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.

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 six meters 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, on the order of 20cm, 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 seconds per tube. We present several case studies of condenser tube inspection, showing how different faults are identified and reported.

Acoustic Pulse Reflectometry (APR) has recently been gaining acceptance for a variety of tube inspection applications, as a viable alternative to more entrenched technologies such as eddy current. In this paper we present a case study demonstrating how APR can be used successfully for inspecting U-tube bundles. This type of heat exchanger poses a great challenge to technologies which require traversal with a probe, due to the presence of tight bends in the tubes. These are usually not traversable by probes. APR, on the other hand, uses an acoustic pulse as a “virtual probe”, with the ability to navigate bends, elbows, fittings etc. with no difficulty. In this paper we show how the various typical faults are revealed in the acoustic measurements and demonstrate how the analysis software recognizes these faults and generates the report. In one case presented here we inspected 62 heat exchangers used to heat natural gas, containing 39 U-tubes each, totaling 2379 tubes. Each tube had an internal diameter of 11mm, wall thickness of 2.5mm, and a length of approximately 6 meters, though there was some variability in length due to different lengths of the U bends. An added difficulty in inspecting these tubes was that the tube sheet was about 80 centimeters in distance from the inspection port-hole. The average inspection time in the field was 25 seconds per tube. All measurements were logged to computer files, and automated fault detection software generated a full report showing the condition of the tubes, indicating degradations in wall thickness, full and partial blockages, and holes. In the second case study we examine the variability in u-tubes in a single bundle and discuss the effect this has on the results.