Electromagnetic flow meters have advantages in measuring the liquid flow rate of conductive media. In recent years, electromagnetic flow meters have been widely used in various industries, and maintenance technicians are increasingly required to master more knowledge about electromagnetic flow meters. Today, the editor will introduce what precautions should be taken when using and installing electromagnetic flow meters?

Installation precautions:

1. Electromagnetic flow meters should be installed on pipelines filled with the measured medium

2. In general measurement situations, the length of the upstream straight pipe section should not be less than 3D, and the length of the downstream straight pipe section should not be less than 2D; in situations where measurement is required, the length of the upstream straight pipe section should not be less than 10D, and the length of the downstream straight pipe section should not be less than 3D

3. When installing a plug-in electromagnetic flowmeter on a horizontal or inclined pipeline, the probe should be installed within a range of 45 ° above and below the centerline plane of the pipeline, as shown in Figure 3.

Figure 3 Installation of electromagnetic flowmeter probe on horizontal pipeline

4. The centerline of the plug-in electromagnetic flowmeter probe should be perpendicular to the centerline of the pipeline.

5. When the measured fluid is not grounded, the electromagnetic flowmeter should be insulated and isolated from the process pipeline, and its power supply and output signal should be isolated by a transformer, as shown in Figure 4.

Figure 4 Electrical connection of ungrounded fluid

When the measured fluid is grounded, the electromagnetic flowmeter body should be well connected and grounded to the process pipeline, as shown in Figure 5.

Figure 5 Electrical Connection of Grounding Fluid

Instructions for Use:

The premise of using an electromagnetic flowmeter is that the measured liquid must be conductive and cannot be lower than the threshold (i.e. lower limit). Conductivity below the threshold will result in measurement errors until it cannot be used. Even if it changes beyond the threshold, it can still be measured with little change in indication error. The threshold of a universal electromagnetic flowmeter is between 10-4 and (5 × 10-6) S/cm, depending on the model. When used, it also depends on the length of the flow signal line and its distributed capacitance between the sensor and the converter. The manufacturer's instruction manual usually specifies the length of the signal line corresponding to the conductivity.

Electromagnetic flow meters can measure corrosive liquids, but in the initial stage of ordering, customers need to provide the correct properties of other measuring media to avoid errors in electrode selection during selection, which may result in the sensor being scrapped during later use, causing inconvenience and economic losses to customers.

Although electromagnetic flow meters have good reliability and are generally not damaged, due to their principle, the sensor electrode surface is always in contact with the liquid, and over time, the electrode surface is more susceptible to contamination. Therefore, in general, for electromagnetic flowmeters, if customers have the conditions to disassemble them, it is recommended to remove and clean the electrodes once every one to one and a half years to ensure the measurement accuracy of the entire flowmeter. Any instrument requires maintenance, and electromagnetic flow meters are no exception.