An Approach to Grid-based Fire Frequency Analysis for Design AccidentalLoads in Offshore Installations

摘要

This paper describes the approach for establishing the Design Accidental Load (DAL) fire based on a grid-based fire risk analysis. Representative cases are screened via an initial fire risk analysis where the leak frequencies, ignition probabilities and inventories are combined to determine the cases with the highest risk. The fire risk analysis is subsequently performed based on the consequence results and the fire frequencies. Although many initiates for risk assessment were taken, there are many limitation and uncertainties on frequency analysis. Especially, calculation of ignition probability for an accidental hydrocarbon release on an offshore platform is a complex issue. To overcome these limitations of historical accident data, time dependent ignition model is developed a model for probability of ignition of hydrocarbon gas leakages on offshore platforms on based of ignition model presented by some JIPs for offshore risk assessment and improved understanding of ignition mechanisms. In this paper, we reviewed the existing probabilistic risk assessment method, such as ignition models, fire and explosion models, and selected the ones most suitable for offshore conditions. Then applied grid-based fire frequency analysis in the risk assessment. Two main revisions were incorporated: a grid-based approach was adopted to enable better consequence/impact modelling and analysis of radiation, and an enhanced onsite ignition model was integrated in the consequence assessment process to obtain better results. This study will be useful for the fire frequency analysis on offshore platform topsides as one of procedures of quantitative risk assessment.