foregoing disclosure indicates that the mat of FIG. 1 or the composite block of FIG. 4 can be attached to a furnace wall by means of mortar, ceramic cement or various metallic fasteners. Since the ceramic cement or mortar will generally be located adjacent the cold face of the insulating member, there should be no particular high temperature problem as far as the cement or mortar is concerned; however, where metallic fasteners are concerned, it is generally recognized that alloy pins, bolts, washers and screws which could be used as fasteners have a maximum temperature limit in the range of 2000° 2100° F. "burying" or imbedding the fastener in the insulating member at a position spaced from the hot face thereof, as disclosed in the present invention, it is possible to use alloy pins, bolts, etc. without, at the same time, exposing these metallic fasteners to such high temperatures as would interfere with their effectiveness.

Although it is indicated that the mat of FIG. 1 could be applied directly to a furnace wall by means of ceramic cement or mortar, it is possible to precondition the cold face of the mat to permit the use of the stud welding method of attachment disclosed herein. For example, if a layer of cement or mortar is imbedded in the mat along the cold face thereof and allowed to harden, it is obvious that the welding technique and fasteners described in connection with FIGS. 7 to 10 could be employed, although a shorter shank 38 obviously would be necessary. The making of such a cement or mortar layer at the cold face of the mat could also be done in connection with the use of a high temperaure cloth or stainless steel wire mesh which would be applied to or imbedded in the mortar layer at the cold face of the mat to improve the fastening capabilities thereof.

Referring now to FIGS. 4 through 7, a suitable insulating block 20' designed for operation at 1800° F. is one where the backing block or mineral block 28 is about two inches in thickness and the strips 22' are approximately 1 inch in width giving a total width of the block, from the cold face to the hot face thereof, of about 3 inches. A suitable insulating block 20' designed for operation at 2600° F. is one where the mineral block 28 is also two inches in thickness but where the strips 22' are four inches in thickness giving an overall dimension of six inches from the cold face to the hot face. By using strips 22 varying in width from 1 inch to 5 inches or more, depending upon the requirements of the particular furnace, it should be apparent that insulating blocks and/or mats could be employed to cover the recommended range of 1600° F. to 2800° F.

Although the block 28 has been referred to as a mineral block whose composition and properties are well recognized in the art, it is also possible to use asbestos block or calcium silicate block, those blocks being relatively rigid, especially as compared to the fiber mat or strips, so as to provide relatively rigid backing material for the mat. The strips 22 or 22' of the ceramic fiber mat 20 or 20', respectively, are preferably cut from a ceramic fiber blanket having a density of 4 pounds per cubic foot. It is understood that the manufacturers provide ceramic fiber blankets which are available in densities ranging generally from 3 to 14 pounds per cubic foot. In the specific examples referred to herein, the ceramic fiber material has a density of four pounds per cubic foot. However, it should be understood that there might be portions of the furnace where the lining would be subject to gas currents which would give rise to erosion problems and, also, that the furnace might have various access openings which would require a lining of greater physical strength or density upon or surrounding the openings; in either of the latter two cases it might be desirable to use a ceramic fiber material of a higher density in the available range referred to above.

Naturally, it is desirable to insulate a furnace wall in such a manner that the outside (cold face) of the furnace is at a minimum temperature. However, it is recognized that this minimum temperature will be dependent upon a number of different factors including, but not limited to, the type, thickness and strength of the outside furnace wall; and prevailing air currents outside of the furnace wall. The use of the present invention will provide an outside temperature varying between 200° F. and 350° F. which is considered to be an acceptable range.

The preferred embodiment of the present invention, as disclosed above, describes the high-temperature insulating fibers which constitute the mat as "ceramic" fibers. However, this invention sould not be tied down to any precise definition of "ceramic"; any high temperature insulating fiber which possesses properties similar to the ceramic fibers indicated herein and capable of operating above 1600° F. could be used in conjunction with the present invention and should be considered as falling within the scope thereof.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein may be made within the spirit and scope of this invention.

Claims

1. A method of protecting the inside wall of a furnace, comprising:

constructing a plurality of insulating blocks, with each of said blocks having a flat first side defining a cold face and a second side remote from said first side and defining a hot face, said cold face being adapted for attachment to the inside wall of a furnace and said blocks being comprised of side-by-side srips strips of material composed of resilient insulating fibers, the fibers fibers having no particular orientation but forming randomly oriented within a plurality of planes substantially parallel to each other and generally perpendicular to said flat first side of said blocks, said cold face of each of said blocks including a supporting member accessible from said hot face by a displacement of said resilient fibers at said hot face; and

attaching each of said blocks to said furnace wall by displacing said resilient fibers at said hot face and embedding a concealable attaching member in each of said blocks at a position spaced from said hot face, said resilient fibers covering said attaching member upon attaching of said block to said furnace wall.

2. The method claimed in claim 1, wherein said attaching is carried out by passing a metal attaching member between said strips and through said flat side of each of said blocks and connecting one end of said attaching member to said wall.

3. The method claimed in claim 2, wherein said attaching members are attached to said wall by an internal welding operation welding.

4. A method of providing internal insulation for a furnace wall comprising the steps of:

providing a plurality of strips of insulating material, each strip being formed from a plurality of generally parallel planes of randomly oriented fibers;

positioning the strips to orient the parallel planes substantially perpendicular to the furnace wall; and attaching the strips to the furnace wall.

5. The method of internal insulation as recited in claim 4 wherein the insulating fibers are ceramic fibers.

6. A method of providng internal insulation as recited in claim 4, wherein the strips are attached to the furnace wall by means of metallic fasteners inserted transversely through said strips, said metallic fasteners being affixed to the furnace wall.

7. The method of insulating as described in claim 6, wherein the metallic fastener is attached to the furnace wall by an

internal welding operation. 8. A method of insulating the interior of a furnace wall, comprising:

constructing a plurality of flat insulating blocks, each of said blocks having a flat first side and defining a cold face and a second side remote from said first side and defining a hot face, said blocks being comprised of side-by-side strips of ceramic fibers having a generally random orientation, the fibers forming within a plurality of planes substantially parallel to each other and generally perpendicular to said flat side cold face of said blocks, an further including means for holding said strips adjacent each other, and further including a fastener embedded in said block at a position spaced from said hot face and concealed therefrom by said ceramic fibers, and attaching each of said blocks to the furnace wall with the flat side cold face adjacent the wall, said attaching being carried out by connecting the internal fastener to the furnace wall displacing said fibers to expose said fastener, inserting a tool through said hot face of each of said blocks to engage said fastener, fastening said fastener, and withdrawing the tool, said fibers being reoriented in response to withdrawal of said tool to conceal said fastener.

9. The method of claim 8 wherein said strips of fibers are folded so that their outer edges comprise planes of fibers substantially parallel to each other and generally perpendicular to the

furnace wall. 10. A method of insulating an interior furnace wall comprising:

constructing a plurality of insulating blocks, each of said blocks having a first side defining a cold face and a second side remote from but generally parallel to said first side and defining a hot face, said cold face being adapted for attachment to the inside wall of a furnace and said blocks being comprised of at least one strip of resilient insulating fibers, the fibers being generally randomly oriented within a plurality of planes substantially parallel to each other and generally perpendicular to said hot face of said blocks, said cold face of each of said blocks including a supporting member accesible from said hot face by a displacement of said resilient fibers at said hot face;

positioning each of said blocks at a desired location with said cold face adjacent the furnace wall;

attaching the supporting member of each of said blocks to the furnace wall by resiliently displacing the resilient fibers, inserting a tool through said hot face, and securing said supporting member to said furnace wall by

operating said tool. 11. The method of claim 10 wherein said block is comprised of a plurality of side-by-side strips. 12. The method of claim 11 wherein said tool is inserted into a seam

between adjacent strips. 13. The method of claim 10 and further comprising the step of embedding a fastener in each of said blocks to completely cover the fastener with resilient insulating fibers. 14. The method of claim 13 wherein said fastener is welded to the furnace wall by said tool. 15. The method of claim 13 wherein said fastener is screwed to the furnace wall by said tool.

16. A method for protecting the inside walls and roof of a furnace during operation at high temperatures, the furnace being operable above 1600° F., comprising the steps of:

constructing a plurality of insulating blocks adapted for attachment to the walls and roof of a high temperature furnace without requiring preattachment of supporting hardware, each of the blocks having a first side defining a cold face and a second side remote from the cold face and defining a hot face, the cold face being adapted for attachment to the inside wall or roof of a furnace without the provision of supporting hardware on the furnace prior to engagement of the insulating block onto the inside wall or roof, the blocks comprised of side-by-side strips of material composed of resilient insulating fibers, the fibers randomly oriented within a plurality of planes substantially parallel to each other and generally perpendicular to the first side of the blocks to control devitrification and shrinkage of the resilient insulating fibers at high temperatures, the cold face of each of the blocks including a supporting member accessible from the hot face by a displacement of the resilient insulating fibers at the hot face; and,

attaching each of the blocks to the inside wall or roof of the furnace by displacing the resilient insulating fibers at the hot face and embedding a concealable attaching member in each of the blocks at a position spaced from the hot face, the resilient insulating fibers covering the attaching member upon attaching of the block to the inside wall or roof of the furnace, the block having no metal retainers exposed on the hot face. 17. The method of claim 16, wherein the attaching step is carried out by the steps of:

passing a metal attaching member between the resilient insulating fibers; and, welding the metal attaching member to the inside wall or roof of the furnace. 18. The method of claim 17, wherein the constructing step further comprises the step of adhesively attaching the side-by-side strips to the supporting member. 19. A method for protecting the inside walls and roof of a furnace, the furnace being operable at temperatures between 2000° F. and 2800° F., comprising the steps of:

constructing a plurality of insulating blocks adapted for attachment to the walls and roof of a high temperature furnace without requiring preattachment of supporting hardware, each of the blocks having a first side defining a cold face and a second side remote from the cold face and defining a hot face, the cold face being adapted for attachment to the inside wall or roof of a furnace without the provision of supporting hardware on the furnace prior to engagement of the insulating block onto the inside wall or roof, the blocks comprised of side-by-side strips of material composed of resilient insulating fibers, the fibers randomly oriented within a plurality of planes substantially parallel to each other and generally perpendicular to the first side of the blocks to control devitrification and shrinkage of the resilient insulating fibers at high temperatures, the cold face of each of the blocks including a supporting member accessible from the hot face by a displacement of the resilient insulating fibers at the hot face; and,

attaching each of the blocks to the inside wall or roof of the furnace by displacing the resilient insulating fibers at the hot face and embedding a concealable attaching member in each of the blocks at a position spaced from the hot face, the resilient insulating fibers covering the attaching member upon attaching of the block to the inside wall or roof of the furnace. 20. The method of claim 19, wherein the attaching step is carried out by the steps of:

passing a metal attaching member between the resilient insulating fibers; and,

welding the metal attaching member to the inside wall or roof of the furnace. 21. The method of claim 20, wherein the constructing step further comprises the step of adhesively attaching the side-by-side strips to the supporting member. 22. The method of claim 1, wherein said constructing step further comprises the step of adhesively attaching said side-by-side strips to said supporting member. 23. A method of insulating the interior of a furnace, the furnace being operable above 1600° F., comprising the steps of:

constructing a plurality of insulating blocks, each of the blocks having a first side defining a cold face and a second side remote from the first side and defining a hot face, the blocks being comprised of side-by-side strips of ceramic fibers having a generally random orientation within a plurality of planes substantially parallel to each other and generally perpendicular to the cold face of the blocks to control the effects of devitrification and shrinkage of the ceramic fibers at high temperatures, further including means for holding the strips adjacent each other without metal retainers exposed to the hot face;

embedding a fastener in the block which is operable to fasten the block to the interior of the furnace without requiring preattachment of supporting hardware;

positioning each of the blocks at an interior surface of the furnace with the cold face adjacent the surface;

displacing the ceramic fibers to expose the fasteners;

inserting a welding tool through the hot face of each of the blocks to engage the fastener;

welding the fastener to the interior surface of the furnace to attach the block to the surface;

withdrawing the welding tool; and,

reorienting the ceramic fibers to conceal the fastener and avoid any

exposed metal. 24. The method of claim 23, wherein the constructing step further comprises the step of adhesively bonding the strips of fibers to a supporting member to hold the strips adjacent each other. 25. A method of insulating an interior furnace wall, comprising the steps of:

constructing a plurality of insulating blocks, each of said blocks having a first side defining a cold face and a second side remote from but generally parallel to said first side and defining a hot face, said cold face being adapted for attachment to the inside wall of a furnace without support hardware being preattached to the inside wall, and said blocks being comprised of at least one strip of resilient insulating fibers, the fibers being generally randomly oriented within a plurality of planes substantially parallel to each other and generally perpendicular to said hot face of said blocks to control the effects of devitrification and shrinkage, said cold face of each of said blocks including a supporting member accessible from said hot face by a displacement of said resilient fibers at said hot face, said strip of resilient insulating fibers being adhesively bonded to said supporting member;

positioning each of said blocks at a desired location with said cold face adjacent the furnace wall; and,

attaching the supporting member of each of said blocks to the furnace wall by resiliently displacing the resilient fibers, inserting a tool through said hot face, and securing said supporting member to said furnace wall by

operating said tool. 26. The method of claim 25 wherein said block is comprised of a plurality of side-by-side strips adhesively bonded to said supporting member. 27. The method of claim 26 wherein said tool is inserted into a seam between adjacent strips. 28. The method of claim 25 and further comprising the step of embedding a fastener in each of said blocks to completely cover the fastener with resilient insulating fibers. 29. The method of claim 28 wherein said fastener is welded to the furnace wall by said tool. 30. The method of claim 28 wherein said fastener is

screwed to the furnace wall by said tool. 31. A method of insulating an interior furnace wall at temperatures between 2000° F. and 2800° F., comprising the steps of:

constructing a plurality of insulating blocks, each of said blocks having a first side defining a cold face and a second side remote from but generally parallel to said first side and defining a hot face, said cold face being adapted for attachment to the inside wall of a furnace without support hardware being preattached to the inside wall, and said blocks being comprised of at least one strip of resilient insulating fibers, the fibers being generally randomly oriented within a plurality of planes substantially parallel to each other and generally perpendicular to said hot face of said blocks to control the effects of devitrification and shrinkage, said cold face of each of said blocks including a supporting member accessible from said hot face by a displacement of said resilient fibers at said hot face, said strip of resilient insulating fibers being adhesively bonded to said supporting member;

positioning each of said blocks at a desired location with said cold face adjacent the furnace wall; and,

attaching the supporting member of each of said blocks to the furnace wall by resiliently displacing the resilient fibers, inserting a tool through said hot face, and securing said supporting member to said furnace wall by

operating said tool. 32. The method of claim 31 wherein said block is comprised of a plurality of side-by-side strips adhesively bonded to said supporting member. 33. The method of claim 32 wherein said tool is inserted into a seam between adjacent strips. 34. The method of claim 31 and further comprising the step of embedding a fastener in each of said blocks to completely cover the fastener with resilient insulating fibers. 35. The method of claim 34 wherein said fastener is welded to the furnace wall by said tool. 36. The method of claim 34 wherein said fastener is screwed to the furnace wall by said tool.