Magnetic Flux Leakage in the most cost effective inspection method currently used. There is now a significant demand for tools with diameters from 100 to 305mm. The challenge in designing these small tools is to fit them within a pipe whose cross section may be 25 times smaller than for larger tools. The tool may also have to negotiate bends with radii as small as 1.5 pipe diameters, so trains with up to ten sections coupled with flexible links have been developed. Custom state-of-the-art solid state electronics is used for sensing devices, data acquisition and storage systems, together with high performance magnetic materials and the latest, most powerful magnets.
Throughout the world, people are becoming more concerned with protecting their environment. The safest way to transport oil and as is considered to be by pipeline. The inspection of these pipelines is therefore becoming more important in order to prevent leakage, rupture, and to increase safety (Palmer and Lee, 1988). The ultimate goal in the development of in-line inspection tools for pipelines is to permit cost effective decisions regarding the necessity of repair, replacement or preventive maintenance. This demands accurate and reliable in-line surveys in order to assess all significant defects with confidence. Magnetic Flux Leakage (MFL) technology is one of the most cost effective inspection methods currently used for corrosion detection (Atherton 1988a, 1989 an 1990m Shannon and Jackson, 1988). It is offered by several pipeline inspection companies and can give excellent results in large diameter lines (above 305 mm diameter). Large-diameter transmission lines are normally the easiest to develop inspection tools for, although the amount of data produced, can present formidable interpretation challenges. Nevertheless, there is a growing demand for inspection services for smaller diameter lines, such as gathering and offshore lines and also lines within process plants or refineries.