In order to monitor pipelines using Distributed Acoustic Sensing (DAS), placing the fiber optic cable inside the pipe offers several advantages compared to external fibers: existing pipelines can be retrofitted without new trenching, and leak sounds can be detected more efficiently without concerns about the relative positioning between the fiber and the leak. A new pipeline monitoring system, DALI (Distributed Acoustics for Leakage and Intrusions), was developed with a specific focus on placing the fiber optic cable inside the pipeline, making it highly suited for retrofitting utility, steam, oil and gas pipelines.

In this paper, we present a case study in which the DALI system was installed in an operational 1000 mm-diameter water pipeline over 6 km. The leak detection capability was confirmed in several blind tests performed by the pipeline operator. We will discuss installation aspects of the fiber, acoustic sensitivity, and how to handle the specific challenges posed by the large data volumes generated by the DAS sensor.

From a cost-benefit standpoint, installing a DALI monitoring system not only facilitates pipeline maintenance and reduces risk of product loss and external damages, but it also enables asset owners to extend the lifetime of ageing pipelines without compromising on reliability, allowing for strong reductions in the both capex and opex costs of the network.