Installation issues with ABB split-type electromagnetic flowmeters
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There is some current flow at the site; the pipes are made of PVC, but no grounding ring is used. According to the model, no grounding electrode is provided either – only one grounding wire leads from the enclosure to a common ground point. Is such an installation reliable?
It depends on the operating conditions of the medium and the pipeline. Generally, electromagnetic flowmeters installed on non-metallic pipes should be equipped with grounding electrodes or grounding rings to ensure that the flowmeter has a reliable zero potential area for measurement. When the pipe is made of a non-metallic material and the conductivity of the fluid is not very good, or when there is no proper grounding at the zero potential level, the measurement values can experience significant fluctuations or even make accurate measurements impossible. Check the operating and installation instructions for electromagnetic flowmeters, and follow the specified requirements.
The medium is water and the pipes are made of PVC. At first I thought it had a grounding electrode, so connecting only the enclosure to ground would be sufficient; that makes sense. But according to the model specifications, no grounding electrode is provided. The manual specifies stricter requirements for grounding, stating that a separate grounding connection is necessary. Yet the system still operates properly – I don’t understand this
It’s no problem if the medium is water. For corrosive environments, a grounding ring still needs to be considered!
Generally speaking, non-metallic pipes require the installation of grounding rings in order to balance the charge distribution within the medium. Since the electrical signal generated by electromagnetic flowmeters is relatively weak, and imbalances in the movement of charges within the medium can easily cause interference, the result is that the flow rate keeps fluctuating. But if the medium is water and the operating conditions are not too severe, the interference caused by the charge in the medium should not be very strong, enough to disrupt the electrical signal of the electromagnetic flowmeter; as a result, the flow rate remains stable. In that case, it doesn’t really matter whether a grounding ring is used or not. This is my personal opinion; please correct me if I’m wrong.