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差压式孔板流量计目前仍是我国进行天然气流量计量的主导流量计,截至2004年7月长庆气田应用该型流量计总量近300套。SY/T6143-1996“天然气流量的标准孔板计量方法”标准中认为,天然气流量测量不确定度主要由3个方面引起：流量计算方程描述流动状态真实性的不确定因素;被测介质实际物理性质的不确定度因素;测量中重要设备的不确定度因素。为此,文章从以上3个方面对差压式孔板流量计进行了不确定度研究和实验,包括流出系数、孔板技术指标的变化对天然气流量的影响,可膨胀系数、二次仪表的不确定度、天然气组分变化、天然气含水对天然气流量的影响,并就这些误差因素分别从节流装置的选择、脉动流的改善、规范各项规章制度、建立量值溯源体系等方面提出了建议。

ERROR SOURCE AND CONTROL MEASURES OF PRESSURE DIFFERENTIAL ORIFICE METER 1)

Pressure differential orifice meters are still the main flow meters of gas flow measurement in China now. By July of 2004, about total 300 sets of the flow meters were used in Changqing gas field. The standard SY/T6143 1996 of "Normal orifice measuring method of gas flow" indicates the uncertainty of gas flow measurement is caused by the following 3 factors: The reality of flowing performance described by the flow calculating formula is uncertain; the real physical property of the measured medium is uncertain; the main measuring device is uncertain. Aiming to the above 3 issues, the study and experiments of uncertainty are conducted for pressure differential orifice meters including the outflow coefficient; the influence of orifice specification changing on the flow; the expandable coefficient; the uncertainty of secondary instrument; the component changing of natural gas; and the influence of water bearing gas on the flow. Also, according to the reasons causing errors, suggestions are proposed separately on throttle device selecting; fluctuating flow improving; different regulations and systems specifying; and system of measured data backing the source, etc.