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Is liquid nitrogen safe?

Discussion in 'Dozers' started by gary808, Oct 30, 2017.

  1. gary808

    gary808 Well-Known Member

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    Is it safe to shrink bearing races in liquid nitrogen?
    Plan on taking them down in a freezer then the nitrogen to fit them. These are about 8" diameter races.

    Any thoughts?
     
  2. Welder Dave

    Welder Dave Senior Member

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    It's common but you have to take precautions like wearing suitable gloves and protective wear. Liquid Nitrogen is about -195C but is used in cooking and other applications as well. No need to put your races in a freezer first. You need a dewar to contain the liquid nitrogen. Mining companies use it to freeze large pins. Depending how much you need to shrink the racers, dry ice is another option and easier to transport. You usually get it in pellets in a burlap type bag and can carry it in a cooler. It's about -70C. Both can cause asphyxiation so make sure you have adequate ventilation. A place I worked at sold it and they said to keep the windows of your car open when transporting.
     
  3. 92U 3406

    92U 3406 Senior Member

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    As long as you're in a ventilated area and wear proper PPE its fairly safe. Tie a piece of wire around the races so you're not reaching into the liquid nitrogen to pull them out once they're frozen.
     
  4. gary808

    gary808 Well-Known Member

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    Okay thanks for the info. Im not to worried about my safety. I've handled it for shrink fitting pins and bushings. Just curious if bearing races would be ok.
    I have used dry ice before on bearing races but the temp dosent give you much time to get it seated before it expands.
    Thanks for the info.
     
  5. Cmark

    Cmark Senior Member

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    You need to be mindful that as the bearing comes back up ambient temperature, water will condense on it. You will have to dry and oil it immediately to stop it flash rusting.
     
  6. gary808

    gary808 Well-Known Member

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    Thanks for the tip, I'll make sure we clean ans oil them.
     
  7. redneckracin

    redneckracin Senior Member

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    I've done 4" press fit bushings that were .003 or .005 oversized with dry ice and it worked great, just make sure if its a vertical bore that you have a way to hold it where you want it while it expands.
     
  8. Old Magnet

    Old Magnet Senior Member

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    Remember that metal gets brittle at extremely low temperatures. I'd limit use to the dry ice.
     
  9. gary808

    gary808 Well-Known Member

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    Thats what's been bothering me. I don't want to have these races crack.
    We will probably just stick to dry ice.
     
  10. td25c

    td25c Senior Member

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    Never did use liquid nitrogen for bearing installation but imagine it would cool a Barley Soda down quick .:)

    De burr & clean up the bore good and we just use old school race driver punch on everything .
    https://store.snapon.com/Oval-BEaRing-Race-Punches-20-Oval-Bearing-Race-Punch-P643668.aspx

    Working on dozer final drives gary808 ?

    Only time I was ever around liquid nitrogen was when we was artificially inseminating cattle .

    It kept the " Bull juice " cool until the rite time .;)
    http://www.selectsires.com/programs...andlingFrozenSemenStraws.pdf?version=20170404

    My God........... I showed the Bull how to do this how many times ?? Hard to find good help anymore .

    LOL ! :D
     
    Last edited: Oct 31, 2017
  11. Cmark

    Cmark Senior Member

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  12. RayF

    RayF Senior Member

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    I've been using liquid nitrogen for around 30 years to install bearings,probably thousands of them. I have broken one bearing. It got stuck and grabbed and we tried to flog it in with a 14 lb hammer. The flange on the bearing broke off.
    A handy rule of thumb for nitrogen is
    Steel bearing shrink .002 per inch of diameter. (4 inch bearing comes down about 8 thou)
    Bronze bearings come down 4 thou per inch of diameter.
     
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  13. hvy 1ton

    hvy 1ton Senior Member

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    Funny you mention that TD, I have some family that had a big part in popularizing AI. My dad swears up and down they used an airstream to haul around the good stuff. Couldn't help but think of the mess if somebody hit that trailer.
     
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  14. td25c

    td25c Senior Member

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    That's pretty cool hvy 1ton ! The Old Man was big into AI as well .

    He could remember doing it when he was a kid back in the late 1950's . Nothing like today but was a start .
     
  15. gary808

    gary808 Well-Known Member

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    Well we got all the bearings seated today. Couldn't get Ln because we have ro provide our own dewar. We ended up getting 10 lbs of dry ice and mixing in a gallon of acetone.
    We got the biggest pot we could find and boiled the expanding parts in oil to 250 and froze the shrink parts.
    Worked our really well, everything just dropped together.
     

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    td25c likes this.
  16. gary808

    gary808 Well-Known Member

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    The bevel gear shaft was to large for the cooler so we did one side at a time.

    We cleaned everything with decently hot oil after to remove condensation.
     

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  17. gary808

    gary808 Well-Known Member

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    Btw the bearings and rads are for a d9h bevel gear shaft and housings and the transmission pinion bearings.
     
  18. gary808

    gary808 Well-Known Member

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    Bevel gear shaft and bearing here. We haven't got the the finals yet but I'm sure we're eventually headed there :/.
    We thought about pressing them in but it was really tough removing the old ones. Even after they were partially split and the housings flash heated. The book called for heat and cooling so we figured it would be easiest. They all ended up just dropping in perfectly I didn't even have to pick up my trusty sledge.
    And boy does that sound like a job haha sounded like a job for Mike row to do a show on!
     
  19. Welder Dave

    Welder Dave Senior Member

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    I don't know if putting hot oil on a very cold part is a good idea. Once the part thaws out would be better.
     
  20. gary808

    gary808 Well-Known Member

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    We thought the same thing so we gave everything about a hour to get to room temp then cleaned it with the oil. The oil was probably 120 to 140. You could touch it but not keep contact.