In 2013 LNG mass flow meters were traceably calibrated by the gravimetric primary LNG mass flow standard with an estimated Calibration and Measurement Capability (CMC) of 0.12% to 0.15%. Dominant uncertainty sources included the uncertainty associated with the correction for so-called parasitic forces. Modifications to the primary standard were made with the objective to reduce the measurement uncertainty associated with the parasitic forces. A Level Compensation System (LCS) was installed to control the level of the weighing vessel during the weighing process. Several experiments were performed, and the results analysed. It was demonstrated that the LCS has the potential to reduce the measurement uncertainty associated with the parasitic forces. An alternative method to reduce parasitic forces was made possible by the installation of a drybreak coupling. Future activities will aim to provide a proof of principle of the improvements due to the LCS and the dry-break coupling when using liquid medium (e.g., LNG) in the weighing process.
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