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Technical Briefs

Condenser Tube Examination Using Acoustic Pulse Reflectometry

[+] Author and Article Information
N. Amir, O. Barzelay, A. Yefet, T. Pechter

 AcousticEye Ltd., 4 Harechev, Tel Aviv, 67771, Israel

J. Eng. Gas Turbines Power 132(1), 014501 (Oct 01, 2009) (5 pages) doi:10.1115/1.3125302 History: Received August 13, 2008; Revised August 24, 2008; Published October 01, 2009

Acoustic pulse reflectometry (APR) has been applied extensively to tubular systems in research laboratories for purposes of measuring input impedance, bore reconstruction, and fault detection. Industrial applications have been mentioned in the literature, though they have not been widely implemented. Academic APR systems are extremely bulky, often employing source tubes of 6 m in length, which limits their industrial use severely. Furthermore, leak detection methods described in the literature are based on indirect methods, by carrying out bore reconstruction and finding discrepancies between the expected and reconstructed bore. In this paper we describe an APR system designed specifically for detecting faults commonly found in industrial tube systems: leaks, increases in internal diameter caused by wall thinning, and constrictions. The system employs extremely short source tubes, in the order of 20 cm, making it extremely portable, but creating a large degree of overlap between forward and backward propagating waves in the system. A series of algorithmic innovations enable the system to perform the wave separation mathematically, and then identify the above faults automatically with a measurement time on the order of 10 s per tube. We present several case studies of condenser tube inspection, showing how different faults are identified and reported.

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Figures

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Figure 1

Schematic examples of reflections from discontinuities

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Figure 2

(a) A segment of a measurement showing a reflection from a hole in the tube wall, versus a reference measurement of tube without a hole. (b) A segment of a measurement showing a reflection from scoring of the tube wall, versus a reference measurement. Scoring creates a local enlargement of cross section, therefore the reflection is a negative pulse followed by a positive one.

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Figure 3

A segment of a measurement showing a reflection from a constriction created by a washer in the tube, versus a reference measurement. The constriction is a local decrease in cross section, therefore the reflection is a positive pulse followed by a negative one.

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Figure 4

A segment of a measurement taken from the reading condenser

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Figure 5

A segment of a measurement showing two local blockages, indicated by a constriction (positive spike) followed by a dilation indicating return to nominal cross section (negative spike)

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Figure 6

A measurement showing local increase in cross section—a dilation—followed by return to nominal cross section

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Figure 7

A measurement showing increase in cross section down to the end of the pipe—a dilation not followed by a return to nominal cross section

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