[TowerTalk] how much rust is too much?

[Roger (K8RI) on TT]

On 10/13/2014 11:45 PM, Matthew Kaufman wrote:
> On 10/13/2014 8:37 PM, Tim Duffy wrote:
>> Hello Matthew:
>>
>> What is the center to center distance of the legs? It could be Rohn 
>> 25 - not
>> model 45 from the photos.
>
> If my notes are right, I measured it at about 17 inches, and the 
> joints are like Rohn 45 joints, not swaged joints.

I installed 100' of 45GT. It used swedged joints, just like the 25G only 
larger.  The solid leg 45Gs use a circular flat plate joint. It's about 
3" in diameter IIRC, but it's been a long time since I saw one.

Look for pits after removing the rust.  Be extra cautious if there are 
any pits large enough to notice.  There are ultrasonic thickness gauges 
for measuring the tube thickness.    I used to measure a lot of pipes 
and tanks, even with epoxy paint on them.  If there are ANY pin holes in 
the tube or welds, you will need an auxiliary base to hold the tower, or 
a big crane.. A job for professionals.

  73 and good luck,

Roger (K8RI)

>
>>
>> It looks like the dirt trapped lots of moisture around the base. That 
>> might
>> be a problem.
>
> That is exactly what happened. Not sure what percentage of its life 
> was spent like that, but long enough to eat through the galvanizing 
> and get rust going.
>
>>
>> A close inspection of the entire installation by a trained and certified
>> tower professional is defiantly in order. Do not take any chances.
>
> Point taken. But still want to get a rough idea of the right level of 
> professional. Most "tower professionals" aren't structural engineers, 
> and most structural engineers want to defer to the manufacturer of the 
> structure. If we're looking at "yeah, that's more than enough good 
> metal remaining for sure", I'll go with a tower professional. If we're 
> looking at "definitely way too much metal is missing and the bottom 
> section and plate must be replaced" (or "just replace the whole 
> tower") then I'll find a tower professional who likes cranes, I suppose.
>
> Matthew
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-- 

73

Roger (K8RI)