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  1. #1
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    SAB 128 rotatune shaft seal leak



    Hi, dear friends,

    want to hear your opinion .... experience ... suggestion ....

    Last year we made general overhaul on SAB 128 rotatune (high stage chiller) now after 5000 working hours client asked for service, because the shaft seal was leaking too much... no smell of ammonia only oil is coming out...

    We opened it and checked, but find no sign of wear or damage, all was clean and nice.

    What to do? ... Check and clean all parts and install again the old carbon part on shaft, but with new steel part inside of cover. After a few days oil leaking was bigger then reduced and now again start at the rate of 0,080-0,090 l/day what is about 0,5-0,6 l/week or about 2-2,5 l/month.

    What to do? Please, do not tell me to install a bigger plastic bottle for leaking oil ... instead of this one

    Seems it is a big amount of leaking oil, but we do not have a good explanation why and what is the best to do ... We are in doubt ... we installed a complete new shaft seal during general overhaul... to install again a new shaft seal is not cheap, but the worst will be if we have a leaking again after 4000-5000 hours like now

    Thanks for your input...

    Best regards, Josip



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  2. #2
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    Re: SAB 128 rotatune shaft seal leak

    I have changed these on the 163 and have to admit, the last one I did.

    The only issue I could find was degradation of the O Ring. There is a drip rate allowed by most manufacturers.
    I will see if I can find the Sabroe one for you.

    Grizzly

  3. #3
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    Re: SAB 128 rotatune shaft seal leak

    Back again my friend.
    I have extracted the following from a Sabroe service manual.

    Shaft seal leakage Leakage exceeds normal allowable
    rate of 7 drops per minute.
    Replace seal.

    Grizzly

  4. #4
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    Re: SAB 128 rotatune shaft seal leak

    Josip,
    From my experience I can offer the following if '0' rings & seal faces look good.

    1/ Coupling alignment

    2/ Shaft seal area damaged

    3/ Welded metal bellows damaged This can be checked by seal repair company by pressure test
    of bellows. This has happened to me on new seals where a pin hole has appeared, on weld, on bellows
    or carbon insert.

    4/ Enough seal tension or seal working lenth. Have had it happen where bellows is to short.
    Usually 3-4 mm crush on bellows (in assembly instructions).

    5/ Anti vibration dampers touching shaft causing shaft damage.
    This happened on new 202 seal where bellows was not running true.
    You can put in lathe to check, also tell tale marks on shaft


    I'd suggest another new seal checking most of above.

  5. #5
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    Re: SAB 128 rotatune shaft seal leak

    Josip,
    Also add anti rotation pin on stationary face not set at correct lenth.

    High spots where stationary seat, seat against seal cover.
    Could have been knocked during removal of old seat.
    High spots on seal cover face/ compressor housing.

    Do you have old shaft seal, maybe it could be reconditioned if it makes it more economical,
    if you have to replace.
    Last edited by RANGER1; 27-02-2012 at 09:22 AM.

  6. #6
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    Re: SAB 128 rotatune shaft seal leak

    Josip, change the "O" rings, though still a problem bellows.

  7. #7
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    Re: SAB 128 rotatune shaft seal leak

    Josip.
    As per RANGER 1, I have had several problems with o/rings in shaft seals lately. Most stemming from low grade motor bearings fitted by other contractors

  8. #8
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    Re: SAB 128 rotatune shaft seal leak

    Josip,
    Have you come up with anything yet or still working on it?

    Hopefully we have come up with something to help solve problem.

  9. #9
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    Re: SAB 128 rotatune shaft seal leak

    Hello Josip,

    when using rotatune, it is recommended to use a temperature controlled valve in the main oil injection line.
    The discharge temperature often gets too cold in low frequency (same amount of injected oil as in high speed!!!), causing too much liquid in your oil system, causing shaft seal failures.

    Regards, Gerben

  10. #10
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    Re: SAB 128 rotatune shaft seal leak

    Hi Gerbin.
    All the guys on this post are well experienced with Sabroe equipment, myself included.
    I am wondering what exactly your post means?
    If you are saying there is a specific size orifice plate fitted, dependant upon the refrigerant being used.
    Or that the Amot Valve which is the temperature control valve within the oil cooling system.

    Then I agree!

    However your discharge temperature is directly influenced by your Condenser control settings.
    Not to mention the many various Unisab settings that monitor oil temp / press etc.
    However your may be a hybrid and not a straight forward Sabroe pack.
    I would be very surprised if Josip had anything like the scenario you suggest.
    Grizzly

  11. #11
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    Re: SAB 128 rotatune shaft seal leak

    Hi Grizzly,

    our experience is a shrimps vessel with 2 off Howden WRV204 packs, which we speed up to 4500 rpm. It turned out that the discharge temps were too low in low speed. This is caused by the amount of oil injected through the main oil line. In high speed you will need more injected oil to cool your discharge gas, in low speed you will need less. We thewn build some temp controlled (discharge temp) valves in the main oil injection line to keep the discharge temp on a stabile 78 C and shaft seals are okay.
    When the discharge temp gets too low lets say below 65 C, you slowly collect too much liquid in your oil bath, and liquid ammonia will slowly dry out your shaft seals. Even with good oil pressures and oil temperatures this happens. It is called blistering.

    http://rm-support.com/expert-advice/...aft-seals.html

    Regards Gerben

  12. #12
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    Re: SAB 128 rotatune shaft seal leak

    Thanks for the info Gerben.
    Next time I have an issue with a Howden, maybe you will be able to help?
    Grizzly

  13. #13
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    Re: SAB 128 rotatune shaft seal leak

    Howden have another new shaft seal design with different "0" rings.
    Hopefully when you look sideways at them they won't leak!

    Josip only mentions problem after rebuild, so assume it was OK before!

  14. #14
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    Re: SAB 128 rotatune shaft seal leak

    Hi, dear friends

    thanks for all inputs .... always learn something new what is good for all of us ..

    at the moment we are not doing anything regarding oil leak, still waiting to see if this is going to develop in more serious oil leak or will remain like now, what we can bear no smell of ammonia yet... and 2 liters of lost oil per month is acceptable ... I prefer to not have oil leak, but sometimes we are not able to improve anything and accept the things as they are ...

    This is standard Sabore unit with Amot 3-way oil temperature control valve and compressor was OK till 40000 hours ... no money to overhaul on time but with some higher shaft seal (original shaft seal) oil leak ... nothing serious ... so we overhauled it with 45000+ hours (last year in March and all compressor internal parts w in a very good condition) and now after almost one year of continuous running happened this ...

    That unit is running almost all the time (6500+ hours per year) and there is hard to have a cold oil within unit, but still it is possible to get some more ammonia drops (unit is working in brewery as chiller) when they start to cool down a very warm beer ... we did not notice something like that, but we are not present all the time there and sometimes operators are prone to use some "shortcuts" to do the job...

    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

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