Experience | Common faults of external liquid level gauges and their solutions

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The three most common faults of external-type level gauges at present: the instrument displays LO (fault code LO)； The instrument displays movement “—” (fault code YD) ； The gauge shows a deviation in the liquid level (fault code XP). These three types of failures account for over 85% of all failures in level gauges. 1. The main reason for the “LO display” caused by the external level gauge: Increased sedimentation in tank A ； Treatment method: Clean the tank ； If the tank cannot be emptied, it is necessary to find a new location for installing the probe; generally, there is less sediment near the discharge outlet at the bottom of the tank. Silicone oil loss in probe B ； Solution: Reinstall the probe. C: Hardware failure of the instrument; Solution: Contact the customer service of the instrument manufacturer, who will decide whether to replace the component or send it back to the manufacturer for repair. Impact during material inlet and outlet in D, loss of level signal. Solution: Change the probe’s installation location, keeping it away from the inlet and outlet. 2. Main reasons for the “deviation XP” caused by external level gauges: A. Calibration issues 1) Low-level calibration is installed unconditionally, while the conditions for high-level calibration are not met ； Solution: If the feed level exceeds the calibrable height, modify user parameter 6# by referring to the reference liquid level. 2) Calibration failed; the instrument is not calibrated ； Solution: Raise the liquid level above the calibrable high level, and check whether the 6# user parameter is within the valid range. If there is no change, it indicates a problem with the instrument calibration; in such cases, contact the manufacturer’s customer service. 3) The calibration signal is poor. Solution: Reinstall the calibration probe. 4) The measured liquid level is inaccurate. Solution: Verify that the zero point of the comparison liquid level is consistent with that of the external level gauge; if not, adjust parameter 5# of the user. B shows a doubled level reading; the doubling is particularly severe when feeding an empty tank or when the liquid level is low, and the instrument sometimes does not reset automatically ； Solution: When the liquid level exceeds the instrument’s blind zone, force a reset of the instrument. C sphere tank deviations are widespread ； Treatment method: Feed liquid so that the liquid level is above the calibration height to achieve automatic calibration. Impact during D inlet and outlet; sometimes the liquid level fluctuates or remains unchanged. Solution: Find a new location for installing the probe, away from the inlet and outlet. 3. The main reasons for “display movement - YD” caused by external level gauges: A. Shock during material inlet and outlet, resulting in loss of the level signal ； Solution: Find a new location for installing the probe, away from the inlet and outlet. B: Hardware damage, mainly on board 0# and board 2# ； Solution: Notify the manufacturer’s customer service, and let them decide whether to replace the component or send it back to the manufacturer for repair. Conditions under which C installs the steering gear, with the steering gear coming loose ； Treatment method: 1) Clean and open the tank, then enter it to re-weld the steering gear ； 2) It is not possible to enter the tank; locate a suitable spot for installing the probe at the bottom of the tank, and check whether there is a suitable location near the discharge and feed ports. The D CPU needs to be upgraded, and after the upgrade, the issue of “display movement - YD” will be resolved” ； Solution: Notify the manufacturer’s customer service about the issue of upgrading the CPUE settings; this problem often occurs on propylene storage tanks and VCM tanks, where “Display Move-YD” appears. Treatment method: 1) Drain waste and clean the tank ； 2) Re-find the probe installation location ； 3) Instrument upgrade.