Design Guides

As a preliminary design guide (Section 10.1), published information may be used to establish pump sump dimensions and a minimum desired submergence.7-10 Figures 1 and 2 of Section 10.1 show the basic layout of a pump sump and present typical dimensions in relation to the flow required per pump, as published by the Hydraulic Institute.7 Some of these references may express sump dimensions in terms of bell mouth diameter, and Figure 3 shows the typical relationship between design flow for a given wet-pit pump and the bell mouth diameter required to achieve reasonable and desirable velocities approaching the impeller. One should be aware that the sump dimensions and minimum derived submergences given by design guides are considered applicable for the ideal condition of a simple, straight approach flow with a constant, low approach velocity to the pump sump.

The need for a physical model study still exists when site or operating conditions make the ideal condition impossible. For example, for a particular pump intake configuration, a hydraulic model study indicated that a strong submerged floor vortex existed with floor clearance of 0.5 times the bell diameter (a usual design value) and that a reduced floor

0 100 wo 300 <00 600 600

pump flow (cfsi

FIGURE 3 An approximate relationship between design flow and required suction bell diameters for vertical propeller pumps for preliminary evaluations.

0 100 wo 300 <00 600 600

pump flow (cfsi

FIGURE 3 An approximate relationship between design flow and required suction bell diameters for vertical propeller pumps for preliminary evaluations.

clearance of 0.3 times the bell diameter eliminated the vortex. Typically, for pump intakes of the following types, model studies should be considered essential:

1. Intakes with nonsymmetric approach flow; for example, an offset in the approach channel

2. Intakes with multiple pump bays with a common approach channel and a variety of pump operating combinations

3. Intakes with pumps of capacities greater than 40,000 gpm (2.5 m3/s) per pump

4. Intakes with expanding approach channel

5. Intakes with possibilities of screen blockages or obstructions close to suction pipe entrance; for example, reactor containment recirculation sumps, gate guides for dry-pit pumps

6. Dual flow screens intake

For items 1, 2, 4, 5, and 6, a model study is recommended because of the unknown effects a nonuniform approach flow can have on vortexing and swirl. For item 3, considering the cost of large pump installations and the cost of backfit, should problems occur, a model study is recommended to ensure proper pump operation.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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