Yokogawa electromagnetic flowmeter does not return to zero
Thread Content
Our company has an electromagnetic flow meter used to measure aqueous ammonia. On July 4th, the readings from the flow meter showed fluctuations; however, after July 5th, it consistently indicated full scale. Even after the process pipeline was isolated, the reading remained at full scale. The exact cause remains unidentified. Could all experts please analyze what possible issues could be responsible for this? ? ? Thank you
1. Remove the flow meter to clean the electrodes and check whether they are corroded or damaged. 2. Check whether the resistance of the excitation coil is normal. 3. Do the indications on the gauge head match those output to the control system? From this, it can be determined whether the fault lies in the signal processing board or the output board
Thank you! I’ll handle it according to your suggestion. What’s the typical resistance of an excitation coil? Please give me some advice! Thank you!
They vary among different manufacturers; AC and DC models also differ. Please refer to the manual for specifics; it usually contains instructions on troubleshooting as well.
First, check the wiring to see if the output remains at 20mA
Intelligent transmitters come equipped with comprehensive self-diagnosis functions, and the flow meter display shows fault alarm codes in the event of any issues. Or connect the HART communicator to see if there are any alarm messages; the reading remains at full scale. It’s usually a self-diagnosis fault, and sometimes the gauge is forced to output a current greater than 20 Ma or less than 4 Ma.
Yes, for the Yokogawa empty pipe alarm, the full-scale output is 20mA. You can compare this with the alarm codes
It is estimated that the weather is hot, the temperature is high, and the flow meter cannot be installed in a condition where the pipe is always full. Due to high temperatures, ammonia gas escapes from the ammonia water, causing the pipelines to become empty. Choosing a location for the flow meter where it can ensure a full pipe may resolve the issue.