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Acoustic Monitoring Principles
Acoustic monitoring takes advantage of the wire embedded in PCP.
Virtually all corrosion will attack the prestressed wire and when it breaks, the energy can be detected.
Process:
- Prestressing wire breaks or slips generating acoustic energy;
- Energy propagates into water in pipeline;
- Wire-related transient has unique acoustic signature that is detected as it passes the
temporarily installed acoustic sensor;
- Origin is determined by comparing arrival times at each site according to the formula
X1 = (V(T1-T2) + D)/2,
where:
X1 = distance of acoustic event from hydrophone #1
V = velocity of sound in water
T1 = time of arrival of acoustic signal at hydrophone #1
T2 = time of arrival of acoustic signal at hydrophone #2
D = distance between the two hydrophones
The process is illustrated in the following diagram
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