Risk Based Inspection (RBI) of Above-Ground Atmospheric Storage Tanks is a process for determining the optimal run length of a tank before a costly and time-consuming internal inspection is required. There are various methods for calculating appropriate inspection intervals which rely on risk models. The risk calculations are generally based on the tank’s design, operation, and corrosion/inspection history.

However, outside of API RP 581, there is little published material giving guidance on actual, quantitative models that can be used effectively to calculate risk. Probability and consequences of failure for tanks require a very different and widely varying set of calculations than pressure vessels and piping, and there are a number of decisions that must be made in the calculation which may have a significant impact on the results.

The purpose of this paper is to overview some of the nuances associated with the calculations used to perform tank RBI. It also explains the effect of each variable on the tank's risk by performing a sensitivity analysis.

Subject
Water, Materials, Risk based inspection, Cathodic protection, Corrosion rate, Inspection, Probability, Mechanical failure, Corrosion modeling, Corrosion data, Tank bottoms, Corrosion monitoring, Soil
Keywords:
Risk Based Inspections, Tank RBI, Sensitivity Analysis, Tank Safeguards, Probability of Failure, Consequence of Failure
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2013
Association for Materials Protection and Performance (AMPP)
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