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14 energy-efficiency improvement opportunities in pumping systems
14 energy-efficiency improvement opportunities in pumping systems (on photo: Dakota Pump Packaged Wastewater Pumping Systems via hennesymech.com)

Detailed energy assessment

Pump systems consist of pumps, driver, pipe installation and controls (such as ASDs or throttles) and are a part of the overall motor system. Below some of the energy efficiency opportunities for the pumping system are presented.

Also, American Society of Mechanical Engineers (ASME) has published a standard that covers the assessment of pumping systems, which are defined as one or more pumps and those interacting or interrelating elements that together accomplish the desired work of moving a fluid.

In this standard the procedure of conducting a 14 detailed energy assessment of the pumping system as well as the energy efficiency opportunities are described.

  1. Maintenance
  2. Monitoring
  3. Controls
  4. Reduction of demand
  5. More efficient pumps
  6. Proper pump sizing
  7. Multiple pumps for varying loads
  8. Impeller trimming (or shaving sheaves)
  9. Adjustable speed drives (ASDs)
  10. Avoiding throttling valves
  11. Proper pipe sizing
  12. Replacement of belt drives
  13. Precision castings, surface coatings or polishing
  14. Improvement of sealing

1. Maintenance

Inadequate maintenance lowers pump system efficiency, causes pumps to wear out more quickly and increases costs. Better maintenance will reduce these problems and the most important – to save energy.

Waukesha pumps periodic maintenance
Waukesha pumps periodic maintenance (photo credit: hollandaptblog.com)

Proper maintenance includes the following:

  • Replacement of worn impellers, especially in caustic or semi-solid applications.
  • Bearing inspection and repair.
  • Bearing lubrication replacement, once annually or semiannually.
  • Inspection and replacement of packing seals.
  • Inspection and replacement of mechanical seals.
  • Wear ring and impeller replacement.
  • Pump/motor alignment check.
  • The largest opportunity is usually to avoid throttling losses.

Typical energy savings for operations and maintenance are estimated to be between 2% and 7% of pumping electricity use for the U.S. industry. The payback usually is less than one year.

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2. Monitoring

Monitoring in conjunction with operations and maintenance can be used to detect problems and determine solutions to create a more efficient system. Monitoring can determine clearances that need be adjusted, indicate blockage, impeller damage, inadequate suction, operation outside preferences, clogged or gas-filled pumps or pipes, or worn out pumps.

The control room at Columbia Boulevard Wastewater Treatment Plant
The control room at Columbia Boulevard Wastewater Treatment Plant (photo credit: peci.org)

Monitoring should include:

  • Wear monitoring
  • Vibration analyses
  • Pressure and flow monitoring
  • Current or power monitoring
  • Differential head and temperature rise across the pump (also known as thermodynamic monitoring)
  • Distribution system inspection for scaling or contaminant build-up
One of the best indicators to follow for monitoring is specific energy or power consumption as a function of the flow rate.

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3. Controls

The objective of any control strategy is to shut off unneeded pumps or to reduce the load of individual pumps. Remote controls enable pumping systems to be started and stopped relatively quickly and accurately, and reduce the required labor with respect to traditional control systems.

Remote Control Pump Control Panels For Water Booster Pump System
Remote Control Pump Control Panels For Water Booster Pump System (photo credit: stainlesssteel-storagetank.com)

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4. Reduction of demand

Holding tanks can be used to equalize the flow over the production cycle, enhancing energy efficiency and potentially reducing the need to add pump capacity. In addition, bypass loops and other unnecessary flows should be eliminated.

Energy savings may be as high as 5-10% for each of these steps.

Total head requirements can also be reduced by lowering process static pressure, minimizing elevation rise from suction tank to discharge tank, reducing static elevation change by use of siphons and lowering spray nozzle velocities.

2500 gallon water storage tank with a internal electrical float switch to control the submersible pump systems
2500 gallon water storage tank with a internal electrical float switch to control the submersible pump systems (photo credit: austinlakepumps.com)

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5. More efficient pumps

Pump efficiency may degrade 10% to 25% in its lifetime. Industry experts however point out that this degrading performance is not necessarily due to the age of the pump but can also be caused by changes in the process which may have caused a mismatch between the pump capacity and its operation.

Nevertheless, it can sometimes be more efficient to buy a need pump, also because newer models are more efficient.

A number of pumps are available for specific pressure head and flow rate capacity requirements. Choosing the right pump often saves both in operating costs and in capital costs (of purchasing another pump). For a given duty, a pump that runs at the highest speed suitable for the application will generally be the most efficient option with the lowest initial cost.

Exceptions include slurry handling pumps, high specific speed pumps or in applications where the pump needs a very low minimum net positive suction head at the pump inlet.

High Efficiency Pump Drive
High Efficiency Pump Drive (photo credit: Grundfos)

Replacing a pump with a new efficient one reduces energy use by 2% to 10%. Higher efficiency motors have been shown to increase the efficiency of the pump system 2% to 5%.

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6. Proper pump sizing

A pump may be incorrectly sized for current needs if it operates under throttled conditions, has a high bypass flow rate, or has a flow rate that varies more than 30% from its best efficiency point flow rate (U.S. DOE-OIT, 2005). Where peak loads can be reduced, pump size can also be reduced. A smaller motor will however not always result in energy savings, as these depend on the load of the motor.

Only if the larger motor operates at a low efficiency, replacement may result in energy savings. Pump loads may be reduced with alternative pump configurations and improved operations and management practices.

When pumps are dramatically oversized, speed can be reduced with gear or belt drives or a slower speed motor. This practice, however, is not common. Paybacks for implementing these solutions are less than one year. Oversized and throttled pumps that produce excess pressure are excellent candidates for impeller replacement or “trimming,” to save energy and reduce costs.

Pump and Controls designed an innovative modular booster system ideal for buildings ranging from 5 -150 stories sustaining 50 - 5000 gpm
Pump and Controls designed an innovative modular booster system ideal for buildings ranging from 5 -150 stories sustaining 50 – 5000 gpm (photo credit: callaghanpump.com)

Correcting for pump oversizing can save 15% to 25% of electricity consumption for pumping (on average for the U.S. industry).

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7. Multiple pumps for varying loads

The use of multiple pumps is often the most cost-effective and most energy-efficient solution for varying loads, particularly in a static head-dominated system. Alternatively, adjustable speed drives could be considered for dynamic systems. Parallel pumps offer redundancy and increased reliability.

The installation of parallel systems for highly variable loads on average would save 10% to 50% of the electricity consumption for pumping for the U.S. industry.

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8. Impeller trimming (or shaving sheaves)

Trimming reduces the impeller’s tip speed, which in turn reduces the amount of energy imparted to the pumped fluid; as a result, the pump’s flow rate and pressure both decrease.

smaller or trimmed impeller can thus be used efficiently in applications in which the current impeller is producing excessive heat. In the food processing, paper and petrochemical industries, trimming impellers or lowering gear ratios is estimated to save as much as 75% of the electricity consumption for specific pump applications.

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9. Adjustable speed drives (ASDs)

ASDs better match speed to load requirements for pumps. As for motors, energy use of pumps is approximately proportional to the cube of the flow rate9 and relatively small reductions in flow may yield significant energy savings. New installations may result in short payback periods.

In addition, the installation of ASDs improves overall productivity, control and product quality, and reduces wear on equipment, thereby reducing future maintenance costs.

Similar to being able to adjust load in motor systems, including modulation features with pumps is estimated to save between 20% and 50% of pump energy consumption, at relatively short payback periods, depending on application, pump size, load and load variation.

Pumping control panel with adjustable speed drive
Pumping control panel with adjustable speed drive (photo credit: motorsandcontrol.com)

As a general rule of thumb, unless the pump curves are exceptionally flat, a 10% regulation in flow should produce pump savings of 20% and 20% regulation should produce savings of 40%.

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10. Avoiding throttling valves

Variable speed drives or on-off regulated systems always save energy compared to throttling valves. The use of these valves should therefore be avoided. Extensive use of throttling valves or bypass loops may be an indication of an oversized pump.

Throttling valve example
Throttling valve example

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11. Proper pipe sizing

Energy may be saved by reducing losses due to friction through the optimization of pipe diameters. The frictional power required depends on flow, pipe size (diameter), overall pipe length, pipe characteristics (surface roughness, material, etc.), and properties of the fluid being pumped.

Twin 3,500 gpm drinking water and fire protection pumping systems
Twin 3,500 gpm drinking water and fire protection pumping systems (photo credit: pacewater.com)

Correct sizing of pipes should be done at the system design stages where costs may not be restrictive.

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12. Replacement of belt drives

Most pumps are directly driven. However, some pumps use standard V-belts which tend to stretch, slip, bend and compress, which lead to a loss of efficiency. Replacing standard V-belts with cog belts can save energy and money, even as a retrofit.

It is even better to replace the pump by a direct driven system, resulting in increased savings of up to 8% of pumping systems energy use with payback periods as short as 6 months.

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13. Precision castings, surface coatings or polishing

The use of castings, coatings or polishing reduces surface roughness that in turn, increases energy-efficiency. It may also help maintain efficiency over time. This measure is more effective on smaller pumps.

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14. Improvement of sealing

Seal failure accounts for up to 70% of pump failures in many applications. The sealing arrangements on pumps will contribute to the power absorbed. Often the use of gas barrier seals, balanced seals, and no-contacting labyrinth seals can help to optimize pump efficiency.

Merc fresh water pump seal replacement
Merc fresh water pump seal replacement (photo credit: bdoutdoors.com)

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Reference: Industrial Energy Audit Guidebook: Guidelines for Conducting an Energy Audit in Industrial Facilities – Ali Hasanbeigi, Lynn Price

About Author //

author-pic

Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears.Professional in AutoCAD programming and web-design.Present on

4 Comments


  1. Chandrakant
    Oct 25, 2015

    Articles are very useful in maintenance work of electro-mechanical equipments.
    Please inform on energy savings in Thermal Power Stations, for, Boilers, cooling towers, WTP, STP, ETPs,


  2. mansoor
    May 01, 2015

    I’m electrical engineer I have already work for hyatt hotel construction electrical site engineer


  3. Suhas
    Dec 10, 2014

    I am interested….I am an Mechanical Engineer….


  4. Mohit
    Oct 21, 2014

    Good information..!

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