First of Two Parts
by Lev Nelik, Ph.D., P.E. (Pumping Machinery, LLC)
October 26, 2015

Despite an increasing focus on energy savings around the world, no formal standard—that is also simple and practical—exists. A recent pump energy conference in the Middle East took a comparative look at available resources on the subject in the U.S., Europe, Israel and other areas of the world. Several fledgling documents on formalizing the approach are in the works, but nothing is complete to the point of availability to the pumping community.

In the U.S., the Department of Energy (DOE) has proposed new efficiency standards for commercial and industrial pumps1, with the hope of having something issued by the end of 2015. Unfortunately, the scope of the project appears to some to be too grand and not specific enough. While it stresses the importance of saving energy, it remains an overall assessment of energy consumption by pumps and motors, leaving out practical "how-to" details.

The European Standard IEEE EN 505982 is also an attempt in the right direction, but it mainly deals with motor efficiency, drives and other electrical aspects.

In Israel, the Ministry of National Infrastructures/Department of Energy Conservation has been conducting work to assess the impact of potential improvements in overall systems efficiency for installed pumps (and other machinery). The department set guideline values for pump efficiencies for different pump types, but the values do not yet account for design details (such as number of stages, flow or power rates, and other factors). Regardless, it is a starting point in establishing reasonably achieved values. The nation's ongoing energy conservation programs are planned to refine and fill the details.3 This work is also supported by the Standards Institution of Israel.

Field measurements of actual versus predicted pump efficiencies have also been conducted by the Pumping Machinery Technology Center in the U.S. and in Israel, as presented at the recent conference on the subject.4a/b

The overall state of creating pump efficiency guidelines is still in rudimentary form, and progress is slow because of many factors, including technical aspects, logistics, political impact and a diversity of opinions on the approach and content of the end-product publication. Several reasons exist for the stalemate in progress, and given the diversity of needs and parties involved, slow progress in this arena is completely understandable.

Actual Efficiencies of New OEM Pumps

While the subject is of great commercial importance during a pump's procurement process—and mainly of interest when large units (typically 1,000 horsepower [hp] and up) are being bid—this should not be the main focus of the effort. The difference in quoted efficiency for new pumps of similar design rarely varies more than +/- 1 percentage point. Most established pump manufacturers have been producing pumps for many years and have evolved the designs (often by the same designers who might have worked at several competitors over the years) to the point that manufacturers can do little to outperform their competitors in regard to efficiency.

For a large pump, even a single point of efficiency could mean significant savings. For example, a double-suction split-case pump operating nonstop burns about $3.3 million per year. This translates to about $30,000 per each point of lost efficiency. This, however, still represents only a statistical variation from one bid war to the next, when the situation often reverses. The bigger picture, as we will touch on later, is elsewhere.

Actual Field Efficiencies of Installed Pumps

The actual field efficiencies of installed pumps are where great differences from the initial original equipment manufacturer (OEM) efficiencies are noticed. Studies show that efficiencies of installed pumps are commonly reduced by 10, 20 and often close to 50 percent below the OEM quoted (rated) point.4a/b There are good reasons for this trend, including wear over time (clearances), changed flow conditions, degraded internals (impellers, casing) and other factors. As studies also show, the majority of pumps in the U.S. operate essentially with few recorded values of efficiency trends, and millions of dollars are burned daily because of this lack of information about pump operation and the energy consumption associated with it.

Part 2 of this series will discuss a user-oriented approach to measuring system efficiency. Read it here.

References

  1. Maurer, J., "Proposed Pump Efficiency Standards," DOE, March 18, 2015
  2. Gross, A., "Energy Efficiency Indicators for Power Drive Systems and Motor Starters," Sept. 8-9, 2015, PumpTec-Israel-2015, conducted at Israel Water Works Association
  3. Bet-Hazavdi, E., "Energy Conservation for Rotating Machinery via Efficiency Improvements," DEC Israel, PumpTec-Israel 2012
  4. a. Nelik, L., "Energy/Efficiency Studies by On-Line Efficiency Monitoring System (PREMS-2A)," doctorpump.com
  5. b. Nelik, L. and Moskovich, D., "Efficiency Evaluation for the Vertical Turbine Pump, Clean Water Well," Weizmann Institute Israel
Editor's Note: A reader asked about the characteristics of 300 and 400 series stainless steel as discussed in Part 3 of "Efficiency Monitoring Saves Plants Millions" (Pumps & Systems, September 2015). According to Dr. Nelik, the reader was correct in pointing out that carbon steel and the 400 series are non-magnetic, but the 300 series is magnetic. For further questions, please contact Dr. Nelik at drpump@pumpingmachinery.com. Thanks to our readers for their careful attention.