GB2178500A - Tiles for lining pipes - Google Patents

Abstract

An abrasion-resistant tile for lining at least a portion of a bend in a pipe has a concave surface which is curved through 45 DEG to 360 DEG , and preferably from 135 DEG to 175 DEG of arc. The tile is shaped for assembly in edge-to-edge relationship with a plurality of similarly shaped tiles to form a portion of a generally toroidal or cylindrical surface. The tile may be cast from basalt, alumina or silicon carbide. <IMAGE>

Description

SPECIFICATION Tiles for lining pipes This invention relates to tiles for lining pipes, and more particularly to tiles for lining bends in pipes. The invention also relates to pipes having a lining comprising one or more such tiles.

Pipes which are intended for carrying highly abrasive or corrosive materials are commonly lined with a material other than that from which the pipe itself is formed. This means that the material of the pipe itself can be selected on the basis of its strength or other properties, while the desired degree of abrasion or corrosion resistance is provided by the lining material. For example, pipes which are used for carrying pulverised fuel to the furnaces of power stations are commonly made of mild steel in order to provide the necessary strength, the inner surface of the pipe being rendered wear resistant by lining with a hard ceramic material.

In some applications, such as in the case of straight sections, the lining may be provided in the form of short cylindrical sections which are most usually spun cast cylindrical sections.

In other cases, and particularly in the case of bends in larger diameter pipes, however, the more usual practice is to line with individual tiles. The tiles are flat and are generally of the order of 5 cm square, this small size being chosen in order that a curved section of pipe can be lined with a minimum of discontinuity between adjacent tiles. It is particularly important that the lining of a bend in a pipe be as effective as possible, because bends (and particularly the outside or extrados thereof) are subjected to very much greater abrasion and erosion than are straight sections. This increased wear results from the breakdown of the laminar flow of material passing through the pipe, as it passes from a straight to a curved section.It will be appreciated, however, that even small tiles cannot adequately be used to line a bend in a pipe without a great deal of cutting to size and shape. Such cutting operations are rendered especially difficult by the fact that the material from which the tiles are formed is chosen specifically for its hardness and wear resistance.

The present invention provides an improved form of tile for lining a bend in a pipe.

According to the present invention there is provided a tile for lining at least a portion of a bend in a pipe, said tile having a concave surface which is curved through at least 450 of arc, and said tile being shaped for assembly in edge-to-edge relationship with a plurality of similarly shaped tiles to form a portion of a generally toroidal surface.

The tiles of the present invention have the advantage that they can be used to line the region of highest wear in the bend of a pipe (the extrados) without having any joints which are in line with the direction of flow of material which is transported through the pipe. It has been found that such in-line joints are particularly susceptible to wear, especially where (as is the usual case) the tiles are flat tiles which do not properly abut each other at the joints between them.

A further advantage of the tiles of the present invention is that they can be assembed to form a lining of more uniform section than is obtained using, for example, flat square tiles. This more uniform section minimises swirl, cavitation, boundary layer separation, turbulence and venturi effects in the material flowing through the pipe, thereby reducing wear.

A still further advantage of the tiles of the present invention is that they can be assembled to form a lining with far greater ease and far more quickly than can conventional tiles.

The greater the extent of curvature of the tile of the invention, the greater the proportion of the internal area of the of the pipe which can be lined without the need for in-line joints.

Preferably, therefore, the tiles of the invention are curved through at least 900 of arc, but preferably through a little less than 180" of arc, (e.g. from 1350 to 17.50 of arc) so as to be easily fitted in the bore of a pipe. The invention also contemplates tiles which form a complete annulus, such tiles being used to line the entire internal surface of a bend in a pipe, without any need for inline joints.

It will be understood that the expression "generally toroidal" is intended to embrace shapes which are not exactly toroidal. Thus, for examples, the curvature of the tile may be cylindrical rather than toroidal, the edges of the tile being defined by the lines along which the cylinder is intersected by a pair of planes which themselves intersect along a line parallel to the diameter of the cylinder. When a plurality of tiles of this shape are assembled in edge-to-edge relationship, the result is not a smooth toroidal surface, but a surface which in axial section through the pipe comprises a series of flats. The smaller the width of each such tile in relation to the radius of curvature of the bend which is to be lined, the more closely the surface approximates to the smooth toroidal shape which is generally preferred.

The expression "generally toroidal" is also intended to encompass the shape of a noncircular bend in a pipe, as well as the shape of a bend in a pipe of non-circular section.

The tiles of the present invention will be of particular usefulness in lining relatively large pipes, such as those having diameters of at least 10 cm, and more usually from 20 to 250 cm, e.g. from 30 to 150 cm.

The width of the tiles of the invention will to some extent depend on the diameter of the pipe of which they are to form a lining. For example, if the pipe which is to be lined has a diameter from 30 cm to 60 cm, suitable tiles will generally have a width (at their widest point) of from 10 to 100 mm, and preferably from 25 to 75 mm, e.g. 50 mm. a tile which is intended to line a pipe of diameter 100 cm will conveniently have a width greater than 50 mm, and preferably from 5 to 15 cm e.g. 10 cm.

The thickness of the tiles will depend not only on the size of the pipe which is to be lined, but also on the material from which the tile is to be formed, and the protective function which the tile is to serve. Generally, however, a ceramic tile for lining a steel pipe for carrying pulverised solids, such as solid fuel, will have a thickness of from 6 to 25 mm, and preferably from 6 to 15 mm, e.g. 10 mm.

The material from which the tiles are made will be chosen largely on the basis of the wear or corrosion resistance required. In the case of tiles for lining pipes for carrying pulverised solid fuel, for example, the tiles may be formed from a material such as alumina ceramic, basalt or silicon carbide.

An example of a suitable medium grade alumina ceramic for forming the tiles of the present invention is disclosed in British Patent Specification No. 1,563,784. This ceramic comprises 96% by weight alumina, the balance being silica (2.4%), ferrous oxide (0.6%) and titanium oxide (0.01%). Higher grade alumina ceramics (containing, for example, 97.5% alumina by weight), or lower grade alumina ceramics (containing from 85-90% alumina by weight) may also be used. Alumina ceramics of a variety of grades are available commercially.

Alumina ceramic tiles are usually formed by isostatic or die pressing. However, in view of the curvature of the tiles of the present invention, we have found that they are more conveniently produced by casing, and particularly by slip casting. It is therefore preferred to form the tiles of the present invention from castable materials such as alumina, basalt and castable silicon carbide.

Tiles according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of one end of a straight section of pipe lined with conventional square, planar tiles, Figure 2 is a perspective view, partially cut away, showing a bend in a pipe lined with tiles according to the invention, Figure 3 is a transverse section through the pipe of Fig. 2, Figure 4 is a view corresponding generally to Fig. 2 showing the use of an alternative form of tiles according to the invention, Figure 5 is a side view of a tile, Figure 6 is an end view in the direction of arrow A in Fig. 5, Figure 7 is a section on line VII-VII of Fig.

5.

Referring to Fig. 1, a steel cylindrical pipe 1 is lined throughout with a plurality of square, planar tiles 3, 3', 3" etc. For increased performance, each tile of a row along the length of the pipe is arranged in staggered relationship with the tiles of the adjacent row (compare tiles 3 and 3', 3' and 3" etc).

When it is desired to line a bend in a pipe, two principal difficulties arise. Firstly, it is necessary either for each tile to be shaped to accommodate the fact that the distance around the outside of the bend is greater than the distance around the inside of the bend, or for substantial gaps to be left between adjacent tiles. Neither solution is satisfactory. It is not commercially feasible to make tiles in the numerous different shapes which would be required to line a bend, and cutting tiles to shape on-site is both time-consuming and expensive. Leaving substantial gaps between adjacent tiles is unsatisfactory because tile fixing cements generally have a much lower resistance to abrasion than do the tiles themselves.

Secondly, if the staggered pattern of Fig. 1 is to be preserved, the edge-to-edge abutting relationship between adjacent rows of tiles (e.g. 3 and 3') cannot be maintained. The result is that a transverse section through the pipe in the region of the bend shows numerous steps and discontinuities, and the section varies in discontinuous fashion from one region of the bend to the next. These discontinuities and variations tend to disrupt the laminar flow of material through the pipe, causing greatly increased wear.

In Fig. 2 there is shown a section of a bend in a steel pipe 21, which complies with the Central Electricity Generating Board standard GDCD 215. The extrados of the bend of the pipe is lined with a plurality of curved tiles 23, arranged in edge-to-edge relationship. The tiles 23 are fixed to the pipe 21 by means of an adhesive lining compound 25 such as Wearwell Lining Compound, available from Atkins Fulford Limited.

The tiles 23 shown in Fig. 2 are of cylindrical curvature, as can better be seen from Figs. 5 and 6. Each is curved through approximately 1700 of arc, so that it can conveniently be inserted in the pipe bend which is to be lined. One major edge 62 is provided with a V-shaped tongue 74, while the other major edge 66 is provided with a correspondingly Vshaped groove 78 (see Fig. 7). Other forms of tongue, such as rounded tongues, may be used if desired, but we have found that in the case of curved tiles, V-shaped tongues give a better fit between adjacent tiles at the manufacturing tolerances which are commercially feasible thus providing joints which are more resistant to the wear caused by cavitation.

As will be appreciated from Fig. 3, the sub stantial curvature in the tiles 23 means that they may be effectively locked in position by adhesive lining compound 25 applied to the intrados of the pipe 21. That is to say, even if the direct adhesion between the tile 23 and the pipe 21 should fail, it is prevented from being dislodged by its neighbouring tiles and by its abutment with the layer of adhesive lining compound 25, as indicated in Fig. 3 by reference numeral 30. Of course, the same positive retention is also obtained when the pipe is lined with tiles on the intrados.

Optionally, each tile may be provided with a pair of holes 57. When the tiles are assembled in position in the bend of a pipe, those holes define two channels in which may be inserted steel wires. The ends of the wires may then be welded to the pipe shell, as an additional means of securing the tiles.

As is apparent from Fig. 2, the tiles of the present invention can be arranged to line the region of the pipe which is subjected to highest wear without any joints in line with the direction of flow of the material which is transported along the pipe. This means that a section through the pipe in the region of the bend shows no discontinuities in the region of the extrados, and the section shows minimal change from one region of the bend to the next. Turbulence and swirl are therefore reduced, with a consequent reduction in abrasion.

Even more extensive protection from abrasion can be achieved using annular tiles according to the invention, as shown in Fig. 4.

In this Figure, a steel pipe 41 is lined with a plurality of annular tiles 43 of cylindrical curvature, so that both the extrados and the intrados of the bend are lined.

It will be understood that the present invention has been described above purely by way of example, and that modifications of details can be made within the scope of the invention.

Claims (10)

1. A tile for lining at least a portion of a bend in a pipe, said tile having a concave surface which is curved through at least 450 of arc, and said tile being shaped for assembly in edge-to-edge relationship with a plurality of similarly shaped tiles to form a portion of a generally toroidal surface.

2. A tile according to claim 1, having a surface which is curved through at least 90" of arc.

3. A tile according to claim 1, having a surface which is curved through an arc of from 135O to 175"

4. A tile according to any preceding claim having a surface of cylindrical curvature, and the edge of the tile being defined by the lines aong which the cylinder is intersected by a pair of planes which themselves intersect along a line parallel to a diameter of the cylinder.

5. A tile according to any preceding claim, the radius of curvature of said surface being at least 5 cm.

6. A tile according to claim 5, wherein said radius of curvature is from 10 to 125 cm.

7. A tile according to any preceding claim, said tile being cast from an abrasion-resistant material.

8. A tile according to claim 7, wherein said abrasion-resistant material is basalt, alumina or silicon carbide.

9. A tile according to claim 1, substantially as hereinbefore described with reference to the drawings.

10. A pipe having a bend therein, said bend being lined with a plurality of tiles according to any preceding claim.