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Courtesy Seaway Heavy Lifting


pants wanted to go beyond this and incor- porate all the offshore aspects as well. “This is really a very ambitious project but the JIP proved that the technology is out there.”


During the OBELICS JIP several case studies were prepared by the participants, including a case with SHL’s heavy lift vessel Oleg Strashnov. Because a lot of effort had been put into the development of the models already, SHL decided to carry out several additional simulation exercises at MARIN’s headquarters in Wageningen. This took place in the summer of 2013.


SHL was keen to make the situation as realistic as possible and flew in engineers, offshore superintendents, crane drivers and DP operators, mobilising some 35 people from all over the world. “We also really wanted to link the office and offshore crew and we wanted to get feedback from every- one that would be involved so we can develop this tool.”


Flying everyone in meant that there hadn’t always been a chance for a thorough briefing but SHL and the team pressed ahead. “We knew this was stretching the limit and that we were of the limit of real-time calculation power.”


Stretching the limits Based on a real case, the simulation scenario involved a model of the Oleg Strashnov, together with a crane and barge. The Oleg Strashnov was working in DP-mode and the original DP computer was connected to the OBELICS environment. The SHL team had to ballast and submerge the cargo barge so the base frame structure would pick up sufficient buoyancy to bring the load within the capacity of the 5,000t Oleg Strashnov crane. Then they had to lift the base frame off the barge on DP, move out to the target location and set it down. The barge was not moored but was set on soft springs.


“This was complex, the barge had tanks so we had to include the stability particulars


and the base frame also had ballast compart- ments. We had to ballast the barge and the frame, operate the crane and tugger winches and the vessel ballasting system.” And this proved quite demanding on the system, which actually crashed several times. “We basically overloaded the processors! But we all went away, regrouped and went back with les- sons learnt from the first time. However, we are stretching the limits, there is no doubt.”


During the simulation exercise the team discovered several crucial factors for future development. “Importantly, the user interface has to be correct. The crane operator for example, is used to a certain interface. All the readings on the loads and outreach have to be there; if the interface is not right they don’t get the right feedback. And the same goes for all the ballast systems and tanks.”


Environmental conditions such as current and waves could be adjusted during the simulation to find the operational limits during the various stages. The participants


report 7


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