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  1. #1
    Join Date
    Aug 2006
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    44

    Decoupling - EagleEye

    Hi guys, does anybody know about the decoupling system used in chilled water systems, and what is the EagleEye valve?

  2. #2
    Join Date
    Sep 2007
    Location
    Michigan
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    290
    Based off pipe size, and balancing, from my non-engineering, control guy mind. Unless your doing a temp reset for the secondary loop I'm not aware of any reason to have a valve. Typcially with chilled water there is a flow station to determine the load on the plant.
    "Yeah I can figure out whats wrong with it, but you were here first and there isn't room for two, plus it's cold up here, I'll be in the van"

  3. #3
    Join Date
    Apr 2007
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    16
    This system is used for large plants with multiple chillers. It consists of a primary chilled water loop with bypass and pumps a secondary loop with the multiple chillers in parallel. Each chiller has its own pump and can be valved into and out of the chiller loop based on the demand accross the primary loops bypass flow. If the flow is negative (low demand in the primary loop) chillers are subtracted from the system and vice versa. The issue of the eagle-eye valve is a new one for me, could this be the trade name? The valves on the system I have experience with are Rotork and we always call them this rather than the "chiller" valve??

  4. #4
    Join Date
    Aug 2006
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    44
    so for me as a control guy, how will i control the system? what is the sequence of operation for such system? attached you will see the drawing where it shows the the Decoupled system.


    Any clue??
    Attached Images Attached Images

  5. #5
    Join Date
    Apr 2007
    Posts
    16
    I'll take a look at the drawings and give this a think. If you can get a copy of Trane's chiller plant engineering document they have several control strategies for large plants built into their software. I don't know what control company you're using but this may give you some good ideas. Just at first glance I'm thinking the eagle eye setup is for detecting flow direction??

  6. #6
    Join Date
    May 2006
    Posts
    348
    Looks like flow meter to indicate how much water is being used by the system vs how much is being bypassed back to the chiller(s) unused.

  7. #7
    Join Date
    Apr 2007
    Posts
    16
    Yep. Made by Rosemount, found it on their site, it's there for exactly that function. I'm going to assume that the secondary loop is monitored, normally a diff pressure xducer and the secondary pumps will have variable speed drives. As the secondary loop flow demand drops the back flow through the decoupling loop to the chillers will indicate that chillers can be subtracted from the primary loop. The flow values time delays etc. to add or subtract the chillers will depend on the dynamics of the chilled water system. I didn't take a close look at the flow sensor but as a note it will be required to measure forward and reverse flow. The terms primary and secondary loop seem to vary job to job, I will clarify here the secondary loop is the one going out to the facility and the primary has the chillers.

  8. #8
    Join Date
    Sep 2007
    Location
    Michigan
    Posts
    290
    Quote Originally Posted by dsirdah View Post
    so for me as a control guy, how will i control the system? what is the sequence of operation for such system? attached you will see the drawing where it shows the the Decoupled system.


    Any clue??
    A bit... over your head? Engineer didn't provide a sequence? If you have the sensor to know your GPM flow yoy can use % to stage the chillers since you know the rated GPM of each chiller. It's been awhile, don't quote me. As someone else said, bring on more secondary pumps as the DP can't make set point and VFDs are maxed. You have 10 chillers? I see 10 primary pumps. Sounds like an awful big job to be designing from scratch, if these are big secondary pumps they may not want to run two pumps at 100 when its more efficient to run 3 are 60. Same as chillers, there is an awful lot of questions I'd be asking to someone with some letters after their name.
    "Yeah I can figure out whats wrong with it, but you were here first and there isn't room for two, plus it's cold up here, I'll be in the van"

  9. #9
    Join Date
    Jun 2007
    Location
    Sydney, Australia
    Posts
    39

    Red face Decoupled Systems

    The following Trane engineers newsletter gives a good overview of decoupled systems:

    http://www.trane.com/commercial/libr...8_2/en18_2.pdf

    The Eagle-eye is a flow sensor and needs to be able to provide both flow and direction as the direction will tell you whether the operating chillers are meeting the load.

    In my experience decoulped systems work excellently for large distributed systems (shopping centres, casinos, large office buildings) as long as the decoupler line is long enough, straight enough and well positioned enough to provide a good decoupling effect. Unfortunately mechanical contractors can take what looks great in a schematic and turn it into a nightmare by not properly considering the effect of poor pipework design.

    Cheers

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