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D2068-24 – Standard Test Method Technical Guide
📐 Scope and Applicable Fuel Types
ASTM D2068-24 provides three distinct procedures for the quantitative determination of the Filter Blocking Tendency (FBT) and filterability of middle distillate fuel oils, biodiesel, and biodiesel blends. The result is highly dependent on the specific filter medium used for the procedure. Per the Introduction, substitution of a different filter medium without explicit agreement from the specifier is strictly prohibited.
The three procedures are restricted to fuels with a kinematic viscosity between 1.3 mm²/s and 6.0 mm²/s at 40 °C. Specific ASTM specification fuels covered by the scope include:
| 🟦 Specification | 📏 Applicable Grades |
|---|---|
| D396 | No. 1 and No. 2 Fuel Oils |
| D975 | 1-D, Low Sulfur 1-D, and 2-D Diesel Fuel |
| D2880 | 1-GT and 2-GT Gas Turbine Fuel Oils |
| D6751 | Biodiesel Fuel Blendstock (B100) for Middle Distillate Fuels |
⚠️ Critical Prerequisites and Limitations
A critical prerequisite for conducting any D2068-24 procedure is ensuring the fuel sample is completely free of undissolved water. Section 1.2 of the method explicitly excludes fuels containing free water. The sample condition should be verified using standard practices such as D4176 (Visual Inspection) or D4860 (Numerical Rating) before proceeding.
🚫 Critical Exclusion (Section 1.2): This test method is not applicable to fuels that contain free (undissolved) water. Testing such fuels violates the scope of D2068-24 and will produce non-conforming results.
💡 User Responsibility (Section 1.4): This standard does not purport to address all safety concerns. Users must establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
📊 Apparatus, Filter Media, and Supporting Standards
The test apparatus relies on tightly controlled filter media. To ensure consistency in media porosity, the standard references ISO 5636-5 (Gurley method) for determining the air permeance and resistance of the paper and board filter media. This guarantees that the physical characteristics of the filters are uniform across different laboratories and test batches.
D2068-24 operates within a comprehensive framework of related standards covering sampling, contamination assessment, and statistical validation.
| 🎯 Standard | ⚡ Purpose in D2068-24 Framework |
|---|---|
| D4057 / D4177 | Manual and Automatic Sampling of Petroleum Products |
| D4176 / D4860 | Detection of Free Water and Particulate Contamination |
| D6426 | Related Test Method for Determining Filterability |
| D6300 | Determination of Precision and Bias Data for Test Methods |
| D6708 | Statistical Assessment and Improvement of Agreement Between Test Methods |
| ISO 5636-5 | Gurley Method for Filter Media Air Permeance and Resistance |
❓ Frequently Asked Questions
🔍 What does ASTM D2068-24 measure?
It measures the Filter Blocking Tendency (FBT) and filterability of middle distillate fuel oils, biodiesel, and biodiesel blends using one of three defined procedures with specific filter media.
💡 Can I substitute a different filter if the specified one is not available?
No. The standard explicitly prohibits substituting a different filter or procedure without the explicit agreement of the specifier, as the test result is dependent on the mandated filter media.
⚡ What is the viscosity limit for fuels tested by this method?
The test method is applicable only to fuels within the kinematic viscosity range of 1.3 mm²/s to 6.0 mm²/s at 40 °C.
📌 Is the test valid if the fuel sample contains free water?
No. The scope clearly states the method is not applicable to fuels containing free (undissolved) water. The sample condition must be verified prior to testing.