Deperming technology in large ferromagnetic pipes

This report describes a deperming technique for reducing of the are blow ef fect in DC welding of ferromagnetic pipelines. The technique is based on co mpensation of the axial field in the welding gap by a re-magnetization of t he pipe near the joint. The re-magnetization is produced with a coil set dr iven with a bipolar impulse, We examined an axisymmetrical model of the pip es with commercial finite element software (ANSYS). The model has plane sym metry in the middle of the welding gap, Initial magnetization levels in the model were determined from a preliminary experimental investigation of an oil pipeline in Ukraine, A prototype of the deperming device was fabricated , including a coil set, an impulse power supply and a magnetometer, A magne tic measuring procedure was also developed to optimize the transient curren t in the coils, Our experimental results have confirmed the efficacy of thi s deperming technique, which provides an acceptable level of the magnetic F ield in the welding gap.