TM 5-813-9
each able to handle the peak demand, must be
and availability evaluation are listed as follows --
provided and set-up to alternate. Whenever two or
(1) water demand and emergency storage
more pumps are cost-effective to meet the peak
(2) preventative maintenance
demand, additional pump capacity or pumps must
(3) wear/life expectancy of subcomponent
be installed so that peak demand can be met with
(4) repair
the largest pump out of service. All pumps should
(5) power transmission
alternate. Raw water pumping stations must have a
(6) parallel operation and stand-by equipment
minimum of three pumps. To prevent large pumps
(7) emergency power
from repeatedly cycling on and off during periods
(8) surge protection
of low demand, one small modulating pump,
(9) pumps
commonly known as a jockey pump, shall be
(10) valves
installed.
(11) piping
b. Emergency power. During curtailed power or
(12) motors
brown-out, emergency power is usually provided
(13) controls
by a diesel generator although other standby fuels
(14) time factors
such as gasoline and natural gas may be used if
Reliability evaluation should be part of the planning
available and economical. Diesel engines and diesel
and design process to make certain that a reliable
engine fueling systems are preferred as more
and cost effective design alternative will be
reliable. Emergency power will not be provided for
implemented. Two independent power supplies
standby equipment. Emergency power will be lim-
might be considered for the most critical main
ited to average demand conditions for water distri-
pumping stations. Existing power supplies will be
bution and transmission systems and to 50 percent
investigated to determine historically the number of
of the treatment plant's capacity for raw water
power outages and length of outages occurring
supply stations.
over a pumping period. Where direct connection of
an engine drive to a pump is considered, a cost
as a whole and of its individual components must
analysis will be made comparing engine generated
be determined. Some typical factors and
electric power versus direct engine connection.
components which may be included in a reliability
3-8
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