T22 is the heaviest standard portable tank in the IMDG T1 to T22 ladder. 10 bar test pressure, 10 mm reference-steel shell (about 6.96 mm in 316L per the Lloyd’s formula), no bottom outlet, frangible-disc relief. ASME VIII Div 2 with the U-stamp is mandatory for ocean carriage under 49 CFR 178.275. The cargo population is highest-class organometallics, fluorination products, and Hazard Zone A or B toxic-by-inhalation substances. The substitution rule of IMDG 4.2.5.2.5 makes T22 the universal “stronger” tank: any T1 to T21 cargo can ride T22, but no T22 cargo can be substituted into a weaker code.
What T22 is built for
The IMDG Dangerous Goods List Column 13 assigns T22 to substances where every parameter is at the strict end: high test pressure, thick shell, no bottom outlet, frangible disc. Examples include certain Class 6.1 inhalation-hazard substances (Hazard Zone A or B), specific fluorination intermediates, and highest-class organometallics that don’t meet the pyrophoric category of T21. The 49 CFR 178.275 mandate of an ASME U-stamp is unique among the T-codes (most T-codes treat the U-stamp as optional); T22 makes it explicit.
Construction and materials
316L stainless cylinder is the standard build. For specific fluorination chemistry where stainless fails (anhydrous HF, fluorine gas dissolved in solvent, certain perfluorinated intermediates) the shell uses Hastelloy or tantalum cladding. 10 mm reference-steel shell is the thickest in the T1 to T22 series, paired with a 50 to 100 mm polyurethane insulation under aluminium cladding. Manlid bolted with PTFE-gasketed M24 fasteners. Top-only fittings: dip-pipe discharge, vapour return, primary PRV, secondary frangible disc with tell-tale gauge, sample valve, thermometer well.
Tare runs 4,500 to 5,500 kg, 500 to 1,000 kg above an equivalent T11 because of the thicker shell. Payload 30 to 31 tonnes. Typical capacity 18,000 L, smaller than T11 because the cargoes are dense and the smaller volume keeps the weight cap above the 80% IMDG surge floor.
When T22 is the right choice
T22 is the right tank when IMDG DGL Column 13 specifies T22 for the UN entry. It is also the universal substitution upgrade: any cargo with a T-code from T1 to T21 may also ride T22 (per IMDG 4.2.5.2.5). In practice no operator books a T22 to carry a T11 cargo because the lease rate is 3 to 4 times higher and the fleet inventory is small.
When T22 is the wrong choice
T22 is the wrong tank for any cargo that doesn’t need it. The over-engineered shell, the ASME U-stamp build cost, and the small fleet inventory all push lease rates and lead times up. T22 is also the wrong tank for liquefied gases (T50) and cryogenic cargoes (T75), which are family-specific and don’t substitute through the T1 to T22 ladder.
How to verify a T22 booking
Pre-loading inspection covers the standard plate stack (CSC, 5-year hydraulic, 2.5-year intermediate) plus the ASME U-stamp on the data plate (mandatory, not optional). The frangible-disc tell-tale gauge is verified visually for prior rupture. For Hastelloy or tantalum-clad builds the lining condition is checked through the manlid opening and the operator’s certificate of clad-build conformity is required. Lead time on this fleet is the longest in the standard liquid-tank ladder (180 to 240 days new build), so spot-market availability is thin and most bookings work through pre-positioned operator inventory at major ports.