APRAcoustic Pulse Reflectometry is an acoustic technique for the inspection of tubes. An acoustic pulse is transmitted from the end of the tube into the medium that fills the tube. This is generally air but can also be water. The pulse will travel along a uniform tube until it reaches the end where a single reflection will be created. Any deviations from uniformity, such as changes in the bore diameter due to erosion or corrosion, any blockages and any holes in the tube wall, will generate reflections, which can be detected and analysed. APR is used for the inspection of heat exchanger tubes.

The APR technique has also found application in seismic work, in medicine for the non-invasive inspection of the ear, nose and throat airways and in the investigation of musical instruments.

For more information on APR, see:
‘The evolution of acoustic inspection based on acoustic pulse reflectometry’. Available at: www.qualitymag.com/articles/90186-the-evolution-of-acoustic-inspection-based-on-acoustic-pulse-reflectometry
‘Talcyon uses acoustic pulse reflectometry for QA/QC of newly fabricated heat exchangers’. Available at: 
 ‘ASTM E2906/E2906M-18 ‘Standard practice for acoustic pulse reflectometry examination of tube bundles’. Available at: www.astm.org/e2906_e2906m-18.html

WHAT THE HEC?! articles are not intended to be the definitive account on the topic or acronym in question. Readers’ comments and contributions are welcomed. Email: ndtnews@bindt.org