MTM Pipeline Inspection System:
Evaluation & Validation for National Grid, UK
(based on “Annual IFI Report National Grid” - 2012)
The original series of trials, performed in 2011, established that the MTM system had the potential to inspect a buried pipeline from the surface and locate metal loss features.
The MTM system successfully inspected 6 sections of pipeline which had previously been inspected with an In Line Inspection (ILI) tool. Following completion of the onsite trials, an MTM inspection report was produced and the MTM results were overlaid on top of the ILI data. This produced a set of pipeline maps that has enabled a direct comparison to be made between the two sets of data. Evaluation of the two data sets has shown that there is a good correlation between the locations of the pipeline anomalies.
Between April and November 2012, the MTM system was used to inspect NG pipelines at 6 locations within the UK. The inspection results were compared to ILI results. Additionally, 2 sections of pipelines suffering from ground movement (due to mining) were also inspected, plus a sleeved section of pipe. From overlaying the original pipeline maps on top of the MTM maps, it appears that MTM system can also detect features like pipeline girth welds and pipeline fittings such as bends.
MTM system performed very well during the trials. A good correlation was obtained between the levels of stress measured in the pipes from strain gauges and the stress values obtained from the MTM results.