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D6375-24 – Standard Test Method Technical Guide
📋 Scope and Significance
This test method, D6375-24, covers the determination of the Noack evaporation loss of lubricating oils using a thermogravimetric analyzer (TGA). It is applicable to base stocks and fully formulated lubricants with evaporative losses ranging from 0% to 30% by mass. This procedure requires much smaller specimens and is faster and safer than the traditional Noack method using Wood’s metal.
The evaporative loss determined by this test method is equivalent to that from the standard Noack test methods (Test Method D5800). This method provides a safe and fast alternative for evaluating lubricant volatility under controlled conditions.
⚙️ Test Procedure and Conditions
In this procedure, a small lubricant specimen is placed in an appropriate TGA specimen pan. The pan is placed in the TGA pan holder and rapidly heated to between 247 °C and 249 °C under a stream of air. The specimen is then held isothermal for a duration determined by the Noack reference time. Throughout the process, the TGA monitors and records the mass loss due to evaporation. The Noack evaporation loss is calculated from the mass loss versus time curve at the specified reference time.
Key parameters include the Noack reference oil, which is used to verify proper operation, and the Noack reference time, which is the time required for the reference oil to reach its known evaporative loss under the test conditions. The TGA Noack volatility is expressed as the evaporative loss in mass percent.
📊 Key Terminology and Data
Essential definitions from the standard include:
- Noack reference oil – the oil provided by Noack equipment manufacturers to check proper operation.
- Noack reference time – the time (in minutes) required for the Noack reference oil to reach its known evaporative loss.
- TGA Noack volatility – the evaporative loss (in mass percent) of a lubricant as determined by this test method.
Key test parameters are summarized in the table below.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Test Temperature | 247 °C to 249 °C |
| Atmosphere | Air flow |
| Evaporation Loss Range | 0% to 30% by mass |
| Specimen Size | Significantly smaller than standard Noack |
💡 Note: This TGA method is significantly safer than the traditional Noack method as it avoids the use of Wood’s metal and requires smaller sample volumes, reducing exposure to hazardous materials.
⚠️ Important: Performance of the test method relies on proper temperature calibration and use of Noack reference oil. Refer to Test Method E1582 for TGA calibration.
❓ Frequently Asked Questions
🔍 What is the temperature range for the TGA Noack method?
The test is conducted at a temperature between 247 °C and 249 °C under an air atmosphere.
💡 How does this method compare to the standard Noack method?
This TGA method provides the same evaporative loss results but is faster, uses smaller specimens, and is safer than the Wood’s metal-based method.
⚡ What is the evaporation loss range for this test method?
The method is applicable for lubricating oils with evaporative losses from 0% to 30% by mass.
📌 What is the Noack reference time?
The Noack reference time is the time in minutes required for the Noack reference oil to achieve its known evaporative loss under the test conditions, used to calibrate the procedure.