A Numerical Exploration of Transient Decay Mechanisms in Water Distribution Systems - Advances in Control and Automation of Water Systems - page 22

Column separations due to pump turned off for Rasht city Water Pipeline were
carried out for two cases [20]:
(a) With surge tank and local leakage condition assumption: In this case air was
sucked into the pipeline at negative phase. (Figure 1.9a)
(b) Without surge tank and local leakage condition assumption: In this case air
was not sucked in the pipeline at negative phase. (Figure 1.9b)

1.4 conclusion
It is always a good idea to run research to check extreme transient pressures. It is
necessary for the system with large changes in elevation, long pipelines with large
diameters (i.e., mass of water). Also, it is necessary for the initial (e.g., steady-state)
velocities in excess of 1 (m/s). In some cases, hydraulic transient forces can result in
cracks or breaks, even with low steady-state velocities.
In this chapter positive water hammer in pipeline was introduced with local leak
in two scenarios. First, with the outflow from the leak to the overpressure reservoir,
second: with free outflow from the leak (to atmospheric pressure, with the possibil-
ity of sucking air in negative phase). Field tests results show the leakage condition at
negative phase air was sucked into the Rasht city water-pipeline (Figure 1.9a).There
was minus pressure in a zone near the 50,000 m³ water reservoir (on point no. 124).
So, this volume of air must be removed from the system.

KeyWords

• Hazard alarm

• Kinetic energy

• overpressure reservoir

• transients

• transmission line

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