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This Application claims benefit of U.S. Provisional Application No. 60/146,353, filed Aug. 2, 1999, the entirety of such provisional application being incorporated herein by reference thereto. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to an insulated, gas tight door for use in high temperature industrial applications, such as on boilers, economizers, scrubbers, precipitators, bag houses, flue gas ducts, etc., and in particular, to door systems for selective catalytic reactor (SCR) systems. SCR systems use catalyst material held in containers to reduce nitrogen oxides from flue gas, such containers being periodically transported into and out of the SCR structure to replenish the catalyst as necessary. 
     Access doors for industrial applications have been patented and, for example, are disclosed in U.S. Pat. Nos. 4,574,973; 4,685,586; and 5,158,043. Such doors were initially developed to eliminate door leakage and cold spots, which could cause inside acid condensation and resulting corrosion, and to provide fast and adequate access for internal maintenance of such equipment. Other types of doors have since been developed to provide other features in different applications for flue gas. 
     However, a need exists for a door which provides a tight seal for a high temperature industrial application, such as for a SCR system, and which facilitates transport of equipment and supplies, such as containers of catalyst, into and out of such industrial application. 
     SUMMARY OF THE INVENTION 
     It is, therefore, the principal object of this invention to provide an industrial door system for high temperature applications. 
     Another object of the present invention is to provide a door system for a selective catalytic reactor (SCR) system. 
     A further object of the present invention is to provide a door system which can be readily installed on a casing wall and with a door opening having variances in the dimensions of such door opening. 
     A still further object of the present invention is to provide a door for an SCR system using a davit arrangement. 
     Yet another object of the present invention is to provide a door for a SCR system which allows for heavy catalyst containers to be transported into and out of a SCR structure. 
     Generally, the present invention includes an SCR catalyst door having a flat and somewhat flexible door plate with notches around the edge thereof for receipt of swing bolts which are attached to a door frame. The door plate may include interior insulation and is suspended from a davit assembly mounted on the casing wall of the SCR structure adjacent to the door. 
     A sealing gasket is provided around the perimeter of the door plate, such gasket being flexible to provide a tight seal of the door against the door frame, even upon the occurrence of some warpage of the SCR system casing wall and/or the door frame. Preferably, the sealing gasket is square in cross-section, and is comprised of braided ceramic material. Such gasket is seated between stainless steel retainers provided about the edges of the door plate. These gasket retainers are placed in a dove-tail pattern which accommodate the expansion of the gasket, once the gasket is compressed in a sealing relationship. By capturing such expanded portion of the gasket, the retainers reduce the likelihood that the gasket will work loose when the door is opened. 
     The lower edge of the door extends downwardly below the floor level of the SCR system floor, and the lower edge of the door opening is typically flush with the floors on the inside and outside of the SCR building. 
     The door is generally attached to exterior of the SCR casing, and because personnel, wheeled carts and other vehicles may be required to enter the opening of the SCR system periodically, a landing, or platform, typically extends outwardly from the exterior of the building adjacent the door. Such platform may include a well, or recess, along the lower edge of the door opening into which the lower edge of the door is received. 
     A problem arises, however, in that in order to swing the door open in a conventional manner, such as by using conventional hinges at the edge of the door, the door would only be able to move to the boundary of the recess and would thus be blocked from opening fully. Accordingly, the door of the present invention includes a davit assembly modified to allow the door to be easily lifted by a predetermined amount in order to rise upwardly and out of the recess, to therefore allow the door to swing over the platform to a fully open position. 
     Closing of the door is accomplished in the reverse manner by swinging the door over the recess, and then lowering it back into place with the davits such that the lower edge of the door extends into the recess, below floor height. The door is then resealed against the door frame. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing, as well as other objects of the present invention, will be further apparent from the following detailed description of the preferred embodiment of the invention, when taken together with the accompanying specification and the drawings, in which: 
     FIG. 1A is a perspective view of a door system constructed in accordance with the present invention, such door system being shown in a closed position; 
     FIG. 1B is a perspective view of a door frame for a door system constructed in accordance with the present invention, the door frame being shown prior to installation; 
     FIG. 2A is a front elevational view of a door system constructed in accordance with the present invention, with such door system being shown in a closed position; 
     FIG. 2B is a front elevational view of the door system shown in FIG. 2A, with such door being shown in an open position; 
     FIG. 3 is a sectional view taken along lines  3 — 3  of FIG. 2A showing the door in a closed position; 
     FIG. 4 is a sectional view taken along lines  4 — 4  of FIG. 2A showing the door in various positions between the open and closed positions; 
     FIG. 5A is a sectional view taken along lines  5 — 5  of FIG. 2A, showing the door in a closed position; 
     FIG. 5B is a sectional view taken along lines  5 — 5  of FIG. 2A, illustrating the door having been moved away from the door frame; 
     FIG. 5C is a sectional view taken along lines  5 — 5  of FIG. 2A, showing the door having been lifted out of a recess to a height above floor level; 
     FIG. 6 is a sectional view, with the parts cut away, of a gasket configuration constructed in accordance with the present invention; 
     FIG. 7 is a sectional view of a davit assembly constructed in accordance with the present invention; 
     FIG. 8 is a sectional view taken along lines  8 — 8  of FIG. 7; 
     FIG. 9 is a sectional view taken along lines  9 — 9  of FIG. 7; and 
     FIG. 10 is a sectional view taken along lines  10 — 10  of FIG.  7 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The accompanying drawings and the description which follows set forth this invention in its preferred embodiment. However, it is contemplated that persons generally familiar with door systems will be able to apply the novel characteristics of the structures illustrated and described herein in other contexts by modification of certain details. Accordingly, the drawings and description are not to be taken as restrictive on the scope of this invention, but are to be understood as broad and general teachings. 
     Referring now to the drawings in detail, wherein like reference characters represent like elements or features throughout the various views, the door system of the present invention is indicated generally in the figures by reference character  10 . 
     In FIG. 1A of the drawings, door system  10  is illustrated installed on a casing wall W of an SCR system, typically in the form of a building or other structure, generally S, having a door, generally  12 , with slots, or notches,  14  around the peripheral portions, or edges,  16   a ,  16   b ,  16   c , an  16   d  thereof. Received in the notches  14  are fasteners, such as swing bolts,  18  pivotally carried between ears  20  on pins  22  (FIGS.  5 A through  5 C), ears  20  being attached to a door frame, generally  24 . Door  12  is preferably constructed of steel, as is frame  24  (which defines doorway  25 )(FIG.  1 B), and includes lifting lugs  26 , as well as handles  28 , used during opening and closing of the door  12 . 
     As shown in FIGS. 5A through 5C, door  12  includes an outer door panel, or plate,  30 , and an inner door panel, or plate,  32  defining a compartment  34  therebetween. Insulation material  36  is provided in compartment  34 . 
     FIGS. 1A,  2 A,  2 B,  3 , and  7 , illustrate a davit assembly, generally  40 , is provided which pivots with respect to the SCR structure S. The davit assembly  40  includes a davit post  42  carried for pivoting movement by upper and lower davit support brackets,  44 ,  46 , respectively, such support brackets  44 ,  46 , being attached to a structural member of the SCR structure by brackets, generally  48 . A load bearing journal  50  and thrust washer  52  (FIG. 7) are provided for supporting davit post  42  for rotation with respect to lower bracket support  46 . Although thrust washer  52  is preferably stainless steel, it could be constructed of other suitable materials. A pin  57  (FIG. 9) fixes post  42  with respect to upper bracket  44 . 
     Davit assembly  40  includes a cantilever arm  54  attached to davit post  42  and also a support brace  56  connected between arm  54  and davit post  42 . Davit assembly  40  includes a jack mechanism, generally J, which could be of various designs, but which preferably includes a screw-type jack having a suspension rod, generally  58 , extending downwardly from arm  54 . The upper end  60  of suspension rod  58  is connected to arm  54 , as shown in FIGS. 7 and 8, via a nut  62  captured and restrained from movement between flanges,  64  and  66 . Preferably, nut  62  is welded to suspension rod  58  in order to prevent any relative rotation of suspension rod  58  with respect to arm  54 . A journal support bracket  68  is fixedly attached to outer door plate  34 , through which suspension rod  58  extends. Suspension rod  58  includes a threaded portion  70 , extending through a bracket, or yoke,  72 , and a suspension rod nut  74  are threadingly carried on suspension rod  58 . A washer  75  is interposed between nut  74  and yoke  72 . Nut  74  is prevented from becoming detached from rod  58 , preferably by welding the threads at the end of rod  58 . 
     During opening and closing of the door  12 , the weight of the door is borne by suspension rod nut  74 , such weight being transmitted by suspension rod  58  to the davit assembly  40 . Washer  75  and nut  74  are preferably bronze, although any other suitable material could be used. A safety chain  77 , also known as a fall chain, is connected between bracket  68  and arm  54  for restraining door  12  in the event of failure of rod  58  and/or yoke  72 . 
     Turning to FIG. 1A, door  12  is shown in a closed position for sealing the door opening O (FIG. 1B) of the SCR structure S. In the closed position, it can be seen that the lower edge  16   a  of the door  12  extends below door opening O, and also below the floor level SL (FIGS. 2A,  3 , and  5 A) of the SCR floor SF. The lower edge  16   a  of the door  12  is positioned within a well, or recess, generally R, in the platform, or landing, generally P, extending outwardly adjacent the SCR floor SF, such platform P having a floor PF typically being at generally the same floor level PL as is the floor level SL of the SCR floor SF. 
     Recess R, which extends at least the full width of door  12 , is provided in platform P, and is defined in part by the SCR system exterior wall W. 
     To open the door to an open position, such as shown in FIGS. 2B and 4, suspension rod nut  74  is first tightened to place suspension rod  58  in tension. Nuts  84  on swing bolts  18  are then loosened. Suspension rod nut  74  would then be further tightened on suspension rod  58 , which, because of the engagement of suspension rod nut  74  with the base  86  of yoke  72 , would cause a corresponding lifting of door  12 . This would raise door  12  upwardly from the position shown in FIG.  5 B. Once the door is raised such that the lower edge  16   a  is above the floor level PL of the platform P, the door  12  may be swung outwardly, such as by grasping handles  28 , and by pivoting of the arm  54  of davit assembly  40  to a position over the platform P, such as shown in FIG.  5 C. Continued pivoting of davit arm  54  causes a corresponding movement of the door  12  from the closed position, shown in FIGS. 1A,  2 A,  3 , and  5 A, to the open position shown in FIGS. 2B and 4. FIG. 4 illustrates the sequence of movement of the door  12  from the closed to the open position. 
     To close the door  12 , the davit assembly  40  is pivoted in the reverse direction until the door  12  is positioned above the recess R, and the inner plate or panel  32  of the door is adjacent the opening O of door frame  24 . The door  12  is then lowered by turning nut  74  in the reverse direction such that inner door panel  32  may be received in opening O. Plate  88  attached adjacent the lower edge  16   a  of door  12  is tapered and assists in the alignment and closing of door  12 . Once door  12  is in place for closure, swing bolts  18  are swung into place within the notches  14  of the door  12 , and nuts  84  reattached to the swing bolts  18 . 
     Although not shown, it is to be understood, of course, that instead of rotating nut  74  to raise and lower door  12 , the present invention could be modified such that rod  58  is captured by and rotates with respect to yoke  72 , and also with respect to nut  62 . In such a configuration, rod  58  itself would be turned in order to raise and lower door  12 . 
     Turning to FIGS.  1 B and  5 A- 5 C, door frame  24  includes a channel, generally  90 , extending about the periphery of frame  24 . After installation, channel  90  is preferably filled with refractory material  92 , after installation of the door frame  24 , for heat resistance purposes. The lower portion  94  of door frame  24  acts as a threshold and includes sill channel stiffeners  96  which are in place within channel portion  94  prior to pouring of the refractory material. After the refractory material is in place in the lower portion  94 , sill plates, generally  98 , are then preferably stitch welded to frame  24  to form a sill  100 , which in effect becomes an extension of the SCR system floor SF into frame  24 , the sill  100  being generally flush with floor SF. 
     An important feature of the present invention is the installation method of the frame  24  on the SCR structures. The frame includes vertical channel members, generally  102 , and horizontal channel members, generally  104 , each of which have a generally U-shaped cross section. Inner and outer flanges  106 ,  108 , respectively, are provided about the periphery of frame  24 , and the inner flanges  106  are of sufficient height to allow frame  24  to be fitted to a generally rough door opening O in the exterior or casing wall W of the SCR system S. Because of the height dimension of flanges  106 , once frame  24  is horizontally centered about door opening O, frame  24  can then be vertically adjusted in order to ensure the upper edge  107  of flange  106  is substantially level with the interior floor SF of the SCR structure. Once the door frame  12  is properly positioned, frame  24  is welded about its periphery to the SCR system structure. 
     Filler grates (not shown) or other structural members are provided within the platform recess R when the door  12  is open to allow for a generally smooth floor from the platform floor PF, through door opening O, and to the interior floor SF of the SCR structure S when the door  12  is open. There generally level surfaces through door opening O facilitate transport of equipment and supplies, such as containers of catalyst, into and out of SCR structure S. 
     Another feature of the present invention is the gasket arrangement, generally  110 , for the door  12 . A ceramic sealing gasket, generally  112 , is provided to prevent escape of hot gases from the SCR structure S. Gasket  110  is of a generally square cross section and is preferably made of braided ceramic material. Note vertical portions of gasket  112  on door  12  are represented in the figures by crosshatched portions  112   a . Gasket  112  could be of several types, but one suitable gasket is a square braided, ceramic gasket manufactured by Unifrax Corp. of Niagara Falls, N.Y. 
     Retainers  114  are attached about the periphery of the interior portion of door panel  32 , and preferably such retainers  114  are of stainless steel and form a channel  118  having a dovetail-shaped cross section. The dovetail cross section allows for expansion of the gasket  112 , once the gasket  112  is compressed by door  12  in a sealing relationship against door frame  24 , such as when the door  12  is in the closed position. By capturing such expanded portion of the gasket  112 , the retainers  114  reduce the likelihood that gasket  112  will work loose and fall out during repeated opening and closing of the door  12 . 
     One advantage of the present invention is that door system  10  can be installed without regard for left or right hinges for the door. Door system  10  can be installed to open to the left, or installed to open to the right, using identical parts and components with no customization being required. 
     While preferred embodiments of the invention have been described using specific terms, such description is for present illustrative purposes only, and it is to be understood that changes and variations to such embodiments, including but not limited to the substitution of equivalent features or parts, and the reversal of various features thereof, may be practiced by those of ordinary skill in the art without departing from the spirit or scope of the following claims.

Summary:
A high temperature industrial door having a flexible door plate with notches about the periphery thereof for receipt of swing bolts. The door plate includes interior insulation and is suspended from and hinged to a door frame using a davit assembly. In the closed position, the lower edge of the door extends below floor level. To open the door, the davit assembly allows the door to be lifted above floor level and moved to an open position, by pivoting of the davit assembly.