Major accident hazard pipeline failure frequency calculation using fracture mechanics

Abstract

The Health and Safety Executive (HSE) use the PIPINV3 (PIPeline INtegrity) model to predict failure frequencies for major accident hazard (MAH) pipelines. The failure frequencies generated by PIPINV3 are used as part of a pipeline risk assessment process to create land use planning (LUP) zones around the pipeline. HSE uses the LUP zones to provide guidance to local planning authorities in Great Britain on proposed developments near a pipeline, for when there are potential modifications to an existing pipeline, and for proposed new pipelines. PIPIN was first developed in the 1990s. It has been rewritten to: incorporate a Monte Carlo solution method; update the scientific basis of the model, and update the historical data used in the model. This paper details the science within PIPINV3 and also describes how predicted failures are apportioned amongst representative hole sizes used by HSE to model different severities of failure. Comparison tests with an earlier version of the model have been made using test data from 584 natural gas pipelines, a subset of pipelines from the UK natural gas network. The tests indicated that the use of PIPINV3 reduced predicted failure frequencies on average. This leads to either no change or a reduction in the size of the calculated LUP zones in most cases.