160 tonnes of force and the shaft won’t come out!? Ideas?
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  1. #1
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    Default 160 tonnes of force and the shaft won’t come out!? Ideas?

    First of all sorry forgot to take a photo to share... so picture this... it’s a 30 tonne drum from a bleach plant at a pulp mill. It’s all stainless except for the shaft to be removed and very expensive to make ($2 million’ish. Drum is probably 14 foot diameter and 40 feet long

    Shaft that needs to come out is approx 6 feet long and 10” diameter. Sleeve is approx 5 feet long with a 10” ID and 13” OD. Which makes the sleeve approx 1.5” wall thickness. Shaft is solid and gets a spocket mounted so the drum is chain driven.
    Let’s call it a press fit shaft. There’s a lot of weld and gussets supporting the sleeve so removing the sleeve is out of the question.

    We think to install the shaft some of the gussets on the sleeve were cut allowing expansion, then the sleeve was heated and the shaft bathed in liquid nitrogen and inserted

    Now, inside the drum they have mounted a big brace to support hydraulic rams to push this shaft out. It’s been heated with Oxy/acetalyne rose buds from both the inside and outside trying to expand the sleeve enough to push out... IT WONT BUDGE!

    I believed the next step is to add more hydraulics, if that fails then it may have to be repaired in place

    I had an idea today but the engineer will think about it... as it’s under immense pressure from the hydraulic rams what about using a demolition jack hammer on the side of the shaft that’s protruding, perhaps clad in a brass pad on the end not to cause any damage to the shaft...

    A lot of smart cookies on here, any thoughts on the jack hammer or other ideas? Can take a picture in the next day or 2 if needed

    Thanks in advance


    It’s something like this. You can see the gussets on the back of the sleeve on the right side of photo

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    I'm assuming the ends are taken off while you're trying to press these shafts out, correct? So you can press directly against those gussets that are on the inside while the drum is assembled. You may need a larger press. Things of that size at the larger shop I worked in were normally disassembled with heat and a 600 ton horizontal or 500 ton vertical press. If the ends are not removable, looking at it you are going to bend something if you press too hard.

    A jackhammer probably won't do much to help you. In cases where we used an impact for driving, it was usually with the job clamped and braced tightly to a floor plate, then a very large weight (think hundreds to thousands of pounds) would be swung from the crane like a pendulum. This was a very rare occurrence, thankfully.

    If you can't get access to a larger press, mount it up on the machine and cut it out... wouldn't be too much work to make a new stub end. Fastest way to do this would be to cut the shaft (torch, saw, whatever) flush('ish) to the face, then drill it so that it will collapse in on itself.

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    What is wrong with the shaft? If it is a simple bearing diameter then a build up and turn in place sounds the simplest. Any keyways?

    Ed.

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    Quote Originally Posted by eKretz View Post
    I'm assuming the ends are taken off while you're trying to press these shafts out, correct?
    Yes, ends are removed. The drum is completely out of the blue housing and sitting on stands. There are manhole access points so work can be done inside.
    I like the idea of a bigger weight on a pendulum, so far they’ve tried a 16lb sledge from the inside hitting the rear or the jack mount. A little bit of junk gets dislodged from the seam on the outside when it gets hit. Unfortunately space is limited, so whatever is used to hit from the inside needs to carried in through a manhole and swung by hand. On that note maybe a couple anchor points could be welded and a bigger weight carried inside... I like it, thanks

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    Quote Originally Posted by atex57 View Post
    What is wrong with the shaft? If it is a simple bearing diameter then a build up and turn in place sounds the simplest. Any keyways?

    Ed.
    This has been discussed and is plan b. Yes i believe it’s the surface of the shaft needing buildup and machining. Pretty sure there’s a keyway but can’t remember

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    Beyond my garage hobbying but system similar to high pressure oil system that is used when installing large bearings would help tremendously.

    Drill one or more small holes in the middle of the sleeve, thread for high pressure hydraulic fittings and pump high pressure oil between the sleeve and shaft.

    The SKF Oil Injection Method

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    Portable (onsite) welding and machining.....

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    Quote Originally Posted by digger doug View Post
    Portable (onsite) welding and machining.....
    I tend to agree with this. Also with Mattij on trying hydraulic expansion if that route must be taken.

    Remember that many stainless steels have a CTE less than "regular" steel, so once these are an assembly deep freezing is the best way to create differential expansion. [Correction - I was reading off two different charts and mixed my units, so this is bass-ackwards]

    I almost guarantee that the effects you'll get from any impact or inertial shock when trying to separate these parts will dissipate as distortion of metal local to the shock, and so won't give the desired results.

    Not to mention having the risk of going disastrously wrong with harm to nearby people...

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    Something that long and that tight is likely going to score really badly if you begin to move it, mainly because that is the nature of stainless.
    Heating could only work if you did it quickly enough. Like a large torch every 6 inches along both sides of the shaft. If you can't do it quickly, too much heat transfers. Stainless has slow heat transfer, but high expansion, so that works in your favor.

    Shrink fits aren't that difficult to assemble, don't even need liquid nitrogen when you're working across a 10" diameter. Plus, you've got all day to heat the sleeve up. Easy to get .020" expansion while the sleeve is sitting out. Hard going when you try to reverse the process.

    If the gussets were welded on after the shaft was installed, the sleeve bore may be wonky, too, when it comes to putting the things back together.

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    Quote Originally Posted by Milland View Post

    Not to mention having the risk of going disastrously wrong with harm to nearby people...
    There is not earplug enough to wear if standing inside that drum whilst operating
    said jack hammer "steel-on-steel".

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    can you drill into the housing so to intersect with the shaft and hook up a high pressure oil pump and pump oil into the intersect so to separate the shaft from the bore? wild idea

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    Burn the shaft out? ………...a competent OA burner should have little problem - and without damaging anything.

    On edit - it's in a stainless bore - changes are it's galled now and will be galled to hell if you do get the shaft out, so it won't be any good anyway.

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    I'd imagine it was originally built with field machining / welding. Why on earth would you make a giant PITA out of such a job? Seems the least effort way to do such outsize things

    Since it ISN'T a "small" job like this 30 ton, it likely has never been near a lathe in its life
    Attached Thumbnails Attached Thumbnails johnoder_1.jpg  

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    Not for field disassembly. Options are: repair bearing seats in place or sent drum out for repair. A shrink fit between components of those dimensions cannot pressed apart, regardless.

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    Yes a shrink fit of this size can be pressed out, I've done it hundreds of times. In this particular instance though I think I will jump off that particular fence and side with the guys recommending a weld and remachine if that's a possibility. Being stainless, if it was pressed out it would definitely gall and gouge the bore (this is almost certain to happen even if it wasn't stainless). Without a very large press it's not happening. And my reference to driving by impact was merely a reflection, not a recommendation. Nothing you can carry in by hand will knock that out, nor likely do a damn thing except make noise.

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    Quote Originally Posted by Limy Sami View Post
    Burn the shaft out? ………...a competent OA burner should have little problem - and without damaging anything.

    On edit - it's in a stainless bore - changes are it's galled now and will be galled to hell if you do get the shaft out, so it won't be any good anyway.
    Get you a piece of 3/4" or 1" pipe about 20 foot long, hook up O2 line to the end of the pipe, light it and start burning a hole thru the shaft end to end. Yeah, be burning up a LOT of O2 but burning a hole thru the full length of the shaft and let it cool back down to ambient temperature. Won't be able to touch it until the next day, has to cool on it's own. The OD of the shaft will shrink a good .030-.060" and should drop out of the bore of the sleeves.
    They used to do this when they used to rebuild draw works on a drilling rig. I'm sure it hasn't changed in years. Haven't been around any of this stuff in years. Ken

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    I'd really like to see pictures of the actual part and get a better idea of what the needed repairs are before we go further. Any chance of that?

    And what are your resources at your facility?

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    Quote Originally Posted by 4GSR View Post
    Get you a piece of 3/4" or 1" pipe about 20 foot long, hook up O2 line to the end of the pipe, light it and start burning a hole thru the shaft end to end. Yeah, be burning up a LOT of O2 but burning a hole thru the full length of the shaft and let it cool back down to ambient temperature. Won't be able to touch it until the next day, has to cool on it's own. The OD of the shaft will shrink a good .030-.060" and should drop out of the bore of the sleeves.
    They used to do this when they used to rebuild draw works on a drilling rig. I'm sure it hasn't changed in years. Haven't been around any of this stuff in years. Ken
    I agree, when you get to parts that size, messing about just won't cut it, ......so ya have to show the job who's boss

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    I have no doubt if the shaft was centre burnt with oxy it would shrink and come out easily........however ,the length means getting a centre thru cut that doesnt blow out into the mounting would be problematic ,to say the least.....one thing is that the stainless shouldnt burn if the cut does go astray........If my continued employment depended on it,I would go for safety,and get in a reputable onsite boring contractor,and bore the shaft out......IMHO,the structure is not strong enough to use unlimited force without major distortion......no use getting the shaft out ,then finding the assembly is stuffed.

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    I’d give In place machining a call. Personally I would not risk damaging a machine that valuable with out a carefully thought out precise plan.

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