INSPECTION TECHNOLOGY Q
“The inspection only required the semi- submersible to deballast. We flew the drone 25m below the main deck in order to check the condition of the fairleads and their connections to the columns that hold up the TSV. With wind speeds of around 15 knots, this went very well and the survey showed that the fairleads and their connections were in a good condition.” It was a first too for the tender’s owner
Prosafe, which reports that the survey saved a significant amount of time and money. “Normally this kind of operation would
cause a disruption of several days to our client,” says Ian Young, chief operating officer at Prosafe. “The drone survey took only a few hours and was just as effective,”
Captured imagery: wind and flying distances are the main challenges for offshore drone surveys
Learning curve To get to this point, Galinski’s specialist team has gone through years of experimentation, modifications and practice runs. And even after having optimized the technology, they have found that flying drones on maritime structures comes with its own set of challenges. “When inspecting the cargo hold of a large
oil tanker, for example, you have to fly the drone about 30m away in the dark,” explains Galinski. “In addition, the pilots are surrounded by thousands of tonnes of steel, which means that the drone’s GPS and magnetic compass, which usually help it identify its position, don’t actually work – and neither does its positioning support. This can make the drone’s behaviour somewhat unpredictable at times. “If you fly a drone outside in your garden
with the position-keeping function enabled, you can push it away and it will automatically return to where it was before. However, on a ship, any sudden input can cause the drone to become unstable and require the pilot to correct its position manually.
“During an offshore survey the pilots manoeuvre the drone along structures at distances of up to 180m. In this environment, the wind speed is the greatest risk factor. “We chose the DJI Phantom drone for the
Safe Scandinavia survey because it can be fitted with a cage. Protecting the drone was important because we were operating it very close to obstacles such as anchor chains and wires. One of the most important advantages with the DJI Phantom drone is its compact size. It can fit neatly into a backpack – making it very convenient for taking offshore by helicopter. “The successful survey demonstrated that
the DJI Phantom was certainly up to the challenge, because it not only survived the inspection but also delivered valuable results.”
Inspection revolution Looking ahead, Galinski expects drones to revolutionize the inspection regime. “I am confident we will eventually see the introduction of autonomous drones,” he says.
“This would open up many new possibilities. For example, autonomous drones could be dropped into inerted compartments which human beings are unable to enter. “The surveyor could remain safely outside
while the autonomous drone would follow a pre-determined flight path to check the condition of the compartment. This would enable survey teams to carry out inspections without having to complete lengthy preparations, while keeping surveyors safe.” In future, it might even be possible for an autonomous drone equipped with artificial intelligence to carry out surveys independently, monitored by the surveyor from the shore office using a virtual-reality headset. For the time being, the autonomous functionality still requires further development. “Outside drones can follow a predefined
flight path using a GPS signal, but for confined steel compartments we need to find an alternative approach,” says Galinski. In a joint research project, DNV GL and
the University of Trondheim, Norway, are now developing an autonomous drone. With several options under consideration, Galinski expects to see the first autonomous surveys of inerted compartments in the near future. “Two of our drone pilots have now
completed the BVLOS (Beyond Visual Line of Sight) certification, which allows them to operate drones beyond their line of sight. “So, while drone inspections are a niche for
now, more advanced models with AI capabilities could soon be transforming ship surveys. We want to be ready for this.”
Specialised drone: the DJI Phantom drone can carry out external surveys for up to 20 minutes
Watch DNV GL surveyors carrying out the classification society’s first offshore drone survey on board Safe Scandinavia at:
bit.ly/2ANcqDi For further information about DNV GL’s drone team, go to:
dnvgl.com/dronesurvey
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