Dangerous Goods by Road
The pressure-relief devices shall consist of spring-loaded valves fitted to prevent significant build-up
within the portable tank of the decomposition products and vapours released at a temperature of
50 °C. The capacity and start-to-discharge pressure of the relief valves shall be based on the results of
the tests specified in 4.2.1.13.1. The start-to-discharge pressure shall, however, in no case be such that
liquid would escape from the valve(s) if the portable tank were overturned.
The emergency-relief devices may be of the spring-loaded or frangible types, or a combination of the
two, designed to vent all the decomposition products and vapours evolved during a period of not less
than one hour of complete fire-engulfment as calculated by the following formula:
The start-to-discharge pressure of the emergency-relief device(s) shall be higher than that specified
in 4.2.1.13.7 and based on the results of the tests referred to in 4.2.1.13.1. The emergency-relief
devices shall be dimensioned in such a way that the maximum pressure in the portable tank never
exceeds the test pressure of the tank.
NOTE: An example of a method to determine the size of emergency-relief devices is given in
Appendix 5 of the "Manual of Tests and Criteria".
For insulated portable tanks the capacity and setting of emergency-relief device(s) shall be determined
assuming a loss of insulation from 1% of the surface area.
Vacuum-relief devices and spring-loaded valves shall be provided with flame arresters. Due attention
shall be paid to the reduction of the relief capacity caused by the flame arrester.
Service equipment such as valves and external piping shall be so arranged that no substance remains
in them after filling the portable tank.
Portable tanks may be either insulated or protected by a sun-shield. If the SADT of the substance in
the portable tank is 55 °C or less, or the portable tank is constructed of aluminium, the portable tank
shall be completely insulated. The outer surface shall be finished in white or bright metal.
The degree of filling shall not exceed 90% at 15 °C.
The mark as required in 6.7.2.20.2 shall include the UN number and the technical name with the
approved concentration of the substance concerned.
Organic peroxides and self-reactive substances specifically listed in portable tank instruction T23
in 4.2.5.2.6 may be carried in portable tanks.
Additional provisions applicable to the carriage of Class 6.1 substances in portable tanks
(Reserved)
Additional provisions applicable to the carriage of Class 6.2 substances in portable tanks
(Reserved)
Additional provisions applicable to the carriage of Class 7 substances in portable tanks
Portable tanks used for the carriage of radioactive material shall not be used for the carriage of other goods.
The degree of filling for portable tanks shall not exceed 90% or, alternatively, any other value
approved by the competent authority.