Power Line Safety and Electrical Hazards
What the exam tests
This domain tests clearance distances, the difference between the default rule and the Table A alternative, spotter duties, and emergency response after contact. Expect voltage-based questions and questions about what counts as part of the equipment.
Core rules
- Treat all power lines as energized. Assume lines sag, sway, and recoil, and that rubber tires, soil, and fiberglass do not insulate a crane from high voltage.
- Under OSHA 1926.1407, the default minimum clearance is 20 ft for lines up to 350 kV and 50 ft for lines over 350 kV. This applies to every part of the crane, load line, load, and rigging.
- OSHA 1926.1408 provides a Table A alternative when the employer meets specific conditions such as a dedicated spotter, planning, warning line, and insulating link. Table A minimums are 10 ft for 0-50 kV, 15 ft for 50-200 kV, and 20 ft for 200-350 kV. Over 350 kV, 50 ft applies.
- If contact occurs, the operator should stay in the cab, warn others away, and try to move the crane clear if it can be done safely. If evacuation is necessary, jump clear and shuffle or hop away without touching the crane and ground at the same time.
Worked example
A crane boom tip will be 16 ft from a 138 kV line. The default 1926.1407 clearance is 20 ft, so the lift as planned is not permitted. The 1926.1408 Table A value for 138 kV is 15 ft, so 16 ft would meet Table A only if the employer has the required dedicated spotter, planning, warning line, and insulating link conditions. Without those controls, the crane must be moved farther away, the line de-energized and grounded, or the lift stopped.
Traps
- Using 10 ft for every line regardless of voltage.
- Measuring from the crane base instead of the boom tip, load line, or load.
- Forgetting that the load and rigging count as part of the clearance envelope.
- Assuming Table A applies without the required spotter and planning controls.
- Believing rubber tires or a wood mat make contact safe.