Solution to Pump Challenge #4


Written by:
Dr. Lev Nelik, P.E. APICS
In Pump Challenge #4, many of you discovered while using the Energy Consumption Evaluator, that the standard listing only goes to 8x6-17 pump size with motor power maxed at 250 hp, which is below the larger pump size considered here (4,000 x 400 x 3,960 = 404 hp, not adjusting for efficiency as a first rough estimate for motor power).
We will select the "Sample" tab and enter 404 hp. (The program will also evaluate the effect on the cost savings, in dollars, if an upgrade is under consideration. The program makes some simplified, but consistent, assumptions internally for the effect on efficiency improvement by a typical upgrade. The dollar amount of the upgrade is arbitrary-$10,000 is assumed for this example-to evaluate the effectiveness of the proposed upgrade to improve efficiency). A $0.10 per kWh cost of energy is assumed

photo of Energy Savings Evaluator Program

Comparing the result to the Efficiency Evaluator program in Pump Challenge #3, the effect of speed is not presented here because the difference was only about 1 percent, due to the pump size change and the Specific Speed factor effect. The effect of overall pump deterioration, like worn out rings (leakage), is a much greater concern in this challenge. Such effects greatly influence pump health (efficiency), and that is what we evaluated.

Life cycle losses can reach into the millions-even for relatively low power units (under 500 hp). Imagine what this may mean for even larger units, like main station feed pumps.

Click here for Pump Challenge #5: Correctly Sizing Pump


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