Threaded connection for steel pipe

Abstract

A method for assembling a threaded connection for a steel pipe, which connects a first pipe formed with a pin having a truncated cone shape at an end thereof, and a second pipe formed with a box having an opening end. The pin includes a male thread portion, which is a tapered thread, and a seal portion, which includes a tapered surface. The box includes a female thread portion, which is a tapered thread, and a seal portion, which includes a tapered surface. The tapered surface of the pin has a minimum diameter smaller than a maximum diameter of the tapered surface of the box. The method includes making-up the male thread portion and the female thread portion by screwing, whereby a root of the male thread portion and a crest of the female thread portion come into contact with each other after the seal portion of the pin and the seal portion of the box come into contact with each other.

1 . A method for assembling a threaded connection for a steel pipe, which connects a first pipe formed with a pin having a truncated cone shape at an end thereof, and a second pipe formed with a box having an opening end,
 the pin including
 a male thread portion which is a tapered thread, and 
 a seal portion which includes a tapered surface, 
   the box including
 a female thread portion which is a tapered thread, and 
 a seal portion which includes a tapered surface, 
   the tapered surface of the pin having a minimum diameter smaller than a maximum diameter of the tapered surface of the box,   the method comprising:   making-up the male thread portion and the female thread portion by screwing, whereby a root of the male thread portion and a crest of the female thread portion come into contact with each other after the seal portion of the pin and the seal portion of the box come into contact with each other.   
     
     
         2 . The method for assembling the threaded connection for a steel pipe according to  claim 1 , wherein
 the seal portion of the pin is provided on each of a tip side of the pin from the male thread portion and a base side of the pin from the male thread portion.   
     
     
         3 . The method for assembling the threaded connection for a steel pipe according to  claim 1 , wherein
 the pin further includes an R portion which is provided on a tip side of the pin from the seal portion of the pin, and   the box further includes an R portion which is provided on a tip side of the box from the seal portion of the box.   
     
     
         4 . The method for assembling the threaded connection for a steel pipe according to  claim 1 , wherein
 the male thread portion is divided into a plurality of male thread portions along a pipe axis direction of the first pipe, and   the seal portion of the pin is further provided between the male thread portions adjacent to each other in the pipe axis direction.   
     
     
         5 . The method for assembling the threaded connection for a steel pipe according to  claim 1 , wherein
 the pin further includes an abutment surface which is provided on a tip or a base of the pin.   
     
     
         6 . The method for assembling the threaded connection for a steel pipe according to  claim 1 , wherein
 each of the first pipe and the second pipe is a steel pipe.   
     
     
         7 . The method for assembling the threaded connection for a steel pipe according to  claim 6 , wherein
 an outer diameter of a body of the first pipe is 190 mm or more,   an outer diameter of a body of the second pipe is 190 mm or more, and   before performing the making-up, an outer diameter of the box is more than 100% of the outer diameter of the body of the first pipe, and is less than 104% of the outer diameter of the body of the first pipe.   
     
     
         8 . The method for assembling the threaded connection for a steel pipe according to  claim 7 , wherein
 before performing the making-up, a difference between the minimum diameter of the tapered surface of the pin and the maximum diameter of the tapered surface of the box is more than 0% of the outer diameter of the body of the first pipe, and is 0.3% or less of the outer diameter of the body of the first pipe.   
     
     
         9 . The method for assembling the threaded connection for a steel pipe according to  claim 1 , wherein
 the first pipe is a steel pipe, and   the second pipe is a coupling.   
     
     
         10 . The method for assembling the threaded connection for a steel pipe according to  claim 9 , wherein
 an outer diameter of a body of the first pipe is 190 mm or more.   
     
     
         11 . The method for assembling the threaded connection for a steel pipe according to  claim 10 , wherein
 before performing the making-up, a difference between the minimum diameter of the tapered surface of the pin and the maximum diameter of the tapered surface of the box is more than 0% of the outer diameter of the body of the first pipe, and is 0.3% or less of the outer diameter of the body of the first pipe.