The 10-Foot Rule: Mobile Equipment and Overhead Lines
Best practices for maintaining safe clearances between heavy machinery and energized distribution lines.
Operating mobile cranes, excavators, and elevated work platforms (MEWPs) in the vicinity of overhead power lines presents a massive, often fatal electrocution hazard. The operator inside the cab is typically protected by heavy steel, but the riggers or ground spotters touching the load exterior will be instantly killed if contact is made.
The 10-Foot Rule (OSHA Standard)
OSHA strictly mandates a minimum clearance of 10 feet for any equipment operating near distribution lines up to 50kV. For lines over 50kV, that minimum distance increases significantly.
Why Distance Matters
Electricity does not always require physical contact to kill. High-voltage transmission lines can “arc” or jump through the air to a grounded object (like a steel crane boom) if it gets too close, especially in humid or dusty environments.
Spotter Protocol
- Dedicated Spotters: If a boom must operate anywhere near the 10-foot boundary, there must be a dedicated spotter on the ground.
- No Other Duties: The spotter’s sole responsibility is observing the boom’s distance from the line. They cannot be directing traffic or manipulating the load simultaneously.
- Emergency Egress: If contact is made, the operator must remain inside the cab (unless it is on fire). If they must exit, they must jump clear, landing with both feet together to avoid step-potential electrocution.
Look up, verify clearances, and always use a dedicated spotter.