In no case shall the wall thickness be less than that prescribed in, and All
parts of the shell shall have a minimum thickness as determined by to This
thickness shall be exclusive of any corrosion allowance.

When mild steel is used (see, calculation using the formula in 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

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.

No moving parts, such as covers, components of closures, etc., shall be made of unprotected
corrodible steel when they are liable to come into frictional or percussive contact with aluminium
portable tanks intended for the carriage of substances meeting the flash-point criteria of Class 3
including elevated temperature substances carried at or above their flash-point.

Piping shall be designed, constructed and installed so as to avoid the risk of damage due to thermal
expansion and contraction, mechanical shock and vibration. All piping shall be of a suitable metallic
material. Welded pipe joints shall be used wherever possible.

Joints in copper tubing shall be brazed or have an equally strong metal union. The melting point of
brazing materials shall be no lower than 525 °C. The joints shall not decrease the strength of the
tubing as may happen when cutting threads.
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