Why does the tank level display in DCS often jump to the full scale?
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The servo level gauges are used for the storage tanks on site; the medium stored in these tanks is white oil and aromatics, under normal temperature and pressure conditions. The control room uses a DCS system from Zhejiang Zhongkong. Currently, the liquid level readings for many storage tanks often jump to the full scale for periods ranging from a few seconds to several dozen seconds, before returning to normal (the actual liquid levels in these tanks are normal). This phenomenon occurs whether the tanks are being filled or emptied, and the intervals between such occurrences are irregular – sometimes it happens every few minutes, other times every few hours, or even after several days or weeks. Does anyone know what could be causing this? The servo meter has also been replaced, and the cables have been reconnected
As for this matter, analyzing the reasons is just guessing; it’s completely useless. Spend some money to upgrade the power supply and use a purified power source – that’s the way to go.
Check the grounding of the DCS cabinet and the cable shielding layers, and measure the grounding resistance. Also, determine whether the power supply for the level gauge is 220VAC or 24VDC, and check that as well.
If nothing else works, try adding an isolator
1 Is the level gauge cable placed in the same tray as the electrical power cable? 2 Is the signal cable of the level gauge shielded with single-ended grounding? 3 Where is the power supply for the level gauge coming from, and what is the quality of that power? All these issues need to be confirmed
Which company makes the servo level gauge? Are there any pictures?
Is there a barrier? Based on what you said, it should be caused by interference. Servo level gauges rely mainly on inductance. It is not very resistant to electromagnetic and leakage interference. More checks are still needed. If nothing else works, filtering has to be done in the configuration.
This kind of issue is a problem with the DCS itself; the software needs to be upgraded
This post was last edited by hfrs on 2018-12-21 at 11:18. Who told you to use servos? It costs a lot of money and also causes a lot of hassle; for dome tanks or floating roof tanks, it’s better to use steel belts.
Is the key issue the power supply? Changing it is useless; it’s really just wasting money. .
So what should the ground resistance be less than in ohms?