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D323-20 – Standard Test Method Technical Guide
📜 Standard Overview and Scope
ASTM D323-20, the Standard Test Method for Vapor Pressure of Petroleum Products (Reid Method), provides procedures for determining vapor pressure of gasoline, volatile crude oil, and other volatile petroleum products. The Reid vapor pressure is measured at 37.8 °C (100 °F) as an absolute pressure in kilopascals or psi. This standard is not applicable to liquefied petroleum gases or fuels with oxygenates other than MTBE; refer to Test Methods D1267, D6897, or D4953 for those materials. Values in SI units are the standard, with inch-pound units provided for reference. This standard has been approved for use by U.S. Department of Defense agencies.
⚙️ Test Procedures and Specifications
The standard defines four procedures based on material type and vapor pressure range:
| 🟦 Procedure | 📏 Applicable Materials | 📐 Vapor Pressure Range | 🎯 Key Notes |
|---|---|---|---|
| Procedure A | Gasoline and other petroleum products | Less than 180 kPa (26 psi) | Primary method for routine samples |
| Procedure B | Other materials (gasoline-based precision) | Not explicitly defined | Precision derived from gasoline interlab study |
| Procedure C | High vapor pressure materials | Greater than 180 kPa (26 psi) | For products exceeding standard range |
| Procedure D | Aviation gasoline | Approximately 50 kPa (7 psi) | Optimized for aviation fuel testing |
📊 Key Technical Notes
Critical considerations for applying this method include:
💡 Important Note: The Reid vapor pressure is an absolute pressure at 37.8 °C (100 °F). It differs from true vapor pressure due to partial sample vaporization and the presence of air and water vapor in the confined chamber (see Note 1 of the standard).
⚠️ Safety Advisory: Specific warning statements are provided in Sections 7, 18, and subsections 12.5.3, 15.5, 21.2, A1.1.2, A1.1.6, and A2.3. Users must establish appropriate safety, health, and environmental practices before handling volatile samples.
❓ Frequently Asked Questions
🔍 What is the purpose of ASTM D323-20?
It is used to determine the vapor pressure of gasoline, crude oil, and other volatile petroleum products for quality control and regulatory compliance, using the Reid method.
💡 Can this method be used for oxygenated fuels?
It is applicable only to fuels containing MTBE as the oxygenate. For other oxygenated blends, use Test Method D4953.
⚡ What is the vapor pressure limit for Procedure A?
Procedure A applies to products with a vapor pressure of less than 180 kPa (26 psi), covering most standard gasoline samples.
📌 Why is Reid vapor pressure different from true vapor pressure?
Per Note 1, the Reid method measures an absolute pressure at 37.8 °C but is affected by sample vaporization and air/water vapor in the confined space, causing a slight deviation from true vapor pressure.