A new gas line with internal 3 mm (0.12 in.) stainless steel CRA cladding experienced a failure. This 16" pipeline was commissioned early in 2013 and only occasionally used prior to the incident. The failure consisted of circumferential cracking in a girth weld at a pipe bend and an investigation team recommended a complete inspection of all weld joints on this 10 km (6 mile) line.
Following the failure, the line was shut down and depressurized. However, this critical piece of infrastructure could be required to be operational at short notice, so an accelerated solution was needed to ensure the safe resumption of this operation. The inspection needed to identify additional areas with lack of fusion or other crack-like anomalies in all girth welds along the pipeline.
Identification of circumferential cracks is one of the most challenging tasks for inline inspection (ILI). Older magnetic flux leakage (MFL) technology is not suitable for identification of these types of features and in addition cannot be used with cladded pipes due to the non-magnetic CRA lining. EMAT technology is similarly unsuitable and so only an ultrasonic technology (UT) inspection was appropriate for these specific threats.
Although UT inspection was the only feasible means to inspect this line, doing so required that a liquid coupling medium be introduced and NDT Global was awarded this project having the skills and experience to manage both setup and inspection.