Integrated methodology for determination of preventive maintenance interval of safety barriers on offshore installations

Abstract

Preventive maintenance (PM) is an essential strategy to ensure the integrity of safety barriers and process safety on offshore installations. However, determination of the maintenance interval is challenging. Inadequate maintenance is likely to increase the unreliability of safety barriers and major accident risk, while excessive maintenance may increase personnel exposure and operational risk. In addition, it is highlighted that the reduction of maintenance cost should also be taken into consideration. In this study, a new integrated methodology is proposed to determine the maintenance interval of a specific group of safety barriers, which require periodic testing. Specifically, the study deals with the trade-off between risk increase and reduction associated with maintenance, and optimizes the allocation of maintenance cost. It aims at minimizing the total risk level whilst reducing the maintenance cost. The dynamic data model is established first to predict the state and trend of risk level for the safety barriers. Then, the classification model is established to classify the risk level and optimize the allocation of maintenance cost. Finally, the maintenance decision model is established to balance the maintenance-related risks. The proposed methodology is tested by a case study which is to determine the recertification interval of PSVs on a specific offshore installation on the Norwegian Continental Shelf (NCS). It is demonstrated that the proposed methodology is effective in determining the PM interval. The methodology is also useful in minimizing the total risk level of the safety barriers and reducing the maintenance cost per unit time.