MEK 6400: bubble fault in volumetric tube with no visible leak
What happened
The analyzer repeatedly reported the BBL1 bubble fault in the volumetric tube during measurements, while no fluid leak was visible anywhere in the system.
What was checked
- Tightness test of the fluid path to see whether the system holds pressure and vacuum.
- Reseating of the baths and inspection of the pressure gauges (manometers) behind them.
- Step-by-step tracing of the aspiration path to find where air could be drawn in.
Cause
The engineers found that air was being sucked in under a rubber cuff (seal) in the volumetric tubing — an air ingress that does not show up as a fluid leak.
What was done
Replacing the rubber cuffs (seals) of the volumetric tube stopped the air ingress, and the bubble fault no longer appeared on repeated measurements.
Safety
Treat all fluid-path parts, spills and waste from a hematology analyzer as potentially infectious: wear gloves and eye protection when opening the tubing, and disinfect any spilled diluent or sample.
Lesson: A bubble error without a visible leak usually means air is being drawn in at a seal on the suction side, so check the rubber cuffs and joints before suspecting electronics or the counting chamber.
Covered in the course: Lab Analyser Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.