What Is Viscosity?
Viscosity is the measure of a fluid’s resistance to flow. In transformer oil, kinematic viscosity is typically measured in centistokes (cSt) at standard temperatures—commonly 40°C and 100°C. Viscosity affects how easily the oil circulates through the transformer’s cooling and insulating system.
Test Standard
ASTM D445 – Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and the Calculation of Dynamic Viscosity)
Key Gases Measured
Insulating Liquids – Measurement of Relative Permittivity, Dissipation Factor (Tan δ) and DC Resistivity.
Temperature | Ideal Range for New Mineral Oil | Action if Out of Range |
---|---|---|
40°C | 8 – 12 cSt | Check for contamination or aging |
100°C | 2 – 4 cSt | Evaluate oxidation or sludge |
Why Viscosity Testing Is Important
- Ensures efficient oil circulation for cooling
- Helps detect oxidation and sludge buildup
- Indicates contamination or polymerization
- Supports diagnosis of oil aging and breakdown
- Reduces risk of overheating and insulation damage
Our Testing Process
- Vacuum-sealed sample collection with barcode tracking
- Automated kinematic viscosity measurement at controlled temperatures (40°C / 100°C)
- Calibration using certified viscosity reference standards
- Data logged into our ERP for tracking and reporting
- AI-generated insights and recommendations included in report
Report Includes
- Measured viscosity at 40°C and/or 100°C (in cSt)
- Comparison to standard and OEM-specified values
- Deviation from baseline (if historical data exists)
- Possible causes and recommended actions
- Integrated with other oil test results for combined assessment
Why Choose Tru-FIL?
- ASTM D445-compliant lab procedures
- NABL-grade calibrated viscometers and bath systems
- ERP-integrated testing with historical trend tracking
- Sample pickup from anywhere in India using vacuum-sealed bottles
- 24/7 laboratory operations and rapid reporting