Description / Abstract:
This test method is intended for measuring fuel permeation at
elevated temperature through low permeating hose or tubing samples
of elastomeric or composite construction. The expected accuracy of
the method is about ±10% of the sample permeation rate.
Hose permeation testing can be done two ways: Method A – Plug
and Fill or Method B – using a fuel reservoir.
Method A involves plugging one end of the hose, filling the
sample to about 90% full with test fuel, plugging the other end,
and then exposing the plugged sample to a desired test temperature,
with the weight loss measured over time.
Method B involves plugging one end of a hose, and then
connecting the other end to a fuel reservoir. The hose sample and
reservoir are then exposed to a desired test temperature with the
weight loss measured over time.
This procedure presents a recommended plug design that permits
inserting the plugs prior to adding the test fluid. One of the
plugs has a small fill hole with a gasketing system that insures
low permeation. This design prevents assembly problems created by
pressurizing a fuel filled configuration, when inserting plugs with
high insertion forces.
Method A is intended for samples with low surface to volume
ratios, so that the % fuel loss over the test period is low, and
the resultant fuel compositional change does not significantly
affect the permeation rate (typically less than 10% fuel loss for
CE10 fuel). Method B should be used when fuel loss with Method A
would be too large. This is typically done where hoses are small
diameter (less than 18 mm) and have high permeation rates. The size
of the reservoir chosen for Method B depends on the permeation rate
of the sample and should be large enough to assure that fuel loss
over the test period is less than about 10%. The amount of fuel
loss that might be acceptable will depend on the fuel composition
and the type of material tested. Uniform deviations from linearity
of the weight loss versus time curves that are not a result of
changes in environmental conditions such as temperature should be
considered suspect regions and could be a result of compositional
or configurational changes might be affecting the permeation
rate.
Standard permeation test temperatures are 40 °C and 60 °C.
Standard test fuels are Fuel C and Fuel CE10. Other fuels, such as
Fuel CM15, and other volatile liquids may be tested according to
this procedure as desired. The method is not applicable for
measuring permeation of higher boiling materials that will not
completely evaporate from the exterior sample surface at the test
temperature.