A critical success factor for all power plants is the ability to accurately measure liquid levels throughout the circulating water system. The use of effective power plant instrumentation can greatly enhance the efficiency and safety of your facility.
To achieve accurate level measurement, it is important to understand the application challenges within the primary process flow of a typical power plant. In this post, we will discuss how level control technology can help you accurately and reliably measure the level of critical applications within your circulating water system, including the demineralization tanks, open atmosphere sumps and cooling tower.
Power Plant Instrumentation for Circulating Water System Applications
At the beginning of the process, source water enters the demineralization tank. Because modern high-pressure boilers evaporate several million pounds of water every working hour, the purity of feedwater circulating inside the boiler is essential. Chemical treatment reduces scale-forming materials and corrosive oxygen content. A feedwater evaporator can be used as an alternative method to chemical treatment because it removes impurities by evaporating raw water with extraction steam. Most often, the purity of feedwater is achieved by chemical treatment.
Because support chemicals for water treatment in demineralization tanks can include caustics, sodium hypochloride, sulfuric acid or other additives, individual chemistry and storage requirements will dictate the level instrumentation selected.
A guided wave radar (GWR) or displacer transmitter, such as the Eclipse® Model 706 GWR or E3 Modulevel®, is the most suitable continuous level control technology for a demineralization tank, while float-actuated switches, such as the Magnetrol® Model T52 or T62, can provide the point level control that this application requires.
Open Atmosphere Sumps
Power generating facilities have large, open atmosphere collection basins known as sumps that are usually found in wastewater treatment areas. Often constructed of concrete with depths ranging from four to ten feet, sumps function as collection and treatment sites for waste liquids ranging from storm water runoff to excess make-up water. With many possible uses for sumps, chemical composition and temperatures will vary.
Proper level control will help ensure the continuous operation of collection and processing basins. Level controls in these areas must often tolerate corrosive media, harsh chemicals, liquids with high solids content and punishing weather conditions.
A GWR or non-contact ultrasonic transmitter, such as the Echotel® Model 355, can provide a reliable continuous level control solution for a condensate storage tank. For point level control, displacer-actuated switches, such as the MAGNETROL Model A10 or B10, are recommended.
Open-system cooling towers reject waste heat from the steam cycle by exposing the cooling water directly to the atmosphere. The majority of heat removed is due to evaporation and the remaining cooled water drops into a collection basin. Level control applications include a high level switch to avoid overflow conditions in the cooling tower basin. In a once-through cooling system, the water intake structure is often a vertical wet pit sump, which requires high and low level sensing and possible pump control.
The water infeed and basin levels of the cooling tower require level sensing and control. In frigid climates, a level switch can work in tandem with a resistance heater to protect standing water in the cooling tower basin against freezing.
The most frequently used continuous level control for this application is a GWR transmitter, while displacer-actuated switches, such as the MAGNETROL Model A15 or B10, can provide point level control.
For More Information
To learn more about this topic, you can also download our guide to level instrumentation for power generating plants.