GB2118283A - Refractory sheathing - Google Patents

Abstract

A refractory tile outer layer (100) of a refractory sheathing for horizontal metal members (11) in furnaces and consisting of a substantially U-shaped block (20) with the centre portion (21) to embrace a furnace member of appropriate size and each arm portion (22, 23) shaped to engage and interlock with a channel-section refractory block (60) the hollow channel (61) of which also embraces a circumferential part of the furnace member so that an outer sheathing layer composite of one U-shaped block and two channel-section blocks embrace at least a majority of the circumference of the furnace member to be retained thereon; the sheathing is completed by an inner layer (103) of a refractory fibrous material. <IMAGE>

Description

SPECIFICATION Refractory sheathing This invention relates to refractory sheathing for horizontal metal members in furnaces, such as re-heat furnace skid rails and their supporting structure, particularly cross-over pipes.

The invention is particularly concerned with refractory tiles for cladding thermal insulation on skid rails and the cross-over pipes which support the rails in reheat furnaces for ferrous slabs and will be described as applied thereto but application of the invention to other members in furnaces where similar conditions exist is not precluded.

In a re-heat furnace, slabs must be heated to a very high temperature, for example 1 260 C, as uniformly as possible and the slabs are therefore moved along raised skid rails, usually water-cooled hollow rails supported by a gantry-like structure of watercooled hollow members, while they are heated from above and below by intensely hot gas blast from burners.

The supporting structure is directly in the path of the hot gas and, as well as being water-cooled, the hollow rails and supports are sheathed with refractory material. The present invention, in its preferred application, improves sheathing of the kind consisting of an inner layer of refractory fibrous material and an outer layer of refractory tiles.For such a layer, the present invention provides a refractory tile of the kind consisting of a sub stantiglly U-shaped block with the centre portion to embrace a furnace member of appropriate size and each arm portion being shaped to engage and interlock with a channel-section refractory block the hollow channel of which also embraces a circumferential part of the furnace member so that the outer sheathing composite of one U-shaped block and the two channel-section blocks embrace at least a majority of the circumference of the furnace member to be retained thereon.

In a preferred embodiment, each U-block arm has a hook-shaped cut-out and each channel-block has a complementary hookshaped cut-out in a side edge thereof so that the blocks are locked one to the other against movement in the plane of the arms; the hook cut-outs are also wedge-shaped radially of the U-block arm portion so that the U-block and channel-blocks are radially locked one to the other; the only direction for free relative movement of the U-block and channel-blocks being axially of the U-block.

In a preferred embodiment of this invention, the U-block arms and each channel-block is provided with a co-axial bore so that a locking-pin can be inserted axially through each U-block and channel-block pair.

The above and other features of the invention are illustrated, by way of example, in the drawings, wherein: Figure 1 is a schematic drawing of the interior of a slab reheating furnace; Figure 2 is a perspective view of a U-block in accordance with the invention; Figure 3 is an end elevation of the block of Fig 2; Figure 4 is a section on the line IV-IV of Fig. 3; Figure 5 is a plan of the block of Fig. 3; Figure 6 is a perspective view of a pair of channel-blocks in accordance with the invention; Figure 7 is a side elevation of the righthand block of Fig. 6; Figure 8 is an end elevation of the block of Fig. 7; Figure 9 is a plan of the block of Fig. 7; Figure 10 is a cross-section of an outer sheathing composite in position about a skid rail; and Figure 11 is a perspective view of a pair of U-blocks in position about a vertical pipe support.

Fig. 1 illustrates, schematically, part of a slab reheating furnace 10 including skid rails 11 along which slabs 1 2 are moved in the direction indicated by arrow 1 3. The slabs are introduced at an inlet, not shown, and discharged through an outlet 1 4.

The skid rails are supported on horizontal water-cooled pipe supports 1 5 which are in turn supported by vertical water-cooled pipe supports 1 6 on refractory brick pedestals 1 7.

The positions of an upper burner and a lower burner are indicated respectively at 1 8 and 1 9 and it can be seen that the skid rail support members stand in the path of the hot gases from the lower burner 1 9.

Figs. 2 to 5 illustrate a reheating sheathing tile in the form of a substantially U-shaped block 20 of a refractory material, such as 70-80% mullite blended with a plastic refractory clay 20 to 30% to mention only one example; mullite is a known refractory made by firing calcined kyanite, a naturally occurring alumina silicate, at about 1450"C. The centre portion 21 of the U-block is of a size to embrace a furnace member, whilst leaving room for an inner layer of refractory fibrous material such as a ceramic fibre of the type known as Triton manufactured and sold by Companies of The Morgan Crucible Group of England; or of the type known as Kaowool, manufactured by the Babcock and Wilcox Company of The United States of America.

The properties of the ceramic fibre material are explained in detail in the United States patent to Harter et al, Patent No. 2 636 723.

Each arm 22 and 23 of the U-block has an oppositely axially-directed, centrally-positioned, hook-shaped cut-out 24 and 25 respectively. The hook-shaped cut-outs are also wedged-shaped radially of the central axis 26-26 of the U-block. Each cut-out 24, 25 has an upper part 27 coaxially extended to overlie a lower part 28 and forms the hook (Fig. 4). Each arm also has an axial bore 29 running from an end face of the block to the lower part of each hook.

Figs. 6 to 9 illustrate a refractory sheathing tile in the form of a channel-shaped block 60 of refractory material, the hollow channel 61 of the channel-block being of a size to embrace a circumferential part of a furnace member, whilst again leaving room for a layer of refractory fibrous material (see Figs. 10 and 11). One side edge 62 of the channel-block has a centrally positioned, hook-shaped cutout 63, complementary to the cut-out 24 and 25 of the U-block 20. The hook-shaped cutout 63 is also radially wedge-shaped and has a lower part 64 axially extended to overlie an upper part 65 and form the hook. An axial bore 66 also extends from an end face of the block to the lower part of the hook.

Fig. 10 illustrates an outer sheathing composite in accordance with the invention in position about a skid rail pipe 11, in which a water-cooled metal tube 101 has an integral rail rib 102 (or series of lugs or projections, not shown) and is sheathed by an inner layer 103 of refractory fibrous material held in position by an outer sheathing comprising a U-block 20 and a pair of channel-blocks 60.

The channel-blocks are identical and, by reversing their axial direction, one channel-block is hooked to interlock with one of the arm hooks of the U-block. The hooks prevent relative upward movement of the channelblocks, in the plane of the U-block arms, and the wedge shaping of the hook cut-outs prevents excessive relative radial movement of the blocks. The blocks are only free to move coaxially of the U-block and, once the composite sheath has been assembled about a furnace member, axial movement of any one composite is prevented by neighbouring composites.

A steel pin (not shown) or other refractory metal pin is inserted into the co-axial bores 29 and 66 to improve the interlock between the blocks, a separate pin might be used for each composite (with the bore holes plugged with refractory fibre) or a longer pin could be employed to join composites together. The gap between the rib 102 and each channelblock 60 is sealed with refractory mortar 1 04.

Fig. 11 illustrates an alternative use of the U-blocks 20. In this application each block extends over a 180"C arc and, owing to the oppositely-directed hooks 24, 25, a pair of blocks can be interlocked about a furnace member, such as the horizontal pipe supports 1 5 or the vertical pipe supports 16, both of which have to be completely sheathed by an inner refractory fibre layer 110 and an outer refractory tile sheath 111 (as shown by Fig.

11). Again metal pins (not shown) are inserted in the co-axial bores 29 and the bores plugged with fibre.

The pins are used to improve the interlock between blocks in the harsh environment of a reheat furnace, whilst being designed to permit limited relative movement of the blocks, either in stress relief or angularly, and this enables the sheath to accommodate mechanical shock or vibration or thermal shock which might damage a rigid refractory sheath. Mechanical shock and vibration can be caused by the movement of heavy slabs on skid rails and thermal shock can occur on starting up of a furnace and in cooling by the practice of hosing cold water into the furnace to cause break-up of accumulated slag.

Claims (7)

1. A refractory tile outer layer of a refractory sheathing for horizontal metal members in furnaces and consisting of a substantially U-shaped block with the centre portion to embrace a furnace member of appropriate size and each arm portion shaped to engage and interlock with a channel-section refractory block the hollow channel of which also embraces a circumferential part of the furnace member so that an outer sheathing layer composite of one U-shaped block and two channel-section blocks embrace at least a majority of the circumference of the furnace member to be retained thereon.

2. A layer as claimed in claim 1, wherein each U-block arm has a hooked-shaped cutout and each channel-block has a complementary cut-out in a side edge thereof so that the blocks are locked one to the other against movement in the plane of the arms.

3. A layer as claimed in claim 2, wherein the hook cut-outs are also wedge-shaped radially of the U-block arm portion so that the Ublock and the channel-blocks are radially locked one to the other.

4. A layer as claimed in any of the previous claims, wherein the U-block arms and each channel-block is provided with co-axial bore so that a locking pin can be inserted axially through each U-block and channelblock pair.

5. A refractory tile outer layer substantially as described with reference to or as shown by the Drawings.

6. A refractory sheathing consisting of an inner layer of refractory fibrous material and a refractory tile outer layer as claimed in any of the previous claims.

7. A refractory sheathing for a furnace member consisting of an inner layer of refractory fibrous material completely sheathed by a refractory tile outer layer formed by an interlocked pair of U-shaped blocks as claimed in any of claims 1 to 5.