TM 5-813-9
expert should be considered under the following
for a pipeline.
design conditions:
(7) Specialized computer programs for hydrau-
(1) Generally, if the interaction of pump station,
lic transient analysis are listed in Appendix B. A
piping system, valves and control system is complex
case study for control for hydraulic transients
following a power failure or during startup
created due to power failure and when using air-
conditions.
vacuum valves is included in Appendix D.
b. Surge control methods. The most common
(2) If power failure at the pump station would
result in significant reverse flow, which can slam
devices to overcome the effects of excessive hy-
check valves or cause a fluid rejoinder surge. In a
draulic surge pressures in water pumping systems
system with a flat pipeline profile, reverse flow
include --
surges are usually not significant. In a system where
(1) Spring or weight-loaded check valves,
the pumps work against a significant static lift,
which are designed to close before the hydraulic
surge pressures can be many times the maximum
pressure wave reverses. This device may protect
steady state operating pressure.
the pump but will not eliminate the water hammer
(3) If the pipeline profile has significant inter-
in the rest of the system.
mediate high points where the fluid may separate,
(2) Surge relief valves, which will open at a
following power failure, and result in high surge
preset surge pressure but do not prevent the
pressures upon rejoining.
occurrence of the water hammer. They are fre-
(4) If the pump station or individual pump take
quently used as a back-up for other control meth-
suction through a pipeline of significant length
ods. Several manifold mounted relief valves will be
(several hundred feet) a power failure may result in
considered in lieu of one large relief valve to
high pressure heads. For pumps located
minimize water wastage.
immediately adjacent to storage tanks, suction line
(3) Air cushioned surge tanks, which will ab-
pressure transients are usually insignificant.
sorb pressure increases in stopping and starting
(5) If the pump station is equipped with dis-
pumps. If properly designed they will reduce pres-
charge check valves and air vessels, the check
sures to protect the system. Space requirements and
valves may be slammed shut by the air vessel or
costs have limited their usage in water pumping
parallel connected pumps following power failure.
systems. Hydropneumatic tanks used in connection
(6) If the preliminary hand calculations indicate
with smaller water pumping and distribution
that surge control equipment is required in the
systems will absorb some pressure increases but are
system, optimum performance and surge control
not designed for surge control.
equipment selection could be established through
(4) Pump control valves as part of a surge
detailed surge analysis. As a general rule; surge
control system including valve, power and manual
analysis should be performed for vertical turbine
valve, operators, accumulator, sensing and record-
pump installations and any pump installation where
ing devices. This system automatically prevents
individual pump capacity exceeds 500 gum. A
water hammer in starting and stopping of pumps
typical checklist of information required for a
and should include safety features in its design to
detailed surge and water hammer analysis is shown
prevent damage from malfunctioning equipment.
in figure 4-4. The example in figure 4-5 shows the
Design and operation of the surge control system
total surge head exceeding the allowable surge head
should be coordinated with the manufacturer.
CHECKLIST OF INFORMATION REQUIRED FOR DETAILED SURGE AND
WATER HAMMER ANALYSIS.
1. BASIC SYSTEM DIAGRAM OR SCHEMATIC
a. Diameters, lengths, wall thickness of piping elements
b. Elevations (pipeline, pump suction/discharge, etc.)
c. Valve and fitting locations
d. Pump location and arrangements
2. FLUID PROPERTY DATA
a. Description of the fluid being transported (potable water)
b. Specific gravity
c. Bulk modulus of elasticity
d. Fluid viscosity
e. Temperature
f. Vapor pressure
Figure 4-4. Checklist Surge and Water Hammer Analysis
4-4
Previous Page
