Applying structural reliability methods to ageing pipelines

摘要

The use of Structural Reliability Analysis (SRA) to justify continued safe operation of pipelines is increasing. Indeed, the technique has recently been used by BG to demonstrate that 900 km of high pressure pipelines in the UK Transco National Transmission System could operate safely at a stress level of 78% SMYS, which is above the code requirements. The overall aim of the structural reliability based method is to assess the fitness for purpose of a pipeline based on a calculated failure probability. It takes account of natural variations in pipeline dimensions and material properties and directly addresses the mechanisms that lead to failure. This paper presents the basic principles of SRA and gives a detailed description of each of the key elements of the approach including relevant mathematical formulations where appropriate. Particular focus is given to the application of the approach to ageing pipelines and some detailed guidance is given on the use of the technique to extend pipeline life. To this end the definition of pipeline life is given detailed consideration. Guidance is given on how the technique may be used to extend life by removing inherent conservatism, introducing and quantifying the effects of failure mitigating activities, or a combination of these.