Test Procedure to Determine the Hydrocarbon Losses from Fuel Tubes, Hoses, Fittings, and Fuel Line Assemblies by Recirculation
This SAE Recommended Practice is intended for the determination of the losses of hydrocarbon fluids, by permeation through component walls as well as through 'microleaks' at interfaces of assembled components while controlling temperature and pressure independently of each other. This is achieved in a recirculating system in which liquids which are transported through walls and joints are collected by a controlled flow of nitrogen (dry) and adsorbed by activated charcoal.
Rationale: The current measurement technique is not adequate to measure the very small emissions of multilayer hoses with a barrier material. Because the exposed surface area of the hoses under test is so small, typically the emissions are below the readability of the test method (scales). Any reading is essentially "noise" in the test. The emissions requirement is in grams/meter squared, therefore the emission levels recorded need to be multiplied by a large number in order to extrapolate the readings to a square meter of material. So, in many cases, you are simply multiplying "noise". My proposal is that we add the option of a Mini/MicroSHED alternative to allow for the ability to measure lower emission levels of the multilayer hoses now in production and offer the ability to discern improvements in utilization of new materials and/or processes going forward.
The fuel hose is currently the only portion of the fuel system that does not have a Mini or MicroSHED option for testing its permeability.