Acoustek® is a
patented technique that has been developed at the
For further information on how Acoustek® was used to survey an offshore gas pipeline and correctly identify and locate a near complete blockage approximately 500m from the host platform see UMIP News.
The basis for the Acoustek® system is the observation that the propagation of acoustic waves in a fluid medium is very sensitive to any discontinuity in the properties of the fluid. To illustrate this, figure 1 shows an expansion in the diameter of a pipeline containing a stagnant fluid. If an acoustic wave is injected from the left into the pipe then it will be partially reflected at the interface, producing reflected and transmitted acoustic components. For weak plane waves of the type considered here, the waves propagate at the local speed of sound, which will vary depending upon the local conditions of the fluid. Reflective waves will occur wherever there is a change in the cross-sectional area of the pipe. In industrial pipeline systems this will occur wherever there is a valve, ‘T’ piece or blockage, for example. Further to this any leakage within a pipe will act like a change in the cross-sectional area and hence a fraction of the incident acoustic energy would be reflected.
Figure 1: Acoustic transmission at pipe joint
Results from Trials
system has been trialed on long lengths of pipelines in
Figure 2: Pipeline layout
The Acoustek® system was able to identify a series of features in the pipeline, which were believed to be deposits of water of varying size. Figure 3 shows the reflections produced by the pipeline and figure 4 shows the locations of features that were identified in the pipeline.
The large peak in figure 3 indicates a full blockage of the pipeline, while the smaller peaks indicate partial blockages. Careful analysis of the reflected signals showed that secondary and tertiary reflections were detectable, suggesting a range of approximately 10 km of this technique.
In a recent trial on an offshore installation, Acoustek® was able to survey a section of gas pipeline and correctly identify and locate a near complete blockage approximately 500m from the host platform (for further details of this see: UMIP News).