Methods for dealing with measurement errors of electromagnetic flowmeters

The electromagnetic flowmeter will produce certain measurement errors during use, which will have a certain impact on the user's use. How should we deal with the measurement error problem? The following editor will specifically introduce the method of dealing with the measurement error problem of the electromagnetic flowmeter, hoping to help everyone.

(1) The electromagnetic flowmeter tube is not full of liquid. Due to insufficient back pressure or poor installation position of the flow sensor, the liquid in the measuring tube cannot be filled. The fault phenomenon has different manifestations due to the degree of infilling and flow conditions. If a small amount of gas flows in the water pipe in a stratified flow or wavy flow, the fault phenomenon is manifested as an increase in error, that is, the flow measurement value does not match the actual value; if the flow is a bubble flow or a plug flow, in addition to the measurement value not matching the actual value, the output will also appear due to the gas phase momentarily covering the electrode surface; if the gas phase part of the flow cross-sectional area in the horizontal pipeline stratified flow increases, that is, the degree of liquid not filling the tube increases, and output shaking will also occur. If the liquid is not filling the tube more seriously, so that the liquid level is below the electrode, the output will appear overfull.

(2) The liquid contains solid phase. The liquid contains solids such as powder, particles or fibers. Possible faults include: ① slurry noise; ② electrode surface contamination; ③ conductive deposition layer or insulating deposition layer covering the electrode or lining; ④ the lining is worn or covered by sediment, and the flow cross-sectional area is reduced.

(3) Electromagnetic flowmeters should be used with caution for liquids that may crystallize. Some chemical materials that are prone to crystallization can be measured normally under normal temperature conditions. Since the conduits that convey the fluid have good heat insulation, they will not crystallize during the insulation work. However, it is difficult to implement heat insulation for the measuring tube of the electromagnetic flow sensor. Therefore, when the fluid flows through the measuring tube, it is easy to cause a layer of solid to form on the inner wall due to cooling. Since the crystallization problem also exists when using flowmeters based on other principles, in the absence of other better methods, an "oring" electromagnetic flow sensor with a very short measuring tube length can be selected, and the heat insulation of the upstream pipeline of the flowmeter can be strengthened. In terms of pipeline connection methods, the flow sensor should be easy to disassemble and assemble, so that it can be easily removed for maintenance once crystallization occurs.

(4) Problems caused by improper selection of materials for electrodes and grounding rings. Electromagnetic flowmeters that fail due to material mismatch with the measured medium include electrodes and grounding rings. In addition to corrosion resistance problems, improper matching can also cause surface effects of electrodes. Surface effects include: ① chemical reactions (formation of blunt film on the surface, etc.); ② electrochemical and polarization phenomena (generation of electric potential); ③ catalytic effects (generation of aerosol on the electrode surface, etc.). Grounding rings also have these effects, but the degree of influence is smaller.