Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology
K.P. Tanis Logistic design and simulation of the unit handling of a selfloading unit ship system. TWAIO-project Design of Transport Systems, Report 94.3.LT.4320, Transport Engineering and Logistics.
Shortsea or coastal shipping can make a substantial contribution to the reduction of the congestion caused by road transport. However, to increase the competitiveness of shortsea with respect to land transport, the time spent in the port must be reduxced drastically. A considerable part of the time needed for trips by shortsea shipping is used for time consuming cargo handling activities in the port. The "Train Unit Loader" (TUL) concept, developed by a research group of the department of Maritime Engineering, dramatically reduces the cargo handling activities in the port. The concept is based on self (un)loading of units, for example containers or swapbodies, using a roll-on roll-off system with a special train of platform cars, called a train-loader. The train-loader used for this concept differs from a conventional train, it can be triple stacked and is adapted to the special requirements of the ship. By using the train-loader it is possible to (un)load many containers simultaneously in a short period. The handling of the containers is executed, while sailing, by an intemal automatic crane, cailed an under deck gantry. Consequently, because the terminal and on board operations are made independent, the turnaround time in the port will decrease.
MariTerm designed a conveyer loader concept called the High Tech Unit Carrier (HTUC). This concept has several decks and on each deck there are number of conveyer lanes for the storage of swapbodies as well as containers. In the midsection of each deck there is a transversal conveyer lane, this lane is connected with an elevator system. The conveyer lanes and the elevator are used to load and unload the units. On the terminal one or two parallel conveyer lanes are connected with the berthing place. The turnaround time in the port will decrease due to the fact that the number of handlings of a unit to be (un)loaded, while the ship is moored, is reduced to one.
This report describes the control and planning of the unit-handling on board of a unit load ship. The purpose is to develop efficient unit-handling methods for a decentralized handling system, to evaluate the performance of this system under different circumstances and to give advice on the layout of the ship concept. Using a logistic simulation model of the Train Unit Loader, the effects of both different kinds of cargo flow and of different kinds of ship layouts on the performance are evaluated. For two reasons conventional planning methods are not suitable for a ship with a process like the Train Unit Loader. First the use of guidelines for weight restrictions and for destinations allocated to parts of the cargo hold would make the control of the unit handling process too inflexible. Secondly, the ship has a high stability and therefore weight restrictions and exact stability calculations are not necessary for the unit handling process on board.
A complexity analysis showed that a mathematical method for the control of the unit handling could not lead to a workable situation. Therefore it was decided to develop unit handling policies for the unit handling on board as well as on the terminal. For both the terminal and on board four policies have been developed. An analysis of these policies using simulation showed that the following policies have the highest potential of giving a good performance.
On the terminal:
Order policy: Put the unit in a free stack onto the train-loader, containing no units that have to be unloaded in a port after the unit will be unloaded.
Dedicated stack policy:
Put the unit in a free stack onto the train-loader, containing only units for the same destination. On board:
Order policy: Put the unit in a free stack into the cargo hold, containing no units that have to be unloaded in a port before the unit will be unloaded.
Dedicated stack policy:
Put the unit in a free stack into the cargo hold, containing only units for the same destination.
The main conclusions of the lo istic analysis, using simulation, of the sailing schedule proposed by Wijnolst et al [N. Wijnolst, H.B. van der Hoeven, C.J. Kleiwegt and A. Sjöbris Innovation in shortsea shipping: Self-loading and -unloading unitload shipsystems Delft University Press (1993)] are:
compared to a random method, the policies mentioned above reduced the total unit handling time on the trip by about 25%;
the performance of the crane using these policies in units per hour is improved by 40% to 45%, leading to a production of about 29 units per hour; while sailing from Visby to Oxelosund, using the current under deck gantry performance, the sailing schedule will always have a delay, independent of the policies used, due to the large number of units which have to be handled.
To prevent delays you could restrict the maximum number of units, to the maximum capacity of the train-loader. Although this is true it is not a satisfactory solution, therefore I would like to recommend:
to increase the train-loader capacity, or;
to change the sailing schedule (For example by letting smaller but more ships sail, or by visiting a busy port twice in the same direction), or to expand the number of under deck gantries (This would also improve the reliability of the handling process but it will make the control of the unit handling process more complex).
The simulation model developed can be used to evaluate what the impact will be of the above mentioned recommendations. Reports on Transport Engineering and Logistics (in Dutch)
