(1) Comparing the results of INDT (in-tube nondestructive testing), which was periodically performed on the same gas pipeline section for a number of years, the authors established that a sharp increase occurred in the formation rate of new SCC (stress corrosion cracking) flaws along with some stability in the development of corrosion processes. (2) The results of monitoring the state of cracks with attachable magnetic anisotropy transducers demonstrated a sharp change in the stressed state as the growth of transducer signals due to the overloading of the wall of a pipe and the additional opening of crack edges at all the monitoring points on the inspected and repaired gas pipeline sections in the spring-summer period. The overloads were caused by winter repair measures, such as the pitting, thawing, and compaction of soil in the spring-summer period. (3) A sharp increase in the SCC flaw formation rate on a repaired section was caused by the repair measures that were performed in the winter with the subsequent thawing and compaction of soil and resulting overloads, which stimulate the development of SCC. Processes that additionally stimulate the development of SCC and induce an increase in the formation rate of new flaws due to overloads that are produced by problems that occur during the laying of pipes during the winter repair measures for the removal of flaws were shown to occur on gas pipeline sections during the analysis of INDT data. New flaws are diagnosed during regular INDT and are liable to subsequent repair and removal, during which overloads can be renewed. Hence, this results in an endless circle of causes and effects, where the repair in order to remove flaws creates the conditions for the formation of new flaws. It seems likely that repair works on the linear part of a main gas pipeline can reasonably be accompanied by stability control of the stressed state of pipes on repaired sections, both in the real-time regime (after the works are performed) and via prolonged monitoring with installed attachable transducers.
Peculiarities of the development of stress-corrosion cracking on a pipeline section from the results of repeated in-tube nondestructive testing
Russian Journal of Nondestructive Testing ; 48 , 7 ; 411-417
2012
7 Seiten, 6 Bilder, 2 Tabellen, 2 Quellen
Article (Journal)
English
zerstörungsfreie Prüfung , Spannungsrisskorrosion , Spannungsrissausbildung , Gasfernleitung , Teilstück , Russland , magnetischer Sensor , magnetische Anisotropie , Bildungsmechanismus , Bildungsgeschwindigkeit , Spannungszustand , vorbeugende Instandhaltung , Inspektionsintervall , Inspektionszyklus , Datenanalyse , Risslänge , Rissbreite , Pipeline-Wartung
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