Grounding Bonding For Flammables
What resistance is acceptable for a bonding/grounding connection in flammable service?
Regulations like WorkSafeBC and OSHA state qualitative requirements (effective, continuous bonding/grounding) but do not prescribe a single numeric resistance. Industry and NFPA guidance often adopt bonding/grounding paths with resistance < 10 Ω or < 25 Ω to earth as a practical design/testing target for static control systems. Best practice includes documented testing of key grounding points using an ohmmeter or ground tester per facility standard, and flagging any connection with visibly damaged cables or unclear earth path.
How do you verify a 'known and verified ground point'?
Verification includes design-level checks (ground bus connected to building grounding electrode system per electrical code, welded or bolted connections to structural steel) and maintenance-level checks (periodic resistance testing from ground point to building ground using a ground resistance tester, visual inspection for tight, corrosion-free connections). Procedurally, SOPs should require connecting bonding and grounding cables to a specific Ground Point ID with documented last test date and satisfactory result, and lockout in digital permits if the ground point is unverified or overdue inspection.
When is bonding/grounding not required for small containers on a shop floor?
Grounding and bonding are required for containers that conduct electricity (metal or conductive plastics). If the container is made from non-conductive material (polyethylene, glass) and dispensing is from ≤ 1 gallon (4 L) container, grounding and bonding are generally not required from a static control perspective. However, this exemption is based on low static energy potential in small-volume, low-flow dispensing. High-hazard conditions (e.g., atomizing nozzles, aerosol formation, pneumatic transfer, low humidity) may still warrant static control measures as determined by site hazard assessment. WorkSafeBC does not specify the 1-gallon exemption; it relies on whether containers are metallic or conductive and whether transfer of flammable/combustible liquids/gases is occurring.
Grounding and bonding for flammables are engineered electrostatic controls that connect conductive flammable-handling equipment (drums, tanks, piping, cans) to each other and to earth so static charge cannot accumulate and produce an ignition source during transfer, dispensing, mixing, or loading of flammable/combustible liquids and gases. Bonding equalizes potential between objects, while grounding dissipates charge to earth, removing the spark from the fire triangle.
On the shop floor, grounding and bonding are applied during drum-to-container dispensing, tank-to-tank transfers, and loading/unloading of mobile tanks. For example, a 205 L drum is grounded via a cable to a verified plant ground, and a bonding cable connects the drum to a receiving metal can, with bare metal contact at both ends. All conductive components (piping, pumps, funnels) are included in the bonded network. WorkSafeBC requires metallic or conductive containers to be bonded or grounded during transfer. For non-conductive containers (e.g., plastic) under 1 gallon, grounding may not be required, but metallic fittings must still be bonded. Integration into compliance systems includes verification steps for cable attachment and clean contact surfaces.
Cables present but ineffective connections: Clamps attached to painted, rusty, or dirty surfaces, or use of corroded cables, preventing a conductive path.
Bonding without grounding: Operators bond containers together but fail to ground the system to earth, allowing high potential relative to earth and risk of spark to a third object.
Ignoring material and scenario thresholds: Misapplying rules by not grounding small containers or high-volatility liquids, or assuming intermittent transfers do not require bonding/grounding.