COSCO SHIPPING Heavy Transport is expanding its extensive DP operational experience to a new area: decommissioning. We have been developing a unique topsides removal method called the Twin Lift Solution which utilizes multiple DP semi-submersible vessels to bring a significant cost savings to the decommissioning market. This development is supported by DNV GL, Shanghai Jiao Tong University (SJTU) and Trelleborg.
The method involves three DP vessels. Two semi-submersible vessels, with inter-connected DP system, will work in synchronized manner to remove the topsides in one piece from fixed and floating substructures, and then transfer the topsides onto a third larger semi-submersible vessel for transport. The whole operation is expected to complete in less than 8 hours. The transport vessel, after quick seafastening of topsides offshore, will sail the topsides directly to the disposal yard.
An engineering study completed by DNV GL has confirmed a pair of COSCO SHIPPING’s K-Class vessels and a single larger semi-submersible vessel are capable of removing topsides from a few thousand tons to beyond 40,000 tons.
Tank experiments have been conducted at Laboratory of SJTU. The whole removal method and the inter-connected DP system have been tested and confirmed feasible for offshore environment. Sea trial and full-scale tests are expected to take place in late 2019/2020.