MIL-HDBK-1005/9A
2.5.3.2
Capacity. Provide a total pumping capacity equal to
the maximum expected flow with at least one of the largest pumps
out of service. Install a minimum of two pumps in any station.
In small stations with a maximum inflow of 500 gallons
per minute (gpm) or less, normally provide only two pumps, each
with maximum capacity. An exception to this practice would be
when this station is the only one pumping directly to a
treatment plant. For larger stations, select pump number and
capacities so that rates-of-inflow may be matched as nearly as
possible. The inflow may be matched by varying sizes of pumps,
selecting multiple speed pumps, or by variable speed pumping.
Variable speed pumping may completely match inflow and may
reduce the necessary wet-well storage volume. Variable speed
pumps are the most desirable types to use when pumping directly
into a treatment plant.
2.5.3.3
Pumps. Submersible centrifugal pumps installed in a
sump are the preferred approach. Pump controls should be
automatic based on wet well level. The controls should perform
the following functions: starting and stopping, sequencing,
alternating, sounding alarms, and low-level shutoff.
2.5.3.4
Force Mains. Force mains should be kept as short as
possible. Check possibility of sulfide generation. Make
provisions to control sulfide generation if necessary by
injecting oxidizing chemicals such as chlorine, permanganate, or
hydrogen peroxide. Consult suppliers of chemicals or generation
and feed equipment on costs and expected performance.
a)
Maintain minimum flow velocity of 3 fps (0.9 m/s).
b)
Provide clean-outs and air relief valves as
required.
2.5.3.5
Dependability. Use two separate and independent power
sources with automatic switching equipment. Evaluate either two
independent incoming powerlines or a standby engine-driven
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