Bonding & Grounding Safety




What’s the difference between “bonding” and “grounding”?

Static electricity, or static charge, is created when two objects or materials come into contact with each other and then separate, or when liquids flow.  Under these circumstances, the surface the objects or the surface of the liquid builds up ionic (electric) charges.

If the charges are not equalized or if they do not have a path to ground, they can build up, eventually developing enough energy to jump as a spark.   An example is lightning which is a discharge of static electricity developed from one cloud across an air gap to another cloud or to the earth.

With respect to liquids, static electricity is produced when liquids flow through a pipe or hose; when they are agitated such as during tank or barge filling; or when they free fall such as when poured into tanks, cans or pails.  (Static is also produced when powdered material flows through chutes or conveyor systems.)

The main hazard of static electricity is the creation of sparks in a flammable atmosphere.  These sparks can cause an explosion or fire if they possess enough energy.  Two methods to control static electricity are bonding and grounding.

Bonding equalizes the charge on surfaces by providing an electrical path, e.g., a metal wire is used to connect metal (conductive) equipment and containers.  For example, bonding cables used during vacuum truck operations equalize the charge between the truck and the container collecting liquid.  Note that bonding does not eliminate the static charge, but it does equalize the charge which reduces the chance of a spark developing.

Grounding is connecting one or more conductive objects directly to the earth.  For example, the grounding cable on a vacuum truck when attached to a proper ground connection provides a path to ground which drains the static charge.  Grounding straps on fixed equipment serve the same purpose.  Unlike bonding which equalizes but does not eliminate the charge, grounding does eliminate the charge.