The 40 ft ISO tank frame (designation 1AAA under ISO 668:2020) is the cryogenic-cargo standard. Outer dimensions 12,192 mm x 2,438 mm x 2,591 mm. Holds the 45,500 L LNG build, the 48,400 L LH2 build (Linde Engineering and Chart Industries), the refrigerated ethylene fleet, and the small liquid-helium fleet. Tare 12,500 to 13,500 kg dominated by the vacuum-insulated double-wall shell construction; payload 23,000 to 24,000 kg of cryogenic cargo at typical fill ratios.
What 40ft is built for
Cryogenic refrigerated gases shipped intermodally. LNG UN 1972 (-162 deg C) is the largest 40 ft cryogenic fleet. LH2 UN 1966 (-253 deg C) is the rapidly developing fuel-and-energy-distribution fleet, with Linde Engineering’s first ferry-mounted LH2 system commissioned in 2023. Refrigerated ethylene UN 1038 for petrochemical feedstock distribution. Liquid helium UN 1963 in small dedicated fleets for medical and research applications.
The 40 ft frame matters for cryogenic specifically because the cargoes are low-density (LNG 0.42 kg/L; LH2 0.071 kg/L) and the tank operating economics need the larger volume to make per-tonne shipping costs work. A 20 ft cryogenic at 21,500 L of LNG would carry only 9 tonnes; the 40 ft at 45,500 L carries about 19 tonnes, which is closer to the IMDG fill cap times the MGW limit.
Construction and materials
Vacuum-insulated double-wall construction. Inner vessel typically 304L stainless steel for LIN / LOX / LAR / LCO2 / ethylene service, or aluminium 5086 for LH2 (where stainless-steel embrittlement at minus 253 deg C is a concern). Outer jacket 304 stainless or carbon steel painted. Annular space between inner and outer evacuated to ultrahigh vacuum, with multi-layer perlite or aluminised mylar superinsulation. No bottom outlet; all cargo connections route through the top via a valve cabinet. Pressure-build coil inside the inner vessel for self-pressurising discharge.
The 2,200 mm shell outer-diameter figure in the spec block above refers to the vacuum-jacketed inner vessel. The outer jacket sits at around 2,400 mm to fit the 1AAA frame outer width (2,438 mm) with clearance for jacket insulation and external fittings. Chart Industries and Linde 40 ft LNG / LH2 datasheets typically report the inner-vessel OD because that is the dimension that drives capacity math.
When 40ft is the right choice
40 ft is the right frame for cryogenic refrigerated gas shipment. It is the only practical frame size for LNG and LH2 intermodal logistics; the 20 ft variants exist but are economically marginal for these cargoes.
When 40ft is the wrong choice
40 ft is the wrong frame for non-cryogenic chemical service. Almost no chemical or food-grade T11 / T14 builds use the 40 ft frame because the smaller 20 ft frame fits the cargo density and fleet rotation economics better. Some specialty very-low-density cargoes might justify 40 ft chemical builds but these are exceptional.
Frame interface specifications
Outer length 12,192 mm. Outer width 2,438 mm. Outer height 2,591 mm (1AAA); 9’6” high cube variant exists at 2,896 mm but is uncommon for cryogenic service because the high-cube height makes the centre-of-gravity calculations harder for the heavier cryogenic cargoes. Corner castings per ISO 1161. Vessel stowage in two consecutive 20 ft slots; lift via top corner castings only (the cryogenic mass distribution makes side-fork-pocket lifting unsafe).