ASTM D381-22

Overview

ASTM D381-22 outlines the Standard Test Method for Gum Content in Fuels by Jet Evaporation. Issued by ASTM International, this standard provides a procedure to determine the gum content present in aviation fuels, motor gasolines, and other volatile distillates. Gum content refers to the nonvolatile residue formed when fuels are evaporated under specific conditions, revealing potential contaminants, oxidation products, or degradation due to handling and storage.

Testing gum content is essential for quality control in fuel manufacturing and distribution. While the absolute correlation between gum content and engine deposits is not well established, high gum values can indicate contamination or improper fuel handling, potentially affecting engine performance or reliability.

Key Topics

• Test Scope

  • Applicable to finished aviation fuels, motor gasolines, and other volatile distillates, including those with alcohols, ethers, and deposit control additives.
  • Provides a step for determination of heptane-insoluble residues in non-aviation fuels.
  • All measurements are performed using SI units, with specific attention to safety regarding mercury-containing apparatus.

• Significance of Results

  • High gum levels can potentially cause fuel system deposits and operational problems, such as sticking intake valves in engines.
  • The procedure measures oxidation products and contaminants formed prior to or during mild testing conditions.

• Test Procedure

  • A measured quantity of fuel is evaporated under controlled air or steam flow and temperature.
  • Residue is weighed pre- and post-heptane extraction (for non-aviation fuels) to determine total and insoluble gum content.
  • Results are reported in milligrams per 100 mL of fuel.

• Precision and Reporting

  • Repeatability and reproducibility guidelines are provided.
  • Specific rounding and reporting practices are outlined based on gum content values.

Applications

The ASTM D381-22 test method is widely used for:

• Fuel Producers and Refineries: Assuring adherence to product specifications by monitoring gum content through production and blending operations.
• Quality Control Laboratories: Routine assessment of finished fuels to detect oxidation products, high boiling impurities, or improper storage conditions.
• Fuel Distributors and Airports: Monitoring aviation fuels for gum content that may indicate contamination from higher boiling oils or mishandling.
• Regulatory Compliance: Supporting requirements in procurement and safety regulations for both military and civil applications.

Low gum content is generally considered desirable, reducing risks related to induction system deposits and maintaining cleaner combustion.

Related Standards

For a comprehensive approach to fuel testing and quality, consider related ASTM standards:

• ASTM D1655 - Specification for Aviation Turbine Fuels
• ASTM D4057 - Practice for Manual Sampling of Petroleum and Petroleum Products
• ASTM D4175 - Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• ASTM E1 - Specification for ASTM Liquid-in-Glass Thermometers

Additionally, the Energy Institute’s IP 540 offers a comparable method for jet evaporation gum determination in aviation turbine fuel.

Keywords: ASTM D381, gum content, jet evaporation, fuel quality, aviation fuel testing, motor gasoline testing, fuel oxidation products, heptane insoluble residue, ASTM standards, petroleum product testing.