SCHEDULING OF VESSELS FOR SHIPMENT OF BULK AND SEMI-BULK COMMODITIES ORIGINATING IN A SINGLE AREA

The continuous growth of the world population and of its standard of living increases the dependence of the world economy on the proper functioning of its sea transport component. Various economic and political reasons compel large shippers to attend to the shipping of their commodities, mainly in bulk and semi-bulk trades. Improving the economic performance of the fleets of such shippers is the object of this research.; The problem dealt with in this research is how to assign available fleet to a given set of shipments while minimizing the costs of that fleet. The cost function which is minimized consists of the cost of the vessel on a daily or per unit shipped basis, port entry charges, cost of ships' time in unloading ports, and demurrage for idle vessels.; The primary objective of this research is to analyze the scheduling of vessels for shipment of bulk and semi-bulk commodities originating in a single area, and to find out ways to reduce the cost of such scheduling. A second objective is to find the effects of allowed tolerance in shipment sizes on the cost of the schedule, and the effects of limiting the number of unloading ports per vessel on that cost.; Three scheduling algorithms are developed: a heuristic algorithm, a biased random generator of schedules and an optimizing algorithm. The results of these algorithms are compared to the industry practice of sending the larger ships to the farther destinations. The algorithms are compared on five test problems, which differ mainly in their size, representing a realistic spectrum of operations. The data for the test problems are drawn from a data base which is built from information in trade publications and industry sources.; The major conclusion of the research is that remarkable cost savings can be achieved by using the proper scheduling method. These savings may, depending upon the specific case, be as high as 34%, in comparison to the industry practice. In financial terms these savings may amount to hundreds of thousands, even millions, of dollars, annually, Tolerance in shipment sizes does not reduce the scheduling cost, and, to a lesser extent, so does an increase in the limit of unloading ports per vessel. The magnitude of the cost decrease of these two parameters depends to a great extent on the specific case.