Construction activity and the Code

[iwire]

Here is what a bucket lift suitable for a 45 story building looks like.

Now that makes much more sense, I assumed they were in some sort of personal lift.


Here is some more info about the accident.

It was a frantic scene in Atlantic City Thursday afternoon at the Revel casino site as emergency responders rushed to the aid of construction workers who were struck by lightning. Authorities say two, possibly three workers, were struck just before 4:00 in the afternoon, when a bolt hit a basket used to carry concrete, which was right next to them.

http://www.nbc40.net/news/19124/

"They were up there pouring concrete when the bucket lift they were using got hit by lightning," Brooks said. "One guy got a glancing hit, and he sustained a minor injury. Another guy got the full brunt of it.

http://www.cbsnews.com/stories/2011/09/15/ap/business/main20107067.shtml

 

[T.M.Haja Sahib]

God help us if an AHJ determines a piece of machinery designed to travel under it's own power is a structure that needs to be bounded to earth.

You might as well require all autos and trucks to be bonded to earth.

It is not that all the bucket lifts,autos,trucks and any moving thing all over the world to be bonded and earthed for protection from lightning.That would be ridiculous.It depends on the situation and practicability

 

[T.M.Haja Sahib]

My goal was to determine why the subject lightning side flashed from the bucket lift to the building steel through the unfortunate workers.I tried an explanation through my post no.28.But the post no.39 contradicts the explanation.However,the main purpose of bonding is to avoid the side flash.So something is wrong.Perhaps the polymer bucket of the lift,for which no grounded metal wire mesh was provided on its outer surface and in which the workers were working.flashed over due to dielectric breakdown from lightning strike

 

[don_resqcapt19]

My goal was to determine why the subject lightning side flashed from the bucket lift to the building steel through the unfortunate workers.I tried an explanation through my post no.28.But the post no.39 contradicts the explanation.However,the main purpose of bonding is to avoid the side flash.So something is wrong.Perhaps the polymer bucket of the lift,for which no grounded metal wire mesh was provided on its outer surface and in which the workers were working.flashed over due to dielectric breakdown from lightning strike

Maybe is just the fact that lightning does what it wants to, no matter how hard we try to make it do what we want it to do. I

t often does not behave as we expect it to. It hits objects that our understand of it says it shouldn't hit. I once worked on a house where the lighting struck the under ground phone cable between the house and trees and utility poles. There was no lighting protection system, but there was a TV tower on the house and the grounded "static" line as the top conductor on the utility poles. The point where the lighting hit the under ground phone cable would have been in the "protected" area using the rolling ball area of protection theory.

 

[T.M.Haja Sahib]

Maybe is just the fact that lightning does what it wants to, no matter how hard we try to make it do what we want it to do. I

t often does not behave as we expect it to. It hits objects that our understand of it says it shouldn't hit. I once worked on a house where the lighting struck the under ground phone cable between the house and trees and utility poles. There was no lighting protection system, but there was a TV tower on the house and the grounded "static" line as the top conductor on the utility poles. The point where the lighting hit the under ground phone cable would have been in the "protected" area using the rolling ball area of protection theory.

I am afraid you misunderstood.I do not expect that the lightning to behave always according to the current theory about lightning. I am just trying to understand what happened in the subject lightning incident.I am trying to explain what might have happened on the basis of what is known about lightning by science.For example I am able to guess on the basis of known facts about lightning why it hit the underground cable as described by you.

 

[don_resqcapt19]

I am afraid you misunderstood.I do not expect that the lightning to behave always according to the current theory about lightning. I am just trying to understand what happened in the subject lightning incident.I am trying to explain what might have happened on the basis of what is known about lightning by science.For example I am able to guess on the basis of known facts about lightning why it hit the underground cable as described by you.

You seem to be suggesting that something could have been done that would have prevented the accident in this thread. I am saying that even if every known method of lighting protection would have been installed on this equipment, the accident many still have happened.

 

[T.M.Haja Sahib]

You seem to be suggesting that something could have been done that would have prevented the accident in this thread. I am saying that even if every known method of lighting protection would have been installed on this equipment, the accident many still have happened.

Are you saying that based on post no.39? Is there any other rationale behind what you say? or is it simply based on your gut feelings? Make it clear.It is my conviction that because the workers were not killed/injured by a direct hit from lightning but from a side flash from it,corrective measures can be made to prevent the SAME KIND of accident again.

But my conviction is not based on gut feeling! Go back to the post no.39.Even though the tower of the lift is reliably grounded and bonded to the building steel.The metal bucket of the lift is not:The lightning current had to travel round from the bucket,along the lift rope to the building steel.Instead,the lightning side flashed to the building steel bypassing the above path.So the metal bucket of the lift should be PROPERLY bonded to the building steel as soon as it arrives at the designated location near the building structure.Now the side flash hazard eliminated, the workers may handle the bucket with suitably insulated gloves and boots.

It is by no means certain whether lightning will strike the workers or the bucket.So the safest option is not to do construction activity during or shortly after a thunderstorm.The lightning can also hit without the warning of a thunderstorm.in such rare cases,the above suggested method can save in case of side flash.

 

[don_resqcapt19]

=don_resqcapt19;1337655]You seem to be suggesting that something could have been done that would have prevented the accident in this thread. I am saying that even if every known method of lighting protection would have been installed on this equipment, the accident many still have happened.[/QUOTE]

Are you saying that based on post no.39? Is there any other rationale behind what you say? or is it simply based on your gut feelings? Make it clear.It is my conviction that because the workers were not killed/injured by a direct hit from lightning but from a side flash from it,corrective measures can be made to prevent the SAME KIND of accident again.

But my conviction is not based on gut feeling! Go back to the post no.39.Even though the tower of the lift is reliably grounded and bonded to the building steel.The metal bucket of the lift is not:The lightning current had to travel round from the bucket,along the lift rope to the building steel.Instead,the lightning side flashed to the building steel bypassing the above path.So the metal bucket of the lift should be PROPERLY bonded to the building steel as soon as it arrives at the designated location near the building structure.Now the side flash hazard eliminated, the workers may handle the bucket with suitably insulated gloves and boots. [/quote]
I am saying that we really have no idea what lighting will do and even if we use every know form of lighting protection that the accident still could have happened

It is by no means certain whether lightning will strike the workers or the bucket.So the safest option is not to do construction activity during or shortly after a thunderstorm.

I agree.

 

[T.M.Haja Sahib]

=don_resqcapt19;1337655]

I am saying that even if we use every know form of lighting protection that the accident still could have happened

I would have gladly agreed with you,if you had shown the flaws in my reasoning of how the subject lightning incident could have prevented.But you had not.

 

[K8MHZ]

I would have gladly agreed with you,if you had shown the flaws in my reasoning of how the subject lightning incident could have prevented.But you had not.

It could have been prevented by the workers not being there. That's the only sure way.

Unless the storm came out of nowhere with no warning, the only reason they were there was greed and lack of the application of safety procedures.

I have been on construction projects where we would work in blizzards, windstorms, searing heat and torrential downpours, but everyone had to stop work and seek shelter at the first sign of lightning. To me, that is just common sense.

Your assertion that something could have been done to assure that anyone near that tower would be safe as it took a direct lightning hit is not much more than wishful thinking.

This should be a lesson to all of us. Consider the risk vs. the reward of working on a construction site during a thunderstorm.

I HAVE went home and lost a half day's pay due to lightning, but losing that pay was not the worst case scenario, as this thread has proven.

 

[gadfly56]

Are you saying that based on post no.39? Is there any other rationale behind what you say? or is it simply based on your gut feelings? Make it clear.It is my conviction that because the workers were not killed/injured by a direct hit from lightning but from a side flash from it,corrective measures can be made to prevent the SAME KIND of accident again.

But my conviction is not based on gut feeling! Go back to the post no.39.Even though the tower of the lift is reliably grounded and bonded to the building steel.The metal bucket of the lift is not:The lightning current had to travel round from the bucket,along the lift rope to the building steel.Instead,the lightning side flashed to the building steel bypassing the above path.So the metal bucket of the lift should be PROPERLY bonded to the building steel as soon as it arrives at the designated location near the building structure.Now the side flash hazard eliminated, the workers may handle the bucket with suitably insulated gloves and boots.

It is by no means certain whether lightning will strike the workers or the bucket.So the safest option is not to do construction activity during or shortly after a thunderstorm.The lightning can also hit without the warning of a thunderstorm.in such rare cases,the above suggested method can save in case of side flash.

So what prescriptive or design-based criteria are to be used? Bonding jumpers are usually made as short as possible to increase their effectiveness. Do that, and you can't move the bucket. So, how long do you make the bonding wire? What gauge? See #22, #29, and #40 for the likely success you'll have with a bonding wire. Have you considered the additional hazard of a metal rope whipping about the job site as the bucket is moved? There is no practical way to achieve your end with currently available means and methods. As others have posted, when you get lightning, you get gone.

 

[T.M.Haja Sahib]

So what prescriptive or design-based criteria are to be used? Bonding jumpers are usually made as short as possible to increase their effectiveness. Do that, and you can't move the bucket. So, how long do you make the bonding wire? What gauge? See #22, #29, and #40 for the likely success you'll have with a bonding wire. Have you considered the additional hazard of a metal rope whipping about the job site as the bucket is moved? There is no practical way to achieve your end with currently available means and methods. As others have posted, when you get lightning, you get gone.

First let us see whether we agree with the theory or not (Post no.47).State what the flaws are in it apart from practical implementation.

 

[T.M.Haja Sahib]

I could only imagine with the openings between the bars on this cage how much of the heat from the lightning could reach the person inside, not including the RF and UV radiation that could cause more harm.

I doubt this.As soon as it hits the cage,the lightning current branches into various paths of the mesh like structure of the cage so that current in individual conductors of the cage would not be large enough to cause that effect and the total heat emitted by that portion of the cage nearest to the person doing the experiment would also not be too high.

 

[K8MHZ]

I doubt this.As soon as it hits the cage,the lightning current branches into various paths of the mesh like structure of the cage so that current in individual conductors of the cage would not be large enough to cause that effect and the total heat emitted by that portion of the cage nearest to the person doing the experiment would also not be too high.

It may branch into various paths or it may just punch a hole right through it and vaporize parts of it.

The problem with lightning is that no two strokes are alike. Also, they can be multi-stroke and act like a half million volt electrical jack hammer.

I think I already mentioned that I have seen a pane of window glass with a hole burned through it by lightning. It didn't break the glass, it just melted about a 2 inch hole through it.

Sometimes cars get hit by lightning, even though it's an old wive's tale that they don't. When they do get hit, sometimes not much even happens to the car, other times it blows the windows out of them.

I live in an area where there is plenty of lightning. I get to see what it does up close and personal.

I applaud your efforts to take the time to consider a means to make a safer workplace so long as it's not a means to keep workers on the job in a possibly deadly environment.

If you are really interested in lightning hazard mitigation check out this site:

http://www.protectiongroup.com/Home

This link is the best info a construction worker can heed in a thunder storm:

http://docs.google.com/viewer?a=v&q...pFwUvy&sig=AHIEtbQEqt3yLlZ6kDN3ODYEdOODPmP_uQ

Note that is says DO NOT stand near tall metal structures such as communications towers.

It says DO go inside and ENCLOSED building.

Again, communications towers employ the best bonding and lightning protection known to man. That protection keeps the gear safe, but NOT personnel outside near the tower.

A building being built is not usually and enclosed building. That means during a storm, get OUT of that building.

You seem to be making many assumptions about lightning that just aren't true. Lightning can't be harnessed nor controlled like human generated electricity. There is no amount of insulation that can stop it. Since the actual voltage can't be measured, we have to guess. Conservative guesses are that the voltage can be as low as 500,000 and as high as 120,000,000 volts. The peak power can be trillions of watts. The temperature rises from ambient to over 50,000 degrees in 30 millionths of a second.

Due to it's ability to ionize the surrounding air and make it conductive it's impossible to create a means to guide it to a grounding electrode with pin point accuracy every time. Due to the fact that it pulses and acts like AC it has a 'frequency' which is not stable, in fact changes rapidly which also changes the impedance of any conductor, semi-conductor or insulator.

My contention is that if we can design a lightning-safe tower, we should be able to design shock proof everyday electrical equipment and conductors. FAR more people die from coming into contact with man made electricity than from lightning. If we can't keep people safe from 120 volts, it's really silly to think we can keep them safe from 100 million volts.

The standard safety procedure is the best, IF FOLLOWED, and that is to stop working and get to a safe area. The real problem is not that equipment is ill-designed, it's that the people will not follow the safety procedures.

 

[K8MHZ]

And....

Even if, somehow, perfect equipotentiality is achieved, there is still the issue of the arc blast. An arc blast that can be seen miles away and heard tens of miles away. An arc blast that can shake a building from a half mile away.

What type of PPE would protect a person from a 100 million volt, 10 trillion watt arc blast?

 

[Bompa]

NFPA 780

NFPA 780

The code dealing with lightning protection is not the National Electrical Code, NFPA 70. It is NFPA 780 "Lightning Protection Code".

I have spent some time studying that code but could not say that I know it real well. However, I do not believe that there are any provisions in NFPA 780 regarding lightning protection for a structure during construction, nor do I believe it addresses provisions for protecting portable equipment.

EDIT: I hope I didn't just restate what may have been previously stated and even amplified upon. When I posted this I had read through the first page of posts without realizing there were five more pages. Sorry. I will need to pay more attention next time and not post while drinking a beer.

 

[T.M.Haja Sahib]

And....

Even if, somehow, perfect equipotentiality is achieved, there is still the issue of the arc blast. An arc blast that can be seen miles away and heard tens of miles away. An arc blast that can shake a building from a half mile away.

What type of PPE would protect a person from a 100 million volt, 10 trillion watt arc blast?

If you have statistics at hand of how many people were injured/killed by arc blast of lightning,produce that here as a convincing proof.

 

[T.M.Haja Sahib]

It may branch into various paths or it may just punch a hole right through it and vaporize parts of it.

The problem with lightning is that no two strokes are alike. Also, they can be multi-stroke and act like a half million volt electrical jack hammer.

I think I already mentioned that I have seen a pane of window glass with a hole burned through it by lightning. It didn't break the glass, it just melted about a 2 inch hole through it.

Sometimes cars get hit by lightning, even though it's an old wive's tale that they don't. When they do get hit, sometimes not much even happens to the car, other times it blows the windows out of them.

I live in an area where there is plenty of lightning. I get to see what it does up close and personal.

I applaud your efforts to take the time to consider a means to make a safer workplace so long as it's not a means to keep workers on the job in a possibly deadly environment.

If you are really interested in lightning hazard mitigation check out this site:

http://www.protectiongroup.com/Home

This link is the best info a construction worker can heed in a thunder storm:

http://docs.google.com/viewer?a=v&q...pFwUvy&sig=AHIEtbQEqt3yLlZ6kDN3ODYEdOODPmP_uQ

Note that is says DO NOT stand near tall metal structures such as communications towers.

It says DO go inside and ENCLOSED building.

Again, communications towers employ the best bonding and lightning protection known to man. That protection keeps the gear safe, but NOT personnel outside near the tower.

A building being built is not usually and enclosed building. That means during a storm, get OUT of that building.

You seem to be making many assumptions about lightning that just aren't true. Lightning can't be harnessed nor controlled like human generated electricity. There is no amount of insulation that can stop it. Since the actual voltage can't be measured, we have to guess. Conservative guesses are that the voltage can be as low as 500,000 and as high as 120,000,000 volts. The peak power can be trillions of watts. The temperature rises from ambient to over 50,000 degrees in 30 millionths of a second.

Due to it's ability to ionize the surrounding air and make it conductive it's impossible to create a means to guide it to a grounding electrode with pin point accuracy every time. Due to the fact that it pulses and acts like AC it has a 'frequency' which is not stable, in fact changes rapidly which also changes the impedance of any conductor, semi-conductor or insulator.

My contention is that if we can design a lightning-safe tower, we should be able to design shock proof everyday electrical equipment and conductors. FAR more people die from coming into contact with man made electricity than from lightning. If we can't keep people safe from 120 volts, it's really silly to think we can keep them safe from 100 million volts.

The standard safety procedure is the best, IF FOLLOWED, and that is to stop working and get to a safe area. The real problem is not that equipment is ill-designed, it's that the people will not follow the safety procedures.

You missed the point entirely.My intention was not to devise a lightning protection method and ask the workers to do construction activity in the open using it.My intention was to assert that the subject lightning incident could have been THEORETICALLY prevented using known methods of lightning protection.

''It may branch into various paths or it may just punch a hole right through it and vaporize parts of it.''
''You seem to be making many assumptions about lightning that just aren't true. Lightning can't be harnessed nor controlled like human generated electricity. There is no amount of insulation that can stop it. Since the actual voltage can't be measured, we have to guess. Conservative guesses are that the voltage can be as low as 500,000 and as high as 120,000,000 volts. The peak power can be trillions of watts. The temperature rises from ambient to over 50,000 degrees in 30 millionths of a second.''

You require a study of principle of operation of 'Faraday cage'.

 

[K8MHZ]

You missed the point entirely.My intention was not to devise a lightning protection method and ask the workers to do construction activity in the open using it.My intention was to assert that the subject lightning incident could have been THEORETICALLY prevented using known methods of lightning protection.

''It may branch into various paths or it may just punch a hole right through it and vaporize parts of it.''
''You seem to be making many assumptions about lightning that just aren't true. Lightning can't be harnessed nor controlled like human generated electricity. There is no amount of insulation that can stop it. Since the actual voltage can't be measured, we have to guess. Conservative guesses are that the voltage can be as low as 500,000 and as high as 120,000,000 volts. The peak power can be trillions of watts. The temperature rises from ambient to over 50,000 degrees in 30 millionths of a second.''

You require a study of principle of operation of 'Faraday cage'.

As a licensed radio operator, I am very familiar with a Faraday cage. People think metal automobiles make good Faraday cages. Sometimes yes, sometimes no.



Besides being impractical for the application, the cage does not suppress the devastating effects of the arc blast.

"My intention was not to devise a lightning protection method and ask the workers to do construction activity in the open using it.My intention was to assert that the subject lightning incident could have been THEORETICALLY prevented using known methods of lightning protection."

THEORETICALLY anything is possible.

Consider this, you are trying to protect personnel from one of nature's most powerful and devastating forces, not from a Tesla coil. You assert that there is some way, not being used, to assure the safety of personnel working either in contact with, or a few feet away from a 500 foot tall steel tower that is taking direct lightning hits.

How would you test such a device or system? Zap it with a Tesla coil and just assume it would offer the same protection from a lightning bolt?

 

[renosteinke]

The blast ... a good point, to remember the blast / pressure wave that accompanies a strike.

As an example .... last Spring a strike in close proximity to my home physically blew / pushed in the window. That is, the entire window assembly was pushed into the house, without breaking the glass. (Maybe it's a good thing the mason skimped in tying the frame to the brick structure!) Like a giant hand, the blast pushed against the house.

That's enough of a push to knock a man off a scaffold, or tip a lift- and that's just from being NEAR the impact point, and without any of the electrical or heat damage folks usually think about.

So, sure, wrap yourself up in a rebar 'cage,' paint a bullseye for the lightning to aim for .... and let the pressure wave turn your insides to Jello. Being 'tenderised' is much better than being roasted.

Is a lightning strike survivable? Of course it is- there is no shortage of film footage showing commercial airliners getting struck, while in flight, and continuing on safely. Note that said airliners are in flight at the time; I suspect that the current flowed 'around,' rather than 'through' them. I suspect that would not have been the case had part of the plane been touching the ground.