Question: How do you recommend bonding and grounding drums of flammable wastes in a central accumulation area? I currently have them stored on plastic containment pallets. Do I just ground the drums or should I also ground the pallets?
Answer: The danger involved in this situation is that static electricity can build on drums and create a spark that could ignite flammable vapors and even cause an explosion. There is no way to eliminate static electricity, but bonding and grounding of drums prevent sparks in the following ways:
- Grounding drums of flammable wastes provides a path for static electricity to be safely dissipated into the earth
- Bonding containers prevents sparks between them by equalizing their potential energy
Both the Occupation Safety and Health Administration (OSHA) and the National Fire Protection Association (NFPA) require drums and other containers to be bonded and grounded during fluid transfer. However, neither has formal requirements for containers in storage. Most facilities do ground drums in storage as best practice, and many insurance carriers require the practice.
When you do bond or ground containers, be sure that each end of the bonding or grounding wire makes metal-to-metal contact. Paint, rust, dirt and other non-conductive surfaces can negate bonding and grounding. Grounding wires can be connected to unpainted water pipes that are grounded or to grounding rods that are sunk several feet into the earth. Both methods will safely channel static electricity.
This question also concerns drums stored on plastic pallets. As a non-conductive material, plastic is not suitable for bonding or grounding because static electricity cannot flow through it into bonding or grounding wires. Steel containment pallets are conductive and will complete the channel.
Ensuring proper ventilation will also help minimize hazards in waste storage areas. This helps prevent flammable vapors from building up and creating the potential for explosions.