Electro-hydraulic sway control system for container cranes

On ship-to-shore (STS) cranes with crane bridges up to 50m high and on rubber tyred gantry (RTG) cranes with an installed height of approximately 30m, a container may sway from side to side over a distance of up to 8.50m, requiring up to eight seconds tocomplete one amplitude. The degree of amplitude is in direct proportion to the weight of the container. 

The sway of the container can represent a considerable delay in completing the loading process, as the load cannot be lowered into position until the swinging has settled. The new system from Gerhard Ruppel Hydraulik allows the amplitude and therefore the oscillation period of the container to be reliably reduced to a minimum.

Ruppel Hydraulik launched its first 'Anti-Sway System' back in 2008. In this system, four attenuation cables were strung diagonally to the direction of sway. During the loading process, the slack in the cables was taken up by a hydraulic unit complete with integrated control block. However, in this previous system only two pre-set hydraulic pressures could be selected.

The new generation of systems uses the same basic principle, but also includes integrated electronics. This results in greater accuracy when setting the system pressure so that it is proportional to the weight of the container, and therefore also greater accuracy when it comes to the requisite pre-tensioning. It also means that constant pressure monitoring can be achieved.

“Our new Anti-Sway System gives us maximum system reliability by combining process-capable hydraulics with the control potential of the electronics,” explains Gerhard Ruppel. “The outcome is much more fail-safe than other solutions, such as purely electronic ones.”  

The electro-hydraulic sway control system also has an energy-saving influence on the crane as a whole, as the reduced sway results in less kinetic energy being expended in the sub-system of lifting gear, load-carrying unit and load. This means the crane does not need as much energy for acceleration, and less energy goes to waste when decelerating. 

Ruppel Hydraulik is developing the system for new crane installations or for retrofitting to big STS systems as well as smaller RTG cranes which are already fitted out with four anti-sway cables. Its straightforward modular design means the system is easy to operate and does not assume any particular training on the part of the crane operator.