Fuel tank is an integral part of the fuel system in which fuel is stored and released into the engine. Fuel tanks range in size and complexity from the small plastic tank of a butane lighter to the multi-chambered cryogenic space shuttle external tank. Typically, a fuel tank must cover the functions such as filling, storage of fuel, gauging, venting and feeding of the engine through a pump. The tank must contain a given quantity of fuel and must avoid leakage and limit evaporative emissions. The remaining quantity of fuel in the tank must be measured or evaluated. If over-pressure is not allowed, the fuel vapors must be managed through valves.