Construction activity and the Code

[WorkSafe]

And if OSHA happens to apply I do not think there is any requirement to bond or ground a personal lift not being used to service live conductors. (I think there are rules about bonding the frame of a bucket truck while it's boom is up around live wires, this is to protect the ground crew not the guys in the bucket)

I agree. OSHA could get the contractor with a 5a1 General Duty Clause violation if the conctractor knew, or should have known there was a imminate hazard and a employee was killed or injured seriously enough and didn't take the necessary precautions.

I haven't seen anything in OSHA 1910 or 1926 in regards to lightning protection of anything.

 

[hurk27]

Of course,grounding and bonding provision for the components of the manufactured item as a unit is outside the scope of the NEC;it is taken care of by certifying agencies such as UL.But such a manufactured item should be properly grounded and bonded at site.From the subject lightning incident it is apparent to me,it was not done.

To understand lightning one has to understand the high frequency component of lighting, lightning is a variable and there is no one answer to providing protection in a one size fits all type of employment, what could be a low impedance path at DC or even 60/50hz can be in the megs of ohms at some of the frequencies that occur in a lightning strike, there is also the resonating effect that can cause lighting to take many very unusual paths through conductors that will surprise even the most seasoned electrical person, so to say that all was needed is proper grounding and bonding without this understanding is an empty statement, no properly installed lightning system can protect 100% and working in a lightning prone area is a risk many take to get work done, this is not the first time workers on high rises have been killed and wont be the last, remember codes adopted into law have to treated as law, to adopt a code that can not for sure guarantee the safety of these workers but will be giving them a false sense of security is wrong and will always be wrong.

You can't tell a worker "It's ok to work because we have protected you from a lightning strike" and then let him base his judgment to work on this lie! because protecting a person from a lightning strike is impossible to do, maybe some day it will be figured out but its not there yet.

 

[iwire]

I agree. OSHA could get the contractor with a 5a1 General Duty Clause violation if the conctractor knew, or should have known there was a imminate hazard and a employee was killed or injured seriously enough and didn't take the necessary precautions.

I haven't seen anything in OSHA 1910 or 1926 in regards to lightning protection of anything.

I vaguely remember some OSHA reg about weather extremes ....... can't think of it now.:huh: It may have had to do with required PPE.

 

[iwire]

because protecting a person from a lightning strike is impossible to do, maybe some day it will be figured out but its not there yet.

Not a problem, each guy just needs their own Faraday cage and has to keep their hands inside.

 

[hurk27]

Not a problem, each guy just needs their own Faraday cage and has to keep their hands inside.

That might work for the low energy of a telsa coil but I wouldn't want to be in that cage if a full bolt of positive lightning hit it, the radiation of the strike alone could cook you:slaphead:

 

[renosteinke]

Overconfidence? When you select your profession, you choose the manner of your injuries.

Chemical workers get to worry about various cancers. Firemen have smoke inhalation. Policemen get bruises. Electricians fall. That's right, fall. Getting electrocuted is WAY down the list. And- guess what?- if you work outside in the rain, atop tall thing, you get real well aquainted with lightening. Just ask any Forest-service Fire Watcher.

From the news report, it appears that absolutely nothing improper was done. The guys were where they were supposed to be, when they were supposed to be there, and doing what they were supposed to be doing.

Bonding the lift? As if a little copper wire would offer the slightest bit of attraction to a lightning bolt .... when there is this huge mass of structural steel and wet concrete at hand.

Let the poor guys rest in peace ....

 

[iwire]

That might work for the low energy of a telsa coil but I wouldn't want to be in that cage if a full bolt of positive lightning hit it, the radiation of the strike alone could cook you:slaphead:

I don't understand.

If you are in a car that gets nailed you will be fine, why would this be any different?

 

[T.M.Haja Sahib]

And if OSHA happens to apply I do not think there is any requirement to bond or ground a personal lift not being used to service live conductors. (I think there are rules about bonding the frame of a bucket truck while it's boom is up around live wires, this is to protect the ground crew not the guys in the bucket)

Let me digress a bit.A telecommunication metal tower is not usually provided with a conductor along its length for lightning protection because the tower itself can perform its function.But if such conductor is provided it should be bonded with the tower and if it were not bonded to the tower,the impedance of the conductor increases to such a high value that a side flash from the conductor to the tower could happen.
The same kind of phenomenon might have happened in the subject lightning incident:with the straightened out boom of the bucket lift almost parallel with with building construction steel,a lightning strike to the lift might have side flashed to the building steel through the unfortunate workers.
A remedial measure?
The bucket lift should be bonded to the building structure.
If the code does not have a clause from 'Electrical power system point of view',I think it may have a relevant clause somewhere from 'lightning protection point of view',

 

[hurk27]

I don't understand.

If you are in a car that gets nailed you will be fine, why would this be any different?

Back when I lived in Florida I had a neighbor who was in his car with his wife in a storm and was hit by what was found to be a very strong positive stroke, the lightning not only put a hole in it's roof, but as it traveled through the water across the windshield it gave them a very good sun burn and spidered the glass, he said the sparks inside the car from the metal of the roof melting just freaked them out as they didn't know what happened until it was over, it also blew out two tires when it arc to the pavement Though them, other wise they were untouched. 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 know we see some results from the test at camp Blanding, but the test at camp Blanding can not duplicate a full strike as their rockets intercept the voltage buildup way before the lightning has reached its full strike potential, they get close but its always lower then the full potential of a natural strike.

 

[jumper]

Let me digress a bit.A telecommunication metal tower is not usually provided with a conductor along its length for lightning protection because the tower itself can perform its function.But if such conductor is provided it should be bonded with the tower and if it were not bonded to the tower,the impedance of the conductor increases to such a high value that a side flash from the conductor to the tower could happen.
The same kind of phenomenon might have happened in the subject lightning incident:with the straightened out boom of the bucket lift almost parallel with with building construction steel,a lightning strike to the lift might have side flashed to the building steel through the unfortunate workers.
A remedial measure?
The bucket lift should be bonded to the building structure.
If the code does not have a clause from 'Electrical power system point of view',I think it may have a relevant clause somewhere from 'lightning protection point of view',

NFPA 780 is about the closet thing I can find that would relate to this subject. I know little about this code, but it does not seem to apply here.

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=780

 

[T.M.Haja Sahib]

NFPA 780 is about the closet thing I can find that would relate to this subject. I know little about this code, but it does not seem to apply here.

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=780

But it does apply here.Clause 4.21.3 Isolated (non-grounded) metallic bodies deals with this subject.

 

[don_resqcapt19]

But it does apply here.Clause 4.21.3 Isolated (non-grounded) metallic bodies deals with this subject.

I don't see Chapter 4 of that code as applying to portable equipment.

 

[T.M.Haja Sahib]

I don't see Chapter 4 of that code as applying to portable equipment.

That chapter deals with lightning protection of ordinary structures.Whether the bucket lift at site is to be included in the definition of 'ordinary structures' may be decided by the AHJ in future in the light of the subject lightning incident.

 

[PEDRO ESCOVILLA]

i know of a 15 year old girl, who was killed by a lightning strike on a softball field. she was a champion softball player, just happened to be up at bat at the wrong time. maybe the use of "common sense", which, in certain cases, isn't common enough

 

[petersonra]

It is doubtful that a direct strike by lightening will be affected whatsoever by a relatively small wire connected to anything.

I suggest an experiment next time there is lightening in your area.

Take a metal golf club and connect a #6 wire to it with a ground clamp and connect the other end of the #6 to a ground rod (or 50 ground rods for that matter).

Hold the golf club up in the air and see how well the grounding protects you from the lightening.

Being as lightening strikes at ground level are fairly rare you may have to try this many times before you get your answer.

Is there lightening during monsoons?

 

[sameguy]

At the power plant we ground the lifts when working out side but not for lightning.
Would a kite, string, and key work?

 

[iwire]

That chapter deals with lightning protection of ordinary structures.Whether the bucket lift at site is to be included in the definition of 'ordinary structures' may be decided by the AHJ in future in the light of the subject lightning incident.

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.

 

[K8MHZ]

Let me digress a bit.A telecommunication metal tower is not usually provided with a conductor along its length for lightning protection because the tower itself can perform its function.But if such conductor is provided it should be bonded with the tower and if it were not bonded to the tower,the impedance of the conductor increases to such a high value that a side flash from the conductor to the tower could happen.
The same kind of phenomenon might have happened in the subject lightning incident:with the straightened out boom of the bucket lift almost parallel with with building construction steel,a lightning strike to the lift might have side flashed to the building steel through the unfortunate workers.
A remedial measure?
The bucket lift should be bonded to the building structure.
If the code does not have a clause from 'Electrical power system point of view',I think it may have a relevant clause somewhere from 'lightning protection point of view',

A bucket lift is essentially a tower, much like a communications tower. Both have a low enough impedance, due to their size and mass, to shunt a bolt of lightning to the ground. Neither have a low enough impedance, nothing does, to reduce the voltage potential between the tower and other structures or beings in the immediate vicinity.

I'll bet the tower for the lift sustained no damage.

The only way not to get hurt or killed when a tower takes a direct hit is to be far away from it, no matter how resilient it is to lightning. You could be dealing with the best grounded structure on the planet, one that has taken repeated hits with no damage, and still be killed deader than a mackerel if you are touching it when it gets hit, or have enough gradient differential between two parts of your body if you are just nearby.

Bonding, no matter how 'perfect', is NOT insulation.

 

[K8MHZ]

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

Take note that about every story or so, the tower is connected to the building with steel braces, most likely bolted to the structural steel. It doesn't get bonded much better than that.

 

[K8MHZ]

It is doubtful that a direct strike by lightening will be affected whatsoever by a relatively small wire connected to anything.

I suggest an experiment next time there is lightening in your area.

Take a metal golf club and connect a #6 wire to it with a ground clamp and connect the other end of the #6 to a ground rod (or 50 ground rods for that matter).

Hold the golf club up in the air and see how well the grounding protects you from the lightening.

Being as lightening strikes at ground level are fairly rare you may have to try this many times before you get your answer.

Is there lightening during monsoons?

In one of the National Weather Service classes I took, they had a video of a pole with a #6 going to a ground rod getting struck by lightning. The #6 literally vaporized.

A sheet of copper 4 - 6 inches wide, 20 to 30 thousandths thick, will carry a full bolt, if installed properly. Actually, it doesn't carry it, the lighting travels on the surfaces. The trick is the terminations. How do you attach a 6 inch wide strip of copper to a ground rod? Well, there are special connectors.

A sheet of copper 4 - 6 inches wide will also easily carry a bunch of amps at a couple thousand volts. Would you think you were safe if you brushed up against this conductor while it was carrying a couple thousand volts?

Obviously not. Nor would you be safe if you brushed up against it when it was carrying 300,000 volts and about that many amps.

One of the most dangerous misconceptions about lightning protection is that bonding and grounding alone are enough to insure a safe operation by personnel during a direct hit. It is NOT.

You need isolation and surge protection along with equipotentiality. The best bet is to not work during lightning storms.

I have worked on sites where we shut down for lighting and sat in the trailer or went home. It didn't end the world. Maybe it was their policy, too, but the storm snuck up on them. It happens.