Nonmetallic Fuel System Tubing with One or More Layers
This SAE Standard covers the minimum requirements for multilayer, nonmetallic tubing as manufactured as a liquid-carrying or vapor-carrying component for use in gasoline, alcohol blends with gasoline, or diesel fuel systems. Monowall tubing (one layer construction) is also covered by this document. The construction has one or more layers of polymer-based compounds in the wall, primarily for the purpose of improvement in permeation resistance to hydrocarbons found in various fuels. The construction can have a straight-wall configuration or can have a wall that is partially convoluted or corrugated. It may have an innermost layer with improved electrical conductivity for use where such a characteristic is desired; also, the improved electrical conductivity can apply to the entire wall construction, if the tubing is a monowall. This document is intended to cover tubing for any portion of a fuel system which operates above -40°C, and below 115°C, and up to a maximum working gage pressure of 690 kPa. The peak intermittent temperature is 115°C. For long-term continuous usage, the temperature shall not exceed 90°C.
In some cases, a distinction is made in the criteria that apply to tubing used to carry liquid fuel compared to tubing used to carry fuel vapor. The term "fuel vapor" can also apply to evaporative emissions and refers to a condition where the fuel content is in vapor form (very low concentration) and operated at a working gage pressure that does not exceed 17 kPa. The fuel vapor, or evaporative emissions, may contain small quantities of liquid fuel, which are present primarily as a result of vapor condensation.