Zero-point issue of double-flange level gauges
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A newly installed EJA double-flange level transmitter shows -2.5% when the tank is empty. The same value is obtained when the upper and lower flanges are loosened. After zero adjustment, the gauge reads 0.1%, while the control room display shows 0%. Once the flanges are tightened again, the reading becomes 2%. The process engineers say there is nothing inside the tank and that it has been connected to the atmosphere. Experts, how should this issue be resolved? Thank you!
Is the gauge manual valve open? The diaphragm wasn’t squeezed, was it?
1: Analyze the problem from a phenological perspective – it was 0 before the flange was tightened and 2% after tightening, indicating that the pressure difference detected by the level gauge had changed. Next, analyze the possible reasons for this change in pressure difference, and then verify each one individually. For example, possible reasons include the presence of fluid or pressure inside the tank, or the diaphragm of the transmitter flange being compressed due to misalignment； Since the process specifies no medium, let’s verify this by turning on the drain to release the pressure or vent it ； Is it possible that the diaphragm has been compressed? It can be taken apart for inspection, or the DCS trends can be checked to see when the 2% level increased. Further analysis is needed. As for me, the way to solve problems is through a process of continuous hypothesis testing and verification, followed by summarizing experiences, which over time leads to the development of one’s own methodology
After confirming that there is nothing inside the tank, perform zero-point adjustment again
The gasket is just the right size, so it won’t press on the diaphragm
Thank you for typing so many words; I’ve learned a lot
It’s an empty tank; it hasn’t been put into operation yet. The operator said that it has been vented to the atmosphere, and the pressure gauge next to it also shows 0
It’s possible that during the process of tightening the bolts, the diaphragm was pressed