Lightning Protection vs. Lightning Elimination 6

[Loopee]

I'm currently doing a study of existing lightning protection at a chemical plant. I will be making recommendations to the client about maintaining his current NFPA 780 style protection with air terminals, conductors and ground rods.

I have also been reading much about the Dissipation Array Systems promoted by companies that claim to eliminate lightning in the area protected. I've also read many critiques, some in this forum, of these systems that call the techniques non-scientific, snake oil, etc. In fact there seems to be a real war going on over whether this works or not. After all I've read, I have to admit to being a skeptic also.

My question is this: Is there anyone who HAS tried these techniques and believes that there is some merit to them?

 

[Loopee]

Bogeyman - Did you notice that there was a "quiet" time in the "ticking" after an actual stroke?
BJC - Thanks for the anecdote, I think it was interesting that you had 30 sec of warning.
VE1BLL - what exactly do you mean by puddles?

Everyone- I appreciate all the input!

 

[VEBill]

According to what I've seen, the charges coming down from above leap from one spot to another over spans of something like 150m (?). The charges accumulate into 'puddles' (I don't recall what the official name is). These accumulations or puddles are interconnected by ionized channels. Once the major stroke to ground starts, then the puddles discharge in sequence along these channels and onto the same stroke resulting in a pulsation as you've no doubt seen in person.

I'll bet that there are probably many variations on the theme. In other words, lightning probably doesn't feel obligated to always perform in exactly the same way. So any particular simple theory is only correct most or some of the time. I've seen one photo where lighting was hitting the base (bottom) of a very tall tower.

 

[Higgler]

A note on lightning when it strikes the ground near you.

The further your two feet are apart, the more voltage between your two feet and the more current that goes up one leg and down the other, and the more dead you may become. Keep your feet together or better yet, stand on one foot in a lightning storm. If you're traveling take little bunny steps, having one foot on the ground at a time only (just my guess of course). I've heard staying low, but who knows if being 2 feet shorter has much impact.

Regarding the sound of lightning near you, I had a bolt hit about 100-150 feet away on a golf course about 20 years ago. I can still remember how bright the flash was, even in my peripheral vision. Fairly loud too but not horrific. I had my golf clubs in hand and used to carry a 1 iron. "not even god can hit a 1 iron" Lee Trevino used to say, he was right that day.

Kevin.

 

[VEBill]

"A note on lightning when it strikes the ground near you."

Perhaps more accurately, just ~before~ it strikes. ;-)


I've seen advice like, "Be sure to disconnect your antenna during lightning storms."

During ? Yikes !

 

[pauljohn]

I was at sea just of Bermuda when we were overtaken by a huge squall. We saw about 20 to 30 lightning strikes within a 1 or 2 mile radius around us, the closest one about 300 feet away. I never could figure out how a metal mast 100 feet tall in the middle of an relatively flat sea could avoid a strike in those situations.

With respect to the OP. Have you checked the marine stores like West Marine or Boat US, I have installed a few of those lightning dissipators on top of masts, bought from those stores they might have a record or some feedback from users as to their effectiveness.

 

[BJC]

Look up Saint Elmos fire.
A friend of the family was in the Pacific in WWII. At one tiem the whole fleet he was in was glowing with St. Elmos fire. HE said every ship was clearly visable even though it was a moonless night. Extra watches were put out for submarines.
Gregory Peck gets a handle on St. Elmos fire in "Moby Dick". Good flick if you have never seen it.

 

[Higgler]

I think the salty ocean is pretty darn conductive too and the mast of a ship may not stand out electrically speaking in a choppy sea.

I'd expect that the sea spray due to the wind puts a fine conductive mist in the air too which probably shrouds the ship and hence no strikes. I've been on Norweigen ships Sovereign of the Seas during a lightning storm with light rain, the ship did get a lot of hits, probably 5 or more. Although we were in the bar and things were a little fuzzy by midnight.

Maybe a misting sea water sprinkler system is a lightning strike preventative measure.

kch

 

[FiltrationEngineer]

Here is a link to the plant where the unit was installed:

http://www.pbcwater.com/srwrf.htm

 

[DRsquare]

Just some random comments. Fiberglass sailboats may not have a good ground to the water, although I've read articles recommending grounding the mast. Also, I was biking the Blue Ridge Parkway up around Mt Mitchel when a thunderstorm hit. Crouching along the side of the road was OK, but if I stood up, I could feel things start to tingle. I stayed down.

 

[ScottyUK]

After a lightning strike has travelled through a few thousand feet of air, do you think the GRP hull of a sailboat is going to impede its progress toward mother earth?

We've taken a good few direct hits on the exhaust stacks and cooling tower at out plant, and I've seen other direct hits on a cooling tower visible from my office. It's deeply disturbing when you are out working on a breakdown on the top of the HRSG ([≈] boiler on the back end of a gas turbine) and you see the stack about 30m above you get hit. On reflection the steel structure is probably not a bad place to be in terms of safety, but that was a real brown trouser moment.


----------------------------------

Sometimes I only open my mouth to swap feet...

 

[pauljohn]

"After a lightning strike has travelled through a few thousand feet of air, do you think the GRP hull of a sailboat is going to impede its progress toward mother earth?"


No, the hull is going to get a big hole blown in it if the lightning decides thats the way it wants to go. The problem is no-one seems to be able to predict the path.

Most sailboats I am familiar with have some form of grounding plate from a small bronze plate to large sintered bronze plates to a direct connection from the mast to the lead keel. Although many builders/electricians can't make up their mind if this is lightning protection or corrosion protection.

I have given up trying to predict the path and now simply unplug all electronics that I can and hope for the best. Lightning seems to behave erratically at best. I have seen 1x19 rigging wire with one single strand blackened from a strike, and the rest of the wires with which it is tightly packed apparently untouched.

If the OP is still interested another possible resource could be the cities in S Florida that are installing those spiked dissipators on their lifting bridges and light poles nearby. They would probably have records of strikes before and after installation. When I was there I seem to remember Delray Beach, Fort Lauderdale and Hollywood were experimenting.

 

[RKithil]

NASA tried it. FAA with Office of Naval Research wrote extensively about it. Recently, Mssrs. Uman and Rakov wrote
about "Unconventional Air Terminals..." in a Amer. Meteorological Bulletin. International Committee on Lightning Protection (ICLP) and IEC both have discounted the psuedo-science behind the claims of perfection. See much more at:

http://www.lightningsafety.com

CAVEAT EMPTOR !