Pipe die method and apparatus

Abstract

A die used in slip and elevator assemblies in oil and gas drilling operations for gripping tubular members while coupling and uncoupling joints, the die including electroless nickel plated, non-interrupted knurled teeth with a truncated pyramid shape and a dimple therein which reduces die surface penetration, thereby reducing wall loss due to die penetration, stress cracking, and carbon transfer leading to acid corrosion in oil and gas field tubular members and especially to corrosive resistive alloy tubular members.

What is claimed is:  
     
         1 . A pipe die insert of the type generally used in slip and elevator assemblies to grip, lift and suspend tubular members in oil and gas drilling operations, the die insert comprising: 
 a) an elongated, rectangular shaped steel die member having thickness and a length approximating that of said slip and elevator assemblies, said thickness tapering along said length, said die further having a concave face relative a longitudinal axis;    b) a plurality of knurled teeth arrayed over said concave face; and    c) a coating means applied to all surfaces of said die, including said knurled teeth, to prevent wear and corrosion.    
     
     
         2 . A pipe die according to  claim 1  wherein said knurled teeth are pyramid shaped having truncated tips with a dimple therein.  
     
     
         3 . A pipe die according to  claim 1  wherein said teeth are cross-knurled and are uniform across said concave face,  
     
     
         4 . A pipe die according to  claim 1  wherein said coating means is hard chrome plating of electroless nickel in solution, chemically disposed by ionic transfer, having a thickness of between 0.0001 and 0.0007 of an inch.  
     
     
         5 . A pipe die according to  claim 4  wherein said hard chrome exhibits a high resistance to wear and having an equivalent hardness in excess of 60 Rockwell “C”.  
     
     
         6 . A pipe die insert of the type generally used in slip and elevator assemblies to grip, lift and suspend tubular members in oil and gas drilling operations, the die insert comprising: 
 a) an elongated, rectangular shaped steel die member having thickness and a length approximating that of said slip and elevator assemblies, said thickness tapering along said length, said die further having a concave face relative a longitudinal axis;    b) a plurality of cross knurled truncated pyramid shaped teeth having a dimple therein arrayed over said concave face; and    c) a hard chrome electroless plating applied to said teeth having a thickness between 0.0002-0.0004 of an inch with a hardness in excess of 60 Rockwell “C”.    
     
     
         7 . A method of lifting and retaining threadably coupled nickel alloy drill pipe with slip and elevator assemblies without significantly marring the surface finish thereof comprising the steps of: 
 a) replacing dies in one of said assemblies with a compatible set of die inserts, each insert comprising: 
 i) an elongated rectangular shaped steel die member having thickness and a length approximating that of said assemblies, said thickness tapering along said length, said die further having a concave face relative a longitudinal axis;  
 ii) a plurality of knurled teeth arrayed over said concave face; and  
 iii) a coating means applied to all surfaces of said die, including said knurled teeth; and  
   b) utilizing said assemblies and said replacement set of die inserts to engage said nickel alloy pipe without significantly marring said surface finish of said pipe.    
     
     
         8 . The method according to  claim 7  including the step of repetitiously engaging said nickel alloy pipe with said dies without transferring carbon from said dies to said pipe.  
     
     
         9 . The method according to  claim 8  includes the step of engaging said nickel alloy pipe with said dies and applying compression thereto with a carbon transfer rate of between 1-2% of the contact surface between said dies and said pipe.  
     
     
         10 . A method according to  claim 7  further including the step of reducing cost of inspection and increasing useful longevity of slip and elevator dies comprising the step of hard chrome plating said dies with electroless nickel in solution, chemically disposed by ionic transfer, having a thickness of between 0.0001 and 0.0004 of an inch.  
     
     
         11 . The method according to  claim 7  further includes the step of deburring, leaving said dies without any significant sharp edges.  
     
     
         12 . A method according to  claim 7  further comprising the step of knurling said teeth upon the interior concave surface of said slip and elevator die inserts by knurling in one direction at one depth and knurling in the opposite direction at a second depth thus producing a deformed tooth formation on said surface having a truncated point and a dimple therein.  
     
     
         13 . The method of knurling according to  claim 12  wherein said knurling process includes the use of 30 degree left and right hand spiral, circular pitch knurl to produce a pyramid shaped tooth.