Jukka Määttänen ABB Marine & Ports, Digital Services Helsinki, Finland jukka.maattanen@fi.abb.com
Container ships are not known for their flexibility. But in point of fact, they are not rigid, and a vessel’s structure does indeed bend in response to the varying loads on its hull. Though of course imperceptible to human senses, such dynamics can have a significant effect on cargo, particularly container stacks. Furthermore, given that the forces acting on containers in a stack are the result of a ship’s responses to prevailing conditions, the ability to monitor and predict vessel motions offers a self-evident safety benefit for containerships.
Then again, if limited to a single location, the accuracy of vessel motion measurements is limited. Accuracy levels improve significantly, however, when accelerations are measured at a minimum of three locations that are widely distributed over a vessel. This, in essence, is the key concept behind the ABB Ability™ OCTOPUS Marine Advisory System, a ship operations performance management package that uses motion monitoring →01 [1] to quantify the risk of losing containers due to excessive accelerations in wave conditions.
Although only a tiny percentage of the six to seven million containers in transit on the water at any given moment, the estimated 1,500 containers that are thought to be lost each year can have significant consequences. Aside from short-term financial costs, reputations are at risk. Environmental impacts can also be a major concern – particularly when the cargo in question is hazardous. Meanwhile, stray containers – whether afloat or on the seabed in shallow waters – represent a potential threat to marine habitats and navigational safety.
Weather forecasts, which include information on sea states, are fundamental to predicting vessel motions and the associated forces exerted on cargo. With accurate insights into conditions at sea, shipmasters can avoid areas where vessel motions are likely to be most severe. Simply considering the height of waves may not be sufficient, however, as the distribution of wave periods and wave direction relative to a ship’s heading can have a greater impact on acceleration levels than wave height alone.
In view of this, protecting cargo against excessive loads is best achieved by using an automated process known as “vessel response forecasting” in which forecast wave conditions are translated into predicted vessel motions. Knowledge of how a ship responds in different sea states is essential to this process; here, its motions in a range of wave directions, periods and heights are recorded over time – with vessel speed and loading condition also taken into account – and stored in a database. Based on this information, OCTOPUS supports real-time decision-making in voyage planning and execution →02. Indeed, it has accomplished this so successfully that ABB estimates that the system is currently utilized by around 90 percent of the semi-submersible heavy lift ships in operation worldwide.
In addition to providing users with detailed information about current conditions, OCTOPUS helps to identify the risks related to vessel motions when changing heading or speed. Motions such as roll and pitch are calculated for the full range of headings and ship speeds and compared with an upper limit. Vessel motion risk management of this type is already a powerful safety tool in the project cargo market, where heavy lift ships transport huge, unwieldy cargoes.
Supporting new wind energy farms
Alongside improved safety, vessel response forecasting based on the OCTOPUS platform also brings efficiency gains. ABB’s ship-type specific expertise in hydrodynamics ensures that OCTOPUS capabilities are transferrable across a growing range of vessels, including wind turbine installation vessels, where there is a direct relationship between minimizing vessel motions and maximizing the operational window →03. For example, a forthcoming vessel for Louis Dreyfus Armateurs will leverage OCTOPUS as it serves the world’s largest offshore wind farm.
OCTOPUS is also making a key contribution to the far-reaching European Union-backed ‘Project ATLANTIS’ research initiative, which is designed to develop new wind energy fields in the Atlantic Ocean, two of which are located off the coast of Viana do Castelo, Portugal. A newly developed OCTOPUS module will provide actionable insights to help onshore operators optimize the planning of missions from port to wind farm, cut transfer times between land and wind farms, and reduce vessel waiting time and on-site worktimes.
The new module will also take into consideration the operational limitations of associated ships and personnel and assess deployment opportunities for remotely operated underwater vehicles (ROVs), unmanned surface vehicles and unmanned aerial vehicles. This is an industry first as it allows onshore users to plan offshore operations according to the performance of a vessel, crew and equipment in the actual conditions they face. It is also a significant step forward for remote decision-making: in adverse weather or rough seas, a mission or an ROV launch could be aborted to save a wasted deployment or worse. All of this adds up to clear benefits for safety as well as efficiency.
Although the latest addition to the OCTOPUS suite was developed with ATLANTIS in mind, ABB’s vision is to develop the module to serve multiple sectors, such as the cruise industry, where it could be used to plan short routes, and the offshore oil and gas industry, where it could map supply operations for rigs and floating offshore units.
References
[1] ABB. ABB’s OCTOPUS advisory system predicts safer, more efficient ship performance. Available at: https://new.abb.com/news/detail/76792/abbs-octopus-advisory-system-predicts-safer-more-efficient-ship-performance [Accessed October 10, 2021].
Title photo: ©enanuchit/stock.adobe.com
