This line carried water-based slurry. It was not insulated and was at ground level, so that access for inspection was not difficult. The main concern was local high levels of internal erosion where eddies in the flow caused turbulence and consequent high impact of particles on the inside of the pipe. Since service history had shown that these occurrences were difficult to predict, spot thickness measurements were ineffective in detecting thinned areas prior to leakage. Teletest ® equipment was used as 100% of the pipe wall is examined. During initial trials, a test was carried out on a section where a small leak had occurred and the result is shown in the scan.The signal approximately 12m from the datum is from a butt weld. The very large signal which follows at 14m (marked '+') coincided with the location of the leak. This suggested extensive metal loss and it was found by subsequent examination that there was a band of erosion almost through the wall for the majority of the pipe circumference. The pipe was therefore at the end of its life.