Inspection of Composite Pipelines Using X-ray Imaging

The integrity of subsea equipment is of paramount importance for the operational continuity of oil and gas production. Due to recent problems with stress crack corrosion (SCC) corrosion in flexible metallic pipelines, Oil & gas operators and pipelines suppliers are developing flexible pipelines made of composite materials, as these are not susceptible to classic corrosion mechanisms. This work presents the results obtained with three radiographic techniques (digital radiography with digital detector array (DDA), computed laminography (CL) and computed tomography (CT)) applied to TCP (Thermoplastic Composite Pipe) pipelines. Artificial discontinuities were inserted in these samples by crushing test experiments. In sequence, the above X-ray imaging techniques were used to detect and size the discontinuities generated in the samples (typically: cracks and delaminations). The results demonstrate the technical viability of digital radiography using DDAs as well as CL and CT for 3D reconstructions of the inspections of TCP pipelines. Notably, CT showed the best results. It was possible to detect and size delaminations with openings larger than 96 µm with the used system. Using DDA and CL it was possible to detect and size other discontinuities in the samples. It is important to mention the CL and CT 3D volume reconstruction capability. Additionally, CT in a fast scan mode showed satisfactory results compared to a slower scanning CT. Based on the results obtained and the operational characteristics of each technique, it is vertified that radiography can be used as a standard testing method, recommending the use of CL, and best CT, especially at points of the TCP pipelines which require more accurate and detailed information on the discontinuities present.