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Repair or replace cracked boom???

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

  1. Kevin Cohrs

    Kevin Cohrs Well-Known Member

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    Just picked up a 2016 Case CX490D machine. Bought it right knowing it needs some repairs. Looking for options on how to properly repair this issue on the main boom section. Can a repair shop fix this crack and actually make it last or should I start shopping around for a replacement? If someone were to repair the crack would the boom need to actually be removed from the machine or could it be done while still installed? Also wondering what might cause this issue in the first place? Looking for any ideas or opinions! Thanks
     

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  2. mutti_wilson

    mutti_wilson Well-Known Member

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    I'm no expert but I wouldn't expect just welding that crack to hold even the first time around. It should be grooved out, welded and then plated in my opinion. I'd do the repair with the boom on for sure. Could could use the machine to tighten up the crack if need be. Move the hoses out of the way and do the repair.
     
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  3. Kevin Cohrs

    Kevin Cohrs Well-Known Member

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    Yeah whoever attempted to repair it the first time definitely didn't do a very good job.
     
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  4. Kevin Cohrs

    Kevin Cohrs Well-Known Member

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    Also anyone know what the main reason a boom would crack like this might be?
     
  5. skyking1

    skyking1 Senior Member

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    I've been around two broken booms. One was a 245 loading big ugly Rock on night shift at a damn job. It cracked right through the boom cylinder bosses, broke off and dropped the stick and the end of the boom into the back of a terex.
    I would chalk that one up to just gross abuse.
    The other was a Long reach hoe that I ran after it was repaired. It was broken in the same area more or less actually a little forward of the boom cylinders. Those things are just very flexible and easy to abuse .
    I would be giving the rest of that machine the stink eye because it very well could have taken a hell of a hit.
     
  6. Nige

    Nige Senior Member

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    Usual SOP for cracked booms is to remove from the machine then the boom can be rolled over to make access & welding easier. Repair often involves cutting holes in the box structure of the boom in order to repair cracks in internal bulkheads that can’t be seen. If the internal cracks aren’t fixed properly then any external repairs are literally “papering over the cracks” and are a waste of time and money IMHO. My 2c, YMMV.
     
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  7. mutti_wilson

    mutti_wilson Well-Known Member

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    Looks to me like someone was swinging to the right and smoked something or was beating against something on purpose.
     
  8. John Canfield

    John Canfield Senior Member

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    Check out IC Weld YouTube channel - he does heavy equipment repair and has a few videos of boom/stick welding repair.
     
  9. funwithfuel

    funwithfuel Senior Member

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    Very common with guys who drop boom n bucket mid swing. Waste machines are notorious for this failure. Speak with the dealer, there is a specific repair procedure to follow. As Nige mentioned, there are internal stiffeners or bulkheads. The manufacturer will have detailed information on how to perform that repair correctly and with the right materials
     
  10. red Squirrel

    red Squirrel New Member

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    This can be repaired, I have done it many times. Need to close it up vee it out weld and grind it smooth and plate it top bottom and side. A good welder can do it in place hyd lines and whatever else might be in the way will have to be moved for access.
     
  11. Welder Dave

    Welder Dave Senior Member

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    I think Nige showed how a boom was repaired using the Cat procedure in an older post. Preheat and a competent welder is required but it can be repaired. A really good welder may be able to repair it on the machine but all the hyd. lines and stuff need to be removed. Yes, it needs to be inspected internally. Case/Sumitomo may have a welding procedure too. Even it costs several thousand bucks to repair I think a new boom would be almost astronomical in comparison.
     
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  12. Willie B

    Willie B Senior Member

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    Larry The Cable Guy says: "I believe: Sometimes you gotta wreck the truck to get insurance money to make the truck payment."

    I admit that has nothing to do with this. The good news is you don't have ductile iron. Bad news is this is a BIG machine with power enough to tear itself apart.

    Do NOT try to take a shortcut. Last repair effort was wasted. Might as well use duct tape. Remove it. cut it open. repair all layers. On the innermost layer put backer plates. Use preheat, (I'll leave temperature to other people better informed than I).
    On steel ground clean, and shaped for full penetration use multi pass welds to fill.
    Experts will disagree on process & filler. Some of them will suggest 7018 stick. Others would favor dual shield flux core with shielding gas. My non expert opinion is you need a good fusion with old steel. The very strong fillers will shrink as they cool & tear away from the cold steel. 7018 is famous for its ability to stretch as it shrinks to maintain fusion integrity. I believe basic dual shield wires work as well. It is the ultra high tensile fillers prone to ripping loose from workpiece.

    In any case, find a very competent welder to do this. Amateur efforts will fail.
     
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  13. Nige

    Nige Senior Member

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    Even better if you beat the sh1t out of it with a needle gun after every pass to stress-relieve it. Double duty as it removes the slag at the same time.

    And if you want something even better, Eutectic Xuper Nucleotec 2222 electrodes are the dog’s bollox. Originally designed for welding nuclear pressure vessels they have an elongation factor in excess of 50%. They were our go-to for anything that we thought had the remotest chance of re-cracking. Pricey though.....
     
    Last edited: May 12, 2021
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  14. Willie B

    Willie B Senior Member

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    I'm sure if the censors knew what you said they'd black out most of it. Still, it is good advice.......I think.
     
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  15. Welder Dave

    Welder Dave Senior Member

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    Yes to peening and since it's a big machine may consider having it stress relieved using flexible ceramic heating pads. Some booms come stress relieved from the factory where they are likely placed in a large furnace in 1 piece. A vessel shop near where I live has the largest stress relieving oven in N. America. This is the same company that built an 820 tonne vessel that was transported to site on over 900 wheels. Do it right and it will good or better than new. Do it wrong and it's a big waste of time and money. I personally don't think you need to use the real expensive specialty rods for the repair but need to use something similar to what was used at the factory. Case may be able to tell you what type of steel it is. Something like 8018C3 (1% Nickle) may be suitable. It is used to repair crane booms and the 1% Nickle gives extra toughness. Dual-Shield Flux-Core comes in comparable types to most stick electrodes. I think if you get it repaired properly for under 10K you're doing good. I could be way off on the repair cost though.
     
    Last edited: May 12, 2021
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  16. JLarson

    JLarson Well-Known Member

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    Def repairable, by someone that knows what they are doing.

    Airarc, plasma, and my needle gun are def my friends doing a repair like that, and it is always easier to have have the piece off the machine so I can put it up on heavy stands and move it around.
     
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  17. John C.

    John C. Senior Member

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    It looks like the people who built that boom are the same ones who built the Cat booms that have been failing for years. Nige is correct in that the boom has inherent defects inside that will have to be corrected in order to stop the cracking. Just welding the outside will allow you to use the machine for awhile but the crack will just show up again. You might be able to fish plate the top and sides and have it hold together. That might be an easier than cutting the boom open and fixing what is wrong on the inside.
     
  18. Willie B

    Willie B Senior Member

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    I'm curious, what would one use to fish plate? Certainly not basic mild steel?

    A 15000LB rental machine I've seen several times with broken dipper has been patched several times by the worst welder in the world. It looks to be MIG welded without any effort to cut for full penetration. Then random pieces of irregular shaped rusty steel picked from a junk pile are scabbed over partially covering the break. I'd guess it takes only hours to break it again.
     
    Last edited: May 13, 2021
  19. Nige

    Nige Senior Member

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    This ..............
    Good quality structural steel plate Willie. From memory I think the spec is an ASTM A572 of 42k pounds minimum tensile but without digging for the exact info I would stand to be corrected on that.

    The procedures for weld-repairing a cracked boom usually involves cutting it open for access, attending to the internal cracks, reinstall or replace the plate over the access hole, AND finally installing a fishplate over the outside when everything is finished. A kind of "belt & braces" fix if you will.

    i could go into detail for a repair procedure but it would be without the benefit of knowing exactly where the bulkheads are inside the structure. In this case a section of the top plate a minimum of 12-15" long would be cut out in order to gain access to the inside (it would be replaced by a section of new plate afterwards which gets rid of one of the cracks straight away). The exact length of the piece and the location of the two transverse cuts would depend entirely on the internal design of the structure, and that's where some info from the OEM would be essential before getting the plasma torch out.
     
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  20. Welder Dave

    Welder Dave Senior Member

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    There are a few ways to look at the repair. 1 involves cutting access holes and repairing everything internally and then repairing the outside, then welding the cut out plate(s) back in place. Doing this way and possibly stress relieving would give you a boom close to what the original was without requiring fish plates. The 2nd option is to repair the cracks you can see and add fish plates over the cracked sections. More of a redneck fix and not nearly as good as the 1st option. Also likely to crack again. 3rd option is to repair like the 1st option and also add fish plates. This may be the best option or just overkill??? The good thing is the fish plates wouldn't have to be very thick material to add strength to the area. I think even 1/4" thick higher strength material would add a lot of piece of mind. Fish plates need to have rounded corners where welded on the boom. Oval shape would work. Still need to look at what a whole new boom would cost. I would bet tens of thousands. Fix it right the 1st time or don't even bother trying.