Method and apparatus for applying axial stress for weld testing

Abstract

A method for testing the integrity of a weld on a pipe includes the application of an axial stress on the weld during the integrity test. An assembly for performing the method is also provided, wherein a pair of circumferential supports are provided on the pipe, on opposite sides of the weld, and between which extend axial force applying devices. In one aspect, the invention is used to test a weld securing a flange to a pipe. The invention also provides novel circumferential clamps for securing to the exterior of pipes.

1 . A circumferential clamp for securing to an outer surface of a pipe, the clamp comprising:
 a generally annular shaped collar having an outer diameter and an inner diameter and being adapted for placement around the outer circumference of said pipe;   a plurality of hydraulic cylinders provided on the collar, said cylinders being generally equidistantly spaced along the inner diameter of the collar;   each of the cylinders including a ram extendable in the direction parallel to the radius of the collar and in the direction toward the center of the collar whereby, upon actuation of said rams, said cylinders apply a generally equal force against the outer surface of said pipe.   
     
     
         2 . The clamp of  claim 1 , wherein the collar is comprised of two or more sections connected together. 
     
     
         3 . The clamp of  claim 2 , wherein adjacent pairs of the two or more sections are connected by a hinge. 
     
     
         4 . The clamp of  claim 3 , wherein at least one adjacent pair of the two or more sections include a locking means to form the collar once positioned over the pipe. 
     
     
         5 . The clamp of  claim 1 , wherein the collar includes a plurality of pockets open to the inner diameter thereof, and wherein said pockets are adapted to receive the hydraulic cylinders. 
     
     
         6 . The clamp of  claim 1 , further comprising a means for actuating the hydraulic cylinders. 
     
     
         7 . The clamp of  claim 1 , further comprising a plurality of load distributing pads for circumferentially distributing the force exerted by said rams. 
     
     
         8 . A circumferential clamp for securing to the outer diameter of a pipe comprising:
 a plurality of links connected together to form a chain, said chain being sized to cover the circumference of said pipe;   each of said links including a connection means for connecting to adjacent links;   each of said links including an electromagnet, connected to a power supply, whereby upon activation of said power supply, said magnets engage the outer surface of said pipe.