Into the Deep using advanced camera techniques
Underwater drones, also known as remotely-operated vehicles (ROVs) have proved key to the inspection of difficult-to-access reservoir assets in Wales
By Euan Hampton, Innovation Scientist, Dwr Cymru Welsh Water
The Welsh landscape has long been used for the efficient capture and storage of water for the purposes of water treatment – something our high rainfall helps with.
Surface water makes up 93% of the total water supplied to the customers of Welsh Water with significant volumes coming from open water reservoirs. Alongside this, we own and operate the Elan Valley reservoirs, which supply the West Midlands. While these structures can be considered as feats of Victorian engineering, adding to the beauty and wonder of the landscape, they can pose a significant challenge.
Dwr Cymru Welsh Water, like all other water companies, needs to understand and monitor the condition of assets like these. This can be particularly challenging where individual assets can be 30 metres or more below the water surface in turbid water with low light penetration.
How do you carry out a detailed survey of assets in such a hostile environment? Traditionally, we have relied on the skills of crewed dive teams, or – more recently – the use of remotely-operated vehicles (ROVs).
The use of divers in such difficult environments can pose significant health and safety risks. As-built drawings of such assets can be somewhat misleading to say the least. With even less information about temporary works that may have been left in situ, or undocumented abstraction points, surveying within these dark murky waters is particularly dangerous.
On top of these health and safety considerations, the quality of the data returned can be lower than we hope or expect. Movement within and around these assets can easily cast up sediments resulting in virtually zero visibility and poor quality photos and videos.
We set out to find a method that would provide the quality of data we need to undertake condition surveys, and the collection of detailed dimensions in a way which would reduce health and safety concerns.
In 2018 we met Abyss Solutions Ltd, an Australian robotics company which combines the latest innovation in ROVs with data analytics. The company had not worked in Europe before, but we had been provided with examples of how they had applied their technology on assets across the world to provide high-fidelity imagery in turbid environments. As well as this, its analytics provide quantitative assessment of condition which can be monitored over time in contrast to the qualitative or subjective assessments relied upon in the past.
As a result, Dwr Cymru Welsh Water invited Abyss Solutions across to the UK to undertake survey on two of our reservoirs – Lisvane in Cardiff and Craig Goch in the Elan Valley. Craig Goch is at the head of the Elan Valley chain of reservoirs. It is a classic Victorian reservoir, where assets are at significant depths and as-built drawings are incomplete. The survey was undertaken over two days in January 2019, with support in the UK provided by Panton McLeod.
By using robotic technology, Abyss Solutions can eliminate many of the dangers and logistical complexities associated with crewed and diver inspections. The technology allows assets previously considered inaccessible to be inspected in detail without disrupting their operation. This is ideal for asset networks with a lack of redundancy and can make it simpler and inexpensive to inspect assets on a frequent basis.
Traditional inspection methods struggle to provide usable visual information in turbid and low light environments, which presents engineers with ambiguous data leading to subjective and inconsistent assessments. Abyss Solutions’ high-fidelity technology eliminates this through better-quality, clearer and colour accurate visual data. Abyss Solutions can also unlock additional information on asset condition through using other sensing modalities such as sonar and laser.
This allows it to build a visual baseline that can be thought of as a desktop virtual tour of a whole asset.
During the survey, a full condition assessment was undertaken on the walls and tower of the reservoir which in some locations reaches 25-30 metres in depth. As well as a rogue Christmas tree, we identified a number of assets and structures that have not been viewed since the reservoir was originally constructed.
By accessing the suite of equipment the team from Abyss could provide, we were able to assess the dimensions of individual features such as pipes and valves, the distances between these features, silt levels and surface areas affected by corrosion or spalling. The comprehensive and quantitative nature of the data collected enables asset condition to be tracked and predicted – something that has not been easy to do in the past.
The quality of the images produced was far beyond what was expected or that has been achieved in the past. This, combined with the online 3D virtual replicas combining video, measurements and condition information has provided us with an exceptionally detailed post survey report.
We found the costs of the work, including mobilisation and all post processing was comparable to traditional methods, given the amount of data that is obtained. However, most importantly, we are now able to obtain the detailed information we require without the need to undertake more risky diver-led survey procedures. This advancement in camera techniques and post processing will lead to a step change in how we as a business undertake such works and improve our ability to maintain such iconic structures.
-This article appears in the May 2019 issue of WWT magazine.
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