The maximum filling rates recommended by IEC and NFPA for conductive intermediate bulk containers (IBC) conflict with each other and take no account of the filling pipe diameter. A model previously developed to predict maximum liquid surface potentials in medium tanks was re-derived using analytical approximation rather than curve fitting techniques and modified for application to conductive containers. Physically consistent flow rate limits are given for all sizes of container. Relative to the 25 kV hazardous potential threshold, IEC's flow velocity limit of 2 m/s theoretically provides a large safety factor for IBC filling that increases linearly from 2 to 5 as the inside diameter of the filling pipe decreases from 78 to 27 mm. However, because potential varies with the inverse cube of pipe diameter, the safety factor provided by NFPA's flow rate limit of 225 L/min diminishes from 8 to 1/2 over the same range and surface potentials exceed 25 kV for filling pipe diameters below about 35 mm. The model is extended to address elevated dielectric constants and practical guidance is provided for different filling pipe options. We also warn of specific practices that could increase the likelihood of a fire or explosion.

中文翻译：

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容器灌装的静电危害

IEC 和 NFPA 推荐的用于导电中间散装容器 (IBC) 的最大填充率相互冲突，且未考虑填充管直径。先前开发的用于预测中型储罐中最大液面电位的模型是使用解析近似而不是曲线拟合技术重新推导出来的，并进行了修改以应用于导电容器。所有尺寸的容器都给出了物理上一致的流速限制。相对于 25 kV 危险电位阈值，IEC 的 2 m/s 流速限制理论上为 IBC 填充提供了很大的安全系数，随着填充管内径从 78 毫米减小到 27 毫米，该系数从 2 线性增加到 5。然而，由于电位随管径的倒数立方而变化，NFPA'提供的安全系数 在相同的范围内，225 L/min 的流速限制从 8 减小到 1/2，并且对于直径低于约 35 mm 的填充管，表面电位超过 25 kV。该模型被扩展以解决介电常数升高的问题，并为不同的填充管选项提供了实用指导。我们还警告可能会增加火灾或爆炸可能性的具体做法。