Automated inspection of subsea structure: A case study

The extreme operational environmental conditions and aging conditions of subsea structures pose risk to their structural integrity and is critical to their safety. Non-destructive testing plays a key role in identifying defects developing within the structure, allowing repair in a timely manner to mitigate against failures that cause damage to the environment and pose a hazard to human operators. However, in order to be cost effective, inspections must be carried out in-situ and this poses significant safety risks if undertaken manually. This paper presents the development of an automated inspection system of flexible risers that are used to connect wellheads on the seafloor to the offshore production and storage facility. Due to the complex structure of risers, radiography is considered as the technique suitable to inspect multiple layers of the risers. However, radiography inspection in turn requires a robotic system for in-situ inspection with higher payload capacity, precise movement of source and detector and withstand extreme operational environment. The deployment of the inspection system has been achieved by implementation of a bespoke robotic scanning system that can accurately control the source and detector motion. The prototype was mounted on a flexible riser during shallow water sea trials. The results from the trial show that the internal inner and outer tensile armour layer in the riser could be successfully imaged in real operational conditions.