APR Technology Overview
In order to perform inspection of HEX or boiler tubes utilizing APR, we need 3 components: Source of acoustic pulses (loudspeaker), receiver of acoustic waves (microphones), and the object of inspection (tube). Principle behind the APR is to inject an acoustic pulse into the air enclosed by the tube, which will propagate down the tube axis. Any change in the cross section in the path of the pulse will create reflected waves, which will propagate back up the tube. These changes of inner diameter (ID) cross section can be caused by obstacles inside the tube, wall loss on the ID of the tube, through wall holes (TWH), but also structural events on the tube such as U-bend, rolling of the tube to tube sheet, end of tube (EOT). Some of these structural changes can be seen in Figure 1.
Figure 1: Schematic description of typical blockage and ID wall loss in a tube
Reflections that are created can be measured and analyzed, and from signal interpretation we can understand if there are any discontinuities in the tube ID cross section uniformity, and we can understand their type, position and size.
Presentation on the working of APR Technology
Principles of the Acoustic Pulse Reflectometry, advantages and limitations of the use of APR are written down in the presentation “Sound Wave Inspection Systems_Sonic V”
White Paper on APR Technology
The exact detailed description of the working of APR you can read in the White Paper: “Sonic V – Acoustic Pulse Reflectometry (APR) Inspection System”