A mobile crane with a 150-foot boom is being used to lift materials. What is the minimum distance this crane must maintain from overhead power lines carrying 50 kV?
Correct Answer
D) 20 feet
OSHA 29 CFR 1926.1408 requires a minimum clearance of 20 feet from power lines up to 50 kV. For lines over 50 kV, the distance increases by 4 inches for every 10 kV above 50 kV.
Why This Is the Correct Answer
OSHA 29 CFR 1926.1408 specifically mandates a minimum clearance of 20 feet from overhead power lines carrying up to 50 kV when operating cranes and other equipment. This regulation applies regardless of the boom length, as the 150-foot boom mentioned is irrelevant to the clearance requirement. The 20-foot distance is a safety buffer to prevent electrical arcing and electrocution hazards. Since the power lines in this scenario carry exactly 50 kV, the 20-foot minimum clearance requirement applies.
Why the Other Options Are Wrong
Option B: 35 feet
35 feet exceeds the required minimum distance and while it would be safer, OSHA only requires 20 feet for lines up to 50 kV, making this unnecessarily restrictive.
Option C: 10 feet
15 feet falls short of the OSHA-mandated 20-foot minimum clearance requirement for power lines up to 50 kV, creating an unsafe working condition.
Memory Technique
Remember '20 at 50' - 20 feet clearance for up to 50 kV, then add 4 inches per 10 kV above 50 kV
Reference Hint
OSHA Construction Standards 29 CFR 1926 Subpart CC - Cranes and Derricks in Construction, specifically section 1926.1408
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