Petroleum testing
Kinematic Viscosity Bath
A clear, stirred liquid bath held to within about ±0.02 °C, in which calibrated glass capillary viscometers are timed. Flow time multiplied by the viscometer constant gives kinematic viscosity in mm²/s (cSt).
- Lubricant blending
- Petroleum refining
- Fuel terminals
- Marine fuel testing
- Fleet and machinery oil condition monitoring
- Independent testing laboratories
TROUBLESHOOTING
Common problems, causes and fixes
Two flow times disagree
Likely causes
- • Sample not at temperature yet
- • Bubble or particle in the capillary
- • Viscometer not vertical
- • Bath temperature cycling
What to do
- • Allow longer equilibration
- • Filter sample and refill
- • Check holder alignment
- • Tune the controller or improve stirring
Results biased high or low on a check standard
Likely causes
- • Bath temperature offset
- • Wrong viscometer constant entered
- • Residual solvent or water in viscometer
What to do
- • Check temperature with a calibrated thermometer
- • Check constant against the certificate for the test temperature
- • Clean and dry thoroughly
Flow time below 200 s
Likely causes
- • Viscometer too large for the sample
What to do
- • Use a smaller-capillary viscometer
Meniscus hard to see
Likely causes
- • Dark or opaque sample
- • Cloudy bath medium
What to do
- • Use a reverse-flow (opaque) viscometer
- • Replace bath medium and clean the glass
Bath cannot reach or hold temperature
Likely causes
- • Lid missing, heat loss high
- • Heater or chiller fault
- • Medium level low
What to do
- • Fit the lid
- • Service heater/chiller
- • Top up medium
In LimsPulse · Calibration Management
Keep every Viscosity bath in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.