Modeling One and Twophase Water Hammer Flows - Advances in Control and Automation of Water Systems - page 54

Hydraulic transient impacts can be expected at the following locations :
1. Check valves at pumps (as flow reverses from the downstream reservoir to the
pump).
2. Reservoir inlet valves, altitude valves at elevated tanks, or isolation valves if
they close rapidly.
3. Local high points where vapor or air pockets collapse.
4. Dead ends as they reflect incoming pulses with up to double the wave ampli-
tude.
5. Pipe bursts, where flow leaving the system may exceed the steady-state flow
(in systems with high static head compared to the dynamic head).
6. Surge-control devices if not properly designed or operated.
7. Changes in pipe-line profile or alignment (where transient forces may be sig-
nificant).
Hydraulic transient impacts can be expected to occur at the following:
1. Pump startup before transient energy has decayed sufficiently or before all air
has been removed from the line.
2. Pump emergency shutdown which may result in water-column separation
and severe transient pressures due to vapor or air pocket formation and col-
lapse.
3. Pump shifting during normal operations, which may result in frequent pressure
shocks. Environmental concerns due to hydraulic transients include:
a. Sewage spills or leaks to soils or groundwater during high transient pres-
sures.
b. Drinking water contamination due to air, debris, or groundwater intrusion
during sub atmospheric pressures. (Table 3.3-3.5).
c. Service interruptions due to repair and maintenance of infrastructure [12-
13].
research field tests model (water pipeline of rasht city in the north of iran)
Software Hammer - Version 07.00.049.00
Type of Run: Full
Date of Run: 09/19/08
Time of Run: 04:47 am
Data File: E:\k-hariri Asli\ daraye nashti.inp
Hydrograph File: Not Selected
Labels: Short