Liquid level signal correction system and method

Abstract

A system and method for correcting a measured liquid level signal from a bypass chamber comprises calculating a density error correction to modify the liquid level signal and indicate a correct liquid level corresponding to the level of liquid inside of a vessel to which the bypass chamber is in fluid communication.

1 . A liquid level signal correction system, comprising:
 a vessel for containing liquid and saturated steam;   a bypass chamber configured to be in fluid communication with the vessel, liquid and saturated steam;   a level transmitter for measuring a level of the liquid in the bypass chamber and generating a bypass level signal;   a first temperature sensor for measuring a temperature of the saturated steam and generating a steam temperature signal, and a second temperature sensor for measuring a temperature of the liquid and generating a liquid temperature signal;   a signal modifier configured to receive the bypass level signal, steam temperature signal and liquid temperature signal, and to calculate a density error correction based on the steam temperature signal and liquid temperature signal to modify the bypass level signal to indicate a correct liquid level corresponding to the level of the liquid inside the vessel.   
     
     
         2 . The system of  claim 1 , wherein the signal modifier calculates the density error correction by calculating a density of the liquid and a density of the saturated steam based on the liquid temperature signal and the saturated steam temperature signal. 
     
     
         3 . The system of  claim 1 , wherein the signal modifier is further configured to output the correct liquid level for feedwater control. 
     
     
         4 . The system of  claim 1 , wherein the signal modifier is further configured to output the correct liquid level for display. 
     
     
         5 . The system of  claim 1 , further comprising a plurality of the second temperature sensors distributed along different locations in the bypass chamber for generating multiple measured liquid temperature signals, and wherein the signal modifier calculates an average of the liquid temperature signals for use in calculating the density error correction. 
     
     
         6 . A method for correcting a measured liquid level signal from a bypass chamber comprises;
 measuring a level of liquid in a bypass chamber and generating a bypass level signal;   measuring a temperature of saturated steam in a vessel and generating a steam temperature signal;   measuring a temperature of a liquid in the vessel and generating a liquid temperature signal;   sending the bypass level signal, steam temperature signal and liquid temperature signal to a signal modifier; and   using the signal modifier to calculate a density error correction based on the received steam temperature signal and liquid temperature signal to modify the bypass level signal to indicate a correct liquid level corresponding to the level of the liquid inside the vessel.   
     
     
         7 . The method of  claim 6 , further comprising using the signal modifier to calculate the density error correction by first calculating a density of the liquid and a density of the saturated steam based on the liquid temperature signal and the saturated steam temperature signal. 
     
     
         8 . The method of  claim 6 , further comprising outputting the correct liquid level from the signal modifier and using it for feedwater control. 
     
     
         9 . The method of  claim 6 , further comprising outputting the correct liquid level from the signal modifier for visual display. 
     
     
         10 . The method of  claim 6 , further comprising taking multiple temperature measurements of the liquid in the vessel to generate multiple measured liquid temperature signals, sending the multiple measured liquid temperature signals to the signal modifier, and using the signal modifier to calculate an average of the liquid temperature signals for use in calculating the density error correction.