ETL 1110-2-367
31 Mar 95
Figure 5-3. Pump station concepts
inlet to the station and should be designed to pass flow into the
characteristics. The operating head, 100 percent efficiency, and
sump with a minimum of head loss and flow disturbance. For
maximum head are used to define the pump characteristics and
open channel approaches, reversing the invert slope away from
efficiency used in planning and design studies.
the station, if practical, is done to minimize siltation and
pumping station dewatering problems. The ability to maintain
(8) Additional hydraulic information besides the pump
an even flow distribution minimizes vortex formation. If an
capacity is required. Various pumping heads needed for
unacceptable vortex forms during pump operation, it could
mechanical design are shown in Figure 5-3 and are described
eventually damage the impeller and pump bearings.
below.
(6) The pumping station selection is part of the planning
(a) The priming head is the difference between the lowest
process. The feasibility of pumping stations is based on
pump start elevation and the center line of the discharge pipe at
economics and other considerations. In general, the without-
its highest point.
pump condition (with gravity outlets and detention storage
implemented) must show adverse effects under present and the
(b) The operating head considers the full range of interior
most likely future condition. Implementation of a pumping
and exterior elevations for pump operation. The operating head,
station must reduce the adverse effects sufficiently to justify the
also called the total head, is the sum of the estimated head losses
construction and operation of the facility. Finally, it must be
and the static head. The estimated head loss is the summation
demonstrated that the implementation of a pumping station is
of all the head losses for the pump discharge system, including
the most effective means of reducing the adverse effects.
friction loss, pipe bend loss, etc. The static head is the exterior
river elevation minus the interior elevation at the pumping
(7) The feasibility study should investigate the general
station. The data input to HEC-IFH for each pump unit
characteristics of the pumping station that might include number
analyzed gives the operating head information for a pumping
and type of pumps, and on-off elevations to the detail necessary
unit at various flow capacities.
for plan evaluation and selection. These and other features are
finalized and detailed in the design phase. The number and
(c) The high head condition is the difference between the
types of pumps are determined to provide the total capacity
lowest stop elevation and the highest exterior elevation.
developed in the planning study. Pump on-off elevations are
specified.
Pumping heads for efficiency and starting
(9) First or operation floor elevations of pumping stations
assumptions are specified for various combinations of interior
should be, as a minimum, at or above ground level to provide
and exterior stage conditions. Figure 5-3 shows key pump
convenient access to equipment, to eliminate need for protection
5-5
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