A key driver in the risk assessment of an offshore installation or process plant is the leak frequency as this is combined with the consequence information to determine the process safety risks.Frequencies are normally determined by processing historic information on incidents.The UK's Hydrocarbon Release Database(HCRD)captures the details of almost 5000 leaks for UK North Sea offshore installations from 1992 to the present day.It is the most commonly used source of leak frequency data both in the UK and the US.It is also applied as many other parts of the world as well as being used for onshore process plants and refineries.Revised correlations for leak frequency and hole size distribution have been developed by DNV GL on behalf of the International Association of Oil and Gas Producers(IOGP).This analysis indicates a significant reduction in leak frequency which has implications for risk-based design and operational decision making.Alternative correlations produced by organizations in the Norwegian offshore industry show a similar significant reduction.With such a high reliance on the use of the HCRD as a source,it is important that the reporting,recording,collation and interpretation of the data is thorough and technically sound.There are initiatives in place or planned to further improve the data collection and thereby the accuracy of the estimates produced.This paper discusses how the IOGP leak frequency correlations were derived from the HCRD and the measures taken to ensure robustness of the conclusions.It also explores the impact of using the updated frequency correlations in quantitative risk assessments and future work investigating the technical quality of the HCRD.
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