Special requirements applicable to Class 2
Construction of shells
Shells intended for the carriage of compressed or liquefied gases or dissolved gases shall be made of
steel. In the case of weldless shells, by derogation from 18.104.22.168.12 a minimum elongation at fracture of
14% and also a stress σ lower than or equal to limits hereafter given according to the material may be
(a) When the ratio Re/Rm (of the minimum guaranteed characteristics after heat treatment) is
higher than 0.66 without exceeding 0.85:
σ ≤ 0.75 Re;
(b) When the ratio Re/Rm (of the minimum guaranteed characteristics after heat treatment) is
higher than 0.85:
σ ≤ 0.5 Rm.
The requirements of 6.8.5 apply to the materials and construction of welded shells.
Construction of battery-vehicles and MEGCs
Cylinders, tubes, pressure drums and bundles of cylinders, as elements of a battery-vehicle or MEGC,
shall be constructed in accordance with Chapter 6.2.
NOTE 1: Bundles of cylinders which are not elements of a battery-vehicle or of a MEGC shall be
subject to the requirements of Chapter 6.2.
NOTE 2: Tanks as elements of battery-vehicles and MEGCs shall be constructed in accordance with
22.214.171.124 and 126.96.36.199.
NOTE 3: Demountable tanks14 are not to be considered elements of battery-vehicles or MEGCs.
Elements and their fastenings
of battery vehicles
and the frame of MEGCs
Under each force the stress at the most severely stressed point of the element and its fastenings shall
not exceed the value defined in 188.8.131.52 for cylinders, tubes, pressure drums and bundles of cylinders
and for tanks the value of σ defined in 184.108.40.206.16.
Items of equipment
The discharge pipes of tanks shall be capable of being closed by blank flanges or some other equally
reliable device. For tanks intended for the carriage of refrigerated liquefied gases, these blank flanges
or other equally reliable devices may be fitted with pressure-release openings of a maximum diameter
of 1.5 mm.
Shells intended for the carriage of liquefied gases may be provided with, in addition to the openings
prescribed in 220.127.116.11.2 and 18.104.22.168.4, openings for the fitting of gauges, thermometers, manometers
and with bleed holes, as required for their operation and safety.
The internal stop-valve of all filling and all discharge openings of tanks
with a capacity greater than 1 m3
intended for the carriage of liquefied flammable or toxic gases shall be instant-closing and shall close
automatically in the event of an unintended movement of the tank or in the event of fire. It shall also
be possible to operate the internal stop-valve by remote control.
However on tanks intended for the carriage of
liquefied non-toxic flammable gases, the
internal stop-valve with remote control may be
replaced by a non-return valve for filling
openings into the vapour phase of the tank
only. The non-return valve shall be positioned
internally in the tank, be spring loaded so that
the valve is closed if the pressure in the filling
line is equal to or lower than the pressure in
the tank and be equipped with appropriate
All openings, other than those accommodating safety valves and closed bleed holes, of tanks intended
for the carriage of liquefied flammable and/or toxic gases shall, if their nominal diameter is more than
1.5 mm, shall be equipped with an internal shut-off device.
Notwithstanding the requirements of 22.214.171.124.2, 126.96.36.199.3 and 188.8.131.52.4, tanks intended for the carriage
of refrigerated liquefied gases may be equipped with external devices in place of internal devices if
the external devices afford protection against external damage at least equivalent to that afforded by
the wall of the shell.
If the tanks are equipped with gauges in direct contact with the substance carried, the gauges shall not
be made of a transparent material. If there are thermometers, they shall not project directly into the gas
or liquid through the shell.
14 For the definition of "demountable tank" see 1.2.1.
15 The use of metal to metal sealing is not permitted.
Filling and discharge openings situated in the upper part of tanks shall be equipped with, in addition to
what is prescribed in 184.108.40.206.3, a second, external, closing device. This device shall be capable of
being closed by a blank flange or some other equally reliable device.