T23 is the IMDG Code Chapter 6.7.2.18 portable tank instruction for Class 4.1 self-reactive substances and Class 5.2 organic peroxides. Min test pressure 4 bar, but the defining features are not pressure-related: temperature sensors mounted on the shell, emergency-relief devices sized per UN entry, mandatory temperature-controlled transport with both control temperature and emergency temperature listed in IMDG 4.2.5.2.6 per UN, and a hard prohibition on fusible elements anywhere in the shell. Some UN entries cap the per-tank cargo mass at 2,000 kg.
What T23 is built for
The cargo population is organic peroxides used as polymerisation initiators, curing agents, and bleaching agents in the chemical and pharmaceutical industries. tert-Butyl hydroperoxide at 72% concentration or below (UN 3109), cumyl hydroperoxide (UN 3110), di-tert-butyl peroxide (UN 3107), dicumyl peroxide (UN 3108), peroxyacetic acid at 41% or below in hydrogen peroxide solution (UN 3105), and a small group of related peroxides. Class 4.1 self-reactive substances (Type F only) ship in similar equipment.
Construction and materials
316L stainless cylinder, 6 mm reference-steel shell, 100 mm polyurethane foam insulation typical (or “inorganic non-combustible” per IMDG TP17 special provision for cargoes that mandate it). Built-in temperature sensors mounted at the shell wall plus emergency-relief devices sized to vent the cargo’s runaway-decomposition mass flow. PRV regime varies by UN entry (some use frangible disc, others use spring-loaded PRV; IMDG 4.2.5.2.6 lists per-cargo). No bottom outlet. No fusible elements in the shell, because fusible elements would melt under the cargo’s exotherm and create a hazard worse than the original.
Degree of filling caps at 90% at 15 deg C per IMDG 4.2.1.13 (lower than the standard T-code 95% / 97% caps). The reduced fill makes room for cargo expansion under partial decomposition without venting through the relief device.
Capacity runs 8,000 to 22,000 L typical, with the smaller end of the range for cargoes that have the 2,000 kg per-tank mass cap.
When T23 is the right choice
T23 is the only legal route for organic peroxides and Class 4.1 self-reactive substances under IMDG portable-tank rules. The substitution rule of IMDG 4.2.5.2.5 does not apply to T23: a peroxide cargo cannot ride T11 or T22 even if those tanks look stronger on paper, because the temperature-control, emergency-relief, and no-fusible-elements rules are class-specific. If the assigned T-code is T23, the equipment must be a T23 build.
When T23 is the wrong choice
T23 is the wrong tank for any non-peroxide and non-self-reactive cargo. The temperature-control system and the emergency-relief device are dead weight elsewhere. T23 is also the wrong tank when the cargo’s IMDG entry mandates limited-quantity packaging or non-bulk shipment; some peroxides cannot ride portable tanks at all and must ship in IBCs or drums under specific TPxx provisions.
How to verify a T23 booking
Pre-loading inspection covers the standard plate stack (CSC, 5-year, 2.5-year) plus the temperature-sensor calibration record, the emergency-relief device sizing certificate, the operator’s history showing dedicated peroxide service, and the temperature-control system pre-cooling check (the cargo loads at or below the IMDG control temperature listed in 4.2.5.2.6 for the specific UN). The fleet is small and operator economics are tight; Eurotainer runs the largest commercial peroxide-tank fleet, with Stolt Tank Containers and a small number of regional specialists rounding out the market.