PROBABILISTIC ASSESSMENT OF PIPELINE RESISTANCE TO THIRD PARTY DAMAGE: USE OF SURVEYS TO GENERATE NECESSARY INPUT DATA

摘要

A complete risk assessment procedure for pipelines relies, among other things, on the evaluation of failure probabilities. Incident reviews in western countries have identified third party damage as the main cause of failures with leaks. While some approaches already exist in order to evaluate the failure probability of transmission pipelines subject to third party damage, the issue of feeding the models with appropriate statistical data is a key factor for the success of the evaluation. We present here briefly the outline of the tool developed by Gaz de France R&D Division to evaluate failure probabilities in the event of third party damage. Then we discuss the issue of available data, and particularly the most critical one, i.e. the population of ground working machinery, a majority of which are excavators. In order to assess as well as possible the exposure of pipelines to the threat of interference with excavators, we conducted a large scale survey in rural, semi-urban and urban areas in Western Europe in order to determine important parameter distributions of the excavators population: mass, digging depth, tool types and dimensions, soil type, type of ground works, etc. Random variables are used to describe these parameters and their influence on the failure probability is illustrated in a series of illustrative case studies. The importance of access to reliable information about the loads to which a pipeline is exposed is clearly shown in this paper, particularly due to the fact that the dispersion is a lot larger for the parameters linked with third parties working around the pipeline than for parameters of the pipeline: geometry and material properties.