Troublesome Anchor bolts in Kenya

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Old 03-27-13, 03:48 AM
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Troublesome Anchor bolts in Kenya

Hello all,

I was hoping I could get your advice on a project I am working on. I work for an organization that installs chlorine dispensers to treat drinking water in remote water points in rural Kenya. The system is essentially a tank that fits inside a housing which is bolted to a PVC pipe. The PVC pipe is filled with concrete and a small base slab is also poured around the base of the PVC as an anchor slab. About 6 in from the top of the PVC there are two holes where we feed bolts through the inside of the pvc and the dispenser housing to bolt the two pieces together. The head of the bolt is flush with the inside of the PVC and the nut/end of the bolt is inside the dispenser housing (so that we can remove the housing if it gets damaged)

This is a picture of the dispenser itself:

This is a picture of how the dispenser housing is bolted to the PVC (note that on these pictures we have added an extra nut to the side of the bolt inside the PVC so that it is slightly more embedded in the concrete. This is not the case for the situation where I am talking about, where the bolt head is flush with the inside of the PVC- this happened before my time and I don't have a picture of this).

There was some unfortunate decisions made early on where the bolt head was flush against the inside of the PVC and we then fill the PVC with concrete to fix the bolts in place. The problem, however, is that since the bolt is not really embedded in the concrete at all and when we need to loosen the nut to change out the tanks, the bolt head breaks free from the concrete and spins in place. We have no real way of accessing the bolt head other than cutting the PVC and removing the entire bolt.

We are now at a scale at which it is likely that we will need to replace approx. 500 dispenser casings. Does anyone have any advice on the best way to do this? Can anyone think of a tool that would allow me to grip the bolt from the threads which provides enough torque that I can remove a rusty nut? (Vice grips are the obvious answer but I was hoping for something that wouldn't damage the threads so we can reattach a housing).

Many thanks for your help!

Best wishes,
Ashley
 
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Old 03-27-13, 04:20 AM
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Ashley, welcome to the forums! From what I understand, you are using carriage bolts through the pipe into the container, and the pipe is filled with concrete, correct? Carriage bolts have no head, but a square collar to keep them in a square hole from turning.

You may be better off using regular hex headed bolts rather than carriage bolts. Using the chase nut is a good idea to keep it all from loosening up. I would also install a fender washer under each nut to help spread out the weight imposed on usage of the container. Fender washers are a bit larger in overall diameter, while the central hole remains the same (looks like 1/4" here). By using the hex headed bolt, even after the concrete is poured, you can grasp the bolt using a wrench, and loosen up the nuts to make your repairs.

I would have the manufacturer of these units substitute hex headed bolts for carriage bolts due to the problems you are encountering. They should also furnish replacements since the carriage bolt idea is not a good one in this instance. You should be able to remove the carriage bolts fairly easily and replace them with hex head bolts since they are breaking away from the concrete anyway.

Keep us informed or ask more questions if this didn't cover all the ground.
 
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Old 03-27-13, 06:16 AM
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Thanks for the kind welcome!

We are actually using hex bolts, but we can't access the head because concrete is poured into the PVC, casting them in place. With a small amount of torque, the concrete directly around them breaks allowing the bolts to rotate in place, but they are unable to be removed without cutting through the concrete in the pvc pipe or cutting the walls of the pvc pipe itself.

We are using fender washers now, just not in the photo I happened to have!
 
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Old 03-27-13, 06:47 AM
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If some of the bolt is protruding past the nut try and get a hack saw or reciprocating saw into the dispenser and cut a vertical slot in the end of the bolt. Then you can put a flat blade screw driver or strip of steel into the end of the bolt to hold and prevent it from turning. Then loosen the nut. Backing the nut over the cut slot should remove or clean up the burrs from cutting to make it easier to re-start the bolt when you put on the new dispenser.

For future installs I would have a local shop weld a washer edge on or scrap of steel onto the bolt heads. It will anchor into the concrete better than a nut and it's cheaper.

Even better is to drill two holes in a block of wood that your bolts will drop into and be held parallel and the correct distance apart. Have the welder weld a scrap of steel across the two bolt heads. Then in the field you insert the two connected bolts into the pipe and add concrete. Welded together they are harder to loose if dropped in the bush and they cannot rotate.
 
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Old 03-27-13, 05:55 PM
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Wait a minute!! I see what is happening, and apologize for not seeing it at first glance. You have your bolts inside the pipe. Run your bolts completely through the pipe, then make your pour. Then, you can hold the hex head on the outside of the pipe, and remove the nuts from within the container. Yes, the bolt will strip inside the concrete, but you will have control of it on the outside of the pipe
 
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