[TowerTalk] Lightning

[Roger (K8RI) on TT]

GENERALLY:  When the spalling (100# chunks?)is on top, or above the 
surface, it is due to moisture / water in the concrete. In the case 
shown in the first link, that appears to be the case exacerbated by poor 
grounding. Inadequate and poor installation. Rerod cage too near the 
surface and not connected to the tower, or not sufficiently connected.  
Water can get into the concrete a number of ways

It's been my experience, Hams are unlikely to need guy anchor grounding 
as typical practice is to break up the guys with insulators, or use non 
conductive guys and the towers are connected to the rerod cages. Even a 
ring of 3 ground rods should be considered the absolute minimum unless 
you have a substantial UFER ground depending on soil conditions.

I don't have photos, but the last commercial tower I worked on used one 
inch steel rope consisting of many fine strands. With these properly 
tensioned, you could feel no vibration on calm or windy days. The did 
oscillate though.  Hit one with a wrench and the very clear tone was way 
above middle C. That meant there was some substantial tension on those 
cables.

Quite a few times I saw that tower take hits with the lightning jumping 
of the guys to ground 50 feet or more

73,  Roger (K8RI)


On 6/28/2017 Wednesday 9:29 PM, Gene Smar wrote:
> TT:
>     
>       There are lots of other examples and case studies of uber-lightning and
> grounding installations linked from the main page of that site:
> https://www.copper.org/ .  Click the Applications tab, then, under
> Electrical, click Power Quality.  You also can find a series of articles on
> the (copper) Statue of Liberty under Education.  Fascinating site.
>
> 73 de
> Gene Smar  AD3F
>
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Shawn
> Donley
> Sent: Wednesday, June 28, 2017 9:05 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Lightning
>
> Here's one documented case of lightning damage to concrete.  I had posted it
> before but here's a repeat.
>
>
> https://www.copper.org/applications/electrical/pq/casestudy/a6137/a6137.html
>
>
> In this case a concrete guy anchor was damaged. But looking at the pictures,
> this might have been caused by moisture entry due to surface cracking with
> the lightning strike just finishing it off as the current pulse turned the
> moisture into steam. Hard to say. I think the real question is if a
> lightning strike can cause internal damage to a tower concrete foundation
> that you can not easily detect.
>
>
> N3AE
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-- 

73

Roger (K8RI)


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