Effect of correlated input parameters on the failure probability of pipelines with corrosion defects by using FITNET FFS procedure

International Journal of Pressure Vessels and Piping, Volumes 105–106, May–June 2013, Pages 19–27
Effect of correlated input parameters on the failure probability of pipelines with corrosion defects by using FITNET FFS procedure
Guian Qian (a), Markus Niffenegger (a), Wenxing Zhou (b), Shuxin Li (c)
a Paul Scherrer Institute, Nuclear Energy and Safety Department, Laboratory for Nuclear Materials, OHSA/06, 5232 Villigen PSI, Switzerland
b Department of Civil and Environmental Engineering, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B9, Canada
c School of PetroChemical Engineering, Lanzhou University of Technology, Lanzhou 730050, China
Abstract
Offers a probabilistic methodology considering the correlations between the input variables for the failure probability evaluation of corroding pipelines based on the corrosion module of the FITNET FFS procedure. Authors built a computer program based on FITNET FFS to calculate the failure probability of pipelines by considering different numbers of defects and various elapsed times.
In the case of a single defect, the correlation between the initial defect depth and the initial defect length has the most significant impact on the failure probability of the pipeline. If the correlations between these two parameters for an individual defect are not considered, the prediction results are nonconservative when the failure probability is below 40% and conservative when it is above 40%.
In the multiple defect case, the independent assumption of variables typically leads to a conservative estimate of the failure probability. The conservatism of the estimate increases as the elapsed time and/or the actual correlation coefficients of the variables increase. The correlation of the operating pressure, the initial defect depth and material ultimate tensile strength at the location of different defects has a larger impact on the failure probability than the correlation of other parameters at different defects.
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