Transmission Tower - Leg Rust

[speedyse86]

I work for a utility and a few of our towers, that sit in low areas, are rusting at the groundline of the legs. These are direct bury towers meaning that they dont have a cassion foundation but instead the steel legs have been driven or buried deep in the ground. A couple of the towers were so bad that we had to replace them but there are a few that are not as bad but still need attention. I am trying to generate options as to how to mitigate the rusting problem and to shore up the structural stability of the really bad towers. For the towers that dont have too much deterioration I think we will just clean the legs and repaint them or seal them with galv. For the really bad towers I think we need to do something structrually. Any ideas? I have attached a picture of the really bad leg. As you can see it is a three pronged leg and two of the prongs are rusted all the way through.

 

[hokie66]

Your attachment did not work.

 

[rustbuster]

Your problem is due to differential aeration (oxygen levels) at the soil to air interface. A good coating system is what you need. Check out this explanation or google "differential aeration corrosion"

http://electrochem.cwru.edu/encycl/art-c02-corrosion.htm

Best of luck

 

[unclesyd]

There is an outfit I believe that is from Louisiana that repairs towers. I saw them here a couple of times after the hurricanes replacing parts. The only part that I observed was that they had a purchase on one leg of the tower while replacing a bent section of the leg.

I would definitely look at using a Coal Tar Epoxy for rust prevention on the tower legs.

 

[EdStainless]

A resin coating over double weight galvanize is a minimum for direct burial.
I have seen special backfill used for such situations. Even for driven legs the dug out and back filled then drove through it. You have to get deep enough to get below a level where moisture and oxygen change to be safe.

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