Cut down and rethread existing anchors

[Liam Nesson]

Hi All,

We are planning to remove and replace and existing vessel. We plan to reuse the existing anchor bolts, 1 1/4" dia with approx. 8" projection, only the top section of the rod is threaded. We have a short window between removing the existing vessel and installing the new vessel. I plan to use the existing anchor rods, however I would like a contingency plan incase the nuts will not come off. Is it possible to cut the rod at mid height and rethread it on site? I will then add a coupling nut and extend the bar. I have found machines like this on the internet but none for 1 1/4" dia rods that is portable:

https://www.cpooutlets.com/ridgid-6...MIuKO4zKX52wIVSLXACh2ZxgOtEAQYAyABEgIpPfD_BwE

 

[JStephen]

First off, while the vessel's in service, can you go loosen the nuts one at a time to see if they do loosen? They need not be removed, but that should be informative. You may want to remove any paint off the threads and soak everything down in WD40 or equivalent ahead of time, too. And make sure the threads weren't peened or something, too.

Secondly, can you see where the bolt goes into the concrete, and is it corroded there? And more to the point, if you turn that nut and snap the bolt off, then what is your contingency plan?

It might be easier to weld a threaded stud onto an existing bolt than to thread it in place if you do have to rework the bolt.

Also be aware that older hooked bolts usually will not satisfy the embedment requirements for current headed bolts. IE, just because the bolts are the size you need, doesn't mean they're adequate for the purpose.

Long ago, removing lug nuts off dump trucks, we'd: 1) Use the impact wrench 2) Tap on the socket with a sledgehammer while using the impact wrench 3) Use a long cheater bar on a tire tool 4) Tap on that socket with the sledge 5) Heat the nut with a torch, then repeat steps (3) and (4). And at some point in there, it WOULD come loose.

 

[Liam Nesson]

Thanks for the quick response JStephen.

That's a good idea about trying to loosen the nuts early and soaking the bolts first.

No I cant see the base of the rod, if the rod snaps off there is a coupling nut just below the surface of the concrete, maybe I can break the concrete away and remove it. My last resort is to core the rod out.

I will have a look at the thread stud.

You are correct, in the Canadian code its approx. 1/4 of the capacity of the headed bolt.

What effect does heating have on removing a bolt? In my mind I am thinking heating the bolt will make things worse as the metal will expand slightly.

 

[JStephen]

Heat the nut, not the bolt, obviously both get hotter, but that does let things move that wouldn't move otherwise.

 

[BridgeSmith]

If the methods above fail, and a minor amount of the bolt threads can be sacrificed, a cut down opposite sides with a torch or cutting disc followed by some aggressive persuasion with a chisel and hammer should split the nuts.

 

[dik]

Are the anchor rods/bolts weldable? They also have hydraulic 'nut splitters' if you have a lot of them.

Dik

 

[Liam Nesson]

I believe the rods are weldable. That hydraulic nut splitter is pretty impressive, seems to be about $150 dollars to rent for a day so it could be an option.

 

[bones206]

Another contingency option might be to abandon and demo the old bolts and install some new bolts in between the existing ones.

 

[dik]

I believe the rods are weldable.

I believe in the Tooth Fairy... one of the members has a tagline, "Trust, but verify", or something of that ilk... best to confirm before you start.

 

[Liam Nesson]

In the past we have simply cut the anchor rods and put post installed rods in between existing rods, this method reduces that chances of unforeseen work during the small window of time available to replace the vessel. In this instance however we are already installing new rods in between, I didn't provide this information as I didn't want to complicate the original question.

Thanks everybody for your practical input, it has been very beneficial.

 

[CANPRO]

In the pictures it looks like the nuts are partially covered by something on the outside of the vessel, what is that?