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  1. #1
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    Screw compressor resonance/vibration in discharge



    Long time reader, first time caller

    My company did a DX plant upgrade (A/C) and have installed a 134a bitzer screw (around 300kw capacity) which was sized and designed by a separate engineer. The discharge pipework has a very loud internal resonance coming from 2 spots (*): brief pipe rundown

    Rises from compressor then horizontal 2m
    *a straight that drops and climbs with two 45 degree bends with 1m in between elbows
    5m then right bend then 15m
    *a left hand bend, runs 1m drops vertical 0.5m then straightens horizontal (loudest)
    Then outside to condenser

    The unit is still slightly undercharged going off vessel on pump down (DX so unsure of full), the discharge pipe work is 2" 1/8, no mufflers/eliminators

    Addition of gas towards 'full' has helped and reduced pulsations a little
    All fixings are tight but not really relevant given the nature of the noise
    Pressures run around 780-800kpa (pressure controlled) and 210 kpa

    Neither myself or my supervisor have had much experience with this issue, can anyone provide insight into what's causing the noise? And/or a solution?



  2. #2
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    Re: Screw compressor resonance/vibration in discharge

    better post a picture of the pipe work of discharge line

  3. #3
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    Re: Screw compressor resonance/vibration in discharge

    is it when the compressor stops or during running?

  4. #4
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    Re: Screw compressor resonance/vibration in discharge

    Pulsing within the discharge line can be a result of the system being undercharged particularly when you have no liquid seal within the receiver.
    Check the temp of the liquid line?

    Screws also have a natural resonance at certain running conditions.
    Sadly you may have to call in someone if you feel its a issue.
    Sorry to be vague.
    Grizzly

  5. #5
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    Re: Screw compressor resonance/vibration in discharge

    Thanks for the quick responses guys.

    I'll get a picture when I go back next, maybe even a video of the noise.

    During normal running

    I'm assuming the receiver would have a pickup at the bottom on the outlet but looking at it makes me think it's just on the side, but sight glass is always full now, it was a little short on liquid before, receiver has 3 sight glasses and all were empty but bottom one stays full now after addition of gas. Haven't got a number for the liquid line only feel which was deemed okay.

    Were going to talk to the guy who designed it because ultimately if he designs them he should have come across this before

  6. #6
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    Re: Screw compressor resonance/vibration in discharge

    Quote Originally Posted by Rexy View Post
    Long time reader, first time caller

    My company did a DX plant upgrade (A/C) and have installed a 134a bitzer screw (around 300kw capacity) which was sized and designed by a separate engineer. The discharge pipework has a very loud internal resonance coming from 2 spots (*): brief pipe rundown

    Rises from compressor then horizontal 2m
    *a straight that drops and climbs with two 45 degree bends with 1m in between elbows
    5m then right bend then 15m
    *a left hand bend, runs 1m drops vertical 0.5m then straightens horizontal (loudest)
    Then outside to condenser

    The unit is still slightly undercharged going off vessel on pump down (DX so unsure of full), the discharge pipe work is 2" 1/8, no mufflers/eliminators

    Addition of gas towards 'full' has helped and reduced pulsations a little
    All fixings are tight but not really relevant given the nature of the noise
    Pressures run around 780-800kpa (pressure controlled) and 210 kpa

    Neither myself or my supervisor have had much experience with this issue, can anyone provide insight into what's causing the noise? And/or a solution?
    There has to be an oil seperator in there somewhere as well!

  7. #7
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    Re: Screw compressor resonance/vibration in discharge

    Nope no seperator, it's a drop in compressor unit so I guess whoever designed it decided it dosent need it.

    image.jpgimage.jpgimage.jpg

    Pictures go from outside back to plantroom

    We're going with a discharge muffler either on the rise out of the compressor or on the first horizontal
    The systems designer couldn't confirm if it'll fix it or not but we don't have many options
    Last edited by Rexy; 15-10-2014 at 10:28 AM.

  8. #8
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    Re: Screw compressor resonance/vibration in discharge

    Would you have a picture of the package / compressor?

  9. #9
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    Re: Screw compressor resonance/vibration in discharge

    Attachment 11797
    Old and bad angle but all I have for the moment

  10. #10
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    Re: Screw compressor resonance/vibration in discharge

    And the discharge muffler has fixed it

  11. #11
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    Re: Screw compressor resonance/vibration in discharge

    Thanks, always good to know the outcome - cheers!

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