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Industry Information
Matters needing attention in the measurement of frozen water by electromagnetic flowmeter
2012-4-13 15:14:06


有明显的优势。 Application in the measurement of chilled water cooling capacity: In the measurement of chilled water flow, electromagnetic flowmeters have obvious advantages. For example: no pressure loss, high accuracy and good stability. However, due to the characteristics of frozen water, some problems should be paid attention to in the use of electromagnetic flow meters. The first is the inner village of the electromagnetic flowmeter. Pay attention to the negative pressure of the memory. When the measurement medium is corrosive, we need to use PTFE memory material. However, the electromagnetic flowmeter using PTFE material cannot withstand negative pressure. There are two ways to solve the problem. The first is to use a memory with a skeleton type. The disadvantage is that it increases investment costs. Second: The original vent valve is changed to a check valve (check valve). When a slight negative pressure occurs in the pipeline, the check valve automatically opens to suck air from the atmosphere, thereby ensuring safety. The above are the matters needing attention in the measurement of frozen water by electromagnetic flowmeter. Another flow meter suitable for chilled water measurement is the time difference ultrasonic flow meter. Some problems should be paid attention to in use. For example: Since the sensor and the cable plug may be wrapped in a thermal insulation layer, in order to prevent condensation from damaging the sensor, the protection rating of the cable plug should be IP68 diving type.


制造技术发展应用:在过去,电磁流量计的校验必需送到专门的标定校验设备上进行检查。 Development and application of electromagnetic flowmeter manufacturing technology: In the past, the calibration of electromagnetic flowmeters must be sent to special calibration and verification equipment for inspection. However, with the development of electromagnetic flowmeter manufacturing technology and the expansion of the application industry, the use of electromagnetic flowmeters is increasing, the caliber is getting larger and larger, and the difficulty of returning to the verification device for verification is becoming more and more difficult. Especially in the water supply industry, due to the large diameter of the pipe and the characteristics of the industry, it is difficult to take out the meter to check the meter and send it out. However, according to the requirements of the ISO9001 quality management system, each enterprise needs to conduct periodic inspections as an electromagnetic flowmeter for measuring instruments. For this reason, the application and manufacturers of electromagnetic flowmeters have been struggling to find an online electromagnetic flowmeter inspection method to replace the traditional offline calibration method. In recent years, the online inspection method of electromagnetic flowmeters at home and abroad is commonly used: the online calibration method of large-caliber electromagnetic flowmeters. In the 1990s, Shanghai Water Systems began to explore online inspection and verification. They used a dedicated analog signal detector to detect the converter, and the sensor inspection was In order to test the liquid resistance of the electrode, check the insulation resistance and copper resistance of the excitation coil including the excitation connection cable, and check the excitation current output by the converter and check the magnetic field strength and other indirect methods. In the pipeline with stop flow condition, enter from the preset hole near the sensor, check the electrode and lining for contamination, deposition and clean. The use of the GS9 in the inspection process is very simple. Just connect it according to the cable identification and the flow meter (plug and play), and then start the automatic verification. The data will be stored in the internal memory (70 instruments), and then the data can be stored. Transfer to a computer for processing. The tester automatically loads the settings of the GK, range, caliber, exciting current, current and frequency output of the meter, and starts measuring the exciting current, detecting the coil and electrode resistance (short circuit or open circuit), checking the signals of the two measuring electrodes, and converting Device current and frequency output check. Give "Pass" or "fail" diagnosis to different parts of the converter and store the entire verification process. The entire process of calibration is automatically controlled and the calibration data is uploaded to the computer through the RS232 communication port. Traceability GS9 can be directly traced to KROHNE's highest-end calibrator (GS100) and (Netherlands Metrology and Testing Institute NMI), the sensor calibration uncertainty is 0.03%, and the GS9 measurement uncertainty is 0.09%. Connect the GS9 to the PC via RS232 at the scene or in the instrument room. Although the above-mentioned online inspection or special diagnostic instrument method is not required to stop the pipeline flow and then test the flowmeter, it still needs the help of external testing equipment to complete the entire inspection. process. Therefore, the development of flow meters with built-in diagnostics and inspection functions is the current development trend of flow meters.

是按照VDI-NAMUR-WIB2650导则的要求进行设计的最新型电磁流量计。 This new type of electromagnetic flowmeter is the latest electromagnetic flowmeter designed according to the requirements of VDI-NAMUR-WIB2650 guidelines. Compared with the conventional electromagnetic flowmeter converter, this type of converter adds many online diagnostic functions, such as: * About the process (conductivity, coil temperature, gas contained in the liquid, flow state); * About Application environment (converter temperature, external magnetic field and installation conditions). It takes a certain time to popularize the online calibration method and the industry recognizes that the online inspection method for electromagnetic flowmeters is becoming more mature from its birth to application, but it will take some time to be promoted in various industries across the country. The biggest difficulty is that the electromagnetic flowmeter is used as a measuring instrument, and its online inspection specifications need to be approved by the national technical supervision department and various relevant industry associations. The above-mentioned schemes and equipment must be cooperated by the manufacturers, users of the electromagnetic flowmeter, and relevant national departments if they are to be approved nationwide. We are glad to see that in the Shanghai water service system where electromagnetic flowmeters are widely used, industry user organizations have joined the technical supervision and manufacturers to complete the industry regulations for online inspection and verification of large-diameter electromagnetic flowmeters and implement them. We look forward to more industries and manufacturers being able to join this technical solution, so that the majority of users of electromagnetic flowmeters can follow the rules.