双向大量程比蒸汽流量计的工程实践

ENGINEERING PRACTICE OF BIDIRECTIONAL LARGE RANGE RATIO STEAM FLOWMETER

介绍使用双向标准孔板实现双向蒸汽流量测量的基本原理。定量计算分析流出系数、可膨胀性系数以及测量不确定度与流量的关系,并讨论制约标准孔板流量计提高量程比的几个主要因素。通过定量计算对比单一大量程变送器和一大一小双量程变送器对不确定度的影响,论证增加1台小量程变送器用于小流量测量、以达到30∶1量程比的技术方案的可行性。介绍应用HART总线降低项目投资的技术方案。论述流量计设计和选型以及施工中应特别关注的几个因素和细节。

Basic principles of bidirectional steam flow measurement using bidirectional standard orifice was introduced.The relationship between discharge coefficient,expansibility coefficient,measurement uncertainty and flow was quantitatively calculated and analyzed.Several main factors restricting the raise of range ratio of standard orifice flowmeter were discussed.Through quantitative calculation and comparison of the influence of single large range transmitter and large and small double range transmitter on the uncertainty,the feasibility of adding a small range transmitter for small flow measurement to reach 30∶1 range ratio was demonstrated.The technical scheme of reducing project investment by using HART was described.Several factors and details that should be paid special attention to in flowmeter design and selection as well as construction were discussed.