MIAB Welding of Oil and Gas Pipelines

Abstract

Magnetically impelled arc butt (MIAB) welding is a “single shot” method of joining pipe and tube which is used in highly automated factory production lines in high volume industries such as automotive manufacture. The entire weld over the full joint thickness is made in one single operation, instead of using several passes as in conventional welding. It is believed to be capable of making finished welds in pipe from small diameters of around 75mm (DN75) up to around DN450, and to around 10mm wall thickness. The welding time is around 10 to 15 seconds, and the joint to joint cycle time will be about 1 minute. Under the right circumstances this means that pipelines in this size range could be welded at a rate of up to around 7.5km per day or more, with only a single small welding crew and a substantial reduction in overall cost. Whilst the circumstances that allow construction spreads to take advantage of that potential speed will not exist on every pipeline, there are still major economic and technical advantages to be had from using the process at more moderate rates. The present target thickness limit of 10mm will make it possible to weld Class 900 DN450 pipelines with maximum allowable operating pressures of up to 15 MPa. The use of MIAB welding will enable the entire paradigm of pipeline construction to be changed, and will lead to reductions in construction cost of around 15% or more when the process is first implemented. Larger savings are expected in the longer term.