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Introduction to the method of improving the accuracy of the plug-in electromagnetic flowmeter

Flow measurement is one of the work items that are widely concerned by people in various industries. Since the flow is a dynamic quantity, coupled with the measured flow, it often has multiple manifestations. Due to the engineering conditions, the operating conditions of the flowmeter are also different, which brings serious challenges to the measurement accuracy of the flowmeter. . As one of the most widely used flowmeters, the electromagnetic flowmeter is supported by the current technical conditions. On the basis of its own qualification, there will still be certain measurement errors. In order to reduce this error in practice and improve the accuracy of the electromagnetic flowmeter, this paper analyzes the following.

1. Accurate selection of electromagnetic flowmeter; firstly, it is necessary to realize a reasonable choice of the sensor diameter of the plug-in electromagnetic flowmeter: the choice of this index will have a decisive influence on the flow velocity of the fluid in the pipeline, and also the output potential The parameters have a significant impact. Therefore, in the process of selecting the electromagnetic flowmeter, it is not necessary to use the diameter of the connecting process pipe as a selection index, but should be selected according to the actual use flow rate. Generally, in the case where the fluid flow velocity inside the pipe to be installed is in the range of 1.5 to 3.0 m/s, the diameter of the sensor needs to be consistent with the diameter of the pipe to be installed, and the fluid flow velocity inside the pipe is <0.5 m/s. Underneath, it is necessary to control the gauge diameter below the pipe diameter.

Secondly, in order to adapt to the measurement conditions of different media, such as the temperature, pressure, corrosivity and wear of the fluid medium, different linings and electrode materials should be used. If it is prone to wear resistance, it is recommended to choose a urethane rubber material. If it tends to have corrosion resistance, it tends to choose a PTFE material.

2. Reasonable installation of electromagnetic flowmeter
First of all, from the point of view of the installation piping requirements, the flow velocity distribution in the electrode plane state has begun to show a certain difference with the data at the initial calibration. In this process, the most important indicator of the particular flow velocity distribution is the level of configuration of the pipe connections upstream of the sensor. If there are problems and defects in the installation of the pipeline, the electromagnetic flowmeter may have a significant amount of displacement problem during its normal use. At the same time, from the point of view of practical engineering application, the installation of the straight section of the front and rear sections of the sensor needs to ensure that the flow velocity can be completely symmetrically distributed under the reference of the central axis, which is to ensure the accuracy of the operation of the electromagnetic flowmeter. Important value. At the same time, it is worth noting that the accuracy of the electromagnetic flowmeter may also be affected by the conductivity level of the conductive fluid in the measuring tube. In order to eliminate the adverse effect of this factor on the accuracy of the electromagnetic flowmeter, the measures to be taken are: if it is required by the engineering practice operating conditions, other types of media need to be added inside the pipeline installed with the electromagnetic flowmeter, then the medium corresponds Joining work needs to be done in the downstream section of the electromagnetic flowmeter installation. If it is affected by objective factors and needs to add media upstream, it is necessary to increase the separation distance between the injection area and the installation area of the electromagnetic flowmeter (the basic control requirement is ≥ 50* measuring tube inner diameter). In this way, ensure the new medium. With the addition, the fluid flows through the electromagnetic flowmeter more evenly and smoothly.

Secondly, during the installation of the plug-in electromagnetic flowmeter, it is necessary to ensure that the inside of the flowmeter measuring tube is filled with flowing fluid. The main basis is: in the process of measuring the internal flow level of the electromagnetic flowmeter, the main factors obtained include the cross-sectional area of the motor and the flow velocity of the motor plane. The product of the above two indicators is the final of the electromagnetic flowmeter. The measured value displayed. Therefore, the electromagnetic flowmeter measuring tube can ensure the accuracy and reliability of the acquired data only in the overflow state. In the process of installing the electromagnetic flowmeter horizontally, the flowmeter needs to be placed at the bottom of the pipe. On this basis, in the case of gas-liquid mixing or solid-liquid mixing, in addition to the installation in the above manner, it is necessary to place the flowmeter in an inclined posture to avoid separation of gas or solid in the mixed fluid. , affecting the accuracy of the measurement.

Again, it is necessary to do the work of grounding and liquid picking during the installation of the electromagnetic flowmeter. During the application of the electromagnetic flowmeter to measure the fluid flow velocity inside the pipeline, the voltage difference level between the sensor output signal and the electrode is in an equal state. Therefore, in order to ensure smooth and reliable operation of the flowmeter, it is necessary to set a reference point of zero potential as a reference. Therefore, in this process, the core of the liquid handling process is: reference point reference for grounding the conductive liquid inside the pipe to zero potential; and the core of the grounding process is to avoid interference of the electromagnetic flowmeter during the measurement of the fluid flow rate. Influence and reasonable safety protection of the electromagnetic flowmeter. At the same time, the grounding treatment can effectively suppress the noise voltage that may be induced by electrostatic induction and electromagnetic induction, and eliminate the interference to the measurement data. Through the control of the grounding resistance level, the level of the stray current voltage drop of the circuit is significantly reduced, and the method of reducing the common mode interference voltage is achieved, thereby achieving the purpose of consolidating the measurement accuracy of the electromagnetic flowmeter.

Finally, in the installation process of the plug-in electromagnetic flowmeter, it is necessary to maximize the distance of the installation area to the magnetic source or the vibration source, and improve the accuracy of the measurement by means of the ground connection. With the support of current technical conditions, it is recommended to control the resistance value of the electromagnetic flowmeter in the grounded state. Especially for electromagnetic flowmeters with explosion-proof requirements and lightning protection requirements, the resistance value control standard under grounding conditions shall be

In addition to the selection and quality control measures for installation, it has an important impact on improving the accuracy of the electromagnetic flowmeter. In the later maintenance and management of the electromagnetic flowmeter, it is necessary to do a good job in preventing and controlling the electrode contamination of the electromagnetic flowmeter. The contaminated area is cleaned and treated. At the same time, the grounding resistance value is measured by a special person to ensure that the electromagnetic flowmeter can operate reliably and efficiently within the safe range and obtain accurate measurement parameters.

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