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Repair or replace cracked boom???

Discussion in 'Excavators' started by Kevin Cohrs, May 11, 2021.

  1. JLarson

    JLarson Well-Known Member

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    I grew up in a pipe and tank fab background, that was the original focus of the family biz. Weedburners and a BBQ tank have always been a thing on pipeline rigs, not so much a shop thing at least around here. For me if we're just heating it doesn't make since to waste getting the oxy/acet out, bending/straightening different story.
     
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  2. crane operator

    crane operator Senior Member

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    I've never welded together a excavator boom. The cranes I'm around, range from the dumbest of dumb old iron, to what they tell me is pretty exotic steels in the new ovaloid booms coming out of germany. Most manufactures of the crane booms, don't want to give out much in repair procedures. They just want it condemned. And don't really want to sell new sections to repair any thing either. Or the manufacturer is simply gone. So you do the best you can with what you have to work with- experience and a guess at what might work.

    I've held 1 1/2" - 2" wall 16-24" pipe at a natural gas pumping plant, while they welded all day to make a joint. They would weed burner preheat after breaks and lunch. Everything was stress relieved and xray inspected. But we're talking about a bomb that takes out a couple square miles if things go wrong. So everything is pretty spelled out. Same deal with all the steam pipe at a powerhouse project I worked on.

    I think Dave comes from a manufacturing background, where there's blueprints and procedures for everything. Nobody freelances in a environment like that. John C. has been out in the woods with little in the way of backup, with a welder and a can of 7018 and not much else. But has to get a boom patched back together. Whether there's any procedures or not. I find it interesting to read both perspectives.

    As far as the original issue- I think Case is going to mess with you for months on end trying to get any kind of a repair procedure, and you may get nothing from them at the end. Its not like your buying 10million in equipment a year from them- you aren't even the original purchaser. I think they're going to tell you to pound sand. I'd cut it open and patch it up inside and out and hope for the best, but I'm just a dumb old farm kid.

    I know you've got some health issues right now dave, but just because someone disagrees with you, doesn't mean they are wishing ill for you. They just don't agree with you, because they are coming at the job from a different experience background. It doesn't have to be personal.
     
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  3. Welder Dave

    Welder Dave Senior Member

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    I like your post Crane Operator but John C has a problem with me. He thinks because I'm not a mechanic or welded a boom I have no business responding. He made it personal not me. Don't need to get into the thread where he started the name calling. I am a 40 year welder though so know a little bit about fabrication and steel work. I guess all I was trying to say is that excavator boom repair procedures aren't some special type of procedure that took month's or years to develop. I suspect Cat or whoever else relied on tried and true repair procedures that have been used on structural steel, trailer and bridge type fabrication work for years. I think when you're looking at a potential 10K+ repair because you have to hire it out, you would want the best chance of a successful long lasting repair. Paying a little more for piece of mind is what I'd do. You want to take out some of the steps or cut corners, that's up to you. If you needed a crane boom weld repair you'd have to follow all the steps because it would have to be certified. I agree some OEM's don't want to tell how a repair could be done because they want to sell you a new part. Why not do the same with an excavator boom? You could have had your crane engine rebuilt but chose to get one from Liebherr. I think you made the right choice even though it may have cost you more. I'll bet you had much more piece of mind getting an engine from Liebherr?

    I think most members on here are intelligent enough to know if someone is giving sound advice or not. What's frustrating is when you give good advice and they don't follow it. There was a thread in the TLB forum where this was the case. Every thing laid out in detail and the OP ignores it because he's in a hurry or something. It was a fairly simple repair and it just makes you shake your head. Why bother asking if you're just going to do a redneck fix? I'm just glad I'm not the one paying the bill for the repair.

    This didn't have to become a big heated debate. I'm really sorry it did and apologize to the members reading it. Most of what I posted was because I had nothing better to do laying in a hospital bed. It took my mind off my pain and made me turn my brain on. As far as the pain I wouldn't wish it on anyone. I was taking Dilauded like candy for quite a while. Dilauded is a high strength Morphine and about 8 times stronger. I was taking long acting 12 hour with 2mg booster injections every 2 hours. Dr. said some people abuse it but I really needed it. Compression fractures in 10 of your vertebrae tend to hurt a little. Laughing doesn't work, it makes it hurt more but so did a hiccup. Much better now. Hope everyone takes care of themselves!

    Dave
     
    Last edited: May 18, 2021
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  4. mutti_wilson

    mutti_wilson Well-Known Member

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    Here is a cracked boom repair that an aforementioned YouTube welder just posted. Looks to be worse than yours.

     
  5. The Peej

    The Peej Well-Known Member

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    I like his comment at the end " this is not a how to do it video, this is how I did it"
     
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  6. Welder Dave

    Welder Dave Senior Member

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    The guy is a good welder and good with a gouging torch but I would have used a grinder or even die grinder to clean the gouged edges. There would be a thin hardened edge that may have carbon in it from the gouging. Don't know if there was internal damage as well. Probably would have been good to take a look. I like how he said it is how he fixed it. Customer should have had the top plate replaced like the welder wanted. Could have seen inside that way too. Very nice 7018 vertical up welds. Root. Pass looked to be 5P+ 6010 which would burn little bits of slang out.
     
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  7. suladas

    suladas Senior Member

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    Since there is already a thread I figured i'd post here. I noticed some cracks on my mini hoe where the thumb plate is welded on, nothing bad but figure fix it before it gets worse although I know some of the cracks have been there for at least a year or two . What do you guys suggest is the best for a fix? Just grind out the cracks and weld them back up? Should the thumb plate be welded past the corner?
    IMG_0283.jpg IMG_0281.jpg

    IMG_0280.jpg IMG_0282.jpg
     
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  8. Welder Dave

    Welder Dave Senior Member

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    Pics. Are a little too close up but I'm on a phone. Maybe you can highlight the cracks?
     
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  9. John C.

    John C. Senior Member

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    That is a pretty common failure. There should have been a plate welded to the stick first and then the cylinder bracket welded on top of that additional plate. It might have been OK if the original weld had been whale tailed but no use worrying about it now. You didn't say the model of the machine but on most minis, people will air arc out the cracks and just weld them up. I used to do a three pass stringer when I filled up the crack and grind off the top to about the level of the original plate. I would put the whale tails in after you fill up the cracks to make it last longer before they may show up again. You could spend a bunch of time making it pretty but most owner's just want the machine back working again.
     
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  10. JLarson

    JLarson Well-Known Member

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    That's so small I'd probably just chase the cracks back to good plate with like a 1/8" edge wheel or a pipe wheel on my 6" then weld em up, run at least part way into those half moons, clean up the edge of the bottom plate and off to the next disaster lol.
     
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  11. Bluox

    Bluox Senior Member

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    That guy used 7018 all the way no 5P.
    At some point down the road the owner is going to wonder why the main boom pin galled and took out the bushings.
    Bob
     
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  12. aongheas.macask

    aongheas.macask Well-Known Member

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    Did he disconnect the electronics before welding, why not cover up the exposed hoist ram rods before gouging and welding, it only takes one spark to damage the chrome with associated seal damage
    This looks a decent field repair to allow the machine to finish the job after which the boom should be removed and opened up to inspect the internal damage and then repair welded from the inside first,then externally, in my humble opinion.
     
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  13. Welder Dave

    Welder Dave Senior Member

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    6010 is common for root pass and burns out slag. Coating looked fairly thin on the rods and the 3 dots on the rod tell me it's Lincoln 6010. Arc sound is rougher to. I'd guess the guy has done some pipe welding. Also he talked about a root pass and hot pass. That's common with 6010 too before fill and cap with 7018.

    All that said, who really cares? It's pretty obvious the guy knew what he was doing. Anyone attempting a similar repair would choose what rods they want to use anyway. 6010 followed by 7018 is perfectly acceptable as is all 7018 as long as there's full penetration. If you had access to Mig for the root would be even better because it's easiest to tell when you have full penetration and leaves a very smooth pass on the inside that looks like it was done from that side. Tig would be good but very slow and would require a lot more cleaning. One thing not mentioned is preheat would have been a good idea.

    You really need to stop trying to instigate things that aren't there.
     
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  14. The Peej

    The Peej Well-Known Member

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    Asking because I don't know and respect others opinions here. Could the arc gouging have been enough to preheat?
     
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  15. Bluox

    Bluox Senior Member

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    All the 6010 I've used is red with 3 stripes and 7018 is grey with 3 dots .
    If he pipe welded he would put a 6010 root pass in down hand.
    This guy used the same rod all the way.
    If he really knew what he is doing I don't think he would ground thru the boom pin.
    Bob
     
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  16. Welder Dave

    Welder Dave Senior Member

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    Pipeline is downhill but is a separate specialty type of welding. There is little to no gap and run very hot essentially melting the beveled edges into the root pass. Standard pipe welding usually has a 3/32" to 1/8" gap and a key hole is formed. The root is primarily weld metal. Pressure tests are done uphill usually with a slight whipping motion but some drag the rod up. Pipeline has it's own test. 3 dots actually just mean it's a Lincoln rod. Starting a debate on which rod was used is pointless as either would work for a root and hot pass. 6010 would burn slag out better. 5P+ is a whiteish colour and far nicer to run than the old 5P that is red. The guy knows how to weld. He could have put the ground in a better location but I suspect the pin grounded on the bosses. I doubt it was his first attempt at this type of repair. As far as members on here are concerned it is a good video on repairing a cracked boom. Could it have been better, yes but overall pretty informative.
     
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  17. Welder Dave

    Welder Dave Senior Member

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    Maybe but using a Tempil stick crayon (or temp. gun)) you could ensure it's 200 deg's. or so. Preheating helps slow the cooling rate so there is less stress in the welded area.
     
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  18. Willie B

    Willie B Senior Member

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    No. Preheat serves a few purposes:
    When weld cools it shrinks. This can create extreme tension where weld meets steel. Expand all the surrounding metal before, there is less tension where it shrinks.
    Heating slows cooling. Cooling slower encourages a different crystalline structure making steel tough rather than hard & brittle.
    Heating drives away hydrogen. It's involved, but hydrogen can be compared to PAM in a frying pan, preventing bonding.

    Preheat will involve the entire surroundings of the weld. Temperature will vary. Higher than that needed to drive away hydrogen, lower than that will draw the intended heat treat already in the steel.
     
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  19. Welder Dave

    Welder Dave Senior Member

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    Then there's post heat in some applications. ;)
     
  20. BrianGrenier

    BrianGrenier Well-Known Member

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    Here's a picture of what you might call a poor boom repair: (attachment) IMG_20210611_193649599.jpg
     
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