A Public Leak Frequency Dataset for Upstream and Downstream Quantitative Risk Assessment

A recent CSChE conference in Montreal identified frequency estimates as the area of greatest uncertainty in current Quantitative Risk Assessment studies.  There are a few sources of onshore data – Netherlands and Belgium have both issued two different datasets for use in Seveso Directive risk assessments.  Some companies and consultants have their own data – but the provenance of these is often uncertain and examples exist of frequencies that are too low, not matching historical accident frequencies.  It is detrimental to QRA methodology that such old or inconsistent data is routinely used.

The UK HSE has maintained a leak event dataset for offshore facilities since the early 1990’s.  This contains around 4000 leak events reported by facilities and supported by detailed documentation completed by the company.  This is considered the most extensive dataset of its type and superior to current published datasets which often have much smaller and older data, not reflecting current integrity management programs.  DNV for several years has assessed this data on behalf of a major operator and screened out leaks not appropriate for QRA’s (e.g. equipment isolated and under maintenance).  While the data is noisy, typical for real data, a smoothing function is applied to cover leak sizes in the range 1-100mm (there is insufficient data for full bore ruptures).  Leaks are differentiated for 17 equipment types.

DNV has decided to make this data publicly available, at no charge, so that all those carrying out QRA studies can use this most up-to-date data, from a large data set.  While the data is from upstream, advice is also presented on how this may be applied to downstream and midstream facilities (e.g. refineries and LNG facilities).