Problems with the liquid level gauge can occur in three ways: high, low or unstable indications.
First of all, check whether the liquid level meter is leaking, pass an air source into the positive pressure chamber and block the negative pressure chamber to see if there is any air leakage. The high indication is generally due to a leak in the negative pressure chamber, which increases the differential pressure; the low indication is due to a leak in the positive pressure chamber, which decreases the differential pressure, or is caused by a blockage in the pipeline, which prevents the pressure from being transferred to the positive pressure chamber. The reason for the unstable liquid level may be the leakage of air from the pipeline, or the packing at the two ends of the glass tube seal is not tight.
In addition, when the positive and negative pressure difference is particularly large, the pressure difference exceeds the rated value of the liquid level meter, the working liquid in the cylinder is forced upward into the negative pressure chamber, at this time the working liquid and gas mixture is easy to blow into the glass tube, resulting in the glass tube inclusions of air bubbles. At this point, the valve of the positive pressure chamber inlet should be closed, and then repeatedly opened and closed several times to drive out the air bubbles.
