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Pumping System Efficiencies: Energy Saving Investigation Process

What do the icons below mean?

  • Pumping system efficiencies are decreased if:
    • Brown IconThe pump is operating outside of its pump curve efficiency range.
    • Brown IconThe pump is worn or not of a proper design.
    • Brown Icon The flow of water is restricted or throttled on the suction (and/or) discharge side.
    • Brown IconThe electrical control system, i.e., VFD is not designed for the application. This is common in high head pumping systems where a VFD controls the whole flow in just a small band if Hz. VFDs are not always efficient in these cases.
    • Brown Icon The Distribution System is not routing and controlling the flow of pumped water properly to its destination, i.e., re-pumping or short circuiting, faulty PRVs, etc. (see System Modeling Efficiencies.)
    • Brown Icon Other Distribution System Problems, i.e., storage issues, leaks, corrosion, pipe age and quality, under sizing, etc.
    • Brown IconPump station pipe materials and fittings are corroded or tuberculated, increasing the friction coefficients.
    • Brown IconThe electrical Load Factor is too low and the head losses on the distribution system are excessive. Load Factor (LF) is a fractional number or percentage indicating the average amount of time per day a motor or pump runs, i.e., a Load Factor of 0.25 or 25% means the pump runs on average six hours per day.
    • Brown Icon The electrical system Power Factor (PF) is not efficient or too low.
    • Brown Icon The water system Peaking Factor is too high (above 2.0).
    • Brown IconThe pumping systems are not cooled properly.
    • Brown IconMetering issues, such as old worn meters, no master metering strategy, and no leak detection. etc.
  • Green IconPump curves and pump performance should be regularly reviewed and tested. Test each pump on at least four points on the curve. Have a VFD curve available if the pump is on a VFD and test at several speed points.
  • Green Icon If you use the most economic utility power rate for your pumping systems, significant money can be saved.
  • Green Icon If you pump during the designated off peak periods of the electrical utility, you can also save money by completely eliminating or reducing the Power Demand Charge. Adequate storage capacity is essential to follow this strategy.
  • Green Icon If you use Variable Frequency Drives (VFDs) to increase your Load Factor, or use jockey type pumps, you reduce your costs by reducing your demand and energy charge.
  • Green Icon If you have a high head loss on a pump plant, a VFD can reduce your energy cost by reducing the total dynamic pumping head.
  • Blue Icon If you are charged a power factor penalty, you can eliminate that charge by implementing power factor correction strategies.
  • Blue IconPump cycles and operation should always be selected for efficiency, yet be prepared for any emergency operation scenario.
  • Green Icon Always match the VFD to the proper pump and pump curve.
  • Never use a restrictor valve to control the flow rate of a pump.
  • Green Icon Run pumps more often (prioritize) based on their costs per unit of water pumped, also referred to Specific Energy. If possible, choose the most efficient pumps first in a system for pumping.
  • Green IconCarefully develop effective multiple pump rotation and lockout strategies.
  • Blue Icon Provide for pump back-up strategies.
  • Blue IconCarefully review the necessity for pump trimming when using a VFD. Often the VFD acts as the pump trim.
  • Blue IconEvaluate multiple and smaller pump designs, vs. one or two large pumps in a pumping plant.
  • Blue IconReview well and pump designs to evaluate if a line drive pump is more efficient than a submersible pump system. Submersible motors are typically less efficient.
  • Blue Icon Implement SCADA and control system lockouts to prevent operators from running multiple pumps when not needed, or bumping pumps unnecessarily during an on- peak pumping period.
  • Blue IconProvide engineered pressure and surge protection systems to better protect distribution infrastructure and pumps from wear, breaks, leaks, etc.
  • Blue Icon Provide or specify motor shaft grounding brushes to protect bearings on VFD operated pumps.
  • Blue IconTypically small jockey type pumps should run first and as long as possible to extend the load factors as much as possible. A load factor above 80 % is not unrealistic, in fact it is preferred.
  • Green Icon Regularly evaluate for service or replacement any old and worn pumping equipment.
  • Green IconUse high performance lubricants on motors for extended performance and lower operating temperatures, and maintain levels.
  • Green IconWell “pump to waste” cycles typically run pumps at their highest energy and power demands. Provide a back pressure or pressure sustaining valve in line with the pump control valve, or add a sustaining pilot on the pump control valve, to hold waste discharge pressures closer to the efficiency point on the curve. Ensure that these valves are not oversized. They should provide a significant back pressure simply as a function of their size. An alternative for a VFD controlled pump would be to run the waste cycle at a lower speed.
  • Green Icon Evaluate your pump exercise and water testing strategies. Avoid running a pump for a short period just to exercise it. If a pumping system needs this, evaluate running it in an off-peak period or on a generator regularly. The same applies to running well pumps for a simple water test, when they would normally be idle for a month or more.
  • Blue Icon Ensure that your well and well pump performance matches its design characteristics and pump curve. Also monitor well static and dynamic drawdown and specific capacity over time. If there are irregularities—the pump may be worn, or the pumping column may be leaking into the well annular space. When changing or servicing well pumps, perform a video inspection to ensure that the well casing is in good condition. A corroded or malfunctioning casing and screen system will restrict flow into the well casing and lower drawdown levels, thus increasing energy and power requirements.
  • Green Icon In summary, implement water pumping and operational management strategies similar to the following:
    • Green IconReduce energy usage on pumping facilities by ensuring that pumps are not running at a level or in a configuration which increases head losses in the pumping or piping systems.
    • Green Icon Eliminating a possible return flow loop or leak in a pumping station through relief/surge anticipator valves or emergency fire flow PRVs.
    • Green Icon Review pump curves to better limit Variable Frequency Drives (VFD) to their optimum frequency range settings.
    • Green IconAvoid “across the line” starters for motors where possible. Reduced Voltage Soft Starters (RVSS) and VFD’s are usually better, depending on the application, and offer far better motor protection strategies.
    • Green Icon Monitor temperatures and environmental variables better in all pumping and other remote facilities to get better controlled energy use for heating and/or cooling. Use motion detectors for lighting controls and install more efficient fluorescent (T5 or T8) or LED lighting.
    • Orange Icon Blue IconEvaluate and implement better and more efficient cooling systems for the
      larger pumping facilities, to not only save energy but extend pump life.
    • Orange Icon Improve the efficiency and reliability of larger HVAC heating and cooling systems by, monitoring air pressures, humidity, and other parameters. And to better control operation in the winter months, using the heating systems only when needed. Integrate HVAC controls into PLCs and integrate with system SCADA equipment. Investigate using the water itself for cooling and heating (i.e., Water Furnace technology).
    • Orange Icon Ensure where feasible, that pumps controlled by Variable Frequency Drives (VFDs) do not have their impellers trimmed, thus allowing for a wider range of operational flows and pressures.
    • Orange Icon Large pump motors should be wound with RTDs (temperature sensors), and associated motor protection relays, to better monitor motor winding conditions.
    • Orange Icon Establish power quality meters on larger facilities with daily SCADA logging capabilities.