Please help resolve a controversial subject being raised on our Construction Site.
Should metal scaffolding be grounded as a foul weather precaution on Construction Sites (Lightning)?
If so what are grounding specifications for the scaffolding? All I get is opinions and no hard facts or reference to a specification.
Appreciate.
TVH
Well if the reason your are asking this question is for the protection of personal located on or close by this scaffolding then I would simply have to say that the grounding of the scaffolding would or could not prevent those who are on it from being injured or killed in the event of lightning striking it, the only preventive measure that would guarantee the safety of those workers is to be in a safe structure located out of the storm.
Lightning is a high frequency and high energy event and does not follow the fundamentals of DC current, and when we apply high frequency theory to the impedances of the grounding and even the metal of the scaffolding, we will find that even grounded there will be voltage gradients at different points that can cause harm to those who might be in this unlucky place, but not only is the voltage a problem, the heat from the strike will also cause those who are close enough to the point of attachment to be burned in a similar fashion as in a arc flash event, grounding the scaffolding would be one of the biggest false sense of protection I could think of in a case like this.
Any one who is working on open metal structures or in this case a scaffold should seek shelter at first sign of any lightning, I spent a major part of my careerer and 3 years at University of Florida studying lightning and I will say this, many do not understand how lightning does not follow the theories of low frequency/DC current, we have had threads on lighting striking a concrete bucket connected to a tower crane mounted to the side of a high rise building well grounded, the bucket was way below the high point of the building or crane and suspended by the crane cable yet the strike from what the report said was to the bucket killing a worker near the bucket, even with the fact that the crane, its cable, and the steel structure was all well above this bucket it still happened.
There have been many cases like this over the years, and yet miss guided people still think that grounding to earth is the holy grail to making everything safe, planes flying high above the earth are not grounded and have the same fate if they are in the path of a lightning bolt, it is not because something is grounded that lightning will strike it, it is the fact that this metal is in the path to earth at the time the charge in the cloud reaches the break down voltage for the charge to flow through the air to earth, if this happens at the time the charge is over the place on earth you happen to be standing, it will take the shorter route through you or what ever else is in that route.
As per your question, I know of no requirement for grounding a scaffold, I feel it can do more harm if it leads workers to believe they will be safe to work on it in a storm.
