Hinged magnetic work coil joins large-diameter pipes by magnetically crimping a metal tube around them. Grooves in the pipes improve pullout strength.

Welding large-diameter oil and gas pipes is hazardous, but threading them together can also be difficult and time consuming. A new method uses a magnetic pulse to join abutting pipes.The method cold-forms a metal sleeve around the ends of two abutting pipes.

To produce the ring-shaped crimping forces, a hinged magnetic work coil is clamped around the sleeve. When the magnetic pulse forms, it instantly crushes the sleeve onto the pipes and into shallow grooves milled around the pipe ends. The grooves need not be precisely cut to grip the sleeve and resist pullout. Because the magnetic field presses the metal uniformly, the joints have uniform stress distributions.An alternate method places the coil inside the pipe, swelling it outward toward an external form.