Working Inside 20 Feet of a 46 kV Line
A 50-ton rough-terrain crane is setting steel columns beside a two-lane road. A 46 kV overhead line runs parallel to the crane's swing path. The utility says the line cannot be de-energized for at least three hours. The operator needs to place the boom tip 18 ft from the line to reach the farthest column, and the boom will swing under the line several times. The site has a dedicated spotter available, but the spotter also runs the gate and is often 100 ft away. No insulating link or proximity alarm is on the crane. The line is bare conductor; the weather is clear and dry. The general contractor wants to proceed because the crane will not touch the line. The operator must decide whether to set up, what clearance applies, and what controls are needed before any lift.
1. What minimum approach distance applies to the 46 kV line, and is 18 ft acceptable under OSHA's crane standard? Explain the options.
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46 kV is in the 0–50 kV band, so OSHA Table A minimum clearance is 10 ft. An 18 ft boom-tip distance is beyond 10 ft, so it does not violate Table A by itself. But it is less than 20 ft, so the employer cannot rely on the 20 ft option. To work at 18 ft, the employer must use the Table A option, which requires effective encroachment prevention: a dedicated spotter, a warning line or boundary, and a procedure to stop if the clearance cannot be maintained. The proposed spotter is not dedicated because he also runs the gate, so the current plan is not acceptable. The line is bare and the crane has no insulating link, so contact or arcing is a real hazard.
2. The utility cannot de-energize for three hours. List the controls that must be in place before the crane moves within 20 ft, and identify which proposed control is unacceptable.
Read the worked answer
First choice: have the utility de-energize and ground the line. If that cannot be done within three hours, the employer can use the Table A option with a dedicated spotter who has no other duties and is in continuous communication with the operator. Mark the 10 ft boundary from the line, keep the boom and load outside it, and stop if the spotter loses sight or the clearance cannot be maintained. A proximity alarm or insulating link can add protection but does not replace the required clearance and spotter. The gate duty must be reassigned. The general contractor's argument that the crane will not touch the line is not a control; the standard addresses approach, not just contact.
3. If the spotter must leave for 10 minutes, what must the operator do?
Read the worked answer
If the dedicated spotter must leave, work within the Table A boundary stops. The operator must move the boom and load so that no part can get within 20 ft of the line, or shut down until the spotter returns or the line is de-energized. The operator should not use the gate attendant as a substitute unless that person is relieved of all other duties and properly positioned. The stop-work decision should be documented. If the crane cannot be moved clear, the lift waits. The 18 ft plan depends on the spotter control, so losing the spotter removes the basis for working inside 20 ft.