Teletest® long range UT inspection of 12" heavy fuel oil line

This inspection of a 3.5km pipeline was carried out over a four-day period at a UK Refinery by TWI's wholly owned subsidiary, Plant Integrity Ltd (P i) acting as sub-contractors to Northern NDT. Specific lengths of line were selected visually as having potential corrosion problems - road crossings, damaged insulation or corroded canning, leaking from the steam trace lines, evidence of flooding surrounding the pipe, etc. Following this preliminary survey, 800m of line were chosen for Teletest® inspection from 30 locations. The line was insulated with mineral wool. The heavy fuel oil contents of the line were found to attenuate the signal somewhat, but did not hinder inspection significantly. Furthermore, the transducers were readily deployed, despite the presence of the steam trace lines. Finally, longitudinally welded pipe supports at 5m intervals had no adverse effect on transmission. 'Moderate' and 'minor' anomalies, representing suspected metal loss features, were located at 12 locations, with a longitudinal accuracy of ±200mm. These anomalies were recommended for detailed local examination. Good correlation was found between the Teletest® predictions and the flaws present.