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  1. #1
    Join Date
    Jan 2012
    Location
    Pakistan
    Posts
    20

    York Chiller (YT) Coupling Damage

    We’ve a York Centrifugal Chiller installed at our site with the following specs
    Series YT Codepak
    Unit Model YTH3J3E35COG
    Refrigerant R123
    Capacity 500 Tons
    Compressor Model YDTL.126
    Starter SSS 26L-50A

    There was a leak in the purge system and we recently had the refrigerant refilled. The chiller was out of service for a good 2 months or so. Before the leak, the chiller was running perfectly fine. After the refill, ‘High Line Voltage’ indication started coming, all the voltages were checked and were found to be within acceptable ranges.

    During the course of troubleshoot, Trigger Board (031-00925-003) was changed, then the logic card (031-00936-004) and finally the Micro Board (031-01065-001). After replacement of Micro Board, the indication disappeared and York Chiller was turned on. It completed its start sequence properly but after approximately five minutes of running, “Coast Shutdown” indication appeared meaning the York Chiller is shutting down, while the chiller was still running. Chiller was not accepting any command; therefore it was turned off from the circuit breaker. After checking all the jumpers on the micro card the breaker was switched on again and the motor started without any start command effectively bypassing the soft starter. The breaker was immediately turned off. The SCRs were checked and were found shorted. (Three shorted, one on each phase).

    All six SCRs and the Trigger Board (031-00925-003) were replaced. The circuit breaker was switched on; this time around the motor didn’t start automatically without the command. The start command was given and after the sequence initiation it the chiller started and tripped immediately. Our supply scheme is such that the chiller is supplied to by a 400V 3Ph feeder which in turn is supplied to by an 11kV distribution grid. When the chiller tripped, the 11kV circuit breaker tripped as well clearly indicating that a significant amount of inrush current went through (we didn’t have any measurement on the current available at that point). For reference, the normal startup current of this motor is around 2400 Amperes and the FLA is 515 Amperes. When we inspected the SCR’s, two of them on a particular phase were found to be shorted.

    The faulty SCR’s were replaced, motor was meggered and was found ok. Furthermore, the motor was decoupled from the compressor and tested and was found to be working perfectly fine.

    During the decouple we found that the coupling on the compressor side had been damaged with the four of the six bolts completely sheared off. When the compressor was checked, it was found to be rotating perfectly fine (with hands).

    The coupling was replaced and the chiller was started again with absolutely no problems.

    My question here is that what could have possibly caused the coupling damage and bolt shearing since the compressor and the motor are perfectly fine?

    I’ll be posting the pictures of the damaged coupling.

  2. #2
    Join Date
    Mar 2010
    Location
    Morgan Hill Ca.
    Posts
    1,171
    We can't really answer any technical questions such as this in an open forum according to the rules.

    However I must say that this is one of the best write ups I have ever seen on this site.

    My suspicion would be that the coupling was installed incorrectly with insufficient torque values, it is all speculation but based on what you describe, it sounds like an issue that may have been exacerbated by the starter problems.

    Another thing to check would be the motor alignment.

    I have been told that these do not need to be aligned, but I call BS. Had to align several YT's over the years.

    GT
    If a day goes by and you have learned nothing, I hope you got a lot of sleep.

  3. #3
    Join Date
    Jan 2012
    Location
    Pakistan
    Posts
    20
    So where can I post this question?

    As far as the alignment goes, it was working perfectly fine since from the last time the motor was decoupled for an overhaul (around a year and a half ago).


    Quote Originally Posted by GT Jets View Post
    We can't really answer any technical questions such as this in an open forum according to the rules.

    However I must say that this is one of the best write ups I have ever seen on this site.

    My suspicion would be that the coupling was installed incorrectly with insufficient torque values, it is all speculation but based on what you describe, it sounds like an issue that may have been exacerbated by the starter problems.

    Another thing to check would be the motor alignment.

    I have been told that these do not need to be aligned, but I call BS. Had to align several YT's over the years.

    GT

  4. #4
    Join Date
    Mar 2010
    Location
    Morgan Hill Ca.
    Posts
    1,171
    Quote Originally Posted by snsici View Post
    So where can I post this question?

    As far as the alignment goes, it was working perfectly fine since from the last time the motor was decoupled for an overhaul (around a year and a half ago).
    If you want to get more in depth, I would recommend applying for Pro status, this would allow you to basically converse tech to tech in the "locked" areas.

    Do you know if any vibration readings have been taken? If so, what was the axial magnitude?

    Are you seeing any sign of looseness with a high vertical? Also, this may sound ridiculous, but is the machine level?

    I have had instances when the shaft seal was repaired and the tech forgot to torque the coupling bolts properly and it broke two bolts... Four is downright scary, that coupler was getting ready to come visit you.

    Keep the guards on is all I have to say..

    GT
    If a day goes by and you have learned nothing, I hope you got a lot of sleep.

  5. #5
    Join Date
    Jan 2012
    Location
    Pakistan
    Posts
    20
    I'll see if i can get the vibration readings.

    Is it possible that this can happen solely due to the starter? (soft starter was rendered faulty and it ran without the 'soft' start during this episode)


    Quote Originally Posted by GT Jets View Post
    If you want to get more in depth, I would recommend applying for Pro status, this would allow you to basically converse tech to tech in the "locked" areas.

    Do you know if any vibration readings have been taken? If so, what was the axial magnitude?

    Are you seeing any sign of looseness with a high vertical? Also, this may sound ridiculous, but is the machine level?

    I have had instances when the shaft seal was repaired and the tech forgot to torque the coupling bolts properly and it broke two bolts... Four is downright scary, that coupler was getting ready to come visit you.

    Keep the guards on is all I have to say..

    GT

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