Abstract A new 3-ton balance weighing system was designed and built up for a high level mass-time primary standard of natural gas up to 60 bar in CVB. The system is composed of a 3-ton electromagnetic balance, two tanks with thermal isolation, two platforms, two roller guide rails and two big weights which are used for special test. To achieve a lower uncertainty and the security application in natural gas measurement, several special methods were used in the system. Firstly, the tanks and platforms can be moved together steadily on the roller guide rail to be connected with pipeline system or to be weighted by the balance which also reduces the pipeline length between tanks and pipeline system. Secondly, the substitute weighing method is used for high accurate weighing. Finally, the whole system is located in a thermal isolated room with temperature and humidity controlling. Technical details, performance tests, uncertainty analysis and the future improvement ideas of the balance system are presented in the paper. The uncertainty analysis shows that the mass measurement uncertainty of gas can achieve less than 1.0g and the maximum relative standard uncertainty of natural gas mass measurement would be no more than 0.022%.

中文翻译：

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一种天平称重系统在 60 bar 以下天然气一级标准中的应用和不确定度分析

摘要 针对CVB中高达60 bar的天然气的高水平质量时间一级标准，设计并建立了一种新的3吨天平称重系统。该系统由一台3吨电磁天平、两个隔热罐、两个平台、两个滚轮导轨和两个用于特殊试验的大砝码组成。为了在天然气测量中实现较低的不确定性和安全应用，系统中使用了几种特殊方法。首先，罐体和平台可以在滚轮导轨上平稳地一起移动，与管道系统连接或通过天平称重，也减少了罐体与管道系统之间的管道长度。其次，采用代称称量法进行高精度称量。最后，整个系统位于一个具有温度和湿度控制的隔热房间内。文中介绍了平衡系统的技术细节、性能测试、不确定性分析以及未来的改进思路。不确定度分析表明，气体质量测量不确定度可达到1.0g以下，天然气质量测量的最大相对标准不确定度不超过0.022%。