100 year old rivets

[corrosionman]

I'm trying to estimate cost of some repairs on a 100 yr old steel bridge and need to remove a couple of hundred rivets ( 3/4 inch size and very corroded) but we must reuse the holes for galvanised bolts. The old rivets can be removed by drilling them out, or by carefull use of a blow torch, or possibly by grinding off the head and punching etc etc. This job has a very tight time schedule due to road closures etc so Please has anyone any comments that might help us start with the best method?
Fortunately this is not heavy structural work but just some "service boxes" affixed to underside of a high level bridge which passes over a main road.
Thanks in advance Corrosionman

 

[kelowna]

In a previous job we used a chisel tip on a compressed air tool. The chisel was applied next to and paralel to the steel plate and ite sheared the head of the rivet off.

We had no problems, and we had to remove quite a few!
It was fast, painless and very effective, although incredibly noisy.

As I type I have one old rivet on my office I kept as a memento.

The other methods you descrive sound effective but slower.

 

[corrosionman]

Kelowna Thats a good idea but did you then punch the rivets from the plates easily or were they fused in with rust ? Our bridge is 100 yards from the North Sea !
CM

 

[kelowna]

After shearing the head on one side they came out very easily. We did not have as much corrosion as you seem to have, but we did have quite a bit, plus several layers of paint. I guess a spike and a hammer would take care of the difficult ones.

Our biggest problem was to avoid the workers removing too many bolts at the same time. We had a limit about how many rivets could be removed at a time. Obviously the more you remove, the weaker the connection/composite member becomes.

 

[bridgebuster]

Agree with kelowna; that's how I've always seen it done; chip the head off and punch it out. One thing to consider: will anyone object if the rivets go flying any which way? When I was on projects in urban areas we had to make sure the contractor had someone on the opposite side of the member to keep them from getting away.

Once in a while you might have to burn the head off. If so, make sure they use a wide tip on the torch. I worked for an old time who used to say "I don't trust iron workers with torches."

 

[kelowna]

Bridgebuster, you are talking there! Ironworker and torch on the same sentence scare me! If I had my way, the torches would be locked with me having the only key!

Rivet pieces flying away were not a problem for me, noise was! And obviously you always have to remember that 100 year old rivets have 100 year old paint, that is, lead paint, but that is another issue altogether.

 

[wiktor]

Shearing the heads off with the flat chisel and punching them out seems to be the best method.
TRo speed the producion you may also use hydraulic shears.
I will highly disadvice use of torches, as all old bridges were painted with the red lead as primer, and the fumes during torching could be a major safety issue.

 

[corrosionman]

I've had tremendously helpfull comments but our project is thwarted yet again - - the service chambers we plan to renew contain telephone cables approx 1.5 inches dia - -like a lead pipe with 400 wires inside - - an old telephone Engineer thinks they are from 1940 (or earlier) and simply to touch the risks breaking some of the internal wires - 70 years ago during the war the lead was very poor quality and is very brittle. Due to extreme corrosion the chambers have sizeable holes in them and are half full of pigeon bird "droppings" in which the lead cables are buried.!! Dare I ask, please has anyone any comments.
Corrosionman

 

[hokie66]

Sounds like the bridge structure is not the only thing which needs repairing. The telephone cables should be replaced. You could expedite this by chopping through them, but probably best to go through the proper channels.

 

[bridgebuster]

First thing, you have to get the pigeon $#!+ out of there because it's a SERIOUS health hazard. It may be possible to split the lead ducts and place the wires in new ducts. In NYC splitting ducts is not unusual.