Bonding and
Grounding
Flammable Liquid Transfer
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Static electricity, or a difference in electrical potential
between two objects, is most easily understood by
the act of dragging one’s feet while walking on a
carpeted floor. If the air is dry enough, a difference in
electrical potential or “charge” can occur. When an
object with a different charge is touched, the static
electricity rapidly equalizes between the two objects,
creating a spark.
This rapid equalization of electrical potential becomes
potentially catastrophic when handling flammable
liquids. Filling one container of flammable liquid from
another container creates friction between the liquid
and the container and can produce a static charge.
Under certain conditions, a spark may ignite the
flammable vapors in the area. It is for this reason that
steps must be taken to equalize the difference
in electrical potential between the containers.
These steps are commonly referred to as bonding
and grounding.
There are two types of bonding and grounding
connections: permanent and temporary. Permanent
connections can be made using solid or braided wires
and should incorporate screw-type clamps, welding or
similar means of attachment. Temporary connections
should use only braided wires in conjunction with
spring clamps, magnetic clamps or similar methods of
maintaining metal-to-metal contact.
Bonding and Grounding
Flammable Liquids
The process of bonding and grounding can best be
described as creating an electrical pathway between
a dispensing container, a receiving container and an
earth ground. This pathway allows static electricity to
safely dissipate into the ground.
OSHA regulations and the Uniform Fire Code state
that all Class 1 liquids (flash points below 73°F) shall
not be dispensed into containers unless the nozzle
and containers are electrically interconnected. Some
common examples of Class 1 liquids include: alcohol,
toluene, acetone and benzene. The flash point of
chemicals and flammable liquids can be found on the
Material Safety Data Sheet (MSDS) that accompanies
the product.
Bonding is connecting two or more conductive
objects with a conductor, such as a copper wire,
which equalizes the difference in potential, or charge,
between them.
Grounding is connecting one or more conductive
objects directly to the earth by means of a conductive
rod driven into the ground or connection to a cold
water pipe. All connections must be made to clean,
bare metal. No paint, rust or other material can be
allowed to interfere with the bonding or grounding
connections, as this may add resistance to the
equalization of the charge.
Continued
Figure 1. Typical grounding system for small volume solvent dispensing via drum tap.
Building static grounding “bus”
1/8 in. stainless steel
grounding cable
Bonding and Grounding
Flammable Liquid Transfer
1/4 in. stainless steel
grounding cable
The following NFPA® illustrations show the two most
common types of flammable liquid transfers. Figure
1 illustrates bonding and grounding using the gravity
feed method. The bulk drum should be connected
to a grounding system (e.g., a cold water pipe or a
conductive rod driven into the ground), and the vessel
being filled should be connected, or bonded to the
bulk drum.
Figure 2 illustrates the bonding and grounding steps
Connector
necessary
when using a drum pump. Note that the
pump is electrically connected to the bulk drum,
2 in. x 3 in. x 3/16 in.
grounding being
tab
the container
filled and the fixed grounding
system. When using reliable bonding and grounding
techniques, static electricity should not build up
Open Pail
during flammable liquid transfer operations.
Figure 2 illustrates the bonding and grounding steps necessary when using a drum pump. Note that the
electrically
bulk drum,
the container
being filled,system
and the fixed
grounding system. When using
Figure 1. Typical grounding system for
small connected to theFigure
2. Typical
grounding
for small
bonding and grounding techniques, static electricity should not build up during flammable liquid transfer operat
volume solvent
dispensing
viasolvent
drumdispensing
tap
solvent dispensing via drum pump.
ure 1. Typical grounding
system for
small volume
via drum
tap.volume
Figure 2. Typical
grounding
system for small volume solvent dispensing via drum pump.
Building static grounding “bus”
Lugs mounted on flange bolt of
pump with 1/8 in. stainless steel
grounding cable and ground clamp
1/8 in. stainless steel
grounding cable
Open pail with grounding
cable and clamp
1/4 in. stainless steel
grounding cable
For attachment to tab
on building ground bus
Connector
2 in. x 3 in. x 3/16 in.
grounding tab
For Additional Information
Figures 1 and 2 are reprinted with permission from NFPA 77-2007, Recommended
National Fire
Protection Association:
NFPA
77® Recommended
PracticeFire
onProtection
Static Electricity,
Practice on Static
Electricity,
Copyright © 2006, National
Association, 2000 Edition
Open Pail
Quincy, MA. This reprinted material is not the complete and official position of the
Occupational Safety and Health Administration: 29 CFR 1910.106
NFPA on the referenced subject, which is represented only by the standard in
www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9752
entirety.
re 2 illustrates the bonding and grounding steps necessary when
using a drum pump.itsNote
that the pump is
trically connected to the bulk drum, the container being filled, and
the fixed
grounding
system.with
When
using reliable
Figures
1 and
2 are reprinted
permission
from NFPA 77-2000, Static Electricity Copyright © 2000, Natio
ding and grounding techniques, static electricity should not buildProtection
up during flammable
liquid
transfer
Association,
Quincy,
MAoperations.
02169. This reprinted material is not the complete and official positio
NFPA on thevia
referenced
subject, which is represented only by the standard in its entirety.
ure 2. Typical grounding system for small volume solvent dispensing
drum pump.
For Additional Information
Lugs mounted on flange bolt of National Fire Protection
pump with 1/8 in. stainless steel
grounding cable and ground clampwww.nfpa.org
Open pail with grounding
cable and clamp
Association:
• NFPA 77® Recommended Practice on
Static Electricity
For attachment to tab
on building ground bus
Occupational Safety & Health Administration:
www.osha.gov
• Standard 29 CFR 1910
Additional Information
onal Fire Protection Association: NFPA 77® Recommended Practice on Static Electricity, 2000 Edition
upational Safety and Health Administration: 29 CFR 1910.106
w.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9752
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Home Office: 717 Mulberry St.
Des Moines, IA 50309
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res 1 and 2 are reprinted with permission from NFPA 77-2000, Static Electricity Copyright © 2000, National Fire
ection Association, Quincy, MA 02169. This reprinted material is not the complete and official position of the
A on the referenced
subject,
whichisisdesigned
represented
only by
standard
in itspurposes
entirety.
Disclaimer:
This material
and intended
for the
general
information
only, and is not intended, nor shall be construed or relied upon, as specific legal advice.
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