Abstract:
With a method and apparatus for the percussive cleaning of objects disposed in a chamber that is under process pressure, whereby an elongated percussive element is held below and in contact with the object that is to be cleaned and percussive energy is applied to the percussive element via an accelerated elongated striker, it is provided for a more simple pressure balancing that at least during the acceleration of the striker, the two ends of the striker be maintained at the same pressure, which essentially corresponds to the pressure in the process chamber.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method and an apparatus for the percussive or beating cleaning of objects disposed in a process chamber that is under process pressure. 
     A method and apparatus of this type are known from DE-PS 31 27 734. The push member thereof, which is designated as a transmission element, is provided with an equalizing channel that connects the chamber that is under process pressure and the pressure chamber that accommodates the compression spring. Furthermore, the push member is provided with an annular collar. Instead of the pressure equalization channel, the balancing chamber that accommodates the spring can be connected to an externally operated gas pressure balancing apparatus. With both embodiments of the known percussive apparatus, the pressure balancing is thus effected in the region of the push member, so that the latter must have a relatively complicated construction. 
     With the embodiment having the equalization channel to the chamber that is under process pressure, the danger exists that if dust-containing gases are present in the process chamber, dirt or other contamination can enter the space that accommodates a spring. With both embodiments, the free space that is defined by the one end of the percussive element and by the percussive mechanism is connected to the atmosphere. One end of the striker projects out of the mechanically, pneumatically or hydraulically operating percussive mechanism. 
     It is therefore an object of the present invention to provide a method and apparatus of the aforementioned general type where the pressure balancing or equalization is effected in a simple manner. 
     SUMMARY OF THE INVENTION 
     This object is realized in that at least during acceleration of the striker, the two ends of the striker are maintained at the same pressure, which corresponds essentially to the pressure in the process chamber. 
     In this manner, the required pressure equalization is no longer carried out in the region of the percussive element, but rather in the region of the mechanically, pneumatically or hydraulically operating percussive mechanism, so that no dirt or contamination can enter the spring chamber via a free or exposed equalization channel, which could very rapidly lead to disruptions in operation; furthermore, a more straightforward configuration of the percussive or beating element is possible. The percussive element can be held in abutment under a resilient bias via at least one spring or via a pneumatic load. 
     Further features are directed to advantageous specific embodiments of the method. 
     The invention is also directed to a percussive or beating apparatus for the percussive cleaning of objects disposed in a process chamber that is under pressure. The apparatus includes a housing, an elongated percussive or beating element that is guided in the housing in a sealed manner, extends through the wall of the process chamber, and rests against the object under the effect of a biasing means, and furthermore includes a percussive mechanism including an elongated striker that is designed for the percussive element. One end of the percussive element and the associated end of the striker extend into a free space or chamber of the housing in such a way that in a state of rest of the percussive mechanism, the two ends are spaced from one another by a distance that is a function of the available percussive energy. 
     This apparatus is inventively characterized in that the percussive element has an essentially rectilinear cylindrical configuration, and in that that end of the striker that projects out of the percussive mechanism and is remote from the percussive element is surrounded by a balancing or equalization chamber that communicates with the free space in the housing and is subjected to a pressure that corresponds essentially to the process pressure. 
     The connection or communication of the free space with the balancing chamber can be achieved by a connecting line that is disposed outside of the housing, or can be achieved by at least one balancing channel that is guided through the striker. 
     With the preferred biasing of the percussive element with a spring, the latter is disposed in the free space, so that the free space serves not only for accommodating the spring but also for providing the acceleration path that is necessary for the operation of the apparatus. 
     Furthermore, as viewed in the direction of beating, an annular chamber that can be supplied with sealing gas introduced through the housing is provided after a seal means that is associated with the spring biased end of the percussive element. The sealing gas can be the same gas, for example nitrogen, as is used for supplying the free space and the balancing chamber. 
     This sealing gas can be held in the annular chamber by a further seal means disposed after the annular chamber, as viewed in the direction of beating, and/or can exit through a gas permeable filter in a direction toward the percussive or beating end of the percussive element. 
     Furthermore, it is expedient to provide that end of the housing that faces the object with a guide collar that surrounds and is spaced from the percussion element, with the free end of the guide collar additionally guiding the percussion element at a distance from the wall that bounds the process chamber. 
     The free space and the balancing chamber are preferably supplied with a pressure that is lower than that of the annular chamber. However, it is also possible to supply the same pressure to the free space, the balancing chamber and the annular chamber if this pressure is somewhat greater than the process pressure. In this connection, it must be noted that in the claims and in the specification it is indicated that the balancing or equalization pressure that acts upon the striker should essentially correspond to the process pressure. This means that the balancing pressure should not deviate significantly from the process pressure, since otherwise the beating element that operationally is held against the object that is to be cleaned under the influence of the spring, is acted upon by an additional force. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in greater detail in conjunction with the accompanying drawings. Shown are 
     FIG. 1 a cross-sectional view through the inventive apparatus, with the equalizing or balancing pressure differing from the pressure of the sealing gas, 
     FIG. 2 an apparatus where the balancing pressure is the same as the sealing pressure, 
     FIG. 3 an embodiment similar to that of FIGS. 1 and 2, whereby however the pressure balancing between the balancing chamber and the free space rather than being effected by an externally disposed balancing line, is effected by a balancing channel in the striker, and whereby the end position of the striker when striking movement is activated can be detected by a position-measuring device, and 
     FIG. 4 is a partial view of the arrangement of FIG. 3 where the percussive end of the percussive element is deformed, and with the striker being shown in the striking position. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 schematically illustrates the object that is to be cleaned in the form of a heat transfer surface 1 that is composed of tubes and that is disposed in the pressure vessel 2 of a coal gasification unit. The heat transfer surface is subjected to the flow of dust-laden gas G at least from the outside. 
     Provided on the wall of the pressure vessel 2 is a connector 3 having a mounting flange 3a for the attachment of the percussive or beating mechanism 4. The percussive mechanism 4 has a housing 5 with a mounting flange 5a via which it can be bolted or otherwise attached to the connector. An essentially rectilinear cylindrical percussive or beating element 6 is mounted in the housing 5 so as to be axially displaceable. The conically tapered percussive end 6a rests against the heat transfer surface 1 subject to the action of a compression spring 7 that on the one hand is supported against the other end 6b of the percussive element and on the other hand is supported against a shoulder 5b of the housing. The end 6b extends into a free space or chamber 8 that is provided in the housing and that also accommodates the spring. 
     Detachably connected to the housing 5 is a striker 9 that in FIG. 1 is embodied as a double acting pneumatic piston cylinder drive mechanism. The two ends 10a and 10b of the piston rod 10 project out of the cylinder 11. The percussive element 6 and the piston rod 10 are aligned with one another and are disposed in the same axis. The end 10a of the piston rod 10 also projects into the free space 8. The other end 10b of the piston rod is surrounded by a pressure balancing or equalization housing 12 that delimits a balancing or equalization chamber 13. The free space or chamber 8 and the balancing chamber 13 are interconnected by a line 14 that in turn is connected via a pressure regulating valve 15 to a pressure source 16, preferably a N 2  source. 
     Provided in the housing 5 is a channel 17 that extends to an annular chamber 18 formed in the guide portion 5c of the housing and that via a regulating valve 15&#39; is also connected to the pressure source 16. Provided on that portion of the percussive element 6 that is associated with the end 6b, next to the annular chamber 18, is a multi-part seal means 19. On the other side of the annular chamber 18, as viewed in the percussive or beating direction, is first a compact seal 20 and then a metal fabric ring 21 that acts as a filter. In this way, the sealing effect of the seal means 19 and 20 is such that gas that is introduced via the channel 17 cannot exit via the seal means 19 but rather exits in a precise manner via the components 20 and 21 into the chamber in the pressure vessel that is under the process pressure P 2 . 
     That end of the housing 5 that faces the heat transfer surface is provided with a guide collar 5d that extends around and is spaced from the percussive element 6, with an annular part 22 that surrounds the percussive element and guides the same being disposed on the free end of the guide collar. A control unit 23 is provided for the control of the regulating valves 15 and 15&#39;; a control signal derived from the process pressure P 2  via a measuring device 24 is conveyed to the control unit. In the embodiment illustrated in FIG. 1, the valve 15 is regulated in such a way that a pressure that corresponds to the process pressure P 2  is established in the free space 8 and in the balancing chamber 13. The force with which the percussive element 6 rests against the heat transfer surface 1 is then essentially determined merely by the force of the spring 7. When the piston is accelerated along the path from its rest position illustrated in FIG. 1 until it strikes the end face of the end 6b, a pressure equalization or balancing is effected between the chambers 8 and 13 via the line 14. The pressure that exists in the annular chamber 18 is set to be somewhat greater than the process pressure P 2  by the control unit 23 in conformity with a pressure Δp via the regulating valve 15&#39;. To summarize: P 2  =P 8  =P 13 , and P 18  is somewhat greater than P 2 . 
     In the embodiment illustrated in FIG. 2, the channel 17 is connected directly to the connecting line 14, so that the control unit 23 controls only the regulating valve 15. In this case, the following applies: P 8  =P 13  =P 18 , and P 2  is somewhat less than P 8 . 
     In the embodiment of FIG. 2, the spring 7 could be dispensed with, since due to the Δp to the pressure P 2 , an abutment of the percussive element 6 against the heat transfer surface 1 is taken care of. However, due to possible pressure fluctuations in the process chamber, a spring 7 should be provided. 
     From the description of the drawings, it can be seen that the required pressure balancing relative to the vessel pressure P 2  is not achieved by a particular stressing and configuration of the percussive element, but rather via a straightforward configuration and manner of operation of the striker drive. By the directed introduction of a sealing gas into the region of the push member via the annular chamber 18, a directed leakage in a direction toward the interior of the pressure vessel 2 is achieved, so that a deactivation of the entire percussive chamber is achieved. This inhibits corrosion. Furthermore, by means of the leakage flow, the seal means that is provided for dust filtration is kept free. 
     In the specific embodiment illustrated in FIGS. 3 and 4, the pressure balancing between the free space 8 in the housing 5 is not effected by the partial branch of the line 14 that in FIGS. 1 and 2 branches off from the outlet of the valve 15 and leads to the pressure balancing chamber 13, but rather is effected via a pressure balancing channel that leads from the end 10a of the piston rod 10 to the end 10b of the piston rod. This pressure balancing or equalization channel comprises radial bores 10d and the channel 10e that extends through the piston rod 10, preferably axially centrally. 
     In FIG. 3, the piston rod 10 with its piston 10c is shifted by the spring 7 into its right hand end position. Upon activation of the piston cylinder drive mechanism, the piston rod is accelerated toward the left, in FIG. 3, until it strikes the percussive element 6. 
     As can be seen in FIG. 4, during the course of operation and as a consequence of frequent percussive or beating movements, the working end of the percussive element 6 deforms, i.e. the end position of the right end 10b is displaced toward the left in FIGS. 3 and 4 by a corresponding amount. 
     A measured value detector 25 is disposed on the pressure balancing housing 12 for detecting the shortening of the percussive element 6 by detecting the displacement of the end position of the piston rod of the actuated piston cylinder drive mechanism. This is schematically indicated in FIG. 4. Suitable measured-value detectors are inductive or capacitative proximity initiators that are disposed outside the housing 12. It is also conceivable to provide photoelectric arrangements within the balancing chamber 13. It is also possible to dispose a mechanical/electrical measuring pin as a limit switch within the balancing chamber. 
     When the output signal of the proximity initiator indicates the presence of a deformation of the percussive element that is no longer acceptable for the percussive or beating operation, the percussive element must be replaced. The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.