Redundancy in position reference and controls, plus green energy, will prevent issues becoming accidents
Advancements in control systems, reference sensors and annual testing are making dynamic positioning (DP) more reliable, despite evidence of falling safety.
Position reference and control systems have become more advanced and global navigation satellite systems (GNSS) more accessible, giving OSV and drilling rig owners operational improvements.
These are vital improvements for the offshore sector as reports and data indicate DP safety has dropped in the past three years, due to issues with computers, power grids, sensors and thrusters.
More vessels operating in DP mode are reporting incidents and undesired events now than they were in 2019, indicating the industry still faces safety issues, and is increasingly reporting on them, according to the latest data from International Marine Contractors Association (IMCA).
“Data shows that since 2019, DP operations are becoming less safe,” said IMCA technical advisor Richard Purser, speaking at Riviera Maritime Media’s European Dynamic Positioning Conference, London, UK, 14 June, 2022. “We need to turn this around and bring down those numbers.”
IMCA received 213 reports from DP vessels over 500 days between January 2021 and May 2022. Of these, 54% were undesired events involving system failures and loss of redundancy; 34% were DP incidents, such as major system failures, and 12% were DP observations that did not result in issues.
The main causes of these reports were issues with thrusters and propellers, followed by computers, power grid and reference sensors. Mr Purser said secondary causes were mainly down to the human element, electrical, computers and then thrusters and propulsion.
Some of the loss of positioning was from issues with reference sensors and a dependence on GNSS, mostly GPS. These risks can be mitigated using other GNSS – such as Europe’s Galileo and China’s Beidou.
Other alternatives include laser- or radar-based referencing devices as part of an integrated DP system, noted Wärtsilä product lead for DP technology Avinash Hingorani.
Sensors Artemis Mk 6 and RadaScan View, using 9 GHz radar and targets, are specifically used in offshore oil and gas operations, Artemis with a range of 10 km and RadaScan 600 m.
CyScan, RangeGuard and SceneScan are more suited to vessels operating around offshore windfarms. RangeGuard uses 24 GHz radar, is solid state and targetless and has 300 m range. CyScan uses a laser with a prism target and has 2.5 km range, while SceneScan is a targetless laser with a 200 m range.
Wärtsilä also offers the RS24 radar reference device with 24 GHz radar operating at 60 rpm with 1,500m range and SPECS camera with 180º field of view for situational awareness.
“Targetless sensor technology can help achieve efficient and safe offshore DP operations,” said Mr Hingorani. “They provide value to operators as there are no targets, quick turnarounds and reduced dependence on GNSS for position reference.”
Remote operations
Advances in DP systems are enabling more remote-control operations and management of vessels from shore centres. Sirehna provided its latest DP technology for a remote-control pilot project with SeaOwl Energy.
A Paris-based operator remotely piloted OSV VN Rebel through a certified DP system, using Marlink-supplied connectivity, in 2020 and 2021.
“Several tests and trials were carried out in extreme conditions,” said Sirehna project manager Loic Vilain. With 800 km between the control centre and VN Rebel, 10 trials were conducted, including five official demonstrations.
“Targetless sensor technology can help achieve efficient and safe offshore DP operations”
Technology included Sirehna’s Brizo controls and automated collision-risk assessment unit, collision alert and environmental perception sensors, including AIS and radar tracking, optical tracking and artificial intelligence.
Sirehna’s solution enables an operator to supervise operations from a shore centre and have direct control of the navigation through DP. Brizo offers automatic collision risk assessment from tracking obstacles on the surface. It proposes an alternative route to follow which avoids collision and grounding when a risk is detected.
“There needs to be cyber-secure communications, multiple sensor fusion and display in real-time,” said Mr Vilain. All this recreates the navigation environment using a 360° camera-stitching panoramic view and technology to detect and track obstacles and to suggest manoeuvres to avoid collisions.
