Dangerous Goods by Road
Portable tanks and their fastenings shall, under the maximum permissible load, be capable of
absorbing the following separately applied static forces:
(a) In the direction of travel: twice the MPGM multiplied by the acceleration due to gravity (g)1;
(b) Horizontally at right angles to the direction of travel: the MPGM (when the direction of travel
is not clearly determined, the forces shall be equal to twice the MPGM) multiplied by the
acceleration due to gravity (g)1;
(c) Vertically upwards: the MPGM multiplied by the acceleration due to gravity (g) 1; and
(d) Vertically downwards: twice the MPGM (total loading including the effect of gravity)
multiplied by the acceleration due to gravity (g)1.
Under each of the forces in 6.7.2.2.12, the safety factor to be observed shall be as follows:
(a) For metals having a clearly defined yield point, a safety factor of 1.5 in relation to the
guaranteed yield strength; or
(b) For metals with no clearly defined yield point, a safety factor of 1.5 in relation to the
guaranteed 0.2% proof strength and, for austenitic steels, the 1% proof strength.
The values of yield strength or proof strength shall be the values according to national or international
material standards. When austenitic steels are used, the specified minimum values of yield strength or
proof strength according to the material standards may be increased by up to 15% when these greater
values are attested in the material inspection certificate. When no material standard exists for the
metal in question, the value of yield strength or proof strength used shall be approved by the
competent authority.
Portable tanks shall be capable of being electrically earthed when 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. Measures shall be taken to prevent dangerous electrostatic
discharge.
When required for certain substances by the applicable portable tank instruction indicated in
Column (10) of Table A of Chapter 3.2 and described in 4.2.5.2.6 or by a portable tank special
provision indicated in Column (11) of Table A of Chapter 3.2 and described in 4.2.5.3, portable tanks
shall be provided with additional protection, which may take the form of additional shell thickness or
a higher test pressure, the additional shell thickness or higher test pressure being determined in the
light of the inherent risks associated with the carriage of the substances concerned.
Thermal insulation directly in contact with the shell intended for substances carried at elevated
temperature shall have an ignition temperature at least 50 °C higher than the maximum design
temperature of the tank.
For calculation purposes g = 9.81 m/s2.
Design criteria
Shells shall be of a design capable of being stress-analysed mathematically or experimentally by
resistance strain gauges, or by other methods approved by the competent authority.
Shells shall be designed and constructed to withstand a hydraulic test pressure not less than 1.5 times
the design pressure. Specific requirements are laid down for certain substances in the applicable
portable tank instruction indicated in Column (10) of Table A of Chapter 3.2 and described in
4.2.5.2.6 or by a portable tank special provision indicated in Column (11) of Table A of Chapter 3.2
and described in 4.2.5.3. Attention is drawn to the minimum shell thickness requirements specified in
6.7.2.4.1 to 6.7.2.4.10.
(0.2% proof strength, generally, or 1% proof strength for austenitic steels) the primary membrane
stress σ (sigma) in the shell shall not exceed 0.75 Re or 0.50 Rm, whichever is lower, at the test
pressure, where:
Re = yield strength in N/mm2, or 0.2% proof strength or, for austenitic steels, 1% proof
strength;
Rm = minimum tensile strength in N/mm2.
The values of Re and Rm to be used shall be the specified minimum values according to national or
international material standards. When austenitic steels are used, the specified minimum values for Re
and Rm according to the material standards may be increased by up to 15% when greater values are
attested in the material inspection certificate. When no material standard exists for the metal in
question, the values of Re and Rm used shall be approved by the competent authority or its authorized
body.
Steels which have a Re/Rm ratio of more than 0.85 are not allowed for the construction of welded
shells. The values of Re and Rm to be used in determining this ratio shall be the values specified in
the material inspection certificate.
Steels used in the construction of shells shall have an elongation at fracture, in %, of not less
than 10 000/Rm with an absolute minimum of 16% for fine grain steels and 20% for other steels.
Aluminium and aluminium alloys used in the construction of shells shall have an elongation at
fracture, in %, of not less than 10 000/6Rm with an absolute minimum of 12%.
For the purpose of determining actual values for materials, it shall be noted that for sheet metal, the
axis of the tensile test specimen shall be at right angles (transversely) to the direction of rolling. The
permanent elongation at fracture shall be measured on test specimens of rectangular cross sections in
accordance with ISO 6892:1998 using a 50 mm gauge length.