A mobile crane with a 80-foot boom is working near power lines carrying 50 kV. What is the minimum required clearance distance?
Correct Answer
B) 10 feet
For power lines rated 50 kV or below, OSHA requires a minimum clearance of 10 feet for cranes and other equipment. Higher voltages require greater clearance distances.
Why This Is the Correct Answer
OSHA 29 CFR 1926.1408 establishes specific minimum clearance distances for cranes operating near power lines based on voltage levels. For power lines rated 50 kV or below, the required minimum clearance is 10 feet. This safety requirement protects workers from electrical hazards including arc flash and electrocution. The 50 kV power line in this scenario falls within the lowest voltage category, making 10 feet the correct minimum clearance distance.
Why the Other Options Are Wrong
Option A: 6 feet
6 feet is insufficient clearance and does not meet OSHA requirements for any voltage level of power lines when operating cranes.
Option C: 15 feet
15 feet exceeds the minimum requirement for 50 kV lines and would be the clearance for higher voltage lines (over 50 kV up to 200 kV).
Option D: 20 feet
20 feet is excessive for 50 kV lines and would apply to much higher voltage transmission lines (over 350 kV).
Memory Technique
Use '50-10 Rule': 50 kV and below requires 10 feet minimum clearance. Think 'Fifty-Ten' as a paired concept.
Reference Hint
OSHA 29 CFR 1926 Subpart CC - Cranes and Derricks in Construction, specifically section 1926.1408 Power line safety
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