Factors affecting and inaccurate measurement of liquid in pipeline by electromagnetic flowmeter

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  Factors affecting and inaccurate measurement of liquid in pipeline by electromagnetic flowmeter

  Electromagnetic flowmeter is a flowmeter with side volume flow of conductive liquid made by Faraday's law of electromagnetic induction. In the early 1950s, electromagnetic flowmeter realized industrial application. As a kind of industrial flow measuring instrument, electromagnetic flowmeter has many advantages, such as minimal pressure loss; Large measurable flow range; The applicable industrial pipe diameter range is wide, up to 3000mm; The output signal is linear with the measured flow and has high accuracy; It can measure acid, alkali, salt solution, water, sewage, corrosive liquid and mud with conductivity > 5us / cm. Electromagnetic flowmeter is widely used in various fields because of its unique advantages. With the continuous improvement of manufacturing technology and the supporting application of various new digital intelligent systems in products, the measurement medium of electromagnetic flowmeter is also increased and the measurement accuracy is also improved. Whether in the international market or in the domestic industrial application, because the adaptability of electromagnetic flowmeter products is very wide, electromagnetic flowmeter has become a very important instrument type and occupies an irreplaceable position in the industry and market. Today, we will briefly introduce the liquid in three cases where it cannot be measured. I hope you have a deeper understanding of it.

  1、 The liquid in the measuring pipe of electromagnetic flowmeter is not full

  In fact, for most types of measuring instruments, non full pipe measurement will cause inaccurate measurement. For example, due to insufficient back pressure or poor installation position of flow sensor, the liquid in the measuring pipe of electromagnetic flowmeter cannot be filled, and the fault phenomenon has different manifestations due to non filling degree and flow condition. If a small amount of gas flows in stratified or wavy flow in the water pipe, the fault phenomenon is that the error increases, that is, the measured flow value is inconsistent with the actual value; If the flow is bubble flow or plug flow, the fault phenomenon is not only the measured value is inconsistent with the actual value, but also the output shaking due to the instantaneous covering of the electrode surface by the gas phase; If the gas phase part of the flow cross-sectional area increases in the stratified flow of the horizontal pipeline, that is, the degree of liquid under filling the pipe increases, there will also be output shaking. If the liquid under filling the pipe is serious, so that the liquid level is below the electrode, there will be output over filling, resulting in the failure of measurement.

  2、 Measurement of solid phase in liquid by electromagnetic flowmeter

  The liquid contains solids such as powder, particle or fiber, and the possible faults are:; Slurry noise; Contamination of electrode surface; The conductive deposition layer or insulating deposition layer covers the electrode or lining, and the electrode cannot work; The lining is worn or covered with sediment, and the flow cross-sectional area is reduced.

  3、 The measuring medium contains easily crystallized components

  Electromagnetic flowmeter must be used with caution when measuring liquid that may crystallize; Some easily crystallized chemical materials can also be measured by electromagnetic flowmeter when the temperature is normal. However, since the pipes conveying fluid have good heat tracing and insulation, they will not crystallize during insulation work, but the measuring pipe of electromagnetic flow sensor is difficult to implement heat tracing and temperature preservation. Therefore, when the fluid flows through the measuring pipe, it is easy to cause a layer of solid on the inner wall due to cooling. The main function of the lining of the electromagnetic flowmeter is to protect the electrode. The low insulation of the electrode will lead to a variety of phenomena in the flowmeter. The common one is that the flow value displayed by the flowmeter will fluctuate greatly and cannot be stabilized, resulting in a large error, and the measured data has no reference value.