Cranes and Derricks
Nearly 30% of the approximately 350 electrical-related fatalities that occur each year involve cranes and overhead
power lines. Because of the voltages involved, overhead power lines present an extremely high risk of fatal electric
shock. If contact occurs, proper safety
procedures should be followed.
The danger posed by overhead power lines at the construction site is often compounded by other factors, such as
uneven ground that could cause the crane to weave or bob into power lines, and windy conditions that can make the power
lines sway, reducing clearance. To address these risks:
- Identify overhead power lines and mark safe routes where cranes must repeatedly travel.
- Operate the crane at a slower-than-normal speed in the vicinity of power lines.
- When working around overhead power lines, de-energize and ground them, or take other protective measures such as
guarding or insulating the lines.
- If the power lines are not de-energized, operate cranes in the area ONLY if a safe minimum
clearance is maintained.
- If maintaining safe clearance by visual means is difficult, designate a person to observe the clearance and to give
immediate warning when the crane approaches the limits of safe clearance.
- All persons should keep well away from the crane whenever it is close to power lines.
- Do not contact the crane or its load until a signal person indicates that it is safe to do so.
- Use cage-type boom guards, insulating links, or proximity warning devices, but do not substitute for de-energizing
and grounding lines, or maintaining safe clearance.
- While handling equipment or materials by boom near transmitter towers, de-energize the transmitter, or (for
equipment) use equipment with an electrical ground connected directly to the upper structure of the boom, or (for
materials) attach materials to ground jumper cables. Use nonconductive poles having large alligator clips or other
similar protection to attach the ground to the cable load.
Minimum Clearances
|
While Working
|
|
Line Voltage
|
Distance
|
|
50kV or below
|
10 feet
|
|
50kV and higher
|
10 feet + .4 inches for each 1kV
above 50kV
|
|
|
In Transit
|
| Line Voltage |
Distance |
| 50kV and below |
4 feet minimum |
| 50kV to 345kV |
10 feet |
| Over 345kV to 750kV |
16 feet |
|
Procedures To Follow If Contact Occurs
Contact between a crane and an energized line does not automatically lead to an electrical incident. To protect
against electrical shock, the following procedures are recommended:
- The crane operator should remain inside the cab until the lines have been de-energized.
- All other personnel should keep away from the crane, ropes, and load, since the ground around the machine might be
energized.
- The crane operator should try to remove the crane from contact by reversing direction.
Additional Information:
- 1926.550, Cranes and Derricks.
OSHA Standar.
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