Sonomatic develops solution for subsea pipelines challenge

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Until recently, thousands of miles of subsea pipelines were almost impossible to inspect ultrasonically, as they were beyond the reach of divers. Issues such as ageing structures and life extension have only intensified the importance of pipeline integrity management, of which externally applied ultrasonic inspection is a key component. At Sonomatic, we have been addressing this pressing problem as part of our research and development for a number of years. It has been a challenging process, as the accurate external ultrasonic inspection of subsea pipelines, at depths beyond diver accessibility, requires many complex techniques to be enacted simultaneously. 

In December 2010, we launched an automated ultrasonic inspection tool, which can be deployed by a remotely operated vehicle (ROV) to depths of up to 2000m. This new technology, the ROV-iT is part of a subsea inspection tradition at Sonomatic. We designed and launched our first ultrasonic scanner in 1989 and have continued to develop new innovations ever since.

At Sonomatic, we believe that the development and deployment of inspection equipment in-house ensures it is optimised for unique operating conditions. It also enables us to use our extensive field experience to ensure developments meet all the practical requirements for field use. Our design process involves combining our capabilities in inspection tool development, mechanical design and analysis, ultrasonic inspection modelling, electrical engineering, electronics, software and system integration. The project’s aim was to create a remotely operated automated ultrasonic scanner which could not only be operated at great depth but would also be flexible in its application.

Pipelines are not the only subsea structures beyond the reach of divers. There is also demand in the industry to find safer and more cost effective means of inspecting other areas such as risers, flexible risers, caissons and structural assets. The ROV-iT has the capacity to complete a subsea inspection, utilising techniques such as corrosion mapping and Time of Flight Diffraction (ToFD), on a variety of complex structures, since it can be deployed vertically as well as horizontally. We also recognise that an increasing number of piping systems are being installed at depths beyond diver accessibility and, as the needs of the sector change, ROV-deployed inspection’s capacities have to be developed further.

Our work on this particular project began following a presentation of several potential ROV-deployed inspection concepts.  Approached by a major operator with a particularly intricate project, it was clear that new inspection technology was required urgently. The project outlined by the operator required an ROV deployed high-resolution inspection system capable of performing zero degree corrosion mapping on a buried pipeline, with a smaller Methanol piggyback line only 4 inches above it. The pipeline was not situated at any great depth, but its location was in the southern North Sea, an area known for its strong tidal currents during the winter. While divers could reach the required depth, the area was not deemed safe for personnel due to the strong currents and adverse weather.

Our solution was to design the ROV-iT to meet the requirements of the operator’s inspection as well as the other considerations already discussed. We maintained design control by self-funding the project, investing heavily in the design and development of its tool and control systems. Every aspect of the project, including concept development, ongoing peer review and feedback from the client, detailed design, manufacturing and integration with ROV, was completed in eight months allowing us to get the operator’s inspection under way.

The inspection methods chosen for the operator’s pipeline inspection were high resolution corrosion mapping, to investigate the full circumference of the epoxy (FBE) coated pipe, and Time of Flight Diffraction (ToFD), to identify degradation in the welds. These techniques were successfully carried out by the ROV-iT during a number of live trials, before the offshore phase took place in December 2010. The resulting inspection was a success for Sonomatic as well as our client.

The inspection proved the ROV-iT’s flexibility, which was important as subsea inspection can present a myriad of challenges. For this reason, the ROV-iT has been designed to carry out a variety of inspection programmes, including the verification of ILI tool findings, inspection for internal corrosion and erosion, preferential weld corrosion and erosion, fatigue cracking, wet H2S damage in sour service, chloride pitting and SCC in corrosion-resistant alloys, subsea fabrication and repair welds, and component geometry measurement with ovality inspection. A major application for the ROV-iT will be the inspection of unpiggable lines where the accuracy of Sonomatic’s inspection technology allows greater confidence in assessment of line condition based on statistical analysis.

Since its launch at the end of 2010, we have continued to develop our ROV-deployed inspection capabilities. In 2011, we unveiled the MAG-Rover, a brand new remotely steerable ultrasonic scanner which, uniquely, can be used in topside locations as well as subsea. With strategically-placed offices, we can deploy our remotely operated automated ultrasonic inspection technologies anywhere in the world. Our systems offer a cost-effective solution for operators as they collect accurate and reliable data, can be deployed to a depth of 2000m and do not require a diver support vessel or divers.