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  1. #1
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    Sab 128 Problems



    Hello, I have a Sabroe 128 MK2. The suctiongas temperature is too high and the amp is too low. It should use about 180 amp, it uses 135-150. The suctiongas temperature is +10-20. The rest of the values seems OK. Has anyone in here seen something similar? I find nothing wrong with the mecanics. I dismantled it and put it together again, and the first time I started it, it worked OK. Then I stopped it and startet it again, and the problems came back.



  2. #2
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    Re: Sab 128 Problems

    Hi
    put it in manual position
    than push up load see what happen
    if you capacity goes up and AMPS move to high
    you check your setting
    if not
    check suction filter and all valves

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    Re: Sab 128 Problems

    Marthe,
    Suction, discharge, oil pressures, refrigerant etc would be helpful.
    Are pressures normal/ abnormal?
    These types of compressors have hydraulically driven suction check valves, so oil pressure & filter condition important.
    Also slide valve indication may be out of calibration, as MBC mentions, can you force it to load more?
    Is something inhibiting it from loading like motor amps or pressure, check settings.

    Check if your readings are correct for transmitters as bad power supply can upset readings as well.

    http://www.cooltech.ru/en/spares/sabroe/spiral/sab128
    Last edited by RANGER1; 07-11-2017 at 08:28 AM.

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    Re: Sab 128 Problems

    I have checked the suction filter. It was OK. I also tried to put it in manual position. When I pushed upload, the capasity went up to 100 %. But the amps did not rise. And the suctiongas temperature did not go down. Every other values were OK, such as oilpressure, oiltemp, suctionpressure etc. It seems like the compressor shows 100 % capasity, but only runs in 10-20% capasity. The slide calibration is also OK. I think there might be someting wrong with the slide, showing 100 %, when it maybe is 10-20%, I don`t know.

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    Re: Sab 128 Problems

    marthe,
    Do you have manual or auto Vi, if auto is it working.
    You think slide is 100% but can you energise load solenoid or use magnet to see if it can do anymore work?
    Is POV bypassing (discharge to suction), as maybe could feel of hear it.

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    Re: Sab 128 Problems

    Hi
    if don't have manual of that inform me I will send it to you .
    Last edited by mbc; 08-11-2017 at 06:32 PM.

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    Re: Sab 128 Problems

    I have manual Vi. But there is a set screw in the end of the regulator. I try to find the correct lenght of that.

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    Re: Sab 128 Problems

    Hi
    there is two REG valves
    one for loading
    2nd for unloading
    close unload one then when compressor is running inergyzed solinod of load by hand very jentilly
    and measure AMP. and load

  9. #9
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    Re: Sab 128 Problems

    Quote Originally Posted by marthe1994 View Post
    I have manual Vi. But there is a set screw in the end of the regulator. I try to find the correct lenght of that.
    If adjustment changed slide valve will have to be recalibrated as it changes travel.

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    Re: Sab 128 Problems

    The sab128 has a manual Vi if I remember correctly (don't take my word for it) so I would leave that alone unless the compressor has been recently refurbished.

    is it controlled by a Unisab controller?

    if so it might show 100% capacity when it's not really in full mechanical slide capacity.

    The unisab controller while it is good, may figure out that the compressor is in 100% capacity, based on the suction pressure, discharge pressure and amps and will show 100% in the display, but the slide might only be at 30% load...

    The unloading solenoid is normally open, meaning it should be energized as long as the compressor is running and click off when it gets a decrease pulse.
    the increase solenoid is normally closed, so that one should be energized only when the compressor is getting an increase signal.

    Watch in the unisab display if there is an up or down arrow blinking next to the capacity % in the unisab display, if it's showing 100% and there is an arrow pointing up blinking next to it, it means that the Unisab controller is asking for more capacity, every time the up arrow blinks, the increase solenoid will be activated.

    if the display shows 100% in the bottom right and there is no up or down arrow blinking, the unisab is saying that the compressor is now at it's max efficiency.

    I'm guessing that the compressor is also fitted with a standard Sabroe capacity indicator like this:
    lot-2-sabroe-3448-004-capacity-indicator-johnson-controls-new-h3-2107-c9a4c03054bae46eff89c8bd52.jpg
    and if you think it is calibrated... you may be wrong

    First of, the text has to be level, then you have to do like MBC said, on either side of the increase and decrease solenoids, there are reg valves, close the reg valve on the decrease side and then disconnect the solenoid on the increase side and use a permanent magnet/service solenoid on the increase side to find the true 100% position. this should be done on an already cooled down plant
    Then adjust the 100% (max point) using the screw on the front of the capacity indicator.

    Because even when you run in manual on the unisab is working in the background and may reduce capacity while you are pushing increase
    -Cheers-

    Tycho

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    Re: Sab 128 Problems

    Quote Originally Posted by Tycho View Post
    The sab128 has a manual Vi if I remember correctly (don't take my word for it) so I would leave that alone unless the compressor has been recently refurbished.

    is it controlled by a Unisab controller?

    if so it might show 100% capacity when it's not really in full mechanical slide capacity.

    The unisab controller while it is good, may figure out that the compressor is in 100% capacity, based on the suction pressure, discharge pressure and amps and will show 100% in the display, but the slide might only be at 30% load...

    The unloading solenoid is normally open, meaning it should be energized as long as the compressor is running and click off when it gets a decrease pulse.
    the increase solenoid is normally closed, so that one should be energized only when the compressor is getting an increase signal.

    Watch in the unisab display if there is an up or down arrow blinking next to the capacity % in the unisab display, if it's showing 100% and there is an arrow pointing up blinking next to it, it means that the Unisab controller is asking for more capacity, every time the up arrow blinks, the increase solenoid will be activated.

    if the display shows 100% in the bottom right and there is no up or down arrow blinking, the unisab is saying that the compressor is now at it's max efficiency.

    I'm guessing that the compressor is also fitted with a standard Sabroe capacity indicator like this:
    lot-2-sabroe-3448-004-capacity-indicator-johnson-controls-new-h3-2107-c9a4c03054bae46eff89c8bd52.jpg
    and if you think it is calibrated... you may be wrong

    First of, the text has to be level, then you have to do like MBC said, on either side of the increase and decrease solenoids, there are reg valves, close the reg valve on the decrease side and then disconnect the solenoid on the increase side and use a permanent magnet/service solenoid on the increase side to find the true 100% position. this should be done on an already cooled down plant
    Then adjust the 100% (max point) using the screw on the front of the capacity indicator.

    Because even when you run in manual on the unisab is working in the background and may reduce capacity while you are pushing increase

    The capasity is calibrated. The compressor goes on 100% and everything seems ok. Then suddenly the amps go down from 170 to 140 and suctiongas temperature also rises, apparatently for no reason. It seems to loose capasity and compression. But both the Unisab and the clock show 100 % capasity. It sometimes work, sometimes not.
    Is it possible that the capasity is not calibrated when both the Unisab and the clock shows the same? The clock follows the slide mecanicaly, doesnt it?
    Last edited by marthe1994; 10-11-2017 at 01:24 PM.

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    Re: Sab 128 Problems

    Quote Originally Posted by marthe1994 View Post
    The capasity is calibrated. The compressor goes on 100% and everything seems ok. Then suddenly the amps go down from 170 to 140 and suctiongas temperature also rises, apparatently for no reason. It seems to loose capasity and compression. But both the Unisab and the clock show 100 % capasity. It sometimes work, sometimes not.
    Is it possible that the capasity is not calibrated when both the Unisab and the clock shows the same? The clock follows the slide mecanicaly, doesnt it?
    I have checked the slide, and then capasity, and I changed the capasity regulator valve with another sab 128 and that works fine. The online thing left in my mind is to check the oilcapasity and the screws. The oilpressure seems ok, but can there be a leakage in the screws? I dont know yet. How can I check?

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    Re: Sab 128 Problems

    Marthe,
    Do you have above pictured potentiometer, or the newer type linear position indicator?
    If potentiometer like pictured you can loosen 4 screws a bit & turn potentiometer complete with glass clockwise, this will alter reading on Unisab to lower than 100% & you could try to load it more.

    If you lock slide valve indicator in one spot, does it stay in same % or move by itself?
    If normally open solenoid is damaged it would creep to unload all the time or depending if solenoid seat damaged maybe some of the time.
    Make you sure it is calibrated, what have you done to prove it.
    Eliminate one thing at a time.

    I have a a problem with one at the moment & believe it is damaged magnet driving indicator like in picture.
    Have new one on order, hopefully fixes it as magnet slips, leaving indicator at full load , but is actually at full unload.
    But if it were your case, why would it unload if capacity is required unless it was the same
    as mine & you can't see it unload due to faulty magnets?
    Front cover if not assembled properly can also cause rubbing between glass & disc with slot in it to drive potentiometer.

    Also so check that it's not backing off on motor amps or high discharge pressure, as these override everything. Check settings & determine if ok.

    You also mention in your first post about dismantling mechanics, what did you do exactly.
    Last edited by RANGER1; 11-11-2017 at 07:52 AM.

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    Re: Sab 128 Problems

    Quote Originally Posted by marthe1994 View Post
    I have checked the slide, and then capasity, and I changed the capasity regulator valve with another sab 128 and that works fine. The online thing left in my mind is to check the oilcapasity and the screws. The oilpressure seems ok, but can there be a leakage in the screws? I dont know yet. How can I check?
    Mao do you still have a problem after changeling capacity valve?
    Amps usually tell you everything & if suddenly drop machine has either unloaded or POV opened.
    How long has it been in service, or when was it last overhauled as 30-40,000 hrs is recommended.

  15. #15
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    Re: Sab 128 Problems

    Quote Originally Posted by marthe1994 View Post
    The capasity is calibrated. The compressor goes on 100% and everything seems ok. Then suddenly the amps go down from 170 to 140 and suctiongas temperature also rises, apparatently for no reason. It seems to loose capasity and compression. But both the Unisab and the clock show 100 % capasity. It sometimes work, sometimes not.
    Is it possible that the capasity is not calibrated when both the Unisab and the clock shows the same? The clock follows the slide mecanicaly, doesnt it?
    Depending on what potentiometer you have it's a magnet on old type in picture supplied by Tycho.
    New type is linear position indicator, also magnet.

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    Re: Sab 128 Problems

    Quote Originally Posted by marthe1994 View Post
    The capasity is calibrated. The compressor goes on 100% and everything seems ok. Then suddenly the amps go down from 170 to 140 and suctiongas temperature also rises, apparatently for no reason. It seems to loose capasity and compression. But both the Unisab and the clock show 100 % capasity. It sometimes work, sometimes not.
    Is it possible that the capasity is not calibrated when both the Unisab and the clock shows the same? The clock follows the slide mecanicaly, doesnt it?
    Depending on what potentiometer you have it's a magnet on old type in picture supplied by Tycho.
    New type is linear position indicator, also magnet.

    http://www.hbproducts.dk/en/products...pacity-sensors

    http://www.hbproducts.dk/en/products...or-long-stroke

    http://www.hbproducts.dk/images/cert...ual-022-UK.pdf
    Last edited by RANGER1; 11-11-2017 at 08:19 AM.

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