Static Discharge Explosion Safety

Protect Against Static-Discharge Explosions with Proper Bonding

Static electricity results from the interaction of dissimilar materials. It can occur when these materials are rubbed together, such as walking across a carpet on a dry winter day while wearing woolen socks or rubbing a balloon on your hair.

However, static discharges are often created when material is conveyed from one point to another through a pipe or hose. The conveyed substance moves electrons from one material to another and the friction of these electrons creates static electricity.

An electrostatic discharge (also called a static spark) is a discharge of electricity across a gap between two points not in contact, resulting from a difference in electrical potential. This spark can be dangerous. In addition to causing in a painful shock, these sudden, high-voltage discharges can damage delicate electronics. More importantly, they can ignite flammable substances, according to the Occupational Safety and Health Administration (OSHA).

To control static discharges, many manufacturers use transfer hoses with an internal bonding wire to manage the discharge. Such hoses concentrate the static charge onto the internal wire. Unfortunately, this concentrated charge can become very strong and cause a discharge spark between the bonding wire and nearby equipment, or even between wraps of the bonding wire within the hose. This spark can then ignite materials with a low minimum ignition energy including starches, metal powders and some chemicals and plastics additives. This concentrated energy makes a hose with a disconnected internal bonding wire a likely ignition point in conveying systems.

One option for controlling static discharges is a static dissipative hose (no ground wire in hose) with a separate bonding wire with fittings made to create a bonding connection. Static dissipative hoses have compounds that spread and dissipate the static charge across the surface of the hose thus preventing a discharge large enough to cause an ignition.  

Proper hose connections for conveying system hose

This video shows poor connections throwing high energy sparks where there are unbonded hoses, flex connections and sight glasses.     

To protect against static charges, always:
  • Make sure you understand the conditions within your process that lead to static charge buildup.
  • Inspect your grounding wires for proper installation.
  • Use a static dissipative hose with an independent bonding wire to reduce the opportunity for static discharge.
  • Keep a clean production site to eliminate dust and other ignition sources.
Please contact us if you have questions or concerns regarding your process.