Reliable and continuous operation of ships is vitally important to the decision-makers. Driven by the rising cost of newbuilding ships, maintenance actions are needed on existing ships to ensure safe and enduring service beyond their initial design life. Extending ship service life can provide economic operating profit and promote sustainability. Meanwhile, ships during their extended service life may involve higher failure risk and additional maintenance expenditure. Therefore, a cost-benefit evaluation is imperative for determining the optimal duration of service life extension (SLE) and the associated maintenance actions. In this paper, a novel method for this purpose is proposed. Two cost-benefit indicators, benefit-cost ratio (BCR) and net present value (NPV) are used to optimize the duration of SLE. Using Bayesian updating, information on the remaining design life and the structural condition at the SLE decision is incorporated into the optimization process to better inform SLE decision-making. The proposed method is illustrated by a fatigue-sensitive very large crude carrier (VLCC) at both structural component and structural system levels.

船舶的可靠连续运行对决策者至关重要。在新船造价上涨的推动下，现有船舶需要采取维护措施，以确保在其最初的设计寿命后仍能提供安全，持久的服务。延长船舶使用寿命可以提供经济的运营利润并促进可持续性。同时，延长使用寿命的船舶可能会带来更高的故障风险和额外的维护费用。因此，必须进行成本效益评估，以确定使用寿命的最佳延长期限（SLE）和相关的维护措施。在本文中，提出了一种用于此目的的新方法。两个成本效益指标，效益成本比（BCR）和净现值（NPV）用于优化SLE的持续时间。使用贝叶斯更新，有关SLE决策的剩余设计寿命和结构条件的信息已纳入优化过程，以更好地为SLE决策提供依据。疲劳敏感的超大型原油运输船（VLCC）在结构部件和结构系统水平上都可以说明所提出的方法。