Acoustic Emission Examintion:

Flat bottom tanks with a storing capacity of up to 150.000 m³ are used world-wide. From the outside the flat bottom is neither accessible nor visible. These tanks must be inspected in certain intervals, as undiscovered leakages can cause considerable environmental pollution. For conventional testing methods the tanks must be emptied, opened and cleaned for the visual inside inspection.

This method is time-intensive and the tanks are not available during the inspection. By applying the acoustic emission examination the bottoms of the full tanks can be searched for leakeages and active corrosion. Not only the existence but also the position of the leakages can be detected. Above all, the reliability of the information gained is higher than that resulting from a normal level examination and a visual inside inspection.

For carrying out the examination sensors are applied evently around the outer side and if possible invasive inner sensors are lowered into the container. During the measurement of only few hours the tank has to be kept on its highest level. The acoustic signals emitting from active leakages and/or corrosion are recorded. On the basis of the transient signals and their time of arrival referring to crossing the threshold and/or cross correlation the existence and position of the source of sound can be determined.

The testing method was developed by TÜV Austria in 1980 and has been improved permanently. So far hundreds of tanks with a diameter of up to 100 m have been examined. In most cases leakages and other failures could be detected, especially when both methods (threshold crossing and cross correlation) were combined.

The locating accuracy is ± D/10 (D=diameter) for tanks with many installations inside (heatings) and ± D/20 without installations. In Austria the leakage test of flat bottom tanks by means of acoustic emission examination is highly recognized by the authorities.