Describe application cases of steam vortex flow meters

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　　With the further advancement of energy conservation and emission reduction efforts, as well as the development of centralized heating in cities, centralized heating has reached a considerable scale. Depending on the type of thermal coal used, central heating is divided into hot water heating systems and steam heating systems. Within steam heating systems, steam metering has increasingly become a focal point of concern for both heating companies and users. It serves as the direct basis for determining users’ energy consumption and is closely related to the economic benefits of both users and heating companies; therefore, the accuracy of steam flow measurement is extremely important. The vast majority of steam flow meters in widespread use today are of the derived type. Among them, those based on throttling differential pressure flow meters and vortex flow meters are the most common; both of these methods have their own advantages and disadvantages, yet they complement each other well. The following uses a vortex flow meter as an example to illustrate the management of steam flow meters. 　　1. Working principle of vortex flow meters Since their introduction, vortex flow meters have been increasingly widely used. Currently, when heating companies supply steam to users, approximately 90% of them use vortex flow meters as the primary measuring instrument for steam flow in pipelines with a diameter of 300 mm or less. When a cylinder is inserted into a fluid, regular vortices form alternately on both sides of the cylinder; this sequence of vortices is known as the Karman vortex street. The frequency at which these vortex streets appear is related to the flow velocity of the fluid and the width of the cylinder, with the frequency being proportional to the flow velocity. Therefore, by measuring the frequency of the Karman vortex street, it is possible to determine the flow rate of the fluid. 　　2. Current status of steam metering 　At present, the selection and installation of steam meters are mainly handled by the heating company, which is also responsible for their maintenance. Since the vortex flowmeter, which is the main instrument for steam measurement, has been in use in China for a relatively short time, and the quality of products manufactured domestically varies greatly, there are still some issues associated with steam measurement in practice. 　　(1) Due to the characteristics of vortex flowmeters, problems often arise during their operation, such as signal interference. Once such problems occur, the flow measurement values become inaccurate. Users usually only discover this after some time has passed, which results in losses. It also leads to numerous disputes between the heating supply agencies and users. 　　(2) Problems existing in the maintenance of measuring instruments. Currently, the maintenance of meters is generally handled by the heating companies, which results in centralized management of these meters. Users lack knowledge regarding the use of steam metering devices; they do not know the importance of conducting regular steam analysis, calibration comparisons, and meter verification, which leads to a lack of consistency in steam metering. 　　3. Management measures for steam flow meters (1) Record, analyze, and study the steam consumption on a daily basis; identify the causes promptly when the consumption is abnormal. 　　(2) It is necessary to regularly send the steam flow meters to authorized technical institutions for verification or calibration. 　　(3) Install a comparison gauge behind the main steam gauge, and the flow meter must undergo metrological verification or calibration. 　　(4) Install sub-meters on the steam pipelines for internal measurement and assessment purposes. After installing these sub-meters, it is possible to compare their readings with those of the main meter, as well as to monitor and evaluate the amount of steam saved by each department. It is also possible to close other valves and conduct online comparisons with the main meter’s flow readings, thereby providing effective supervision. 　　Flow metering is one of the components of metrological science and technology, and it is closely related to the national economy, national defense construction, and scientific research. Doing this work well plays an important role in ensuring product quality, improving production efficiency, and promoting the development of science and technology. Especially in today’s era of energy crises and an increasing degree of automation in industrial production, the significance and role of flow meters in the national economy have become even more evident.