What are the Problems with Magnetic Flowmeters in the Acetic Acid Industry

It is also known as acetic acid and is used as an acidity regulator, acidifier, pickling agent, flavor enhancer, and spice. It is also an excellent anti-microbial agent, mainly due to its ability to lower the pH below that required for optimum microbial growth. Acetic acid is the earliest and most used acidifier in China and is mainly used in compound sauces, preparation of waxes, canned goods, cheese, jellies, etc.

Therefore, the failure analysis of the BCST self-control electromagnetic flowmeter in the acetic acid application is as follows.

1. Measurement failure with air bubbles in the medium

Two ways of generating bubbly gas in liquids.

1.1 The medium draws in gas from the outside world.

1.2 The dissolved gas in the medium transforms into free bubbles.

If there is a giant bubble in the medium, when the bow through the electrode, the entire electrode is covered so that the flow signal input loop instantaneous open circuit so that the output signal will appear fluctuations.

Integral Magnetic flowmeter

When we determine the cause of this fluctuation, you can do so. The magnetic field circuit current is cut off if the flow meter still shows and is in the fluctuation state, proving the existence of bubbles in the medium will cause electromagnetic flow meter fluctuations. Using a pointer multi-meter to measure the electrode resistance of the electromagnetic flowmeter will find that the circuit resistance of the electrode of the electromagnetic flowmeter is higher than the average resistance value.

If the air causes the electromagnetic flowmeter installation position into the measured medium, if due to the installation of the electromagnetic flowmeter in the high point of the pipe system and storage of gas, or due to external inhalation of air caused by fluctuations in the flow meter, it is necessary to replace the electromagnetic flowmeter installation position modified in the pipeline z low point installation or the use of U-shaped pipe installation.

But some cases, due to the electromagnetic flowmeter caliber being more extensive or the installation of the location is not easy to change, and we can take in the flow meter upstream installation of gas collection package and exhaust valve to solve this situation.

2. Medium that is not a full tube

In everyday production, we also experience the phenomenon of non-full tubes. This phenomenon can be seen as a typical liquid containing air bubbles. When the electrode level is below the liquid level of the medium, it is ideal to use a straight pipe section before and after the flow meter, and the measurement data is more stable.

But the gas volume in the upper part of the tube is also calculated into the medium flow, so this situation has a larger measurement error; when the electrode level is higher than the medium liquid surface, the electromagnetic flowmeter measurement circuit is in the open-circuit state, the measured data is seriously distorted. Therefore, to deal with this medium is not full tube generated by the fault can have the following approach: as far as possible in the bottom-up flow of vertical pipeline installation.

3. Installation of electromagnetic flowmeters

An electromagnetic flowmeter in actual production needs to be installed horizontally. In this case, it should be installed at the z-low end of the pipe, and the electrode axis of the electromagnetic flowmeter will be paralleled to the horizon to avoid negative pressure in the measurement tube. The flow meter sensor should be installed downstream of the pump, upstream of the control valve; the flow meter installation port should have specific backpressure and be far from the direct discharge port.

installation for flowmete

4. Electrode of electromagnetic flowmeter is corroded

The electromagnetic flowmeter will come into contact with some solid corrosive media in acetic acid production. When the electrode material of the electromagnetic flowmeter is not selected correctly, the medium will corrode the electrodes of the flow meter and eventually lead to sensor failure. Therefore there will be flow meter output fluctuations. When a flow meter failure occurs after the electrodes have been eroded, We can only find out that the electrode material is not resistant to corrosion. This material itself has performance problems that cannot be identified before use. Therefore only a new electrode to solve such failure. So the electrode corrosion fault judgment processing belongs to the maintenance after the fact processing method.

Electrode of electromagnetic flowmeter 

5. Measurement faults due to the nature of the liquid to be measured.

If the measured medium conductivity is reduced, the output impedance of the electrode will increase. As a result, the flow meter will produce measurement errors when the converter input impedance causes a load effect. If the electromagnetic flowmeter this fault is the only choice to meet the low conductivity electromagnetic flowmeter requirements, or use other flowmeter principles such as orifice plate flow meter.

6. Deformation of the flow meter lining causes measurement fluctuations.

Electromagnetic flowmeter lining is generally used fluorine plastic so that the flow meter lining is effortless to deform, the phenomenon of metering failure.

There are two main reasons for the deformation of the lining.

6.1 First, a fluorine plastic lining penetration into the steam thermal diffusion phenomenon, usually the lining material, thickness, temperature difference between inside and outside, the type of fluid and steam, pipeline pressure, and many other factors determine the degree of penetration.

6.2  Secondly, it depends on the fluorine plastic lining material. Generally, PTFE is used as fluorine plastic lining material. PTFE material is without bonding force only by pressure paste and pipe wall combination, so the negative pressure pipeline does not use this material.

Deformation of the flow meter lining

7. Interference from external electromagnetism.

There are stray pipeline currents, static electricity in the production site. Electromagnetic flowmeter flow signal is minimal, elementary to be external electromagnetic interference, and affects the electromagnetic flowmeter’s everyday work. The so-called electric field interference means that the flow meter measuring potential tube balance is destroyed by noise after the output signal fluctuation is abnormal.

8. Conclusion

Many acetic acid installations use flow measurement instruments such as vortex and oval gear flowmeters. These flowmeters have many shortcomings: easy to wear, by the medium after corrosion leakage, short life, maintenance workload, and it is challenging to meet the production requirements with the technological change of the device using a new electromagnetic flow meter instead of the design of the flow meter. This change meets the needs of the acetic acid production process and reduces the investment and maintenance intensity to a large extent.

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