Guest Column | October 10, 2023

What Benefits Do Variable Frequency Drives Offer For Pump Control?

By Emily Newton

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People working with water infrastructure or handling other industrial needs may choose variable frequency drives (VFDs) for better pump control options. This approach relies on a component that alters the frequency and voltage received by the pump motor, thereby changing its speed and torque. Here are some of the benefits of VFDs.

Reduced Maintenance

Prioritizing reliable pump performance means understanding the pressure and flow characteristics of the network, and selecting a correctly sized pump to meet those needs. People must also determine if flow and pressure vary depending on the time of day or season when choosing their pumps.

Besides picking the right pump size, people must perform regular checks to inspect valves and manage the friction losses that can cause reduced pumping pressure. Installing a VFD on a pump is another useful strategy. Doing so can save between 20 and 35% by increasing pump efficiency.1 The outcomes are often particularly impressive in systems with high annual operating hours, as these usually use the most energy and require the most upkeep.

Relatedly, people should strongly consider using a VFD to maximize the pump control options associated with older piping. Although many things can cause leaks in such environments, one common problem is hydraulic stresses may occur, leading to pipe dislocations and wall weakening. However, a VFD can reduce the pressure during periods of lower demand, making the piped infrastructure less likely to fail.

Minimizing Unexpected Problems And Addressing Water Hammer Issues

People can also eliminate water hammer problems, which happen due to sudden flow rate changes. These most commonly occur when a pump starts or stops.

Water hammer issues can cause significant damage to a pump system and pipe infrastructure if not addressed, leading to additional maintenance needs and costs. Individuals often use a VFD to eliminate water hammering because the component allows the pump motor to start and stop gradually.

These examples illustrate some of the specific benefits of variable frequency drives that could help people minimize how much they spend on pump and infrastructure upkeep. The possibilities mentioned here don’t allow individuals to cut corners with maintenance. Still, they can address some of the issues that could result in rising upkeep expenses, so they are well worth consideration.

Energy Savings

People using pumps with variable frequency drives may do so primarily because of the expected energy savings. A VFD can manage wasted power because the power used matches the motor load. Users can often achieve 2.7% in savings for every 1% reduction in VFD output.2 Thus, they’re commonly used in industrial pumping stations, for wastewater aeration systems, or other cases where people want to keep costs low.

The electricity costs associated with municipal water supplies are substantial. Decision-makers should strongly consider performing audits to determine whether their current setups use more or less than expected. The results may show people should try to use specific equipment during off-peak times or that it would pay off for them to become more dependent on renewable energy. Those are viable possibilities.

However, executives must not overlook the pump control options provided by variable frequency drives and how those could conserve energy. VFDs stop pump motors from running at the same speed all the time, wasting energy. They can change motor speeds almost instantly, according to process changes and site demands.

Achieving Energy Savings In Residential Environments

Homeowners can enjoy the benefits of variable frequency drives, too. These components are frequently part of the submersible sump pumps that extract water from basements after flooding. Submersible sump pumps are ideal for these use cases because they’re waterproof and can tolerate liquid originating from above, such as a burst pipe.3

A VFD also brings more consistency to residential environments by maintaining consistent water pressure, regardless of the number of occupants using the supply at any given time. When the variable frequency drive responds to demand fluctuations, users don’t need to worry about unnecessary and costly energy usage.

Sometimes, the people overseeing the water infrastructure for hotels, dorm rooms, and multistory apartment buildings add VFDs to pressure booster pumps, compensating for the times when high demand makes the water mains pressure insufficient. Using the VFDs and pressure booster pumps saves money while providing consistent performance during shifting demands.

Making variable frequency drives part of pump motors used for water infrastructure is a practical way to manage energy consumption. People should consider this approach while deploying other best practices.

Better Visibility

Innovative advancements allow people to see what’s happening with their pumps anytime, even without being near them. Many wastewater professionals use Internet of Things (IoT) sensors to monitor for pressure drops or other potential signs of leaks.4 They can then become more proactive, potentially stopping catastrophic outcomes.

As people research and learn more about the benefits of variable frequency drives, they’ll likely notice more models have connectivity features that let them get real-time performance statistics and change operating modes when necessary. Manufacturers are releasing intelligent controllers, with some featuring remote monitoring capabilities that send data to the cloud for analysis.5

Depending on the model, some may allow a VFD to collect supplemental information, such as temperature or tank levels. The more insights a wastewater manager has, the better equipped they are to respond to emerging situations. Additionally, people can often pull historical data from the VFD, using it to spot gradual changes that could be signs of problems needing immediate investigation.

This improved visibility also saves people time and money by reducing the occasions when technicians must visit physical sites to verify everything is functioning correctly. If the variable frequency drive provides relevant information, people can use those details to reach informed conclusions.

Solving Problems With Variable Speed Drives  

Maintaining wastewater infrastructure requires critical thinking, especially once people notice undesirable performance trends in their systems. People may use IoT-enabled VFDs to ensure previously identified issues don’t return. However, variable frequency drives could also address problems people have uncovered during previous system checks.

Such was the case for people overseeing water-tank servicing associated with Kentucky’s Bowling Green Municipal Utilities. They needed to remove the tank for repainting while maintaining the necessary water pressure in the tank’s zone.

After discussing the specifics, they realized the best approach would be to rely on a water pump station to provision the system directly. However, they knew that option would only suffice if they used controllable pumps that decreased flow rates at times of reduced demand.

The team eventually decided to operate the system with VFDs equipped with failover sensors. This arrangement allowed for a seamless transition while removing and reinstalling the water tank.

The involved parties realized the VFDs addressed a previously identified problem that caused occasional amperage spikes that tripped pump station breakers. The VFDs eliminated that issue and caused up to an 80% reduction in peak-demand usage.5 Leaders also expect the VFDs to prolong equipment life span and minimize unexpected outages, which will have numerous ongoing advantages for the organization.

Getting the Benefits Of Variable Frequency Drives

These are some of the main advantages that lead people to put VFDs on pumps used in wastewater management or for other industrial needs. Individuals considering doing the same should identify the primary goals they want to achieve and the associated budget for the project. Those details will help them determine if using variable frequency drives is the best way to meet the stated objectives.

References

  1. https://www.waterworld.com/wastewater/treatment/article/14181574/optimizing-pumping-systems-in-drinking-water-distribution
  2. https://modernpumpingtoday.com/benefits-of-variable-speed-pumping/
  3. https://www.epumps.com/blog/better-submersible-sump-pump-standing-pump/
  4. https://revolutionized.com/what-is-an-iot-sensor/
  5. https://www.sourcesecurity.com/news/mitsubishi-vfds-give-incredible-rapid-roi-co-9737-ga.1647845834.html

Emily Newton is an industrial journalist. She regularly covers stories for the utilities and energy sectors. Emily is also editor in chief of Revolutionized (revolutionized.com).