Determination of design accidental fire load for offshore installations based on quantitative risk assessment with treatment of parametric uncertainty

- This study investigated parametric uncertainty for determining DAL fire based on the QRA for offshore installations.
- There are two types of critical and uncertain parameters, which are the initial leak size and statistical data.
- LHS technique was used to extract representative values from defined probability distributions of uncertain parameters.
- The proposed method provided quantitative information on inherent uncertainty, which can lead to better decision making.

This study investigated the critical issues for determining the design accidental load (DAL) fire procedure based on quantitative risk assessment (QRA) for offshore installations. Considerable attention was paid to parametric uncertainty in choosing the numerical values used for the frequency and consequence analysis. In particular, selecting the initial leak size was one of the most critical aspects, and inconsistent approaches for selecting this value resulted in different risks for identical systems. Frequency analysis of past investigations also overlooked the inaccuracy and unsuitability of statistical data. Accordingly, the estimated risks were significantly uncertain, and the lack of information about the results increased the risk of making the wrong decision. In this study, the Latin hypercube sampling (LHS) technique was used to treat parametric uncertainty in QRA. Different fire exceedance curves and DAL fires were demonstrated by selecting different sets of representative values. The distribution and confidence interval of the DAL fires showed a wide distribution with varying uncertain and critical parameters. Therefore, this procedure provided quantitative information on inherent uncertainty, and such additional information regarding DAL fires can lead to better decision making.