1) When the liquid level instrument value reaches the highest or lowest, it shall be judged according to the field test instrument. If the field instrument is normal, the system shall be changed to manual control to check whether the liquid level changes. If the liquid level can remain stable within a certain range, it indicates that there is a problem in the liquid level control system; otherwise, it is due to technological reasons.

2) For the differential pressure level instrument, when the display data of the control instrument is inconsistent with that of the field test instrument, and there is no obvious abnormality in the field instrument, check whether the liquid seal of the pressure guide pipe is normal. If there is leakage, add the sealing liquid, and the instrument returns to zero; If there is no leakage, it is preliminarily inferred that the negative migration of the instrument is wrong, which needs to be corrected.

3) When the data of the liquid level control instrument fluctuates abnormally, it should be judged according to the equipment capacity. If the equipment capacity is large, it is usually the instrument that has problems; If the equipment capacity is small, it is necessary to check the process operation first. If the process operation changes, it is most likely to be the fluctuation caused by process reasons, and otherwise, it is the problem of the instrument.