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Thread: Hitachi screw/preventative rebuild

  1. #1
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    Hitachi screw/preventative rebuild

    I have a new customer with an air cooled machine on the roof running two Hitachi screws. In actuality they feed a dx air coil but I figured the chiller side was the best place for this one.

    The customer, a contract customer, wants to have a compressor sent off for a preemptive rebuild. It is required in the process of this factory and both compressors are needed for summer loads. The push is to get hours evaluated and get this pump sent out to be rebuilt like this week... and then back inside the machine before our first 70 deg day. I suppose the manufacturers recommendation will dictate whose buyin, this is a contract customer. I doubt the time table is achievable.

    But just to the general concept of rebuilding a screw as a preventative measure, I'm not exactly on board with that one. The engineer had a point when we walked around to a few of his other machines, those involved in the process. Everything had a rebuild recommendation based on hours right there in the manuals, moving parts wear out. I have never seen this done with a screw. Oil change and gaskets but nothing that requires the pump to be shipped off.

    My question then, any of you guys rebuild a screw just because it's hit a certain amount of runtime? I emailed the mfg but I kind of need a generic answer ASAP.
    Guinness for strength

  2. #2
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    Generally on a aircooled screw you should pull at least one of the compressers and inspec t it around 10,000 hrs. Reason because of unfavorable conditions. High head etc.

  3. #3
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    Run it to failure, and it will take a long time to fail.

  4. #4
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    Junk it. Replace with a Hanbell,

  5. #5
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    Quote Originally Posted by JEF1980 View Post
    Generally on a aircooled screw you should pull at least one of the compressers and inspec t it around 10,000 hrs...
    Where did this come from? Why would anyone do this? I have screws that have way over 50k hours without ever being inspected because they just work.

  6. #6
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    I don't remember the exact figures and it depends on the model of compressor................. the service replacement/overhaul period for Hitachi screws was 12,000 hours for standard bearings and 24,000(ish) hours for long life bearings on air cooled machines here in the uk. Yes you can run them for longer and I have seen them with 50,000 + hours. The issue was that a service exchange policy was available for rotors that were in tolerance, reducing the cost. Why the low run hours service interval ? That would be for Hitachi to answer !
    Replace it with a Hanbel !!!!!!!! Really ?!

  7. #7
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    I suppose that some manufacturers may have a recommended overhaul time frame, but 10-12k hours? I know of some chillers that are only shut down fr the annual cleaning and put on 363 days of run time. With over 16k hours every 2 years, you would be yanking the compressor every year!!! Not much of a selling point.

  8. #8
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    What is the selling point of a screw, they won't fail like a recip? yes that is true but all your system problems that were there with a recip are still there with the screw and it won't die right away but the problems will kill them. We just pulled out a well known screw with about 15,000 hours, pulled it apart and the thrust bearing came out in a couple of pieces, rotors were scrap metal. I dont belive there is a set number of hours, you need to go off of the conditions it runs in. All the manufacturers have hours listed in there books which are suggestions but they are definitly are not maintence free. Well some tell you they have a lifetime oil filter lol.

  9. #9
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    Are you taking oil samples every 6mo to a year and logging them? They will tell a good story on the machines insides.


  10. #10
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    Quote Originally Posted by JEF1980 View Post
    ... I dont belive there is a set number of hours, you need to go off of the conditions it runs in...
    My feelings exactly.

  11. #11
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    I have to admit those Hitachi screws can take a beating and ask for more . Ran into one that was running backwards and tripping on motor winding sensors . No one came back after install in dead of winter to start it up . Engineer swears that the screw ran for months yea right . No damage to the machine , no metal pieces . I can continue on with the story but don't want it to go to the wall of shame forum .

  12. #12
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    Quote Originally Posted by B_roche View Post
    My question then, any of you guys rebuild a screw just because it's hit a certain amount of runtime? I emailed the mfg but I kind of need a generic answer ASAP.
    Have you tried the ACCS Compressor the Hitachi rebuild out of MO? 417-859-6067. www.accscompressor.net I have used them before with good results. Usually can do a quick turn around like you need. Ask for Don.

  13. #13
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    I have know hitachi screws 6005sc-z and 500 series to run for decades, not that they dont need attention but that a hell of a good life span. ACCS is good people to work with parts or service

  14. #14
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    Makes no since to me to rebuild a screw ..
    no signature blast'em man blast'em
    !!!KILL THE TERRORIST!!!

  15. #15
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    Hitachi does list a rebuild recommendation based on hours of run time. Typical life is 2-4x longer to failure.

    The repair manual list around a dozen special tools and field rebuild is not practical.

    Most industrial screws are field rebuildable, commercial screws usually have limited field serviceability and recommended to be rebuilt in a qualified shop.

  16. #16
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    D/B had a horizontal teardown recommendation of 50,000 hours for many years. I don't know if they still do. I have seen them need serious re-work at 20,000 hours and I have seen them happy at 100,000 hours.

    If I had this customer I would suggest installing a new compressor to minimize downtime, have the take-out evaluated and a detailed inspection report generated, before rebuilding it. Then we could use it's pre-rebuild condition to evaluate the prudence of rebuilding their second compressor now or later. Either way the rebuild could be filled completely with oil and pressurized for storage. Leave a gauge in place and maintain a monthly log of the gauge pressure.

    PHM
    ---------


    Quote Originally Posted by B_roche View Post
    I have a new customer with an air cooled machine on the roof running two Hitachi screws. In actuality they feed a dx air coil but I figured the chiller side was the best place for this one.

    The customer, a contract customer, wants to have a compressor sent off for a preemptive rebuild. It is required in the process of this factory and both compressors are needed for summer loads. The push is to get hours evaluated and get this pump sent out to be rebuilt like this week... and then back inside the machine before our first 70 deg day. I suppose the manufacturers recommendation will dictate whose buyin, this is a contract customer. I doubt the time table is achievable.

    But just to the general concept of rebuilding a screw as a preventative measure, I'm not exactly on board with that one. The engineer had a point when we walked around to a few of his other machines, those involved in the process. Everything had a rebuild recommendation based on hours right there in the manuals, moving parts wear out. I have never seen this done with a screw. Oil change and gaskets but nothing that requires the pump to be shipped off.

    My question then, any of you guys rebuild a screw just because it's hit a certain amount of runtime? I emailed the mfg but I kind of need a generic answer ASAP.
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

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