Requirements for the design, construction, inspection and testing of portable tanks intended for the carriage of substances of Class 1 and Classes 3 to 9

Definitions

For the purposes of this section:
Alternative arrangement means an approval granted by the competent authority for a portable tank or
MEGC that has been designed, constructed or tested to technical requirements or testing methods
other than those specified in this Chapter:
Portable tank means a multimodal tank used for the carriage of substances of Class 1 and Classes 3 to
9. The portable tank includes a shell fitted with service equipment and structural equipment necessary
for the carriage of dangerous substances. The portable tank shall be capable of being filled and
discharged without the removal of its structural equipment. It shall possess stabilizing members
external to the shell, and shall be capable of being lifted when full. It shall be designed primarily to be
loaded onto a vehicle, wagon or sea-going or inland navigation vessel and shall be equipped with
skids, mountings or accessories to facilitate mechanical handling. Tank-vehicles, tank-wagons,
non-metallic tanks and intermediate bulk containers (IBCs) are not considered to fall within the
definition for portable tanks;
Shell means the part of the portable tank which retains the substance intended for carriage (tank
proper), including openings and their closures, but does not include service equipment or external
structural equipment;
Service equipment means measuring instruments and filling, discharge, venting, safety, heating,
cooling and insulating devices;
 
Structural equipment means the reinforcing, fastening, protective and stabilizing members external to
the shell;
Maximum allowable working pressure (MAWP) means a pressure that shall be not less than the
highest of the following pressures measured at the top of the shell while in operating position:
(a) The maximum effective gauge pressure allowed in the shell during filling or discharge; or
(b) The maximum effective gauge pressure to which the shell is designed which shall be not less
than the sum of:
(i) the absolute vapour pressure (in bar) of the substance at 65 °C, minus 1 bar; and
(ii) the partial pressure (in bar) of air or other gases in the ullage space being determined by
a maximum ullage temperature of 65 °C and a liquid expansion due to an increase in
mean bulk temperature of tr - tf (tf = filling temperature, usually 15 °C; tr = maximum
mean bulk temperature, 50 °C);
Design pressure means the pressure to be used in calculations required by a recognized pressure
vessel code. The design pressure shall be not less than the highest of the following pressures:
(a) The maximum effective gauge pressure allowed in the shell during filling or discharge; or
(b) The sum of:
(i) the absolute vapour pressure (in bar) of the substance at 65 °C, minus 1 bar;
(ii) the partial pressure (in bar) of air or other gases in the ullage space being determined by
a maximum ullage temperature of 65 °C and a liquid expansion due to an increase in
mean bulk temperature of tr - tf (tf = filling temperature usually 15 °C; tr = maximum
mean bulk temperature, 50 °C); and
(iii) a head pressure determined on the basis of the static forces specified in 6.7.2.2.12, but
not less than 0.35 bar; or
(c) Two thirds of the minimum test pressure specified in the applicable portable tank instruction
in 4.2.5.2.6;
Test pressure means the maximum gauge pressure at the top of the shell during the hydraulic pressure
test equal to not less than 1.5 times the design pressure. The minimum test pressure for portable tanks
intended for specific substances is specified in the applicable portable tank instruction in 4.2.5.2.6;
Leakproofness test means a test using gas subjecting the shell and its service equipment to an effective
internal pressure of not less than 25% of the MAWP;
Maximum permissible gross mass (MPGM) means the sum of the tare mass of the portable tank and
the heaviest load authorized for carriage;
Reference steel means a steel with a tensile strength of 370 N/mm2 and an elongation at fracture
of 27%;
Mild steel means a steel with a guaranteed minimum tensile strength of 360 N/mm2 to 440 N/mm2 and
a guaranteed minimum elongation at fracture conforming to 6.7.2.3.3.3;
Design temperature range for the shell shall be -40 °C to 50 °C for substances carried under ambient
conditions. For the other substances handled under elevated temperature conditions the design
temperature shall be not less than the maximum temperature of the substance during filling, discharge
or carriage. More severe design temperatures shall be considered for portable tanks subjected to
severe climatic conditions;
Fine grain steel means steel which has a ferritic grain size of 6 or finer when determined in
accordance with ASTM E 112-96 or as defined in EN 10028-3, Part 3;
Fusible element means a non-reclosable pressure relief device that is thermally actuated;
 
Offshore portable tank means a portable tank specially designed for repeated use for carriage to, from
and between offshore facilities. An offshore portable tank is designed and constructed in accordance
with the guidelines for the approval of containers handled in open seas specified by the International
Maritime Organization in document MSC/Circ.860.

General design and construction requirements

Shells shall be designed and constructed in accordance with the requirements of a pressure vessel code
recognized by the competent authority. Shells shall be made of metallic materials suitable for forming.
The materials shall in principle conform to national or international material standards. For welded
shells only a material whose weldability has been fully demonstrated shall be used. Welds shall be
skilfully made and afford complete safety. When the manufacturing process or the materials make it
necessary, the shells shall be suitably heat-treated to guarantee adequate toughness in the weld and in
the heat affected zones. In choosing the material, the design temperature range shall be taken into
account with respect to risk of brittle fracture, to stress corrosion cracking and to resistance to impact.
When fine grain steel is used, the guaranteed value of the yield strength shall be not more than
460 N/mm2 and the guaranteed value of the upper limit of the tensile strength shall be not more than
725 N/mm2 according to the material specification. Aluminium may only be used as a construction
material when indicated in a portable tank special provision assigned to a specific substance in
Column (11) of Table A of Chapter 3.2 or when approved by the competent authority. When
aluminium is authorized, it shall be insulated to prevent significant loss of physical properties when
subjected to a heat load of 110 kW/m2 for a period of not less than 30 minutes. The insulation shall
remain effective at all temperatures less than 649 °C and shall be jacketed with a material with a
melting point of not less than 700 °C. Portable tank materials shall be suitable for the external
environment in which they may be carried.

Portable tank shells, fittings, and pipework shall be constructed from materials which are:
(a) Substantially immune to attack by the substance(s) intended to be carried; or
(b) Properly passivated or neutralized by chemical reaction; or
(c) Lined with corrosion-resistant material directly bonded to the shell or attached by equivalent
means.

Gaskets shall be made of materials not subject to attack by the substance(s) intended to be carried.

When shells are lined, the lining shall be substantially immune to attack by the substance(s) intended
to be carried, homogeneous, non porous, free from perforations, sufficiently elastic and compatible
with the thermal expansion characteristics of the shell. The lining of every shell, shell fittings and
piping shall be continuous, and shall extend around the face of any flange. Where external fittings are
welded to the tank, the lining shall be continuous through the fitting and around the face of external
flanges.

Joints and seams in the lining shall be made by fusing the material together or by other equally
effective means.

Contact between dissimilar metals which could result in damage by galvanic action shall be avoided.

The materials of the portable tank, including any devices, gaskets, linings and accessories, shall not
adversely affect the substance(s) intended to be carried in the portable tank.

Portable tanks shall be designed and constructed with supports to provide a secure base during
carriage and with suitable lifting and tie-down attachments.

Portable tanks shall be designed to withstand, without loss of contents, at least the internal pressure
due to the contents, and the static, dynamic and thermal loads during normal conditions of handling
and carriage. The design shall demonstrate that the effects of fatigue, caused by repeated application
of these loads through the expected life of the portable tank, have been taken into account.

For portable tanks that are intended for use offshore, the dynamic stresses imposed by handling in
open seas shall be taken into account.

A shell which is to be equipped with a vacuum-relief device shall be designed to withstand, without
permanent deformation, an external pressure of not less than 0.21 bar above the internal pressure. The
vacuum-relief device shall be set to relieve at a vacuum setting not greater than minus (-) 0.21 bar
unless the shell is designed for a higher external over pressure, in which case the vacuum-relief
pressure of the device to be fitted shall be not greater than the tank design vacuum pressure. A shell
used for the carriage of solid substances (powdery or granular) of packing groups II or III only, which
do not liquefy during carriage, may be designed for a lower external pressure, subject to the approval
of the competent authority. In this case, the vacuum valve shall be set to relieve at this lower pressure.
A shell that is not to be fitted with a vacuum-relief device shall be designed to withstand, without
permanent deformation an external pressure of not less than 0.4 bar above the internal pressure.

Vacuum-relief devices used on 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, shall prevent the immediate passage of flame into the shell, or the portable tank shall have
a shell capable of withstanding, without leakage an internal explosion resulting from the passage of
flame into the shell.
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