GB2078900A

GB2078900A - Lined conduits

Info

Publication number: GB2078900A
Application number: GB8118711A
Authority: GB
Original assignee: KILARD CO BURTON ON TRENT Ltd
Current assignee: KILARD CO BURTON ON TRENT Ltd
Priority date: 1980-06-21
Filing date: 1981-06-18
Publication date: 1982-01-13
Also published as: GB2078900B

Abstract

A conduit for conveying a pulverised fuel/air mixture comprises an outer casing (34) surrounding an inner lining (30) of hard wearing material, the latter being releasably located within the casing (34) and being spaced inwardly from the casing (34) to define an annular clearance (36). Tell tale holes (54) may be provided in the casing (34) such that, on puncture of the lining (30), penetration of the coal/air mixture into the annular clearance (36) will be apparent due to leakage of coal dust through the holes (54). The pipework including the conduit may then be closed off for repair and this can involve removal of the lining (30), replacement of a new lining, and re-use of the casing (34). The annular clearance (36) may have an infill of loose material such as wire wool which will further reduce the velocity of the coal/air mixture as it passes into the clearance (36) through a damaged lining (30). <IMAGE>

Description

SPECIFICATION Improvements in or relating to lined conduits This invention is concerned with improvements in or relating to lined conduits, especially but not exclusively conduits intended for the transportation of pulverised coal/air mixture.

For safety reasons conduits of this nature are formed from an assembly comprising inner and outer tubes the inner tube or liner normally being cast from a suitable material for example NIHARD.

The outer tube is provided as a safety measure as the pulverised coal/air mixture is abrasive and results in a degradation of the liner which utlimately punctures. In view of the nature of the mixture passing through the puncture spontaneous combus- tion could occur and in an attempt to obviate or mitigate the resultant danger of explosion the annular clearance between the liner and outer tube has been filled with a suitable grouting material after the tube and liner have been assembled.

This arrangement has been disadvantageous as not only has it been difficult if not impossible to readily detect a puncture in the liner but also when the liner has been punctured in view of the construction of the assembly of inner liner, outer tube and grout it has been necessary to replace the entire assembly.

According to one aspect of the present invention there is provided a lining for a conduit which is arranged to convey a pulverised fuel/air mixture, said lining being adapted to be located within an outer casing, being formed of a wear resistant material, and comprising means for enabling releasable retention of the lining in a spaced apart relation with the outer casing, whereby the lining can be removed when damaged for replacement.

According to another aspect of the present invention there is provided a conduit for conveying a pulverised fuel/air mixture, said conduit comprising an outer casing, means for releasably retaining an inner lining in the casing in an inwardly spaced relation therewith, whereby the lining can be removed when damaged for replacement, the lining being formed of a wear resistant material.

Preferably at least one opening is provided in the casing to provide communication between the exterior of the conduit and the spacing defined between the casing and the lining.

According to a further aspect of the present invention there is provided a method of forming a conduit for conveying a pulverised fuel/air mixture, said method comprising providing an outer casing and an inner lining which is formed of a wear resistant material, and releasably locating the inner lining within the outer casing in an inwardly spaced relation therewith, whereby the lining when damaged can be removed from the casing in situ for replacement purposes.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of a first embodiment of a conduit according to the invention Figure 2 is an end elevation of the embodiment of Figure 1; Figure 3 is a detail, shown in section, of a part of one end of the conduit, the lower end as viewed in Figure 1; Figure 4 is a detail, shown in section, of a part of the other end of the conduit, the upper end as viewed in Figure 1; Figure 5 is a sectional side elevation of a second embodiment of a conduit according to the invention Figure 6 is a detail, shown in section, of a part of the upper end of the conduit of Figure 5; Figure 7 is a detail, shown in section, of a part of the lower end of the conduit of Figure 5;; Figure 8 is a diagrammatic view of an alarm system for use with a conduit according to the invention; and Figure 9 is a diagrammatic view of an alternative alarm system for use with the conduit according to the invention.

Referring to Figures 1 to 4 of the drawings, a first embodiment of a conduit for transporting a pulverised coal/air mixture comprises a casing 14, preferably fabricated from mild steel, surrounding an inner lining 10, which is preferably cast from a suitable gard wearing material. The lining 10 is spaced inwardly of the casing 14 to define an annular clearance 16 between the lining 10 and the casing 14.

For mounting of the conduit at a desired location, a radially outwardly extending flange 18 is provided on the casing 14 at each end thereof. The flanges 18 are secured to the casing 14, for example by welding, and are provided with a plurality of fixing holes 20 as shown in Figure 2.

To close the annular clearance 16 at the lower end of the conduit, the lining 10 has a radially outwardly extending integral flange or nib 12, which may locate initially against inwardly extending small locating members (not shown) on the casing 14. To close the upper end of the clearance 16, the flange 18 at the upper end of the conduit has a radially inwardly extending flange or nib 24 projecting inwardly beyond the casing 14. Each of the flanges 18 defines a respective end face of the conduit which extends beyond the respective end face of the lining 10, and a coating 22 of a synthetic plastics material is applied to each end face of the lining 10 to be flush with the end face of the respective flange 18, such that a planar end surface is provided for the conduit without the need for expensive and time consuming machining.The synthetic plastics material is preferably an anti-degradation "ADI" epoxy resin filler.

The arrangement of the nibs 12 and 24 respectively on the lining 10 and the flange 18 ensures the concentricity of the lining 10 and the casing 14 and the maintenance of the annular clearance 16 therebetween.

Radially directed small diameter bores 26 are formed through each flange 18 and the outer casing 14 to provide communication between the annular clearance 16 and atmosphere. Four bores are provided in each flange 18.

When the conduit is in use, if the lining 10 is punctured, pulverised coal/air mixture will penetrate into the annular clearance 16 and will leak through the bores 26, immediately giving a visual indication of the breakdown of the lining 10. The dimension of the bores 26 is so chosen that the velocity of pulverised coal/air mixture passing therethrough is substantially less than that required to cause spontaneous combustion so that immediately the tell tale leakage of coal dust is detected, the run of pipework including the conduit may be closed off for repair.

The annular clearance 16 defines a radial spacing of less than 50 mm.

When repair is necessary the coating 22 can be broken down and the locating members removed, for example by burning off, whereby the damaged lining 10 can be withdrawn from the casing 14, through the lower end thereof. The lining 10 can then be replaced with a new lining enabling re-use of the casing 14. There is thus enabled a speedy and economic repair of the conduit.

Referring to the embodiment of Figures 5 to 7, a conduit comprises an outer casing 34, preferably fabricated from mild steel, surrounding an inner lining 30, which is preferably cast from any suitable hard wearing material. The casing 34 surrounds the lining 30 and is so dimentioned as to define an annular clearance 36 between the lining 30 and the casing 34. For mounting of the conduit at a suitable location, a radially outwardly extending mounting flange 38 is provided at each end of the conduit and may be secured to the casing 34, for example by welding. The flanges 38 are provided with fixing holes.

At the upper end, the flange 18 has an annular locating part for the lining 30 extending of the casing 34 to define the end face of the conduit. The part 40 terminates short of the inner periphery of the lining 30 and a coating 46 of a synthetic plastics material is applied to the exposed end face of the lining 30 to be flush with the end face of the part 40. Alternatively a hard surfacing material may be used. At the lower end, the lining 30 has a radially outwardly extending flange or nib 44 and the latter, together with the locating part 40, close the respective ends of the annular clearance 36. A series of thin locating members 42 are provided on the casing 34 to extend inwardly therefrom and engage the end face of the nib 44 and the members 42 allow for some expension of the lining 30.The lower end face of the casing 34 extends beyond the respective end face of the lining 30 with the flange 44. A coating 48 of a synthetic plastics material is applied to the end face of the lining 30 to be flush with the endface of the casing 34. The synthetic plastics material is preferably an anti-degradation "ADI" epoxy resin filler and a planar end can thus be provided for each end of the conduit without the need for expensive and time consuming machining.

The arrangement of the part 40 and the flange 44 ensures the concentricity of the lining 30 and the casing 34 and the maintenance of the annular clearance 36 therebetween.

Towards each end of the conduit, four bosses 50 are equi-spaced on and around the outer surface of the casing 34. Each boss 50 mounts a pair of spaced bolts 52 extending through respective thread apertures in the boss 50 to project inwardly of the casing 34 into engagement with the lining 30. Between the bolts 52 on each boss 50 there is provided a hole 54 extending radially through the boss 50 and the casing 34 to provide communication between the annular clearance 36 and the atmosphere. The engagement of the bolts 52 with the lining 30 prevents twisting of the lining 30 relative to the casing 34.

When the conduit is in use, if the lining 30 is punctured, pulverised coal/air mixture will penetrate into the annular clearance 36 and will leak through the holes 54 immediately giving a visual indication of the breakdown of the the lining 30. The dimension of the holes 54 is so chosen that the velocity of pulverised coai/air mixture passing therethrough is substantially less than that required to cause spontaneous combustion so that immediately the tell tale leakage of coal dust is detected, the run of pipework including the conduit may be closed off for repair.

The annular clearance 36 has a radial dimension of less than 50 mm.

As in the first embodiment a damaged lining 30 can be withdrawn from the casing 34 by effecting breakdown of the coatings 48, removing the locating members by burning off, and then withdrawing the damaged lining 30 through the lower end of the coduitwith the aid of the exposed pin 46. The lining 30 may then be replaced with a new lining enabling re-using of the casing 34. This results in the speedy and economic repair of the conduit.

The conduit according to either of the embodiments reduces the total thickness of the structure measured from the inside diameter to the outside diameter and this is advantageous in minimising the energies released if an explosion happens to take place.

In either embodiment the annulrclearance may have an infill of a material which can still enable free withdrawal of the inner lining. The infill material will further reduce the velocity of the coal/air mixture as it passes into the annular clearance through a damaged lining and, for example, the infill material may be wire wool.

In a modification, the bores or holes for giving visual indication of the breakdown of the lining may be omitted, although it would be preferred to provide at least one vent hole so as to allow for any expansion of air due to uneven expansion of the materials of the lining and the casing.

In a further modification, each end face of the conduit may have a coating extending over the end area of the lining and the annular clearance, with a locating ring being mounted internally on the casing of the lower end instead of the inwardly projecting flange part.

As an alternative to the use of bores or holes for - giving a visual indication of the breakdown of a lining, an external alarm system may be provided.

With reference to Figure 8, a diaphragm unit 60 has an air line 62 communicating with the annular clearance between the casing and the lining through a suitable tapping 64. The unit 60 provides a valve located in a pneumatic line between an air supply 66 and a pneumatically operated alarm 68. When the lining is damaged, the change in pressure within the annular clearance and the air line 62 operates the valve to provide communication between the air supply 66 and the alarm 68 such that the latter is activated. The alarm may be in the form of, for example, a whistle, such that an operator is immediately notified of any damaged lining and the run of pipework including the damaged conduit may be closed off for repair.With the type of alarm system described, a vent orifice 70 is incorporated in the casing to communicate between the annular clearance and the atmosphere so that any change from atmospheric pressure within the annular clearance due to heat generated will not falsely operate the diaphragm unit.

In a modification of this alarm system, a series of conduits may each have a diaphragm unit, with the units having a common air supply and being connected via isolator valves, which are hand operated, to a common return line. The latter may connect to a floor level module comprising an air operated valve with manual push button re-set which in turn would connect to an alarm, for example in the form of a whistle. When a conduit lining fractures, the respective diaphragm unit would enable air to pass down the return line to operate the valve in the module and sound the alarm until monthly re-set. The operator would then identify the fractured lining by isolating the valve on each respective diaphragm until the alarm switches off. The damaged lining can then be replaced.

In an alternative alarm system as shown in Figure 9, a valve module 72 has an air line 74 communicating with the annular clearance in a lined conduit. A valve in the module controls communication between an air supply 76 and an alarm 78, for example in the form of a whistle, and a line also communicates between the air supply 76 and the air line 74 through a venturi 80. Thus the annular clearance is pressurised at mains air pressure and while at this pressure the valve which is biased open, is held closed. On the occurrence of a fracture in the lining, the pressure downstream of the venturi 80 drops rapidly allowing the valve to change under its biasing force to an open position, which opens communication between the air supply 76 and the alarm 78 for activation of the latter. In a modification of this arrangement a series of conduits may each be connected with a similar alarm circuit, with the circuits communicating between a common air supply alarm module at floor level, of the type described in the modification of the alarm arrangement of Figure 8.

Various other modifications may be made without departing from the invention. For example a conduit may have the inner lining of constant diameter but with the outer casing having a varying diameter at the outer side relative to a bend in the conduit, so as to provide increased spacing between the lining and the casing at the area where the stresses are greatest. Further, the casing need not of course be fabricated but could also be a cast member.

Claims

1. A lining for a conduit which is arranged to convey a pulverised fuel/air mixture, said lining being adapted to be located within an outer casing, being formed of a wear resistant material, and comprising means for enabling releasable retention of the lining in a spaced apart relation with the outer casing, whereby the lining can be removed when damaged for replacement.

2. A lining according to the claim 1, wherein the spacing means comprises an external flange on one end of the liner, the flange in use forming on end closure between the lining and the casing.

3. A lining according to claim 1 or 2, which is formed from a cast material.

4. A conduit for conveying a pulverised fuel/air mixture, said conduit comprising an outer casing, means for releasably retaining an inner lining in the casing in an inwardly spaced relation therewith, whereby the lining can be removed when damaged for replacement, the lining being formed of a wear resistant material.

5. A conduit according to claim 4, wherein the spacing defined between the casing and the lining is less than 50 mm.

6. A conduit according to claim 4 or 5, wherein means are provided for closing each end of the spacing defined between the casing and the liner.

7. A conduit according to claim 6, wherein the closing means comprises an external flange on the lining at one end of the conduit, and an internal flange on the casing at the other end of the conduit.

8. A conduit according to claim 7, wherein each end face of the outer casing extends beyond the respective end face of the lining and a coating of a synthetic plastics material is provided on each end face of the lining to be flush with the respective end face of the outer casing.

9. A conduit according to claim 8, wherein the synthetic plastics material is an anti-degradation epoxy resin.

10. A conduit according to any of claims 4 to 9, wherein at least one opening is provided in the casing to provide communication between the exterior of the conduit and the spacing defined between the casing and the lining.

11. A conduit according to any of claims 4 to 10, wherein an external mounting flange is provided at each end of the casing for securing of the conduit.

12. A conduit according to claim 11, when dependent on claim 10, wherein a plurality of the openings are provided to extend through the mount- ing flanges.

13. A conduit according to any of claims 4to 11, wherein the or each opening extends through a boss located externally on the casing, the or each boss locating means which extend into engagement with the lining to prevent twisting thereof.

14. A conduit according to any of claims 4 to 11, wherein an infill material is provided loosely in the spacing defined between the casing and the lining.

15. A conduit according to claim 14, wherein the infill material comprises wire wool.

16. A conduit according to any of claims 4 to 11 or claim 14 or 15, wherein pneumatic valve means are provided to have an operating line communicating with the spacing defined between the casing and the lining, the valve means controlling communication between a pneumatic alarm and a supply of pneumatic operating medium therefor, whereby a substantial change in pessure of air in the spacing operates the valve means to enable activation of the alarm.

17. A conduit according to claim 16, wherein there is provided means for introducing compressed air into the spacing whereby a substantial change in the pressure of the compressed air in the spacing operates the valve means to enable activation of the alarm.

18. A conduit according to claim 1i, wherein the pneumatic operating medium is compressed air and a a common supply is provided for the compressed air for the spacing and for the alarm.

19. A method of forming a conduit for conveying a pulverised fuel/air mixture, said method comprising providing an outer casing and an inner lining which is formed of a wear resistant material, and releasably locating the inner lining within the outer casing in an inwardly spaced relation therewith, whereby the lining when damaged can be removed from the casing in situ for replacement purposes.

20. A lining for a conduit which is arranged to convey a pulverised fuel/air mixture, substantially as hereinbefore described with reference to the accompanying drawings.

21. A conduit for conveying a pulverised fuel/air mixture, substantially as hereinbefore described with reference to the accompanying drawings.

22. A method of forming a conduitforconveying a pulverised fuel/air mixture, substantially as hereinbefore described with reference to the accompanying drawings.

23. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.