Patent Publication Number: US-4093242-A

Title: Slag blower wall box seal

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a wall box seal for the slag blower or lance tube of a device employed for blowing soot or other combustion products from the tubes of boilers. 
     Customarily, a plurality of wall box seals are mounted on the side wall of a boiler with the rotatable and projectable tubular slag blower or cleaning element extending therethrough and into the combustion chamber adjacent the boiler tubes to be cleaned. The wall box seals are provided for the purpose of preventing products of combustion and soot from escaping from the interior of the boiler to the exterior thereof along the outer surface of the tubular slag blower as it rotates and reciprocates and conveys fluid under pressure to nozzles or outlet openings in the slag blower at the head end thereof. 
     The tubular slag blower member, through which steam, air or some other suitable cleaning material is forced under pressure for blowing the boiler tubes clean, usually becomes warped due to the heat of the furnace and roughened and worn on its outer surface where it slides and rotates through the wall box seal. The seal also becomes worn and must frequently be replaced or repaired in order to prevent the escape from the boiler interior of soot and combustion products which present health hazards to persons in the area adjacent the boiler. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved wall box seal which fits tightly around the tubular slag blower or lance tube and prevents soot and other combustion products from being blown out of the interior of the boiler around the slag blower member. The present seal is adapted to expand and contract so as to conform to the outer surface of the slag blower member and at the same time to slide radially in order to accomodate irregularities and warpage of the slag blower member as it rotates and reciprocates. 
     It is, therefore, a principal object of this invention to provide a wall box seal which may be readily installed without disturbing a seal already in place. 
     Another object of the invention is to provide a seal which consists of few parts and is inexpensive to manufacture. 
     A further object is to provide a seal which will prevent the escape of products of combustion from a furnace combustion chamber past a worn out seal already in place. 
     These and other objects and advantages of the invention will become more apparent from the following description of a preferred form of the invention when taken in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary side elevational view, partly in section, of a wall box and seal arrangement for a tubular slag blower according to the present invention. 
     FIG. 2 is a fragmentary and elevational view, partly in section, of the wall box and slag blower tube on a smaller scale and taken on the line 2--2 of FIG. 1; 
     FIG. 3 is an enlarged fragmentary vertical sectional view, taken on the line 3--3 of FIG. 2; and 
     FIG. 4 is a transverse vertical sectional view, with portions of the seal broken away, taken on the line 4--4 of FIG. 3. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in the drawings, a wall box generally designated by the reference numeral 1 is mounted in the side wall 3 of a boiler having a plurality of tubes, not shown, contained therein. 
     The wall box 1 includes a housing 5 provided with an outer wall 7 and an inner wall 9 fixedly mounted in the furnace wall 3. A partition 11 provided with a central opening 13 divides the interior of the wall box housing 5 into an inner annular chamber 15 and an outer annular chamber 17. The outer wall 7 is provided with an opening 19 of substantially the same diameter as central opening 13 while the inner wall 9 is provided with an opening 21 somewhat larger in diameter than the openings 13 and 19. 
     A first seal member 23 mounted in the openings 13 and 19 has an outer peripheral wall 25 which is a close sliding fit in these openings. The first seal member 23 includes an integral, radially extending flange 27 secured to the outer wall of the wall box housing 5 by a plurality of threaded fasteneres 29. 
     The first seal member 23 is provided with an annular recess 31 on its inner surface located between the inwardly extending annular shoulder 33 and the inwardly extending annular shoulder 35. A plurality of openings 37 extend through the wall of the first seal member 23 and open into the annular recess 31 thereby providing communication between the annular chamber 17 and the interior of the first seal member 23. The annular shoulder 35 is a littler larger in diameter than the annular shoulder 33 which initially is a close fit around the tubular slag blower or lance tube 38 and provides a seal for the slag blower as it rotates and slides therethrough. A pipe 39 threaded into the wall box housing 5 connects the annular chamber 17 to a source of fluid under pressure, not shown, such as air, steam or the like. 
     The outer surface 42 of the radial flange 27 is smooth and planar and the threaded fasteners 29 are arranged in a circle and are spaced radially outwardly from the central opening 41 of the flange 27 so as to provide an annular, radially extending, planar surface 43 extending for a substantial distance radially outwardly of the central opening 41. 
     A second seal member 45 is disposed contiguous with the radially extending, planar surface 43 of the first seal member 23. The second seal member 45 comprises a split annular ring 47 having parallel inner and outer surfaces 49 and 51 respectively. The inner diameter 53 of the annular seal ring 47 is substantially the same as or only slightly larger than the outer diameter of the slag blower or lance tube 38 adapted to be inserted therethrough. 
     The split annular seal ring 47 is provided on its outer surface with an annular recess 55 and is divided on its diameter into two equal parts 57 and 59. A tension type garter spring 61 is disposed in the annular recess 55 and secures the two parts of the annular ring together. 
     A thrust ring 63 having a central opening 65 and a planar inner surface 67 disposed normal to the axis of the central opening is carried by the outer wall 7 of the wall box housing 5 by means of threaded fasteners 69. These fasteners, which extend through openings in the thrust ring and are screwed into threaded jack screw openings 70 formed in the radial flange 27, are spaced radially outward of the central opening 65 to provide a radially extending, annular, planar surface 72 contiguous with the outer surface 51 of the second seal ring 47. 
     The inner planar surface 67 of the thrust ring 63 is spaced from the planar surface 43 of the radial flange 27 by the heads 71 of the threaded fasteners 29. These heads space the opposed planar surfaces of thrust ring 63 and of radial flange 27 apart by a distance which is slightly greater than the distance between the parallel faces or surfaces 49 and 51 of the annular seal ring 47 so that the seal ring may float or slide radially. 
     An annular member 73 disposed within the wall box housing 5 and extending from the inner wall 9 to the partition 11 forms an inner wall for the annular chamber 15. The annular member 73 is provided with a plurality of inclinded openings 75 which connect the annular chamber 15 with the interior passage 77 of the wall box seal through which the lance or slag blower 38 extends. A supply pipe 81 threaded into the wall box housing 5 is connected with a source of fluid under relatively high pressure, not shown, for supplying fluid to the annular chamber 15 for projection through the openings 75. 
     In operation, the tubular slag blower or lance 38 is rotated and advanced into the boiler through the seals 33 and 45 of the wall box 1 while compressed air or other suitable cleaning fluid supplied through the tubular slag blower or lance 38 to the nozzles 83 is discharged therefrom against the boiler tubes for removing soot and the like from their surfaces. At the same time compressed air is supplied to annular chamber 17 through the pipe 39 and, if desired, to the annular chamber 15 through the pipe 81. 
     The compressed air supplied to annular chamber 17 is furnished under greater pressure than the pressure within the boiler and continually flows between the outer surface of the slag blower 38 and the inner surface of the annular shoulder 35 of the first seal member 23 and into the interior of the boiler thereby assisting in preventing the escape of soot of other combustion material from the interior of the boiler past the seals 33 and 45 to the exterior thereof. 
     The inner surface 53 of the split annular ring 47 is held in sealing engagement with the exterior surface of the tubular slag blower 38 by the garter spring 61 as the slag blower rotates and advances and retracts. The second seal member 45 may also float or move radially to accomodate radial movement of the tubular slag blower 79 and a radial seal will be provided as the inner parallel surface 49 of the annular ring 47 slides against the outer planar surface 43 of the radial flange 27. 
     The compressed air furnished to the annular chamber 15 through the supply pipe 81 is projected toward the interior of the boiler through the openings 75. This air is under a pressure substantially greater than that present within the boiler and assists in preventing soot and other products of combustion from passing from the boiler interior outwardly toward the seals 33 and 45 of the wall box. 
     The floating seal 45, which provides an annular seal with the exterior surface of the tubular slag blower member as well as a radial seal with the fixed planar surface 43, in combination with the seal 33 substantially prevent the escape from the boiler of any soot or other combustion products through the wall box. If desired, resilient means such as a spring or springs, not shown, may be installed between the outer surface 51 of the seal ring 47 and the inner surface 67 of the thrust ring 63 for biasing the surface 49 of the floating seal ring against the fixed surface 43 of the flange 27. 
     While a typical first seal means is shown incorporated in the wall box, it would be obvious to one skilled in the art that the present second floating seal could be employed with wall boxes incorporating other types of first seal means.