A Liquid Level Testing Method for Working Fluids Near Critical State Based on Three Differential-Pressure Transducers

Abstract

The online detection of leak for liquefied gas storage tanks needs high-precision liquid level measuring methods, while the traditional ones cannot meet the measurement demand for the working fluid near its critical state. A precise level measurement device based on three differential-pressure transducers was put forward, and the comprehensive relative uncertainty of the device with different component parameters was analyzed. It can be concluded that the height difference in the pressure tap, the accuracy of the differential-pressure transducer in the gas section, and a testing times more than 10 has little effect on the measurement accuracy. The accuracy and resolution of the ordinary A/D converter can meet the requirements of the testing. It is better to apply the equipment within the measuring range of 80%∼100%. The density ratio does not affect the accuracy with a density ratio greater than 16. When the density ratio is constant, the working fluid property has no influence on the measuring precision. By applying the proposed method, the uncertainty of level measurement for near-critical medium is within 0.4%.