Year
2016
Abstract
Instrumentation has been developed at Idaho National Laboratory for continuous monitoring of fluid in a vessel. The instrument utilizes three dip tubes for determining the mass and volume of a liquid in a vessel. The principles of tank calibration and volume determination are currently standardized in ISO18213 Parts 1-6 and utilize two dip tubes to measure density and depth. A weakness in the standards is that the surface tension must be estimated. Poor surface tension estimates lead to inaccurate depth measurements, which introduce error in mass and volume determination. Surface tension is dependent on the fluid composition and temperature. Although literature exists for many pure, binary, and possibly ternary systems, the fluid composition must be known to predict surface tension; furthermore, some complex mixtures may not have adequate data. In a real time setting, the composition may change during chemical reactions and chemical additions; as a result, the real time compositions are difficult to estimate and the corresponding surface tension is likely in error. The measurement of surface tension can mitigate problems associated with surface tension estimation. The maximum bubble pressure method utilized in the above standards may also be applied to surface tension. One of the significant features is the addition of a third dip tube with a different inner radius and at the same depth to measure surface tension. The application of a triple bubbler system can provide continuous mass and volume determinations in fluids of complex mixtures or unknown composition.