Abstract In the last decade significant progress has been achieved in the development of measurement traceability for LNG inline metering technologies such as Coriolis and ultrasonic flow meters. In 2019, the world's first LNG research and calibration facility has been realised thus enabling calibration and performance testing of small and mid-scale LNG flow meters under realistic cryogenic conditions at a maximum flow rate of 200 m3/h and provisional mass flow measurement uncertainty of 0.30% (k = 2) using liquid nitrogen as the calibration fluid. This facility enabled, for the first time, an extensive test programme of LNG flow meters under cryogenic conditions to be carried out to achieve three main objectives; the first is to reduce the onsite flow measurement uncertainty for small and mid-scale LNG applications to meet a target measurement uncertainty of 0.50% (k = 2), the second is to systematically assess the impact of upstream flow disturbances and meter insulation on meter performance and the third is to assess transferability of meter calibrations with water at ambient conditions to cryogenic conditions. SI-traceable flow calibration results from testing six LNG flow meters (four Coriolis and two ultrasonic, see acknowledgment section) with water in a water calibration facility and liquid nitrogen (LIN) in the LNG research and calibration facility under various test conditions are fully described in this paper. Water and LIN calibration data were compared and it was observed that the influence of removing the meter insulation on mass flow rate measurement accuracy can be more significant (meter error > ±0.50%) than the influence of many typical upstream disturbances when the meter is preceded by a straight piping length equal to twenty pipe diameters (20D) with no additional flow conditioning devices, in particular for ultrasonic meters. The results indicate that the correction models used to transfer the water calibration to cryogenic conditions (using LIN) can potentially result in mass flow rate measurement errors below ±0.5%, however, the correction models are specific to the meter type and manufacturer. This work shows that the target measurement uncertainty of 0.50% can be achieved if the expanded standard error of the mean value measured by the meter is smaller than 0.40% (k = 2). It is planned to repeat these tests with LNG in order to compare the results with the LIN tests presented in this paper. This may reveal that testing with an explosion safe and environmentally friendly fluid such as LIN produces representative results for testing LNG flow meters.

中文翻译：

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流动扰动对工业标准 LNG 流量计性能的影响

摘要 在过去十年中，LNG 在线计量技术（如科里奥利和超声波流量计）的测量可追溯性的发展取得了重大进展。2019 年，全球首个 LNG 研究校准设施建成，从而实现了在最大流量 200 m3/h 和临时质量流量测量不确定度的真实低温条件下对中小型 LNG 流量计的校准和性能测试。 0.30% (k = 2) 使用液氮作为校准流体。该设施首次实现了低温条件下 LNG 流量计的广泛测试计划，以实现三个主要目标：一是降低中小型 LNG 应用的现场流量测量不确定度，以满足 0.50% (k = 2) 的目标测量不确定度，二是系统评估上游流量扰动和仪表绝缘对仪表的影响。第三是评估仪表校准在环境条件下到低温条件下的水的可转移性。完整描述了在各种测试条件下使用水校准设施中的水和 LNG 研究和校准设施中的液氮 (LIN) 测试六个 LNG 流量计（四个科里奥利和两个超声波，见确认部分）的 SI 可追溯流量校准结果在本文中。对水和 LIN 校准数据进行了比较，发现去除仪表绝缘对质量流量测量精度的影响可能比仪表前置时许多典型上游干扰的影响更显着（仪表误差 > ±0.50%）直管长度等于 20 个管径 (20D)，无需额外的流量调节装置，尤其是超声波仪表。结果表明，用于将水校准转移到低温条件（使用 LIN）的校正模型可能会导致质量流量测量误差低于 ±0.5%，但是，校正模型特定于仪表类型和制造商。这项工作表明，目标测量不确定度为 0。如果仪表测量的平均值的扩展标准误差小于 0.40%（k = 2），则可以达到 50%。计划用 LNG 重复这些测试，以便将结果与本文中介绍的 LIN 测试进行比较。这可能表明，使用防爆和环保流体（例如 LIN）进行测试会产生用于测试 LNG 流量计的代表性结果。