Flow Meter
Flow meters are key devices used in the chemical industry to measure the flow or quality of liquid or gas in a pipeline, and are essential for precise process control, safety, quality assurance, cost-effectiveness, and regulatory compliance. These devices work on a variety of principles, including differential pressure (e.g., orifice plates, venturi tubes), electromagnetic (for conductive fluids), ultrasonic (transit time and Doppler), Coriolis force (for direct mass flow), turbine rotation, and heat transfer. The selection of the right flow meter depends on a variety of factors, such as fluid characteristics (corrosiveness, viscosity, conductivity), flow type, accuracy requirements, installation constraints, maintenance requirements, and cost. Typical applications include monitoring raw material feeds, controlling reaction inputs, wastewater discharge, and custody transfer.
| Device type | Classification method | Features | Application scenario |
| Differential pressure flowmeter | Classification by measurement principle | The flow rate is calculated by measuring the pressure difference generated when the fluid flows through a throttling device (such as an orifice plate, nozzle, venturi tube, etc.). The differential pressure flowmeter has a simple structure and high reliability, but requires a throttling device and has a certain pressure loss. | It is widely used in the flow measurement of liquids, gases and steam, such as petroleum, chemical, electric power and other industries. |
| Velocity flowmeter | Classification by measurement principle | The flow rate is calculated by measuring the flow velocity of the fluid. Velocity flowmeters include turbine flowmeters, electromagnetic flowmeters, ultrasonic flowmeters, etc. | It is suitable for the flow measurement of various liquids and gases, especially in situations where high-precision and unobstructed flow measurement are required. |
| Positive displacement flowmeter | Classification by measurement principle | The flow rate is calculated by measuring the volume of the fluid. Positive displacement flowmeters include oval gear flowmeters, swivel flowmeters, piston flowmeters, etc. This type of flowmeter has high accuracy, but has high requirements for the cleanliness of the fluid. | It is suitable for high-precision measurement occasions, such as liquid and gas flow measurement in industries such as petroleum, natural gas, and chemicals. |
| Mass flowmeter | Classification by measurement principle | Directly measures the mass flow rate of the fluid, and is not affected by changes in fluid density, temperature, pressure, etc. Common mass flowmeters include Coriolis mass flowmeters and thermal mass flowmeters. | Applicable to occasions where accurate measurement of mass flow is required, such as chemical, pharmaceutical, food and other industries. |
| Fluid vibration flowmeter | Classification by measurement principle | Calculates flow by measuring the vibration frequency or amplitude caused by the fluid. Common ones include vortex flowmeters and swirl flowmeters. | Applicable to flow measurement of liquids, gases and steam, especially in situations requiring high accuracy and wide range ratio. |
| Pipeline flowmeter | Classified by installation method | Directly installed in the pipeline, in direct contact with the fluid, with high measurement accuracy. | Applicable to flow measurement of various liquids and gases. |
| Insertion flowmeter | Classification by installation method | Measure the flow rate by inserting the probe inside the pipe. It is easy to install, but the accuracy is relatively low. | Suitable for flow measurement of large-diameter pipes, such as sewage treatment, industrial waste gas, etc. |
| Clamp-on flowmeter | Classification by installation method | Measure the flow rate by clamping the sensor on the outside of the pipe. There is no need to cut the pipe, which is easy to install. | Suitable for situations where lossless installation is required, such as ultrasonic flow meters. |
| References | Authors | Abstract | DOI |
| Characteristics and Applications of Ultrasonic Flowmeters | Chen Cong | The working principle of ultrasonic flowmeters is introduced, and the differences between various measurement methods are compared. At the same time, the characteristics of ultrasonic flowmeters and the key points of selection, installation, maintenance and overhaul in engineering applications are briefly discussed. | 10.3969/j.issn.1008-455X.2010.01.012 |
| Discussion on the Applicable Length of Straight Pipe Section of Flow Meter | Xie Lin, Yin Jiayun, Ji Bofeng, Ji Gang | Among the existing flow meters, except for volumetric flow meters and Coriolis mass flow meters, other flow meters have specific requirements for the front and rear straight pipe sections, and the length of straight pipe sections required by different types of flow meters is also very different. The reason why the uncertainty of flow measurement increases when the straight pipe section is not long enough is that when the fluid flows through the elbow or valve, the velocity distribution is distorted, resulting in the actual flow coefficient being inconsistent with the flow coefficient calibrated at the factory. Common countermeasures include: pipeline bypass, which is simple and easy; reducing the accuracy index, which is also often used in ordinary monitoring and process control; choosing the most favorable position for the flow sensor to be installed on the pipeline; installing a flow regulator; choosing a flow meter with a lower requirement for the length of the straight pipe section. At the same time, a comparative analysis of the above countermeasures is carried out. | 10.3969/j.issn.1007-7324.2014.05.015 |
| Problems in the use of flow meters and the countermeasures to be taken | Zheng Canting, Wu Zhaoxi, Ye Zhigang | Through the application examples of flow meters, it is shown that there are many problems in the application of flow meters, some of which are caused by improper selection, some are caused by improper operation, and some are caused by improper installation, maintenance and measures. At the same time, it is proved that even if the flow meter has high accuracy and is very perfect in experimental verification, there are still many problems in actual measurement. | CNKI:SUN:LYHG.0.2008-05-021 |
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