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Title: Lateral buckling of submarine pipelines
Category: Papers by Dr Andrew Palmer
Downloadable: Yes 
Project No.:
Research Agency:
Catalog No.: AP120
Date of Publication: 1997
Price: $25.00 US
Authors: A C Palmer, C R Calladine, D Miles and D Kaye
Abstract: The longitudinal compressive force induced in pipelines by operating temperature and pressure often causes upheaval buckling in buried pipelines both onshore and offshore. Upheaval is recognised as a serious problem, and has received much research attention, though it would be wrong to suggest that the practical problem is yet entirely conquered. The problem is made more severe because operating temperatures beyond 150°C are no longer unusual.

The same driving force can also cause the pipeline to buckle sideways. A pipeline that lies on the natural seabed or in an open trench can generally move sideways against a smaller resistance than if it were to move upwards. Lateral buckling is probably more common than upheaval buckling, and often goes unnoticed. It may not be harmful to the continued safe operation of a pipeline, and may indeed be beneficial, because its effect is to relieve the longitudinal compressive force at the buckle and over some distance to either side of the buckle, so that a significant length of the line is protected against more damaging upheaval.

Such movements no doubt occur in many unburied pipelines, and have often been overlooked or ignored. The development of pigs with highly-sensitive inertial navigation systems has for the first time made it possible to detect and measure movements of this kind. It becomes entirely practicable to identify the locations automatically by a pattern-recognition system, and to evaluate and report on each bow without any human intervention.

It seems likely that lateral movements at regular intervals are generally beneficial, or at worst harmless. However, a less reassuring possibility is that the movement might localise and concentrate into a smaller number of very large buckles, in which the level of strain might be so far into the plastic range that the pipe might buckle locally, or might rupture because the ductility of a girth weld had been exhausted. Another possibility is that the most severely strained region of such a pipeline might move backwards and forwards during temperature and pressure cycles, and that low-cycle fatigue might occur.

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