One of the most critical activities in a refinery is the scheduling of loading and unloading of crude oil. Better analysis of this activity gives rise to better use of a system's resources, as well as control of the entire supply chain. It is important that the crude oil is loaded and unloaded contiguously, primarily for security reasons (e.g. possibility of system failures) but also to reduce the setup costs incurred when flow between a dock and a tank or between a tank and a crude distillation unit is reinitialized. The aim of the present paper is to develop an exact solution approach, widely applicable to most refineries where several modes of blending and several recipe preparation alternatives are used. A novel time formulation is proposed for the scheduling of the system under study called event-based time representation where the intervals are now based on events instead of hours. (C) 2009 Elsevier Ltd. All rights reserved.