John Benson reveals the latest news from the pipeline inspection sector
The majority of general visual inspections of subsea assets can be done in real time. Generally a 3.4U inspector complements the ROV or diving team. The inspector commentates during the inspection and using his/her experience, determines the structural integrity of the asset. This is done in real-time and the results are usually compiled in a final report, written in a format that is acceptable to the end client, the asset owner.
Pipeline inspection however, is a more challenging affair. Routine platform inspections are usually done directly from the platform or from a static vessel alongside. When inspecting pipelines the vessel moves along the pipeline, effectively following the ROV. This is generally called ‘Follow Sub Mode’, with both the ROV and vessel moving along the pipeline at a set rate. During this inspection the ROV team, together with the 3.4U inspector, are carefully watching the video feed and reporting any anomalies that are visible.
This is no easy affair to do in real time, due to the multi-channel video and the general pace of the inspection. The ROV will also have various extra survey equipment fitted to aid the inspection. A pipe-tracker may be fitted, to allow the ROV team to follow the pipeline when it is buried. A profiler will also be required to give a profile of the pipeline in relation to the seabed. From the profiler data, combined with GPS positioning, it can be ascertained if a pipeline is supported on the seabed. If the pipeline is not supported (freespan), this needs to then be measured accurately. This is fairly impossible to do in real-time, due to the pitch/roll of the vessel and other GPS anomalies.
Therefore, most pipeline inspection and associated reporting is ‘offline’ and involves a team of inspectors, reviewing previously recorded video and eventing any anomalies. The previously collected GPS positioning data also needs to be smoothed, due to vessel pitch and roll, etc. The anomalies found are then matched to the smoothed GPS, to provide the most accurate true position of the anomaly.
In addition, some pipelines are buried below mean seabed level at the time of laying. This is mainly done to protect the pipeline from any fishing trawling. So the position of the pipeline within the trench is also very important.
Once all of this is done, a final report can be issued to the client with any anomalies logged and correctly identified. This report can then be used to compare against previous years’ inspection to monitor any changes.
During 2015, Digital Edge Subsea will be launching a new addition to its product range, the dedicated pipeline version of the EdgeDVR. The existing version can be used on pipelines, due to its eventing properties, but a true pipeline solution requires a greater level of reporting due to a greater amount of data.
The new pipeline system will be capable of recording one high-definition (HD) video channel and up to three standard-definition (SD) video channels, together with all survey sensor data.
In addition to the pipeline system, the company will also be releasing a ‘Lite’ version of the EdgeDVR and a blackbox recording system.
For more information visit www.engineerlive.com/iog
John Benson is with Digital Edge Subsea, Ulverston, UK