Boom Pump Near an Overhead Power Line
Ironline Concrete is placing a 36-meter boom pump at a commercial site. A 7.2 kV overhead distribution line crosses the site, and at maximum reach the boom will come within about 8 feet of the conductors. The utility agrees to de-energize the line from 7:00 a.m. to 9:00 a.m., but the pour is scheduled until 1:00 p.m. The pump operator says he has a spotter and will keep the boom 'a few feet' from the line. The line is on wooden poles and is not insulated or covered. The crew plans to use a tag line to guide the boom near the line, and a worker asks whether he can hold the tag line.
1. What minimum approach distance applies to this equipment, and is the operator's plan acceptable?
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The line is 7.2 kV, which falls in the 50 kV-or-below category. The minimum approach distance for equipment such as a boom pump is 10 feet. The planned 8-foot reach is already inside that distance, and 'a few feet' is not a plan.
A spotter is useful, but a spotter alone does not make encroachment acceptable. The employer must prevent encroachment: de-energize and visibly ground the line, maintain the required 10-foot clearance with engineering controls such as a range limiter, or use an insulating barrier or link as permitted. The operator's plan is not acceptable.
2. The utility will only de-energize for two hours. What are the employer's options for the rest of the pour?
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The employer should not default to working inside the minimum approach distance. Options include rescheduling the pour, splitting it into segments that fit the outage, requesting a longer de-energization, relocating the pump or the pour sequence so the boom never enters the 10-foot zone, or using different equipment.
If the line is de-energized, the employer must confirm that with the utility and ensure the line is visibly grounded at the point of work. Until that confirmation, treat the line as energized. If work must continue near the line, maintain the minimum approach distance and use engineering controls, not just a spotter.
3. Can the worker hold the tag line? What controls are needed?
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No, not as described. If the boom contacts the energized line, the equipment becomes energized and a worker holding a tag line attached to it can be electrocuted. The tag line also gives the worker a false sense of control over a hazardous approach.
Use non-conductive tag lines only where they are needed, keep personnel clear of the equipment and the minimum approach distance, and use remote controls or other methods that keep workers away. If the line is de-energized and grounded, the tag-line discussion changes, but the employer still needs to control the work zone and confirm the de-energization.