Results 1 to 16 of 16

Thread: a compressor autopsy

  1. #1
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    4,797
    Post Likes

    a compressor autopsy

    reading "commercial refrig for a/c techs" and remembered there's an old compressor sitting in back of shop.
    We had saved it since were curious why was shaking so bad. Old carrier unit w/semi hermetic compressor.

    let oil out of it before started to tear into it and saw metal flakes in oil, so not good there.

    started to take the heads off and found this:
    Attached Images Attached Images   
    Col 3:23


    questions asked, answers received, ignorance abated

  2. #2
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    45,368
    Post Likes
    I went to a class last year...
    They had half a dozen old Carlyles opened up...

    One of them had shattered connecting rods...
    Got to talking to some guys... they said that was probably caused by liquid refrigerant flooding back.
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

    GA's basic rules of home heating and AC upgrades:
    *Installation is more important than the brand of equipment
    *The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
    *Cheap is not good, good is not cheap; however expensive is not a guarantee of quality!
    Choose your contractor wisely!

  3. #3
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    4,797
    Post Likes
    Thread Starter
    After taking more covers off and spilling oil on floor, got to this:
    Attached Images Attached Images   
    Col 3:23


    questions asked, answers received, ignorance abated

  4. #4
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    4,797
    Post Likes
    Thread Starter
    Not sure if piston ring cracked and seized piston, or if this was due to everything else flying apart.
    Attached Images Attached Images  
    Col 3:23


    questions asked, answers received, ignorance abated

  5. #5
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    4,797
    Post Likes
    Thread Starter
    I was wondering the same thing. took reeds apart on some of the heads, but none were bent up. Thought maybe wear was causing on piston to hit head and maybe that broke a rod?
    Col 3:23


    questions asked, answers received, ignorance abated

  6. #6
    Join Date
    Mar 2004
    Location
    Austin, Texas
    Posts
    2,172
    Post Likes
    I would guess that the connecting rod failed first. The piston and everything else was damaged after the rod broke.

    As far as liquid causing the rod to break - maybe. I have seen a lot of internal combustion engines break connecting rods. I am certain those engines NEVER saw liquid in the combustion chamber. So connecting rods can break due to wear and tear without liquid flood back.
    If "I have always done it this way" is a good reason to do it again, how many times do I have to do something wrong - before it becomes right?

  7. #7
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,844
    Post Likes
    Looks like an old O6E Carlyle. If so, those are tough pumps but can be destroyed by either too much oil in the sump, oil return problems, oil flashing off in the sump (no superheat from evap), oil washed off bearing surfaces, etc.

    I've seen how liquid can damage the top of a piston head. Looks like someone took buckshot to it. For your pump I'd wager on oil problems.
    Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.

  8. #8
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    6,067
    Post Likes
    Seeing two rods snapped on the OPPOSITE end of the crankshaft from the oil pump makes me suspect this comp ran out of oil or had significant oil dilution due to floodback. If the oil pump is not pumping enough oil, it won't get to the far end of the crankshaft, the rods bind to the shaft and try to rotate and shear off.

    The way to verify this is to take off the broken connecting rod big ends and see if there's galling on their bearing surfaces and off there's aluminum built up on the crankshaft.

  9. #9
    Join Date
    Feb 2004
    Location
    New Mexico
    Posts
    9,678
    Post Likes
    I once went to a three day Carrier class on semi-hermetic. I remember them saying that even engineers won't always agree on the failure mode.
    What craig1 said I agree with as which bearing failed first is a good clue. I'm thinking bearing wash out due to flood back or oil pump failure.

    Carrier encourages tearing down failures. They don't mind if you don't put it back together, just throw the parts back in any way you can.
    I used to open any failure I could. I've even cut open hermetics on a couple occasions. Especially with burn outs as seeing how the winding's failed can help stop a repeat failure.

    Good job billygoat22
    Give me a relay with big enough contacts, and I'll run the world!

    You can be anything you want......As long as you don't suck at it.

    If a person wants to create a machine that will be more likely to fail...Make it complicated.

    USAF 98 Bomb Wing 1960-66 SMW Lu49

  10. #10
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    4,797
    Post Likes
    Thread Starter
    If I recall, the shaft was clean, don't remember built up metal on it. Did note that the sump heater was bad, and that the motor side was pristine, looked like brand new. Some of the pistons did have a brown tint, but the oil was clear, except for sparkle from metal flakes as it drained out. One piston only (in pics) had a mark like the piston was nearly or touching the top of cylinder. Compressor was still running when pulled out system. Carlyle 06DA...
    Col 3:23


    questions asked, answers received, ignorance abated

  11. #11
    Join Date
    Jan 2010
    Posts
    19,350
    Post Likes
    I agree with the others. Once that rod locks it's self to the crank ( do to loss of oil) it just snaps those aluminum rods right off. That compressor look like it could be rebuilt though.
    Thanks for posting the pics.

  12. #12
    Join Date
    Feb 2004
    Location
    New Mexico
    Posts
    9,678
    Post Likes
    You might take a hard look at the piston wrist pin and the hole in the piston where it goes thru.
    There is an effect called "Opposition of forces" It causes the piston pin boss in the piston to become elongated. The pin in lubed by oil being forced into the top of the pin on the down stroke and to the bottom on the upstroke. This failure is caused from leaky valves.
    If the valves leak there is not enough pressure from the compression to oil the pin. Your piston looks like a possible candidate.
    I once saw a piston that was elongated nearly 1/4 inch before it failed. Refrigeration application.
    Give me a relay with big enough contacts, and I'll run the world!

    You can be anything you want......As long as you don't suck at it.

    If a person wants to create a machine that will be more likely to fail...Make it complicated.

    USAF 98 Bomb Wing 1960-66 SMW Lu49

  13. #13
    Join Date
    Sep 2015
    Location
    NJ
    Posts
    136
    Post Likes
    Have not seen the guts to a compressor in years. Last time it was a copeland rep at a supply house, I enjoyed the pics ty.
    Seeing the piston removed reminds me of when I had an engine blow a piston and it shot out the block.
    Still have the piston somewhere

  14. #14
    Join Date
    Mar 2015
    Location
    ARK.
    Posts
    3,384
    Post Likes
    Compressor was still running when pulled out system.

    1. What happened to our 'posting stuff,Quote,imogies,etc'.
    2. How could this 1 be still running???
    Well, If the rod's 'cleared the rotating asmy and the end bearings were good,I can see why but Man,it would have been obvious...Which I'm sure it was.

    This is 'Interesting' as the destruction is relegated to the 2 cylinders and completely wrecking Them but the others seem ok and still operational but 'ship happens which has no logical explanation.

  15. #15
    Join Date
    Feb 2015
    Location
    South Texas
    Posts
    5
    Post Likes
    it was still running because someone jumped out the oil differential pressure switch.

  16. #16
    Join Date
    Feb 2004
    Location
    New Mexico
    Posts
    9,678
    Post Likes
    I was told in the tear down seminar that when the failure is the rear piston bearing it's because of the bearing washing out. This happens with extreme flooding or oil lube failure.
    What was interesting is what I mentioned that engineers won't always agree on the failure mode. That got me interested in opening the end bell on semi's to try to understand the failure.

    One of the most interesting was a 25 ton (me thinks) carrier. the end bell was removed and it was a phase failure. Problem there was phase protection along with overloads.
    This failure was caused by the compressor being fed from a sub panel. Tracing the feeders I located the main feed panel and found a loose lug that, over time burned the winding. It probably took a long time for the protection to not respond.

    Carrier encouraged all semi-hermetic compressors to be opened and attempt to analyzed. They knew almost all failures except maybe really old ones were external to the compressor. Also if the problem isn't found a replacement will also probably fail.

    Early on I once was sent to a job where they were replacing the second failure within a short time. Instead of replacing the compressor I pulled the heads on the failed comp and found the cylinders full of oil. Full. I knew the problem was external. It reinforced the importance of trying to discover the cause.
    Give me a relay with big enough contacts, and I'll run the world!

    You can be anything you want......As long as you don't suck at it.

    If a person wants to create a machine that will be more likely to fail...Make it complicated.

    USAF 98 Bomb Wing 1960-66 SMW Lu49

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •