DOT UN or ISO tubes that are manufactured in accordance with 49 CFR 178.71(j) or ISO 11120 will have a retest cycle of 10-years provided they are carrying Division 2.1 (flammable) or 2.2 (non-flammable) gases (excepting CO2). The retest cycle is 5 years for Division 2.3 (toxic) gases. This 10-year retest comes from DOT and IMDG/UN/ADR regulations. FIBA performs requalification of these DOT UN tubes in accordance with 49 CFR 180.207. No tracking of fills is required. No 5-year visual examination is required. No special permit is required.
Today, 49 CFR 180.207 references ISO standard 6406. Since this relates only to small cylinders (0.5 to 150 L water capacity), FIBA is currently requalifying the tubes per DOT-SP 9847 or DOT-SP 10922, but for a retest cycle of 10-years. These two (2) permits authorize us to test DOT UN tubes manufactured per ISO 11120. FIBA intends to petition the DOT to get the regulations changed to allow requalification of ISO 11120 tubes by AE or UE without reference to ISO 6406. Additionally, ISO members are currently drafting a new standard that addresses the requalification of cylinders and tubes with a water capacity that is greater than 150 L.
DOT 3-Series tubes (e.g. 3A, 3AA, 3AX, 3AAX, 3T) can be requalified by hydrostatic test for a 5-year cycle without a special permit. To requalify by AE or UE, a special permit is required for a 5-year cycle. (We have DOT-SP 9847 for AE and DOT-SP 10922 for UE.) A special permit is also required for a 10-year cycle, in which case fill tracking and other requirements must be met, including a visual examination after 5 years, which is why we mark the equipment with a 5-year retest until the 5-year visual examination has been performed and passed and we have confirmed compliance with fill tracking requirements and completed an external visual examination of the tubes per CGA C-6. (For a 10-year requalification of DOT 3-Series tubes, FIBA has DOT-SP 14661 for AE and DOT-SP 14453 for UE.)
For dual-stamped tubes, testing shall be accomplished under the code that is applicable to the conditions and countries within which the owner or operator of the equipment is filling the equipment. For example, if the equipment is being filled in Korea or China, where DOT UN and ISO 11120 tubes are not recognized, then requalification will be in accordance with what is applicable to DOT 3-Series tubes. If the equipment is operating in the USA or Europe, where the UN and ISO 11120 tubes are accepted and referenced in regulations, then requalification will be in accordance with what is applicable to DOT UN pressure receptacles (i.e. 10 years if operating in a flammable or non-flammable gas service, excluding CO2). The operator is ultimately responsible for this decision and data plates must be marked accordingly.
It’s important to point out that a DOT UN tube is distinct by its UN marking and the mark of USA as the country of origin. FIBA is permitted to manufacture and requalify DOT UN tubes manufactured with the USA marking as well as the specifications of ISO 11120. Tubes manufactured outside of the USA per ISO 11120 (perhaps without the UN marking) will need special attention to confirm that the correct requalification method is being applied.