Replaceable Wear Plates for Use with Blind Shear Rams

Abstract

A shear ram assembly including upper and lower ram blocks having blades positioned on opposing sides of pipe and other, more ductile items, and arranged to close around and shear the pipe and the more ductile items. The shear ram assembly includes pipe guide arms attached to the upper ram block and configured to guide pipe and other items into the path of the blades, and to be received by recesses in the lower ram block. Also included are wear plates mounted on top of the pipe guide arms and positioned to force the lower ram block to rise as the arms enter the recesses, thereby causing the gap between the blades to decrease so that the blades can better shear the more ductile items.

What is claimed is: 
     
         1 . A shear ram assembly for shearing a pipe and ductile items, comprising:
 first and second ram blocks positioned adjacent the pipe and ductile items, and on opposite sides thereof, the first and second ram blocks arranged to close around the pipe and ductile items;   first and second blades attached respectively to the first and second ram blocks and positioned so that as the first and second ram blocks close around the pipe and the ductile items, the blades pass over one another and shear the pipe and the ductile items;   at least one recess in the second ram block;   at least one arm attached to the first ram block that inserts into the at least one recess when the first and second ram blocks close; and   at least one plate positioned on the at least one arm, so that when the arm inserts in to the at least one recess, the wear plate slides against a surface of the recess and orients the blades at a maximum distance apart.   
     
     
         2 . The shear ram assembly of  claim 1 , wherein the blades are separated by a distance of about 0.003 inch to about 0.008 inch when closed. 
     
     
         3 . The shear ram assembly of  claim 1 , wherein the wear plates are attached to the arms by a means selected from the group consisting of welding, adhering, and fastening with mechanical fasteners. 
     
     
         4 . The shear ram assembly of  claim 1 , wherein a distance from a lower surface of the first blade to an upper surface of the wear plate exceeds a distance from a lower facing surface of the recess to an upper surface of the second blade by a designated amount. 
     
     
         5 . The shear ram assembly of  claim 1 , wherein the edges of the recesses are chamfered to allow the wear plates to enter the recesses as the upper and lower ram blocks close. 
     
     
         6 . The shear ram assembly of  claim 1 , wherein the edges of the wear plates are chamfered to allow the wear plates to enter the recesses as the upper and lower ram blocks close. 
     
     
         7 . The shear ram assembly of  claim 1 , wherein the blade of the upper ram block is attached to a forward end of the upper ram block, and has a face, an upper edge, and a lower edge, and wherein the lower edge extends farther forward from the forward end than the upper edge, so that the face is inclined relative to the forward end of the upper ram block. 
     
     
         8 . The shear ram assembly of  claim 7 , wherein the blade of the upper ram block has outboard ends that extend farther forward from the forward end than a central portion of the blade, so that the face of the blade has a generally concave configuration. 
     
     
         9 . The shear ram assembly of  claim 1 , wherein the arms are attached to the upper ram block by means selected from the group consisting of welding, adhering, and mechanical fasteners. 
     
     
         10 . The shear ram assembly of  claim 1 , wherein the arms are integral with the upper ram block. 
     
     
         11 . A shear ram assembly for shearing a pipe and ductile items, comprising:
 first and second ram blocks, each having a blade, and the second ram block defining a recess positioned laterally with respect to the blades, the first and second ram blocks positioned on opposite sides of the pipe and the ductile items, and such that one slides over the other when the first and second ram blocks are moved forward to a closed position, thereby shearing the pipe and the ductile items;   a guide arm protruding from the first ram block toward the second ram block and positioned to enter the recess when the first and second ram blocks close, and   a wear plate attached to an upper surface of each guide arm that selectively engages an upper surface of the recess to raise the second ram block upward relative to the first ram block so that any gap between the blades is reduced.   
     
     
         12 . The shear ram assembly of  claim 11 , wherein the gap between the blades is about 0.003 inch to about 0.008 inch when closed. 
     
     
         13 . The shear ram assembly of  claim 11 , wherein the wear plates are attached to the arms by a means selected from the group consisting of welding, adhering, and fastening with mechanical fasteners. 
     
     
         14 . The shear ram assembly of  claim 11 , wherein the wear plates are integral with the arms. 
     
     
         15 . The shear ram assembly of  claim 11 , wherein the edges of the recesses are chamfered to allow the wear plates to enter the recesses as the upper and lower ram blocks close. 
     
     
         16 . The shear ram assembly of  claim 11 , wherein the edges of the wear plates are chamfered to allow the wear plates to enter the recesses as the upper and lower ram blocks close. 
     
     
         17 . The shear ram assembly of  claim 11 , wherein the arms are attached to the upper ram block by means selected from the group consisting of welding, adhering, and mechanical fasteners. 
     
     
         18 . The shear ram assembly of  claim 11 , wherein the arms are integral with the upper ram block. 
     
     
         19 . A subsea BOP assembly, comprising:
 a BOP stack having a frame with a wellhead connector at a lower end for connecting to a subsea wellhead assembly; and   at least one shear ram attached to the frame for shearing pipe and ductile items extending through the BOP assembly and into the wellhead assembly, the at least one shear ram comprising:
 first and second ram blocks positioned adjacent the pipe and ductile items, and on opposite sides thereof, the first and second ram blocks arranged to close around the pipe and ductile items; 
 first and second blades attached respectively to the first and second ram blocks and positioned so that as the first and second ram blocks close around the pipe and the ductile items, the blades pass over one another and shear the pipe and the ductile items; 
 at least one recess in the second ram block; 
 at least one arm attached to the first ram block that inserts into the at least one recess when the first and second ram blocks close; and 
 at least one plate positioned on the at least one arm, so that when the arm inserts in to the at least one recess, the wear plate slides against a surface of the recess and orients the blades at a maximum distance apart.