Research on improving ship operating benefit by properly using ship´s load line

With the gradual increase of ship tonnage, the voyage operating efficiency becomes the core of competition. In actual operation, on the one hand, in order to improve ship carrying capacity, the phenomena of overloading and neglecting ship safety existed. On the other hand, due to the improper and wrong judgment of maritime supervising authorities, many ships didn\´t reach their maximum carrying capacity. And sometimes ships were detained or delayed due to misjudgment of overloading, hence caused unnecessary financial and reputation losses. The discrepancy of load line determination is the main reason. This paper analyzes the determining principle of load line and load line immersion based on interpretation of "International convention on load lines, 1966" properly. By using the methods of reasoning and checking, it discusses the judgment errors caused by the impact of hogging and sagging, inclination, and water density overboard, and proposes the correct methods of determining overload. It has a practical guidance for improving ship operating benefit, preventing overloading and ensuring operation safety.