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D2392-15 – Standard Test Method Technical Guide
🔬 Scope and Significance
This test method, designated ASTM D2392-15 (Reapproved 2021), provides a standardized procedure for determining the acceptability of color in dyed aviation gasolines. The specific hue and color intensity of aviation fuels serve as essential visual safety markers, allowing for rapid grade identification and minimizing the risk of misfueling aircraft. The standard operates strictly in SI units and emphasizes the user’s responsibility to establish appropriate safety and environmental practices.
⚠️ Critical Safety Alert: Gasoline is extremely flammable. The user must carefully review the specific warning statements found in Annex A1 of the standard and adhere strictly to all applicable safety, health, and environmental regulations before handling any materials or operating the apparatus.
⚙️ Apparatus and Reference Materials
The accuracy of the color determination depends entirely on a specific apparatus configuration. The core instrument is a split-field color comparator for simultaneously viewing the sample and the standard by transmitted light. The sample and reference liquid are contained in dedicated glass fluid tubes with a 200 mm viewing depth and fused-on plane bottoms. Polished optical glass plungers are used to seal the tubes. The acceptability of the color is determined by comparing the sample against Aviation Gasoline Color Standards, which are permanent-color glass disks.
| 🟦 Component | 📏 Specification |
|---|---|
| Fluid Tubes | Optical glass; 200 mm viewing depth; fused-on plane bottom plate |
| Plungers | Polished optical glass |
| Color Standards | Permanent-color glass disks (Min/Max intensity sections) |
| Comparator | Split-field design for simultaneous transmitted light viewing |
The reference liquid chosen for the baseline comparison can be either distilled water or a sample of the base gasoline before the addition of dye or lead alkyl fluid. This selection provides flexibility depending on whether a general clarity comparison or a matrix-specific baseline is required.
| 🧪 Reference Liquid | 📐 Application |
|---|---|
| Distilled Water | Standard transparent baseline for general color comparison |
| Undyed Base Gasoline | Matrix-matched baseline for critical accuracy |
💡 Procedural Tip: To ensure accurate optical comparison, wipe all excess liquid from the outside of the fluid tubes and the top of the plungers immediately before placing them in the comparator. This eliminates any optical interference from drips, smudges, or fingerprints.
📝 Procedure and Color Evaluation
The testing sequence begins by thoroughly cleaning the optical surfaces of the comparator and balancing the intensities of the light source across the two halves of the split-field using empty tubes. The left tube is filled with the chosen reference liquid, while the right tube receives the dyed test sample. After inserting the glass permanent-color standards, the operator compares the two fields.
The evaluation specifically examines both the hue and the color intensity of the sample against the minimum and maximum sections of the glass standards. An acceptable result is achieved when the hue of the sample is approximately the same as the standard, and the intensity of the color is between, or equivalent to, the established minimum and maximum benchmarks.
❓ Frequently Asked Questions
🔍 What is the primary purpose of this ASTM standard?
ASTM D2392 defines the test method for evaluating the acceptability of color in dyed aviation gasolines to ensure proper visual grade identification.
💡 What materials are approved as the reference liquid?
The standard specifies two options: distilled water or an undyed sample of the same gasoline taken before the addition of dye or lead alkyl fluid.
📐 What is the exact viewing depth specified for the fluid tubes?
The glass fluid tubes must have a precise viewing depth of exactly 200 mm, as stated in the apparatus section of the standard.
📌 How is a passing result defined in this test?
The sample passes if its hue is visually similar to the glass permanent-color standard and its color intensity falls within the range defined by the minimum and maximum color sections of that standard.