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Inspection tool designed to fill a niche


T.D. Williamson, Inc. (TDW) has announced the successful development of a new 48-inch Gas Magnetic Flux Leakage (GMFL) inspection tool. The new tool has already had a field run on a 48-inch natural gas transmission line in Canada.

TDW can provide cleaning pigs and inline inspection (ILI) services using its 48-inch Kaliper 360 tool for identifying physical anomalies and geometry in a pipeline and using its 48-inch GMFL tool for identifying corrosion features and pipe wall loss. TDW can also offer hot tapping and plugging services to assist with the repair of identified anomalies.

TDW’s Gas MFL (GMFL) tool is designed to fill a niche in the ILI market. Gas pipeline MFL tools do not enjoy the advantages that liquid product MFL tools do. In a liquid line, the product (for instance, crude oil) provides lubrication, reducing friction
between the inspection tool and pipe wall.

This makes it possible to maintain a steady speed as the MFL tool traverses the pipe. In a gas environment, however, opposite conditions predominate: without the lubrication, friction rises, causing the magnetic inspection tool to “stick” to the pipe wall. In addition, it is difficult to maintain a steady tool speed because variations in gas pressure cause the tool to stall and surge as it moves within the line.

The TDW high resolution GMFL tool addresses these impediments with three strategies. First, each magnetizer “floats” individually so that magnetic forces are consistent whether in a thick or thin wall, or a tight bend. By reducing tool drag, floating magnetizers enable more consistent velocities. Second, the traditional MFL tool has coarse steel brushes that magnetize the pipe wall (so that sensors can read magnetic loss levels).

These are replaced in a GMFL tool with smooth, flat wear skid plates that glide more easily. Finally, the tool’s design allows for as much as 25 per cent bore reduction and is constructed of lighter weight materials, making the TDW GMFL tool approximately half the weight of other 48-inch tools.