Fluctuations in the indication of the single-flange level gauge
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Atmospheric pressure tank with an open top (normally covered by a lid but without sealing), so a single-flange level gauge is selected. The material in the storage tank is an aqueous solution of surfactant; it is stirred and prone to foaming. The problem is that when the tank indicator shows a certain liquid level, stirring is stopped (feeding or discharging is halted), and after remaining stationary for some time, the liquid level drops by more than about 20 cm. My understanding is that once stirring stops, the amount of material in the storage tank no longer changes; even if foam is present, the pressure transmitted to the single-flange level gauge should not change, which means the level indication should not change either. However, after remaining stationary for a while, the liquid level does drop. How to understand it?
When stirring is in operation, vortices form in the center; at this time, the liquid level around it is higher than that at the center. Once stirring stops, the measured liquid level will represent the actual liquid level (with the level in the center being equal to that around it)
After the motor stops, the vortex does not cease immediately; it takes some time for that to happen
Learn* it a bit. . . . . :handshake
EJA210A-DMSH2D5A-97DN/NF1 is the transmitter model, manufactured by Yokogawa. The actual range is set at around 30 kPa; the rated range could not be found
It can barely be explained as a wave; it usually needs to stay stable for about 20 minutes, which is quite a long time
I have also considered this kind of disturbance; it seems that it takes a rather long time for the liquid level to reach stability, about 20 minutes