A SWELL SOLUTION FOR DOVER
Dover is to be the first European port to install an automated mooring system using vacuum technology and developed by Mooring Systems (MSL), following the signing earlier this year of a European licensing agreement between MSL and Cavotec Group in the Netherlands. David Foxwell explains.
Speaking to PS, technical director Robert Weber says MSL has completed construction of the MoorMaster 800 vacuum mooring system for Dover, which, he anticipates, would be installed between December 2004 and January 2005.
Weber says Dover, the busiest ferry port in northern Europe, had selected the vacuum-based automatic mooring system for the new piers that it is building to overcome problems that the port and ferries using it have with swell. The port has a normal tidal range of 7metres, but this can increase to as much as 10metres at times.
"A report commissioned by Dover Harbour Board determines that the very specific environmental conditions encountered by ferries using the port are mostly determined by surge, and has led to traditional steel mooring wires breaking at times, " Weber explains.
"Ships coming alongside the quays have to use their main engines to push into the berth, which is bad news for the engines, and leads to additional fuel consumption and unnecessary emissions in the port environment." As Weber also explains, using the engines in this manner to berth ships also creates significant propeller wash, which has been undermining existing structures.
The MoorMaster 800 is a shore-based version of the MoorMaster unit that is designed to meet the needs of larger ships in exposed seaway conditions where high windage is common. Instead of a rope, vacuum pads are used to provide the mooring attachment. Each pad has a measurable working load, providing a powerful physical attachment between ship and shore.
MSL's vacuum pads have been tested and rated under the supervision of classification societies DNV and Lloyds Register. When combined with the innovative, three dimensional supporting apparatus, the mooring units emulate the range of movement, resilience and elasticity of a line mooring. The vacuum pads can also cope with extensive surface irregularities and are able to slide under extreme loads without significant seal deformation or loss of attachment.
Because the mooring units attach to the ship closer to the waterline and immediately counteract mooring forces, the system has a greater mooring efficiency than angled ropes. By using internetbased control software the system permits the user to monitor performance clearly communicating all essential mooring load information in real-time. Mooring load information is produced from the measurement of vacuum efficiencies and from monitoring athwartships and fore and aft hydraulic cylinders. With a full knowledge of the mooring conditions at all times, the operator has complete control and understanding of the moored state of the vessel.
The unit ranges up and down the quay face, and in the installation at Dover is designed to cope with tidal variations of up to 10metres and surge conditions causing vertical, or fore and aft movement, of up to 1metre per second. Typically between three and four units will be required for large ro-ro vessels with substantial windage area. The MoorMaster 800 has a design load of 80,000kg and outreach of 2,500mm.
After the initial MoorMaster 800 has been installed, tested and accepted into service, Dover is expected to acquire several more units, so that each of its new ferry berths has three of the units, manufactured by Cavotec.
Weber says the MoorMaster units were also attracting significant interest in other parts of the world, including certain Japanese and Korean ports that are subject to the long wave phenomenon which can lift ships at berth and cause significant operational problems through berth creep. This, says Weber, could cause problems for gantry cranes unloading vessels in ports subject to the phenomenon, and has been known to reduce crane efficiency by as much as 75%. To-date, berth creep caused by the long wave phenomenon has tended to be solved by constructing breakwaters, at huge cost to the ports involved.
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