A VESSEL MOTION FORECAST TOOL

Some 13,000 ships enter South Africa’s eight ports annually. These ports process some 10,000 containerised loads per day. Many industries rely on imports and exports via the country’s ports, where a safe port environment, with minimal disruptions while loading or offloading cargo, is critical. Delays at ports, caused by weather events and uncontrollable environmental factors such as wind and waves, are common and have far-reaching impacts. Ports around the world face these factors, which impact their operability and interrupt operations. The motion of moored vessels can contribute to operational hindrances and downtime of the port. It can also result in the breaking of mooring lines during larger environmental events.  One of the main contributing factors to mooring problems is long-period waves. These waves result in varying ship motions at the berths inside a port, making it difficult for port operators to predict the impact of the resulting ship motions. Solutions to manage the impact of long-period waves on moored vessel motion can be very costly and often involve making structural changes to the ports or adopting specialised mooring systems. Downtime at ports can be reduced with proper port planning and strategies, such as where, when and what size vessels can be moored safely for optimal operational conditions.

A new CSIR-developed tool can predict the motion of moored ships in a port, for both current wave conditions and forecasted wave events, contributing to operational efficiency and port safety. First tested in the Port of Ngqura, northeast of Gqeberha in the Eastern Cape, South Africa, the tool can be set up to be port-specific and can be integrated into most existing infrastructure.  The vessel motion forecast tool helps with the management of mooring and long-period wave problems at ports. Predicting the effects of long-wave events on moored ships can be challenging for port operators, but the CSIR-developed tool allows them to readily assess the impact of long-period waves on particular vessels at specific berth locations inside the port, removing any guesswork. This is achieved by linking numerous state-of-the-art numerical models, enabling the modelling of complete long-period wave climates and the resulting moored ship motions. The CSIR has been providing long-wave forecasts to the ports of Ngqura, Cape Town and Saldanha Bay for many years, and although this system has been proven to work well, the impact of these long-period waves on moored vessels at the respective ports has not been quantified. Recent experience has highlighted the fact that port operators are unable to readily assess and quantify the impact of long-period waves on a particular vessel based on the forecast alone. Although the port operators might be aware of a long-period wave event on the horizon, they are unable to determine what, if any, effect this will have on port operations. From the prevalence of adverse wave activities experienced at ports, a clear international opportunity for the creation of this tool has been developed from mature capabilities.