Safety vs. Sustainability – How Much Underpowering of Ships Is Acceptable?

Abstract

The present EEDI regulations have a strong impact on ship design. Especially for tankers and bulk carriers, the regulation results in the reduction of the installable main engine power. In 2020, the next EEDI reduction phase is put into force with the consequence that the main engine power of these ships will be reduced even further. The development helps to reduce emissions, especially greenhouse gases, but it puts challenges on ship safety, as the ship must still be maneuverable even in bad weather conditions. Recently, a grounding incident of a bulk carrier sea took place in the German Bight where the ship was dragging its anchor although the main engine was running at full speed. Numerical investigations of this accident showed that the environmental forces acting on the ship were larger than the sum of propeller and anchor forces. This incident was an excellent opportunity to investigate whether our existing numerical calculation methods are able to cope with such kind of incidents and whether it was possible to investigate the root cause of that particular grounding event. The paper gives an overview about the numerical investigations of the grounding event which address course keeping in heavy weather including anchor forces. Additionally, operational aspects of the main engine operation and the propulsion control systems are considered. The ship did not need to comply with the existing EEDI regulations. Therefore, the paper addresses also the effect of reduced main engine power on this particular incident, because it is obvious that reduced main engine power will make such incidents more probable, as limiting environmental conditions for a ship with less power will be less severe and therefore more probable.