Kinematic Viscosity Tester（Kinematic Viscosity Tester）
Kinematic viscosity is a key indicator for evaluating the fluidity of lubricating oil, hydraulic oil, diesel, fuel oil, etc., usually measured in mm²/s (cSt). Common test standards include ASTM D445, ISO 3104, and GB/T 265.
Composition of Kinematic Viscosity Tester
Main equipment:
| Device Name | Application |
|---|---|
| Kinematic Viscosity Tester | Maintain constant temperature and measure oil flow time |
| Capillary viscometer (Ubbelohde, countercurrent, Pinnacle, etc.) | Mainly used for oil flow rate measurement |
| Constant temperature bath (±0.01°C control accuracy) | Maintain oil sample at target temperature |
| Stopwatch (accuracy 0.1s) | Record outflow time |
| Vacuum suction device (suitable for high viscosity samples) | Helps high viscosity oil enter the viscometer |
| Washing solvent (such as pentane, ethanol) | Cleaning the Viscometer Pipe |
Test procedures (ASTM D445 / GB/T 265)
Step 1: Prepare the sample
✅ Take 10-15mL of sample and put it in a 105°C oven to dry and remove moisture (if applicable)
✅ Filter impurities with filter paper (if necessary)
✅ Select a suitable capillary viscometer (select the inner diameter according to the expected viscosity)
Step 2: Fill the oil sample
✅ Clean the viscometer (blow dry with solvent + dry air)
✅ Use a pipette to inject the oil sample into the viscometer (fill to the specified scale)
✅ Place the viscometer vertically in a constant temperature bath and let it stand for 10-15 minutes to stabilize the temperature
Step 3: Measuring Viscosity
✅ Measure at a specified temperature (such as 40°C or 100°C)
✅ Use a stopwatch to record: the time (t, unit: seconds) for the oil sample to pass between two scale lines
✅ Repeat the measurement twice to ensure that the error is ≤0.2%
Step 4: Calculate viscosity
✅ Kinematic viscosity calculation formula: ν=C×t
IN：
- ν = Kinematic viscosity (mm²/s or cSt)
- C = Capillary viscometer constant (given on the viscometer)
- t = time for the oil sample to pass the scale line (seconds)
✅ Example calculation:
- Capillary viscometer constant C = 0.035 mm²/s²
- The test time t = 120s
- Kinematic viscosity:
ν=0.035×120=4.2mm²/s
Test results and standards
| Oil type | Kinematic viscosity at 40°C (cSt) | Kinematic viscosity at 100°C (cSt) |
|---|---|---|
| Hydraulic oil ISO VG 46 | 41.4 – 50.6 | 6.8 – 8.5 |
| Engine Oil SAE 10W-40 | 12.5 – 16.3 | 3.5 – 4.5 |
| Diesel oil | 1.9 – 4.1 | 0.9 – 2.5 |
✅ Kinematic viscosity affects the fluidity, lubricity and atomization performance of oil, and is very important when selecting lubricants and fuels.
Notes on kinematic viscosity test
✔ Precise temperature control (±0.01°C), temperature error will seriously affect the results
✔ Clean the viscometer, residues may affect the measurement accuracy
✔ Use a suitable capillary viscometer, too large or too small will affect the results
✔ Repeat the test, calculate the average value, and ensure the data is stable
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