Dangerous Goods by Road
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 having a capacity of more than 450 litres used for the carriage
of non-refrigerated liquefied gases of class 2. the portable tank includes a shell fitted with service
equipment and structural equipment necessary for the carriage of gases. 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. tankvehicles,
tank-wagons, non-metallic tanks, intermediate bulk containers (ibcs), gas cylinders and
large receptacles are not considered to fall within the definition for portable tanks;
shell means the part of the portable tank which retains the non-refrigerated liquefied gas 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 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, but in
no case less than 7 bar:
(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:
(i) for a non-refrigerated liquefied gas listed in the portable tank instruction t50
in 4.2.5.2.6, the mawp (in bar) given in t50 portable tank instruction for that gas;
(ii) for other non-refrigerated liquefied gases, not less than the sum of:
- the absolute vapour pressure (in bar) of the non-refrigerated liquefied gas at the
design reference temperature minus 1 bar; and
- the partial pressure (in bar) of air or other gases in the ullage space
being determined by the design reference temperature and the liquid phase
expansion due to an increase of the mean bulk temperature of tr -tf (tf = filling
temperature, usually 15 °c, tr = maximum mean bulk temperature, 50 °c);
(iii) for chemicals under pressure, the mawp (in bar) given in t50 portable tank instruction
for the liquefied gas portion of the propellants listed in t50 in 4.2.5.2.6;
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 maximum effective gauge pressure to which the shell is designed as defined in (b) of
the mawp definition (see above); and
(ii) a head pressure determined on the basis of the static forces specified in 6.7.3.2.9, but not
less than 0.35 bar;
test pressure means the maximum gauge pressure at the top of the shell during the pressure test;
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 6.7.3.3.3.3;
design temperature range for the shell shall be -40 °c to 50 °c for non-refrigerated liquefied gases
carried under ambient conditions. more severe design temperatures shall be considered for portable
tanks subjected to severe climatic conditions;
design reference temperature means the temperature at which the vapour pressure of the contents is
determined for the purpose of calculating the mawp. the design reference temperature shall be less
than the critical temperature of the non-refrigerated liquefied gas or liquefied gas propellants of
chemicals under pressure intended to be carried to ensure that the gas at all times is liquefied. this
value for each portable tank type is as follows:
(a) shell with a diameter of 1.5 metres or less: 65 °c;
(b) shell with a diameter of more than 1.5 metres:
(i) without insulation or sun shield: 60 °c;
(ii) with sun shield (see 6.7.3.2.12): 55 °c; and
(iii) with insulation (see 6.7.3.2.12) : 50 °c;
filling density means the average mass of non-refrigerated liquefied gas per litre of shell capacity
(kg/l). the filling density is given in portable tank instruction t50 in 4.2.5.2.6.