UN-DOT-3AX-2538 40' ISO Frame Tube Trailer — 660 cu ft, 2,650 PSIG

Is this ASME or DOT rated, and what does that allow me to do with it?

This is DOT rated to UN-DOT-3AX-2538 specification, which allows transport of compressed hydrogen over public roads in the United States and in countries recognizing UN portable tank standards. DOT certification is required for any cylinder or container moving in commerce; ASME vessels are stationary installations. The ISO frame design allows standard intermodal handling—ship, rail, or truck—without offloading the gas.

What is the requalification or inspection status?

The listing does not provide requalification or last inspection dates. DOT-3AX cylinders typically require requalification every 5 years from date of manufacture or last requalification, and this 2015-built unit would be due or overdue depending on its service history. Request documentation showing the most recent hydrostatic test, visual inspection, and any valve or fitting replacements performed during requalification.

What should I inspect before putting it into service?

Verify current DOT requalification status and ensure the stamped retest date on each cylinder bundle is within the allowable service window. Inspect all manifold connections, pressure relief devices, and valves for corrosion, damage, or evidence of leakage; hydrogen embrittlement at fittings is a particular concern on units that have seen thermal cycling. Check the ISO frame structural welds and corner castings for cracks or deformation, and confirm that all required placarding and specification markings are legible.