Dangerous Goods by Road
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The thickness of shells designed in accordance with 6.8.2.1.14 (a) which either are of not more than 5 000 litres capacity or are divided into leakproof compartments of not more than 5 000 litres unit capacity may be adjusted to a level which, unless prescribed otherwise in 6.8.3 or 6.8.4, shall however not be less than the appropriate value shown in the following table: |
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Maximum radius of curvature of shell (m) |
Capacity of shell or shell compartment (m3) |
Minimum thickness (mm) |
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Mild steel |
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2 |
5.0 |
3 |
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2 - 3 |
3.5 |
3 |
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> 3.5 but 5.0 |
4 |
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Where a metal other than mild steel3 is used, the thickness shall be determined by the equivalence formula given in 6.8.2.1.18 and shall not be less than the values given in the following table: |
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Maximum radius of curvature of shell (m) |
2 |
2-3 |
2-3 |
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Capacity of shell or shell compartment (m3) |
5.0 |
3.5 |
> 3.5 but 5.0 |
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Minimum thickness of shell |
Austenitic stainless steels |
2.5 mm |
2.5 mm |
3 mm |
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Austenitic- ferritic stainless steels |
3 mm |
3 mm |
3.5 mm |
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Other steels |
3 mm |
3 mm |
4 mm |
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Aluminium alloys |
4 mm |
4 mm |
5 mm |
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Pure aluminium at 99.80% |
6 mm |
6 mm |
8 mm |
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The thickness of the partitions and surge-plates
shall in no case be less than that of the shell.
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Surge-plates and partitions shall be dished, with
a depth of dish of not less than 10 cm, or shall be
corrugated, profiled or otherwise reinforced to
give equivalent strength. The area of the surge
plate shall be at least 70% of the cross-sectional
area of the tank in which the surge-plate is fitted.
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Welding and inspection of welds
The ability of the manufacturer to perform welding operations shall be verified and confirmed by
either the competent authority or by the body designated by this authority, which issues the type
approval. A weld quality assurance system shall be operated by the manufacturer. Welding shall be
performed by qualified welders using a qualified welding process whose effectiveness (including
any heat treatments required) has been demonstrated by tests. Non-destructive tests shall be carried
out by radiography or by ultrasound and shall confirm that the quality of the welding is appropriate
to the stresses.
The following checks shall be carried out for welds made by each welding process used by the
manufacturer in accordance with the value of the coefficient λ used in determining the thickness of
the shell in 6.8.2.1.17:
λ = 0.8: All weld beads shall so far as possible be inspected visually on both faces and shall
be subjected to non-destructive checks. The non-destructive checks shall include all
weld “Tee” junctions and all inserts used to avoid welds crossing. The total length
of welds to be examined shall not be less than:
10% of the length of all the longitudinal welds,
10% of the length of all the circumferential welds,
10% of the length of all the circumferential welds in the tank ends, and
10% of the length of all the radial welds in the tank ends.
λ = 0.9: All weld beads shall so far as possible be inspected visually on both faces and shall
be subjected to non-destructive checks. The non-destructive checks shall include all
connections, inserts used to avoid welds crossing, and welds for the assembly of
large-diameter items of equipment. The total length of welds to be examined shall
not be less than:
100% of the length of all the longitudinal welds,
25% of the length of all the circumferential welds,
25% of the length of all the circumferential welds in the tank ends, and
25% of the length of all the radial welds in the tank ends.
λ = 1: All weld beads throughout their length shall be subjected to non-destructive checks
and shall so far as possible be inspected visually on both faces. A weld test-piece
shall be taken.
In the cases of either λ = 0.8 or λ = 0.9, when the presence of an unacceptable defect is detected in a
portion of a weld, the non-destructive checks shall be extended to a portion of equal length on both
sides of the portion that contains the defect. If the non-destructive checks detect an additional defect
that is unacceptable, non-destructive checks shall be extended to all remaining welds of the same
type of welding process.
Where either the competent authority or a body designated by this authority has doubts regarding
the quality of welds, including the welds made to repair any defects revealed by the non-destructive
checks, it may require additional checks.
3 For the definitions of "mild steel" and "reference steel" see 1.2.1. "Mild steel" in this case also covers a steel
referred to in EN material standards as "mild steel", with a minimum tensile strength between 360 N/mm² and
490 N/mm² and a minimum elongation at fracture conforming to 6.8.2.1.12.
5 Equivalent measures means measures given in standards referenced in 6.8.2.6.
Other construction requirements
The protective lining shall be so designed that its leakproofness remains intact, whatever the
deformation liable to occur in normal conditions of carriage (see 6.8.2.1.2).
The thermal insulation shall be so designed as not to hinder access to, or the operation of, filling and
discharge devices and safety valves.
If shells intended for the carriage of flammable liquids having a flash-point of not more than 60 ºC
are fitted with non-metallic protective linings (inner layers), the shells and the protective linings shall
be so designed that no danger of ignition from electrostatic charges can occur.
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Shells intended for the carriage of liquids having
a flash-point of not more than 60 ºC or for the
carriage of flammable gases, or of UN No.1361
carbon or UN No.1361 carbon black, packing
group II, shall be linked to the chassis by means
of at least one good electrical connection. Any
metal contact capable of causing electrochemical
corrosion shall be avoided. Shells shall be
provided with at least one earth fitting
clearly marked with the symbol
 capable
of being electrically connected.
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All parts of a tank-container intended for the
carriage of liquids having a flash-point of not
more than 60 ºC, flammable gases, or UN
No.1361 carbon or UN No.1361 carbon black,
packing group II, shall be capable of being
electrically earthed. Any metal contact capable
of causing electrochemical corrosion shall be
avoided.
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Protection of fittings mounted on the upper part of the tank
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The fittings and accessories mounted on the
upper part of the tank shall be protected against
damage caused by overturning. This protection
may take the form of strengthening rings,
protective canopies or transverse or longitudinal
members so shaped that effective protection is
given.
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Items of equipment
Suitable non-metallic materials may be used to manufacture service and structural equipment.
The items of equipment shall be so arranged as to be protected against the risk of being wrenched
off or damaged during carriage or handling. They shall exhibit a suitable degree of safety
comparable to that of the shells themselves, and shall in particular:
- be compatible with the substances carried; and
- meet the requirements of 6.8.2.1.1.
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.
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As many operating parts as possible shall be
served by the smallest possible number of
openings in the shell. The leakproofness of the
service equipment including the closure (cover)
of the inspection openings shall be ensured even
in the event of overturning of the tank, taking
into account the forces generated by an impact
(such as acceleration and dynamic pressure).
Limited release of the tank contents due to a
pressure peak during the impact is however
allowed.
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The leakproofness of the service equipment shall
be ensured even in the event of the overturning of
the tank-container.
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The gaskets shall be made of a material compatible with the substance carried and shall be replaced
as soon as their effectiveness is impaired, for example as a result of ageing.
Gaskets ensuring the leakproofness of fittings requiring manipulation during normal use of tanks
shall be so designed and arranged that manipulation of the fittings incorporating them does not
damage them.
Each bottom-filling or bottom-discharge opening in tanks which are referred to, in Column (12) of
Table A of Chapter 3.2, with a tank code including the letter "A" in its third part (see 4.3.4.1.1) shall
be equipped with at least two mutually independent closures, mounted in series, comprising
- an external stop-valve with piping made of a malleable metal material and
- a closing device at the end of each pipe which may be a screw-threaded plug, a blank flange
or an equivalent device. This closing device shall be sufficiently tight so that the substance is
contained without loss. Measures shall be taken to enable the safe release of pressure in the
discharge pipe before the closing device is completely removed.
Each bottom-filling or bottom-discharge opening in tanks which are referred to, in Column (12) of
Table A of Chapter 3.2, with a tank code including the letter "B" in its third part (see 4.3.3.1.1 or
4.3.4.1.1) shall be equipped with at least three mutually independent closures, mounted in series,
comprising
- an internal stop-valve, i.e. a stop-valve mounted inside the shell or in a welded flange or
companion flange;
- an external stop-valve or an equivalent device 6
| one at the end of each pipe | as near as possible to the shell |
and
- a closing device at the end of each pipe which may be a screw-threaded plug, a blank flange or
an equivalent device. This closing device shall be sufficiently tight so that the substance is
contained without loss. Measures shall be taken to enable the safe release of pressure in the
discharge pipe before the closing device is completely removed.
However, in the case of tanks intended for the carriage of certain crystallizable or highly viscous
substances and shells fitted with an ebonite or thermoplastic coating, the internal stop-valve may be
replaced by an external stop-valve provided with additional protection.
The internal stop-valve shall be operable either from above or from below. Its setting - open or closed
- shall so far as possible in each case be capable of being verified from the ground. Internal stopvalve
control devices shall be so designed as to prevent any unintended opening through impact or an
inadvertent act.
The internal shut-off device shall continue to be effective in the event of damage to the external
control device.
In order to avoid any loss of contents in the event of damage to the external fittings (pipes, lateral
shut-off devices), the internal stop-valve and its seating shall be protected against the danger of being
wrenched off by external stresses or shall be so designed as to resist them. The filling and discharge
devices (including flanges or threaded plugs) and protective caps (if any) shall be capable of being
secured against any unintended opening.
The position and/or direction of closure of shut-off devices shall be clearly apparent.
All openings of tanks which are referred to in Column (12) of Table A of Chapter 3.2, by a tank code
including letter "C" or "D" in its third part (see 4.3.3.1.1 and 4.3.4.1.1) shall be situated above the
surface level of the liquid. These tanks shall have no pipes or pipe connections below the surface
level of the liquid. The cleaning openings (fist-holes) are, however, permitted in the lower part of the
shell for tanks referred to by a tank code including letter "C" in its third part. This opening shall be
capable of being sealed by a flange so closed as to be leakproof and whose design shall be approved
by the competent authority or by a body designated by that authority.
6 In the case of tank-containers of less than 1 m3 capacity, the external stop-valve or other equivalent device may
be replaced by a blank flange.
Tanks that are not hermetically closed may be fitted with vacuum valves to avoid an unacceptable
negative internal pressure; these vacuum-relief valves shall be set to relieve at a vacuum setting not
greater than the vacuum pressure for which the tank has been designed (see 6.8.2.1.7). Hermetically
closed tanks shall not be fitted with vacuum valves. However, tanks of the tank code SGAH, S4AH or
L4BH, fitted with vacuum valves which open at a negative pressure of not less than 21 kPa (0.21 bar)
shall be considered as being hermetically closed. For tanks intended for the carriage of solid
substances (powdery or granular) of packing groups II or III only, which do not liquefy during
transport, the negative pressure may be reduced to not less than 5 kPa (0.05 bar).
Vacuum valves and breather devices (see 6.8.2.2.6) used on tanks intended for the carriage of
substances meeting the flash-point criteria of Class 3, shall prevent the immediate passage of flame
into the shell by means of a suitable protective device, or the shell of the tank shall be explosion
pressure shock resistant, which means being capable of withstanding without leakage, but allowing
deformation, an explosion resulting from the passage of the flame.
If the protective device consists of a suitable flame trap or flame arrester, it shall be positioned as
close as possible to the shell or the shell compartment. For multi-compartment tanks, each
compartment shall be protected separately.
The shell or each of its compartments shall be provided with an opening large enough to permit
inspection.
(Reserved)
Tanks intended for the carriage of liquids having a vapour pressure of not more than 110 kPa (1.1 bar)
(absolute) at 50 oC shall have a breather device and a safety device to prevent the contents from
spilling out if the tank overturns; otherwise they shall conform to 6.8.2.2.7 or 6.8.2.2.8.