Section XII provides rules that constitute requirements for construction and continued service of pressure vessels for the transportation of dangerous goods via highway, rail, air, or water. Construction is an all-inclusive term comprising materials, design, fabrication, examination, inspection, testing, certification, and over-pressure protection. Continued service is an all-inclusive term referring to inspection, testing, repair, alteration, and recertification of a transport tank that has been in service. The term pressure vessel refers to the pressure boundary defined by the geometric scope of this Section and includes, but is not limited to, the shell, heads, and openings. The term tank refers to the pressure vessel, appurtenances, and additional components that are covered by the Modal Appendices.

The rules of this Section apply specifically to pressure vessels intended for transporting dangerous goods with design pressures appropriate for the transportation mode and volumes greater than 450 L (120 gal).

Pressures normally incident to transportation, including loading and unloading operations, are to be considered.

Careful application of this Section will help users to comply with applicable regulations within their jurisdictions, while achieving the operational, cost and safety benefits to be gained from the many industry best-practices detailed within these volumes.