In-line partially closed valves: how to detect by transient tests

Reliable and quick techniques are needed to locate and estimate the asset of in-line partially closed valves in pressurised pipes. The methodology considered in this paper is based on the analysis of transient tests. As a matter of fact, singularities (e.g., junctions, partial blockages, partially closed in-line valves, leaks) give rise to reflected waves whose arrival time and amplitude – recorded in one or more sections of the pipe – allow their detection. Transients are generated by means of a total and fast closure of an end valve and the pressure time-history – referred to as pressure signal – is measured at a section immediately upstream the end valve. In the paper, first some numerical simulated signals show that this kind of analysis can be useful for locating the valve and determining its asset, also by means of two simplified numerical models. Then some results of an extensive laboratory campaign carried out at the Water Engineering Laboratory (WEL) of the University of Perugia, Italy, are reported.