GB1600468A - Insulation module - Google Patents

Description

(54) INSULATION MODULE (71) We, SAUDER INDUSTRIES, INC., a Corporation organised and existing under the laws of the State of Kansas, United States of America, of P.O. Box 1158, 220 Weaver Street, Emporia, Kansas, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to lining the interior of a furnace or like high temperature chamber or duct (all, for convenience, called "furnaces" herein).

It is known to line a furnace by fastening a high temperature fibrous insulating material, such as a ceramic fibre insulation module, to the interior wall of a furnace capable of developing temperatures in excess of 2300"F.

Fastening has been effected by such means as impaling insulation modules on fasteners in the form of bolts or studs affixed, for example by welding, to a metal interior wall and securing the insulation modules in position.

More recently, a fastening system has been developed that enables an insulation module to be selectively positioned on a metal wall and then affixed thereto by welding a stud to the wall. Such a system is disclosed in, for example, United States Patent 3,819,468 and British Patent Specification No. 1,396,724. Such prior art systems are found to be satisfactory or highly desirable in some furnace installations.

However, in circumstances where the interior geometry of a high temperature furnace is complex or where the furnace in operation is exposed to highly corrosive gases, it has been found that known systems and apparatus have performed less than ideally. For example, in highly corrosive atmospheres, it is common for metallic fastening hardware and/or metal interior walls to suffer corrosion. Although the ceramic fibres of insulation modules remain substantially unaffected by exposure to such a chemically hostile environment, the fastening hardware may deteriorate to such an extent that the structural integrity of the insulating material and the furnace wall is threatened.

Particular problems have been noted with such systems in instances where sulphur-containing gases generated in a furnace chamber have penetrated the insulating material, and thus reached the cooler regions of the furnace.

In these cooler regions, usually along the outer surface (cold face) of the insulating material, these sulphur-containing gases may condense along with some water vapour, producing sulphuric acid of relatively high concentration on the metal wall and around the fastening hardware. The effects of sulphuric acid on metal are well-known, and it is a relatively short time before insulation fastening hardware and/or metal walls will experience great damage.

In instances where furnaces have unusual geometries, e.g. asymmetric configurations with many curved surfaces, or in instances where obstructions e.g. pipes or tubing, impede the attachment of insulating material to the wall, known techniques have proven to be awkward and, in some cases, may require a substantial expenditure of time and labour in excess of that which is economically feasible.

It is also known to veneer the interior of a brick or ceramic furnace by attaching fibrous insulating materials to the interior walls thereof.

For example, a refractory motar, cement, or other adhesive material, may be used to effect a ceramic-to-ceramic bond between, say, fire brick of a furnace chamber and a ceramic fibre insulating material.

Many such refractory materials are airsetting, and become brittle and assume glasslike properties on setting. It will, of course, be apreciated that such materials tend to crack if there is relative movement between the adherent surfaces, for example caused by one or both of the surfaces experiencing significant thermal growth or shrinkage on temperature changes of the furnace. Moreover, such materials may be porous and enable corrosive vapours to penetrate any cracks formed on relative movement between the wall and linking.

Such penetration may result in the formation of highly corrosive acids and the like along the interior wall of the furnace.

Recognising the need for an improved system for applying insulating material to the interior of a furnace, it was found desirable to pro vide an improved method for attaching insulating material directly to the wall of a furnace while also inhibiting the undesirable effects of a corrosive atmosphere on the wall.

This may conveniently be achieved by means of a bonding material that forms an elastic, yieldable bond between the insulating material and the furnace wall. Because the bond is elastic and yieldable it can stretch to accommodate a degree of relative movement between the furnace wall and the insulating material caused by thermal growth and shrinkage on temperature changes between ambient and the highest temperature to be encountered by the bond, typically 200-3000F. The bonding material should preferably be a corrosion inhibitor/adhesive material, most preferably a silicone compond such as the room temperature vulcanizing silicone compound known by the Trade Mark SILASTIC, type "732 RTV" available from Dow Coming Corporation of Midland Michigan, USA.

The present invention is directed towards a form of insulation module utilising a yieldable adhesive and incorporating a substrate and which may also provide an impervious corrosion resistant barrier between the insulating material and the wall to which the module is attached so as to be especially suitable for lining furnaces within which corrosive atmospheres occur.

Thus in one aspect the present invention provides an insulation module for attachments to a wall which is subject to thermal size variation, the module comprising insulating material and a substrate comprising a layer of adhesive covering at least a portion of a face of the insulation material which is to be attached to the wall, the adhesive being a material which remains yieldable and elastic over the temperature range to which the wall is subject, and a fabric which is attached to at least a portion of the adhesive.

In a preferred embodiment the substrate comprises a first layer of adhesive, a second layer of fabric and a third adhesive layer.

Preferably the adhesive is a corrosion inhibitor, silicone compounds such as the SILASTIC type 732 RTV are especially preferred: the same material may be used to effect bonding of the module to the wall, e.g.

of a furnace, with optimum compatibility of the substrate and the bonding material and the formation of an elastic and yielding bond.

To form an impervious corrosion resistant barrier the corrosion resistant adhesive may be applied as a continuous layer on the face of the module and/or on the wall to which the module or a plurality of modules are attached.

The fabric is desirably formed of glass fibre material and is preferably of openwork (mesh) construction, being so applied that the adhesive permeates into the interstices of the fabric and forms an integrated reinforced structure.

The insulating material is preferably ceramic fibre and most desirably is comprised of a series of side-by-side strips cut from a blanket or web of ceramic fibre so that the majority of the fibres in the module lie in planes that are generally parallel with one another and substantially perpendicular to those faces of the module which, in use, are the hot and cold faces of the module.

The invention also embraces a furnace lined with insulation modules.

The invention will be further explained with reference to the accompanying drawings, in which: FIGURE 1 is a diagrammatic sectional view depicting two adjacent insulation modules affixed to a furnace internal wall surface; FIGURE 2 is a cross-sectional view of one of the modules of Figure 1; and FIGURE 3 is a perspective view on the cold face of the module of Figure 3, partly broken away to reveal the construction of the attachment substrate.

Figure 1 depicts a pair of modules 60 and 60' as they might lie in relationship to one another in a furnace constructed in accordance with the present invention. Modules 60 and 60' are approximately the same size and each is comprised of a series of side-by-side insulating strips 26. The strips 26 are held in position with respect to one another by an attachment substrate 64. The substrate 64 defines the cold face of the modules 60 and 60' as will hereinafter be more fully explained.

Each insulating strip 26 is comprised of insulating fibres, preferably of the ceramic type. The fibres have no particular orientation but generally lie in a plurality of planes that are substantially parallel to each other and generally perpendicular to the cold face or flat side 18 of each module.

It is preferable to construct the furnace of the present invention with adjacent modules rotated 90" with respect to the orientation of the strips 26. For example, in Figure 1 it can be seen that the module 60 has strips which run in a direction generally 90" with respect to the strips 26 of module 60'.

The substrate 64 consists of three layers: an inside layer 66 is comprised of a corrosion inhibitor/adhesive that is preferably the silicone compound known by the Trade Mark SILASTIC type "732 RTV3' and that is applied to a plane or cold face 67 defined by edges of strips 26 diluted with a suitable solvent and in sufficient quantity to penetrate slightly into the ceramic fibrous material of strips 26, so as to form an impervious barrier layer on the cold face 67.

Overlying the first layer 66 is a second layer 68 that serves as a reinforcement and is preferably a cloth-like fabric of glass fibres. It is preferably of open mesh construction but may have a wide variety of geometries or mesh sizes. As may be seen in Figure 3, the reinforcement layer 6S preferably extends to the edges of the cold face 67.

An outside or third layer 70 of corrosion inhibitor/adhesive is applied over the reinforcement layer 68. This outside layer 70 may not be as thick as the first layer 66 and may take the appearance of a "skin" over the layer 68 with the contour of the mesh of that layer being visible.

The substrate 64 provides a highly reliable attachment arrangement which maintains the strips 26 in side-by-side relationship during handling of the module 60 as well as after a furnace is constructed in accordance with the present invention. A relatively small amount of a suitable bonding material, such as the corrosion inhibitor/adhesive of the layers 66, 70, is required to satisfactorily affix the module 60 to a furnace wall 12. Two strips 22 of corrosion inhibitor/adhesive may be required per module in the construction of a furnace according to this invention. It will be appreciated, of course, that the internal surface 16 of the furnace wall 12 may be completely covered with another layer of corrosion inhibitor/adhesive and the module 60 applied thereto to achieve complete isolation of the wall 12 from the atmosphere within the furnace.Moreover, whereas fibre fabric is preferred for the reinforcement layer 68, other fabrics which demonstrate the appropriate temperature resistance, corrosion resistance, and handling characteristics may be appropriate.

If reinforcement material of an open mesh construction is utilized, it may be found that the reinforcement does not form a discrete layer in substrate 64. Rather, the reinforcement 68 may "sink" into the first layer 66 of corrosion inhibitor/adhesive and comprise a portion of this first layer. In such a case, the corrosion inhibitor/adhesive will flow into the interspaces 72 of the mesh to form a substrate having highly desirable structural characteristics.

The preferred insulating material for the insulation modules of the invention is ceramic fibre, preferably in the form of strips cut from a blanket or web in the manner described.

However, the invention contemplates modules of other insulating materials and constructions, for instance vacuum-formed modules of a required shape, and modules formed from a single, albeit large, strip of ceramic fibre.

WHAT WE CLAIM IS:- 1. An insulation module for attachment to a wall which is subject to thermal size variation, the module comprising insulating material and a substrate comprising a layer of adhesive covering at least a portion of a face of the insulation material which is to be attached to the wall, the adhesive being a material which remains yieldable and elastic over the temperature range to which the wall is subject, and a fabric which is attached to at least a portion of the adhesive.

2. An insulation module according to claim 1 in which the substrate comprises a first layer of adhesive, a second layer of fabric and a third adhesive layer.

3. An insulation module according to claim 1 or claim 2 in which the adhesive covers the entire said face of the insulation material.

4. An insulation module according to any one of the preceding claims in which the fabric comprises a foraminous material.

5. An insulation module according to any one of the preceding claims in which the fabric is woven.

6. An insulation module according to any one of the preceding claims in which the fabric comprises glass fibre material.

7. An insulation module according to any one of the preceding claims in which the adhesive is also a corrosion inhibitor.

8. An insulation module according to claim 7, wherein corrosion inhibitor/adhesive material is a silicone compound.

9. An insulation module according to claim 8, wherein said silicone compound is that known by the Trade Mark SILASTIC, type "732 RTV".

10. An insulation module according to any one of the preceding claims in which the fabric is of openwork construction and so applied that the adhesive permeates into the interstices of the fabric.

11. An insulation module according to any one of the preceding claims wherein the insulating material is ceramic fibre.

12. An insulation module according to claim 11, wherein the insulating material comprises a series of side-by-side strips cut from a ceramic fibre blanket or web, whereby the majority of fibres in the module lie in planes that are generally parallel with one another and substantially perpendicular to the substrate.

13. An insulation module substantially as described with reference to and as shown in the accompanying drawings.

14. A furnace lined internally with insulation modules in accordance with any preceding

Claims (1)

1. claim.

   15. A furnace according to claim 14, wherein the modules are fixed to the internal surfaces of the furnace walls by means of a corrosion inhibitor/adhesive bonding material.

   16. A furnace according to claim 15, wherein said bonding material is applied as a continuous layer on said wall surfaces.

   17. A furnace according to claim 16, wherein said bonding material is the same material as the adhesive substrate of the modules.