GB2288524A - Mounting a heating element on a furnace lining construction - Google Patents

Abstract

A thermal insulation module (13) which is positioned with one face (14) thereof against or closely adjacent to an internal surface of the furnace wall (11) to be lined, and a second opposite face (15) being spaced away from the furnace wall, is made up of matted insulated fibres. Hanger means (18) for supporting an electrical resistance heating element (16) from the second face of the thermal insulation member, comprise a generally elongate spiral element (19) and a support part (20) at one end thereof, the element being screwed into the thermal insulation module at least part way along its longitudinal axis (A) with the support part located exteriorally of the thermal insulation module and the support part in use, providing support for the electrical resistance heating element. The module may be recessed to support the length of the element and the element may have a supporting member extending through its coils, the member being supported on hooks. <IMAGE>

Description

Title: Furnace lining construction Description of Invention This invention relates to a furnace lining construction.

Throughout this specification by "furnace" we mean a furnace, oven, or kiln in which heating is effected, not necessarily exclusively, by an electrical heating means comprising one or more electrical resistance heating elements.

Throughout this specification by "furnace wall" we mean either a side wall or ceiling of a furnace, or a floor.

Conventionally, such electrical resistance heating elements comprise ribbons or wires which are supported on hangers which are either attached to the furnace wall or to an anchor means wholly located within a thermal insulation member which lines the furnace wall.

An arrangement of the latter kind is described in British patent specification 1596288, but the construction of thermal insulating members each having an anchor means located therewithin, can be economically disadvantageous and also, because the hangers which support the heating elements have to cooperate with the anchor means, there is limited flexibility as to where the electrical resistance heating elements can be positioned.

According to one aspect of the invention we provide a furnace lining construction comprising a thermal insulation member which is positioned with one face thereof against or closely adjacent to an internal surface of a furnace wall to be lined, and a second opposite face being spaced away from the furnace wall, the thermal insulation member being made up of matted insulating fibres, there being hanger means for supporting an electrical resistance heating element from the second face of the thermal insulation member, the hanger means comprising a generally elongate spiral element and a support part at one end thereof, the element being screwed into the thermal insulation member at least part way along its longitudinal axis with the support part located exteriorally of the thermal insulation member, and the support part in use providing for the electrical resistance heating element.

Thus utilising the present invention, a furnace lining construction is provided in which the thermal insulation member is not made unduly heavy by the inclusion of an internal anchor for the hanger means, and surprisingly the hanger means is sufficiently securely held by the matted fibres of the thermal insulation member to give adequate support to the electrical resistance heating elements hung thereon.

The hanger means may be made of a heat resisting metal such as a nickel chrome alloy or an iron chrome aluminium alloy which is capable of withstanding the design temperature of the furnace, but the hanger means may be made of a ceramic material, thus to obviate any risk of the hanger means becoming ductile due to the heat of the furnace. Also, a ceramic hanger means is not prone to corrosion as may be the case with a hanger means made of metal.

The invention will now be described with reference to the accompanying drawings in which: FIGURE 1 is an illustrative fragmentary view, partly exploded, of an internal surface of a furnace wall lined with a furnace lining construction in accordance with the invention, FIGURE 2 is an enlarged illustrative view of a hanger means for use in the furnace lining construction of figure 1.

FIGURE 3 is a perspective view of a modified module for lining a furnace wall, in accordance with the invention.

Referring to figures 1 and 2 of the drawings, a furnace 10 has an outer furnace wall 11 which may be made of metal, such as mild steel or expanded metal or another material, or may be metal clad with ceramic lining material. The furnace wall 11 shown comprises a side wall of the furnace 10, but it will be appreciated that the invention may alternatively or additionally be applied to lining a furnace wall comprising a ceiling of the furnace, or even the floor thereof.

In use, the internal surface of the furnace wall 11 is a so called "cold" surface, in that it is shielded from heat generated in the furnace 10, by a furnace lining construction 12.

The furnace lining 12 comprises in this example, two thermal insulation modules 13, also known as modules, each comprising a block of matted insulating fibres, conveniently ceramic fibres, such as may be known under the trade mark KAOWOOL. The thermal insulation modules 13 are in this example each made up as a plurality of layers L1, L2, etc. of matted fibres, formed into a block, with the fibres of each layer extending generally in a direction generally vertical to the side furnace wall 11 or otherwise perpendicular, or in the same direction, as desired. For the ceiling furnace wall, the layers L1, 12, may extend parallel to the side furnace wall 11 or transverse relative thereto, as shown, as desired.

Instead of the insulating fibres being ceramic fibres, any other suitable kinds of fibres could be provided. Ceramic fibres are preferred as they provide high thermal capacity for low weight, and thus provide good insulation without being unduly heavy. In the example shown in the drawings, the thermal insulation module 13 has a density of about 200 kilograms per square metre but could have a density anywhere in the range of 128 to 240 kilograms per square metre conveniently.

Alternatively, the thermal insulation modules 13 could be made by folding a blanket of matted ceramic or other fibres in concertina fashion or the fibres may otherwise be matted into a mass.

In practice, more than two thermal insulation modules 13 would be provided side by side, each thermal insulation member being a block measuring perhaps 300mm x 300mm square, by 125 mum up to 300mm thick, although other dimensions are possible depending upon the furnace application and the degree of ease of handling required. For example, the modules may be 600mm long instead of 300mm. Thus part only or the entire furnace wall may be lined.

The thermal insulation module(s) 13, may be attached to the furnace wall 11 by any desired means. For example in GB 2111657 there are described methods of affixing fibre insulation modules to a furnace wall either by attaching studs to the furnace wall e.g. by welding, and impaling the fibre modules onto the studs, or by using adhesive. Thus a first outward face 14 of the thermal insulation module 13 may be in contact with the furnace wall 11 or spaced therefrom as required, and this may be a cold face.

Supported from a second face 15 of each of the thermal insulating modules 13 opposite to face 14 which is, in use, exposed to the heat of the furnace and is therefore a "hot" face, are a pair of electrical resistance heating elements 16 which in the example shown, comprises coils, but could each comprise a ribbon of electrically resistive material made of a suitable metal, connected exteriorally of the furnace to a suitable electrical power source. Such electrical resistance heating elements 16 have a relatively short useful life and require replacement. Thus supports for the electrical resistance heating elements 16 need to support the elements such as to enable the elements easily to be replaced.

In accordance with the invention, at least one support comprises a hanger means 18, preferably being of a unitary construction, and comprising a generally elongate spiral element 19, and at one end thereof, a support part 20.

In use, the hanger means 18 is screwed into a thermal insulation module 13, at least part way along its longitudinal axis A such that, in this example, the support part 20 is located exteriorally of the thermal insulation module 13, so that the support part 20 can in use, support the electrical resistance heating element 16.

Conveniently, the hanger means 18 is screwed into the module(s) 13 where two of the layers L1, meet.

In the example shown, the support part 20 comprises an end of the spiral element 19, bent into a hook shape, although other configurations are possible.

In one arrangement, the hanger means 18 is made of a heat resistant metal such as nickel chrome alloy or an iron chrome aluminium alloy which is capable of withstanding the temperatures which the furnace 10 is designed to attain. For example, typical furnaces used for heat treating metal, firing bricks or pottery or the like, may attain a temperature of up to 1200O C or more.

The hanger means 18 is made from rod stock metal formed into the generally elongate spiral element as shown. Alternatively, the hanger means 18 may be made from flat stock metal such that the material of the hanger means 18, at each point along the spiral, lies in a plane transverse to the longitudinal axis A of the spiral such that at each point along the spiral, the material of the spiral has a width dimension which is greater in a generally radial sense than a dimension in a direction generally parallel to the longitudinal axis A. In this way, the maximum surface area is presented to the ceramic fibres of the thermal insulation module 13, to resist withdrawal of the hanger means 18 axially from the module 13.

In each case the exact pitch to diameter ratio of the turns of the spiral hanger means 18 needs to be chosen to provide adequate resistance to pull out and ease of securing the hanger 18 into the module 13, and it is envisaged that a pitch to diameter ratio of between 1:6 and 1:10 needs to be chosen.

In the example shown, the hanger means 18 has a generally cylindrical outline 22, at least along the spiral element 19 thereof, having an overall diameter of typically 15 mum, which is similar to the external diameter of the heating coils 16. Preferably, the diameter or thickness of the material from which the hanger 18 is made, is no greater than the diameter of the material from which the heating coils 16 are made. Typically, this could be about 3mm.

In another embodiment, the hanger means 18, instead of being made from a heat resistant metal, is made from a ceramic material which may be formed or moulded to a helical configuration as shown. Ceramic material has an advantage over metal in that there is no risk of a ceramic hanger means 18 becoming ductile at high temperatures, such that a ceramic hanger means 18 may be utilised in furnaces in which higher temperatures are attained. Also, a ceramic hanger means 18 is not prone to corrosion, like metal hanger means 18.

The spiral element 19 may be right or left handed as desired, and preferably the hanger means 18 is screwed into the thermal insulation module 13 such that the spiral element extends into the module 13 to a depth until at least three turns or pitches of the spiral are embedded in the module 13.

Referring to figure 3, a module 13' is shown in an outer face 15' of which, notches 25 are cut of a part circular form in this example, in which notches in use the heating coils 16 are received. Thus the coils 16 are supported along their length by the walls of the notches 25.

The hanger means 18' are each screwed into the module 13' such that a support element thereof just extends into the notch 25 to retain the coils of the elements 16.

If desired, particularly where the module 13, or 13' is attached to a ceiling furnace wall, if desired a thin anchor rod or tube (shown at 26 in figure 3) is inserted through the coils of the heating elements 16,16' to support the heating elements 16,16' along their lengths. The anchor rod or tube 26 would be supported by the hanger means 18,18'.

The features disclosed in the foregoing description, the following claims or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (15)

1. A furnace lining construction comprising a thermal insulation member which is positioned with one face thereof against or closely adjacent to an internal surface of a furnace wall to be lined, and a second opposite face being spaced away from the furnace wall, the thermal insulation member being made up of matted insulated fibres, and there being hanger means for supporting an electrical resistance heating element from the second face of the thermal insulation member, the hanger means comprising a generally elongate spiral element and a support part at one end thereof, the element being screwed into the thermal insulation member at least part way along its longitudinal axis with the support part located exteriorally of the thermal insulation member and the support part in use, providing support for the electrical resistance heating element.

2. A construction according to claim 1 wherein the thermal insulation member comprises matted ceramic fibres.

3. A construction according to claim 1 or claim 2 wherein the thermal insulation member comprises layers of insulating fibres formed into a block, with the fibres in each layer extending generally perpendicular to the furnace wall.

4. A construction according to any one of claims 1 to 3 wherein the thermal insulation member has a density of between 128 and 240 kilograms per square metre.

5. A construction according to any one of claims 1 to 4 wherein the thermal insulation member has a thickness between the first and second faces of between about 125 mum and 300mm.

6. A construction according to any one of claims 1 to 5 wherein the hanger means is of a unitary construction.

7. A construction according to claim 6 wherein the hanger means is made of a heat resistant metal capable of withstanding the temperature which the furnace is designed to attain.

8. A construction according to claim 6 wherein the hanger means is made from formed rod.

9. A construction according to claim 7 wherein the hanger means is made from generally flat stock metal formed into the generally elongate spiral element with the material at each point along the spiral lying in a plane transverse to the longitudinal axis of the spiral.

10. A construction according to any one of claims 1 to 6 wherein the hanger is made of a ceramic material moulded or otherwise formed to a generally spiral configuration.

11. A construction according to claim 9 or claim 10 wherein at each point along the spiral, the ceramic material of the spiral has a dimension which is greater in a generally radial sense than in a direction parallel to the longitudinal axis.

12. A construction according to any one of claims 1 to 11 wherein the spiral element has a generally cylindrical outline and a pitch to diameter ratio of of between 1:6 and 1:10.

13. A construction according to any one of claims 1 to 12 in which the furnace wall to be lined is made of metal.

14. A furnace construction substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

15. Any novel feature or novel combination of features as herein defined and/or shown in the accompanying drawings.