7.5.5 Tanks Constructed of Nonconductive Materials.
Tanks
constructed of nonconductive materials are not allowed for
storing Classes I, II, and IIIA liquids except under special cir-
cumstances, as outlined in Section 2.2 of NFPA 30, Flammable
and Combustible Liquids Code. (See 7.10.7 for design and use recom-
mendations.)
7.6 Loading of Tank Vehicles.
Recommended loading pre-
cautions for tank vehicles vary with the characteristics of the
liquid being handled and the design of the loading facility. A
summary of precautions recommended when a flammable
mixture exists in the tank vehicle compartment, based on API
RP 2003, Protection Against Ignitions Arising Out of Static, Light-
ning, and Stray Currents, is provided in Table 7.6. These precau-
tions are intended for tank vehicles with conductive (metal)
compartments. (For compartments with nonconductive linings, see
7.10.4. For compartments of nonconductive material, see 7.10.7.)
7.6.1 Top Filling.
Splash filling should be avoided by using a fill
pipe that is designed according to the recommendations in 7.4.4.
7.6.2 Bottom Filling.
The bottom-filling inlet should be
designed with a deflector or a diverter to prevent upward
spraying and generation of mist. Using a cap or a tee to direct
incoming liquid sideways toward the compartment walls,
rather than upward, will achieve this objective.
7.6.3 Switch Loading.
The practice of loading a high flash
point, low conductivity liquid into a tank that previously con-
tained a low flash point liquid is known as switch loading. This
practice can result in the ignition of residual flammable vapor
as the tank is filled. The methods of hazard prevention are
similar to those for 7.5.2.1(a), (b), (d), (e), (f), and (g). Flow
velocities are found in Table 7.6.
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