Anomaly pre-localization in distribution–transmission
mains by pump trip: preliminary field tests in the Milan
pipe system
S. Meniconi, B. Brunone, M. Ferrante, C. Capponi, C. A. Carrettini,
C. Chiesa, D. Segalini and E. A. Lanfranchi
ABSTRACT
In this paper, the reliability of transients due to pump trip as a powerful tool for the pre-localization of
anomalies in real pipe systems is tested. The examined pipe system is part of the one supplying the
city of Milan, Italy and is managed by Metropolitana Milanese SpA (MM). The characteristics of such a
system can be considered as intermediate between those of classical transmission mains and
distribution systems because of its several branches. A Lagrangian model simulating pressure wave
propagation is used to evaluate the pipe pressure wave speed – associated with a genetic algorithm –
and to locate possible anomalies – associated with wavelet analysis. The results of the diagnosis of the
pipe system are corroborated by repairs executed by MM in the area where possible anomalies have
been pre-localized.
S. Meniconi (corresponding author)
B. Brunone
M. Ferrante
C. Capponi
Dipartimento di Ingegneria Civile ed Ambientale,
The University of Perugia,
Via G. Duranti 93,
06125 Perugia,
Italy
E-mail: silvia.meniconi@unipg.it
C. A. Carrettini
C. Chiesa
D. Segalini
E. A. Lanfranchi
Metropolitana Milanese S.p.A.,
Via del Vecchio Politecnico 8,
20121 Milano,
Italy
Key words | genetic algorithm, Lagrangian model, pipe diagnosis, transient tests, transmission–
distribution pipe system, wavelet transform
INTRODUCTION
Traditional design guidelines for the analysis of transients
due to the variation of functioning conditions in pressur-
ized pipe systems contemplated the evaluation of all
reasonably possible combinations of loads to check
system strength. Moreover, transient effects were con-
sidered as a possible cause of accidents only in
transmission mains (TM) where large overpressures could
be due, as an example, to the closing of control valves or
pump trip. In contrast, in water distribution systems
(WDS) transient effects were not assumed as a possible
cause of pipe failure since the numerous branches and
user’s taps behaved as a sort of natural protection device
against pressure waves. In other words, vulnerability of
TM is due to the fact that such systems are closed systems
from the pressure wave propagation point of view whereas
WDS, as open systems, eject most pressure waves. This, of
course, is not generally true: for example, leaks, as an exter-
nal flow, may reduce significantly the effects of a given
transient in a TM as well as pressure waves do not damp
in the parts of WDS with a small demand. In the last
couple of decades, such an approach to transient analysis
in pressurized pipe systems has changed radically from sev-
eral points of view (Boulos et al. ). First, as will be
discussed in more detail later, pressure waves are used as
a tool to check TM condition. Second, in WDS transient
events can have significant water quality and health impli-
cations as well as cause background leakage due to the
fatigue of joints. Third, TM has evolved towards more com-
plex topologies – with several branches and connections –
to ensure the necessary flexibility of functioning
conditions.
Even if properties of pressure waves partially reflected
by any anomaly – as an example, leaks, partially closed in-
line valves, partial blockages – have been known for a
long time (e.g. Babbitt ; Contractor ), attention of
researchers has been captured by transient test-based
377 © IWA Publishing 2015 Journal of Hydroinformatics | 17.3 | 2015
doi: 10.2166/hydro.2014.038
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