Homopolar Pipeline Welding, An Overview
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Homopolar pulse welding (HPW) has been proposed as a one-shot, single stage welding process for the joining of pipe in the J-lay configuration. A joint industries program (JIP) has been formed to develop this process for off-shore, deep water applications. At this point, no studies have been conducted on the applicability of the method for underwater service, but its speed and lack of pressure sensitivity makes it an interesting possibility for future, deep water considerations. Homopolar pulse welding utilizes the high current, low voltage electrical pulse produced by a homopolar generator to rapidly resistance heat the interface between abutting pipe ends, producing a full circumference resistance forge weld requiring no filler metal in only three seconds. This five year program began in February 1993, funded by a consortium of six oil companies (Shell, Exxon, BP, Texaco, Amoco, and Mobil). The program's ultimate goal is to produce a prototype system suitable for installation on a barge. The goals for the first two years of the program include demonstrating suitability of the process by producing and evaluating welds in different grades and wall thicknesses of three inch nominal diameter API SL line pipe. Funding for each year of the program is contingent upon meeting program goals for the previous year.