Rusty tower questions

Discussion in 'Tower, Rooftop and Antenna Installation' started by Ed Murray, Mar 25, 2009.

  1. Ed Murray

    Ed Murray Friend of the Community

    The company I represent has an inventory of approximately 250 towers most of which are in the 35-40 year age range. We have a climbing inspection performed at a 4-6 year interval. I have been asked to begin reviewing the inspection reports and photographs to develop a plan/budget to correct any problems/issues found. If required, the towers were originally painted but over time virtually all have been converted to strobe lighting and painting is a thing of the past. I am seeing a lot of rusty tower members, U bolts on antenna supports, hose clamps, guy wire saddle clamps, etc. In a few cases the weep holes on diagonal members are showing signs of internal member rust present.

    Questions: 1)Is there any method to determine how severe the rusty U bolts, saddle clamps, etc is? Is failure imminent?

    2) Is there a method to determine how severe the structural member rust is? How much life is left in the member? That's probably a hard one to address given a host of factors but it's the degree of rust I concerned about.

    3) It there any sacrifice in strength in replacing [formerly] galvanized U bolts/nuts etc with stainless steel vs replacing with new galvanized?

    4) What about rusty guy wires? I am seeing a wide variety of situations ranging from one strand on a wire rusty, to several strands, to all strands, to only one wire at an elevation, to all wires at an elevation to all wires at all elevations.

    Thanks in advance for your input.
  2. Allen Hughey

    Allen Hughey Friend of the Community

    Ed, I have been in this business for over 10 years. I work alot with old towers and hope that I can shed a little light on the matters for you.

    There really is no way other that a visual check to determine the severity of a rusted bolt, member or guywire. You can perform an ultrasound on rusted tubular members that can give you some clue as to the extent of the rust inside the member but, the services are usually more costly than the replacement of the member itself. Ultrasounds only measure the thickness of the steel. If you know what the thickness was from an Asbuilt Drawing then an ultrasound can help you determine an "average" rate of corrosion. I say average because an ultrasound does not check every square inch of the structure. Usually you only check each tower leg in three areas (top, middle and bottom) when you perform and ultrasound. To check every square inch would cost so much I figure you would be better off to just replace the entire structure. But lets face it, with tight budgets set in place that is not an option for you.

    Next concern would be the replacement of galvanized hardware with stainless steel. I have run into alot of this in the last year up in Kansas and Colorado. A customer of mine had used stainless steel hardware in the past for all attachments on their microwave antennas. The problem with stainless is that when exposed to extreme cold temperatures the stainless steel u-bolts tend to break in half. This is something that I have never seen with the galvanized u-bolts. I had to replace 50 or more u-bolts last year alone that were stainless steel.

    Finally to the rusted guywires. Just like with the tower members I dont think that there is any one way to determine how severe the rust can be on a guywire. The best advice that I can give you here is get them replaced. Start with your worst towers first. Schedule a few each year until you can get the situation under control. New guywires can usually under normal circumstances last at least 25 years before they start to show even the slightest signs of rust. Depending on the size of the guywire and the hieght of the tower, guywire replacement is not all that costly. A full replacement on 15 wires usually only takes 2 to 3 days and add the cost of materials you are still looking at $10,000 to $15,000 for a reguy. I would consider the cost of losing the tower to be much more significant.

    If you have any more questions I would be glad to help you.

    Allen Hughey
    H & H Tower Services
  3. JerBo

    JerBo Friend of the Community

    My $.02 cents..

    Stainless steel has one more inherent flaw.
    Stainless steel is soft, although hard to machine, it is not always as strong as steel, and when you get some Hercules type tech who does not apply anti seize and over torque's it, it is very difficcult to remove.
    The threads gall and god bless the guy who mixes carbon steel and stainless steel hardware. That is even worse.

    Rule of thumb is - if you have to ask, you probably don't know in the first place.

    People who works on towers and riggers has to at the very least, be qualified to perform the functions of their job before they should ever be left on the job site..
    I think too many people are side stepping the issue here.

    As a start, here is a little publication for you to read...

    Once you become proficient in these tasks - you should have all of your crew trained to operate as a tower crew with this knowledge and should have a lead man who can direct all workers as per the safest way to perform these functions.

    As you can see - part 1 - General Rigging Principals covers some of this and is probably the most important of all the material in this web site - else they would have put it someplace else...

    This should be the bare mininum training that each member of the crew should have before working on any crew.

    You might also contact a tower manufacturer and take a tour of their facilities to see how a new tower is constructed and take a training course - to show you how to perform inspection functions.

    Rule of thumb #1
    If the tower is rusty - do not climb it.

    Rule number #2
    If the tower is bent - do not climb it.

    Rule number #3
    If the guys are not properly attached or tensioned - do not climb it!

    Tower is CHEAP!

    How much is your life worth?
  4. Vizsla

    Vizsla Friend of the Community

    If it is a hollow leg tower and you see what you believe could be some serious rust in your report, invest the money to have the company revisit the site and do an ultrasonic wall thickness test. It's the only way of telling if the leg needs replacement or repair.
  5. JerBo

    JerBo Friend of the Community

    A trick I seen performed before was if you can remove a tower bolt and drop a camera down the hole near the top - you can look down the tower leg.
    The problem with tower inspection of Rohn type towers is that sometimes the tower is laid down for a period of time before it is installed. Bugs and spiders tends to sneak inside of the tower leg and build nests. The outside of the tower looks just fine, while the inside is rusted and no good in one area.
    Same is true if the weep holes are corroded or blocked...

    Many a tower climber was injured or killed when they climbed the tower deemed to be safe. Took it down with a Gin Pole, got to the last 30'.. Decided to cut the guy wires and the tower snapped at the base and fell.

    A tower is like a egg standing on end. All of it's strength depends upon it being perpendicular and straight. When you remove the guys - it falls apart...

    Many a tower crew will tell you about a tower that was hit by an automobile, where one leg was missing, but it was still standing straight. A welding crew came in, cut out the bad section, welded in the new section, added some paint and it was as good as new....

    That was done with sheer faith...

    Other towers with ice on the guys, and a strong wind came along and the tower fell down - not months after the annual inspection.
    Why did one stand while the other fell - just because of the forces working against it.
  6. spudw

    spudw Friend of the Community

    I'm glad that some of you guys are concerned about rusty towers and guy wire. Many tower owners know that their towers are rusted but they will not do anything about it because no one requires them to maintain them. If a building inspector came by a building that had serious cracks in the walls he would site them. The difference is with towers is that the owner knows they will never be inspected and will continue to have climbers on them even though it might be unsafe.
  7. HAL9000

    HAL9000 First Time Poster

    Not trying to date myself, but I remember when Strobes were becoming used more often, and tower owners felt they could reduce the operational expense of the tower by not painting or replacing bulbs. They also assumed that there would be no need to have regular inspections either. Now you are getting a new generation towers that have not been maintained like their predessors were in the past. Towers are not designed to fall, they are designed to stay erect. The key to keep the tower up is to make sure it is within its engineered paramaters, inspected and maintained on a regular and consistant basis.

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