Grounding & Bonding 101
Facilities often use grounding and bonding principals to control static electricity and prevent fire and/or explosion. The dissipation of accumulated electrical charge from an object or material is a common source of static electricity.
The static potential in an object or substance (or the system that contains it) is directly related to its electrical conductivity and the conductivity in the materials surrounding it. If a substance or system has low electrical conductivity, it may generate and build up electrical charge faster than it can release that charge.
When enough electrical charge builds up in an object or material and another object or substance with a different static potential, or higher conductivity, comes close enough; the excess charge can arc from the one to the other. In industrial settings, we often see this in material transfer. When a material flows through pipes, hoses or the air, it can generate static electricity.
Grounding that Static
Dry air, pipe or hose material and its inner surface structure all account for how much and where in a system static will show up. Static electricity, in and of itself, is not necessarily dangerous. However if this electricity does not have a suitable grounding path, it will dissipate or spark. This can create an ignition source and, if you are working with flammable materials, that may cause more excitement than you want on any given day.
Grounding attaches an object to the ground and assures that generated electricity travels a safe path into the earth instead of creating a spark. Many objects in your facility are already good ground connectors, machine mounts, building frames, etc. If you are not sure, ask.
Bonding: The Great Equalizer
Bonding is the connection of two or more objects to ensure that they have the same static potential. With bonding, the static or electrical discharge does not need to arc to move from one object to the other. It can travel through the bonding system. In most cases, one of the bonded objects is grounded. This practice keeps the static potential even among all objects in the system and gives electrical buildup a safe path to the earth
You can test the theory for yourself at home. Vigorously rub your feet on the carpet to build up your static potential. Then, slowly extend a finger toward the back of your wife's ear. If her static potential is less than yours, the electrical charge, and an ignition source or spark, will jumped from your finger to her ear. Chances are very good that you will produce an explosive reaction.
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Unfortunately, using grounding and bonding is a safety rule that people often decide to ignore. On one occassion, forgetting to attache the bonding wires may produce no arc whatsoever. But don't get complacement, because the next time may be fatal.