Patent Publication Number: US-3971343-A

Title: Devices for the cleaning of heating surfaces

Description:
BACKGROUND OF THE INVENTION 
     In the past, jarring devices have proved useful for the purpose of cleaning the heating surfaces of pipe coils, particularly where such heating surfaces of pipe coils have been exposed to gases which are heavily particle-laden. For example, they have been used, among other things, in the waste-heat boilers of calcining furnaces. By means of such jarring devices, which may be operated at predetermined time intervals, adherent particles are loosened and shed from the outer surface by the jarring of the pipe coils against each other. Known jarring devices of this type may be regulated as to jarring frequency by monitoring the temperature of the effluent gas, since it will rise as the pipes become particle covered and; therefore, less efficient in heat transfer capability. In this connection reference is made to U.S. Pat. No. 3,721,217. With such jarring devices, however, there is a danger that the periodic forces arising from the motion of the pipe coil masses may transfer, by way of their bearing elements, onto the body of the boiler and its supporting structures. Therefore, the bearing elements must be designed and/or dimensioned to withstand such extra dynamic loads. In addition, the transfer of periodic alternating forces from the masses in motion may produce troublesome oscillations, (i.e., resonance) in supporting structures, scaffolding and/or buildings, which might, under certain circumstances, totally or partially destroy, or at least damage, portions of the installation. Alternatively, the period of jarring may be varied to reduce such adverse effects, but this is undesirable because this makes the frequency of jarring, and therefore the cleaning effectiveness and periods, depend on considerations not necessarily, or even usually, related to the factors which are relevant to the rate of particle accumulation. 
     Therefore, an object of this invention is to provide a means for the cleaning of the heating surfaces of pipe coils in such a way as to minimize or minimize or prevent the transfer of forces to the body of the boiler from the pipe coil masses as they move. 
     SUMMARY OF THE INVENTION 
     Desired objectives may be achieved through practice of the present invention which, in one embodiment, comprises a drive-cylinder actuated, two-armed lever, which is pivotally interconnected with suspended pipe coils which are to be cleaned by upper and lower connecting means, wherein the lever arms of the two-armed lever are of unequal length and the pivot of said lever is so positioned that it resides at a distance ##EQU1## BELOW THE SUSPENSION LEVEL AT WHICH THE PIPE COILS ARE PIVOTALLY MOUNTED, WHEREIN A DENOTES THE DISTANCE OF THE UPPER CONNECTING MEANS, AND B THE DISTANCE OF THE LOWER CONNECTING MEANS, RESPECTIVELY, FROM THE PIVOT POINTS OF THE PIPE COILS AT THE SUSPENSION LEVEL, AND WHEREIN THE LENGTH OF THE UPPER LEVER ARM R 1  AND THE LOWER LEVER ARM R 2  RESPECTIVELY ARE (C - A) AND (B - C); WHEREBY FORCES AND MOMENTS INDUCED BY JARRING OF THE COILS ARE OFFSETTING, AND OBJECTIONABLE OSCILLATIONS IN THE BOILER BODY DURING THE JARRING OPERATION MAY BE AVOIDED. 
    
    
     DESCRIPTION OF DRAWINGS 
     This invention may be understood from the accompanying description and drawings in which 
     FIG. 1 is a lengthwise/cross-section through a waste heat boiler in which devices according to this invention may be used, 
     FIG. 2 is a transverse section of the boiler shown in FIG. 1, 
     FIG. 3, is a perspective view of a prior art mechanism for use with a jarring device, 
     FIG. 4, is a schematic arrangement of a jarring device embodying the present invention, 
     FIG. 5, is a schematic arrangement of a jarring device embodying the present invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring first to FIG. 1, there is shown a waste heat boiler 1 in which embodiments of the present invention may be used. In normal use, the boiler is traversed by particle-laden waste gases in the direction of the arrows 2 and 3. The waste gas duct 4 is positioned horizontally to accommodate four nests of pipe coils 5. These pipe coil nests 5 are suspended and are oriented generally perpendicular to the direction of the waste gas flow. The pipe coils 5 are fed by collectors 6 located above the waste gas duct 4. Below the pipe coils, provision has been made for ash or particle funnels 7. FIG. 2 further illustrates this embodiment, but in a section which is transverse to that shown in FIG. 1. 
     As shown in FIG. 3, a jarring device associated with the pipe coil nest 5 may consist of a hydraulically or pneumatically actuated cylinder 8, the lower end of which is secured to boiler wall 9. The piston rod 10 projecting from its upper end is linked to shaft 12 by means of a one-armed lever 11; the shaft resting on a support 13 which is also secured to the boiler wall. Positioned on shaft 12 are two-armed levers 14, whose free extremities are respectively connected to connector means in the form of cooled, hollow pipes 15 and 16. These hollow pipes 15, and 16 project through an opening 17 in the wall of the boiler 9 and on to the pipe coils in such a way that the individual pipe coils are alternatingly connected to the lower or the upper hollow pipes. Reciprocating motion of the piston rod 10 causes the pipe coils to move back and forth; whereby, in each case, the two adjoining pipe coils may be caused to move against each other. 
     FIG. 4 is a simplified illustration of the geometric arrangement of a device embodying this invention associated with two adjoining pipe coils. Line 18 represents the frame of the boiler, supporting the drive cylinder 8 at point A and the shaft 12 at fulcrum C; the pipe coils being suspended from pivot points along the level E. When the piston rod is moved in the direction of the arrow 19, the upper hollow pipe 16 moves in the direction of arrow 20, and the lower hollow pipe 15 in the direction of arrow 21. In the process, the two pipe coils have imparted to them the same angular displacement τ. To achieve this end, the operating lever arms r 1  and r 2  of the two-armed lever 14 are of unequal length. The length of each of the lever arms is determined by the distance C of the pivot C from the suspension level E and c in turn is calculated from the distances a and b of the hollow pipes 16 and 16 from the suspension level E. 
     As an example, for a waste heat boiler with four suspended nests of pipe coils, designed for a steam output of 20 metric tons per hour, the pipe length was selected at 4,000mm below the suspension level E. Based on design considerations, a was set at 2,260mm and b at 2,560mm. From the expression ##EQU2## we obtain c = 2,400mm. Hence, the effective length of each of the lever arms r 1  and r 2  is (c - a), (b - a) respectively, or 140mm and 160mm respectively. A jarring device so constructed will transmit no substantial induced forces into the body of the boiler, and therefore the physical arrangement of the drive cylinder and the time intervals at which it is to operate can be chosen at will and in accordance with the rate of particle accumulation, rather than being restricted by considerations of force resonances. 
     In FIG. 4, the drive cylinder 8 is arranged vertically. As shown in FIG. 5, a drive cylinder may be inclined at an angle β to the vertical, whereby the point A supporting the drive cylinder on the frame of the boiler lies below the fulcrum C, is similar to the arrangement shown for the apparatus in FIG. 3. Alternatively, as shown in the upper portion of FIG. 5, the cylinder also can be secured above the fulcrum C. It is to be understood that the embodiments herein discussed and illustrated are by way of illustration and not of limitation and that other embodiments of this invention may be made by those skilled in the art without departing materially from the spirit or scope of this invention.