The Health and Safety Executive (HSE) uses the PIPIN (PIPeline INtegrity) model to determine failure frequencies of major hazard pipelines. PIPIN contains two approaches to determine failure rates: an approach based on operational experience data, which generates failure frequencies for four principle failure modes (mechanical failures, ground movement and other events, corrosion, and third party activity); and a predictive model that uses structural reliability techniques to predict the failure frequency due to third party activity (TPA) only. The predictive model uses historical data in the form of damage data distributions and strike rates as inputs to the fracture mechanics equations. HSL used statistical techniques to determine the damage data distributions that provide the best fit to UKOPA (UK Onshore Pipeline Operators’ Association) data. The strike rates were also updated using the same dataset. The effect of the revised data on a set of 584 pipelines has been investigated and it has been shown that the failure rates are reduced in the majority of cases. Further tests have been performed using a revised form of PIPIN with modified science and updated historical operational experience data. It was found that the failure rates are reduced, on average, when compared to the previous version of PIPIN.
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