metal tank

Evaporative emissions (EVAP) compliance for metal fuel tanks is no longer merely a matter of quality assurance—it is a matter of market access. Starting with the 2000 model year, both the U.S. Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) have mandated that OBD II systems must be capable of detecting system leaks equivalent to a hole larger than 0.5 millimeters (0.020 inches) in diameter. This regulatory threshold imposes stringent requirements on the manufacturing process of custom metal fuel tanks: any welding porosity—that is, gas voids trapped within the weld pool during solidification—can form microscopic vapor pathways, triggering P0456 or P0442 fault codes when the vehicle is started. Traditional hydrostatic testing relies on water as the pressurizing medium, but its resolution is insufficient to reveal these sub-millimeter defects; surface tension effects often mask minute leaks that would otherwise allow vapor to escape under the influence of fuel vapor pressure. For a metal fuel tank to pass certification, […]