Q2. What is the AE sensor's attenuation coefficient?
As the attenuation coefficient decreases with frequency, lower frequency AE sensors can be selected for polymer based pipelines in order to monitor leakage with reasonable sensor spacing.
Q3. What is the effect of the cross correlation approach on the detection of leaks?
As leak source generates continuous acoustic emissions which can be highly chaotic, cross correlation approach should be integrated with the hit sequence identification based on the ASL distributions of the AE sensors in order to reduce the error of the arrival time differences of the AE sensors.
Q4. What is the importance of secondary information in the AE method?
Secondary information is needed for the reliable use of cross correlation approach, and preventing potential errors in the arrival time difference determination of continuous AE sources.
Q5. What is the phase velocity of time harmonic waves?
The phase velocity c for time harmonic waves is a complex number as a function of wavenumber k as given by the equation [17]:)()( 21 kickcc += (6)The first term indicates dispersive viscoelastic waves; the second term with imaginary part indicates the amplitude loss with the increase of wave number.
Q6. Why do AE sensors detect leaks with lower amplitude?
Due to the attenuation, the AE sensors away from the leak source detect the source with lower amplitude as compared to the AE sensor closest to the sensor (i.e. the first hit sensor).
Q7. What is the AE sensor response to the leak source?
The AE sensor responses to the leak source can be chaotic, which may cause uncertainty and high probability of error in source location.
Q8. What is the main reason why the pipeline inspection and maintenance is not prioritized?
Caleyo et al. [4] demonstrated that prioritizing the pipeline inspection and maintenance based on the failure data might establish incorrect prioritization due to significant uncertainty of pooling failure of dissimilar pipeline systems data.
Q9. What is the definition of the Acoustic Emission method?
The Acoustic Emission method is a nondestructive testing method that relies on propagating transient waves generated by sudden stress-strain change in a material such as crack growth, leak, impact.
Q10. What is the main advantage of the AE method?
The ability of the AE method to locate time dependent (e.g. crack growth) or instantaneous sources (e.g. impact) with the sensors further from the flaws is a major advantage as compared to other NDE methods.
Q11. What is the effect of the attenuation and the wave velocity study with distance on leak?
The attenuation and the wave velocity study with distance can be integrated with the location model for any kinds of pipeline materials in order to increase the reliable leakage location.
Q12. What is the AE source energy due to the target leak rate?
AE source energy due to the target leak rate should be identified in correlation with the attenuation characteristics of material in order to validate the claim that the AE source can propagate along the pipes above the background noise so that two nearest sensors can detect the source.
Q13. What is the attenuation coefficient of the PVC pipe?
The attenuation coefficient obtained on the 2.54 cm PVC pipe using 60 kHz sensor indicates that 60 kHz is not an appropriate frequency for detecting leakage in long PVC pipeline networks.
Q14. What is the definition of the continuous AE signal?
As compared to the burst type AE signal, the continuous AE signal does not have a definite rise time, and can be idealized as the summation of multiple wave arrivals using Heaviside functions.
Q15. What is the second assumption of the source localization algorithm?
The second assumption causes significant error if the conventional source localization algorithm is applied to structures that are spread in two dimensions while they could be idealized as one dimensional due to the length to cross section ratio.
Q16. What is the standard deviation of the AE sensor?
The standard deviation indicates the expected error in source localization due to the variance in the wave velocity caused by dispersion.