Optimization Study On Economic Speed Of Tramp Ships

In tramp shipping market, the cargos are always in large volume and are distributed unevenly. At the same time, the loading and unloading ports are scattered all around the world. For now freight rates are in downturn while fuel prices are rising continuously, coupled with tramp shipping market information is dispersed, how to minimize operational costs by using economic speed to maximize fleet utilization and fleet operating profit has become a serious problem for shipping company. It has also gradually attracted more attention and research.We focused on the economic speed in tramp ship scheduling problem, considering multi-ship types, multi-batches and multi-routes. The goods to be carried includes contract cargoes and spot ones. In the case of certain routes and certain speed range, we discrete the ship speed, which means in each voyage period ship has limited speeds instead of unlimited speeds to select. Then we establish mathematical model of tramp ship scheduling based on speed optimization. We take the speed as a decision variable. Therefore, different speeds can cause variation in voyage time and fuel consumption, thereby influences the total receipts of scheduling.To solve this problem, a tabu search algorithm is designed due to the complexity of the problem and limitations of traditional mathematical programming approaches, especially when large-scale problems are involved. Finally through the practical case analysis, the result shows potential economic effectiveness of considering variable speed and fuel consumption in tramp ship routing and scheduling problems. The formulated model and proposed solution scheme can help tramp shipping companies to optimize ship’s allocation, freight assignment in routing and scheduling.Economic speed is lower than normal level, so the tramp needs to slow down to achieve its requirement. To ensure the implementation of the economic speed safely, scientifically and effectively, considering the actual situation, we should make clear the specific procedure of corresponding maintenance and management measures of lowering ship’s speed, only in this way can ensure the normal operation of the ship.