Electromagnetic flowmeter as a high-precision, highly reliable flow measurement instrument, in industrial production has been widely used. However, its use is not without limitations, understanding and following these limitations is essential to ensure accurate measurement and long-term stable operation of electromagnetic flowmeter. The following is a detailed discussion of the use of electromagnetic flowmeter restrictions.
First of all, electromagnetic flowmeter can only measure the flow of conductive liquids, which is determined by its measurement principle - Faraday's law of electromagnetic induction. Therefore, for non-conductive liquids, such as gases, vapours, oils (especially non-conductive oils), electromagnetic flowmeters are unable to measure effectively. This limitation makes the electromagnetic flowmeter may not be useful in specific application scenarios, and other types of flowmeter need to be selected as an alternative.
Secondly, the pipe diameter range of electromagnetic flowmeter is usually 2mm to 3000mm, although this range has been able to meet the measurement needs of most industrial pipelines, but in some special cases, such as the measurement of small-diameter pipelines (less than 2mm) or large-diameter pipelines (more than 3000mm), electromagnetic flowmeter may face challenges. For small-diameter pipelines, the measurement accuracy of electromagnetic flowmeter may be affected due to the limitation of pipeline size; while for large-diameter pipelines, the installation and maintenance of electromagnetic flowmeter may become relatively difficult due to the huge size of the pipeline, and even need to use special installation methods and maintenance means.
In addition, the temperature and pressure range of the electromagnetic flowmeter also has certain limitations. Typically, the temperature range of the electromagnetic flowmeter is between -25 ℃ and 200 ℃, the pressure range is between 0.6 MPa and 4.0 MPa. For high-temperature, high-pressure liquids, such as steam, hot oil, etc., you need to choose a special electromagnetic flowmeter or take appropriate protective measures to ensure the accuracy and safety of the measurement. This limitation requires users to use electromagnetic flowmeter, must be based on the temperature and pressure characteristics of the measured medium, select the appropriate models and specifications.
In addition to the above mentioned limitations, the measurement accuracy of electromagnetic flowmeter is also affected by a variety of factors. Although the measurement accuracy of the electromagnetic flowmeter is usually ± 0.5% to ± 1.0%, which can meet most of the requirements of industrial production, but in some occasions with high accuracy requirements, such as metering, trade settlement, etc., it is necessary to select a high-precision electromagnetic flowmeter or take the corresponding calibration measures. In addition, the measurement accuracy and stability of the electromagnetic flowmeter is also affected by the nature of the fluid, such as fluid conductivity, viscosity, temperature, pressure, etc.. Therefore, when selecting the electromagnetic flowmeter, you need to choose the appropriate model and specifications according to the nature of the fluid to ensure the accuracy and stability of the measurement.
In the installation and use of electromagnetic flowmeter, you also need to pay attention to the following constraints:
1. Electromagnetic flowmeter installation requirements are more stringent, you need to ensure that the sensor and the pipe concentricity, verticality and horizontality, as well as the distance between the sensor and the pipeline and so on. In the installation process, it is necessary to operate in accordance with the manufacturer's installation instructions to ensure the quality of installation. If the installation is not appropriate, it may lead to increased measurement error, sensor damage and other problems.
2. Electromagnetic flowmeter needs regular maintenance and repair, such as cleaning the sensor, checking the cable connection, calibrating the instrument, etc.. In the maintenance process, the same need to follow the manufacturer's maintenance instructions to ensure the normal operation of the instrument. If the maintenance is not appropriate, it may lead to a decline in measurement accuracy, instrument failure and other problems.
3. Electromagnetic flowmeter is susceptible to electromagnetic field interference. In the installation and use of electromagnetic flowmeter, you need to avoid the presence of strong electromagnetic fields around the equipment, such as transformers, motors, welding machines and so on. If it can not be avoided, you need to take appropriate shielding measures to reduce the impact of electromagnetic fields on the electromagnetic flowmeter measurement.
4. Electromagnetic flowmeter installation location also has certain requirements. For example, the need to meet the front straight section of 5D (D is the nominal diameter of the pipe), after the straight section of 3D requirements; to avoid its installation in the highest part of the pipeline to prevent gas accumulation affects the measurement; if installed in the insulated pipe, must be equipped with grounding ring or grounding electrode, and so on. These requirements are to ensure that the electromagnetic flowmeter can be accurately measured and stable operation.
5. in the measurement of different conductivity of the media, electromagnetic flowmeter should be installed in the media upstream or the media fully mixed position. This is because the different conductivity of the media mixed, may affect the measurement accuracy of the electromagnetic flowmeter. At the same time, for easy adhesion, deposition, scaling of the fluid, electromagnetic flowmeter of the actual flow rate should not be less than 2m / s, preferably 3 ~ 4m / s or more, in order to reduce the adhesion of the fluid on the sensor and clogging. For abrasive fluids, the common flow rate of electromagnetic flowmeter should be less than 2~3m/s, in order to extend the service life of the sensor.
In summary, there are a variety of restrictions on the use of electromagnetic flowmeter. Understanding and following these restrictions is essential to ensure accurate measurement and long-term stable operation of electromagnetic flowmeter. In practical application, users need to select the appropriate electromagnetic flowmeter model and specifications according to the characteristics of the measured medium, measurement requirements and installation environment and other factors, and operate and maintain in accordance with the manufacturer's installation and maintenance instructions. At the same time, we also need to pay attention to avoid the interference of electromagnetic fields, select the appropriate installation location and take appropriate protective measures to ensure that the electromagnetic flowmeter can play the best performance and provide users with reliable measurement data.
Hangzhou Economic Development Area，Hangzhou 310018，China
