Tanks shall be designed for a calculation pressure equal to 1.3 times the filling or discharge pressure
but not less than 400 kPa (4 bar) (gauge pressure). For the carriage of substances for which a higher
calculation pressure of the tank is specified in Chapter 6.8, this higher pressure shall apply.

Tanks shall be designed to withstand a negative internal pressure of 100 kPa (1 bar).

Items of 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. This requirement can be fulfilled by placing the items of
equipment in a so called "protected area" (see

The bottom discharge of shells may be constituted by external piping with a stop-valve fitted as close
to the shell as practicable and a second closure which may be a blank flange or other equivalent

The position and closing direction of the stop-valve(s) connected to the shell, or to any compartment
in the case of compartmented shells, shall be unambiguous, and be able to be checked from the

In order to avoid any loss of contents in the event of damage to the external filling and discharge
fittings (pipes, lateral shut-off devices), the internal stop-valve, or the first external stop-valve (where
applicable), and its seatings shall be protected against the danger of being wrenched off by external
stresses or shall be so designed as to withstand 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 tanks may be equipped with openable ends. Openable ends shall comply with the following
(a) The ends shall be designed to be secured leaktight when closed;
(b) Unintentional opening shall not be possible;
(c) Where the opening mechanism is power operated the end shall remain securely closed in the
event of a power failure;
(d) A safety or breakseal device shall be incorporated to ensure that the openable end cannot be
opened when there is still a residual over pressure in the tank. This requirement does not apply
to openable ends which are power-operated, where the movement is positively controlled. In
this case the controls shall be of the dead-man type and be so positioned that the operator can
observe the movement of the openable end at all times and is not endangered during opening
and closing of the openable end; and
(e) Provisions shall be made to protect the openable end and prevent it from being forced open
during a roll-over of the vehicle, tank-container or tank swap body.

Vacuum-operated waste tanks which are fitted with an internal piston to assist in the cleaning of the
tank or discharging shall be provided with stop-devices to prevent the piston in every operational
position being ejected from the tank when a force equivalent to the maximum working pressure of the
tank is applied to the piston. The maximum working pressure for tanks or compartments with
pneumatic operated piston shall not exceed 100 kPa (1.0 bar). The internal piston shall be constructed
in a manner and of materials which will not cause an ignition source when the piston is moved.
The internal piston may be used as a compartment provided it is secured in position. Where any of the
means by which the internal piston is secured is external to the tank, it shall be placed in a position not
liable to accidental damage.

The tanks may be equipped with suction booms if:
(a) The boom is fitted with an internal or external stop-valve fixed directly to the shell, or directly
to a bend that is welded to the shell; a rotation crown wheel can be fitted between the shell or
the bend and the external stop valve, if this rotation crown wheel is located in the protected
area and the stop-valve control device is protected with a housing or cover against the danger
of being wrenched off by external loads;
(b) The stop-valve mentioned in (a) is so arranged that carriage with the valve in an open position
is prevented; and
(c) The boom is constructed in such a way that the tank will not leak as a result of accidental
impact on the boom.

The tanks shall be fitted with the following additional service equipment:
(a) The outlet of a pump/exhauster unit shall be so arranged as to ensure that any flammable or
toxic vapours are diverted to a place where they will not cause a danger;
(b) A device to prevent immediate passage of flame shall be fitted to all openings of a vacuum
pump/exhauster unit which may provide a source of ignition and which is fitted on a tank used
for the carriage of flammable wastes, or 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;
(c) Pumps which can deliver a positive pressure shall have a safety device fitted in the pipework
which can be pressurised. The safety device shall be set to discharge at a pressure not
exceeding the maximum working pressure of the tank;
(d) A stop-valve shall be fitted between the shell, or the outlet of the overfill prevention device
fitted to the shell, and the pipework connecting the shell to the pump/exhauster unit;
(e) The tank shall be fitted with a suitable pressure/vacuum manometer which shall be mounted in
a position where it can be easily read by the person operating the pump/exhauster unit. A
distinguishing line shall be marked on the scale to indicate the maximum working pressure of
the tank;
(f) The tank, or in case of compartmented tanks, every compartment, shall be equipped with a
level indicating device. Sight glasses may be used as level indicating devices provided:
(i) they form a part of the tank wall and have a resistance to the pressure comparable to that
of the tank; or they are fitted external to the tank;
(ii) the top and bottom connections to the tank are equipped with shut-off valves fixed
directly to the shell and so arranged that carriage with the valves in an open position is
(iii) are suitable for operation at the maximum working pressure of the tank; and
(iv) are placed in a position where they will not be liable to accidental damage.

The shells of vacuum-operated waste tanks shall be fitted with a safety valve preceded by a bursting
The valve shall be capable of opening automatically at a pressure between 0.9 and 1.0 times the test
pressure of the tank to which it is fitted. The use of dead weight or counterweight valves is
The bursting disc shall burst at the earliest when the initial opening pressure of the valve is reached
and at the latest when this pressure reaches the test pressure of the tank to which it is fitted.
Safety devices shall be of such a type as to resist dynamic stresses, including liquid surge.
The space between the bursting disc and the safety valve shall be provided with a pressure gauge or
suitable tell-tale indicator for the detection of disc rupture, pinholing or leakage wich could cause a
malfunction of the safety valve.


Vacuum-operated waste tanks shall be subject every three years for fixed tanks or demountable tanks
and at least every two and a half years for tank-containers and tank swap bodies to an examination of
the internal condition, in addition to the tests according to


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