T9 is the IMDG Code Chapter 6.7 portable tank instruction at 4 bar test pressure with the 6 mm reference-steel shell explicitly required, no bottom outlet, and a frangible-disc plus tell-tale-gauge relief regime. T9 differs from T8 (which uses normal PRV) on the relief regime alone. Cargo population: high-hazard Class 6.1 toxics and Class 8 corrosives where the IMDG entry profile justifies the frangible disc.
What T9 is built for
The IMDG Dangerous Goods List assigns T9 to specific Class 6.1 PG II and Class 8 PG I/II UN entries where the cargo’s hazard profile demands a frangible-disc relief but the test pressure remains at 4 bar. The substitution rule allows T9 cargo to also ride T10, T13, T14, T19, T20, T21, T22.
Construction and materials
316L stainless cylinder with 6 mm reference shell explicitly required (vs the diameter-dependent rule for T1 to T8). Top discharge through a dip-pipe. Frangible disc plus tell-tale gauge mounted in series with the spring-loaded PRV at 4.4 bar.
When T9 is the right choice
T9 is the right tank when IMDG DGL Column 13 specifies T9 for the UN entry. The fleet is small; in practice many T9-eligible cargoes ride T14 (where the higher 6 bar test pressure adds margin without changing operational profile) because the T14 fleet is much bigger.
When T9 is the wrong choice
T9 is the wrong tank for cargoes that fit T11 (no frangible disc requirement, bigger fleet) or T14 (where the 6 bar test pressure is preferred and the operator inventory is bigger). T9 is also wrong for cargoes assigned to T19 / T20 / T22 where the higher hazard demands the 10 bar test pressure.