A ROBUST APPROACH TO PIPELINE INTEGRITY MANAGEMENT USING DIRECT ASSESSMENT BASED ON STRUCTURAL RELIABILITY ANALYSIS

摘要

The management of the threat to integrity of corrosion damage has traditionally been achieved using in-line inspection (ILI) and the hydrostatic test. However, these approaches are not always practicable and therefore alternatives are sometimes necessary. For external corrosion, valuable information can be obtained using surface measurement techniques such as Close Interval Survey (CIS), Direct Current Voltage Gradient (DCVG) and other so-called Direct Assessment (DA) techniques. For internal corrosion, multiphase flow modeling can be used to determine the likely sites of water 'hold-up' and hence internal corrosion. However, both above ground measurement techniques and predictive modeling are subject to uncertainty and therefore do not always locate the presence of corrosion. Moreover, it is possible that the presence of corrosion may be identified erroneously. In order to account for this, a new technique, based on Structural Reliability Analysis, has been developed for robustly interpreting the impact of results from above ground surveys and predictive modeling on the structural reliability levels. This paper describes the development and application of these techniques for the purpose of integrity management. Case studies involving both external and internal corrosion are presented which, clearly demonstrate the application, and emphasize the value of the technique as a basis for integrity management.