GB1589613A - Thermal insulating element for furnace skid pipes and beams - Google Patents

Description

(54) AN IMPROVED THERMAL INSULATING ELEMENT FOR FURNACE SKID PIPES AND BEAMS (71) We, BRITISH STEEL CORPOR ATION, a Corporation incorporated and existing under the Iron and Steel Act 1967 whose principal office is at 33 Grosvenor Place, London, S.W.1, England, 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: The invention relates to thermal insulation elements, and particularly, but not exclusively, to insulation elements for cooled support beams in furnaces.

In many metallurgical process furnaces, particularly continuous reheating furnaces in the steel industry, flat metal stock is heated from both sides while passing more or less continuously through the furnace.

During this process the stock is supported on an open array of hollow beams which are cooled to maintain their mechanical strength. The array of hollow beams may be a fixed structure over which the stock is slid by a pushing mechanism outside the furnace, in which case the array is commonly called a skid system, the hollow beams on which the stock slides being called skid pipes. Alternatively, the array may consist of a fixed part and a moving part which are so arranged that the stock may be lifted from the fixed beams by the moving beams, transported a small way along the furnace and the replaced on the fixed beams. This latter is commonly called a walking beam system.

In both systems of support the degree of cooling required and the total surface area of the array of hollow beams are such that without insulation a significant part of the heat input to the furnace may be lost to the beam cooling system. Typically, 25% of the heat input may be lost from the furnace in this way. Much has been done to reduce this loss by insulating the array of hollow beams.

A common method of insulating skids is indicated in Figure 1. This type of insulation has a fairly short life, failing in several ways, e.g. by loss of grouting and subsequent failure of tack welds, leading to total loss of the segments; and by oxidation of the reinforcement and temperature gradients in the case segments, leading to disintegration and loss of refractory.

Developments in the field of refractory fibrous materials (ceramic fibres) have resulted in some proposals and applications of these materials for beam insulation. The present invention is concerned with a further method of using ceramic fibres for beam insulation.

The invention provides a thermal insulation element comprising at least two sheets of knitted ceramic fibre material connected together in face-to-face relationship and in which there are apertures in one or more sheets whereby the sheets can be hung from projections on a face so to insulate that face, two of the sheets having bulked ceramic fibres contained therebetween.

It is further preferred that the bulked caramic fibres are connected to the said two sheets.

Preferably, one or more of the sheets have apertures along two opposed edges, whereby it or they may be wrapped around the hollow beam or a pipe, and the opposed edges can be hung from one or two series of projections along the beam or pipe.

Conveniently the opposed edges of the sheet or sheets can be hung from a single series of projections.

Alternatively there are several series of projections around the periphery of the beam or pipe.

Advantageously, the sheets are connected only along one edge.

Conveniently ceramic material is spray coated onto an outwardly facing surface of one of the sheets.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which Figure 1 is a cross-section of a prior art skid pipe, and Figure 2 is a cross-section of a skid pipe according to the present invention.

As shown in Figure 1 skid pipes have previously been insulated using cast refractory insulation elements (7) formed on wire mesh reinforcement (8) which is welded to the skid pipe at 9. The gaps between the insulation elements and between the insulation elements and the skid rail weaver bar have in the past been filled with grout.

In accordance with the invention ceramic fibre is spun into thick yarn which is then knitted into a flexible sack indicated at 11 (which shows the knitted yarn in section). A small quantity of bulk ceramic fibre 12 is placed in the sack.

The completed sack in wrapped around a hollow beam or skid pipe 10 and attached by hooking stitches or specially knitted loops over small studs 14 welded to the beam.

The outer surface of the attached sack 15 may be given some further protection, e.g.

by a spray coating of same material.

Figure 2 indicates in section the suggested method of insulating a hollow beam showing specifically a skid rail on top of a skid pipe.

Although Figure 2 indicates only two rows of studs for attaching the edges of the cushion to a skid, more studs distributed over the beam can be used if desired, with the knitting popped or teased over each.

An alternative method of using knitted caramic fibre insulation is in the form of multiple layers of single knitted thickness superimposed with at least one loose fibre interlayer, with or without spray coatings for any or all layers.

A convenient method of attachment may be achieved by knitting a row of "buttonholes" near the edge to be attached and buttoning the knitting to the studs. Attachment for completely insulated beams may be achieved using a single row of studs and buttoning both edges to that single row (more studs can be used if required of course).

WHAT WE CLAIM IS: 1. A thermal insulation element comprising at least two sheets of knitted ceramic fibre material connected together in fact-toface relationship and in which there are apertures in one or more sheets whereby the sheets can be hung from projections on a face so to insulate that face, two of the sheets having bulked ceramic fibres contained therebetween.

2. An insulation element as claimed in claim 1 in which the bulked ceramic fibres are connected to the said two sheets.

3. An insulation element as claimed in Claim 1 or 2 in which said one or more sheets have apertures along two opposed edges, whereby it or they may be wrapped around a hollow beam or a pipe, and the opposed edges can be hung from one or two series of projections along the beam or pipe.

4. An insulation element as claimed in any one of the preceding claims in which the sheets are connected only along one edge.

5. An insulation element as claimed in any one of the preceding claims in which ceramic material is spray coated onto an outwardly facing surface of one of the sheets.

6. A thermal insulation element substantially as hereinbefore described with reference to and as shown in Figure 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. sheet or sheets can be hung from a single series of projections. Alternatively there are several series of projections around the periphery of the beam or pipe. Advantageously, the sheets are connected only along one edge. Conveniently ceramic material is spray coated onto an outwardly facing surface of one of the sheets. A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which Figure 1 is a cross-section of a prior art skid pipe, and Figure 2 is a cross-section of a skid pipe according to the present invention. As shown in Figure 1 skid pipes have previously been insulated using cast refractory insulation elements (7) formed on wire mesh reinforcement (8) which is welded to the skid pipe at 9. The gaps between the insulation elements and between the insulation elements and the skid rail weaver bar have in the past been filled with grout. In accordance with the invention ceramic fibre is spun into thick yarn which is then knitted into a flexible sack indicated at 11 (which shows the knitted yarn in section). A small quantity of bulk ceramic fibre 12 is placed in the sack. The completed sack in wrapped around a hollow beam or skid pipe 10 and attached by hooking stitches or specially knitted loops over small studs 14 welded to the beam. The outer surface of the attached sack 15 may be given some further protection, e.g. by a spray coating of same material. Figure 2 indicates in section the suggested method of insulating a hollow beam showing specifically a skid rail on top of a skid pipe. Although Figure 2 indicates only two rows of studs for attaching the edges of the cushion to a skid, more studs distributed over the beam can be used if desired, with the knitting popped or teased over each. An alternative method of using knitted caramic fibre insulation is in the form of multiple layers of single knitted thickness superimposed with at least one loose fibre interlayer, with or without spray coatings for any or all layers. A convenient method of attachment may be achieved by knitting a row of "buttonholes" near the edge to be attached and buttoning the knitting to the studs. Attachment for completely insulated beams may be achieved using a single row of studs and buttoning both edges to that single row (more studs can be used if required of course). WHAT WE CLAIM IS:

1. A thermal insulation element comprising at least two sheets of knitted ceramic fibre material connected together in fact-toface relationship and in which there are apertures in one or more sheets whereby the sheets can be hung from projections on a face so to insulate that face, two of the sheets having bulked ceramic fibres contained therebetween.

2. An insulation element as claimed in claim 1 in which the bulked ceramic fibres are connected to the said two sheets.

3. An insulation element as claimed in Claim 1 or 2 in which said one or more sheets have apertures along two opposed edges, whereby it or they may be wrapped around a hollow beam or a pipe, and the opposed edges can be hung from one or two series of projections along the beam or pipe.

4. An insulation element as claimed in any one of the preceding claims in which the sheets are connected only along one edge.

5. An insulation element as claimed in any one of the preceding claims in which ceramic material is spray coated onto an outwardly facing surface of one of the sheets.

6. A thermal insulation element substantially as hereinbefore described with reference to and as shown in Figure 2 of the accompanying drawings.