ShipArrestor Project

By Keith Henderson at July 08, 2010 06:30
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Last month a system called ShipArrestor was tested by consortium leader Miko Marine AS, Norway as part of a two year EU funded program started in Oct 2008 to try to develop a system to prevent such disasters. In the 1990’s there was a Norwegian project called NepCon which researched possible ways to bring a stricken ship under control. It was impractical for a number of reasons but mainly because ropes chaffed and when substituted with chain of sufficient strength. it was too heavy for the helicopter to lift it! Under the ShipArrestor program a special steel chain is used that is lighter than the proposed titanium chain. So the helicopter can drop the lasso over the windlass is achieved by putting the chain inside an inflatable collar of about 6m diameter. Once the windlass is ringed, a 30m diameter sea anchor can be deployed to bring the bow round, reduce roll and slow the drifting until a tug can commence towing. In June 2010, the complete ShipArrestor system was tested and was considered a major success in proving its functionality and practicability, however the calm weather conditions were too good to give any definite indication as to how the system would behave in a real life situation. Further tests will be made: the program is due to run to September 2010.
We have all seen the desperate situation of a disabled or abandoned ship drifting helplessly toward a lee shore and about to founder with devastating if not catastrophic consequences. Last month a system called ShipArrestor was tested by consortium leader Miko Marine AS, Norway as part of a two year EU funded program started in Oct 2008 to try to develop a system to prevent such disasters.

In the 1990’s there was a Norwegian project called NepCon which researched possible ways to bring a stricken ship under control. A technique was investigated to lasso the windlass and or bollards in the bows and deploy a sea anchor or provide a means to tow the ship to safety. It was impractical for a number of reasons but mainly because ropes chaffed and when substituted with chain of sufficient strength. it was too heavy for the helicopter to lift it!

Under the ShipArrestor program, several alternatives to the chain problem were investigated and the only apparent solution appeared to be a chain made out of titanium. Manufacturing titanium chain is very difficult if not too difficult however a FSU space and defense metallurgical institute came up with an alternative steel chain that was lighter per ton and with a greater breaking strain than the originally proposed titanium chain. The next problem was how to keep the lasso open so the helicopter could drop it over the windlass. This was achieved by putting the chain inside an inflatable collar of about 6m diameter. Although this operation is not easy, helicopter pilots are adept to this sort of task as it resembles their work routine in the oil & gas industries.

Once the windlass is ringed, a 30m diameter sea anchor can be deployed to bring the bow round, reduce roll and slow the drifting until a tug can commence towing. The sea anchor diameter is critical; without the anchor the ship normally lies beam on and the hull itself acts like a sea anchor. If a too small sea anchor is deployed, it pulls the bow round and the decreased hull area with the small sea anchor is less than the hull beam on, so the drift rate actually increases.
In June 2010, the complete ShipArrestor system was tested just off the North Cape in arctic Norway. One helicopter, one tugboat and one LNG tanker participated. The tests were considered a major success in proving its functionality and practicability, however the calm weather conditions were too good to give any definite indication as to how the system would behave in a real life situation.
There were some minor problems in handling the system and some flaws in the test procedure which should be rectified prior to the next set of tests. The program is due to run to September 2010.

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