Fastening Apparatus for a Cleaning Device Based on Introducing High-Amplitude Pressure Waves

A fastening device for a cleaning device by introducing pressure waves through a hollow nozzle into a boiler to be cleaned through an opening in the boiler wall has a housing body, which can be fastened to the boiler wall with the aid of a fastening flange on the boiler side, the hollow nozzle being concentric with the opening in the boiler wall and orthogonal to the boiler axis. Damping units are arranged at regular angular intervals around the hollow nozzle in the longitudinal direction thereof and are each fastened with one free end to the boiler-side fastening flange and with the respective other free end to the housing body. When the pressure waves are triggered, the housing body is resiliently retained in the longitudinal direction away from the boiler and brought back into the initial position.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a fastening device for a cleaning device based on the introduction of high-amplitude pressure waves through a hollow cylindrical nozzle into a boiler to be cleaned through an opening in the boiler wall, wherein the housing body of the cleaning device can be fastened to the boiler wall with the aid of a fastening flange on the boiler side, wherein advantageously the longitudinal direction of the hollow cylindrical nozzle is concentric to the opening in the boiler wall and is orthogonal to the boiler axis.

DESCRIPTION OF RELATED ART

A cleaning device and a cleaning method for generating high-amplitude pressure waves, in particular for boiler cleaning, is known from WO 2019/185736. The corresponding device has a discharge opening for the directed discharge of the gas pressure generated in a combustion chamber. This outlet opening is usually a hollow cylinder which is guided through the boiler wall to be cleaned. For the purpose of cleaning, when the boiler is not in operation, the said high-amplitude pressure wave is generated in the device and introduced into the boiler volume.

When the boiler cleaning device is in operation, the explosion thrust triggers a force along the longitudinal axis of the device, which can damage this mounting of the cleaning device used to fix the device to the boiler wall.

To overcome this problem, the hollow cylinder intended for releasing the explosive gases can have a flange to which the said device is attached. The corresponding tensile and shear forces then act on this connection. In addition to the load on the hollow cylinder, which is then itself attached to the boiler wall, a further disadvantage is that this device cannot be easily adjusted to different exhaust gas volumes. The system is usually scaled by using hollow cylinders of different diameters, so that the system then has to be adapted to the correspondingly larger or smaller diameter of the hollow cylinder with corresponding additional flanges.

Most of the time, however, the boiler is in its operational function and the boiler cleaning device is in its idle function. The disadvantage of this is that aggressive gases can flow from the boiler through the hollow cylinder to the drain opening and thus to the piston valve seat. These gases can impair the tightness to such an extent that the rapid pressure build-up, which is advantageous for boiler cleaning, is impaired by a reduction in the quality of the valve seat.

SUMMARY OF THE INVENTION

Based on this prior art, it is an task of the invention to provide a device in which lower forces and torques act on the attachment of the boiler cleaning system to the boiler. It is another aim of the present invention to improve the attachment in such a way that the boiler cleaning system can be easily adapted to different requirements.

This task is solved for a fastening device for a cleaning device according to the invention in that a series of damping units are provided which are arranged at regular angular intervals around the hollow cylindrical nozzle in its longitudinal axis and are each fastened with one free end to the fastening flange on the boiler side and with the other free end to the housing body, so that when the said high-amplitude pressure wave is triggered in the cleaning device, its housing body is resiliently retained in the longitudinal direction away from the boiler and can be returned to the starting position.

At the same time, it may be advantageous that maintenance can be carried out without having to completely dismantle the system. Finally, another aim of the present application is to prevent aggressive gases from flowing from the boiler through the hollow cylinder to the drain opening and thus to the piston valve seat.

Advantageously, each damping unit can have a pneumatically or hydraulically controllable damping cylinder and a piston that can be extended from it, resulting in a retraction unit with which the cleaning device can be retracted, especially if it is suspended above on a trolley so that it can be retracted.

The damping units preferably comprise hydraulic dampers that are rotationally symmetrical around the tube of the cleaning device. The hydraulic dampers of the damping unit can also have two tension/compression springs arranged in a row in the longitudinal direction, which are inserted between the boiler-side fastening flange and a damping plate or between the centre plate and the damping plate, wherein the housing body is rigidly fastened to the centre plate with first longitudinal rods, that the damping plate is rigidly fastened to the boiler-side fastening flange with second longitudinal rods, and wherein additional hydraulic dampers are provided between the damping plate and the centre plate in the longitudinal direction around the hollow cylindrical nozzle.

Advantageously, the two tension/compression springs of each damping unit arranged in a row in the longitudinal direction can then be arranged around one of the second longitudinal rods and supported on the centre plate directly or on bushes facing the tension/compression springs on this centre plate, while the associated second longitudinal rod is guided through an opening in the centre plate. In particular, the springs are preloaded compression springs in the rest position.

In a further advantageous embodiment of the damping units, instead of tension/compression springs, these consist of toroidal or tyre-shaped elastomers arranged in a row, each of which is arranged around one of the second longitudinal rods and is supported on the centre plate directly or on bushes facing the directly adjacent elastomers on this centre plate, while the associated second longitudinal rod is passed through an opening in the centre plate. In particular, the elastomers can be copolyester elastomers. Spacers, in particular metal plates, can be provided as washers between every two elastomers and the second longitudinal rod can be surrounded by a hollow radial guide tube, against which the inner edges (=inner continuous opening of the torus directed inwards towards the longitudinal axis of symmetry) of the elastomers abut, so that these are provided with only a small amount of play around their longitudinal axis.

The mounting flange on the boiler side can be part of a one-piece or composite closure housing that has a boiler wall flange that can be fixed to the boiler at the longitudinal end opposite the mounting flange.

The closure housing can have a guide tube in which the hollow cylindrical nozzle is freely guided so that it can be retracted separately.

Cooling to protect the guide tube and the nozzle can be realised in the fastening device in that the guide tube is double-walled with an internal cavity which is provided in a helical shape from a feed point into the guide tube pointing away from the boiler to the front edge of the guide tube, in that the inner cavity can be supplied with a cooling fluid from a fluid source arranged outside the closure housing and in that the wall or front edge of the guide tube directed towards the boiler wall has openings for an outlet of the cooling fluid. The guide tube thus protects the breakthrough opening of the boiler wall in the event of a pulse event, i.e. a continuous cleaning pulse.

Advantageously, the mounting flange on the boiler side can be moved back and forth relative to the boiler wall flange in the longitudinal direction of the hollow cylindrical nozzle, whereby the guide tube can be at least partially withdrawn from the opening in the boiler wall in a rearward rest position. As a result, boiler gases can only partially attack the guide tube.

To protect the nozzle and to simplify maintenance by separating the cleaning device from the fastening device, a closure flap can be provided in the interior of the closure housing, which consists of two to four closure wings, each of which can be swivelled about a bearing axis arranged tangentially transverse to the longitudinal axis in order to be opened by swivelling against the inner walls of the closure housing when the hollow cylindrical nozzle is pushed forward through the front edge of the nozzle. These flaps are arranged in the longitudinal direction in such a way that an actively cooled guide tube is arranged in front of the flaps and in the longitudinal direction between these and the boiler wall.

The closure wings can be double-walled with an inner cavity, whereby the inner cavity can be supplied with a cooling fluid from a fluid source located outside the closure housing and the wall of the closure wing facing the boiler wall has openings for an outlet for the cooling fluid, so that the closure wing itself can also be protected from the temperature and aggressive media in a boiler.

If a swivelling axis is arranged above the housing body for the fastening device, which is aligned transversely to the longitudinal axis of the hollow cylindrical nozzle of the cleaning device, and on which the housing body is suspended via a pendulum arm, the recoil of the cleaning device can be absorbed in a simple manner, whereby the pendulum movement combines a larger return movement with only a small height deflection.

If the swivel axis is attached to a trolley that can be moved in the longitudinal direction of this hollow cylindrical nozzle on a trolley profile provided above the hollow cylindrical nozzle, the cleaning device can also be easily retracted, which is particularly feasible when using active pneumatic or hydraulic lifting cylinders in the damping units.

Further embodiments are given in the dependent claims.

DESCRIPTION OF THE INVENTION

FIG.1shows a schematic side view of a boiler cleaning device according to an embodiment of the invention, comprising a shock wave generator10which is attached to a boiler20in a resilient manner. Resilient means that the shock wave generator10is not rigidly fixed to the boiler wall20, but can move resiliently in the longitudinal direction of the shock wave to be generated. The shock wave generator10has a hollow cylinder19through which the pressure wave generated by this shock wave generator10is channelled into the boiler. This hollow cylinder19is inserted in a boiler connection piece31. The boiler connection piece31is connected to a boiler wall flange30, which is placed on the boiler wall20from the outside and is firmly connected to the boiler wall20. The boiler access is defined through the boiler wall20. The boiler connection piece31has a fastening flange32on the side opposite the boiler wall flange30in the longitudinal direction of the hollow cylinder19. This boiler-side fastening flange32is thus directly and rigidly connected to the boiler wall flange30via the guide tube31. A fastening flange40on the cleaning device side is rigidly connected to the boiler-side fastening flange32, which holds the shock wave generator10via a series of here three second longitudinal rods or tension rods154, around which damping spring assemblies150,156are arranged. Each damping unit150,156has two tension/compression springs150,156arranged in a row in the longitudinal direction, which are inserted between the mounting flange on the boiler side and a centre plate151or between the centre plate151and the damping plate152. The springs150,156are supported on the centre plate151directly or on bushes154facing the ends of the springs on this centre plate151, while the associated second longitudinal rod154is passed through an opening in the centre plate151. Since the housing body10is now rigidly attached to the centre plate151with first longitudinal rods155and the damping plate152is rigidly attached to the boiler-side mounting flange with the second longitudinal rods154, a cleaning plus leads to a compression and subsequent return of the hydraulic cylinders, which absorb the main part of the recoil forces, with the remainder being absorbed by the spring assemblies.

The three damping spring assemblies150,156are arranged in the circumferential direction around the longitudinal axis of the hollow cylinder19at an angular distance of 120 degrees. Four or more, for example six or eight such packs can also be arranged, preferably at the same angular spacing. In addition to the damping spring packs150,156, hydraulic dampers250are provided between the centre plate151and the damping plate. The number of hydraulic dampers250can be one or two between each of the three damping spring packs150,156, i.e. a total of three or six. If there are four, six or eight damping spring assemblies150, the same number of hydraulic dampers250can also be arranged at the same angular distance from one another, if possible. The hydraulic dampers250usually absorb between 50% and 90%, usually more than 75% to 90%, for example between 80% and 90% of the recoil energy. The advantage of the hydraulic dampers250also lies in the even distribution of the recoil forces over the stroke compared to the spiral springs of the spring assemblies150,156.

When the pressure wave shock of the shock wave generator10is directed in the longitudinal direction through the tube of the hollow cylinder19through the boiler wall20into the boiler, the hydraulic dampers250are lengthened or shortened by the recoil of the shock wave generator10due to the flow dynamics in the dampers and the damping springs150,156are stretched or compressed in parallel and the shock wave generator10moves away from the boiler wall20in the longitudinal direction.

Advantageously, the weight of the shock wave generator10is supported by a holding lever12via a holding chain11, which holding lever12is fastened via a horizontal swivelling axis13to a supporting frame14, which is also fastened in a longitudinally displaceable manner in the longitudinal direction of the hollow cylinder19via a trolley16to a trolley profile15. The holding chain11is provided with a length such that the axis of symmetry or longitudinal axis of the shock wave generator10corresponds to the axis of symmetry or longitudinal axis of the boiler nozzle31and the boiler wall flange30, i.e. they coincide. In this way, the pressure wave is emitted around the same axis as the axis of the boiler outlet and the recoil is absorbed in an ideal manner.

The axis of the trolley profile15is advantageously arranged in the vertically aligned plane, which is also encompassed by the aforementioned longitudinal axis of the shock wave generator10. This allows the shock wave generator unit with the hollow cylinder19to be pulled directly backwards out of the boiler nozzle31.

FIG.2shows a schematic side view of a boiler cleaning device according to a further embodiment of the invention. As in the embodiment according toFIG.1, the cleaning tube19has a larger diameter. The term “larger diameter” is to be seen in comparison with the embodiment according toFIG.5.

Identical features are labelled with the same reference signs in all figures. The difference between the two devices shown inFIG.1andFIG.2lies in particular in the type of mounting and damping. While the design shown inFIG.1has a series of damping spring assemblies150,156arranged around the circumference, three damping cylinders50are provided here at an angular distance of 120°. These damping cylinders50have the same function as the hydraulic dampers. The only difference is that no spring assemblies are provided. In the design shown inFIG.2, the combination of boiler-side mounting flange32—boiler connection piece31—boiler wall flange30ofFIG.1is replaced by a closure housing60, which has the same function. A further difference is that air connections70are provided at 120° intervals on the circumferential circle, which are explained in the further description and are in operative connection with the butterfly valve80.

The inside of the shutter housing60has the 120° closures81of the shutter80described below.

The essentially triangular convex mounting flange40on the cleaning device side accommodates the abutments of the three damping cylinders50at its corners. The pistons51protruding from the damping cylinders50on the opposite side are attached to the shockwave generator10, which is shown here only schematically as a simple cylinder. In other words, the weight of the shock wave generator10would act on the mounting flange40with a corresponding moment. It is also possible that the damping cylinders50are supported via a support plate, not shown inFIG.2, with apertures provided for these damping cylinders50and a central hole for and on the connecting tube43.

The hollow cylinder19is inserted in the connecting tube43. Although it could also transmit the weight of the shock wave generator10with play and thereby tilting, it is preferably inserted freely in the tube43. When an explosion is triggered by the shock wave generator10to clean the boiler, a shock wave travels through the hollow cylinder19in the longitudinal direction of the cleaning device, moving the shock wave generator10in a direction opposite to the boiler wall20via the recoil. The damping cylinders50have a damping effect on this movement and pull the shock wave generator back again after the first large amplitude. This can be achieved in particular by using active damping cylinders50as hydraulic cylinders, in which the pistons51can be extended and retracted in a correspondingly controlled manner.

A further advantage of the use of damping cylinders50over damping springs150will become apparent in connection with the description ofFIGS.8A to8C.

FIG.3shows a perspective view of the boiler cleaning device according toFIG.1. This also includesFIG.4, which shows a side view of the boiler cleaning device according toFIG.1. Three damping spring assemblies are braced in two sections by individual springs150,156between a damping plate152, a centre plate151and the fastening flange40on the cleaning device side. A series of flange connecting screws41are also recognisable on the fastening flange40, with which this fastening flange40is fastened to the boiler-side fastening flange32or a corresponding flange of the closure housing60. In other words, the closure housing60with an internal closure flap and/or ventilation can also be used with the construction according toFIG.3, even if further advantages only arise in connection with a retractable generator10according toFIG.2. The damping springs150,156are guided through openings in the damping plate152and mounting flange40and braced on the outside in each case. Openings are provided in the centre plate151for the second tension rods154to pass through, each of which abuts against a sleeve157provided on both sides of the centre plate151, which separates the spring action for the two sections to the damping plate152and mounting flange40.

The hydraulic dampers250are arranged between the damping plate152and the centre plate151, as they have to absorb the first recoil and the weaker springs should only return the then compressed hydraulic dampers.

From attachment points153on the shock wave generator10, a series of here six first tension rods155are fixedly connected to the centre plate151at an angular distance of 60 degrees to each other, for example passed through the centre plate151with a reduced cross-section through a corresponding bore and fastened with a screw on an external thread located on each end of a first tension rod155.

When the shock wave generator10is triggered, it moves away from the boiler wall20and exerts a tensile force on the centre plate151via the tension rods155, which causes the right-hand damping springs150close to the mounting flange to stretch. At the same time, the left damping springs156on the damping plate side and the hydraulic dampers250are shortened so that a damping movement in the opposite direction results once the shock wave generator10has reached a maximum distance from the boiler wall20. The damping springs150,156and the hydraulic dampers250are designed in such a way that the oscillating movement is minimised.

The hydraulic dampers250are mounted on one side in the damping plate152and abut against the centre plate151by means of a piston and a spring (package251) surrounding it.

Hydraulic dampers250are provided between damping plate152and centre plate151parallel to the springs156, which reduce the peak force with the same energy absorption.

It can also be seen inFIG.3that the diameter of the hollow cylinder19is such that it is only guided through the inside diameters of the mounting flange40, centre plate151and damping plate152with a small amount of play. It is therefore the maximum diameter of a hollow cylinder19that can be used together with this cleaning device.

FIG.5shows a schematic side view of a boiler cleaning device according toFIG.2, but with a cleaning tube190with a smaller diameter, whileFIG.6shows a perspective view of the boiler cleaning device according toFIG.5. All the features of the attachment of the shock wave generator10to the attachment flange40according toFIG.5are identical to the features according toFIG.3, the only difference being the different design of the exhaust pipe190, which has a much smaller diameter here. Therefore, the distance from the outside of the hollow cylinder190to the inside diameter of the damping plate152, the centre plate151and the flange40is much greater. Care is merely taken to ensure that an inner cover plate with a centrally adapted opening42is provided on the mounting flange40or on the corresponding closure housing60, which surrounds the tube190with little play and can be easily sealed with a seal. In a preferred embodiment, the mounting flange40and the cover plate42are in one piece, in other words, the mounting flange40has an inner diameter corresponding to the cover plate42shown and is selected and installed according to the pipe diameter.

FIG.14shows a partially sectioned side view of the assembly group of a damping unit, as shown inFIG.4orFIG.6. The hydraulic dampers250are shown fixed in the plate152.

FIG.7shows a schematic partially sectioned side view of a boiler cleaning device according toFIG.2.FIG.8Ashows the same schematic partially sectioned side view of the boiler cleaning device according toFIG.2in idle mode, i.e. in a parked position.FIG.8Acorresponds to a scaled-down version ofFIG.7.FIG.8Bshows a schematic partially sectioned side view of the boiler cleaning device according toFIG.8Ain cleaning mode, i.e. with the cleaning device in an advanced position. Due to the small damping path, it is essentially irrelevant whetherFIG.8Bshows the cleaning device before, during or after a shock wave impact.FIG.8Cshows a schematic, partially sectioned side view of the boiler cleaning device according toFIG.8Ain a partially dismantled maintenance position, i.e. in a retracted position of the cleaning device. In addition,FIG.9shows a schematic perspective view of the closure flap80with the three 120-degree segment closures81of the boiler cleaning device according toFIG.7.

The detailed view inFIG.7shows that a closed closure flap80is inserted in the interior of the closure housing60, which tapers towards the boiler wall20, on the inside of the fastening flange40, which forms an inner shoulder of the closure housing60. The closed closure flap80forms a convex cone projecting in the direction of the boiler wall20. It consists of three 120-degree closures81, each covering an angular range of 120 degrees, which can be swivelled about their swivel axes between the closed position shown inFIG.7andFIG.9and a fully open position shown inFIG.12C. The 120-degree closures81are thereby pivotable about tangential axes lying in a plane at a predetermined distance from the longitudinal axis, the said plane being perpendicular to the longitudinal axis of the closure housing60. These tangential axes are predetermined by the hollow bearing axes84. Two sliding cylinders82are arranged around each hollow bearing axis84with a return spring83located between them, with which an opened segment of a 120-degree closure81is returned to the locking position.

InFIG.8A, the shock wave generator10is in a rest position in which the usual working processes take place in the boiler.FIG.8Bthen shows the forward movement of the shock wave generator10by shortening the pistons51in the damping cylinders50, whereby the hollow cylinder19advances in the guide tube31in the direction of the boiler wall20and the front edges of the hollow cylinder19abut against the side surfaces of the 120-degree locks81and these open in synchronisation with each other against the spring force of the return spring83. InFIG.8B, the front edge of the hollow cylinder already protrudes slightly beyond the boiler wall30into the boiler.

The inner shape of the closure housing60extends from the shoulder on which the position axes84are provided for disciples and to the boiler wall flange30of the housing60so that the outward-facing sides and surfaces of the closure81can position themselves in this widened rear space when the shock wave races through the hollow cylinder19, which is guided in the guide tube31.

FIG.8Cthen schematically shows a disassembled shock wave generator10in that the sealing housing60with the integrated sealing cap80is firmly attached to the boiler wall20via the boiler wall flange30. The damping cylinders50, on the other hand, are disassembled and shown individually, and the shock wave generator10with its attached hollow cylinder19is shown in further extension. Preferably, the shockwave generator10with the hollow cylinder19is suspended from the trolley profile15via the elements shown inFIG.1: retaining chain11, swivel arm12, trolley16. In addition to a single chain11, it is also possible to provide further fastening chains or rods if the weight of the shockwave generator10with its hollow cylinder19is not balanced.

FIG.9shows a schematic perspective view of the 120-degree segment closure80of the boiler cleaning device according toFIG.7or alsoFIG.8A. The closure elements81, which are essentially triangular in a plan view, abut each other with connecting edges and end at a convex tip orientated towards the boiler wall20. The surface pointing towards the boiler wall20and thus towards the boiler has a plurality of openings85for infusion cooling. In other words, each closure element81has a double-walled structure which extends as far as the sliding cylinder82, so that each individual closure element81can be pressurised with cooling ambient air or corresponding gases via the air connection70and the hollow bearing axis84. These pressurised gases flowing into the hollow bearing axis84then escape through the openings85into the space of the opening in the boiler wall20.

In this context,FIG.10shows a schematic, partially sectioned perspective view of the 120-degree segment closure81according toFIG.9. The reference sign71indicates the gas flow direction and thus a volume flow which enters the hollow bearing axis84at the air connection70and then enters the cavity in the double-walled closure elements81at the sliding cylinders82, which are also hollow and have an opening to the hollow bearing axis84, through corresponding openings in the wall of the hollow bearing axis84and then exits through the opening85. In the embodiment example of the closure elements81, reinforcing ribs86are provided.

FIG.11shows a schematic, partially transparent perspective view of a segment81of the 120-degree segment closure80according toFIG.10, in which the regularly distributed openings85and the essentially radially extending reinforcing struts86are shown in particular. The passage for the volume flow71can be seen from the thickness of the transition between the sliding cylinder82and the closure element81.

FIG.12Ashows above a side view, on the left a top view of the 120-degree segment closure in the area of the closure housing and on the right a top view out of the boiler, in each case of a closed 120-degree segment closure80as in a rest or maintenance position, i.e. in normal boiler operation.FIG.12Bshows at the top a side view, on the left a top view of the 120-degree segment closure81in the area of the closure housing60and on the right a top view out of the boiler, in each case of a partially opened 120-degree segment closure81during the transition between the parking and cleaning positions; andFIG.12Cshows above a side view, on the left a top view of the 120-degree segment closure81in the area of the closure housing60and on the right a top view out of the vessel, in each case of an open 120-degree segment closure81as when a cleaning position is reached, while cleaning is being carried out or shortly thereafter. The sequence of the drawings shows that the closure elements81open completely so that the hollow cylinder19can pass through them.

The individual closing elements81are pressed on by the front edge of the hollow cylinder19until the tip of the closing elements rests on the outside of the hollow cylinder19and this is pushed further into the boiler wall area if necessary.

FIG.13shows a perspective side view of a ventilation device for the guide tube31. The mounting flange32is attached here to a modified closure housing60′, which is connected to the boiler wall flange30, but can be moved longitudinally in relation to it. For this purpose, the sealing orifice35is located opposite the outer casing of the guide tube. For this purpose, an orifice flange34is mounted on the boiler wall flange30, which has a receptacle on its side facing the boiler20in which an orifice35can be inserted. The orifice35surrounds the guide tube38and can be moved in height, in particular, so that the expansion of the boiler and thus a change in height of the breakthrough opening22in the boiler wall20can be tracked relative to the guide tube38. This is associated with a mechanical decoupling of the recoil forces acting on the fastening flange32, which normally act on the boiler wall20, and which forces now act on a separately supported closure housing60′, whereby temperature or assembly-related misalignments with the guide tube38can be absorbed by the displaceable plate35, which is mounted with play.

The guide tube38itself is double-walled and has a helical inner cavity36. It can also be said that a helical intermediate wall is inserted between the two walls of the guide tube38, which allows air to be blown in in the area of the mounting flange32, via an air connection70not shown here, which then moves between the double walls of the guide tube31in the direction of the boiler, heating up, and finally flows into the boiler at the mouth of the opening in the boiler wall20.

There is a cylindrical gap37between the boiler wall and the guide tube38, which gap37is closed off from the shock wave generator10by the orifice35. In the advanced position, the hollow cylinder19is always surrounded by the guide tube38and cooled by the air volume flow.

The guide tube38itself is designed with a flange33for this purpose, which is firmly connected to the mounting flange32of the housing60′ in the receptacle provided by the mounting flange29. One or more passages may be provided in the receiving flange29for the cooling fluid, which can be fed into and via the flange33into the guide tube38at this point.

In an embodiment not shown in the drawings, a telescopic extension is provided for the retraction option of the guide tube38, whereby the retraction mechanism can be pneumatic or hydraulic. By briefly advancing the guide tube38to the position shown inFIG.13and then retracting it after the cleaning pulse, the heating of the guide tube38is kept sufficiently low even at very high flue gas temperatures in the boiler and at the same time the often porous boiler wall20is protected from the cleaning pulse. Conversely, the guide tube38is at least partially withdrawn from the boiler wall opening22between individual cleaning pulses, so that essentially only the front edge39of the guide tube38is exposed to the gases contained in the boiler, since gas exchange with the interior of the guide tube does not usually take place.

FIG.15shows a schematic perspective view of a fastening device for a boiler cleaning device according to a further embodiment example with elastomers350in the damping units.FIG.16shows a side view of the boiler cleaning device as shown inFIG.15. Finally,FIG.17shows a sectioned partial side view of an assembly group of the damping units constructed from elastomers350with an optional guide tube353.

In a further advantageous embodiment of the damping units, these consist of toroidal or tyre-shaped elastomers350arranged in a row, each of which is arranged around one of the second longitudinal rods or tensioning rods354and is supported on the centre plate151directly or on bushes352(such as bushes157) facing the directly adjacent elastomers350on this centre plate151, while the associated second longitudinal rod354is passed through an opening in the centre plate151. In particular, four such elastomers350are provided at an angular spacing of 90 degrees, each with two times seven elastomers350on the corresponding four longitudinal rods354. Two first tension rods155are arranged between each of these four longitudinal rods354as in the other embodiments, i.e. between the centre plate151and the housing of the cleaning device with the damping plate152. In particular, the elastomers350are copolyester elastomers. Spacers351, in particular metal plates, can be provided between every two elastomers350and the second longitudinal rod354can be surrounded by a hollow radial guide tube353, against which the inner edges of the elastomers350abut, so that the elastomers350have essentially no play with respect to the centre axis355of guide tube353and elastomers350.

One advantage of using groups of elastomers350over hydraulic solutions is that the damping works satisfactorily in both directions. The drawing of the embodiment example shows a symmetrical arrangement of the same number of elastomers on both sides of the centre plate151. It is also possible to use differently damping elastomers350based on a different material or different dimensions or to arrange a different number on both sides of the centre plate151in order to achieve asymmetrical damping.

LIST OF REFERENCE SYMBOLS