Why Test Your Pump for Efficiency

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Pumps and pumping systems are some of the most costly equipment used by water utilities and other large operations that transport water. Despite their importance, the actual parameters for pump performance are often largely unknown by anyone except the engineer who designed the pumping system. Even operators tend to see pump systems as an unknowable and unchangeable part of their work environment. Yet this seeming lack of knowledge regarding the most important tool in many fluid-transporting systems can sometimes become a real problem.

While most pumps used in large-scale operations are typically robust, their efficiency declines over time like any machinery. This is especially troublesome when such pumps support integral operations like fire suppression systems in large commercial buildings or facilities that treat a municipality’s wastewater. Pump efficiency will lessen as parts wear out, regardless of the purpose for which it’s used. When water pump efficiency declines, those tasked with system maintenance have more control than they realize, and resolving pump issues begins with testing.

Water Pump Efficiency in Largescale Pumping Operations

Whether it’s a pumphouse that controls the flow of water through canal locks, a pump in a sewage treatment plant, a large pump for a water-based heating and cooling system in a large commercial building, or for another application, most big pumping systems are designed to transport large amounts of water. Pump efficiency for these larger systems is often ignored, and the ability to handle the rigors of regular use is taken for granted. While infrastructure on these systems is meant to last, water pump efficiency measures taken by operators can significantly decrease the costs for these large-scale operations.

Largescale and commercial pumping operations include: 

  • Canal pumping station: These are used to operate canal locks since water is lost to the lock with a lower elevation each time a ship passes through the lock. As lock gates aren’t watertight, they also transport water back to the more elevated locks to ensure they remain navigable. These will sometimes also involve back-pumping systems.
  • Chilled water-cooling systems: Providing cooling for large commercial buildings, these pumping systems are part of a plant that distributes chilled water to cool off equipment like processing equipment, chilled beams, and air handlers.
  • Commercial boiler systems: Hydronic heating systems used in certain older buildings or complexes use pumps to transfer hot water and heat energy. It comes from the boiler where water is heated, continuing to a radiator before returning to the boiler in a closed loop. These systems involve check valves, expansion tanks, pipes or tubing, and strainers.
  • Fire protection systems: Often, office buildings, schools, and other large buildings will be equipped with a sprinkler system to protect occupants and properties from fires. These systems include a controller, driver, fire pump, and other accessories.
  • Land drainage: For low-lying areas, especially those below sea level, pump stations are sometimes used to remove floodwater. Pump efficiency is particularly important to restore flooded land by removing water and transporting it towards channels that lead to waterways and other bodies of water.
  • Plumbing systems: In high-rise buildings, a pump is necessary to bring water to the building’s upper floors. These types of systems apply pressure to pump water efficiently at a pressure and flow rate that allows plumbing fixtures to operate properly on the building’s higher stories.
  • Sewage pumping stations: These handle raw sewage, fed through gravity piping underground into what’s commonly called a wet well. Equipped with electrical monitoring devices, once sewage rises to a certain point, the pump lifts it upwards into a pressurized piping system that transports it to a treatment plant. These are often end-suction centrifugal pumps with open impellers, which generally pump more quickly, making the pump easier to repair and keep clean.
  • Wastewater pumps: Used in larger buildings, these pumps transport fluids from drains, sinks, toilets, and other wastewater sources, including gray water. Pump efficiency is essential to ensure the effluent is transported effectively, along with any organic and inorganic solids in the wastewater, before going to a treatment facility.
  • Water pumping stations: Built-in areas where there’s a demand or projected demand for water, pump efficiency needs may vary depending on the purpose for which they’re used. Applications might include:
- Water pumped directly from a lake, river, or other body of water.
- Source pumps that transport water into a raised tank.
- Recirculating pumping systems that transport water into a raised tank.
- Pressurized pumping of treated water back into the distribution system from a water treatment plant.
- Systems without tanks for storing water that pump it efficiently through distributed piping.

The above facilities work specifically with effluent and/or water, so regardless of size, each facility’s operations depend on some type of water pump. Efficiency in energy usage translates to cost reduction, as pumping systems that are kept in good working order can pump more water with less energy. In plants that treat municipal wastewater, pump efficiency will often entail looking at electricity or other power sources, which generally comprise a significant portion of costs for the entity overseeing the facility.

Importance of Water Pump Efficiency for Pumping Systems

According to the US Department of Energy (DOE), electric motors used in pumping systems consume about 25 percent of the total energy used by the US industry. Electric motors account for more than 50 percent of the energy used in those sectors that rely upon intensive pumping. Though pumps are fundamentally efficient, they can be, and often are, operated inefficiently.

When water pump efficiency is optimized, pumping systems:

  • Decrease emissions of carbon dioxide and other greenhouse gases.
  • Enhance profitability of commercial operations by conserving energy.
  • Ensure fewer repairs are necessary.
  • Lower maintenance expenses as pump components need not work as hard.
  • Make the entire system more reliable.

It’s entirely possible to save 20 to over 40 percent on the energy expenses of operating a water pump. Efficiency is particularly important for pumping systems that must operate around the clock, as is the case for municipal water treatment plants. In cases involving plants transporting water, pump efficiency can mean savings nearing 50 percent of energy costs. In fact, up to 75 percent of operating costs over a pumping system’s lifecycle relate to the energy used.

With any water pump, efficiency can be determined by looking at the point at which the pump performs at its peak. This is known as the best energy point (BEP), and the further the pump is away from the BEP, the more energy it uses to move smaller amounts of water. Pump efficiency also helps ensure a system’s reliability while lowering operating and maintenance costs. Conversely, inefficiency is likely the culprit when there are problems like premature wear, motor failure, and other issues with a water pump. In fact, pump efficiency that’s even 15 percent under optimal levels for wastewater treatment facilities may increase costs by up to 45 percent.

Testing Water Pump Efficiency 

For a water pump, efficiency is essential in large-scale applications, as a seemingly small inefficiency can impact budgets considerably. According to the DOE, water pump efficiency drops 50 to 60 percent, or even lower, before replacing a pump in many larger operations. Meanwhile, companies in industries that rely on pumps often overlook optimizing systems by replacing or repairing components to conserve energy, instead often opting for replacement.

Through the performance of efficiency tests, facilities can determine water pump efficiency and thus make estimates of potential energy savings. This is especially helpful for larger pumps and those that operate continuously for long periods. Instruments can be installed directly into a water pump to achieve a reliable measure of flow rate. Efficiency can also be determined by tools separate from the pump that measure numerous factors that determine water pump efficiency, such as capacity, head, leakage, power absorption, pressure, suction characteristics and vibrations.

Potential savings from water pump efficiency includes looking at: 

  • Total kilowatt-hours consumed annually based upon hours a pump is operational.
  • Kilowatt input measured by tester.
  • Kilowatt-hours used per acre-foot pumped through the system.
  • Estimate of acre-feet pumped through the system annually.
  • The average cost for each kilowatt-hour purchased over a 12-month billing period.
  • The mean cost per each acre-foot that goes through the system.
  • Overall plant efficiency measured as a percentage.
  • Total cost annually for energy expenditure, often not including surcharges or demand charges for running the pump.  

Once testing is completed, corrective actions can be taken. For example, internal leakage due to worn or poorly attuned components can reduce water pump efficiency, as can excessive clearances of pump impellers. These can be resolved by refurbishing or replacing damaged or worn parts like impellers, pump bowls, throat bushings, or wear rings to restore internal clearances. Other aspects affecting efficiency may include deterioration of pipes and valve losses or altering processing requirements and strategies for controlling the water pump. Efficiency testing can often lead to directed pump repairs or even to ensure a new pump works correctly.

With new pumps, the problem could be a small thing like the wrong impeller or something more serious like a poorly machined or incorrectly installed pump. Testing water pumps for efficiency allows utility companies or other large operators to ensure their systems work optimally. It’s recommended that testing for wire-to-water pump efficiency should consider not only the pump’s parameters but also that of the motor. These wire-to-water calculations are conducted so that the system’s efficiency curve falls into the area where it operates best. These parameters help measure the overall efficiency of the pumping system.

Wire-to-Water Pump Efficiency

Wire-to-water pump efficiency essentially measures how efficiently a pump converts electricity from a motor or an engine into electro-mechanical energy. In other words, it measures how well the pump performs against the energy inputs it receives. It’s vital to understand this wire-to-water pump efficiency rating, as these calculations always differ at least somewhat from the charted parameters. Wire-to-water pump efficiency looks at the power inputs the pumping system receives to calculate the wire-to-water pump efficiency for a specific pressure head and flow rate. Operators can then set up different parameters to ascertain when the water pump offers maximum efficiency.

Hayes Pump: Water Pump Efficiency Experts 

Hayes Pump Inc. distributes a wide variety of pumps and pump parts throughout the Northeast. Our factory-trained pump technicians have extensive experience in troubleshooting any rotating equipment, and our company is independently audited to ensure our installations are of the highest quality, exceeding industry standards. Besides sales and installations, we also provide repair services for rotating pumping equipment, either in-house or in the field. To learn more about our capabilities, contact the pump experts at Hayes Pump.

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