The remote signal from the magnetic flap level gauge fluctuates, and an alarm is triggered suddenly at full scale – what could be the cause?
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Range: 11 meters. Medium: methanol. The issue is indicated by the red trend line in the diagram; from time to time, fluctuations of varying degrees occur, with no regular pattern, and these fluctuations can reach up to the full range. During monitoring in the control room and on-site, there were no fluctuations in the current signal; the current signal in the control room was 7.55 mA, while it was 7.52 mA on-site. It is initially suspected to be electromagnetic interference, but no specific cause for the interference can be identified.
Methanol vaporizes easily, and it is not ruled out that vaporization causes fluctuations in the float
1. The remote signal cable is damaged; check its insulation； 2. Loose connection of signal line ； 3. Has water entered the electrical panel? 4. Check whether there is any fluctuation during feeding; if so, control the feeding speed to see if the problem persists. It’s also possible that the magnetism of the magnetic level gauge has weakened
Similar problems often occur when the liquid level remains within the same range for an extended period, caused by poor contact due to wear of the reed inside the reed switch. To verify this, disconnect the transmitter and move a magnet slowly across the current liquid level range to check whether the resistance changes uniformly; if there are several instances of sudden resistance changes, it is recommended to replace the reed switch. If the resistance remains stable across multiple tests, the resistance transmitter can be replaced. Additionally, for stable measurement, it is recommended to use differential pressure level gauges, as they have a longer service life and provide more stable readings compared to magnetic flap level gauges.
There is a high possibility of a transmitter failure
The operating conditions are unknown, and the installation method is also unknown; how can it be analyzed? It shouldn’t be a single segment – check the issues with that segment
Check whether there is frost on the inner wall of the level gauge float, or any obstacles that prevent the float from moving freely, thus hindering its up and down movement.
It’s possible that the remote transmission rod has aged over time, resulting in poor contact in some of the circuits. The 11-meter tank is quite long; it would be better to use a radar level gauge, as it is stable and easy to install. If the remote transmission system for this 11-meter tank breaks down, it will also be difficult to disassemble it
Is the period of fluctuation related to temperature, as methanol vaporizes easily?
This situation is only meaningful when measured during fluctuations; I think the reed switch should be taken out for inspection.
1. If the display on the panel also fluctuates, it indicates that the float is moving; this phenomenon occurs when the medium is prone to vaporization. 2. If there is electromagnetic interference at the installation site, the remote transmitter can be removed and tested separately, away from that location. 3. It could be a problem with the module, resulting in unstable performance. The level transmitters produced by our company are subjected to at least 24 hours of aging before being shipped.