Cleaning apparatus for heat transfer surfaces found in applications such as, for example, furnaces and boilers, are well known. Such apparatus provides jets of pressurised cleaning medium, directed through nozzles, which impinge on these heat transfer surfaces to remove coatings of contaminants found in the heating gas, which have built up on the surfaces. This coating forms a barrier that reduces the heat transfer performance of the application in question.

The cleaning apparatus is used to remove this barrier layer to restore the heat transfer efficiency. In order to achieve this, the cleaning medium is directed onto this barrier as a pressurised fluid to ensure such contaminants adhering to the heat transfer surfaces are dislodged. The cleaning medium is generally steam, air or pressurised fluid (water).

Such a cleaning apparatus is shown in European patent application EP-A- 0667949 in which a cleaning medium is delivered under pressure to remove blockages from heat exchange elements within a heating application. The heat exchange elements comprise plates carried on a rotating frame within an enclosed space. The nozzles are carried on lance which moves forwards and backwards along its axis in a manner which, coupled with the rotation of the heat exchange apparatus, will achieve full coverage whilst also trying to remove any build up of depositions. This coverage is achieved by linear movement of the nozzles in a direction.

This backwards and forwards motion of the lance and nozzles, is often accompanied by rotation of the lance tube so that the jets are directed at a range of angles. Rotation is common in boiler applications but not air heaters, for which the device of EP-A-0667949 was developed. That device has a dual-medium facility, in which separate nozzles are provided for high-pressure and low-pressure cleaning jets.

Furthermore, the high-pressure nozzles are located behind and co-axial with the low- pressure jets, to direct the high pressure jets through the same nozzle apertures as the low-pressure medium. This has important advantages in that the lance can be retracted fully from a hostile chemical environment when not in operation.

This known arrangement, and known high-pressure or dual medium arrangements generally, are not adapted for rotation about their axis. Providing rotation causes problems with such devices due to the design of the high-pressure supply. High- pressure seals, which permit rotation, are difficult to maintain in such inaccessible locations as the interior of a cleaning lance. The supply tube in EP-A-0667949 is a flexible hose external to the lance that is only connected at an inlet point of the lance tube rather than as an integral part of the tube. Rotation of the lance tube would inevitably complicate the design of the supply tube which already requires careful design of its travel arrangement, and would compromise the reliability of the entire apparatus.

This inability to rotate severely restricts the commercial applicability of this device and it is one object of the invention to permit rotation of the lance in a cleaning device adapted for high-pressure and/or dual-medium operation.

It is an object of the invention to improve upon existing cleaning devices in terms of cost of manufacture, maintenance requirements, space, reliability or any combination of these, whether or not rotation is desired.

The invention in a first aspect provides a cleaning device comprising an elongate lance body, the lance body carrying at least one first nozzle at a point along its length for the release of at least a first pressurised cleaning fluid within an enclosed working space, the lance body being supported outside said space and driven so as to retract the lance along its axis at least partially from the working space, the lance body internally housing a first moving conduit for said fluid, said first moving conduit communicating with a first fixed conduit for the supply of the first cleaning fluid to said

nozzles, wherein the first fixed conduit and first moving conduit engage one another telescopically, one entering the other at a first telescopic joint incorporating a first seal.

The first moving conduit may in particular be arranged to enter the first fixed conduit at said first telescopic joint and be surrounded by the first fixed conduit as the lance retracts. The first seal may be fixed to the first fixed conduit towards its end nearer the working space. The lance body may in turn surround the first fixed conduit as the latter retracts.

The lance body may further form or contain a second moving conduit, engaging telescopically with a second fixed conduit, the lance body carrying at least one second nozzle at a point along its length for the release of a second cleaning fluid supplied via the second fixed and moving conduits.

The second moving conduit may be arranged to surround the second fixed conduit as the lance body retracts. A second seal arranged on and moving with the second moving conduit may seal the second fixed and moving conduits against escape of the second cleaning fluid.

The second fixed conduit may be provided with apertures toward its end nearest the working space, said apertures permitting flow of the second cleaning fluid radially from the second fixed conduit into the second moving conduit. This is of particular merit in embodiments where the end of the second fixed conduit is for some reason at least partially obstructed. In a dual medium embodiment, for example, the end of the second fixed conduit may be partially obstructed by means supporting the first telescopic joint that carries the first cleaning fluid.

The apertures, which may for example comprise slots extending partially along the second fixed conduit from its end nearest the working space, may further provide means for preventing undesired rotation of part of said first telescopic joint. This is particularly advantageous in combination with the feature mentioned below, whereby

rotation of one or other of the first and second fixed conduits provides a means of adjusting said first seal.

The first fixed and moving conduits may be arranged within the diameters of the second fixed and moving conduits.

The first and second fixed and moving conduits may be formed and sealed from one another such that the first cleaning fluid will be retained at a substantially higher pressure than the second cleaning fluid. The above arrangements in which the first telescopic joint is stationary, and of relatively small diameter assist the provision of a high-pressure seal. Moreover, leakage of the high-pressure fluid in such arrangements is only into the low-pressure conduits, and does not lead to escape of fluid from the cleaning device.

The second moving conduit may be formed directly by the lance body.

The first nozzle (s) may be arranged co-axially with and behind the second nozzle (s) to direct the first fluid through the second nozzle. This brings advantages as explained in EP-A-0667949 mentioned above.

The first seal may be constructed to permit adjustment of sealing force by movement of one of said conduits. By this means, a high-pressure seal can be maintained over long periods of wear, although the joint itself is inaccessible within the lance and casing. This is particularly an issue where the first fixed and moving conduits are surrounded by second fixed and moving conduits in a dual-medium embodiment. This feature is equally useful in single-medium embodiments, however.

In one such embodiment, the first seal is adjusted by means of screw threaded components, one threaded component fixed to the first fixed conduit and restrained against rotation, the other fixed to the second fixed conduit, the threaded components being rotated relative to one another by relative rotation of the first and second fixed conduits. In a preferred embodiment, a first threaded component is carried by the first

fixed conduit and a second threaded component is carried by, or at least constrained against rotation relative to, a second fixed conduit which surrounds the first fixed conduit.

The first fixed conduit may be provided with manual or powered actuating means, such as a simple handle, to permit said adjustment of the sealing gland.

Alternatively a gripping tool may be required. Said adjustment may require loosening or removal of other joints or coupling. Provided these are relatively accessible, in particular outside the working space and outside the lance body, very little inconvenience results.

The cleaning device outside the working space may be housed within an elongate casing into which the lance body retracts, the first fixed conduit projecting out of the casing at its end furthest from the working space to a first supply coupling for said first cleaning fluid.

The first fixed conduit may project from within the second fixed conduit where provided. The second fixed conduit may also project from the end of the casing to a second supply coupling for said second cleaning fluid.

The second supply coupling may be arranged off-axis to permit passage of the first fixed conduit in a straight line. The second supply coupling may be connected to the second fixed conduit via an adapter section providing said offset, the connections at each end of the adapter section being complementary so as to permit a common design of supply coupling and second fixed conduit to be used with and without said adapter.

In any of the above arrangements, the lance body may be arranged to rotate about its axis during operation, to vary the attitude of the nozzle (s). This is in contrast to prior arrangements in which a high-pressure or dual-medium arrangement is incompatible with a rotating lance. The lance may be independently rotatable, or arranged to rotate in a helical manner synchronously with its axial movement. The

rotation may be caused at least in part by directing the nozzles for cleaning medium along a path offset from the lance axis.

The invention in a second aspect provides a cleaning device comprising an elongate cylindrical lance body, the lance body carrying at least one first nozzle at a point along its length for the release of at least a first pressurised cleaning fluid within an enclosed working space, the lance body being supported outside said space and driven so as to retract the lance along its axis at least partially from the working space, the lance body internally housing a conduit for said fluid, wherein said first nozzle is housed within a nozzle section formed separately from the cylindrical lance body and having substantially the same outer cross section as the lance body.

Providing a separately formed nozzle section simplifies assembly of the device, and provides for an adaptable and modular product range. Since the nozzle section has an outer cross-section similar to the lance body, it does not interfere with retraction of the entire lance through the wall of the working space.

The cylindrical lance body will typically be of circular cross-section, but other cylindrical shapes are possible in principle.

The nozzle section may incorporate a passage open at both ends to permit said fluid beyond the individual nozzle section. The cleaning device may comprise an end cap mounted onto said nozzle section to terminate said passage. The cleaning device may incorporate a second nozzle section directly or indirectly in series with the first, fluid being supplied to the second nozzle section via the passage in the first nozzle section. The first and second nozzle sections may be oriented differently so as to direct jets of said fluid in different directions.

The nozzle section may comprise at least one shell piece and an internal nozzle block formed separately. The internal nozzle block may house a conduit for said fluid and at least one nozzle for discharging a jet of said fluid into the working space, said nozzle being set behind and coaxially with an aperture in said shell piece. The aperture

in said shell piece may act as a nozzle for a second cleaning medium which, in use, is pressurised less than the first cleaning fluid.

In a preferred embodiment, the or each nozzle section comprises a pair of shell pieces and a nozzle block, each formed as a casting.

The nozzle block may comprise apertures defining a plurality of nozzle positions selectively occupied by nozzle inserts or blocking inserts, according to the number of nozzles desired in a given application.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of example only, by reference to the accompanying drawings, in which: Fig. 1 is a schematic diagram of the main elements of a dual-medium cleaning device in operation, as described in EP-A-0667949; Fig. 2 shows the device of Fig. 1 at a later stage in operation; Fig. 3 is a schematic diagram of a rotating, dual-medium cleaning device in accordance with one embodiment of the present invention; Fig. 4 shows in more detail the general arrangement of a practical embodiment of such a device; Fig. 5 shows in more detail the arrangement of a supply end of the apparatus of Fig. 4; Fig. 6 shows in more detail the arrangement of a telescopic joint incorporating a remotely adjustable sealing gland within the apparatus of Fig. 4;

Fig. 7 shows the modular nozzle arrangement in the device of Fig. 4 along a split section on line B-B of Fig. 8; Fig. 8 shows the split section A-A of Fig. 7; Fig. 9 shows the modular nozzle arrangement of Fig. 7, adapted to provide two sets of nozzles firing in opposite directions; Figure 10 shows in more detail an adjustable gland arrangement for use in place of that of Fig. 6; Figures 11 and 12 show certain alternative nozzle arrangements for use in place of those of Figs. 7-9; Figure 13 is an exploded schematic view of the drive and bearing arrangements for the lance in the embodiments of Figures 4-12; and Figure 14 is an exploded schematic view of the drive and bearing arrangements in an alternative embodiment, having independent rotation and traverse drives.

DETAILED DESCRIPTION OF THE EMBODIMENTS Referring to Figs 1 and 2 of the drawings, there is shown a cleaning device 10 or "sootblower", as described in EP-A-0667949. By this device, a cleaning medium 15 is delivered under pressure to remove blockages from heat exchange elements 60 within a heating application, for example, a rotary air heater 50. The cleaning medium may be water, air or steam, for example. The cleaning device 10 comprises a lance tube 20, a casing 30 and a high pressure cleaning medium supply tube 40. The cleaning medium 15 (H. P. water) is delivered to a lance tube nozzle assembly 45 by means of a stainless steel feed tube within the lance tube (not shown). The lance tube 20 containing the

multi-duty nozzle assembly 45 is contained within the casing 30. There is also a pocket (not shown) welded onto the lance tube 20 near to the outer end, the purpose of which is to allow the H. P. water tube 40 an exit path from the lance tube 20. The tube is supported at its bend by a half-speed pulley wheel (shown in EP-A-0667949), to ensure smooth paying out and retraction of the hose. Low pressure cleaning medium is carried via the lance tube, outside the H. P feed tube mentioned above, itself to exit via L. P. nozzles in the assembly 45. Separate L. P supply arrangements are provided, but not shown for clarity.

Fig. 1 shows the device 10 with the lance tube 20 fully extended within the air heater 50, during a cleaning cycle. The cleaning medium 15 blasts the heat exchange elements 60 within the air heater 50 as it is discharged from the nozzle assembly 45 under pressure. Full coverage of the elements 60 by the nozzle assembly 45 and cleaning medium 15 is achieved by linear movement of the lance tube 20 in a forwards and backwards direction as indicated, while the elements 60 follow a rotary path from heating to cooling sides of the heater 50.

Referring to Fig. 2, the lance tube 20 is shown towards its parked position after completing a cleaning cycle ready to begin again. Where the environment within heater 50 is corrosive, the lance may be designed to retract completely from the operating space. This is facilitated by directing the H. P nozzles co-axially through the L. P nozzles, as described in EP-A-0667949, mentioned above. In operation, a start signal activates a motor (not shown), the lance tube 20 starts to move forward until part of it makes contact with a limit switch at a pre-determined point, sending a signal to actuate the cleaning medium 15. The main carriage continues to move until the reverse limit switch is tripped. This switch reverses the drive motor and the lance tube 20 continues to retract in steps until the limit switch, which activated the cleaning medium 15, is tripped again. After a small delay to allow for lance drainage, the lance tube 20 is fully retracted to the parked position.

In many applications, more efficient cleaning can be obtained by providing for rotation of the lance tube 20 while it advances and retracts. Rotation is common in

boiler applications, where a single, low-pressure medium such as air or steam is used, but not in air heaters, requiring high-pressure jets and dual-medium supplies. The known arrangement, which in itself is complicated and expensive to manufacture for reliability, does not readily adapt to rotation of the lance, as it would require the H. P. hose to wrap around the lance.

A cleaning device will be described with reference to Figs 3 to 7, which provides for H. P and L. P. cleaning media, permits rotation, and permits a simpler construction and ease of maintenance greater than in the known device. In the embodiment of Figs 3 to 7 to be described, parts with reference numbers 10, 20 etc. correspond to parts 10,20, etc. in the description of Figs 1 and 2.

Fig. 3 shows schematically the arrangement of such a cleaning device 10. The essence of this device 10 is to replace the single nozzle arrangement of the first device as shown in Figs. 1 and 2 with a co-axial nozzle as this will enable a high-pressure water cleaning supply for cleaning the boiler tubes to be used. Solid arrows indicate the flow of high pressure medium, while broken line arrows indicate the alternative, low pressure medium. The drive means for the lance body 20 (Fig. 4), in addition to advancing the lance tube 20, also causes rotation of the lance 20. Angled rollers 55 are provided for this purpose, and support the lance body 20 as it enters the boiler space.

HP medium is delivered via a first fixed conduit 80, entering along the axis of the lance from the rear. A second fixed conduit 90 surrounds the first conduit 80 and is for the supply of LP medium. An elbow piece 100 is connected the conduit 90 with an inlet valve 110 for this purpose. A sealing gland 120 surrounds conduit 80 to isolate the LP medium from the environment and from the interior of conduit 90. The source of the HP fluid is a hose connected to the end of conduit 80 of to the left of the figure. The lance body 20 internally houses a further conduit 170 communicating with the fixed conduit 80 for the supply of the HP medium to HP nozzles 230, and moving with the lance body 20 as it extends and retracts and rotates on its axis. Conduits 80 and 170 engage one another telescopically, one entering the other at a telescopic joint incorporating an adjustable sealing gland 180.

The lance body 20 itself constitutes a second moving conduit for supply of LP medium to nozzles at its far end. This engages telescopically with conduit 90, at a second sliding and rotating seal 185 arranged on and moving with the lance body. The fixed LP conduit 90 is provided with apertures 190 toward its end nearest the boiler space, said apertures permitting flow of the second cleaning fluid radially from the second fixed conduit into the second moving conduit, as shown by the broken line arrows. This reduces the impedance of the flow which would other wise be associated with the sealing gland 180.

Still referring to Fig. 3, the gland 180 can be tightened to take up wear by relative rotation of the two fixed conduits 80 and 90. The mounting of conduit 90 is loosened at its rear end, to permit relative rotation of the threaded gland pieces deep inside the lance. For example the gland 120 may be loosened and the HP inlet 80 rotated while conduit 90, and hence the gland 180 mounting remain fixed. This feature, and alternatives that may be considered for achieving the same function, will be described in more detail later with reference to Figure 10.

Fig. 4 shows in more detail the general arrangement of an actual implementation of the device 10 of Fig. 3, (a) in part cut-away elevation and (b) in part cut-away plan view. Again the same reference signs are used for parts corresponding to those in Figures 1-3. More detail of nozzle arrangements is given below, with reference to Figures 7,8, 9 and 10. Within the fixed housing 30 can be seen the travelling carriage 25 and drive chain 35 by which the lance is advanced and retracted. The lance 20 at its cleaning end has two side-by-side sets of nozzles 45 arranged to face oppositely.

References 25', 35'and 45'show these parts in the fully extended position. The drive motor 70 and associated gearbox are mounted outside the main housing, for convenience. Figures 13 and 14, described later, illustrate in yet further detail the bearing and drive arrangements for the lance in two alternative forms.

Fig. 5 shows in more detail the supply (outer) end of the apparatus of Fig. 4. A high-pressure stationary supply tube 80 is located co-axially within the present LP

supply feed tube 90 and in respect of means 110 for supplying the cleaning medium 15 at the outer end. A fabricated elbow branch piece 100 is connected at one end to the feed tube 90 (for the LP cleaning medium) for LP feed thereto with the high-pressure tube 80 extending rearwardly from this feed tube 90 and a gland device 120 provided between the two tubes 80,90. A valve 110 for low pressure cleaning medium is located at the other end of the elbow 100.

The gland 120 employs a threaded boss 130 welded to the outer end of the LP supply tube 90, which is stationary, with a gland nut 140 threaded to the neck of the boss 130. Packing 150 of a graphite form is utilised and a tapering wedge element 160 is present in the gland 120. As the rotation of the gland nut 140 causes it to move axially along the threaded portion of the boss 130, so it continues until it comes into contact with the tapered wedge 160. Continued rotation of the gland nut is then translated into axial movement of the tapered wedge 160 along the tube 80. However, such axial movement is restricted as the threaded boss 130 is welded to the tube 90 and will therefore limit the amount of axial movement available inside the boss. Any such axial movement of the tapered wedge 160 will force the threaded boss to open out radially, more so at its threaded end, as the tapered wedge prises open the boss. By forcing the threaded portion of the boss 130 radially outwards into the gland nut 140, a tighter threaded engagement with the gland nut 140 is created. This threaded engagement also exerts a pressure on the tapered wedge 160, maintaining its position between the feed tube 80 and the threaded boss 130, to complement the sealing function of the gland 120. The HP tube 80 is also stationary and a suitable valve (not shown) will deliver the HP cleaning medium (water) to this tube 80.

In order to deliver the cleaning medium to the high-pressure nozzles, a HP tube is needed which is capable of rotation. This would have to be housed within the stationary HP tube 80 for purposes of rotation. Furthermore, a gland arrangement is now required to seal this arrangement of HP tubes 80, 170.

Fig. 6 shows this gland arrangement wherein the rotary HP tube 170 is provided within the lance 1 for feeding the cleaning medium to the high-pressure nozzles. In this gland arrangement 180, the rotary HP feed tube 170 is arranged co-axially with the stationary HP feed tube 80 part of the HP supply. Views (a) and (b) show the telescopic joint between conduits 80 and 170 mounted within the end of LP conduit 90, with lance body 20 removed for clarity. Views (c) and (d) show the relationship between conduit 90 and the lance body 20, with the HP parts removed for clarity.

Side by side with the gland, there are provided axial slots 190 on the LP feed tube 90. Consequently when the low pressure cleaning medium arrives at the gland area, it will pass outwardly through these slots so as to flow via the LP tube 90 and the lance 1 and then axially into the outer lance portion for onward direction to the LP nozzles. This arrangement avoids any undesirable throttling of the cleaning medium which may result from a reduction in the area of the passage in the annular space between the stationary HP feed tube 80 and the LP feed tube 90.

The gland 180 at the HP tube portion employs a nut 200 welded to the stationery tube portion 80 with a threaded receiving member 210 connected to the LP feed tube 90. Again, a graphite sealing element 220 is employed in the gland. This enables the fixed LP and HP tubes 80,90 to be used as a means of remotely tightening the gland 180. In particular, this enables the gland 180 to be tightened by an external operation at the outer end of the cleaner.

Figs. 7 and 8 show the arrangement of the nozzle portion 230 of the cleaning device. This nozzle portion 230 comprises an outer nozzle 250 assembled from two split housing portions 250a and 250b. This outer nozzle 250 is welded onto the end of the lance 1. The outer nozzle 250 is generally circular in shape and has a similar outer diameter to that of the lance 1. The nozzle 250 is split in a horizontal plane generally along the centre line of the lance as shown in Fig. 8. The upper half of the nozzle 250a is provided with a profiled internal recess portion 320, generally U-shaped in profile.

This recess 320 occupies the central portion of the upper half 250a and is aligned centrally with the centre line of this upper half 250a. This upper half is also provided with a stepped feature 255 which has a mating surface on the lower half 250b and is

dimensioned to provide a location surface used when assembling both halves 250a and 250b. Housed within this recess 320 is a nozzle casting 260 having a mating surface 325 for locating within the upper half 250a. The casting 260 is then secured to the upper half 250a of the split housing using a socket head capscrew 300. The nozzle casting 260 is substantially hollow and is provided with a through bore 330 aligned concentrically with a counterbore 340 within which the HP water feed tube 170 locates.

This tube 170 is welded to the nozzle casting 260 once located. The throughbore 330 is sized to match that throughbore of the HP water feed tube 170. The throughbore 330 opens into a substantially rectangular chamber 350 which serves as a means of fluid communication between the HP feed tube 170 and the high pressure nozzles 240 located at an angle of approximately 90° to the axis of the HP feed tube 170.

The nozzles 240 are located within three equispaced threaded apertures at the bottom of the chamber 350 in the casing 260. These apertures are provided with a tapered thread. The nozzles 240 have a matching tapered thread 245 for fastening into the casing 260 and are also provided with a flange 265 having spanner flats. The flange 265 abuts the bottom face of the casing 260 to lock the nozzle fully in position. The nozzles 240 project from the nozzle casting 260 into a recessed portion of the lower half 250b of the split housing 250 which is also substantially U-shaped.

This lower half contains a jet nozzle block 370 in the form of a spigot insert which is provided with the outlet nozzles 310. These nozzles 310 have a profile which narrows from the inlet until a curved neck is formed at the narrowest point 315. From this point, the profile of the nozzles gradually tapers outwardly until it reaches its widest point where it blends with the outer diameter of the nozzle block 370. The high- pressure nozzles 240 are centrally aligned with the outlet nozzles 310. Both parts of the split housing are assembled by locating the mating faces 255 provided on both halves 250a and 250b. They are then secured using socket head capscrews 270.

A generally circular end cover 280 with an outer diameter similar to that of the outer nozzle 250 is provided with means for locating within a counterbore provided at the end of the assembled outer nozzle 250 furthest from the lance 1. The end cover 280

is secured in two ways. Firstly, it is secured to the lower half 250b of the outer nozzle 250 using a socket head capscrew 290 and, secondly, it is secured to the upper half 250a of the outer nozzle and the nozzle casting 260 using a socket head capscrew 300. This end cover 280 prevents the unwanted escape of any pressurised cleaning medium from the nozzle arrangement shown.

The nozzles 240 may be used in different configurations dependent on the number of nozzles required. Additionally, the holes 310 in the split housing 250 may be plugged to give different configurations also. Alternatively, it is possible to achieve any desired combination by removing any given nozzle 240 and blocking any given nozzle outlet 310. Furthermore, the nozzles may be configured in a manner that enables the pressurised cleaning medium to be delivered in opposite directions without adjusting the position of the lance.

Fig. 9 shows such a configuration, where the modular nozzle arrangement shown in Fig. 7 has been adapted to provide two sets of nozzles. The split housing of both outer nozzles 380,390 are welded to each other and are of a generally similar outer diameter to that of the lance 1. The housing 380 is, in turn, welded onto the end of the lance 1. The outer nozzle 380 is provided with a jet nozzle block 400 that is similar to the jet nozzle block 370 shown in Fig. 7. Three equispaced nozzles 410 are provided in this block, but up to six can be provided in the same casting, in two rows or three. The centre line of the nozzles 410 is offset from the centre line of the housing 380 by a specified amount. Again, as with the nozzles 370 shown in Fig. 7, the nozzles 410 are generally of a tapered form extending from the inlet to the outlet points of the nozzle. However, the nozzles have a profiled neck 420 just beyond the nozzle inlet, which form the narrowest point of the nozzle. At this point 420, the taper of the nozzle gradually widens until it reaches its widest point where it meets the outer diameter of the jet nozzle block 400.

The housing 390 is welded to the end of housing 380 furthest from the lance 1.

The nozzle block 410 provided in this housing is shown in Fig. 9 at a position and orientation 180° opposite the nozzle block 400 in the housing 380. This enables the

pressurised cleaning medium to be delivered in from two opposite directions, as indicated schematically in Fig. 4. Additionally, the housing 390 has features similar to those described in Fig. 7 for securing an end cover 430 to the housing 390 at a point furthest from the lance 1. However, unlike the arrangement shown in Fig. 7, there is no nozzle casting 260 present which means the end cover 430 has to be secured to the upper half of the housing 390 using a socket head capscrew 450, a plain washer 460 and a hex nut 470 instead. As previously described for the arrangement of Fig. 7, the end cover 430 is secured to the lower half of the housing 390 using a socket head capscrew 440. Button covers 480 placed in counterbores provided in the end cover 430 protect both socket head capscrews 450 and 480. As with the arrangement of Fig. 7, both halves of the split housings 380 and 390 are secured together using socket head capscrews 490 offset from the centre line of the housings.

Although the nozzle arrangement shown in Fig. 9 has no internal nozzle casting 260 for housing a further set of nozzles 240, co-axial with the nozzles 410, the arrangement can readily be adapted to provide dual-medium operation by the provision of internal nozzles and conduits, similar to those included in Figures 3 and 7. such an arrangement is shown, for example, in the general arrangement of Fig. 4.

Various modifications are possible to the embodiments described above, as will now be described.

Referring again to Figures 4 and 5, an alternative embodiment has the"elbow" piece 100 moved inside the housing 30 for the apparatus. Depending on the product variations required, this may be more convenient and/or provide a neater appearance and better protection for the components of the cleaning device. The flange for mounting of the valve 110 (548 Fig. 5) can for example be integrated with the back plate 549 of the housing.

Figure 10 shows in more detail an alternative gland arrangement 180'. In addition to the remotely-adjustable threaded gland 200'/220', there is provided a second gland closure 500 at the outer side of the gland arrangement, with packing 510. This

gland provides an additional barrier to the high pressure fluid, although it is not made adjustable in this case. Packing 220'and 510 may be rings of graphite or other suitable material.

A removable coupling 520 is also shown in this Figure, which may be included in applications where different nozzle arrangements may be desired to be substituted in the field. In addition to the dual-gland arrangement, Figure 10 also shows in more detail the adjustment mechanism for gland 200'/210'. In particular, during adjustment, the inner high pressure feed tube 80 remains stationary while the outer, low pressure feed tube 90 is rotated. This rotates the end cap 530, and hence the inner portion 210' of the adjustable gland, in order to increase compression of the packing 220'. Keying bolts 540 are provided in this case with dedicated slots 550 in the end of the outer tube 90, rather than locating merely in the air slots 190 (not shown in Figure 10). Slots 550 may be flared, to assist assembly.

Referring to the detail in Figure 5 with the housing open, the joint 550 can be loosened by loosening nuts 552, to permit tube 90 to be rotated manually or by means of a suitable gripping wrench or keys (not shown) provided on the outside of the tube.

In an alternative embodiment, it can be envisaged that LP tube 90 might remain stationary while the innermost, HP tube 80 is rotated to tighten the gland. This has the advantage that it might be performed without opening the housing, but involves disturbing the high pressure fluid connections, which are more susceptible to damage and leaks. Providing design considerations such as are taken into account, however, many variations are possible, for using the conduits themselves to provide for remote adjustment of the telescoping seal deep within the lance body. Limited rotational freedom would suffice, if a ratchet mechanism were included at the gland, for example.

Finally, Figures 11 and 12 show alternative nozzle assemblies to form the end of the lance tube. In each Figure 11 and 12, part (a) shows the nozzles in axially cross section, while part (b) shows a canted radial cross section on line BB while (c) shows an end view on arrow C. These are not based on the castings of Figures 7-9, but still the

nozzle assembly, over its length, defines the lance tube body. In particular, the nozzle assemblies of Figures 11 and 12 are constructed within a piece of tube 600, having a diameter corresponding to that of lance tube 1. Instead of being welded to the main body of the lance tube 1, tube 600 is fixed by a series of radial bolts (not shown) through holes 602, and a circular connecting collar 604, welded or similarly bolted to the end of the main lance tube body 20. In this arrangement, in addition to nozzles firing in opposite directions, it will be seen that the angle of direction is a few degrees off the normal to the tube axis. Different sizes of high pressure nozzles 608 and 610 are provided in these examples. In Figure 11 the high pressure fluid passes co-axially through the low pressure fluid nozzles 612. In Figure 12, separate nozzles 614 are provided for the high pressure fluid.

Figure 13 shows in exploded schematic form the principal elements of the drive and bearing arrangements for the lance tube 20 in the cleaning device 10 of Figures 4- 12. Elements already mentioned in the previous description include the lance tube body 20, the traverse drive chain 35, nozzles 45, inclined rollers 55 and drive motor 70.

Drive motor 70 is arranged to drive a traverse gear box 702, which in turn drives a first cross shaft 704. Either side of the lance tube axis, chain pinions 706 and 708 are fixed to rotate with the shaft 704 under power of the motor 70. Traverse drive chain 35 extends between the first driven pinion wheel 706 and a freely rotating pinion wheel 710, which is pulled longitudinally to act as a tensioner for the traverse chain. Lance tube body 20 is attached to a main shaft 712 by means of a bolted flange connection 714. A second drive chain 716 is provided for controlling rotation of the lance, and extends between the second pinion 708 and a further tensioner 718. A second cross shaft carrying a spiral gear 720 is geared to main shaft 712 for causing rotation of lance tube 20 about its longitudinal access. This cross shaft is driven by a further chain pinion 722. The main shaft 712 and spiral gear 720 form part of a traversing gear box which is fixed to the traverse drive chain 35 at traverse chain gear box fixing point 724.

In operation of motor 70 causes rotation of the first cross shaft 704, and in turn drives chains 35 and 716 in unison. Chain 35, via fixing point 724 on its upper span drives the lance tube body forward or backward along its axis, according the direction

of the motor. At the same time, the lower span of station drive chain 716, travelling in the opposite direction, drives pinion 722. This is turn causes rotation of the spiral gear 720, and hence rotation of the main shaft 712 and the entire lance body 20 about its axis. The result is to impart the desired helical motion indicated at 726, the angle of this helix being matched to the angle of inclination of rollers 55. The ratios of gearing between the various drive parts just described of course are selected to define the helix angle.

Figure 14 shows for the most part the same elements as Figure 13, and these will not be described again in detail. There are some differences, however, which permit the lance tube 20 in this embodiment to describe a helix of variable pitch, and even to rotate whilst not traversing, or to traverse without rotating. This allows more flexibility of the cleaning operations, and greater efficiency. For example, in a circular space, it may be appropriate for the nozzles to traverse more slowly with increasing distance from the centre of the machine, whilst rotating at the same speed about the lance axis.

To allow the helix 726 to be infinitely variable in this way, the arrangement of Figure 14 differs from that of Figure 13 in the following details. As a first point, the inclined rollers 55 have been replaced by ball bearings 730, to support the weight of the lance body whilst allowing it to move freely both longitudinally and rotationally.

Passive tensioner wheel 718 is replaced by pinion wheel 732 driven by a further motor and gear box arrangement 734 to drive the second chain 716. Fixed pinion wheel 708 is replaced by a free running rotary chain pinion wheel 736, carrie d on cross shaft 704, but not driven by it.

In operation, as will be readily appreciated, motor 70 and cross shaft 704 now control the traverse drive chain 35 only, to control the longitudinal motion of the lance body 20. Quite independently, the motor and rotary drive gear box 734 controlled the motion of the second chain 716, and hence the rotation of spiral gear 720, and the rotational component of the motion of the lance tube 20. The motor can be driven by an inventor circuit, to allow variable speed.

In a yet further embodiment, in illustrated, the chain drives may be replaced by a rack-and-pinion arrangement. A drive motor and gearbox in this case may be mounted on the lance carriage, so as to traverse with the lance. A pinion wheel driven by this motor engages a tooted rack which extends the length of the housing. Another shaft driven by the same motor provides the rotary motion. This arrangement has the advantage of cheapness, if fixed helix operation is sufficient. Again, a clutch arrangement, to allow independent control of rotation and traverse motion.

Of course, any combination of drive types, be they chain, rack and pinion or whatever, may be envisaged to suit a given application.

Further modifications are of course possible within the spirit and scope of the invention in its various aspects. The examples described are given as examples only, and are not intended to limit the scope of the invention in any way.