Problems on this page:
Level reading wrong
Hits OEE: Quality
Symptoms: The level shown in the control system does not match the tank when it is checked by hand.
Sensor settings do not match the tank geometry
Check the tank height, the empty and full distances and the units in the sensor.
Product density different from the setting on pressure-based level
Check the density used in the calculation for the product in the tank.
Build-up on the sensor or in the tank
Inspect and clean the sensor and the area around it.
Foam or vapour confusing a radar or ultrasonic sensor
Check the reading against the product conditions and the sensor type.
Prevention: Level checked against a manual dip on a schedule.
Reading jumps or loses echo
Hits OEE: Availability
Symptoms: A radar or ultrasonic level jumps or shows a lost-echo fault.
Agitator blades or fittings giving false echoes
Map out false echoes with the sensor setup routine.
Sensor mounted too close to the wall or inlet
Check the mounting position against the maker guidance.
Condensation or build-up on the antenna
Clean the antenna and check for an air purge option.
Surface turbulence during filling
Increase damping or use a stilling well.
Prevention: Echo quality checked during planned maintenance.
High level switch not tripping
Hits OEE: Availability
Symptoms: A tank overfills because the high level switch did not act.
Switch coated with product
Clean the switch and check its sensitivity setting.
Switch mounted at the wrong height
Check the switch height against the overfill limit.
Wiring or logic fault
Test the switch function end to end, including the action it should trigger.
Switch never tested
Add a proof test to the maintenance plan; an overfill protection that is never tested may not work when needed.
Prevention: High level switches proof tested on a fixed schedule.
Low level pump protection not working
Hits OEE: Availability
Symptoms: Pumps run dry because the low level signal came too late.
Low level setpoint too low
Raise the setpoint so the pump stops with enough liquid above the suction.
Sensor reading delayed by damping
Reduce the damping on the signal used for the low level alarm so it reacts in time.
Vortex at the outlet before the sensor sees low level
Check the outlet design and fit a vortex breaker if air is drawn in early.
Signal not interlocked with the pump
Check that the low level signal actually stops the pump in the control logic.
Prevention: Dry-running events recorded with the level at the time.
Solids level reading wrong in silos
Hits OEE: Quality
Symptoms: Silo levels jump or disagree with deliveries and usage.
Material cone and dust affecting the reading
Check the sensor type suits solids, and aim it at the right point.
Build-up on the sensor
Clean the sensor and consider an air purge where dust sticks to it.
Silo geometry settings wrong
Check the silo height and cone dimensions entered in the sensor setup.
Filling dust during deliveries
Hold the last good reading while a delivery is blowing product into the silo.
Prevention: Silo level compared with stock records monthly.
Signal lost
Hits OEE: Availability
Symptoms: The level signal drops to a fault value, and pumps or valves fall back to their safe state.
Supply power lost
Check the supply voltage at the sensor terminals.
Cable damaged on the tank roof or in a tray
Inspect the cable route for damage and check the connections.
Water in the sensor housing
Dry the housing, replace the seal and check the cable gland.
Sensor electronics failed
Read the diagnostics and replace the sensor if it has failed.
Prevention: Level signal faults logged by tag.
Hygiene problems on food tanks
Hits OEE: Quality
Symptoms: Hygiene swabs fail around the level sensor fitting on a food or pharma tank.
Dead space at the process connection
Use a hygienic process connection that is flush with the tank wall.
Cleaning spray not reaching the sensor
Check the spray device coverage around the sensor.
Seal material not suited to the cleaning chemicals
Check the seal material and replace damaged seals.
Sensor refitted with a gap after maintenance
Check the fitting after any sensor work.
Prevention: Swabs taken at sensor points after cleaning.
Interface level wrong
Hits OEE: Quality
Symptoms: The interface between two liquids, such as oil and water, is reported in the wrong place.
Density difference too small for the method
Check that the sensor type can measure an interface with these two liquids.
Emulsion layer between the liquids
Check the process for a mixed layer that the sensor reads as the interface.
Upper and lower liquid settings wrong
Check the dielectric or density settings for both liquids.
Build-up on the probe
Clean the probe.
Prevention: Interface reading checked against a sample.
Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.
Related equipment guides: silo / hopper · mixer / agitator · centrifugal pump · PLC · photo-eye sensor
Stop the same fault coming back
Recurring level sensor stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.
Book a Fabrico demo
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Related tools: full troubleshooting directory · OEE calculator · downtime cost · MTBF / MTTR · glossary
Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover