Design of Transient Tests for the Diagnosis of Transmission Mains

In the last two decades, increasing attention has been paid to the Transient Test-Based Techniques (TTBTs) for the diagnosis of long transmission mains (TMs). In fact, the usual distrust – which derives from the misunderstanding that reliable results could be achieved only if large and, therefore, potentially dangerous, pressure waves are generated – has been overcome. As a matter of fact, pressure waves can be very small as long as they are sharp, and applications of TTBTs increased, because of the simplicity and shortness of the tests, as well as the modest cost of the necessary instruments. For these reasons, TTBTs are undoubtedly competitive with the techniques – quite invasive – which involve the insertion of probes in the pipelines, or the realization of "points of listening” for the leak a few hundred meters away from each other.

This paper illustrates the possible methods for generating suitable transients for a reliable diagnosis of TMs without compromising their integrity. For each method, the main characteristics are highlighted as well as limits and potential weaknesses are discussed. Moreover, the results of some experimental tests carried out at the Water Engineering Laboratory (WEL) of the University of Perugia (Italy) are reported.