Detecting Blockages and Valve Status in Natural Gas Pipelines

This paper will provide an overview of a novel acoustic reflectometry method that has been developed to detect features, such as blockages and leakages in industrial gas-filled pipelines. The basic concept of the technique is to inject a pulse of sound into a pipeline and then measure the reflections produced as this signal travels along the length of the pipe. Wherever the internal cross sectional area of the pipeline changes then there will be a refection produced. With knowledge of the speed of sound in the gas, the time of flight can be determined and the location of the change in cross sectional area can be identified. The technique is non-invasive and can be used to accurately detect many pipeline features, such as holes, blockages and other objects including valves and even welding joints. The paper will present the results from laboratory tests and field trials which will show the accuracy of the technique in detecting and locating blockages and valve status in industrial pipelines with lengths exceeding 10km and containing high pressure gas. In particular, details of a test where the method was used to identify valve status in a live offshore pipeline, containing high pressure gas will be provided. The difficulties associated with detecting abnormalities in pipelines containing flowing gas will be discussed and suitable signal processing methods will be described which should enable the technique to be applied as a continuous monitoring tool for offshore gas pipelines.