Repair or replace cracked boom???

[Welder Dave]

When machinery manufacturers use high strength steel & sophisticated welding & normalizing procedures it makes it more difficult to repair. It also makes the probability of a re break greater.

The reason strict procedures need to be followed.

 

[John C.]

Maybe you should start by showing an excavator manufacturer’s written procedure for a boom repair.

 

[JLarson]

Occasionally we'll get a custom deal made from something like 514 (aka T1) but most mass produced stuff if similar to that Cat booms, something like a low grade 572. Typically 7018 or a comparable dual shield or gasless flux is our jam on those repairs.

There's 2 parts to the preheat department, one is of course if the metal requires it, the other is thickness/size of weldment and you should also be thinking ambient temp too if you're doing a field repair. Trying to put good heat into a big ol chunk of cold metal just doesn't work out, get the weed burner first.

 

[Tugger2]

My experience in the mining world is fairly limited . I welded the lip on that shovel bucket that shows my pickup parked in it 45 years ago. You run into thick materials 3"and4" and more ,that bucket lip was about 14"thick manganese alloy .Different alloyed materials welded together. Lots of stress relieving that we would never consider on excavator repairs but is critical on big mining stuff. Two different worlds in the repair business.

 

[John C.]

That's a different animal entirely. Procedures and specifications will come with the parts you purchased. When I was welding all the time I loved that kind of work. Ripper noses, bucket lips, shanks, blade lips and push plates. I suppose I got lucky in that my employers decided I was worth more to them working on hydraulic systems, engines and transmissions. Ship yards here let hundreds of welders go so they became less expensive and I apparently avoided the bad lungs and heavy metal poisoning that shows up in life time welders when they get past their late fifties. Today my hands shake a little too much and my eyes have a lot of trouble in the smoke.

 

[skyking1]

+1 for the weed burner. I start there when I have serious rosebud work to do. I have a 500 gallon propane tank there and a 20 minute drive to town for oxy acetylene bottles.
The big caveat is preheating for welding purposes, propane produces a ton of water vapor in the combustion process.
Just saw your post, @John C.
I miss the cracks about half the time now, really annoying!

 

[Welder Dave]

If OEM' were so good with boom fabrication why are booms cracking in the first place? Why do mining booms get stress relieved? A 450 is a good size machine. Why not repair it like you would a mining size machine? All the work to repair and it cracks again because a step was missed.

 

[Welder Dave]

I'm laying in the hospital and somehow the thread has turned I to a pizzing contest. Good job!

 

[lantraxco]

If OEM' were so good with boom fabrication why are booms cracking in the first place? Why do mining booms get stress relieved? A 450 is a good size machine. Why not repair it like you would a mining size machine? All the work to repair and it cracks again because a step was missed.

Sometimes it's a manufacturing defect, like an automated weld with almost zero penetration, but looks good on the surface, seen it. More likely though, it's operator abuse, long hours of hammer operation, twisting moments from thumb use, or being too lazy to swap that wide cleanup bucket for a digging bucket when that's what you should have on there. And/Or a long stick when you should have a short one on. All of these are actual cases from personal experience, humans are gonna do human things.

 

[Nige]

In my book there is nothing wrong with leveraging procedures & practices (pre-heat, needle peening, run out tabs, post heat, etc, etc) that are obligatory to use in the repair of a much larger machine to do a similar type of repair on a smaller one. I think that it likely increases the possibility that the repair will live long-term.

Many posters have commented that you can’t just weld over the existing repair, so the question then becomes how best to do it in such a way that maximizes the chance of success. Like Dave I can’t see why that thought process should descend into a pi$$ing match.

 

[lantraxco]

In my book there is nothing wrong with leveraging procedures & practices (pre-heat, needle peening, run out tabs, post heat, etc, etc) that are obligatory to use in the repair of a much larger machine to do a similar type of repair on a smaller one. I think that it likely increases the possibility that the repair will live long-term.

Many posters have commented that you can’t just weld over the existing repair, so the question then becomes how best to do it in such a way that maximizes the chance of success. Like Dave I can’t see why that thought process should descend into a pi$$ing match.

Exactly, it's no different than how to change a flat tire, the procedure and time it takes, effort required will vary tremendously based on the make, model, year, tire size, front or rear, etc. Excavator booms, and the exact failure vary so tremendously that each and every failure has to be evaluated and a plane put together, which likely will change some as you open things ups.

 

[Welder Dave]

Also what do you do if there is no repair procedure established by the OEM?

 

[lantraxco]

Also what do you do if there is no repair procedure established by the OEM?

Use common sense, experience, best advice?

 

[Welder Dave]

Can sometimes be hard to know which is the best advice. Would really suck to do a 10k repair only to have it fail because a step was missed or not followed.

 

[Welder Dave]

+1 for the weed burner. I start there when I have serious rosebud work to do. I have a 500 gallon propane tank there and a 20 minute drive to town for oxy acetylene bottles.
The big caveat is preheating for welding purposes, propane produces a ton of water vapor in the combustion process.
Just saw your post, @John C.
I miss the cracks about half the time now, really annoying!

I think the heat is so high the .moisture isn't a problem. Weed burners are the method of choice for most preheat requirements. Inter pass temp. is important too.

 

[John C.]

It all comes down to how much it costs, who is paying the bill and who has to stand behind the fix. On booms and sticks there is no need to get all crazy on exotic procedures, materials and processes. It isn't necessary and even the factories only give you so much money to complete the repairs.

Actually weed burners are not the choice for any weld shop I've worked in or run. Preheat was always done with rose budds and oxyacetylene. As skying1 says, they are a good start when working on big components, but the rose budds come out to get the temps up high and I've never seen a weed burner used to control interpass temps.

 

[Welder Dave]

You haven't been around much welding then. Weed burners heat a much bigger area and preheat isn't red hot. Straightening is but acetylene is lot more expensive than propane. Using it for preheating thick steel instead of a weed burner certainly isn't going to appeal to the person paying the bills.

 

[John C.]

Maybe, but then again, I've actually been paid to put booms and sticks back together again. How about you?

 

[terex herder]

With all respect to your experience John, but acetylene has gotten stupid expensive within the last several years. I remember $20 for 125 ft3, now its over $90 for the same tank.

 

[Welder Dave]

I can actually burn bigger than 5/32" electrodes. And you why wonder people like Tctractor left the forum. If you worked in a vessel shop and used a rosebud to preheat a 3" thick x 10' long shell prior to welding you'd likely be given the boot. Yeah, I worked on stuff a heck of a lot more critical than an excavator boom.
Weld procedure qualifications have been around a long time. An excavator boom would be way down the list but the same procedures that have been established for decades could be followed if you want a repair to last. You seem to like to stir pot. You're not likely to when it comes to welding. Most members are wishing me well and you're trying to start a pizzing contest. Now everyone can see your true colors. Hope you're proud of yourself.