Big ships and old rope

As ships have got larger, the effect of their wake on vessels they pass in port has increased and is capable of overcoming mooring systems and affecting loading operations.

The wash from passing ships can exert large forces on moored vessels, mooring lines and fender loads, creating dangerous conditions, according to a joint industry study Research on the Passing Effects on Ships (Ropes).

Wash effects were shown to be able to cause moored ships to come loose and affect the safe loading and unloading of vessels, the three year project reveals.

The research also found that forces from the wash are directly influenced by the shape of a port basin, the size of the vessel, the passing distance and speed.

“Our research has identified the full effects of a passing ship’s wash and the impact is serious,” said Marco Pluijm, Bechtel ports-sector manager and chair of Ropes.

Container cranes, loading arms for oil and LNG and automated dry bulk excavators generally allow limited horizontal vessel motions which can be exceeded, and mooring equipment was often found to be incapable of resisting forces exerted on ropes and winches.

Ropes researchers have developed a software program to improve safety and created guidelines for use in the design of future ports based on the findings.

The Ropes group of 25 members includes port authorities, maritime research institute representatives, pilots, linesmen, and hardware suppliers, plus port engineering and construction group Bechtel.