Crane Accidents

Lightning and Crane Safety

08/23/99
I’m an occupational safety inspector in our state labor department, and some questions about lightning safety during crane operations came up during an inspection of a concrete pour for a bridge piling.

A subcontractor had a crawler crane holding a 70-foot long rebar cage in place in a 6-foot wide steel cylindrical form buried in the riverbank. The top of the crane was about 150 feet up, somewhat taller than any of the trees in the area. Three workers were standing on the ground, holding onto either the steel form, the rebar cage, or the crane main line as they guided the hose of the concrete pumper during the pour, which lasted for an hour or so.

A lightning storm began (a rarity here in the Northwest), with lightning strikes every few minutes, mostly at a distance of about 6 miles (33 seconds between lightning and thunder). After a lull in the storm, there were suddenly two lightning strikes within 3000 feet (less than 3 seconds between lightning and thunder). The Weather Service said this storm had thunderheads to over 40,000 feet altitude (exceptionally high for this area).

Based on my experience in high-lead logging, where I knew of chokersetters being struck by lightning in very similar circumstances, I advised the foreman that he should pull the workers away from where they were for 5 or 10 minutes for the storm to pass, but he refused, saying they had to make a continuous pour. I’m trying to decide what advice to give to the subcontractor’s safety department about how to handle future incidents like this.

My questions are:

1. Are there any safety guidelines for situations like this? (I haven’t been able to find anything through my state agency or OSHA, though I may not have asked the right people yet—your group would seem to be the right specialists). I’ve been told the crane operator, inside the metal cab of the grounded crane, wouldn’t be at much risk, but it’s the workers on the ground with their hands on that 150-foot lightning rod and 70-foot deep ground rod that I’m worried about.

2. Does anyone know of any reported accidents in situations similar to this? The logging accident I mentioned was similar, but I’d like to know of anyone else’s experience or documented cases.

3. Are there any good resources for this information, especially including accident reports or statistics?

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One Response

  1. Alex Frech says:

    Hi there,
    I am also looking for some written OSHA or similar regulation for shutdown of crane operation on approach of a thunderstorm in this case a mobile crane with a 200ft boom.

    Did you find anything?

    Regards Alex

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