The shipping industry has long known about the dangers of parametric roll, with researchers working to broaden understanding of the phenomenon that is increasingly linked to damage to containers and car carriers. Today, a Danish company that manufactures a wide range of sensors reports that it has developed and tested a system on container ships that can alert crews to danger or even automatically adjust a ship’s course before it does not begin the rolling phenomenon.
It is believed that the hull shapes of modern container ships and car carriers make them particularly susceptible to parametric roll. In the worst case scenario, during a series of uncontrollable movements, ships have reported tilting up to 46 degrees in a very short time. Investigators have long believed that these incidents, which often occur quickly and without warning, have contributed to container stacks collapsing and containers being lost overboard, such as the recent incidents with the ONE Apus, the APL England and several Maersk ships.
An ongoing three-year study by the container shipping industry has already identified that parametric roll in the following seas is particularly dangerous for container ships. The project is performing tests and measurements to better identify causes and how they can be addressed, but so far has largely only been able to provide browsers with some general warnings and instructions.
Danish company Kjærulf Pedersen, which manufactures and develops sensors to measure temperature, humidity, CO2 and O2, now reports that it has developed a sensor system capable of recognizing trends that lead to parametric roll and to send a message to the ship’s control system in order to
the system and the crew have time to change course.
“Parametric roll can happen in just eight wave cycles, each lasting four to five seconds, and from roll to roll the list can be doubled. It’s impossible to detect, because it’s going very fast, and the situation is incredibly dangerous for everyone,” says Ole Egelykke-Milandt, sales engineer and project manager at Kjærulf Pedersen.
On the other hand, Egelykke-Milandt notes that it is enough to modify the course slightly so that the movements of the ship slow down again.
The company’s system is based on three sensors, placed at the bow, amidships and stern. All vessel movements are monitored in real time up to 100 times per second. The system compares observations to data on the vessel’s speed, acceleration and direction. The sensors detect if the movements are approaching a state that can get out of control and notify the vessel’s control system so that the course can be changed and uncontrollable tilts avoided.
Since January, the system has been installed on four large container ships that sail between China and the United States, and the company reports that its tests with Maersk have shown that the system is successful in recognizing the warning signs of the parametric roll. Kjærulf Pedersen reports that the system is now implemented across the shipping company’s container fleet.
“In the long term, it is expected that the data from the ships will flow to a central location so that all the ships of the shipping company can use the data collected. In this way, we obtain an algorithm that is increasingly improving for predict dangerous situations, thereby significantly increasing safety,” says Egelykke-Milandt.
The large amount of data from the sensors will also be used for other improvements such as the weight distribution and trim of the vessel in the water.