Abstract:
A power boiler tube removal tool assembly is provided with co-operating shear block cavity, shear blade, and anvil elements that function to shear and inwardly bend gap metal in a boiler tube flared-end segment to thereby facilitate subsequent boiler tube flared-end segment peeling, crushing, and withdrawal steps that complete tube end removal from retention within a boiler drum wall.

Description:
CROSS-REFERENCES 
     None. 
     FIELD OF THE INVENTION 
     This invention pertains generally to power boilers, and specifically concerns apparatus that is particularly useful in connection with the maintenance removal of selected installed boiler tubes for subsequent replacement 
     BACKGROUND OF THE INVENTION 
     Experience in connection with the removal of water-tubes and fire-tubes from within power boilers for replacement using a tube-end gap-cutting tool of the type disclosed and claimed in U.S. Pat. No. 5,893,209 granted to Weeks et al. has shown that because of depth-of-cut procedural limitations that may be in effect to avoid possible drum wall damage, or sometimes because of gap-cutting tool construction characteristics, sufficient gap metal in a remaining boiler tube end segment is not removed in the initial longitudinal gap cutting operation and particularly at the tube segment flared end. In some instances little or not flared-end metal at the gap location is initially removed using the known gap-cutting tool. 
     In order to properly accomplish preparation of a retained boiler tube flared-end segment for subsequent final gap metal removal steps of “peeling” and “crushing”, I have devised a novel tool, sometimes called a “nipper” tool, that properly shears and bends to-be-removed gap metal in the boiler tube flared end to thereby complete the preliminary formation of the tube gap without damaging or removing metal from the co-operating boiler tube drum wall. 
     Other objects and advantages of the present invention will become apparent from a consideration of the descriptions, drawings, and claims which follow. 
     SUMMARY OF THE INVENTION 
     The present invention is basically comprised of a tool head subassembly provided with a rigid frame, an anvil and co-operating shear blade that is pivotally carried by the frame and engaged with a boiler tube flared end, a reciprocating cam that causes pivoting of the tool assembly shear blade element, and with a reversible, pressurized fluid actuator subassembly that is supported by the tool head frame and that causes reciprocating movement of the tool head cam element. Operation of the actuator subassembly in a positive direction, following insertion of the tool head anvil in a cut boiler tube flared-end and engagement of the tool shear blade with the boiler tube end segment flare, causes the shear blade to be rotated to double shear and downwardly bend a portion of the lip of the tube flare that ultimately comprises an extension of the desired tube end segment longitudinal gap. The tool may then be conveniently removed from engagement with the boiler tube end segment by simple longitudinal rotation, and the reciprocating cam retracted in preparation for next use of the tool. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic vertical section of a water-tube power boiler illustrating the environment in which the tool of the present invention is typically utilized; 
     FIG. 2 is a section view taken at line  2 — 2  of FIG. 1; 
     FIG. 3 is a perspective view of a preferred embodiment of the “nipper” boiler tube removal tool of the present invention; 
     FIG. 4 is an exploded view of the boiler tube shear tool illustrated in FIG. 3; 
     FIG. 5 is an elevation section view of the FIG. 3 tool co-operating with a boiler tube flared end segment and in an initial operating condition; 
     FIG. 6 is a section view similar to FIG. 5 but illustrating the FIG. 3 tool after shearing and bending of tube flared end segment gap metal has been completed; 
     FIG. 7 is a section view taken at line  7 — 7  of FIG. 5; and 
     FIG. 8 is an enlarged view of a profile that is preferred for the invention shear blade element. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 schematically illustrates a power boiler  10  having multiple conventional boiler water-tubes  12  installed with their upper and lower flared ends co-operating with boiler steam and mud drums  14  and  16 , respectively. Burners  18  are typically fired by a carbonaceous fuel, and the resulting effluent gasses of combustion, following heat extraction for water and steam heating purposes, are exhausted from within power boiler  10  through chimney connections  20 . As with all power boilers, it is necessary from time to time to remove and replace one or more of individual boiler tubes  12  from within power boiler  10 , and such is basically accomplished by selected tubes first being cut at their ends adjacent the exterior wall metal of drums  14  and  16  for removal. The boiler tube flared-end shear tool  100  of the present invention pertains generally to the removal of the tube flared-end segments that are initially retained in the steam and mud drum peripheral walls and, as illustrated in FIG. 2, such tool is basically utilized from a position within the applicable boiler drum. 
     FIGS. 3 and 4 best illustrate the basic construction details of tool assembly  100 . (Not shown in the drawings, however, is the conventional system for supplying the flow of pressurized fluid, which may be either pressurized hydraulic fluid or compressed air, to the conventional bi-directional pressure actuator subassembly  102  included with tool  100 ). Tool assembly  100  includes, in addition to cylinder  104  and piston rod  106  of actuator subassembly  102 , a tool head subassembly  108  that is basically comprised of rigid frame element  110 , anvil block element  112  having shear cavity  114 , rotatable shear blade element  116  carried in anvil block element  112  by pivot shaft  118 , wear plate element  120  supported by frame  110  and extending from anvil block  112  to actuator subassembly  102 , and cam body  122  supported by wear plate  120  and connected to the piston rod element  106  for reciprocation. Referring to FIG. 8, it should be noted that an undercut relief  115  is formed in shear blade element  116  just behind a shear edge  117  formed thereof. A bending edge  119  is located adjacent and in front of shear edge  117 . Guide elements  124  and  126  are fixedly secured to opposite faces of cam body member  122 . A lug pin  128 , mounted in and projecting from opposite sides of the rear portion of shear blade element  116 , co-operates with the ways provided in guide elements  124  and  126  and causes rotation of shear blade element  116  about pivot pin  118  as cam body  122  and its included guide member  124  and  126  are reciprocated by actuator subassembly  102 . 
     Additionally, the upper surface  113   a  of the nose portion  113  of anvil block element  112  is advantageously provided with upwardly projecting locating lugs  130  (see FIGS.  4  and  7 ). Lugs  130  engage longitudinal gap edges previously cut in boiler tube segment  12  when nose  113  of shear block element  112  is properly inserted in that tube segment for the subsequent shearing and bending steps resulting from operation of actuator subassembly  102 . It may be observed that upper surface  113   a  of nose portion  113  projects forward of the shear edge  117  formed on shear blade element  116 . Thus, when actuator subassembly  102  advances cam body  122  to rotate shear blade element  116  about shaft  118 , shear edge  117  engages gap metal  121  at  121   a  inwardly of gap metal edge  121   b  to cause such gap metal to be sheared and bent downwardly about anvil edge  113   a . By causing shear blade element  116  to engage gap metal  121  inwardly of its outer edge  121   b , blade element is drawn into tube segment  12  thereby preventing blade element  116  from moving away from or backing out of engagement with tub segment  12 . This makes tool assembly  100  much easier to hold in position during the shearing and bending operation. Undercut relief  115  acts to receive the flared edge or end  121   b  of a tube segment  12  to prevent shear blade element  116  from engaging said flared edge prior to engagement with tube segment  12  at location  121   a.    
     As illustrated in FIG. 4, tool assembly  100  also includes tool head cover  132 , which is removably attached to frame member  110 , housing  134  for the power system direction control valve, and tool handle  136 . Components  134  and  136  are preferably removably attached to and carried by actuator subassembly  102 . Subassembly  102  is removably mounted on tool frame  110  by the conventional threaded fasteners designated  103 .