Scheduling of raw-material unloading from ships at a steelworks

Abstract

Formulating a schedule for unloading raw material from ships at the seaport of a steelworks is a difficult task. Even in its simplest possible form, finding an optimum solution for the problem is nondeterministic polynomial time (NP)-hard. The problem at a steelworks gets more complicated due to several factors, such as the difference in capacities of unloading equipment, the requirement of keeping ships balanced and the dynamic nature of berthing eligibility of each ship, as governed by the weight of the remaining payload. Moreover, the raw material must be transported through a network of belt conveyor units to designated storage yards while being discharged from ships. The combinatorial nature of this belt conveyor operation is analysed in this article. A heuristic approach to the raw-material unloading problem is proposed and its effectiveness was tested with real-world examples.