T Code System Classifications for ISO Tank Containers

The IMO classifications for ISO Tank Containers has been replaced by the ‘T’ code system.

The T-Code system specifies the test pressure of each type of tank container, its shell thickness, the pressure relief set-up and the bottom and top outlet arrangement. T-Code instructions apply to dangerous goods in classes 1 and 3 through 9. Class 2.

The T-Code system for tank containers was introduced in 2001. The T-Code system identifies tank containers from T1 through T22 and identifies the type of cargoes each container is designed to carry.

ISO tank containers have to be manufactured in accordance with strict international codes fCryogenic Tank Container T70or worldwide carriage of by liquids whether by land or sea.

Whilst the following isn’t a complete listing of the IMO types, it provides an indication of the original system of classification.

IMO Type 1 – Hazardous Tanks – approved for transportation of substances of Class 1 and Classes 3 through 9 where the liquids have a flashpoint of less than 0°C. Some examples of the types of liquids include explosives, flammable liquids, corrosive and toxic substances.

IMO Type 2 – Low Hazardous Tanks – approved for transportation of Class 3 substances that have a flashpoint of 0 – 61°C. Some examples of combustible liquids include diesel and cooking oils.

IMO Type 5 – Gas Tanks –  approved for transport of non-refrigerated liquefied gases of Class 2.

For reference, IMO stands for International Maritime Dangerous Goods Code.

T Code System for ISO Tank Containers and specifications:

T-Code Minimum Test Pressure (bar) Minimum Shell Thickness Pressure-Relief Requirements Bottom Opening Requirements
T1 1.5 > or = 6mm normal 2 shut-off devices (Int + Ext)
T2 1.5 > or = 6mm normal 3 shut-off devices (Int + Ext + cap/blank)
T3 2.65 > or = 6mm normal 2 shut-off devices (Int + Ext)
T4 2.65 > or = 6mm normal 3 shut-off devices (Int + Ext + cap/blank)
T5 2.65 > or = 6mm normal + rupture disc Not Allowed
T6 4 > or = 6mm normal 2 shut-off devices (Int + Ext)
T7 4 > or = 6mm normal 3 shut-off devices (Int + Ext + cap/blank)
T8 4 > or = 6mm normal Not Allowed
T9 4 6mm normal Not Allowed
T10 4 6mm normal + rupture disc Not Allowed
T11 6 > or = 6mm normal 3 shut-off devices (Int + Ext + cap/blank)
T12 6 > or = 6mm normal + rupture disc 3 shut-off devices (Int + Ext + cap/blank)
T13 6 6mm normal Not Allowed
T14 6 6mm normal + rupture disc Not Allowed
T15 10 >or = 6mm normal 3 shut-off devices (Int + Ext + cap/blank)
T16 10 > or = 6mm normal + rupture disc <3 shut-off devices (Int + Ext + cap/blank)/td>
T17 10 6mm normal 3 shut-off devices (Int + Ext + cap/blank)
T18 10 6mm normal + rupture disc Not Allowed
T19 10 6mm normal + rupture disc 3 shut-off devices (Int + Ext + cap/blank)
T20 10 8mm normal + rupture disc Not Allowed
T21 10 10mm normal Not Allowed
T22 10 10mm normal + rupture disc Not Allowed

In addition to the above types of ISO tank container, there are 2 others, namely, a T50 and a T70.

The T50 is a gas tank and has a minimum test pressure of 57.6 bar. Under the IMO system, this was classified IMO5.

The T70 is a cryogenic tank container designed for carrying liquefied gases. Under the IMO system, this was classified IMO7.

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