Probabilistic investigations into the value of information: A comparison of condition-based and time-based maintenance strategies

Abstract

Optimal maintenance of marine structures is challenging due to numerous fatigue-prone components, serious failure consequences, high maintenance costs, harsh sea environments, difficult access, and uncertainties in fatigue loading, resistance, and inspection and maintenance activities. Time-based maintenance (TBM) is convenient to implement. However, condition-based maintenance (CBM) is proved to be more cost-effective. This paper assesses the value of information (VoI) by inspections in CBM, compared to TBM, and investigates the conditions for CBM to outperform TBM in terms of fatigue reliability. A probabilistic maintenance optimization method and a life cycle cost analysis framework are established to derive optimal CBM and TBM strategies with the objective of maximizing lifetime reliability and evaluating their life cycle costs. The advantages of CBM, in comparison to TBM, and the VoI depends strongly on the inspection time. The CBM can achieve higher reliability with fewer maintenance costs than the TBM. An illustrative example is provided using the established probabilistic method and framework to support optimal maintenance planning. This example serves as a basis to explain the benefits of CBM to lifetime fatigue reliability and cost reduction, the conditions when CBM is more beneficial than TBM, the conditions for beneficial, ineffective and unbeneficial repair, and the VoI by inspections.

Bayesian maintenance decision optimisation based on computing the information value from condition inspections

“…Marine and offshore structures are typically exposed to sea and wave environments, which can cause fatigue crack initiation and growth in structural components, especially in the areas with stress concentration. Figure 2 shows a typical fatigue-prone stiffened plate under fatigue loading caused by waves, which are common in marine vessels 3 . Normally, stiffeners and frames improve plate stability, but can lead to d fatigue performance decrease, due to stress concentration, poor welding quality and presence of initial flaws, etc.…”

“…Figure 2 shows a typical fatigue-prone stiffened plate under fatigue loading caused by waves, which are common in marine vessels. 3 Normally, stiffeners and frames improve plate stability, but can lead to d fatigue performance decrease, due to stress concentration, poor welding quality and presence of initial flaws, etc. These are typical trigger factors of crack initiation.…”

“…As a result of development in non-destructive evaluation, sensing and monitoring technologies, it becomes easier to obtain crack condition information. Many researchers thus put efforts in developing CBM strategies that rely on condition information to make maintenance decisions [1][2][3][4] . In marine and offshore engineering, visual inspection and magnetic particle inspection (MPI), represent commonly-adopted means to examine fatigue crack conditions.…”

“…Many researchers thus put efforts in developing CBM strategies that rely on condition information to make maintenance decisions. [1][2][3][4] In marine and offshore engineering, visual inspection and magnetic particle inspection (MPI), represent commonlyadopted means to examine fatigue crack conditions. Following inspection activities, repairs or replacement may be performed to recover structural integrity and increase structural reliability, to avoid failures.…”

On risk-based maintenance: A comprehensive review of three approaches to track the impact of consequence modelling for predicting maintenance actions

“…To overcome this limitation new maintenance policies such as Condition-Based Maintenance (CBM) have been introduced. Thanks to the advancement of technology, especially in sensing and monitoring devices, CBM has indeed gained much attention over the last years [8]. While time-based PM schedules maintenance actions at fixed time-intervals, CBM reacts based on available information regarding the condition of a given component [9].…”