Patent Abstract:
Disclosed herein is a novel pivot pin assembly  410, 420 430, 600  for pivotally attaching nozzle tips  200  to stationary nozzles in a solid fuel furnace. The pivot pin assemblies allow rapid replacement of the nozzle tips  200.  The pivot pin assembly  410, 420 430, 600  employs fasteners that or recessed or have an aerodynamically shaped head  610.  The head  610  includes a leading edge  613  and optionally a trailing edge  615  that are aerodynamically shaped to reduce corrosion and erosion. The pivot pin assembly pivotally attaches the nozzle tip  200  to the stationary nozzle  110.  It employs fasteners that are accessible from a furnace side through a central opening of the nozzle tip  200.  This allows removal of the nozzle tip  200  from inside the furnace greatly simplifying nozzle tip  200  replacement.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation-In-Part of U.S. Ser. No. 12/618,031 “PIVOT PIN FOR FURNACE SIDE REMOVAL” by Briggs et al., filed Nov. 13, 2009 and claims priority from this application. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    This disclosure relates to burners of solid fuel fired furnaces and more specifically to a burner nozzle tip design that allows for easier removal and maintenance. 
         [0004]    2. Discussion of Related Art 
         [0005]    Solid fuel furnaces have many common uses, such as for firing boilers to produce steam and electricity. The solid fuel typically is pulverized coal. Coal particles of the pulverized coal is entrained in a flowing air stream and blown into a combustion chamber of a furnace where it is burned. 
         [0006]      FIG. 1  is a schematic depiction of a fuel firing compartment  100  of a typical solid fuel fired furnace.  FIG. 2  is a side elevational view showing a cross section of the nozzle, nozzle tip, and pivot pin shown in  FIG. 1 . 
         [0007]    The invention will be described with reference to both  FIGS. 1 and 2 . It can be seen here that stationary nozzle  110  receives sold fuel particles entrained in a stream of flowing air. The air/fuel flows through the stationary nozzle  110  and out of the nozzle tip  200 . The air/fuel is then burned in the combustion chamber of a solid fuel furnace. The direction following the flow is referred to as “downstream” and the opposite direction is referred to as “upstream”. 
         [0008]    In order to adjust the operation of the nozzle tip  200 , one or more control arms, shown here as a tilt pivot  120  and a tilt drive  130 , adjust the orientation and operation of the nozzle tip  200 . The nozzle tip  200  may be tilted with respect to the stationary nozzle  110  on a pivot pin  310  to cause the nozzle tip  200  to be directed in a different direction to optimize the firing of the furnace. 
         [0009]    Since the air flow with entrained solid particles passes through the fuel-firing compartment  100  subject to erosion effects similar to sand blasting. Anything within the path of the air/fuel flow is eroded. 
         [0010]    Since the nozzle tips  200  are located in the combustion chamber, they are also exposed to excessive heat and heat cycling. This can overheat and warp the nozzle tips, and have effects on the moving parts, such as pivot pin  310 . 
         [0011]    Combustion occurring near the nozzle tips  200  creates constant expansion, contraction and vibration. If the pivot pin is held in place with standard bolts or nuts, it is possible that they will loosen and vibrate out. This would cause the nozzle tip  200  to fall into the furnace. The furnace has a grinder for grinding up the ashes at the bottom of the furnace. Not only will there be uneven and uncontrolled burning, but the nozzle tip, bolt and nut will become caught in the grinder causing damage and the boiler to become non-operational. This would require time and expense to correct the problem. 
         [0012]    For this reason, one end of the pivot pin is typically welded into place. The pins must be ground off to replace them. The inside of the furnace is covered with water tubes that pass close to each of the nozzle tips  200 . Therefore, the only way to replace the nozzle tips is to grind or burn off the pivot pins from inside of the nozzle tips  200 . There is little access to the nozzle tip  200  openings, making replacement difficult. 
         [0013]    The entire fuel firing compartment, except for the nozzle tip  200  is located within a closed windbox compartment (not shown for clarity in  FIG. 1 ). The common method of changing the nozzle tips  200  is to remove the entire fuel firing compartment  100  from the windbox and grind off the pivot pins from the outside of the nozzle tips  200 . This is very time-consuming causing the power plant to be ‘down’ for quite a while. 
         [0014]    Typically these solid fuel furnaces are used as steam generators to create electricity in power plants. When one of these power plants is ‘down’, the owner is required to buy and supply equivalent power from the power grid to provide an uninterrupted supply of electricity to its customers. 
         [0015]    Buying this replacement electricity is much more expensive that generating it. This may amount to significant losses by being out of operation. Therefore, a significant part of the costs are ‘down time’ costs. 
         [0016]    Since nozzle tip operate at very high temperatures and in an erosive environment, the nozzle tips  200  tend to have a short life relative to the other parts of the system and have to be replaced often. 
         [0017]    Since the nozzle tips  200  typically require more maintenance then the remainder of the fuel firing compartment parts, it would be beneficial to be able to quickly and easily replace only the nozzle tip  200 . This then results in a furnace that is less costly to operate and service. 
       SUMMARY 
       [0018]    The present invention may be embodied as a replaceable nozzle tip assembly  250  within a solid fuel furnace having a stationary nozzle  110 . The nozzle tip assembly  250  includes a nozzle tip  200  having with shroud walls  210 ,  220  and a central opening  230 . 
         [0019]    A bearing  510 ,  520 ,  530  is fixed to the shroud walls  210 ,  220 . The bearing  510 ,  520 ,  530  has a central orifice  511 ,  521 ,  531 . 
         [0020]    A pivot pin assembly  410 ,  420 ,  430  passes through the bearing orifice  511 ,  521 ,  531  and the sidewall of the stationary nozzle  110 , to pivotally and removeably attach the nozzle tip  200  to the stationary nozzle  110 . The pivot pin assembly  410 ,  420 ,  430  acts as a fastener that is accessible from the central opening  230 . This allows easy replacement of the nozzle tip. 
         [0021]    The present invention may also be embodied as a nozzle tip assembly  250  removeably attached to a stationary nozzle of a solid fuel furnace. 
         [0022]    The nozzle tip assembly  250  includes a nozzle tip  200  having at least one outer shroud wall  210 ,  220  and at least one central opening  230 . 
         [0023]    A bearing  510 ,  520 ,  530  with a bearing orifice  511 ,  521 ,  531  is attached to the shroud wall  210 ,  220  of the nozzle tip  200 . 
         [0024]    A fastener base  413 ,  423 ,  433  is fitted into the bearing orifice  511 ,  521 ,  531  and extends at least partially through a sidewall of the stationary nozzle  110  allowing the stationary nozzle  110  to pivot relative to the fastener base  413 ,  423 ,  433  and nozzle tip  200 . 
         [0025]    A set screw  411 ,  421 ,  431  is used to secure the fastener base  413 ,  423 ,  433  to the bearing  510 ,  520 ,  530 , the set screw  411 ,  421 ,  431  being accessible from the central opening  230  of the nozzle tip  200 . 
         [0026]    The invention may also be embodied as an aerodynamic pivot pin assembly  600  passing through a surface of a shroud  210  of a nozzle tip  200  for pivotally securing a nozzle tip  200  to a nozzle, having a head  610  inside of the nozzle tip  200 , wherein the head  610  has decreasing thickness “t” from a top  619  to a leading edge  613  to minimize resistance to flow and erosion of head  610 . 
         [0027]    The head  610  may also be designed to decrease in width in a lateral dimension as it extends upstream to further minimize resistance to flow and erosion of head  610 . 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0028]    With reference now to the figures where all like parts are numbered alike; 
           [0029]      FIG. 1  is a perspective view of a fuel firing compartment showing a nozzle tip and a pivot pin. 
           [0030]      FIG. 2  is a side elevational view showing a cross section of the nozzle, nozzle tip, and pivot pin of  FIG. 1 . 
           [0031]      FIG. 3  is a perspective view showing the inside of the nozzle tip of  FIGS. 1 ,  2  with an exploded diagram of a pivot pin assembly according to the present invention. 
           [0032]      FIG. 4  is an enlarged view of a portion of the nozzle tip and pivot pin assembly of  FIG. 3 . 
           [0033]      FIGS. 5-7  are exploded perspective views of three different embodiments of a pivot pin assembly according to the present invention. 
           [0034]      FIG. 8  is a partial view of a nozzle tip  200  from the furnace side showing another embodiment of a pivot pin assembly, as it would appear installed. 
           [0035]      FIG. 9  is a perspective view showing the curvature of the outside surface of the head of the pivot pin according to one embodiment of the present invention. 
           [0036]      FIG. 10  is a perspective view showing the inner side of the head of the pivot pin of  FIG. 9 . 
           [0037]      FIG. 11  shows a top plan view of the pivot pin shown in  FIGS. 9 and 10 . 
           [0038]      FIG. 12  is a side elevational view of the pivot pin of  FIGS. 9-11 . 
           [0039]      FIG. 13  is a front elevational view of the pivot pin of  FIGS. 9-12 . 
           [0040]      FIG. 14  is a bottom plan view of the pivot pin of  FIGS. 9-13 . 
           [0041]      FIG. 15  is a partially cut-away view of the nozzle tip assembly of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0042]    The use of the terms “a” and “an” and “the” and similar references in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. 
         [0043]    The most direct way of replacing a nozzle tip  200  would be from the furnace side, if the pivot pin were not welded. 
         [0044]    The inside of the furnace is covered with water pipes for collecting the heat and for creating steam. These burners may be many feet from the bottom of the furnace. Therefore, temporary scaffolding must be erected to allow access to the nozzle tips  200 . This may be acceptable for light work, but any more involved work may cause accidents that would damage the water pipes and other equipment inside of the furnace. For this reason, it was common to work on the other side of the windbox and remove the entire fuel-firing compartment  100  for maintenance. 
         [0045]    The present invention allows for easier and more economical replacement of the nozzle tips  200 . A new pivot pin assembly design is used instead of the welded pivot pin design for holding the nozzle tip  200  in place. This new design allows for the pivot pin removal and installation from inside the furnace without grinding or cutting. 
         [0046]      FIG. 3  is a perspective view showing the inside of the nozzle tip  200  of  FIGS. 1 ,  2  with an exploded diagram of a pivot pin assembly  410  according to the present invention. Nozzle tip  200  has an outer shroud  220  that encloses an inner shroud  210 . Pivot pin assembly  410  passes through the stationary nozzle (not shown here for clarity), the inner shroud  210  and the outer shroud  220 . This allows nozzle tip  200  to pivot with respect to the stationary nozzle ( 110  of  FIGS. 1 ,  2 ). 
         [0047]    The pivot pin assembly  410  remains the same size as the pivot pin  310  currently being used. The pivot pin assembly  410 , however, is manufactured to allow it to be removeably held in place using a fastener that is protected from the hazardous conditions. 
         [0048]      FIG. 4  is an enlarged view of a portion of the nozzle tip and pivot pin assembly  410  of  FIG. 3 . In addition to the inner shroud  210 , the outer shroud  220  and the pivot pin assembly  410 , a portion of a bearing  510  is visible. 
         [0049]      FIGS. 5-7  are perspective views of three different embodiments of a pivot pin assembly  410 ,  420 ,  430  according to the present invention that attach to bearings  510 ,  520 ,  530  in the nozzle tip.  FIG. 5  shows a bearing  510  having an inner extension  515  that fits within the inner shroud ( 210  of  FIG. 4 ), and a bearing body  517  that is sandwiched between the inner and outer shrouds ( 210 ,  220  of  FIG. 4 ). Bearing  510  has a bearing orifice  511  that passes through the bearing  510 . 
         [0050]    A fastener base  413  has a cylindrical portion  415  and an expansion portion  417 . The expansion portion  417  in its normal resting position is slightly larger diameter than bearing orifice  511 . Expansion portion  417  has slits allowing it to be squeezed to make it thinner or released to expand back to make it thicker. The expansion portion  417  also has a snap ridge  419  that protrudes outward from the expansion portion  417 . Bearing  510  also has a snap groove  513  that is designed to receive and removeably hold snap ridge  419 . Cylindrical portion  415  extends outward enough to pass through a sidewall of stationary nozzle ( 110  of  FIGS. 1 ,  2 ). Cylindrical portion  415  will be flush with respect to the inner surface of the sidewall of the stationary nozzle. (In an alternative embodiment, it may extend only partially through the stationary nozzle and be slightly recessed.) This insures that it will not be abrased away by the flowing air/fuel. 
         [0051]    For assembly, fastener base  413  is pushed into bearing orifice  511 . The leading edge of the extension portion  417  is preferably tapered to the center so as to squeeze expansion portion  417  together making it thinner until snap ridge  419  snaps into snap groove  513 , holding fastener base  413  in place. 
         [0052]    A set screw  411  has a threaded head section  412  and a body section. It is inserted into the fastener base  413  after the fastener base  413  has been inserted into bearing orifice  511 . The body section restricts the expansion section  417  from reducing its thickness and prevents the snap ridge  409  from being removed from the snap groove  513 . The head section  412  is threaded to thread into the outer end of the fastener base  413 . 
         [0053]      FIG. 6  is a second embodiment of the pivot pin assembly according to the present invention. Bearing  520  has a bearing body  527  sandwiched between the inner and outer shrouds ( 210 ,  220  of  FIG. 4 ) of the nozzle tip when installed. A fastener base  423  has a cylindrical portion  425  and an insertion portion  427 . The insertion portion  427  is inserted into the bearing orifice  521 . Insertion portion  427  is shown here with a square cross sectional shape in this embodiment, however, any geometrical or irregular shaped cross section shape would be acceptable which matches the shape of the bearing orifice  521 . 
         [0054]    A set screw  421  passes through the fastener base  423  and screws into a threaded section fixed within bearing  520 . This may be a threaded nut (not shown) welded within bearing orifice  521 . The shape of insertion section  427  fitting snugly within bearing orifice  521  stops rotation of fastener base  423  restricting loosening of set screw  421 . 
         [0055]    A screw cap  429  threads into fastener base  423  thereby providing a corrosion-tight barrier protecting set screw  431  and fastener base  423 . This screw cap  429  acts as a plug on the stationary coal nozzle side to seal the inner area from coal intrusion and wear. This also acts to jam against set screw  421  and acts as a lock nut in case set screw  421  begins to loosen. 
         [0056]    In an alternative embodiment, cylindrical section  425  of fastener base  423  has internal threads. A screw cap similar to screw cap  429  may be employed and screwed into this cylindrical section  425  to protect fastener base  423  and prevent set screw  421  from loosening. 
         [0057]    Cylindrical portion  425  extends outward enough to pass through a wall of the stationary nozzle ( 110  of  FIGS. 1 ,  2 ), but it and screw cap  429  will be flush with respect to the inner surface of the stationary nozzle. In an alternative embodiment, they may extend only partially through the sidewall of the stationary nozzle and be slightly recessed. This insures that it will not be abrased away by the flowing air/fuel. 
         [0058]      FIG. 7  shows a bearing  530  having a bearing body  537  that is sandwiched between the inner and outer shrouds ( 210 ,  220  of  FIG. 4 ) of the nozzle tip when installed. Bearing  530  has an inner extension  535  that fits within the inner shroud ( 210  of  FIG. 4 ), an outer extension  539  that fits within outer shroud ( 220  of  FIG. 4 ) and a bearing body  537  that is sandwiched between the inner and outer shrouds ( 210 ,  220  of  FIG. 4 ). Bearing  530  has a bearing orifice  531  that passes through the bearing  530 . 
         [0059]    A fastener base  433  has a cylindrical portion  435  and an expansion portion  437 . The expansion portion  437  in its normal resting position has a diameter slightly smaller than bearing orifice  531 . Expansion portion  437  has slits allowing it to be expanded to make it thicker. 
         [0060]    Cylindrical portion  435  extends outward enough to pass through a wall of the stationary nozzle ( 110  of  FIGS. 1 ,  2 ), but will be flush with respect to the inner surface of the stationary nozzle sidewall. In an alternative embodiment, it may extend only partially through the stationary nozzle and be slightly recessed. This insures that it will not be abrased away by the flowing air/fuel. 
         [0061]    A set screw  431  has threads at one end. It is inserted through the fastener base  413  and loosely screwed into the narrower end of a truncated cone shaped expander  438 . 
         [0062]    The set screw  431 , fastener base  433 , and expander  438  are inserted into bearing orifice  531 . Set screw  431  is then tightened causing expander  438  to be pulled toward set screw  431  thereby expanding expansion portion  437 . Expansion portion  437  then becomes tightly held within bearing orifice  531 . 
         [0063]    A screw cap  439  is screwed into this cylindrical section  435  to protect fastener base  433  and prevent set screw  431  from loosening. 
         [0064]    Even though a set screw is described in this embodiment, it is appreciated that the invention covers all types of removable fasteners that will allow the nozzle tip to pivot about the stationary nozzle, and be accessed from the furnace side of the nozzle tip. 
         [0065]    As opposed to the prior art designed, with the present invention, a worker will not have to cut out material to replace the nozzle tip. No welding is required to install the present invention. 
         [0066]    The present invention is designed to use existing holes in the stationary nozzle and nozzle tips  200 . The embodiment of  FIG. 7  also allows use of the existing bearing block sizing. In this embodiment, no new design sizing is required. 
         [0067]    The present invention may be used to retrofit any existing ‘T fired’ nozzle types. The pivot pin assembly is sealed from wear. Since it attached with fasteners, it may be replaced with hand tools. No special rigging is required. 
         [0068]    Even though this invention has its preferred use for solid fuel burner nozzle tips, and more specifically coal-fired burner nozzle tips, it is equally applicable to other nozzle tips that are intended to pivot and are located inside of a furnace. These may be oil burner nozzle tips, natural gas burner nozzle tips, other fuel gas nozzle tips and air inlet tips. 
         [0069]      FIG. 8  is a partial view of a nozzle tip  200  from the furnace side showing a head  610  of a second embodiment of a pivot pin assembly  600 , as it would appear installed. 
         [0070]    A curved head  610  of the pivot pin assembly  600  is visible fitting flush against the surface of the inner shroud  210  of nozzle tip  200 . 
         [0071]      FIG. 9  is a perspective view showing the curved head of a pivot pin  601  of the pivot pin assembly according to one embodiment of the present invention. 
         [0072]      FIG. 10  is a perspective view showing the inner side of the head of the pivot pin of  FIG. 9 . 
         [0073]      FIG. 11  shows a top plan view of the pivot pin shown in  FIGS. 9 and 10 . 
         [0074]      FIG. 12  is a side elevational view of the pivot pin of  FIGS. 9-11 . 
         [0075]      FIG. 13  is a front elevational view of the pivot pin of  FIGS. 9-12 . 
         [0076]      FIG. 14  is a bottom plan view of the pivot pin of  FIGS. 9-13 . 
         [0077]    The pivot pin  601  is now described in connection with  FIGS. 9-14 . 
         [0078]      FIGS. 9 and 12  show a pin axis  603  passing through the length of the shaft  650 . Also, the indications of the upstream and downstream directions are shown, as well as the lateral direction. 
         [0079]    In this embodiment, the pivot pin  601  includes a shaft  650 . The shaft  650  fits through an orifice of a bearing held by the at least one of the shrouds similar to the embodiment shown in  FIG. 4  or the other previously described embodiments. In this embodiment, the shaft  650  has a hole  652  that receives a clip, pin or other fastener on the other side of the shrouds, holding the pivot pin  601  in place. 
         [0080]    Pivot pin  601  has a flat inner surface  620  on head  610  that fits flush against the inner shroud ( 210  of  FIG. 8 ). The inner surface  620  also has an alignment peg  622  that fits into a corresponding hole in the inner shroud such that the pivot pin head is oriented to have a portion of the head  610  point upstream, a leading edge  613 , and a portion face downstream, a trailing edge  615 . 
         [0081]      FIG. 9  shows the surface of the head  610 . It is shaped to be aerodynamic with the head  610  being narrow at the leading edge  613 , and increasing to a head thickness “t” at the top  619 . It is curved, or angled to divert flow outward away from the inner shroud surface and around head  610  as shown by arrow “A” in  FIG. 12 . 
         [0082]    It may also be designed to divert flow laterally around head  610  as show by arrows “B” in  FIGS. 11 and 14 . 
         [0083]    Similarly, to reduce turbulence and abrasive swirling effects, the trailing edge  615  is designed to continue the smooth flow around the head  610  and downstream. In  FIG. 12 , the thickness of head  610  decreases from a maximum at the top  619  to a smaller thickness at the trailing edge  615 . This causes the flow to follow arrow “C”. 
         [0084]    The trailing edge  615  may also be aerodynamic in the other dimension. As shown in  FIG. 14 , the trailing edge  615  is rounded causing the flow to follow arrows “D”. It is to be understood that other aerodynamic shapes may also be advantageously used for the pivot pin head  610 . 
         [0085]    The gradual redirection of the flow around the head  610  minimized abrasion and erosion of the head. This allows these to function longer before replacement. 
         [0086]      FIG. 15  is a partially cut-away view of the nozzle tip assembly of  FIG. 8 . Here, a clip  653  which fits through the hole of the pin shaft ( 652 ,  650  of  FIGS. 9 ,  10 ,  12 ,  13 , respectively). 
         [0087]    Since these are design for quick replacement from inside the furnace, they are easily replaced when required. 
         [0088]    While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention.

Technology Classification (CPC): 5