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Thread: chiller help

  1. #1
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    Mar 2009
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    Norhern WI
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    chiller help

    I am working on a York liquid screw chiller, oil pump and oil filter were both replaced prior to my arrival.
    Unit shuts off on low discharge pressre. I measure a 4.5bar restriction (somewhere in the compressor). please help,

  2. #2
    Join Date
    Jan 2005
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    Houston TX
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    As always

    In order for anybody to help you, you also need to help us. We need some 411. Some history as in why was the oil pump and filter changed. Air cooled, water cooled.-GEO

  3. #3
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    Mar 2009
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    Norhern WI
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    ok i will try my best, I am still new at this.
    Costumer call was unit was tripping on low discharge pressure.
    They ( the costumers refer tech) changed oil filter and found a substantial amount of metal shavings.
    The unit is a York liquid screw unit with Appr. 750 hours. (Marine application)
    Myself and the York tech rep have been working on this for the last 2 days, we checked the oil pressure in the oil return line in a few different spots. We found a restriction in the new filter and replaced the filter again. When we run the unit we are starting in manually with the TXV at 15%. The slide valve is at its lowest setting which is 10%.
    When we bring the unit on it has low suction pressure which is normal for the start up time. It then drops to very low suction pressure, into negative. The unit still has a oil pressure drop of about 4-5bar. I cant find where the restriction is, it almost seems like it is in the compressor.
    Please help

  4. #4
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    Dec 2008
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    Dixiana, AL
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    What's the model number of this machine and compressor? And if at all possible, give your readings in psi - the vast majority of folks on this site don't correlate well to the metric measurements. Post ALL of your operational readings, otherwise, the very best you can expect is a wild guess. I've personally never seen a York machine trip on low discharge pressure (low discharge superheat, yes). But if it is tripping on low discharge pressure, and the suction is going into negative numbers, has anyone checked the charge level in the machine? What does a low discharge pressure trip have to do with an oil pump and oil filter being changed, unless someone lost all the freon when they changed the oil pump? You say the customer called with the LDP trip - are you sure that's what it tripped on? What are the oil pressures? Is it tripping or alarming on oil pressure? If you're tripping on low discharge pressure, why are you fooling with the oil filter and not finding out why you have low discharge pressure? You say you are new at this. Are you new at posting, are you an apprentice, or are you new to this level of equipment?

    I'm not trying to be difficult, but if you look objectively at your posts, I believe you can see where you can help yourself by helping us to understand your situation. It would also be nice, if you want advice on industrial refrigeration equipment, if you would be so kind as to tell us a little about yourself in your profile. This depth of questioning is usually done after someone has applied for and gained pro membership, and everyone knows a little about you.

  5. #5
    Join Date
    Mar 2009
    Location
    Norhern WI
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    Klove,
    Sorry about that. I will update my profile.
    I am just getting alittle discouraged with this call, I have been stuck on this ship for the last week, The York tech I am working with is very hard to communicate with, being from another country. I will be onboard today and will take all readings necessary, if your still willing to help me?
    Thanks, and sorry.

  6. #6
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    Dec 2002
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    SouthEast NC ICW & Piedmont Foothills
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    any idea where those metal shavings came from?

    how long since filter & pump were last replaced?
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  7. #7
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    Klove just looking thru IOM's they are most likely working on a S7 style screw compressor which does have a oil pump on it.
    Arguing with your Boss is like wrestling with a pig in
    mud.
    After a while you realize that while you are getting
    dirty, the pig is actually enjoying it.

    It is not exactly cheating, I prefer to consider it
    creative problem solving.

    25 years ago we had Bob Hope , Steve Jobs , and Johnny Cash today we have no Hope no Jobs and no Cash !
    I can fix broke but i can't fix stupid !

  8. #8
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    Mar 2009
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    Norhern WI
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    No, at this point I have no idea were the metal shavings came from, the shavings are very black and fine, like sand. The York tech thinks they are left over from the manufacturing state.
    The oil pump was replaced about 4 weeks ago, the unit would still not run with the new oil pump, at that time the oil filer was replaced with a used filter out of another machine, this was done by a different York tech prior to my arrival.
    Yesterday we replaced the oil filter with a brand new filter, found more shavings on the magnet at that time.
    I am not sure were the York tech is getting his measurments for the oil pressure drop, the only problem I notice is the suction going to low and tripping.
    Yesterday when we added more refrigerant we maintained the unit running for a longer period until the York tech tried adjusting the Txv, Then it shut down on low suction.
    Today I will take all readings.
    The York tech mentioned yesterday that it may be something internal to the compressor.
    When we did start the unit yesterday the oil temp in the oil return line next to the comp had reached 105F.
    I compared a unit in operation yesterday, the readings on that unit are LOW SUCTION PRESS=20PSI DISCHARGE PRESS=76PSI
    OIL PRESS=102 SUCTION TEMP= 55F
    These units (in the tech manual) state that the oil differential across the filter can be up to 1bar (14.5PSI)
    Yesterday it seemed to operate longer and sounded good after adding more refrigerant.

  9. #9
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    Quote Originally Posted by york56 View Post
    Klove just looking thru IOM's they are most likely working on a S7 style screw compressor which does have a oil pump on it.
    S7's and the majority of Fricks have oil pumps, I believe some S5's were so equipped.

    Very willing to help T, just have to know what we're trying to help with. Which problem are we chasing first - low suction or lube system? Or low discharge? As with all problems, they're based on physics and logic, neither of which will lie to you. But especially if there are mustiple issues on one machine, they will hide and laugh at you. We have to deal with things in a somewhat orderly fashion, but the question was about low refgt pressures and all that was given any info on was shavings in the oil filter. Lets get it running first, and then we can deal with the minor details.

  10. #10
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    Mar 2009
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    Norhern WI
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    Klove,
    The unit is a Saab vsm89(sabroe?) is how the york tech pronounced it.
    I had a chance to talk with the york tech today, What he is saying is - The unit does not have sufficient oil pressure to push the oil past the oil filter. As it goes into pull down the oil pressure drops along with the suction pressure.
    His thought are that the oil is leaking somewhere within the compressor and there for is taking the path of least resistance, and does not have enough pressure to push it through the oil filter. The unit then trips on low oil pressure.
    I sure hope this helps as I said before I am very new to these types of systems.

  11. #11
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    Sabroe is a Danish-built refrigeration system. I don't have any literature at all on these units, because they don't sell them in the states, to the best of my knowledge. Frick was the mfr of our industrial refrigeration systems.

    That being said, we still have the general mechanics of a typical system to fall back on, so let's try and get pointed in the right direction: We still need the particulars of the system - what are you cooling (brine or dx air to refgt), what refgt are you using, what are your design temps (condensor and evap, if water cooled)? Could be that negative numbers on the suction are fine, depending on the application and the refrigerant. What are the particulars of the problem that you are seeing??? At the risk of sounding like a horses butt, I really don't care what the York tech thinks unless it can be backed up with something substantial - we have to have some hard numbers to get going, especially if it's an odd issue that may be a one-of-a-kind problem. Going with what someone else thinks won't get you anywhere if they haven't come up with an answer. For example : according to your statement of what he said, there is unfiltered oil going into the compressor. Is that the case? How do the lube lines run on this unit? What's the actual pressure drop across the filter? Is it a Frick (or anybody else's) compressor, and if so, what model? Does it use full time auxiliary lube pump, or use the oil pump for startup only? If this is a true industrial refrigeration system, then it looks like an explosion at a pipe factory, and if myself, or anyone else is going to have a chance of helping you make this thing do what it's supposed to to do, then we have to know what it's supposed to do - guessing is a waste of time.

    I/we can't do anything but speculate without something to go on. The problem you describe could lead us down a thousand miles of bad road making assumptions and saying "look at this" or "look at that". You may be new to these systems, but at least on this one, sounds like you're up to your eyeballs in it. Help us to help you.
    Last edited by klove; 10-25-2009 at 04:12 PM. Reason: country of origin was wrong on sabroe

  12. #12
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    I used to look after a sabroe system a few years ago it was kind of cool. The whole unit was designed to be run in a shipping container. Came with the tower inside and just had to pull it out and put it on the roof of the container. I saw that diagnostic once turned out to be a bad txv on the liquid injection cooling lines cooling lines basically dumping liquid. It would overfeed and trip us out on low discharge temperature. Changed it out and all was well. If I recall and its been a while those lines are supposed to feed at 75 degrees. give or take

  13. #13
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    http://www.sabroe.com/products/screw-compressors.html
    See if it looks like anything on here quite a few different styles to choose from. See if visual association will help out.
    Arguing with your Boss is like wrestling with a pig in
    mud.
    After a while you realize that while you are getting
    dirty, the pig is actually enjoying it.

    It is not exactly cheating, I prefer to consider it
    creative problem solving.

    25 years ago we had Bob Hope , Steve Jobs , and Johnny Cash today we have no Hope no Jobs and no Cash !
    I can fix broke but i can't fix stupid !

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