Electromagnetic flowmeter measurement of beer when to pay attention to the relevant matters

　　Domestic enterprises' investment in automation control is much weaker than that of foreign enterprises. Take a beer brand that ranks among the top three in China in terms of annual output as an example. One of its production bases has a daily beer design capacity of 5,000 m3 (annual output of more than 200,000 m3) and uses only more than 30 electromagnetic flow meters (referring to those directly used in the beer production process, without involving other auxiliary processes). However, the technical level of its equipment still lags behind that of its international counterparts.

　　For example, after the reconstruction of Japan's Kirin Beer Yokohama Factory in 2000, the annual beer production can reach 500,000 m3, and nearly 500 electromagnetic flowmeters are used. From the above data, we can see how big the gap is between the automation level of my country's beer industry and that of foreign companies. For all kinds of instruments needed for current production and future expansion and development, we should comprehensively and comprehensively consider the particularity of the industry and the specific requirements of the use, maintenance and production process of different instruments, and select them correctly. This is an extremely important work content to ensure product quality and the correct and safe operation of the instrument body, which will bring great benefits to future practical work.

　　The flow measurement of materials and products in the production process of the beer industry is valued by many companies, especially the liquid flow measurement instruments used, which are different from those of general companies and have their own special requirements. For example, the reproduction of bacteria must be avoided, frequent cleaning must be convenient, and disinfection with corrosive alkaline water and hydrogen peroxide must be withstood at high temperatures. The specific requirements are as follows: the sensor measurement circuit is simple, without flow obstructions and parts that are prone to media retention; all materials of parts in contact with the media meet the requirements of food hygiene, such as the requirements of the FDA (U.S. Food and Drug Administration) and EHEDG (European Hygienic Equipment Design Group); parts in contact with the media can withstand temperature shock and corrosion during cleaning with steam, alkaline water and hydrogen peroxide.

　　When used in the filling process, it must have fast response performance and high measurement accuracy, and be able to adapt to low temperature (around 2e) and humid working environment. Among many liquid flow meter products, electromagnetic flowmeter can meet the above requirements, and its price is decreasing day by day, so it is recognized by the majority of users in the beer industry, and thus occupies a large proportion in practical applications. This article combines some examples encountered by the author in daily work to discuss the application of electromagnetic flowmeter in the beer industry, such as selection, operation and daily maintenance.

　　Principle of electromagnetic flowmeter The basic principle of electromagnetic flowmeter is Faraday's law of electromagnetic induction. A moving conductor cuts magnetic lines of force in a magnetic field, generating induced electromotive force at both ends. As shown in Figure 1, in a non-magnetic measuring tube with an inner diameter of D and an internal magnetic field strength of B, a liquid conductive medium flows at a speed of v, and an induced potential U proportional to the flow rate is generated in a direction perpendicular to the flow direction. The magnitude of the potential is as follows: U=BvD(1) Where: B is the magnetic induction intensity, T; v is the average flow velocity of the fluid, m/s; D is the inner diameter of the measuring tube. The volume flow rate of the liquid is qv=14PD2v(2) which is very important and sensitive, and accuracy is its primary indicator.

　　Wort has a certain viscosity, but there is no difficulty in measuring it with an electromagnetic flowmeter. What needs to be considered is the disinfection during the process. The flowmeter used at this measurement point can be an electromagnetic flowmeter with a PTFE lining (or PFA) and stainless steel electrodes. It can prevent corrosion from dilute hydrogen peroxide and alkaline water. The diameter is usually between 50 and 100 mm. The diameter of the flowmeter can be determined based on the flow rate and the matching process pipeline. Fermentation: The fermented and filtered sake will be transported to the next process) through a pipeline for packaging, which also involves the measurement handover between the two departments. It is also extremely important to accurately measure the sake, otherwise it will cause unnecessary disputes.

　　The requirements for flowmeters are similar to those for wort metering. High-concentration dilution: Due to different production processes, some beers are produced by blending high-concentration original juice wine. This requires strict control of the ratio of high-concentration original juice wine and sterile carbonated water to ensure the beer degree after mixing. In each production line, two electromagnetic flowmeters are required to control the proportioning flow. Generally, the flowmeter for measuring wine is selected with a caliber of 50~100mm, and the flowmeter for measuring water is selected with a caliber of 20~50mm, depending on the production scale. In order to ensure that the instrument has a high measurement accuracy, the fluid flow rate should be guaranteed to be above 1m/s, so that the flow measurement is within the optimal working range of the instrument. At the same time, the time constant of the flowmeter should also be set smaller, generally 1~3s, to improve the sensitivity of the control and ensure the accuracy of the ratio.

　　Filling: Filling is the last step of beer production, in which filling requires accurate control of the filling volume of each bottle (can, barrel) (the industry standard is ?10ml). As for glass bottled beer, which accounts for the vast majority of the market, most domestic manufacturers currently use equal liquid level filling. This process has low equipment manufacturing costs and low investment. Most domestic beer companies use this method, but there is a problem of large errors. Due to the discreteness of beer bottle production, the volume difference is large, resulting in a large error in the final amount of beer filled. According to the situation in production practice, it can be as large as ?30ml! If you want to reduce this error, using a batch control electromagnetic flowmeter designed specifically for filling production lines can effectively solve this problem. This type of flowmeter has high accuracy and fast response performance, and can quickly and accurately control the filling volume of each bottle of beer.

　　Usually, this type of electromagnetic flowmeter has a small caliber, generally between DN2.5 and DN40, with a compact size and a response speed of 0.3s. At present, there are products available on the market, such as Krohne's BatchFlux, Heinrichs' MID-NFD, etc. This electromagnetic flowmeter, which is dedicated to batch control, has a small batch processing capacity of 10ml (for a 10mm caliber meter), and the actual control accuracy is very high (up to ?0.2%). However, the filling equipment commonly used by domestic beer companies currently rarely uses this type of electromagnetic flowmeter. Only on imported beer production lines have such meters imported with equipment been seen. The main reason is that the error in the filling volume of beer will not immediately affect the beer production; second, the equipment currently used is low in cost and can meet the production needs.

　　However, with the expansion of the application of PET to replace glass bottle filling technology, this type of equipment equipped with batch control electromagnetic flowmeters will inevitably replace the current equal liquid level filling equipment. Wastewater treatment: There is some wastewater generated by bottle washing and can brushing in the beer production process. According to environmental protection requirements, it must be effectively treated before discharge. This relatively small wastewater treatment system in the beer industry has matured. There are many options for flowmeters used in the intermediate treatment process and discharge, such as electromagnetic flowmeters and open channel flowmeters. However, from the feedback of user applications, it is more appropriate to use electromagnetic flowmeters. Although the price is more expensive than open channel flowmeters, its reliability during operation is higher.

　　The electromagnetic flowmeters for various purposes mentioned above have various pipe connection methods. For example, the electromagnetic flowmeters used in wastewater treatment processes are connected by flanges, and most of the flowmeters used in other processes are also connected by flanges, but there are also quick connection methods that are unique to the food and pharmaceutical industries. This type of quick connection structure is usually used in places where it needs to be disassembled frequently. From the actual domestic use situation, many users generally do not disassemble the flowmeter frequently after reasonably designing the installation location of the process, so there is no need to invest more in this aspect. Flange connection methods account for the majority, and quick connection structures sometimes have the disadvantage of easy leakage. For example, domestic buckles may be deformed and unable to lock after several uses.