Electromagnetic flowmeter as an indispensable and important measurement tool in industrial production, its accuracy and stability is directly related to production efficiency and product quality. However, in practice, electromagnetic flowmeter zero inaccuracy problems occur from time to time, which not only affects the accuracy of flow measurement, but also may cause unnecessary trouble to the production process. In this paper, we will discuss the causes of electromagnetic flowmeter zero inaccuracy, and put forward a series of effective solutions, designed to help industry to solve this problem.
First of all, we need to clarify the specific performance of the electromagnetic flowmeter zero point is not allowed. Usually, when the electromagnetic flowmeter in the absence of flow through, its display value is not zero, or zero value in a short period of time to change significantly, can be regarded as the zero point is not allowed. This phenomenon may be caused by a variety of factors, including but not limited to the following:
1. bubble impact: mixed in the fluid bubble will interfere with the normal measurement of electromagnetic flowmeter, resulting in zero drift. The presence of bubbles will change the conductivity of the fluid, thereby affecting the distribution of the electromagnetic field, so that the measured value deviates from the actual value.
2. Non-full state: when the measurement of the fluid in the pipe is not full of pipe, electromagnetic flowmeter will also be due to poor contact between the fluid and the electrode and produce zero error. Non-full pipe state may be caused by improper pipe design, insufficient fluid pressure or flow rate is too small and other factors.
3. low flow rate: when the flow rate is too low, the relative motion between the fluid and the electrode is weakened, resulting in a weaker electromagnetic induction signal, thus affecting the measurement accuracy. In addition, a low flow rate may also cause impurities in the fluid to be deposited on the electrode surface, further affecting the measurement.
4. Changes in fluid properties: Changes in fluid temperature, density, viscosity and other physical properties will also affect the measurement accuracy of the electromagnetic flowmeter. For example, when the fluid temperature increases, its conductivity may change, resulting in zero drift.
5. Coil insulation problems: Poor coil insulation in electromagnetic flowmeters can lead to measurement errors. Insulation problems may be caused by factors such as aging, moisture or damage to the coil.
6. Lining deformation: The lining of electromagnetic flowmeter may be deformed due to abrasion, corrosion or high temperature in long-term use, thus affecting the measurement accuracy.
7. Electrode Pollution or Wear: Pollution or wear of the electrode surface will affect the electromagnetic field, resulting in the measured value does not match the actual value. Pollution may be caused by impurities in the fluid, grease, etc., while wear and tear may be caused by factors such as long-term use or fluid washout.
8. sensor damage or aging: sensor is the core component of the electromagnetic flowmeter, and its performance directly affects the measurement accuracy. Sensor damage or aging may lead to increased measurement error, or even can not work properly.
9. improper installation position: electromagnetic flowmeter installation position has a great impact on the measurement accuracy. If the installation position is not appropriate, such as tilt angle is too large, close to the electromagnetic interference source, etc., may lead to measurement errors.
10. Bad grounding: the correct grounding of the electromagnetic flowmeter is essential to eliminate electromagnetic interference. If the grounding is poor, it may lead to electromagnetic interference affecting the measurement accuracy.
For the above reasons, we can take the following measures to solve the problem of electromagnetic flowmeter zero inaccuracy:
1. Elimination of air bubbles: Eliminate air bubbles by increasing the operating pressure or installing a gas-liquid separator before the measuring equipment. At the same time, you can also optimise the pipeline design to reduce the generation of air bubbles.
2. Ensure full tube condition: Change the process conditions to ensure that the measuring tube is always full of fluid. Where appropriate, the EPD electrode can be opened to improve fluid contact with the electrode.
3. Improve flow rate: Try to open the valves on both sides of the boundary to improve the flow rate and ensure sufficient relative motion between the fluid and the electrodes.
4. Monitor Fluid Properties: Regularly monitor the physical properties of the fluid, such as temperature, density, viscosity, etc., in order to detect and adjust the measurement parameters in time.
5. Check coil insulation: Use insulated equipment to measure the voltage of the sensor, taking care to disconnect the electronics before performing the measurement. If insulation problems are detected, the coil should be replaced promptly.
6. Replacement of the lining: If deformation of the lining is found, it should be replaced with a new one in time to ensure measurement accuracy.
7. Clean the electrodes: Clean the electrodes regularly to prevent them from scaling and affecting measurement accuracy. It can be cleaned with appropriate cleaners or solvents.
8. Check and replace the sensor: Check the performance of the sensor regularly, and replace it promptly if it is found to be damaged or aged. Also, higher performance sensors can be considered to improve measurement accuracy.
9. Optimise the installation position: Install the electromagnetic flowmeter according to the installation requirements to ensure that it is installed horizontally on the pipeline (pipeline tilt within 50 degrees), and the flowmeter line should be concentric with the pipeline axis, the same flow direction. At the same time, it should be far away from electromagnetic interference sources to ensure measurement accuracy.
10. Improve grounding: Ensure that the electromagnetic flowmeter is properly grounded to eliminate electromagnetic interference. You can use a special grounding device or grounding wire for grounding.
In addition to the above measures, we can also take the following methods to further improve the measurement accuracy of the electromagnetic flowmeter:
1. Periodic calibration: Periodically calibrate the electromagnetic flowmeter to ensure its measurement accuracy. The calibration can be carried out on site or with special calibration equipment.
2. Parameter Adjustment: Adjust the parameters of the converter according to the fluid properties and measurement requirements to obtain accurate measurement values. For example, parameters such as zero point, range, damping time, etc. can be adjusted to optimise measurement performance.
3. Adoption of intelligent technology: with the development of intelligent technology, more and more electromagnetic flowmeter began to adopt intelligent technology to improve measurement accuracy and stability. For example, measurement data can be processed and analysed by intelligent algorithms to eliminate errors and improve measurement accuracy.
4. Strengthen the maintenance management: Regular maintenance and repair of the electromagnetic flowmeter can extend its service life and improve the measurement accuracy. For example, electrodes can be cleaned regularly, coil insulation checked, and damaged parts replaced.
5. Training of operators: Strengthening the training and management of operators can improve their understanding and use of electromagnetic flowmeters. Through training, operators can better master the operation methods and precautions of electromagnetic flowmeter, thus reducing the occurrence of misoperation and failure.
In summary, the problem of inaccurate zero point of electromagnetic flowmeter can be solved by a variety of measures. In practical application, we need to choose the appropriate solution according to the specific situation, and adjust and optimise with the actual situation. Through continuous efforts and practice, we can further improve the measurement accuracy and stability of electromagnetic flowmeter, to provide a strong guarantee for the smooth progress of industrial production.
Hangzhou Economic Development Area，Hangzhou 310018，China
