A mobile crane is operating near overhead power lines carrying 35,000 volts. What is the minimum clearance distance required between the crane and the power lines?
Correct Answer
A) 20 feet
For power lines carrying 35,000 volts, OSHA requires a minimum clearance of 20 feet. Lines over 50kV require additional clearance based on the specific voltage.
Why This Is the Correct Answer
OSHA 29 CFR 1926.1408 specifically requires a minimum clearance of 20 feet for overhead power lines carrying between 0.75kV and 50kV. Since 35,000 volts (35kV) falls within this range, the 20-foot clearance applies. This regulation is designed to prevent electrical arcing and electrocution hazards when operating cranes near energized power lines. The clearance distance increases for voltages above 50kV, but 35kV falls in the standard 20-foot category.
Why the Other Options Are Wrong
Option B: 25 feet
25 feet exceeds the required minimum clearance for 35kV lines, though it would be safer, it's not the regulatory requirement and represents unnecessary operational restrictions.
Option C: 15 feet
10 feet is insufficient clearance for 35kV power lines and would create a serious electrocution hazard, as electrical arcing can occur at much greater distances with this voltage level.
Option D: 10 feet
15 feet does not meet OSHA requirements for 35kV lines and would still pose significant safety risks due to the potential for electrical arcing across shorter distances.
Memory Technique
Remember '20 for 50' - 20 feet clearance for voltages up to 50kV, then additional clearance calculations apply above 50kV
Reference Hint
OSHA Construction Standards 29 CFR 1926 Subpart CC - Cranes and Derricks, specifically section 1926.1408 Power line safety
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