We've mentioned the terms Static Bonding and Grounding many times on this site, and of course since you are here, you've heard these terms thrown around as well.  Often people will use them interchangeably, Static Bonding or Static Grounding, as if they mean the same thing.  But there is a very important difference that is critical to understand if you want to be as safe as possible.  Complying with OSHA and NFPA requirements means knowing the difference and implementing it correctly.

A "bonding" system connects conductive equipment together to keep them at the same electrical potential. Static sparking will not take place between conductive objects that are the same potential.  Think about connecting a drum to a filling hose, or an airplane to the refueling truck, or a container to a mixing machine.  These are all good examples of 'bonding' together the pieces of equipment that are generating static electricity in an effort to bring them to the same electrical potential.  Assemblies such as the LE60HH (see right) are often used to accomplish something like this as the clamp on both ends can serve as a convenient portable way to bond two pieces of equipment together.

A "grounding" system is a special form of bonding in which conductive equipment is connected to earth in order to prevent sparking between conductive equipment and grounded structures.  Think about 'grounding' a drum to the copper bus bar in the room that leads eventually to the ground rod and earth.  We are bringing the electrical potential of the equipment to that of the earth, i.e. neutral.  Think of earth as having an unlimited amount of electrons and protons to give up or absorb, making it able to take any piece of equipment to a neutral electrical potential if connected properly.

So what to do?  It is often believed that bonding techniques alone are sufficient to eliminate the risk of static ignition.  As a result, many operators rely only on static bonding methods in the field.  In reality, bonding only ensures that two objects are at the same electrical potential and therefore electricity cannot jump between the two.  If those two items are themselves isolated from ground they can still hold electrical potential which could create a spark if a third material (e.g. a person) is introduced. 

Imagine this scenario.  An operator bonds together a drum full of flammable liquids and a mixing machine that is stirring up those liquids.  The movement of the liquids in the drum creates static electricity on the drum, and the bonding connection serves to equal that static charge out between the drum and the mixing machine.  Now, since the electrical potential between the two pieces of equipment is the same, you won't have a spark between them.  But now the operator leaves his/her post to do some other work and comes back to the mixing station after a couple of minutes.  It is likely the fact that the operator is now at a different electrical potential than the bonding drum/mixing machine.  When he/she then touches the mixer to turn it off, there is a strong chance of a static discharge between the mixer and the operator, which could ignite the fumes coming from the drum.  However, if the mixer was grounded (and thus the drum was grounded too as part of their bond), the risk of this discharge is much lower.

Bottom line:  It is always best to both bond and ground in order to ensure that the potential energy is zero.