Dangerous Goods by Road
When additional protection against shell damage is provided, portable tanks with test pressures less
than 2.65 bar may have the minimum shell thickness reduced, in proportion to the protection provided,
as approved by the competent authority. However, shells not more than 1.80 m in diameter shall be
not less than 3 mm thick in the reference steel or of equivalent thickness in the metal to be used.
Shells more than 1.80 m in diameter shall be not less than 4 mm thick in the reference steel or of
equivalent thickness in the metal to be used.
The cylindrical portions, ends (heads) and manhole covers of all shells shall be not less than 3 mm
thick regardless of the material of construction.
The additional protection referred to in 6.7.2.4.3 may be provided by overall external structural
protection, such as suitable "sandwich" construction with the outer sheathing (jacket) secured to the
shell, double wall construction or by enclosing the shell in a complete framework with longitudinal
and transverse structural members.
In no case shall the wall thickness be less than that prescribed in 6.7.2.4.2, 6.7.2.4.3 and 6.7.2.4.4. All
parts of the shell shall have a minimum thickness as determined by 6.7.2.4.2 to 6.7.2.4.4. This
thickness shall be exclusive of any corrosion allowance.
When mild steel is used (see 6.7.2.1), calculation using the formula in 6.7.2.4.6 is not required.
There shall be no sudden change of plate thickness at the attachment of the ends (heads) to the
cylindrical portion of the shell.
Service equipment
Service equipment shall be so arranged as to be protected against the risk of being wrenched off or
damaged during handling and carriage. When the connection between the frame and the shell allows
relative movement between the sub-assemblies, the equipment shall be so fastened as to permit such
movement without risk of damage to working parts. The external discharge fittings (pipe sockets,
shut-off devices), the internal stop-valve and its seating shall be protected against the danger of being
wrenched off by external forces (for example using shear sections). The filling and discharge devices
(including flanges or threaded plugs) and any protective caps shall be capable of being secured against
unintended opening.
All openings in the shell, intended for filling or discharging the portable tank shall be fitted with a
manually operated stop-valve located as close to the shell as reasonably practicable. Other openings,
except for openings leading to venting or pressure-relief devices, shall be equipped with either a
stop-valve or another suitable means of closure located as close to the shell as reasonably practicable.
All portable tanks shall be fitted with a manhole or other inspection openings of a suitable size to
allow for internal inspection and adequate access for maintenance and repair of the interior.
Compartmented portable tanks shall have a manhole or other inspection openings for each
compartment.
As far as reasonably practicable, external fittings shall be grouped together. For insulated portable
tanks, top fittings shall be surrounded by a spill collection reservoir with suitable drains.
Each connection to a portable tank shall be clearly marked to indicate its function.
Each stop-valve or other means of closure shall be designed and constructed to a rated pressure not
less than the MAWP of the shell taking into account the temperatures expected during carriage. All
stop-valves with screwed spindles shall close by a clockwise motion of the handwheel. For other
stop-valves the position (open and closed) and direction of closure shall be clearly indicated. All
stop-valves shall be designed to prevent unintentional opening.