GB2165328A

GB2165328A - Pipe bends

Info

Publication number: GB2165328A
Application number: GB08425123A
Authority: GB
Inventors: Robert Ian Sykes
Original assignee: MORGAN ROCTEC Ltd
Current assignee: MORGAN ROCTEC Ltd
Priority date: 1984-10-04
Filing date: 1984-10-04
Publication date: 1986-04-09
Also published as: GB8425123D0; GB2165328B

Abstract

A pipe bend (1) for conveying abrasive particulate material having a rectangular cross-section, a cross- sectional area greater than that of the pipework to which the bend is to be connected, abrasion resistant lining (9, 10) of alumina-ceramic tiles bonded to the wall (4,5) of the bend and, at either end (3), connector means (12) including an adaptor (16) moulded from an alumina-ceramic material and internally shaped at one end (17) to conform to the internal cross-sectional shape of the bend and at the other end (18) to the internal cross-sectional shape of the adjacent pipe. <IMAGE>

Description

SPECIFICATION Pipe bends This invention relates to abrasion resistant pipe bends for conveying pulverised particulate material such as coal. It is known for large power station installations burning pulverised coal to line pipework carrying the coal, which is conveyed by a moving stream of air to the boiler burners. However, such pipe bends are of relatively massive size and of large radius making it simple to insert a moulded lining into a bend.

The present invention is particularly concerned with providing pipe bends for small boiler installations burning pulverised coal wherein the overall gauge of the metalwork has to be thinner and lighter and the radius of the pipe bends much tighter because of the restricted space within which such boilers usually have to be installed. In such situations conventional steel pipes have been known to have the radially outer wall of the bends thereof abraded through in a matter of ten days or so. The invention is equally applicable to other situations requiring the conveyance of an abrasive particulate material around small radius bends.

According to the present invention, a pipe bend for conveying abrasive particulate material has a rectangular cross-section, a crosssectional area greater than that of the pipework to which the bend is to be connected, abrasion resistive linings to the walls of the bend and, at either end, means to connect the pipe bend to adjacent pipes. Use of a rectangular cross-section increases the area of the pipe bend surfaces exposed to maximum abrasion; these surfaces being about the radially outer wall of the bend that experiences direct impingement of particulate matter and the radially inner wall that experiences abrasion by particulate matter reflected off the radially outer wall. Curved section pipe bends suffer maximum abrasion along an essentially longitudinal narrow band. Use of rectangular section increases the lateral width of this maximum abrasion band.The greater cross-sectional area of the pipe bend reduces the velocity of the particulate material and hence the abrasion; abrasion being a function of the cube of velocity.

In a preferred embodiment of the invention, the abrasion resistant linings are tiles of abrasion resistant alumina-ceramic material, the tiles for the radially outer and inner walls of the bend being of rectangular shape and the tiles for the sidewalls being tapered to allow for the radius of the bend. The material of the inner and outer wall tiles may be of a more abrasion resistant, alumina-ceramic than that of the sidewall tiles.

In another embodiment of the invention, one of the sidewalls is removably attached to the pipe bend, with the sidewall tiles bonded to the inner surface thereof, to permit in situ inspection of the pipe bend and to simplify replacement of worn tiles.

The means for connecting the pipe bends ends to adjacent pipes preferably include an adaptor moulded from alumina-ceramic material and having an internal shape that varies from, at one end, the cross-sectional shape of the pipe bend and, at the other end, the cross-sectional shape of the adjoining pipe.

The above and other features of the invention are illustrated, by way of example, in the Drawings wherein: Figure 1 is a perspective view of a pipe bend in accordance with the invention with one sidewall removed; Figure 2 is a plan of the pipe bend of Fig.

1; Figure 3 is a section on the line 3-3 of Fig.

2 but with the upper sidewall attached; Figure 4 is an end elevation of a pipe bend adaptor; and Figure 5 is a longitudinal section of the adaptor of Fig. 4.

As shown by the Drawings, a pipe bend 1 consists of a curved channel 2, of square cross-section with, at either end, a conventional circular mounting flange 3; all fabricated from mild steel.

The channel 2 is lined with a series of tiles made of abrasion resistant alumina-ceramic material. The tiles for the radially outer wall 4 and for the radially inner wall 5 are of simple rectangular shape whilst the tiles for the sidewalls 6 and 7 are of wedge shape to accommodate the radius of the bend. Whilst the tiles 8 and 9 of the outer and inner walls are shown to be curved, they would more usually, and depending on the hardness of the abrasion resistant material to be employed, be flat and only approximate to the curved shape of the channel 2.

The channel is closed by a further sidewall 6, having tiles 10 bonded to the under surface thereof. The sidewall 6 may be welded to the rest of the pipe bend, itself of welded construction, or more conveniently, may be removably attached such as by use of mounting bolts or clamps (not shown).

An adaptor 12 is attached to the mounting flange 3 at each end of the bend, the adaptor consisting of a rectangular metal shell 13, with a mounting flange 14 at one end and 15 at the other end. The shell 13 contains an alumina-ceramic moulding 16, the internal shape of which changes from the square cross-section 17 of the pipe bend at the flange 14 end to the cross-section of a pipe to which the bend is to be attached, for example a simple circular cross-section 18, at the flange 15 end. Flange 14 is shaped to attach to the pipe bend mounting flanges 3 whilst flange 15 can be of appropriate size and shape to match the mounting flanges for the rest of the pipework.The adaptor has to be of alumina-ceramic material to withstand abrasion as, especially at the downstream end of the pipe bend, the reduction in cross-sectional area from square to circular acts as a choke which will increase particle velocity and hence abrasion.

Provision of a removable sidewall 6 permits in situ inspection of the pipe bend, to assess the abrasion damage thereto, and also simplifies renovation of worn pipe bends by replacement and re-bonding of severely abraded tiles.

A suitable alumina abrasion resistant material for the outer and inner wall tiles 8 and 9 is a 97.5% sintered high alumina tile such as DERANOX 975 (Trade Mark), and a suitable composition for the sidewall tiles 10 and 11 and for the adaptor body 16 is a 96% sintered high alumina such as ROCTEC 960 (Trade Mark).

Finally, the bonding medium is an epoxy resin such as CIBA-GEIGY 136M and HU998 (Trade Marks).

Claims

1. A pipe bend for conveying abrasive particulate material having a rectangular crosssection, a cross-sectional area greater than that of the pipework to which the bend is to be connected, abrasion resistant linings to the walls of the bend and, at either end, means to connect the bend to adjacent pipes.

2. A pipe bend as claimed in claim 1, wherein the abrasion resistant linings comprise alumina-ceramic tiles bonded to the bend walls.

3. A pipe bend as claimed in claim 2, wherein the tiles bonded to the radially outer and inner walls of the bend are of a more abrasion resistant material than those of the tiles bonded to the sidewalls of the bend.

4. A pipe bend as claimed in any of claims 1 to 3, wherein one of the sidewalls is removably attached to the bend.

5. A pipe bend as claimed in claim 2 and claim 4, wherein the sidewall tiles are bonded to the removable sidewall.

6. A pipe bend as claimed in any of claims 1 to 5, wherein said connector means include an adaptor moulded from an alumina-ceramic material and internally shaped at one end to conform to the internal cross-sectional shape of the bend and at the other end to the internal cross-sectional shape of the adjacent pipe.

7. A pipe bend for conveying abrasive particulate material substantially described with reference to or as shown by the Drawings.