Measuring and testing – Vibration – By mechanical waves
Patent
1998-01-15
1999-10-12
Chapman, John E.
Measuring and testing
Vibration
By mechanical waves
G01N 2918
Patent
active
059658185
ABSTRACT:
This invention is a new inspection technique using ultrasonic Lamb waves to measure reduction of pipe wall thickness due to localized corrosion at pipe supports. The technique uses two transducers in a pitch-catch mode to send and receive a selected Lamb wave. The wave travels along the pipe wall in the circumferential direction. The reduction of the pipe wall thickness at the pipe support changes the time-of-flight between the two transducers. By comparing time-of-flight data measured from the pipe support area and from areas adjacent to the pipe support, one can quantify the change of time-of-flight due to the pipe corrosion wall loss at the support. A mathematical model, a sizing algorithm and a PC program have been developed to quantitatively relate in time-of-flight to the minimum remaining wall thickness. With them, one can quantify the minimum remaining pipe wall thickness at a pipe support by simply measuring the change in the time-of-flight.
REFERENCES:
patent: 4307616 (1981-12-01), Vasile
patent: 5438872 (1995-08-01), Kobayashi et al.
patent: 5619423 (1997-04-01), Scrantz
Chapman John E.
Shell Oil Company
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