Centrifugal Pumps

By Quintus Potgieter

Centrifugal pumps are used in many different industries. Most notably, the pumps are used in water supply operations for both municipal and industrial areas around the world. They are also used in the event of floods for land drainage. Further uses include wastewater management and irrigation applications. The Titanic even used four gunmetal centrifugal pumps that circulated water through the ship’s condensers in their cooling system. The cooled water,  a practice that is still performed on cruise ships. The oil and gas industry also make use of centrifugal pumps. General Electric use multistage split-case centrifugal pumps that deal with crude oil transfer, seawater disposal, and water injection. The pumps are instrumental in those and other industrial operations. The fact of the matter is that centrifugal pumps are essential to key fluid transport systems engineers work with. However, there is one more novel application of centrifugal pumps that many people don’t know exists. It has to do with renewable energy.

When a centrifugal pump is run in reverse it can act as a turbine. More specifically, the centrifugal pump, with the right equipment, could act as a hydroelectric turbine. A collection of these pumps in operated in reverse can be used to create mini-hydro plants that, in the past, have reached up to 500kW of energy per unit. Dubbed ‘pump-as-turbine’ (PATs), the pump running backward is coupled up with the pump’s induction motor that then becomes an induction generator, which, in turn, produces electricity. The energy output of the newly-formed turbine is actually higher than the input.

According to experts, running the centrifugal pumps backward is a cost-effective method of generating power, even more so, than the conventional turbine. Paul N. Garay, a professional engineer, wrote an article titled Using Pumps as Hydroturbines. He writes: “A primary advantage of using a PAT instead of a hydro-turbine is the potential cost savings. Due to a large number of standard pumps produced, a standardized pump converted to a turbine can be significantly less expensive than a specifically designed hydraulic turbine.” A hydraulic turbine extracts energy from the water it is in, whereas a pump adds, even more, energy to the water that is passing through its impeller.

In a world where energy policies require companies to work with more renewable energy-producing technologies, the centrifugal pump could - in the near future - be seeing more uses than it already does. However, turning the pumps into turbines opens them up to higher volumes and forces. A higher level of flow is needed to reach the turbine effect, which means the pump could be damaged at some point. Nonetheless, if the pump is able to handle the high volume of water, it is able to produce more energy. To divide the load, a host of pumps acting as turbines are connected in a system. Adding more pumps to control water volume might be a costly endeavor, however. This has made engineers question the viability for centrifugal pumps as turbines.

However, some engineers point to the cost-effectiveness of using the centrifugal pumps as water turbines in developing countries. A pump manufacturing company named KSB Aktiengesellschaft has installed their own line of pumps in Brazil.  In a small village, a water pump known as the Meganorm 200-250 water pump, is used in reverse to create a pump-as-turbine system. The company says the systems would make good hydropower stations for “remote communities”.

To learn more about centrifugal pumps, EIT offers the Professional Certificate of Competency in Centrifugal Pumps and their Mechanical Shaft Sealing Selection, Optimizing, Performance and Troubleshooting course.

The twelve module course, conducted over a three-month period will delve further into the different types of centrifugal pumps and focus on key applications in modern day engineering. The course also goes into the environmental considerations relating to centrifugal pumps as well. Pump efficiency is also a focus of the curriculum, and could further influence a group of students to further investigate how to turn a solitary pump into an efficient, clean energy-producing turbine.

Works Cited
"Feature." Pumps as Turbines in the Water Industry. Web. 23 Aug. 2016.
Palgrave, Ron. Troubleshooting Centrifugal Pumps and Their Systems. Oxford: Elsevier Advanced Technology, 2003. Print.
Sulzer Centrifugal Pump Handbook: Sulzer Pumps. Oxford: Elsevier, 1998. Print.