Valves in the EVAP System
Valves in the fuel system are necessary in order to be able to meet the strict global emission and diagnostic requirements. They must meet very demanding functional requirements, especially with regard to leakage, resistance and stability.
In particular - but not only - for use with pressurized fuel tanks, which are commonly used in plug-in hybrid vehicles (PHEV), a tank shut-off valve (also known as Fuel Tank Isolation Valve or FTIV) is required to prevent the undesired start of the combustion engine in electric driving mode to purge the charcoal canister. The installation location is usually between the tank and the canister. In addition, a shut-off valve between the canister and the ambient is required for leak diagnosis.
With the Fuel Tank Isolation Valve, a valve is available that represents the benchmark for this valve class in terms of size and weight and meets the challenging functional requirements of all vehicle manufacturers. The standard version of the valve is normally closed and contains two integrated mechanical bypass valves to avoid unsafe values of pressure or vacuum in the fuel tank. The opening points of the bypasses are adjusted according to customer-specific requirements. Large flow cross-sections allow quick ventilation of the tank and a patented flow limiter can restrict the flow to a specified permissible value if necessary. The patented sealing system allows extremely low leakage values.
Depending on the requirements of the architecture of the fuel system, other versions are available, such as an "FTIV Light" without a flow limiter or a normally open variant. The application is not limited to systems with pressurized tanks, but possible universally.
Without the mechanical protection valves and the flow limiter, the normally open version can be used as a ventilation valve in all systems.