Composite/Novel Media Portable Tank Specifications (27)
Criticality: Medium
Progress: Addressed, Not Adequately
Score: 12
DOT Relevance: §178
Description of Key Area
DOT requires that non-liquefied compressed gases be shipped in
specification containers. Composite cylinders are not included in DOT cylinder
specifications. Therefore, composite cylinders are only allowed in service by
obtaining a special permit in accordance with 49 CFR 107 Subpart B. Section 178
Subpart H deals specifically with portable tank specifications, which contain
liquefiable gases with a liquid/gas interface.
Discussion of Criticality
Fluids held in §178 Subpart H portable tanks must currently be
made of steel with welded construction in accordance with ASME Section VIII.
Portable tanks are held at relatively low pressures, which would imply storage
of hydrogen would be cryogenic or in the form of a solution or chemical
hydride. Light weight is one consideration for portable tanks, so that they can
be transported more easily. Composite tanks are lighter in weight than steel
tanks, although this would be less significant with liquefied contents at lower
pressures. Consideration must be given to temperature compatibility of
composite materials, to thermal stresses in the composite tank, and dynamic
loads.
Composite tanks have been used in cryogenic applications, but
their use in transportation is insignificant. Composite tanks have been used to
transport liquids, but these have generally been at low internal pressure.
Discussion of Progress
DOT currently has no composite portable tank standards. Composite
tanks have been developed for containing pressurized liquid hydrogen, but their
use in transportation has been limited. Composite tanks for liquids are
generally not at high pressure. There is likely insufficient transportation
experience with portable composite tanks to deal with standards development at
this time.
ASME's Boiler and Pressure Vessel project team on hydrogen tanks
is addressing high pressure gas storage in metal and composite tanks. The work
plan includes a proposed new article KD-10 to Section VIII-3, a code case on
composite tanks for Section VIII-3, and a revision to code case 2390 on metal
lined composite reinforced circumferentially wrapped pressure vessels under
Section VIII-3. Transport tanks may also be included in Section XII.
Recommendations
The industry and DOT should monitor the need for composite
portable tanks. Design studies may be required to assess the practicality of
using composite portable tanks to transport hydrogen or hydrogen compounds. DOT
should address any applications with special permits until a sufficient data
base of use exists and a larger market need exists.
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