Detection and Localization of Leakages in Toxic/Flammable Chemicals Pipelines Using Distributed Fibre Optic Sensor

Over the past decades, several major industrial accidents led the chemical industries handling large quantities of dangerous substances and national regulation bodies to reinforce the safety and prevention measures of their installations, in compliance with local laws such as the Seveso II directive in Europe. Indeed, leakages of chemicals can be at the origin of toxic releases, which can have severe consequences on the installations as well as on the environment and nearby inhabitants. Industries are prompted to take all possible measures to reduce the occurrence of such catastrophic events by implementing additional technical safety barriers in order to prevent or mitigate any potential danger on their key structures such as pipelines, reactors, storages, transfer lines, etc. Pipeline leakages may have different origins, such as corrosion, fatigue, material flaws, shocks, abnormal temperatures, extreme pressures, or excessive deformations caused by ground movement. In the case of liquefied or pressurized gases, leakages can be detected by the rapid drop of temperature due to the evaporation of the released liquid and its evaporation gases or due to gas expansion. These local thermal anomalies can be reliably detected by a fibre-optic distributed temperature sensing system able to detect temperature changes of the order of 1 degrees C, with 1m spatial resolution and 10 s response time. A fibre optic cable is installed all along the whole length of the pipeline and is connected to a measurement system that can automatically detect temperature anomalies which are tell-tale of leakages and generate an alert to initiate appropriate response actions on the affected pipeline section. Such a system has been permanently deployed at several industrial and chemicals sites were functional and operational tests have also been carried out. This paper will present the system architecture and installation at an ammonia production, storage, shipping and processing site. Results of simulated leakage detection tests and long-term operation in normal conditions will also be presented.