02 August 2010

Dr Hans Cozijn: “Tests on the DIFIS solution proved successful also in deep water and severe storm conditions”

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The DIFIS structure was then tested in extreme storm conditions simulating waves twelve meters high. Below the water, the buffer bell and the dome hardly moved. The installation of the whole structure remains the real challenge 

Hans Cozijn is Senior Project Manager at MARIN, the Maritime Research Institute in the Netherlands, which specialises in testing designs of ships and oil platforms. MARIN coordinated the consortium set up to test and refine the DIFIS concept, an innovative solution to fight oil spills. MARIN already built a scale model of this solution. It is 12 meters tall and in a deployment test, the folded dome with the oil reservoir opened successfully over the oil spill of a tanker wreck, even in strong currents.

We understand that the device is huge – the dome can be a hundred meters across, the riser tube kilometres long and the buffer bell the size of a house. Could this actually be done in a powerful, dangerous environment like the ocean?
The concept itself seemed feasible, although I realised immediately that in very deep waters it would be complex to install such a system. Also, it was not immediately clear if, in deep water conditions with strong currents, if the system could work. We set up a test in our offshore basin. In our basins we can model environments of currents, waves and wind, and we tested different wave conditions, everyday operational conditions but also severe storms. DIFIS was put through a number of trials. One of these was to see if the structure would deploy correctly in strong currents.

Did you manage to test the structure in extreme weather conditions?
Yes, we managed to test if the dome would still open correctly in severe storm conditions . By remote control, the lines are released, and the lifting bags pull open the dome. Also we investigated different cases where one or two of the lifting bags were failing, and also in these cases the dome unfolded correctly. The structure was then tested in extreme weather conditions, subjected to the equivalent of waves twelve metres high. In this test we measured the motions of the buffer bell but also the tensions in the mooring lines and the riser tube. The results of these tests show that the motion of the buffer bell were relatively limited and also the loads in the lines did not exceed the design limit. This is important because the structure might have to be in place for several years, so it needs to be able to survive any storm in that could pass by.

Do you think that the DIFIS solution would therefore work?
Once it’s installed, I think it will function very well. The main challenge is installing it.

 

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