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Hydraulically rerating an existing booster pump station to reduce energy cost by €99k a year

SAM4 Energy advised to hydraulically rerate one of the two identical booster pumps operating in the same process. This would ensure backup functionality and prevent downtime during rerating. The investment pays for itself in less than 7 months.

pump savings chart water

Rerating one pump triples performance

• Two identical booster pumps operated at a significantly lower flow, resulting in a drop in efficiency from 69% to 23%.

• The recommended solution was to hydraulically rerate one pump to improve efficiency and run it 90% of the time.

• Rerating only one pump would save costs, pay for itself in less than 7 months, and provide backup during rerating and for higher-flow requirements.

pump diagram water

Pump operation far from best efficiency point revealed by data

SAM4’s real-time pump curve and operating data for the first pump, showing operation far to the left of the best efficiency point (top right). Data for the second pump were similar.

Problem

Two identical booster pumps in the same process operated sequentially as an A/B pair. The pumps were designed for a duty point of 540 m3/h at a head of 217 m. Using its real-time pump performance curve and operational data, SAM4 Energy identified that the two pumps actually operated at a significantly lower flow, near 100 m3/h. As a result, the pumps’ efficiency had dropped from the rated maximum of 69% to only 23%.

Solution

Our Energy team investigated three potential courses of action. Our recommended solution was to hydraulically rerate one of the two pumps so that its best efficiency point was nearer to 100 m3/h. By running this improved pump 90 percent of the time (instead of alternating the two pumps), the pump owner would nearly triple the station’s efficiency.

In making this recommendation, our Energy team considered the following practicalities:

  • Rerating both pumps would save slightly more each year, but take twice as long to pay for itself.
  • Buying new pumps instead of rerating would cost more for no additional benefit.
  • By rerating only one pump, the second pump would be there to handle any higher-flow requirements if they should occur, and to operate while the first pump was being rerated, to prevent downtime.
  • Six months of operational data showed that using the improved pump for 90% of the flow would be roughly 500 hours per month, which was feasible.

At a cost of roughly €50k, the rerate would pay for itself in less than 7 months.

Impact

energy case impact table

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