Прогнозирование долговечности магистральных газопроводов, подверженных коррозионному растрескиванию под напряжением

Abstract

Background At the present time the issue of service life prediction of main gas pipelines under the stress corrosion cracking (SCC) is very important. The existing normative basis is able to make out only the individual tasks of the probabilistic evaluation of the gas pipeline service life, despite the fact of widespread use of expert techniques that are mainly based on the deterministic models of exhaustion. In the case of gradual failures caused by development of stress corrosion, assessment of reliability indexes is based on the theory of runs of random processes out of the available limits by Poisson distribution, whereas the statistical number of failures caused by SCC is often described by a normal one. In this article, on the basis of the analysis of main gas pipelines failures caused by SCC, the applicability of the known methods for cracking prediction is considered and a new method is offered, which significantly increases the accuracy of determination of the time to failure. Aims and Objectives Building a model of development of main gas pipelines SCC, taking into account the operational factors. Results It was shown that the service life prediction can be performed by introduction of effective crack growth rate, normalized to the temperature, the stress-state and the sensitivity to SCC. Use of the SCC rate index, the stress state of the pipeline wall, thickness, temperature, sensitivity of steel to cracking improves the accuracy of service life prediction of main oil and gas pipelines under stress corrosion.