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D2709-22 – Standard Test Method Technical Guide
📐 Scope and Applicability
ASTM D2709-22 provides a standardized centrifuge method for determining the volume of free water and sediment in middle distillate fuels. The method is strictly applicable to fuels whose kinematic viscosity falls between 1.0 mm²/s and 4.1 mm²/s at 40 °C and whose density falls between 770 kg/m³ and 900 kg/m³ at 15 °C. It covers fuels corresponding to Specifications D396 (Grades No. 1 and 2), D975 (Grades No. 1-D and 2-D), D2880 (Grades No. 0-GT, 1-GT, and 2-GT), and D3699 (Grades No. 1-K and 2-K), as well as similar middle distillate fuels and blendstocks.
⚠️ Important Distinction: For heavier fuel oils with higher viscosities outside the specified range, refer to Test Method D1796, which covers the determination of water and sediment in such fuel oils by centrifuge.
⚙️ Test Procedure and Conditions
The procedure involves centrifuging a 100 mL undiluted fuel sample under strictly defined parameters to separate free water and sediment. The core test conditions are summarized below:
| 🟦 Parameter | 📐 Required Specification |
|---|---|
| Sample Volume | 100 mL (undiluted) |
| Relative Centrifugal Force (rcf) | 800 |
| Centrifuge Time | 10 minutes |
| Test Temperature Range | 21 °C to 32 °C (70 °F to 90 °F) |
| Reading Precision | 0.005 mL (settled in tip of tube) |
After centrifugation, the volume of the material that has settled into the calibrated tip of the centrifuge tube is read directly.
💡 Best Practice for Temperature Control: Strictly maintaining the sample and centrifuge within the 21 °C to 32 °C range is critical. Temperatures outside this range can alter the solubility of water in the fuel, leading to inaccurate free water readings.
📊 Measured Properties and Terminology
The test specifically measures free water, defined as water in excess of that soluble in the liquid fuel at the test temperature, and sediment. These typically appear as a haze, cloudiness, droplets, or a distinct water layer after centrifugation. The result is reported as a volumetric percentage of the original sample. The common fuel grades covered by this method are:
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