removing rivets with minimal damage 3

[CTW]

i'm in the process of retrofitting an old truss with all riveted connections. a couple of the web members (double angles) need to be replaced due to damage, and i was wondering if it's possible to remove the rivets without damaging the gusset plates too much.

 

[pipewelder1999]

Oxy Acet torch tips are made for removing bolt/rivet heads. I have done this on bolt heads and a similar concept is used to remove bearing races and rolled boiler tubes from steam/mud drums.

Heat the head of the rivet till red. Use a large enough tip that you don't have to spend so much heating and use an oxidizing flame. That reduces the heating of the base metal and keeps it from reaching a temperature that it would melt/oxidize. When the rivet reaches a sutable temperature the excess oxygen in the flame will "cut" the rivet.

Oxygen can be applied with a cutting torch but care must be used.

There are probably tools available that are more efficient and I have NO experience with rivets but I have removed other items in close contact with other materials.

G Austin

 

[GRoberts]

You should be able to do this using Mr. Austin's method. I have also seen this method cut a nut off of a bolt & keep the bolt threads in tact. The main idea is to keep the metal you do not want to cut below the temperature required for exothermic reaction with oxygen. I can't remember what it is right now off the top of my head, but when you're out there using a torch, you don't know what temperature you're at either. Also, if the metal you don't want to coat has paint/rust on it, that helps you out, so don't remove it first.

 

[GRoberts]

You should be able to do this using Mr. Austin's method. I have also seen this method cut a nut off of a bolt & keep the bolt threads in tact. The main idea is to keep the metal you do not want to cut below the temperature required for exothermic reaction with oxygen. I can't remember what it is right now off the top of my head, but when you're out there using a torch, you don't know what temperature you're at either. Also, if the metal you don't want to cut has paint/rust on it, that helps you out, so don't remove it first.

 

[CTW]

thanks to both of you for your input.

 

[evelrod]

CTW:

I have cut out "about a million" rivets on the last 40 years(also put IN a few). It is NOT rocket science but it does require skill with a oxy/acct torch. On the trusses we reworked at the old South Gate GM assembly plant I used a #2 or larger scarfing tip to cut the tops off the rivets (mostly 7/8 inch and larger) then a straight tip to 'blow' a hole straight through the middle of the rivet(the skill part I was talking about) then take a small rivet gun (80xx will do) a flat nosed punch and drive it out (bull pin and hammer will work, but is 'unfriendly') The hole is necessary because the rivets upset in the hole and need that little hole to 'swuish' into as you drive it out.
Cutting nuts off bolts without damaging the threads is a skill that I have but most don't. It is an easy trick to learn, but most "just don't have the touch".

In referance to Mr. Austins method---It works ok as long as the inspector will let you put that much heat into the truss. Most will not. I have 'washed' rivets and bolts off this way in demo work, but not too often (I REALLY dislike demo work). AND--Yes there are tools to remove revits but they are mostly in MUSEUMS! Besides, you will probably have a difficult time finding anyone who knows how to use them. LOL

Rod

PS---I will note that when a rivet is removed, quite often the hole will still need to be reamed for a replacement bolt one size larger. A red hot rlivet WILL go into a somewhat less than perfect hole. TAKE CARE, INSPECTORS DON'T LIKE TO SEE "NICKS".

 

[dennis42]

Hi from Australia. I am a teacher of welding and fabrication (for the past 23 years) having "served my time" on the Victorian Railways. Back in the 1950's most repairs to rolling stock were carried out on riveted fabrications as they had been manufactured prior to the arrival/acceptance of welding. I was fascinated to read of the skill in removing rivets with the OAW equipment. I removed thoasands of them over a period of nine years. I was also excited by the "boasting" around removing the nut from a bolt without damaging the botls thread. We, as a group of apprentices, used to practice this as its achievement was a mark of excellence.

As a teacher I often tell my students that if Oxy Actetylene equipment was as portable as a carpenter's saw then it would be carried with the boilermaker at all times. It is certainly an essential piece of equipment to those working in the trade.

 

[wiktor]

Another procedure you could consider is removal of the head using pneumatic hammer w/chisel and hammering the rivet out. This is a common practice in bridge projects. (rivets typically 7/8" or 1" dia)

Torching is equally effective, but presence of lead based paint could be a very serious problem, as removal of the paint could be required by a local code.

 

[evelrod]

wiktor:

I take it you have never actually used this procedure?

I have. I'll stick to the torch, thank you very much.

The pneumatic tool you speak of (large enough to knock the head of a 1" rivet off without destroying the structure or shaking the operator to death) is called a "helldog" for the uninitiated.

Re lead paint---Here in the L.A. area lead paint removal is pretty much required before starting ANY type of rework, not just torch or welding work. Of course there IS always that one job that cheats a way around lead or asbestos problems. I always turned these RAT outfits in to OSHA whenever I ran into them. The workmen never seem to understand that the job will still get done, just much safer for them and their families.


Rod

 

[greendrake]

The abbove information is truly helpful. Thank you. I will be working as an inspector for rivet removal. I have couple of questions:Keep in mind...Bridge built in 1948 7/8 rivets. lead paint. The contractor is propossing exothermic rods and pneumatic methods.
What are some of the common errors or problems i should be looking for with the contractor?

 

[evelrod]

I don't get back to the structural forum very often these days. The further along I go since retirement "in the last century", the less I even think about the "job". Maybe that's good for me, but I did re read all the above and find that it's all good. Should your contractor find a "helldog"(in a museum, perhaps?), have fun finding someone who will know how to use it properly. As to using the cutting torch (I never tried this with a plasma cutter), it works as well today as it did in the 60's when I learned how to do it. Like I said, NOT rocket science but requiring a bit of skill and patience. Just keep an eye out for that "cowboy" that can take a torch and turn it into a "weapon". I know it's not kosher, but I kept a list of the men that worked for me and what their skills were. All too often there was the notation "BB"...bad burner!
Best of luck...hope your contractor is union, it will save you on the "Tums"! ;-)

Rod

 

[greendrake]

thanks for your input. non-union contractor yikes!
I will be a learning curve for all.

 

[bridgebuster]

You can still find helldogs in New York City and UNION ironworkers.

NYSDOT specs prohibit flame cutting to remove rivet heads. Although once in a while it must be done due to access problems. I've seen plenty of rivets removed by a helldog without any problems to the base metal. The one big concern is making sure someone catches the head when it breaks off.

 

[Ingy]

Funny thing, here on the west coast a helldog is an impact wrench and rivet busters are the norm.

My company is in the process of retrofitting the south approach span of the Golden Gate Bridge and it's all being done with rivet busters. In my years doing bridge retrofit work in the Bay Area I can't recall anyone every letting us use a torch except as a last resort on an extremely stubborn rivet or you just can't get to it any other way.