MASS Electrical Safety and Power Line Awareness 2 — Questions and Answers
Question 1: What is the minimum clearance distance required from power lines when the voltage is UNKNOWN?
- 10 feet
- 20 feet
- 50 feet (Correct answer)
- 100 feet
Correct answer: 50 feet
OSHA requires a minimum 50-foot clearance when line voltage is unknown, ensuring the most conservative margin to cover the possibility of high-voltage conductors.
Question 2: Which OSHA standard specifically governs power line safety requirements for crane and derrick operations in construction?
- 29 CFR 1910.269
- 29 CFR 1926.502
- 29 CFR 1926.1408 (Correct answer)
- 29 CFR 1926.600
Correct answer: 29 CFR 1926.1408
OSHA 29 CFR 1926.1408 is the specific standard addressing power line safety procedures for crane and derrick operations in the construction industry.
Question 3: What is 'step potential' and why does it pose a hazard near an energized crane?
- The mechanical force needed to climb crane steps; it increases risk of falls
- A voltage difference between two ground contact points that drives current through a person's legs and body (Correct answer)
- The electrical resistance of the crane's tracks that prevents proper grounding
- The voltage required to start the crane engine, which varies with temperature
Correct answer: A voltage difference between two ground contact points that drives current through a person's legs and body
Step potential is the voltage difference between two points on the ground energized by a fault current; a person standing with feet apart creates a circuit through their body, causing electrocution.
Question 4: According to OSHA, if a power line cannot be de-energized before crane operations, what must the utility company provide?
- A certified electrician to monitor operations
- Insulation of the lines or a written revised minimum approach distance based on actual voltage (Correct answer)
- A written waiver releasing the employer from OSHA requirements
- An insurance bond covering electrical incidents during the project
Correct answer: Insulation of the lines or a written revised minimum approach distance based on actual voltage
When de-energization is not possible, OSHA requires the utility company to either physically insulate the lines or provide a written revised minimum approach distance based on the confirmed voltage.
Question 5: When operating a crane near power lines, OSHA requires that a specific person be assigned to what dedicated role?
- A qualified electrical lineman to monitor line voltage
- A signal person assigned exclusively to monitor and maintain clearance from the power lines (Correct answer)
- A certified rigger to handle all load connections near the lines
- A utility company representative to authorize each lift
Correct answer: A signal person assigned exclusively to monitor and maintain clearance from the power lines
OSHA requires a dedicated signal person (spotter) whose sole job is to monitor the crane's proximity to power lines and warn the operator when approaching the minimum clearance distance.
Question 6: How does high humidity affect the electrical hazard level during crane operations near overhead power lines?
- High humidity increases danger because moisture improves electrical conductivity in the surrounding environment (Correct answer)
- Low humidity is more dangerous because dry conditions increase static electricity
- Humidity has no measurable effect on power line hazard levels
- Only visible rain, not humidity, affects the risk of electrical incidents
Correct answer: High humidity increases danger because moisture improves electrical conductivity in the surrounding environment
High humidity and wet conditions reduce the insulating properties of air, increasing conductivity and the risk of electrical arcing or shock between energized lines and nearby equipment.
Question 7: OSHA requires the employer to notify the utility company and establish safe minimum approach distances before beginning crane operations within what distance of overhead power lines?
- 50 feet
- 100 feet
- 300 feet (Correct answer)
- 500 feet
Correct answer: 300 feet
OSHA requires employers to contact the utility and confirm minimum approach distances before beginning crane operations within 300 feet of energized overhead power lines.
MASS Electrical Safety and Power Line Awareness 2
What is the minimum clearance distance required from power lines when the voltage is UNKNOWN?