A mobile crane with a 150-foot boom is operating near power lines. What is the minimum safe distance that must be maintained from energized power lines rated at 50kV?
Correct Answer
D) 10 feet
For power lines rated up to 50kV, OSHA requires a minimum clearance of 10 feet for crane operations. Higher voltage lines require greater clearance distances.
Why This Is the Correct Answer
OSHA 29 CFR 1926.1408 specifically requires a minimum clearance of 10 feet for crane operations near power lines rated up to 50kV. This safety standard applies regardless of the boom length and is designed to prevent electrical contact that could result in electrocution or equipment damage. The 50kV rating falls within the voltage range that requires exactly 10 feet of clearance according to federal safety regulations.
Why the Other Options Are Wrong
Option A: 6 feet
15 feet exceeds the required minimum distance for 50kV lines, though it would be acceptable as it's more conservative than required.
Option B: 20 feet
20 feet is the minimum clearance required for higher voltage lines (over 50kV up to 200kV), not for 50kV lines.
Option C: 15 feet
6 feet is insufficient clearance and does not meet OSHA requirements for 50kV power lines, creating a dangerous electrical hazard.
Memory Technique
Use '50-10 Rule': 50kV and under = 10 feet minimum. For higher voltages, add 4 inches per 1000 volts over 50kV.
Reference Hint
OSHA 29 CFR 1926 Subpart CC - Cranes and Derricks in Construction, specifically section 1926.1408 Power line safety
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