METHOD AND APPARATUS FOR REPAIRING DETERIORATED REFRACTORY LININGS IN LARGE VERTICAL SHAFT KILNS, FURNACES ₅ CYCLONES AND THE LIKE

This invention relates to methods and apparatus for the removal of deteriorated refractory linings in large industrial vessels, such as vertical shaft kilns, furnaces, cyclones and the like. hi the refurbishing of refractory linings in large industrial vessels, such as vertical shaft kilns, furnaces, cyclones and the like, it is common for scaffolding to be erected within the interior space of the unit and for workers working at discrete stage levels on said scaffolding to remove deteriorated refractory lining using manually-operated tools. Such large industrial vessels may be of great vertical development or may be in elevated situations, necessitating the use of scaffolding for safe working access. Diameters of such large industrial vessels may be more or less constant and range from one metre to more than 5 metres, or may vary considerably throughout their height and range from several metres to in excess often. The cost of restoring the refractory linings of a typical large industrial vessel is high and may occupy many days, or even weeks. More importantly, the cost of lost productive output of an associated plant during the restoration process may considerably exceed the actual cost of restoration.

The first object of the present invention is to provide a method and apparatus for the removal and replacement of deteriorated refractory linings in large industrial vessels which does not require the use of scaffolding. A second object of the present invention is to provide such method and apparatus enabling rapid removal of deteriorated refractory linings in such large industrial vessels through the use of powerful, power- operated tools and with a minimal labour requirement. A third object of the present invention is to provide such method and apparatus enabling rapid removal of deteriorated refractory linings in such large industrial vessels through the use of multiple small charges of explosive material. A fourth object of the present invention is to provide a work platform

deployable in such large industrial vessels to support workers reinstating said removed refractory linings. A fifth objective of the present invention is to provide a working apparatus which may be broken down into component parts of sufficient lightness and compactness to be hoisted into an elevated work situation, entered through limited access means and readily assembled to provide a strong and safe unit. And a sixth of object of the present invention is to provide work procedures based upon said method and apparatus which permit accurate planning of the timing of the work. According to the present invention, immediately following shutdown and ventilation of a large industrial vessel and during cooling, inspection of the refractory lining is conducted using closed-circuit (CCTV) television cameras and oblique flood lighting. If necessary, said CCTV cameras and flood lighting means are protected from radiant heat by suitable reflective coverings and kept cool by air blast. CCTV camera images of the internal surfaces of the large kirn, furnace, cyclone or the like are recorded and studied to determine details of the work required, to plan the work and to compute the cost and time for its performance. Prior to commencement of the restoration work, all gas ducting and feeding provisions at the top of the large kiln, furnace, cyclone or the like are removed or suitably displaced to provide free access to the internal space. A head frame is installed at the top of said large industrial vessel and a mobile work platform lowered into its interior space supported on cables from a hoist fixed to said head frame. Said work platform is rotationally supported on a suspension bearing via suspension rods and a spreader frame and comprises underframe and bearing; airleg-type rock drill; debris chute; hydraulic power unit; compressed air, water and electricity supply and control means; rotational displacement means; communications means, and ventilation means. Rotationally supported from said work platform is a carrier unit comprising; steady arms; steady arm actuators; rotational displacement actuator; broken suspension cable sensing means; and anti-fall means.

In operation, said work platform and carrier unit are raised to the desired height in the interior of a large industrial vessel and locked into position by extending said steady arms. An operator controls said hoist and said steady arm extension using manual controls. Said operator then operates said airleg-type rock drill to drill into solid refractory lining which is then broken out by detonating small charges of a suitable explosive in said drill holes. Said work platform is raised above the work zone prior to said detonations, a protective shield being provided on the lower surface of said carrier unit to minimise the possibility of damage from flying debris. Already fractured refractory lining is dislodged using suitable tools in said airleg-type rock drill. Dislodged material is captured in the top hopper of said debris chute and falls via said chute to the bottom of said kiln, furnace, cyclone or the like where it is collected for disposal. Said debris chute is located at the centre of said work platform and is made modular with additional sections being added as said work platform is raised. Said central location of said debris chute ensures that its weight is always immediately below the supporting cable of said work platform. Said airleg-type rock drill is made of a suitable length to suit the diameter of said large kiln, furnace, cyclone or the like. It is rotatable through 360°, may be extended radially to approach the interior surface of said large kiln, furnace, cyclone or the like and may be tilted up and down each by at least 45°. With said carrier locked into place by said steady arms, said work platform is rotatable through 360°. Rotation of said work platform provides full access to all said refractory lining surfaces and brings said top hopper of said debris chute into place beneath a work zone, hi the event of cable breakage or hoist failure, a signal from said broken suspension cable sensor triggers means to rapidly and fully displace said steady arms to prevent uncontrolled descent of said work platform.

The various aspects of the present invention will be more readily understood by reference to the following description of preferred embodiments given in relation to the accompanying drawings in which:

Figure 1 is a vertical cross-sectional view of said head

frame and associated components;

Figure 2 is a vertical cross-sectional view of said carrier unit and said work platform.

Figure 3 is a partial side view of an alternative embodiment of said carrier unit and said work platform;

Figure 4 is a partial side view of another alternative embodiment of said carrier unit and said work platform;

Figure 5 is a partial plan view of the embodiment depicted at Figure 4, with supported panels removed; Figure 6 is a partial transverse cross-sectional view of connection means for the mounting of work platform panels in the embodiment depicted at Figures 4 and 5;

Figure 7 is a partial face view depicting bore holes drilled to weaken a monolithic mass of refractory lining material and the positioning of charges for its removal;

Figure 8 is a partial longitudinal cross-sectional view of a deflagrating explosive cartridge accommodated in a bore hole;

Figure 9 is a partial face view of an alternative arrangement of the embodiment depicted in Figure 7. It should be noted that the figures are drawn to the different scales.

With reference to Figures 1 and 2, immediately following shutdown and ventilation of a large industrial vessel, such as a vertical shaft kiln, furnace, cyclone or the like and during cooling, inspection of the refractory lining is conducted using closed-circuit television (CCTV) cameras and oblique flood lighting (not shown). If necessary, said CCTV cameras and flood lighting means are protected from radiant heat by suitable reflective coverings and kept cool by air blast. CCTV camera images of the internal surfaces of said large kiln, furnace, cyclone or the like are recorded and studied to determine details of the work required, to plan the work and to compute the cost and time for its performance. Prior to commencement of restoration work, all gas ducting and feeding provisions (not shown) at the top of said large industrial vessel are

removed or suitably displaced to provide free access to the internal space. A head frame 1 is installed at the top of said large industrial vessel 2 and a mobile work platform assembly 3 lowered into the interior space of said large kiln, furnace, cyclone or the like supported on suspension cable 4 deployed from a suitable hoist 5 fixed to said head frame. Said cable is led from the drum 8 of said hoist and over suitably positioned sheaves 6, 7 such that the load on said cable is always maintained on the centreline of said hoist. A work surface 3 a of said work platform is rotationally supported on a suspension swivel bearing 9 provided at the lower end of cable 4, a plurality of angled suspension rods 10 being fixed to said swivel bearing and circular spreader frame 11. A plurality of vertical suspension rods 12 are fixed to said spreader frame and work surface 3. A broken suspension cable sensor (not shown) is incorporated into said suspension swivel bearing. Said work platform assembly comprises underframe 13; carrier unit 3b; carrier support bearing 14; airleg-type rock drill 15; debris chute 16; hydraulic power unit 20; lighting means; compressed air, water and electricity service connection lines or cables 17, 18, 19 and their control means (not shown); circular rotational displacement rack 22; communications means (not shown), and ventilation means 21. In the preferred embodiment, a suitable chest is provided on said work surface for the safe storage of explosive material used in breaking up said refractory lining together with a suitable accommodation for an electric exploder. Said airleg-type rock drill is mounted on centrally-located pedestal 23 fixed to said work surface, hi the preferred embodiment, said angled and vertical suspension rods take the form of solid or hollow rods of a suitable material, clevis fittings 31 at their ends being connected to complementary fittings at said swivel bearing, said spreader frame and said work surface by means of suitable quick-release pins (not shown), hi an alternative embodiment, said angled and vertical suspension rods take the form of suitable cables with said clevis fittings swaged to their ends. hi another alternative embodiment, threaded ends of said suspension rods are screwably attached to complementary sockets provided on said work

surface, said spreader frame and said swivel bearing and locked by means of suitable pins or nuts. In the preferred embodiment, work surface 3a is made from a strong metal mesh. Also in the preferred embodiment, said head frame and said work platform assembly are purpose built to suit a large kiln, furnace, cyclone or the like of a particular diameter and configuration. Also in the preferred embodiment, the structural components of said head frame are made from strong, hollow, light-weight metal alloy sections and are adapted to be readily assembled in situ. Bracing struts and/or gussets employed to stiffen said head frame have been deleted from the figures for clarity of illustration. Obviously, for some types of work, said airleg-type rock drill may be replaced by a smaller rock drill. Said smaller rock drill is optionally manually supported or supported by a cable from a recoiling spring drum or counterweighted beam. Rotationally connected to said work surface on bearing 14 is carrier unit 3b comprising; steady arms 25 pivoting on bearing brackets 24; steady arm actuators 26; rotational displacement actuator 27; and anti- fall control unit (not shown). With said steady arms extended to bring their shoes 28 into contact with the refractory lining 29 of said large vertical shaft kiln, furnace, cyclone or the like rotational displacement actuator 27 is operated by said operator to rotationally drive pinion 30 engaged with circular rack 22 to rotationally displace said work surface together with said vertical suspension rods and said debris chute. Apron 32 of a suitable elastic polymer material projects outwardly from the upper, outer edge of top hopper 33 of said debris chute into contact with refractory lining 29 and acts to direct dislodged material into said top hopper. In the preferred embodiment, hydraulic power unit 20 is of the conventional arrangement well known in the art and operated by electricity or compressed air, supplying pressurised hydraulic fluid to control valves on said airleg-type rock drill via hydraulic supply and return lines 34. Said hydraulic power unit incorporates a suitable accumulator (not shown) to store a supply of pressurised hydraulic. fluid. Water and compressed air

are supplied to said airleg-type rock drill via lines 17, 18. Ventilation air is supplied via flexible duct 21 which may be fitted at its lower end with suitable flow direction means (not shown). Air, water and electrical power lines 17, 18, 19 pass vertically up said large vertical shaft kiln, furnace, cyclone or the like close to cable 4 and pass outwardly via multiple sheaves 35, 36 fixed to sheave support beam 37. Said sheave support beam is removably fixed to one side of head frame 1 with multiple sheave 35 positioned closely adjacent cable 4. Flexible air duct 21 passes upwardly through the interior of said large industrial vessel and outwards over a suitably shaped shoe (not shown) positioned on lower frame 38 of said head frame. In the preferred embodiment, ventilation air flow is provided by a suitable fan at said head frame with said flexible air duct passing down the outside of said large industrial vessel for a suitable distance and then up and over said suitably shaped shoe, hi an alternative embodiment, said ventilation air flow is generated by a discharge of compressed air through a venturi-type ejector situated towards the delivery end of said flexible air duct. Where required, an industrial vacuum duct is deployed in a similar way to collect dust and fine debris generated at a work site. Hoist 5 is of the conventional arrangement well known in the art and, in the preferred embodiment, its drive motor 42 is powered by electricity. Also in the preferred embodiment, said hoist incorporates a braking unit (not shown) which operates to lock drum 8 of said hoist when said drive motor of said hoist is unpowered. Said operator is provided with a suitable pendant control unit (not shown) at said work surface and, from said control unit, control cables (not shown) pass upwardly through the interior of said large industrial vessel over sheaves 35, 36, down to a suitably positioned, weighted sheave (not shown) outside of said large kiln, furnace, cyclone or the like and upwardly (as supply line 39) to said hoist. In alternative embodiments, said hoist is pneumatically or hydraulically powered with suitable controls (not shown) being provided at said work platform.

In operation, said work platform assembly, including said carrier

unit, is raised to the desired height in the interior of said large industrial vessel and locked into position by extending said steady arms. Said operator controls the operation of said hoist and the extension of said steady arms using manual controls. Said operator then operates said airleg-type rock drill to drill into solid refractory lining 29 which is then broken out by igniting or detonating small charges of suitable explosive (not shown) in said drill holes. Said work platform assembly is raised above the work zone prior to said ignitions or detonations, a protective shield 40 being provided on the lower surface of said carrier unit to minimise the possibility of damage from flying debris. Already fractured refractory lining is dislodged using suitable tools (not shown) in said airleg-type rock drill. Dislodged material is captured in said top hopper of debris chute 41 and falls via said chute to the bottom of said large kiln, furnace, cyclone or the like where it is collected for disposal, hi the preferred embodiment, said debris chute is made modular, comprising a plurality of frustoconical sections of a tough, stiff polymer material joined telescopically, and additional sections are added as said work platform is raised. The use of such debris chutes is well known in the art. Said airleg- type drill is rotatable on pedestal 23 through 360°, may be extended radially to approach the interior surface of said large kiln, furnace, cyclone or the like and may be tilted up and down each by at least 45°. With said carrier locked into place by said steady arms, said work platform is rotatable through 360° on swivel bearing 9. Rotation of said work platform provides full access to all said refractory lining surfaces and brings said top hopper of said debris chute into place beneath a work zone.

Care is required to ensure that successive rotational displacements of said work platform take place is opposed directions to avoid entangling said service connection cables and supply lines with cable 4. Cable 4 is connected to swivel bearing 9 by a link (not shown) incorporating a strong spring which is normally kept compressed by the weight of said work platform and said carrier. An electrical emergency switch (not shown) is mechanically connected across said link and its contacts are made by the

compression of said link. Current flowing through said contacts of said emergency switch act to maintain an emergency hydraulic solenoid valve (not shown) in the closed position against spring pressure. Said emergency hydraulic solenoid valve connects said accumulator of said hydraulic power unit to shuttle valves (not shown) in the supply lines to steady arm actuators 26. With said emergency hydraulic solenoid valve powered, a normal flow of hydraulic fluid is permitted from said hydraulic power unit, via manual control valves, to said steady arm actuators. In the event of cable breakage or hoist failure, extension of said link breaks said switch depowering the solenoid of said emergency hydraulic valve and allowing said emergency hydraulic valve to be opened by spring pressure to direct the stored pressurised hydraulic fluid in said accumulator to fully and immediately displace said shoes of said steady arms powerfully into contact with said refractory lining of said large kiln, furnace, cyclone or the like, thereby preventing uncontrolled descent of said work platform. The pressure of said emergency flow of hydraulic fluid acts to displace said shuttle valves to lock out the normal operating hydraulic circuits for said steady arm actuators, hi the preferred embodiment, said shoes of said steady arms are each provided with a plurality of raised ridges of hard facing material which augments the frictional engagement of said shoes with said refractory lining surface, hi the preferred embodiment, suitable rescue equipment is maintained on site to permit escape of operators in a situation in which said hoist is immobilised for some reason.

In the preferred embodiment, said head frame together with said work platform and said carrier are lifted into position in a said large vertical shaft kiln, furnace, cyclone or the like using a suitable crane. Lower frame 38 of said head frame is securely clamped or bolted to structural members 43 at the top of said large industrial vessel, sheave support beam 37 is installed on said head frame, said lines and cables are installed and connected and operations are commenced as described. In an alternative embodiment, suitably .trained personnel obtain ladder access to the top of said large kiln, furnace, cyclone or the like and haul up a light-

weight shearlegs and winch apparatus which is fixed into place. Said head frame members are hauled up using said shearlegs and winch apparatus and assembled in place at the top of said large industrial vessel. Said head frame includes hoist transport rail 44 along which carriage 45 of said hoist travels freely. A suitable safely net is deployed across the open top of said large industrial vessel during assembly of said head frame and all personnel working at the top of said large kiln, furnace, cyclone or the like wear safety harnesses and suitable head protection at all times. Suitable safety warning signs are also deployed. With said head frame assembled, said hoist is positioned on said hoist transport rail and connected to an electricity supply and controls. Said hoist is deployed out along said hoist transport rail and employed to raise said work platform and carrier assembly and position it in the interior of said large industrial vessel where it is supported, correctly positioned, on temporary cables (not shown) fixed to suitable fittings (not shown) on said head frame. Said airleg-type rock drill and its said pedestal are brought up and positioned on said work platform. Said swivel bearing, said suspension rods and said spreader frame are assembled and connected to said work platform. Cable 4 is connected to said swivel bearing, said hoist is operated to take the load and said temporary cables are removed. Said sheave support beam is installed on said head frame, said lines and cables are installed and connected and operations are commenced as described. Where said work platform assembly in its uppermost position is inconveniently below the top of said large industrial vessel, access is gained to it by means of a flexible ladder (not shown) fixed to said spreader frame or lower frame 38 of said head frame. In another alternative embodiment, where access is available at the lower end of a said large industrial vessel, said work platform assembly, including said carrier unit, is assembled there and lifted by said hoist after assembly. In the preferred embodiment, a narrow footway (not shown) is provided around the outside of said head frame to facilitate work on said head frame and said work platform. In an alternative embodiment, a small railed pulpit (not shown) capable of

accommodating two or more persons is provided at said head frame. Where appropriate a separate adaptor frame is made for each work situation, said adaptor frames being designed to accept and support said head frame. The length of said airleg-type rock drill is selected to suit the diameter of said large kiln, furnace, cyclone or the like in which work is to be conducted. Care is exercised in rotationally displacing said work platform to ensure that electricity supply and control cables and service supply lines do not become excessively twisted, hi the preferred embodiment, all said electrical circuits are made intrinsically safe. Said debris chute is preferably led out through a suitable access opening and permitted to discharge directly into a suitable collection bin. The arrangement eliminates double handling and minimises the possibility of damage to equipment or personnel by falling debris.

With reference to Figures 3, 4 and 5 in an alternative embodiment, said work platform assembly, including said carrier unit, is made such as to readily permit its deployment in a said large industrial vessel in which access is gained to the interior space through an opening of restricted size, such as a manway or the like. In this embodiment, said work platform assembly comprises an axial supporting column 46 from the lower edge of which carrier unit 47 is rotationally supported on suitable bearing means (not shown). Said work platform assembly comprises said supporting column, a plurality of supporting panels 50 fixed to it and a plurality of supported panels 63 fixed to said supporting panels. Said supporting panels are fixed to said supporting column by rails 52 fixed to the inner ends of bracing panels 49 slidingly engaging complementary attachment channels 48 fixed to the exterior surface of said supporting column. A suitable locking fastening (position indicated as feature number 61) is employed to lock rails 52 in position in channels 48. The lower surfaces of said supporting panels are strongly joined to the upper edges of said bracing panels. In the preferred embodiment, said supporting panels are made from a suitable light, stiff, strong material in the form of an open grating having regularly-shaped apertures in area ranging from nine to 15

square centimetres. Also in the preferred embodiment, attachment channels 48 and rails 52 are made round. In alternative embodiments, said channels and said rails are made in any suitable complementary shape, including square and T-shaped. Supported panels 63 are provided along their radial edges with as plurality of downwardly-directed attachment pins 62 supported from lugs 76 provided along said radial edges. Said supporting panels are provided with a plurality of complementary sockets 51 provided along their radial edges. In assembling said work platform, said supporting panels are fixed to said supporting column and said locking fastening installed and tightened. Said supported panels are then installed with their attachment pins 62 engaging sockets 51 of said supporting panels. With all said supporting and supported panels installed, said work platform is effectively locked into a unitary whole. In the preferred embodiment, said work platform is made round, hi alternative embodiments, said work platform is made square, hexagonal, octagonal or other suitable regular geometric shape.

The hydraulic power unit described in relation to Figures 1 and 2 is accommodated within supporting column 46, but supported from carrier 47. In the preferred embodiment, controls for all hydraulic functions are provided in a pendant control unit, the terminal plug of the cable of which is connected to a suitable multi-pin socket (not shown) provided on that part 77 of said supporting column projecting above the level of said work platform, hi the preferred embodiment, a suitable electric power supply cable is connected in a similar way and conductors from this and from said multi-pin socket pass to said hydraulic power unit via a multi-pole slip- ring unit, the axis of which is maintained collinear with that of said supporting column and said carrier, hi an alternative embodiment, said controls (not shown) for all hydraulic functions are provided mounted directly on part 77. hi another alternative embodiment, said hydraulic power unit is pneumatically powered and a supply of compressed air is connected to suitable connection means provided on part 77 and connected to said hydraulic power unit via a suitable rotary joint, the axis

of which is maintained collinear with that of said supporting column and said carrier. Attachment means 53 are provided at the outer ends of supporting panels 50, normally on the centreline of each. Where the top hopper 33 of a debris chute (as described hereunder) is incorporated into a said supporting panel, attachment means 53 are provided at each side of it at the outer end of said supporting panel. In the preferred embodiment, vertical suspension rods 12 are connected to spreader frame 11 (as described in relation to Figure 2) and to said attachment means of said supporting panels in the manner described in relation to Figure 2. Pedestal 23 to support said airleg-type rock drill is fixed to attachment plate 78 provided at the upper end of said supporting column. Pivotally supported from carrier unit 47 and passing radially outwards through suitable apertures are three or more steady arms 66. In the preferred embodiment, said steady arms are made telescopic with extendible parts 67 slidingly accommodated inside them and extended as required by internal small hydraulic rams (not shown). Suitable shoes 28 are provided on the outer ends of said extendible parts and, in the preferred embodiment, said shoes are each provided with a plurality of raised ridges of hard facing material which augments the frictional engagement of said shoes with said refractory lining surface. In the preferred embodiment, said steady arms are pivotally mounted on the shafts of suitable vane-type, hydraulic rotary actuators (not shown) and flexible hoses (not shown) are provided to convey pressurised hydraulic fluid from said control valves to said small hydraulic rams and to conduct the return flow. In an alternative embodiment, said steady arms are deployed to their radial positions by small hydraulic rams. During insertion of said supporting column and said carrier into a said large industrial vessel, said extendible parts of said steady arms are retracted and said steady arms are displaced into positions parallel with the longitudinal axis of said supporting column (position indicated in broken line as 66a), the mode of displacement being indicated by arc 75. Where said steady arms form part of an anti-fall system (as described in relation to Figures 1 and 2), they are braced against upwardly

bending forces by strong cables 74, end fittings 72, 73 of which are connected to fittings 70, 71 provided, respectively, on the lower end of strut 69 and the lower surfaces of the outer ends of steady arms 66. In the preferred embodiment, said end fittings of said strong cables are such as to permit the ends of said strong cables to pivot freely during movement of steady arms 66, thereby minimising the possibility of kinking damage to said strong cables. Said strut is fixed to the lower surface of carrier 47 and positioned generally coUinear with said carrier and said supporting column. Gussets serving to reinforce the position of said strut have been deleted for the purpose of illustrative clarity. With said steady arms deployed to their radial positions, said strong cables are maintained in tension and should said anti-fall system (as described in relation to Figures 1 and 2) be activated, act to prevent upward deflection of said steady arms. Where this embodiment of the present invention incorporates said anti-fall system, shoes 68 are urged against said refractory lining of said large kiln, furnace, cyclone or the like by said small hydraulic rams. A suitable hydraulic rotary actuator (not shown) is provided on said carrier driving a suitable pinion engaging a complementary circular rack (not shown). Operation of said rotary actuator causes said supporting column to be rotationally displaced when said shoes of said steady arms are engaged with said surface of said refractory lining. Where required, a safety fence is provided around said work platform, said fence taking the form of any suitable barrier material supported on stanchions 64 plugged into sockets 65 provided in the outer ends of said supported panels. In the preferred embodiment, one said supporting panel is made to incorporated the top hopper 33 of debris chute 41, said debris chute being largely as described in relation to Figures 1 and 2. In the preferred embodiment, said top hopper is connected to said debris chute by a telescopic duct 54, 55 and flexible joint 56 and said top hopper is supported on rails 59 slidingly supported in bearings 58. Said bearings are supported on twisted struts 57 fixed to the sides of said supporting panel and the outer ends of said rails are fixed to lugs 60 provided on the sides

of said top hopper. In the preferred embodiment, said top hopper is provided with apron 32 of a suitable durable, elastic polymer material, said apron projecting outwardly from the upper, outer edge of top hopper into contact with said refractory lining and acts to direct dislodged material into said top hopper. Where the internal diameter of said large industrial vessel is larger than the diameter of said work platform, said top hopper is displaced outwardly on said rails and said bearings to bring apron 32 into contact with said refractory lining. In the preferred embodiment, said displacement is effected by means of a small hydraulic ram (not shown). In alternative embodiments, said displacement is effected by any suitable simple mechanical means. During said outward displacement of said top hopper, telescopic duct 54, 55 is extended and flexible joint 56 is deflected. Said debris chute is supported more or less collinear with the axis of said work platform on a suitable hanger (not shown) connecting support collar 79 to a swivel bearing on the central, lower surface of said carrier or the lower end of strut 69. m the preferred embodiment, a protective shield (depicted as 40 in Figure 2) is provided below said work platform in the present embodiment. The weight of said debris chute suspended more or less collinear with said work platform acts to stabilise said work platform. Where said top hopper is incorporated into said work platform, attachment means 53 are provided to each side of it and the lower ends of short suspension rods (not shown) are fixed to said attachment means and the upper ends fixed to a strong spreader bar (not shown) positioned a suitable distance above said top hopper so as to not interfere with or obstruct the working of said airleg-type rock drill. A short suspension rod (not shown) connects said strong spreader bar to spreader frame 11 above, thereby supporting that part of said work platform around said top hopper.

Wherever possible, components of said work platform assembly and associated equipment are made from a suitable durable and rigid polymer material or light alloy material, a lower weight facilitating transport, lifting, positioning and assembly of said work platform from

said components. The arrangement described is readily deployed into the interior space of a said large industrial vessel through an opening of restricted size. Following initial deployment of said supporting column and said carrier unit into said interior space, said hydraulic unit is powered and said steady arms deployed to their radial positions and extended to stabilise the position of said assembly. To facilitate initial manipulation of said supporting column and said carrier unit, a rigid strut (not shown) positioned more or less coUinear with said supporting column is optionally fixed to attachment plate 78. Anchor points (not shown) for the connection of safety harnesses are provided on said rigid strut. Said supporting column and said carrier unit are optionally supported within the interior space of said large industrial vessel on temporary struts or cables until said hoist 5, cable 4, spreader frame 11, swivel bearing 9, and suspension rods 10, 12 (as described in relation to Figures 1 and 2) or their equivalents are installed. Supporting panels 50 and supported panels 63 are then installed, said safety fence erected and said top hopper displaced outwardly to bring said apron into contact with said refractory lining. Said airleg-type rock drill is then installed and connected to its necessary services and all supporting equipment loaded into said work platform. With said debris chute assembled, said work platform assembly is ready for operation. Work on said refractory lining is commenced at the bottom of said large industrial vessel and sections of said debris chute added as said work platform is raised.

With reference to Figures 7 and 8, where thicker said refractory lining material or material which retains its structural integrity is to be removed, this is optionally performed using multiple small charges of a suitable explosive material inserted into bore holes made in said material using said airleg-type rock drill. The use of both deflagrating explosives and high explosive in the fracturing of crystalline solids is well known in the art. Obviously, small charges of any suitable explosive material may be employed to fracture said refractory lining material, ranging from slow- burning, deflagrating explosive material through intermediate explosive

materials to rapid detonation high explosive material. Depending upon the thickness and characteristics of said refractory lining material, said explosive material may be deflagrating explosive material or high explosive material. In a first embodiment, said deflagrating explosive material takes the form of cartridges 80 with a diameter of 28 or 34 millimetres diameter, from 50 to 80 millimetres long, containing from 20 to 40 grammes of explosive material. Typically, said cartridges having a diameter of 28 millimetres and containing from 20 to 30 grammes of explosive material are ignited in bore holes 81 of 32 millimetres diameter to fracture refractory lining material 29 of a thickness of up to 100 millimetres. To fracture said refractory lining material of a thickness of up to 300 millimetres, said cartridges of having a diameter of 34 millimetres and containing up to 40 grammes of explosive material are ignited in said bore holes of 41 millimetre diameter. In the preferred embodiment, said cartridges incorporate an electric match (not shown) and are ignited electrically. Said cartridges are not specifically tamped, but each is simply secured in place in said bore holes prior to ignition by one or more suitable wooden wedges 82, 83 set with a wooden mallet (not shown). Said wooden wedges are provided with grooves 84 to permit ingress of conductors 85 connecting said electric matches of said cartridges to a suitable electric exploder (not shown). Where said cartridges are made with tapered outer ends (not shown), each is secured in place in a said bore hole with a single said wooden wedge. Where said cartridges are made with square outer ends (as depicted in Figure 8), each is secured in place in a said bore hole with a mated pair of wooden wedges 82, 83. In practice, said wedges are positioned to abut the outer ends of said cartridges, not with a gap as depicted in Figure 8 for the purpose of showing the entry of said conductors into said cartridges. In a second embodiment, said high explosive takes the form of cartridges 80 filled with an explosive material such as Powergel Magnum™ manufactured by Orica Mining Services. Said cartridges have a diameter of 28 millimetres and contain from 10 to 50 grammes of explosive material. Typically, a 10 gramme cartridge is

used to fracture refractory lining material having a thickness of approximately 100 millimetres. A 30 gramme cartridge is used to break out relatively soft or partially fractured refractory lining material having a thickness of approximately 300 millimetres. A 50 gramme cartridge is used to break out hard refractory lining material having a thickness of approximately 300 millimetres. Where high explosive is employed to break out a zone of refractory material, one or more cartridges are preferably simultaneously detonated in a central location, followed by one or more arrays of circumferentially situated cartridges. The nearest said cartridge array to said central location is detonated after a delay of 25 milliseconds with each successive said array outside it being detonated with a further delay of 25 milliseconds. Said cartridges are detonated by an electric detonator and are secured in place in said bore holes prior to detonation in a manner similar to that employed with deflagrating explosive cartridges, hi normal operations, multiple said bore holes are made and charged, said work platform is raised a suitable distance and said charges ignited or detonated. The said work methods permit said refractory lining material to be rapidly removed while substantially preserving a layer of rare-earth heat insulating cement 86 beneath it. Where said refractory lining material to be removed is in the form of a monolithic mass, a plurality of closely-spaced, parallel bore holes 81 is optionally made in it to compromise its structural integrity and cartridges ignited or detonated in widely-spaced bore holes to fracture and dislodge it. hi such a monolithic mass, and dependent upon the nature of the material, typically said bore holes are made at centre distances of between

50 and 200 millimetres with charges placed in every fourth to every tenth bore hole. In Figure 7, said charged bore holes in a typical arrangement are shown blacked out. hi the preferred embodiment, all said charges are ignited or detonated simultaneously. It is common for deflagrating explosive cartridges to be made to discharge inwardly (towards the bottom of a bore hole) to generate a penetrating cone fracture. Where, in the application of the present invention, a penetrating cone fracture is not

required, transverse obturating pins 87, 88 are installed at the ends of said cartridges. Said obturating pins pass transversely through the thick walls of said cartridges and abut the exterior surfaces of the end closures of said cartridges. They act to momentarily support said cartridge end closures in place during ignition of said deflagrating explosive. This has the effect of confining gas pressure within said cartridges such that the bursting effect generated is exerted substantially normal to the longitudinal axes of said cartridges, thereby being more effective in dislodging said refractory lining material and less likely to damage the structural wall 2 of said large kiln, furnace, cyclone or the like. Similarly, said wooden wedges act to momentarily confine gas pressures within said drill holes during ignition of said deflagrating explosive. Said deflagrating explosive operates by generating a momentary high gas pressure. No concussion is generated and said refractory lining material is removed without damage to the structure of said large industrial vessel.

Said airleg-type rock drill is a powerful tool which provides hole drilling or percussive breaking out of refractory lining material at a much greater rate than the hand tools normally employed in this work. Similarly, the airleg-type rock drill requires only guidance from the operator, minimising the human effort required for the removal process and greatly reducing operator fatigue and the possibility of back injuries and the like. The combined effect is to provide a safer, less fatiguing work process and a substantial reduction in the shutdown time required for the refurbishment of refractory lining material in a plant. Where said refractory lining material is already fractured and does not require shot firing, it is broken out and removed using chisel or diamond-point tools installed in said airleg-type rock drill. Said rock drill incorporates provisions for the rapid changing of tools.

With reference to Figure 9, where a specific area of refractory lining material 29 retaining its structural integrity is to be removed it is delineated by a plurality of bore holes 89. Said bore holes, referred to as pre-split holes, are made with said airleg-type rock drill. Said pre-split

holes extend substantially through the depth of said refractory lining material and their spacing is dependent upon the thickness and hardness of said lining material. Typically, in said lining material of a thickness between 100 and 300mm, 41mm diameter said pre-split holes are made at an approximate centre spacing of 70mm. A plurality of charge holes 90 (depicted blacked out) is drilled in said refractory lining material within the area delineated by said pre-split holes at an approximate distance from said pre-split holes of 15 to 40 per cent of the total width of said area. The number of said charge holes is dependent upon the thickness and hardness of said lining material but, in the preferred embodiment, falls in the approximate range of one charge hole for each four to eight pre-split holes. Suitable charges of explosive material are simultaneously ignited or detonated in said charge holes, the fracture so generated working through to said pre-split holes, hi this way, said delineated mass of said refractory lining material is broken out cleanly with no tendency to over-break.

In an alternative embodiment (not shown), greater thicknesses of said refractory lining are broken out by drilling suitable one or more suitable bore holes into it using said airleg-type rock drill, inserting into said detonation hole in sealing co-operation with it the barrel of a discharge device and discharging near the muzzle of said barrel of said discharge device a suitable explosive charge. The rise in gas pressure hi said bore hole generated by a deflagrating explosive charge effectively causes a penetrating cone fracture which breaks out a localised mass of refractory lining material around said hole. The shock wave generated by a high explosive charge propagates through and fractures a greater area of said refractory lining material around said hole. The use of such discharge devices is well known in the art and examples are those taught by Watson in US 5,474,364, McCarthy in US 5,803,551 and Watson in US 6,339,992. hi the preferred embodiment, anchor points are provided for the attachment of safety harnesses at all appropriate points on said head frame and said work platform to secure operators during assembly and working.

Also in the preferred embodiment, a shield (not shown) of suitable material is erected over said work platform to protect operators from falling material. Said shield takes the form of light panels of a suitable high-impact material fixed to said spreader frame and positioned obliquely so as to deflect falling material outwardly towards said refractory lining material.

In the preferred embodiment, said airleg type rock drill is provided with suitable stops (not shown) which restrict the radial extension of its said tools, thereby preventing contact with and injury of said structure of said large kiln, furnace, cyclone or the like. Before commencement of work and with said shoes of said steady arms in contact with the inner surface of said refractory lining material, measurements are taken to permit said stops to be accurately set.

Following removal of the deteriorated refractory lining, said airleg- type rock drill and its pedestal work are optionally removed from said work platform and said platform deployed in the manner described by personnel reinstating said refractory lining with sound material. Alternatively, said work platform is removed to other employment and replaced by another to be used by said reinstating personnel, hi this way, the work proceeds rapidly in accordance with a planned schedule without the need for scaffolding and with the participation of only a minimal number of personnel. Obviously the present invention may be readily adapted for working inside any tall or elevated and enclosed structure, including kilns, chimneys, reactor vessels, furnaces, cyclones and the like.