UN Portable Tank T-Code Selection Matrix
Standard specification guidelines for 20ft ISO tank containers: cross-reference UN portable tank instructions (T1 to T22), minimum hydraulic test pressures, and bottom opening safety closures.
01 HazMat Commodity or T-Code
02 Mandatory Tank Container Build Specs
Internal foot valve + secondary butterfly valve + 3-inch blind flange or dust cap.
Set to open between 100% and 125% of MAWP.
Understanding UN Portable Tank Instructions (T1 to T22)
The International Maritime Dangerous Goods (IMDG) Code and US DOT 49 CFR Part 172 establish UN Portable Tank Instructions (T-Codes) to standardize multimodal liquid chemical shipping. A tank container certified for a higher instruction code may always be used to transport goods authorized for a lower instruction code, creating an upward compliance hierarchy.
Bottom Openings & Triple Containment
For moderate hazards (T4, T7, T11), bottom discharge is permitted only with three serially mounted independent closures: an internal stop-valve (foot valve), an external shutoff valve (clamped butterfly or ball valve), and a solid bolted blind flange or threaded cap. For high-hazard toxics (T10, T14, T22), all bottom openings are strictly illegal; product must be unloaded exclusively through top siphon dip pipes.
Rupture Discs in Series with Relief Valves
When transporting toxic or highly corrosive chemicals (such as methyl isocyanate or chlorosulfonic acid), spring-loaded relief valves cannot be exposed directly to product vapors because corrosive fumes cause weeping and mechanical spring deterioration. A frangible rupture disc must be installed upstream of the relief valve, equipped with a tell-tale pressure gauge to detect disc pinholes.
Enterprise ISO Tank Intermodal Dispatch Automation
Exspeedite TMS prevents costly terminal rejections and federal HazMat citations by cross-referencing UN numbers against assigned container CSC plates. The system verifies that container test pressure ratings and valve configurations satisfy 49 CFR § 172.102 special provisions before dispatching drayage trucks to rail ramps or maritime port terminals.