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Thread: I put oil in electric motor that calls for grease. now what?

  1. #1
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    I put oil in electric motor that calls for grease. now what?

    Got this 3 phase motor. Saw the small plugs in the picture above the bearings, so popped them off and put several drops of oil in. Spun super easy, but nothing was dripping out the bottom hole. Put quite a bit more oil in. Still nothing. poked my Allen wrench in the holes and discovered grease in it that was stopping the oil from running out the bottom. Then I noticed on the nameplate it specifies to use grease...

    1. I put a whole lotta drops of oil in. It was eventually coming out around the shaft. Will this have messed something up? Gotten on the windings? Its not TEFC, so I expected some to come out the venting

    2. What should I do now? Can I just thread a grease fitting in it and use this from here forward? I was thinking of putting grease fittings on the top and pumping until it came out the bottom?

    3. Kind of unrelated: The bandsaw I just bought has a 5hp 3phase motor. It is TEFC and has grease fittings for front and back bearings. Since the motor is totally enclosed, where does the grease go? Seems like it would eventually fill the whole inside of the motor...

    DW

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  2. #2
    Is it just the pictures or are there cracks in the casting through the lube holes at both ends?

  3. #3
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    I think its just the picture. The housing is aluminum

    FWIW, the motor will be used for the idler of a rotary phase converter, so it will never actually be driving anything...
    Last edited by dustin wassner; 07-14-2017 at 8:23 PM.

  4. #4
    Use a Q-tip to get out as much oil as possible, then put "zerks back in. Only about once a year would you need a shot of grease in each bearing. Bearings are the only part of a 3 phase that goes bad, unless you fry the windings. In industrial settings, 3 phase motors are seldom repaired, because the down time cost a lot more than a motor. That's why 3 phase motors are a "dime a dozen" in scrap yards. Almost every one I have bought needed new bearings, which I replaced with sealed bearings.

  5. #5
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    Not knowing how it was designed I would worry about injecting too much grease - excess might not come out the bottom but be forced inside. I don't know how your motor is constructed but my experience with greasing big equipment is low speed pivots that are basically steel shafts in cylindrical holes are typically lubed by pumping grease into a zerk fitting until it is forced out the ends. I can't imagine a motor constructed like this but I've never had a motor that speced grease instead of oil.

    Google "hot to grease an electric motor" gave several links including this:
    https://www.mobil.com/en/industrial/...ng-lubrication
    Or better, take it to a motor shop and ask.

    If concerned with the oil contaminating things perhaps you could dissasemble the motor (or let a motor shop do it) and inspect, clean, and regrease. Seeing how it's made inside might provide a clue.

    JKJ

  6. #6
    I wouldn't worry about the oil. There are no brushes or switches or anything in a 3 phase motor that could get "contaminated".

    I also wouldn't bother with zerks and grease - those holes only serve to grease the bearings, so I'd take the motor apart and replace the old bearings with new, sealed, bearings.

    Taking a 3-phase induction motor apart is a very easy and quite instructive. Not really anything you can break or do wrong.

  7. #7
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    ok thanks all for the input. I think i will shop for bearings but use the motor for now as other machines it will be powering are in need of it at the moment.

  8. #8
    Quote Originally Posted by dustin wassner View Post
    I think i will shop for bearings but use the motor for now as other machines it will be powering are in need of it at the moment.
    check with Fastenal for bearings. Sure they are made in china, but so are most others, including the OEM ones. As for quality, on my daughter's Honda, I replaced a idler pulley bearing ( $17.00 from NAPA.) It lasted about 6 months, but the $1.99 special from Fastenal now has over 200 K miles on it.

  9. #9
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    Sealed bearing should only have about 30% grease fill. A sealed bearing is really designed not to be re-greased for the lifetime of the bearing. I would follow the suggestions of a q-tip to remove as much as oil as possible then replace when needed. The old grease was probably dried out and the oil helped refresh it. Ebay is a good source of cheap bearings if you have time. Also worth buying a bearing splitter to remove the old ones.
    Be aware that motor bearings are often two different sizes.
    Bill

  10. #10
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    Just a comment, on the threephase motor. The bottom of the name plate has instructions on ty way to lubricate.

  11. #11
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    Quote Originally Posted by Patrick Morris IV View Post
    Just a comment, on the threephase motor. The bottom of the name plate has instructions on ty way to lubricate.

    Thanks, Mr. Obvious, you're a lifesaver!
    Jason

    "Don't get stuck on stupid." --Lt. Gen. Russel Honore


  12. #12
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    Quote Originally Posted by Patrick Morris IV View Post
    Just a comment, on the threephase motor. The bottom of the name plate has instructions on ty way to lubricate.
    Another comment, I assumed Dustin knew that since he mentioned it in is original post (and posted the picture of the plate).

    JKJ

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