Which system uses cascade style with 9-12 tubes per tube?

• A. DOT 406
• B. Dry Bulk Trailers
• C. High Pressure Tube
• D. Cryogenic Liquid tank car

Answer: (C)

High-pressure tube systems store compressed gas in a bank of rigid tubes arranged in a cascade. This design uses multiple tubes—typically around 9 to 12 in a group—so gas can be drawn from the highest-pressure tubes first and then from the next as supply continues, helping keep discharge pressure relatively steady. That cascade of tubes is what sets this system apart from other cargo designs.

The other options describe different modes of transport: one is a liquid cargo tank for flammable liquids, another is a trailer for dry powders carried pneumatically, and the cryogenic tank car carries very cold liquids in an insulated vessel. None of those use a cascade arrangement of many high‑pressure tubes.