Pipelines are the most economic transport systems for mineral oils, gases and other chemicals such as ammonia, ethylene and carbon dioxide. As a means of long-distance transport, pipelines have to meet high demands of safety, reliability and efficiency.

The management of pipelines therefore presents unique challenges. Their long length, high value, high risk and often difficult access conditions require continuous monitoring and an optimisation of the maintenance interventions.

Flowlines: dangers and maintenance

Pipelines or gas lines often cross hazardous environmental areas, both in terms of exposure to natural disasters such as landslides and earthquakes, and third-party influences such as vandalism or obstruction. These hazards can significantly change the original structural functioning of the flowline, leading to damage, leakage and failure, as well as serious economic and ecological consequences.

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The main concern for pipeline owners comes from possible leakages, which can have a severe impact on the environment and put the pipeline out of service. Leakages can have different causes, including excessive deformations caused by earthquakes, landslides or collisions with ship anchors, wear, material flaws or even intentional damage.

Failures usually begin with leaks at poor joints, corrosion, and small structural material cracks, and can gradually progress to a catastrophic result. Leakages can be detected and localised using distributed fibre optic temperature sensors.

Fluid pipelines generate a hot spot at the location of the leak, while gas pipelines generate a cold spot due to the gas pressure relaxation. These localised thermal anomalies can be detected by a distributed measurement with good spatial, time and temperature resolution such as the DiTeSt system.

It is often possible to detect damage before a critical state is reached. Fibre-optic systems are ideally suited for this task. By measuring distributed strain, it is possible to determine the increased stress caused by external actions such as landslides and earthquakes, or internal causes such as a reduction of cross-section due to corrosion and wear. Finally, distributed temperature and strain monitoring can detect third-party intrusion before any damage is done to the pipeline.

Pipeline integrity monitoring systems are beneficial because they can enhance productivity and system reliability, and are therefore an important aspect of pipeline technology, operation and safety.