How must any unused opening in a tank be closed?

Closing any unused opening in a tank with a vapor tight threaded plug or cap is required to ensure safety and to prevent any potential leaks of fuel or vapors into the environment. Vapor tight closures effectively seal the opening, which helps maintain the pressure within the tank and mitigates the risk of fire hazards or exposure to harmful substances. Additionally, this method complies with industry standards and regulatory requirements related to the storage and handling of fuels.

Rubber stoppers, duct tape, and metal clamps may not provide the necessary seal integrity required for fuel tanks. Rubber stoppers can degrade over time and may not provide a reliable seal against vapor release. Duct tape is not a suitable long-term solution as it can easily peel away, lose adhesion, or become compromised due to temperature and environmental factors. Metal clamps may secure other types of connections, but they do not inherently create a vapor-tight seal and are subject to corrosion and wear. Overall, using a vapor tight threaded plug or cap is the most effective and compliant method for closing unused openings in tanks.