On planning of repair of pressurised main pipelines based on the results of in-pipe diagnostics

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On planning of repair of pressurised main pipelines based on the results of in-pipe diagnostics

Milenin, A.S.

The world and national practice of operation of land main pipelines shows the trend to utilisation of different methods to repair them by welding without any interruption of transportation of a product. Planning of a certain repair method, which is an important stage of ensuring the efficiency and safety of restoration of a carrying capacity of defective regions in main pipelines, requires development of appropriate methodological principles for analysis of damage of a structure, estimation of admissibility of operation and prediction of remaining life. This study suggests a multilevel procedure for numeric analysis of results of in-pipe diagnostics of the state of linear parts of main pipelines, allowing for the specific character of repairing them without removal from service, and permitting optimisation of repair-and-renewal operations in lengthy regions of a pipeline on the basis of numeric ranking of defects of a different nature. It is suggested using different levels of ranking depending on the available data of technical diagnostics of the state of a specific linear region of a main pipeline: based on subdivision of all defects into admissibility groups by estimating the remaining safety factor in a region of a specific defect, or by calculating the probability of violation of integrity of a pipeline wall. A differing degree of conservatism of the suggested procedure depending on the completeness of the source data makes it possible to analyse the results of in-pipe diagnostics at the required accuracy and effectively plan removal of the detected defects by the methods of repair of pipelines without withdrawing them from service.