Additives

Additives necessary for the treatment of the resin, such as catalysts, accelerators, hardeners and
thixotropic substances as well as materials used to improve the tank, such as fillers, colours, pigments
etc. shall not cause weakening of the material, taking into account lifetime and temperature
expectancy of the design.

Shells, their attachments and their service and structural equipment shall be designed to withstand
without loss of contents (other than quantities of gas escaping through any degassing vents) during the
design lifetime:
- the static and dynamic loads in normal conditions of carriage;
- the prescribed minimum loads as defined in 6.9.2.5 to 6.9.2.10.

At the pressures as indicated in 6.8.2.1.14 (a) and (b), and under the static gravity forces caused by the
contents with maximum density specified for the design and at maximum filling degree, the design
stress σ in longitudinal and circumferential direction of any layer of the shell shall not exceed the
following value:
 

At the dynamic stresses, as indicated in 6.8.2.1.2 the design stress shall not exceed the value specified
in 6.9.2.5, divided by the factor α.

At any of the stresses as defined in 6.9.2.5 and 6.9.2.6, the resulting elongation in any direction shall
not exceed 0.2% or one tenth of the elongation at fracture of the resin, whichever is lower.

At the specified test pressure, which shall not be less than the relevant calculation pressure as
specified in 6.8.2.1.14 (a) and (b) the maximum strain in the shell shall not be greater than the
elongation at fracture of the resin.

The shell shall be capable of withstanding the ball drop test according to 6.9.4.3.3 without any visible
internal or external defects.

The overlay laminates used in the joints, including the end joints, the joints of the surge plates and the
partitions with the shell shall be capable of withstanding the static and dynamic stresses mentioned
above. In order to avoid concentrations of stresses in the overlay lamination, the applied tapper shall
not be steeper than 1:6.
The shear strength between the overlay laminate and the tank components to which it is bonded shall
not be less than:
 

Openings in the shell shall be reinforced to provide at least the same safety factors against the static
and dynamic stresses as specified in 6.9.2.5 and 6.9.2.6 as that for the shell itself. The number of
openings shall be minimized. The axis ratio of oval-shaped openings shall be not more than 2.

For the design of flanges and pipework attached to the shell, handling forces and the fastening of bolts
shall also be taken into account.

The tank shall be designed to withstand, without significant leakage, the effects of a full engulfment in
fire for 30 minutes as specified by the test requirements in 6.9.4.3.4. Testing may be waived with the
agreement of the competent authority, where sufficient proof can be provided by tests with
comparable tank designs.

Special requirements for the carriage of substances with a flash-point of not more than 60 °C

FRP tanks used for the carriage of substances with a flash-point of not more than 60°C shall be
constructed so as to ensure the elimination of static electricity from the various component parts so as
to avoid the accumulation of dangerous charges.

The electrical surface resistance of the inside and outside of the shell as established by measurements
shall not be higher than 109 ohms. This may be achieved by the use of additives in the resin or
interlaminate conducting sheets, such as metal or carbon network.

The discharge resistance to earth as established by measurements shall not be higher than 10^7 ohms.

All components of the shell shall be electrically connected to each other and to the metal parts of the
service and structural equipment of the tank and to the vehicle. The electrical resistance between
components and equipment in contact with each other shall not exceed 10 ohms.
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