Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology / Logistic Engineering
C.J. van Nielen Het lossen van bulkschepen. Een simulatiestudie naar losstrategieën en invloedsfactoren. Masters thesis, Report 99.3.LT.5264, Transport Technology, Logistic Engineering.
Ertsoverslagbedrijf Europoort C.V. (EECV) is one of the biggest transhipment companies for iron ore in the world. On a yearly basis EECV handles about 50 million tons of iron ore. The target of EECV is to combine a minimal lay-time for ships on the seaside, with a maximum service to the hinterland. A study has been performed which focuses on the seaside of the EECV- terminal. For the seaside several unloading strategies will be tested and a sensitivity analyses will be performed.
After a description of all processes at EECV, the unloading process has been modelled. The unloading of a ship is subjected to several conditions. To prevent high stress in the ship, each hold has to be unloaded proportionally. For the modelling of the seaside, much attention has been paid to find a good method which gives cranes assignments to unload quantities of iron ore from the holds. The method must combine logical assignments with the condition that each hold must be unloaded proportionally. In the model, cranes are given the assignments to unload quantities of iron ore from the holds by a "activity network".
For the seaside a simulation model has been made. With the simulation model several unloading strategies have been tested. For ships transporting one sort of ore, there is a strategy to reserve one crane for another ship in the final phase of unloading. The other two cranes will perform the final phase of unloading for the first ship. By a smart way of giving cranes assignments, a high filling of the conveyors can be brought about. This "smart" strategy is tested against a normal situation in which three cranes complete the unloading of a ship. For ships transporting two sorts of ore, the strategy to unload one kind of ore at a time, is tested against the strategy to unload two sorts at a time. Next to these unloading strategies, a sensitivity analysis is performed for the following points:
The capacity of the cranes; The availability of the cranes;
The availability of the conveyors on the seaside.
The simulations show that the strategy to reserve one crane for an other ship (when unloading a ship transporting one sort of iron ore), can give a higher production for EECV. The lay-time of the first ship will increase with about 15 hours. But the total production in the same time span increases too. Every time EECV must determine if the increase in lay-time is allowed and if the increase in production balances the increase in lay-time.
For ships transporting two sorts of ore, the strategy to unload one sort of ore at a time, gives better results than the strategy to unload two sorts at a time. With the strategy to unload one sort of ore at a time, the cranes and conveyors will have to treat an other sort of ore less times. Because of this the lay-time of a ship will decrease.
The unloading of ships at EECV, seems to be most sensitive for the capacity of the cranes. The sensitivity analysis shows that a varying capacity of the cranes, has a large influence on the lay-time of ships. The availability of the cranes and the conveyors, have less influence on the lay-time. This result pleads in favour of further research on grabs used for the unloading. If good grabs are used, the capacity of the cranes will increase and the lay-time of ships will decrease.
The method to give cranes assignments via an activity network, gives good results. This way of giving the assignments gives a good representation of the real unloading process.
Reports on Logistic Engineering (in Dutch)
