Accurate Measurement of Water in Feedwater Heaters

The accurate measurement of liquid levels in power plant operations is key to efficient operation. Although water is a liquid that can be easily measured by numerous measurement technologies, detection in applications like feedwater heaters, for example, takes on a range of complexity that stresses even the most robust devices. Feedwater heaters operate in various ranges depending upon the stage of the process. High-pressure heaters typically operate at 1030 psig @550°F (71 bar @288°C). Further, liquid level transmitters should operate ideally from ambient start-up to operating conditions at full capacity; a wide variation. Torque tube and differential pressure transmitters have been the technologies of choice for many years, each technology having a set of strengths, weaknesses and idiosyncrasies. Performance of both technologies are dependent on the Specific Gravity (SG) of the medium of they are measuring; both suffer inaccuracies when the SG of water varies over temperature. A new level measurement technology, Guided Wave Radar (GWR), has emerged that eliminates the issues that have plagued torque tube and DP transmitters. Guided Wave Radar (GWR) has shown to accurately measure the level of water throughout the changing conditions seen in the life cycles of vessels like feedwater heaters. GWR is a technology based on the speed of light, or more precisely, electromagnetic energy. Inaccuracies due to Specific Gravity (SG) variations are not an issue. In fact, Guided Wave Radar has shown to accurately measure media with wide variations in dielectric.