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 @5500F (71 bar @2880C). 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.
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