An algorithm for analyzing wave reflections and time-of-flight ultrasonic pulse-echo data has been developed for monitoring the health of steam pipes to determine the height of condensed water through the wall in real time, at temperatures up to 250 °C.

Illustration of the condensed water height monitoring using time-of-flight measurements of reflected ultrasonic waves.
When the water height is low or there is disturbance in the environment, the predicted water height may not be accurate. In the developed computer code, various signal processing techniques including the auto-correlation, Hilbert transform (HT), and the Shannon Energy Envelope methods were implemented to determine the water height in the steam pipe. The results have shown that the developed method provides a good capability for monitoring the height in the regular conditions. An alternative solution for shallow water or no water conditions based on a hybrid method based on HT with a high pass filter and using the optimized windowing technique was used to refine the algorithm.

The disclosed algorithm and computer code provide an effective method of analyzing time-of-flight ultrasonic pulse-echo data in nondestructive evaluation (NDE) and health monitoring applications. Such an algorithm is needed to support the determination of the quality and integrity of structures. This includes the ability to detect minute flaws that are critical to secure the operation of NASA structures in service.

There is no existing software that monitors the height of condensed water in steam pipes that are as hot as 250 °C. The data is noisy and complex, and the developed software has been shown to provide accurate determination of the height in real time.

This work was done by Shyh-Shiuh Lih, Yoseph Bar-Cohen, Xiaoqi Bao, and Hyeong Jae Lee of Caltech for NASA’s Jet Propulsion Laboratory.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Innovative Technology Assets Management
JPL
Mail Stop 321-123
4800 Oak Grove Drive
Pasadena, CA 91109-8099
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Refer to NPO-49048