A mobile crane with a 150-foot boom is operating near overhead power lines carrying 50,000 volts. What is the minimum required clearance distance?
Correct Answer
C) 20 feet
For voltages from 46kV to 72.5kV, OSHA requires a minimum clearance of 20 feet between the crane or its load and energized power lines. This clearance protects against electrical arc and contact hazards.
Why This Is the Correct Answer
OSHA 29 CFR 1926.1408 establishes specific minimum clearance distances based on voltage levels to prevent electrical hazards during crane operations. For power lines carrying 50,000 volts (50kV), which falls within the 46kV to 72.5kV range, the required minimum clearance is 20 feet. This distance accounts for electrical arc potential and provides a safety buffer to protect workers and equipment from electrocution hazards.
Why the Other Options Are Wrong
Option A: 25 feet
25 feet is the minimum clearance required for voltages over 72.5kV up to 345kV, which exceeds the 50kV voltage in this scenario.
Option D: 10 feet
10 feet is the minimum clearance required for voltages up to 50kV, but since this line carries exactly 50kV, it falls into the next higher voltage category requiring greater clearance.
Memory Technique
Remember '50-72 needs 20' - voltages from 46kV to 72.5kV require 20 feet clearance
Reference Hint
OSHA 29 CFR 1926 Subpart CC - Cranes and Derricks in Construction, specifically section 1926.1408 Power line safety
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