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SAE J2663-2019: Measuring Fuel Permeation in Elastomeric Hoses via Weight Loss
Overview of the Weight Loss Method
This SAE Recommended Practice provides a gravimetric procedure for measuring fuel permeation at elevated temperatures through low-permeating hose or tubing of elastomeric or composite construction. The method is accurate to within approximately ±10% and is well-suited for permeation rates above 1 g/m²/day (GMD). Standardized test fuels include Fuel C and CE10, with standard temperatures of 40°C and 60°C. The standard has been stabilized, indicating mature technology and consistent methodology.
The test offers two distinct approaches:
- Method A (Plug and Fill): The hose sample is filled to ~90% capacity with test fuel, both ends are plugged, and weight loss is monitored over time. This method is ideal for samples with low surface-to-volume ratios where fuel loss remains below 10%.
- Method B (Fuel Reservoir): One end of the hose is plugged, and the other connects to a fuel reservoir. This configuration accommodates smaller-diameter hoses (below 18 mm) or those with high permeation rates, where the larger fuel volume minimizes compositional changes.
| Feature | Method A (Plug & Fill) | Method B (Reservoir) |
|---|---|---|
| Sample preparation | Fill hose, plug both ends | Plug one end, attach reservoir |
| Fuel volume | Limited to hose internal volume | Extended by reservoir (size chosen per need) |
| Best for | Larger diameters, lower permeation | Small diameters, higher permeation |
| Fuel loss limitation | <10% total loss during test | <10% total loss (reservoir sizing ensures) |
Methodological Insights and Design Considerations
🛠️ A key design element in the procedure is the recommended plug design, which includes a small fill hole with a gasketing system. This arrangement allows plugs to be inserted before filling, avoiding pressurization issues and ensuring low permeation at the seal. When using Method B, the reservoir must be sized so that fuel loss stays below about 10% over the test period; this prevents compositional drift that could skew permeation rates. The standard specifies the use of an analytical balance sensitive enough to capture weight changes confidently—typically the weight loss between weighings should be at least ten times the balance sensitivity.
📋 Key Engineering Insight
Choose Method A for pure fluids or when compositional changes do not affect permeation. Opt for Method B when testing with fuel mixtures like CM15, where methanol loss can change permeation characteristics. Always verify steady state by ensuring linear weight loss over a sufficient portion of the test duration. Non-linear regions may indicate problems such as leaking plugs, environmental fluctuations, or fuel composition shifts.
Practical Guidance and Frequently Asked Questions
Common Pitfalls to Avoid
⚠️ Even with a straightforward method, some mistakes can compromise results. The most common are:
- Exceeding the 10% fuel loss limit, which alters fuel composition and invalidates the permeation rate.
- Applying the method to high-boiling-point materials that will not fully evaporate from the hose exterior at the test temperature.
- Improper plug insertion causing damage or poor sealing, leading to leakage instead of permeation.
- Ignoring non-linear weight-loss curves that may denote underlying changes in the sample or fuel.
⚠️ Caution – Fuel Loss Management
Track total fuel loss carefully. For accurate results, limit loss to less than 10% of the initial fuel weight. When >10% loss occurs, compositional changes can become significant, especially for blended fuels like CE10 or CM15. This may lead to non-linear behavior and unreliable permeation values.
Frequently Asked Questions
How do I choose between Method A and Method B?
Consider the hose’s surface-to-volume ratio. Method A works well for larger-diameter hoses or those with low permeation rates. For smaller diameters (under 18 mm) or high permeation, Method B provides a larger fuel reservoir to keep relative loss low and maintain fuel composition.
What is the maximum allowable fuel loss during testing?
The standard recommends limiting total fuel loss to less than 10% of the initial fuel mass. This threshold helps ensure that the fuel composition does not change enough to affect permeation rate. However, the acceptable limit may vary with fuel type and material; examine weight loss curves for linearity as a check.
How should the plug be designed to minimize permeation?
The recommended plug includes a small fill hole with a gasketing system (see Appendix A of the standard). Using such a design allows the plug to be inserted before adding fuel, preventing pressurization that can occur when forcing plugs into a filled hose. Proper gasketing ensures that weight loss comes only through the hose wall, not the plugs.
What does a non-linear weight loss curve indicate?
Non-linearity can result from environmental changes (temperature, air flow), but when conditions are stable, it often signals that the fuel composition is changing (e.g., rapid loss of a high-permeation component) or that the sample is undergoing physical changes. Such curves should be investigated; they indicate that the permeation rate is not steady and the reported value may not reflect the steady-state characteristic of the material.
This article summarizes key aspects of SAE J2663-2019. Always refer to the full standard for complete procedural details and official wording.
