Inventory Ship Routing and Cargo Stowage Planning on Chemical Tankers

Chemical tankers are a type of ocean carrier with multi-compartments to simultaneously carry various liquid chemicals in bulk and prevent their mixing. This paper discusses the difficulties chemical tanker managers experience when planning vessel routes and scheduling inventory maintenance because of chemical tankers’ unique characteristics and operational constraints. To date, no models have addressed chemical tankers’ inventory routing and scheduling needs while accounting for these challenges. Bridging the research gap, we propose a novel, integrated, mathematical model of inventory ship routing and stowage planning problem (ISRSPP) for chemical tankers. We seek to combine stowage planning, which is an operational problem, with inventory ship routing, which is a tactical problem, through integrated tactical planning. Our objective is to propose a solution with minimal total voyage costs. For this purpose, we formulate our problem in a mixed integer linear program. We build two scenarios to analyze the models applicability and performance, and we solve both of them using a commercial solver. Our results confirm that the stowage planning problem cannot be separated from the inventory ship routing problem for chemical tankers because such a separation could lead to fleet routes for which no feasible stowage plan is possible