LimsPulse
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
Illustration of Kinematic Viscosity Bath
Follow your site SOP
This is a typical operating sequence for learning. Your instrument model and approved SOP take precedence.
STAGE 1

Before you start

  1. 1Check the bath temperature on the calibrated reference thermometer, not only on the controller display.
  2. 2Check bath medium level and clarity; top up or replace if cloudy.
  3. 3Select clean, dry viscometers whose constants are certified and whose range gives a flow time of at least 200 s.
  4. 4Filter the sample (for example through a fine sieve or sintered glass) if it may contain particles.
  • A dirty or wet viscometer gives wrong flow times; any drop of solvent or water left inside changes the result.
STAGE 2

Charging

  1. 1Fill the viscometer as its type requires (inverted suction for Cannon-Fenske routine, filling tube for Ubbelohde), avoiding bubbles.
  2. 2Hang it vertically in the holder so the sample is fully immersed.
  3. 3Allow the sample to reach bath temperature, typically about 30 minutes (longer for viscous samples).
  • Do not use mouth suction; use a rubber bulb or vacuum line to draw sample.
STAGE 3

Timing

  1. 1Draw the sample above the upper timing mark and let it flow freely.
  2. 2Start the timer as the meniscus passes the upper mark and stop it as it passes the lower mark.
  3. 3Repeat to get a second flow time from the same filling (or charge a second viscometer as the method requires).
  4. 4Calculate ν = C × t for each time and check the two agree within the determinability; if not, clean and repeat.
  • Keep the timer's start and stop on the same edge of the meniscus each time.
STAGE 4

Cleaning

  1. 1Drain the viscometer and rinse several times with a suitable solvent (for example petroleum spirit or heptane), then a volatile solvent such as acetone.
  2. 2Dry with a gentle stream of filtered dry air or by vacuum.
  3. 3Periodically clean with a non-chromic acid cleaner to remove deposits.
  4. 4Record results with the viscometer serial number, constant and bath temperature.
  • Avoid chromic acid cleaning mixtures; they are highly toxic and carcinogenic. Use the alternatives your SOP allows.
In LimsPulse · Calibration Management

Keep every Viscosity bath in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

See how