Modeling One and Twophase Water Hammer Flows - Advances in Control and Automation of Water Systems - page 58

figure 3.5 (a) Pressure Head Histories for a Single Pipe system, Using Steady and unsteady
Friction. (Arturo S. Leon Research, 2007). (b) Rasht city Water Pipeline.
3.4 conclusion
Hydraulic transients can result in the following infrastructure management issues and
risks:
1. Premature aging and wear of valves, pipes, and pumps due to high magnitude
and/ or frequent pressure shocks.
2. Pump cavitations due to low suction head and pipe lining damage due to vac-
uum conditions.
3. Rapid pump or valve operation by major water users (e.g., a food production
factory) may accelerate the pipe material and anchor fatigue in their vicinity.
Rapidly closing or opening a valve causes pressure transients in pipelines, known
as water hammer. Valve closure can result in pressures well over the steady state val-
ues, while valve opening can cause seriously low pressures, possibly so low that the
flowing liquid vaporizes inside the pipe. Results have been showed the maximum and
minimum piezometric pressure (relative to atmospheric). Hydrodynamics instabilities
in a pipeline were occurred. Flow-Time transient curve (for Transmission Line with
surge tank and in leakage condition) has been showed surge pressure equal to 110
(M-H 2 O). Hence, water flow decreased from 3000 (l/s) to 2500 (l/s). This means UFW
hazard was a serious alarm. The valuable observation was the action of leakage point
as an open valve near the water treatment plant pump station. This open valve has been
helped to release of air at exceeding of water pressure. But when vapor pressure was
generated, air has been sucked into the pipeline.