Where protection of the tank against damage
through lateral impact or overturning is provided
according to 6.8.2.1.20, the competent authority
may allow the aforesaid minimum thicknesses to
be reduced in proportion to the protection
provided; however, the said thicknesses shall not
be less than 3 mm in the case of mild steel3, or
than an equivalent thickness in the case of other
materials, for shells not more than 1.80 m in
diameter. For shells with a diameter exceeding
1.80 m the aforesaid minimum thickness shall be
increased to 4 mm in the case of mild steel3 and
to an equivalent thickness in the case of other
metals.
Equivalent thickness means the thickness given
by the formula in 6.8.2.1.18.
Except in cases for which 6.8.2.1.21 provide, the
thickness of shells with protection against
damage in accordance with 6.8.2.1.20 (a) or (b)
shall not be less than the values given in the
table below.
Where protection of the tank against damage is
provided according to 6.8.2.1.20, the competent
authority may allow the aforesaid minimum
thicknesses to be reduced in proportion to the
protection provided; however, the said
thicknesses shall be not less than 3 mm in the
case of mild steel3, or than an equivalent
thickness in the case of other materials, for shells
not more than 1.80 m in diameter. For shells of a
diameter exceeding 1.80 m this minimum
thickness shall be increased to 4 mm in the case
of mild steel3, and to an equivalent thickness in
the case of other metals.
Equivalent thickness means the thickness given
by the formula in 6.8.2.1.18.
The thickness of shells with protection against
damage in accordance with 6.8.2.1.20 shall not
be less than the values given in the table below.
 

Diameter of shell

≤ 1,80 m

> 1,80 m

Minimum
thickness of
shells
Austenitic stainless steels 2,5 mm

3 mm

Austenitic-ferritic stainless
steels
3 mm

3,5 mm

Other steels

3 mm

4 mm

Aluminium alloys

4 mm

5 mm

Pure aluminium of 99.80%

6 mm

8 mm

 

For tanks built after 1 January 1990, there is
protection against damage as referred to in
6.8.2.1.19 when the following measures or
equivalent5 measures are adopted:
(a) For tanks intended for the carriage of
powdery or granular substances, the
protection against damage shall satisfy the
competent authority.
(b) For tanks intended for the carriage of other
substances, there is protection against
damage when:
 
1. For shells with a circular or elliptical
cross-section having a maximum radius
of curvature of 2 m, the shell is
equipped with strengthening members
comprising partitions, surge-plates or
external or internal rings, so placed that
at least one of the following conditions
is met:
- Distance between two adjacent
strengthening elements of not more
than 1.75 m.
- Volume contained between two
partitions or surge-plates of not
more than 7 500 l.
The vertical cross-section of a ring,
with the associated coupling, shall have
a section modulus of at least 10 cm3.
External rings shall not have projecting
edges with a radius of less than
2.5 mm.
Partitions and surge-plates shall
conform to the requirements of
6.8.2.1.22.
The thickness of the partitions and
surge-plates shall in no case be less
than that of the shell.
2. For tanks made with double walls, the
space between being evacuated of air,
the aggregate thickness of the outer
metal wall and the shell wall
corresponds to the wall thickness
prescribed in 6.8.2.1.18, and the
thickness of the wall of the shell itself
is not less than the minimum thickness
prescribed in 6.8.2.1.19.
3. For tanks made with double walls
having an intermediate layer of solid
materials at least 50 mm thick, the
outer wall has a thickness of at least
0.5 mm of mild steel3 or at least 2 mm
of a plastics material reinforced with
glass fibre. Solid foam (with an impact
absorption capacity like that, for
example, of polyurethane foam) may be
used as the intermediate layer of solid
material.
4. Shells of forms other than in 1,
especially box-shaped shells, are
provided, all round the mid-point of
their vertical height and over at least
30% of their height with a protection
designed in such a way as to offer
specific resilience at least equal to that
of a shell constructed in mild steel3 of a
thickness of 5 mm (for a shell diameter
not exceeding 1.80 m) or 6 mm (for a
shell diameter exceeding 1.80 m). The
protection shall be applied in a durable
manner to the shell.
This requirement shall be considered to
have been met without further proof of
the specific resilience when the
protection involves the welding of a
plate of the same material as the shell to
the area to be strengthened, so that the
minimum wall thickness is in
accordance with 6.8.2.1.18.
This protection is dependent upon the
possible stresses exerted on mild steel3
shells in the event of an accident, where
the ends and walls have a thickness of
at least 5 mm for a diameter not
exceeding 1.80 m or at least 6 mm for a
diameter exceeding 1.80 m. If another
metal is used, the equivalent thickness
shall be obtained in accordance with the
formula in 6.8.2.1.18.
For demountable tanks this protection is not
required when they are protected on all sides by
the drop sides of the carrying vehicle.
 
 
The protection referred to in 6.8.2.1.19 may
consist of:
- overall external structural protection as in
"sandwich" construction where the sheathing
is secured to the shell; or
- a structure in which the shell is supported by a
complete skeleton including longitudinal and
transverse structural members; or
- double-wall construction.
Where the tanks are made with double walls, the
space between being evacuated of air, the
aggregate thickness of the outer metal wall and
the shell wall shall correspond to the minimum
wall thickness prescribed in 6.8.2.1.18, the
thickness of the wall of the shell itself being not
less than the minimum thickness prescribed in
6.8.2.1.19.
Where tanks are made with double walls with an
intermediate layer of solid materials at least
50 mm thick, the outer wall shall have a
thickness of not less than 0.5 mm if it
is made of mild steel3 or at least 2 mm if it is
made of a plastics material reinforced with glass
fibre. Solid foam with an impact absorption
capacity such as that, for example, of
polyurethane foam, may be used as the
intermediate layer of solid material.

 

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:

 

Maximum radius of curvature

of shell (m)

Capacity of shell or shell compartment (m3)

Minimum thickness

(mm)

Mild steel

 2

 5.0

3

2 - 3

 3.5

3

 

> 3.5 but  5.0

4


Where a metal other than mild steelis 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:

 

 

 

Maximum radius of

curvature of shell (m)

 

 2

 

2-3

 

2-3

Capacity of shell or shell compartment

(m3)

 

 5.0

 

 3.5

> 3.5

but

 5.0

Minimum thickness of shell

Austenitic

stainless steels

 

2.5 mm

 

2.5 mm

 

3 mm

Austenitic- ferritic

stainless steels

3 mm

3 mm

3.5 mm

Other steels

3 mm

3 mm

4 mm

Aluminium

alloys

4 mm

4 mm

5 mm

Pure aluminium at

99.80%

 

6 mm

 

6 mm

 

8 mm

The thickness of the partitions and surge-plates
shall in no case be less than that of the shell.

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.
                                                                      

 

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.

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.
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.

 

Protection of fittings mounted on the upper part of the tank

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.
                                                                       

 

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.
 
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.
The leakproofness of the service equipment shall
be ensured even in the event of the overturning of
the tank-container.
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.
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