Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology
H.A. ter Horst Vessel stowage planning for the Floating Crane Concept. Literature survey, Report 2006.TL.7086, Transport Engineering and Logistics.
A research project entitled "The Container Terminal of the Future" is aimed to generate new ideas to accommodate the increasing demands on the container terminals in the future. One idea that resulted from this project was the application of a floating crane for board to board (ship-barge) container transfer. The floating crane is placed alongside a moored deep-sea vessel, making it possible to load and discharge the ship from both sides. The containers discharged by the floating cranes are loaded onto barges, which transport them further. Obviously, this process can also be reversed for loading a deep-sea vessel.
One of the critical aspects identified for the floating crane concept is the increased complexity of the container stowage problem. Determining a viable arrangement of containers to facilitate the process of container handling, in a cost-effective way, makes up the container stowage problem. This report aims to discover what the possibilities are for the implementation of the floating crane concept using the current vessel stowage planning employed by APM Terminals and Maersk Line.
A number of models have been developed attempting to optimise the container vessel stowage problem. However, because of the number of constraints involved the problem is NP-Hard. This means that it is impossible to guarantee that an optimal solution can be found for commercial sized ships within a practical processing time. In practice therefore, these models are not implemented. Software support packages, which store details about each container and calculate loads and moments on the vessel, are used combined with human judgement by operators.
Maersk Line has planning offices in London and Singapore. The London office handles all the ships arriving in ports between the east coast of the America's and the east coast of Africa and Europe, up to the Suez Canal. The planners in the London office make the load plan which shows where the containers are to be loaded onto the vessel. At the terminal itself the loading sequence is determined and constraints, such as maximum stack weights, are checked using a computer programme. The terminal also receives the current container layout of the vessel and uses this to determine the discharge sequence. Before the vessel can depart, the captain must approve the final container layout.
Approximately 5 million containers (9 million TEU) flow through the Port of Rotterdam per year. A primary market for floating cranes, the barge containers, make up 22,7% of these. When looking specifically at APM Terminals in Rotterdam the barge containers make up almost 26% of the approximate 680.000 containers per year.
Four different case studies are used to investigate different methods of introducing the floating crane concept without making changes to the current vessel stowage planning. Two floating cranes are added to the 7 quay crane schedule of an example vessel resulting in a decrease in the vessel mooring time from 17 to 15 hours. Handling costs increase when the floating crane is introduced. However, the use of a hub terminal, located roughly 50km inland from the Port of Rotterdam, reduces the increase. The use of the hub terminal also results in a decrease in the storage costs. A fifth case study introduces a change in the stowage planning by grouping barge containers on the vessel. This results in the lowest total handling costs.
It is found that various methods of introducing floating cranes whilst using the current vessel stowage planning are possible. One or more floating cranes can be used to handle containers on deep-sea vessels in combination with quay cranes. They are able to work on bays adjacent to those being worked on by the quay cranes, enabling the maximum berth capacity to be increased.
The most critical aspects that arise when introducing floating cranes are twofold. Firstly, the use of a hub terminal for secondary container handling. Its use limits the increase of the total handling costs. Second is the approach the floating cranes take when handling containers. It is critical that floating cranes are not selective in the types of containers they handle so long as the current vessel stowage planning is used. Handling only specific types of containers causes the overall container handling efficiency to decrease to such an extent that it is no longer financially viable.
In the future it is worth looking at the costs and implications of making changes in the current stowage planning. The last case study implies that by grouping certain types of containers on the deep-sea vessel, handling costs can drop below their present values.
Reports on Transport Engineering and Logistics (in Dutch)
