Bonding and grounding are methods of controlling static electricity so it cannot discharge as a spark and ignite flammable vapors or combustible dust. Bonding connects two or more conductive objects, such as a drum and a safety can, so they share the same electrical potential. Grounding connects an object to the earth so built-up charge drains away safely.
Both are essential when transferring flammable liquids, because the flow of liquid through pipes, hoses and nozzles generates static charge.
Why Static Electricity Is Dangerous
When liquids flow, splash or are filtered, charge separates and builds up on the liquid and its container. If two objects reach different potentials, a spark can jump between them. Many flammable liquids give off enough vapor to ignite from a very small spark, so a static discharge near an open container can start a flash fire. The same risk exists with combustible dust handling.
Bonding vs. Grounding
- Bonding eliminates a difference in potential between objects, so no spark jumps between them. It does not remove the charge from the system.
- Grounding connects the system to earth, draining charge away so it cannot build up.
In practice, both are used together: containers are bonded to each other, and the dispensing container is grounded.
OSHA Requirements
OSHA's flammable liquids standard, 29 CFR 1910.106, requires that when flammable liquids with a flashpoint below 100°F (37.8°C) are dispensed into containers, the nozzle and container be electrically interconnected, and that dispensing systems be bonded and grounded. Employers must also control ignition sources where flammable vapors may be present. NFPA 77, Recommended Practice on Static Electricity, provides detailed guidance for designing static controls.
How to Bond and Ground Containers Step by Step
- Check the safety data sheet. Confirm the liquid's flashpoint and any static-related precautions.
- Use conductive containers. Metal safety cans and drums are preferred. Plastic containers do not conduct charge in the same way and need extra care.
- Ground the source drum. Clamp a grounding cable from the drum to a verified ground, such as a ground bus.
- Bond the receiving container. Clamp a bonding wire between the drum and the receiving container before opening it.
- Get metal-to-metal contact. Clamps must bite through paint, rust or coatings.
- Dispense slowly. Keep the nozzle in contact with the container and avoid splash filling.
- Remove connections last. Close containers before removing bonding and grounding wires.
- Inspect and test. Check cables and clamps regularly and verify continuity.
Common Mistakes to Avoid
- Clamping onto painted or rusty surfaces.
- Using damaged or frayed cables.
- Filling portable containers in a truck bed instead of on the ground.
- Assuming plastic containers cannot build static.
- Forgetting that people can carry static charge too.
How SMS360 Helps
SMS360's Safety Data Sheets module centralizes SDS documents so workers and supervisors can quickly check a product's flashpoint, fire hazards and handling precautions before transferring it. Keeping SDSs current and easy to find supports safe handling of flammable liquids across sites.
Frequently Asked Questions
What is the difference between bonding and grounding?
Bonding connects conductive objects to each other so they are at the same electrical potential and no spark can jump between them. Grounding connects an object to the earth so static charge drains away. Both are usually used together when transferring flammable liquids.
When is bonding and grounding required?
OSHA requires electrical interconnection between the nozzle and container when dispensing flammable liquids with a flashpoint below 100°F into containers. Bonding and grounding are also recommended for other static-generating operations, such as handling combustible dust or filling tanks.
Why should gas cans be filled on the ground?
Placing a portable container on the ground before filling helps dissipate static charge. Filling a container in a truck bed with a plastic liner can isolate it, allowing static to build up and potentially cause a spark at the nozzle.
