Static Electricity 2000 Edition

particular need should normally be selected and should not
exceed 20 L. Listed safety cans are recommended, especially
those types equipped with a flexible metal dispensing hose so
they can be used without a funnel. Because nonconductive con-
tainers cannot be grounded, they should be limited to 2 L for
Class IA liquids and 5 L for Class IB and Class IC liquids. An
exception is gasoline, where approved 20 L plastic cans have
been widely used for many years with no reported increase in
ignition incidents due to static electricity compared to metal
cans. This is in part due to the rapid establishment of rich
(above the UFL) gasoline vapor inside the can; these plastic con-
tainers should not be used for other flammable liquids without
review of the hazards. Unlike gasoline, conductive liquids such
as alcohols can become inductively charged by a charged plastic
container and give rise to sparks. In addition, the container can
contain an ignitible atmosphere.
7.13.6.1 Nonconductive Containers.
Subject to the volume
limitations described in 7.13.6, it is common to handle flam-
mable liquids in small glass or plastic containers of 0.5 L capac-
ity or less. Where such containers are involved in frequent
transfer operations, such as a small-scale solvent blending
operation, a grounded metal funnel whose spout extends to
the bottom of the container should be used when filling the
container. This practice ensures that any charge induced on
the liquid by the container, as could happen if the plastic con-
tainer has been charged by rubbing, is dissipated through the
grounded funnel. Plastic or glass funnels should be used only
where essential for compatibility reasons.
7.13.6.2 Containers for Sampling.
Ignition risk is greatly
increased when an ignitible atmosphere is present outside the
container; for example, when sampling directly from a tank or
transferring a sample near a manway, since this can precipitate
a large fire or explosion. A grounded metal sample “thief” or
glass bottle in a grounded metal sample cage can be used in
such cases. Nonconductive plastic containers should be
avoided, except when used in well-ventilated areas, since they
are more easily charged than glass. If outdoor sampling is car-
ried out at sample spigots that are located away from tank
openings and in freely ventilated areas, and sampled quanti-
ties are 1 L or less, the fire risk is, in most cases, insufficient to
require any special procedures other than bonding of metal
components.