A quantitative risk-based approach for assessing optimal inspection intervals of a caustic soda recovery plant: a case study

Arena S.

;Perna R.;Pilloni M. T.

2022-01-01

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Abstract

Inspection and maintenance activities are necessary to ensure mechanical integrity and the efficient and safe operation of systems and equipment. The management of critical assets is crucial, and it should take into consideration the inspection and testing of the equipment using proper approaches and procedures. The Risk Based Inspection (RBI), proposed by the American Petroleum Institute (API), is currently the major practical standard for the management and scheduling of in-service/on-site inspection activities in the chemical industry. In this paper, the risk-based inspection (RBI) technique, based on API 581 standard, is introduced for determining optimal inspection intervals of a caustic soda recovery plant. Using inspection data based on active major damage such as corrosion and thinning both the probability and consequence of accident have been investigated as well as the annual cost of the inspection program. The novelties lie in performing this analysis on a caustic soda recovery plant due to limited literature on this specific application and the inclusion in the proposed approach of several damage mechanisms aiming at providing a more accurate analysis. Therewith, the corresponding scenarios and outcomes of potential failures are determined, and accordingly, appropriate inspection dates and maintenance routines are proposed by considering the assumption that risk remains acceptable between two planned intervals. This paper summarizes that, as a fundamental step in the risk analysis, the RBI can be considered as suitable maintenance guidance for assessing critical equipment affected by multiple damage mechanisms providing an effective approach for inspection programs that increases plant availability and reduces unplanned shutdowns.