What is the maximum allowable pressure in a fuel tank vent system?

The maximum allowable pressure in a fuel tank vent system is specified to be 80% of the tank's rated test pressure. This standard ensures that the tank can safely handle internal pressures due to fuel vapor and thermal expansion without exceeding its design limits. Operating at 80% of the rated test pressure provides an adequate safety margin to prevent potential ruptures or leaks.

While it is crucial that tanks are adequately vented to prevent pressure buildup during fueling and temperature changes, adhering to the 80% guideline ensures that structural integrity is maintained and minimizes the risk of failure. This ensures compliance with safety regulations and enhances the overall reliability of the tank’s operation.

The other options present either insufficient safety margins or unregulated pressure limits that could potentially compromise the integrity of the fuel system, which is why those choices do not meet the established safety standards in this context.