Girth welds of hydro-carbon transporting pipelines play important role of the life and the lifetime, during both the construction and the operation. In consideration of the huge number of girth welds, the highlighted attention to those is worthy and necessary. The aims of the article are twofold: on the one hand, collecting the influencing factors on the failures of girth welds; on the other hand, answering the question assumed in the title of the article: how to prevent damages of transporting pipeline girth welds? The answers build upon the demonstrated influencing factors, using examples, and systematically respond to those.

Hydrocarbon transport pipelines' safe operation is an economic and environmental interest. These pipelines are typically designed for static loads, but during their long-time operation - due to pressure changes and environmental impacts - they are also subject to cyclical loads. The individual pipe sections are connected by girth welds, which represent potential sources of hazards in terms of damage. In order to assess the reliability of girth welds, full-scale tests are carried out under simple and complex loads. The purpose of this article is twofold. On the one hand, summarize the full-scale tests on transmission pipelines, with special attention to the tests on girth welds; on the other hand, based on this, draw conclusions for the design and implementation of our own full-scale tests.

The critical elements of high-pressure hydrocarbon transporting pipelines are often the girth welds, which are subjected to complex loads. The aims of our research and this paper are to introduce our full-scale pipeline fatigue and burst tests applying cyclic internal pressure and superimposed external bending stress on girth welds, furthermore, attracting the importance and the applicability of the investigation results. A unique testing system was built to study the behaviour of pipeline girth welds under simultaneous loads. The tests were evaluated using video camera recordings, internal pressure vs. burst time functions and failure pressure values.

A hidrogén okozta repedés, illetve a hidegrepedés egy gyakran előforduló károsodási mechanizmus, ami a fémek és az ötvözetek többségére hatással van. A hidegrepedést számos külső és belső paraméter befolyásolja, így a repedéskialakuláshoz hozzájáruló tényezők meghatározása gyakran nehézségbe ütközik. Jelen áttekintő cikkben, hazai és nemzetközi szakirodalmi források alapján, a hidrogén előfordulását, oldhatóságát, diffúzióját és mennyiségi maghatározásának a lehetőségeit vizsgáljuk, valamint a hidegrepedés mechanizmusát és kialakulásának lehetséges megakadályozási módjait foglaljuk össze.

The main objective of our ongoing research is data collection for integrity management (IM) tasks, in other words for pipeline integrity management system (PIMS), helping the transporting pipeline operators in different decision situations. Either the reserves of the girth welds after a long-term operation can be identified or the girth welds with different defects should be repaired and/or replaced. From the operators’ point of view, the long-term operation is the cost-effective way; however, from the safety point of view, the managing of the lifecycle of the pipeline is the more reliable way. Unfortunately, inadequate girth welds cause catastrophic damages in transporting pipelines, all over the world. Consequently, the optimal operation of the pipelines is a complex task. The paper introduces our investigation program executed on full-scale pipeline sections. Fatigue (100,000 cycles) and burst tests were executed on different pipeline sections containing girth welds. Long-term operated and replaced gas transporting pipeline sections, furthermore, both appropriate and inadequate girth welds were investigated. The testing results and the damage histories were compared with each other; safety factor (SF) was defined and calculated for the assessment of the reliability of the girth welds.