Risk-based life-cycle optimal dry-docking inspection of corroding ship hull tankers

The performance of the ship hull deteriorates randomly over time under corrosion attacks. To ensure the safe operation of a ship, dry-docking inspections are carried out on a regular basis to inspect, recoat, and renew structural members. The convention "at least two inspections every five years", implemented in the shipping industry, is empirically determined without much numerical evidence. Considering the expensive cost of drydocking inspections, it is crucial to study the optimal inspection interval in the presence of uncertainty. This paper proposes a risk-based maintenance decision-making framework for ships to address the optimal drydocking inspection. The minimum expected cost rule is used to explore the economically optimal inspection interval. Monte Carlo simulations are employed to obtain the probability distribution of the life-cycle cost. The costs considered include the cost of dry-docking and member renewal as well as monetary consequences of hull failure. A ship hull is utilized to illustrate the application of the proposed framework.