August 11, 2010
ShipArrestor system completes test
Miko Marine AS, of Oslo, has successfully completed the first full-scale test of its ShipArrestor system. This enables a helicopter to attach a sea anchor on a tow line to an unmanned vessel such as a tanker that is drifting without power.
By reducing the speed of the ship's drift, the ShipArrestor increases the time available for rescue tugs to reach the vessel before it runs aground.
The trial was undertaken in association with the Norwegian Technical Institute and Norway's Coastal Administration. It took place recently off the north coast of Norway using the 147,000 cu.m, 288 m long LNG tanker Arctic Princess which was made available by Hoegh LNG and Statoil.
The tests were conducted in two phases. In the first, a helicopter operated by Luftransport successfully "lassoed" the winch gear and bollards on the foredeck of the Arctic Princess.
This was easily accomplished with a version of the connecting ring and the lightweight chain that will be by the system. It used a substitute material for the chain that had the same weight and handling characteristics to avoid the possibility of the chain causing damage to the forecastle of the Arctic Princess.
The helicopter pilot encountered no problems attaching the tow line to the ship and in releasing it correctly and Claus Christian Apneseth, project manager for Miko Marine is now confident that the procedure is viable.
The second phase of the trial was completed shortly afterwards. It tested the performance of the sea anchor itself and was completely successful.
A 30 m diameter nylon parachute anchor was deployed from the Arctic Princess by a tug. It then turned the LNG tanker up into the wind in less than 20 minutes and reduced its rate of drift by 58 per cent.
"We have identified some small design improvements that can be made to the anchor, but in a genuine emergency its performance could have been the difference between the successful recovery of an oil tanker or its being wrecked," said Mr. Apneseth.
Until now, the use of sea anchors has been restricted to smaller vessels. Part of the project has been to include the mathematical modeling needed to identify the size of sea anchors needed for ships of different tonnages. This impacts upon the sea anchor's weight and its ability to be carried by helicopter. Similar constraints apply to the tow line which must be strong and also capable of resisting abrasion against the ship's winch and gunwhale.
This has led to the development of a unique lightweight chain that is half the weight of conventional chains offering the same performance.
It is also believed that the research will lead to the development of sea anchors that can be permanently carried aboard ships for emergency use.
The recent loss of a jack-up platform for windfarm installation from a heavy lift vessel when its engines failed in mid-Atlantic shows the dangers arising from excessive roll when a ship is unable to turn into the wind. Miko Marine is confident that a solution now exists for this type of hazard.
Miko Marine holds the patent for the ShipArrestor principle. The system is being developed with help from an EU investment grant and a consortium of eight European organizations that includes the Norwegian Institute of Technology and the UK's Ship Stability Research Center.
It is hoped that the Norwegian Coastal Administration will become the first to buy ShipArrestors which it would be expected to keep at its depots around the Norwegian coastline. They would then be readily available in an emergency and could reduce the likelihood of groundings and the pollution that can result from them.