Differential pressure flowmeter is not suitable for use under a full range of 30%. Why?
When the flow rate is less than 30% of the full scale, the following can be done:The A. process allows for maximum flow reduction and, when the Reynolds number is large enough, it can be solved by changing the orifice size or instrument range.B. uses other types of flowmeters, such as turbines, flowmeters, etc..
Flow measurement is widely used in industrial and agricultural production, national defense construction, scientific research, foreign trade and people's daily life. In the oil industry, from oil exploitation, transportation and refining metallurgical processing and trade sales, flow measurement throughout the whole process, any link cannot do without flow measurement, otherwise the oil industry's normal production and trade will not be guaranteed. In the chemical industry, the inaccurate flow measurement results in the imbalance of the distribution ratio of chemical components, and can not guarantee the quality of products, and serious production safety accidents will happen. In the power industry production, the measurement and adjustment of the flow of liquid, gas, steam and other media occupies an important position. Flow measurement accuracy not only to ensure the power plant under the optimal conditions has great economic significance, but with the development of high temperature and high pressure large capacity unit, flow measurement has become an important link to ensure the safe operation of the power plant. Such as large capacity boiler instantaneous water supply interruption or reduction, may cause serious dry pot or explosion accident. This requires that the flow measurement device should not only make accurate measurement, but also send out an alarm signal in time. In the production of iron and steel industry, the measurement of circulating water and oxygen (or air) in steelmaking process is one of the important parameters to ensure the quality of products. In the light industry, food, textile and other industries, the flow measurement can not be separated.
Flow measurement, the national standard provides: throttling device applicable flow ratio of 30% (minimum flow: maximum flow =1:3). This is because the differential pressure is proportional to the square of the flow rate, and the flow ratio is less than 30%, and the accuracy can not be guaranteed. In addition, when the flow rate is less than 30%, the Reynolds number is often lower than the limit Reynolds number. The coefficient of flow coefficient is not constant, which makes the flow measurement inaccurate.
