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Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

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48 <strong>Centrifugal</strong> <strong>Pumps</strong>: <strong>Design</strong> <strong>and</strong> <strong>Application</strong><br />

Step 3<br />

Establish next size pump by multiplying each base line BEP by<br />

• GPM x 1,75<br />

• Head x 1,45<br />

Example: Smallest pump on chart has BEP of 86 GPM <strong>and</strong> 150-ft<br />

head. Thus, BEP for next size pump = 86 x 1.75 = 150 GPM <strong>and</strong><br />

150 x 1.45 = 220 ft. Repeat this step for each base line BEP. As can<br />

be seen from the chart, the head of 220 ft now requires a 9-in. impeller,<br />

Step 4<br />

For all additional pump BEP's multiply prec<strong>ed</strong>ing pump flow by<br />

1.75 <strong>and</strong> head by 1.45.<br />

The constants 1.75 <strong>and</strong> 1.45 are recommend<strong>ed</strong> for a well-plann<strong>ed</strong> performance<br />

chart following a number of constant specific spe<strong>ed</strong> lines.<br />

There are no gaps between pumps, each performance block can be cover<strong>ed</strong><br />

by normal impeller trim, <strong>and</strong> there are no overlaps. The chart is also<br />

helpful to the designer. In this example, only six small pumps have to be<br />

Figure 4-2. Recommend<strong>ed</strong> performance chart.

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