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  1. #1
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    Collapsed evaporator tubes - anyone seen this before??

    So I've been lurking for years, but this is my first post. Glad to be here, this is a great forum that is a wealth of information.

    I'm posting because I have an issue that I've never come across before in my 35 years in the business, nor has anyone I've talked to. I'll have to describe it as best as possible since I can't post a picture until I have at least 7 posts.

    I'm dealing with an air cooled scroll chiller with a shell and tube evaporator. I'll try to describe the history as best as possible:

    - received a call that it was not maintaining chilled water temp

    - sent a tech, found the unit low on gas (not flat), found multiple leaks on the Rotolocs.

    - pulled the charge, repaired the leaks, pulled vacuum, recharged. Did not have enough gas to top off the charge, was about 50# short (190 ton machine, 1 of 2 circuits affected).

    - went back the next day to top off, had water in the refer circuit. Chilled water circuit is 20% propylene.

    - figured it was unrelated and it possibly lost a tube (6 year old machine), scheduled an Eddy current test

    - Eddy test inconclusive, could not get the probe thru the return bends (2 pass circuit)

    - removed the discharge piping to look in the shell. This is where it got interesting. A pic would be worth a 1,000 words, IF I could post one...

    The piping on the return bends, past the end of the last tube sheet, was destroyed. The tubes on the outside of the bundle were crushed practically complete flat. Imagine laying a piece of copper on the pavement and running over it with a steamroller. The tubes towards the middle of the bundle were completely concaved. A cross section cut would look like a "C" instead of a "O". The tubes towards the center of the bundle were perfectly fine. All of the damage was in the bends, beyond the tube sheet. All of the straight pipe was fine.

    I have absolutely no idea what could cause this. The factory is blaming it on water hammer or water over pressurization, but I'm not buying it for a minute. Water hammer may damage the tubes, but not flatten them. I thought it might have been ice buildup from being undercharged, but that wouldn't crush the pipes flat either. I'm pretty much at a total loss as to what happened.

    Has anyone seen anything like this before?

  2. #2
    Join Date
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    No....but I would put my money on ice if we were betting.

    Sent from my SM-G965W using Tapatalk

  3. Likes captube liked this post
  4. #3
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    Get your post count up and load some pictures.

  5. #4
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    Aug 2006
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    Well, it ran fine for 6-ish years. So this happened recently. My money is also on a water issue but I wouldn’t know what issue. Logically, the water crushed the tubes when you pulled it into a vacuum. Maybe the water pressure was just above the maximum allowable water pressure? Have you tested the glycol concentration?
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

  6. #5
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    Thread Starter
    Quote Originally Posted by BALloyd View Post
    No....but I would put my money on ice if we were betting.
    If the ice was around the circumference, would it crush it flat or would it concave it? This situation has both.

  7. #6
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    Thread Starter
    Quote Originally Posted by VTP99 View Post
    Get your post count up and load some pictures.
    Trying...

  8. #7
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    Quote Originally Posted by jayguy View Post
    Well, it ran fine for 6-ish years. So this happened recently. My money is also on a water issue but I wouldn’t know what issue. Logically, the water crushed the tubes when you pulled it into a vacuum. Maybe the water pressure was just above the maximum allowable water pressure? Have you tested the glycol concentration?
    20% propylene

  9. #8
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    Sep 2019
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    Quote Originally Posted by jayguy View Post
    Well, it ran fine for 6-ish years. So this happened recently. My money is also on a water issue but I wouldn’t know what issue. Logically, the water crushed the tubes when you pulled it into a vacuum. Maybe the water pressure was just above the maximum allowable water pressure? Have you tested the glycol concentration?
    How much pressure, hypothetically, would it take to crush a copper pipe? I don't know the wall thickness...

  10. #9
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    Quote Originally Posted by jayguy View Post
    Well, it ran fine for 6-ish years. So this happened recently. My money is also on a water issue but I wouldn’t know what issue. Logically, the water crushed the tubes when you pulled it into a vacuum. Maybe the water pressure was just above the maximum allowable water pressure? Have you tested the glycol concentration?
    I understand the pipe's strength is exponentially more outward than inward, but I would think it would take a crazy amount of pressure to crush the pipe flat.

  11. #10
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    Sep 2019
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    Thread Starter
    Quote Originally Posted by jayguy View Post
    Well, it ran fine for 6-ish years. So this happened recently. My money is also on a water issue but I wouldn’t know what issue. Logically, the water crushed the tubes when you pulled it into a vacuum. Maybe the water pressure was just above the maximum allowable water pressure? Have you tested the glycol concentration?
    And why only at the return bends, not on the straight pipe?

    My 7th post... I'll try to post a picture.

  12. #11
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    Sep 2019
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    Quote Originally Posted by PAJoel View Post
    My 7th post... I'll try to post a picture.
    Guess I need one more...

  13. #12
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    Thread Starter

  14. #13
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    That looks like excessive vacuum and thin wall tubing.

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