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Industry Information
Knowledge about DX-plug-in flowmeter
2011-10-8 16:32:10

这些年 来流 量计的应用 逐年 提升,特别是在大管道的测量 ,优势更是 比较的显著 With the continuous development of modern industry, the application of flowmeters has been improved year by year , especially in the measurement of large pipelines . The advantages are even more significant . 使用 插入式流量计 时需 要注意两个因素。 There are two factors to be aware of when using a plug-in flowmeter . 阿牛巴流量计 为例, 公司 相关技术人员在参考大量资料的前提下,对阿牛巴流量计本身经过很深的研究, 以下为 现场主要影响阿牛巴流量计的两个重要 因素 The following takes Annubar flowmeter as an example. The relevant technical personnel of our company have conducted a deep research on the Annubar flowmeter itself with reference to a large amount of information. Important factors :
1 . 长度 Length of straight pipe section
很多 用户来说,不算陌生。 Plug-in flow meters are not unfamiliar to many users. 阿牛巴流量计是一种插入式仪表,它只能 通过 测管道中直径方向几点的流速来推算流量, 因此 具有取样的性质。 The plug- in Annubar flowmeter is a plug-in meter. It can only estimate the flow rate by measuring the flow velocity in the diameter direction of the pipe, so it has the nature of sampling. 精确度高,而直管段又不能达到设计 要求 那么 管道内的流速分布不可能成为对称于轴线的同心圆,仅 仅通过 测直径方向几点流速 不能充分反映整个截面的流速分布 ,因此,必须 对流速 分布有 严格要求 If the required accuracy is high, and the straight pipe section cannot meet the design requirements , then the velocity distribution in the pipeline cannot become a concentric circle symmetrical to the axis. Simply measuring the velocity in the diameter direction cannot fully reflect the entire section. Velocity distribution , therefore, must have strict requirements on the velocity distribution . 具有15 - 25 管内径的长度,这样才能充分 发展紊流,才有可能用几 流速反映整个截面的流速分布 The straight pipe section should have a length of 15-25 times the inner diameter of the pipe, so that turbulent flow can be fully developed, and it is possible to use several points of flow velocity to reflect the flow velocity distribution of the entire section . 均速管多用于大管径, 现场一般难以保证这么长的直管段 因此精确度难以提高 Because averaging pipes are mostly used for large pipe diameters, it is generally difficult to ensure such a long straight pipe section on site , so it is difficult to improve the accuracy . 只要流动是定常流, 也就是 流速分布是稳定的,不 随时间变化 But as long as the flow is steady, that is, the velocity distribution is stable and does not change with time . 流速虽然精确度差,但 重复性还是较好的。 Although only a few points of flow velocity are poor in accuracy, the repeatability is still good.
2 . 内径 Inside diameter of the pipe
计算 认为管内径D 是精确的, 但是 实际上并 不是 如此 The above calculations assume that the tube inner diameter D is accurate, but this is not the case . 很少有用户认真精确测量管内径。 In general, few users carefully and accurately measure the inner diameter of the tube. 没有办 法测 内径 情况下,也 可以 允许根据管道外周长, 根据 壁厚确定管内径, 但是 这样确定的内径当然难以准确。 According to the international standard IS07145 , when there is no way to measure the inner diameter , it is also allowed to determine the inner diameter of the pipe based on the outer circumference of the pipe and the wall thickness, but of course it is difficult to determine the inner diameter accurately. ,同时 还要考虑管道内壁的腐蚀、积垢、凝析物等因素 In addition , factors such as corrosion, fouling, and condensate on the inner wall of the pipeline must also be considered . 内径有1 2mm 的误差 也许有时用户习以为常,但是 它对流量的影响却不可忽视。 While the internal diameter may have an error of 1-2 mm , sometimes users are accustomed to it, but its effect on the flow cannot be ignored.
的同时, 也许很容易理解插入式的安装方法 就是间接的把面测量转换成点测量 然后再通过理论的转换管道流量 While understanding the principle of the plug-in flowmeter , it may be easy to understand the plug-in installation method , which is to indirectly convert the surface measurement to the point measurement , and then theoretically convert the pipe flow . 以上两个参数的重要性就可想而知的了 Therefore , the importance of the above two parameters can be imagined .