The NPROXX system involves fewer, bigger and more efficient pressure vessels, held in an advanced mounting structure.

This reduces the total number of pressure vessels required and increases the total volume of hydrogen that the tanks can store, thereby giving greater productivity while taking up less space.

NPROXX has developed an advanced mounting system to hold these vessels in place on top of the train.

Traditional roof-mounting systems either strap the vessels to the roof or embed them in a metal frame that itself holds them in place. NPROXX has created a new patented mounting system that is more efficient and stronger.

The cylindrical part of the pressure vessel has been extended over the roof dome to form an envelope shape, and the vessels are mounted on two metal endplates. This approach reduces the weight of the total structure including the supports. 

[출처] Gasworld, 2019.07.15

https://www.gasworld.com/nproxx-develops-hydrogen-tank-train-mountings/2017528.article