Knowledge of the uncertainty of Custody Transfer and Allocation measurement is typically calculated following the published Guidelines & Standards using Manufactures Data. But what if there are environmental issues regarding the Installation or Type of Equipment. This Paper identifies and illustrates ways of using established uncertainty theory as a tool for modelling the design of measurement equipment, the combination of that equipment into flow measurement systems and/or the modelling of complex Plants/Allocation Systems. By using these tools measurement exposure can be expressed in terms of uncertainty, units measured or financial risk, thereby giving an insight into the advantages of one method of measurement over another. In a similar way Design Houses can determine the optimum solution for a measurement system and Operators the most cost effective solution for Plant/Allocation metering. The Paper is subdivided into three main Sections: 1. Instrument Uncertainties -^sExamining the physics of the meter and determining its sensitivity to various aspects of its installation. 2. Meter System Uncertainties -^sExamining the algorithms used to determine flow rate from instruments and using a combination of sensitivity factor and calibration tolerances. 3. Plant & Allocation Systems -^sExamining the connectivity between the individual metering system associated with a Plant/Allocation System and assessing the cumulative uncertainty effect on reported figures.
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