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  1. #1
    Join Date
    Jul 2004
    Location
    Oklahoma City
    Posts
    18
    We have two 500 ton Absorber units in this facility, currently temperatures are cool outside (66 F*). We have been experiencing a 20 - 25 degree difference in Generator temperatures on the units. Our #2 unit consistantly is
    20 - 25 degrees higher than the #1 unit. Average generator temperature on the #1 unit is 240 to 250 degrees, where as the #2 unit constantly runs 260 - 270 degrees. The #2 unit on startup runs right up to the edge before a generator pressure alarm happens, we run the unit on half fire then ease it back to full fire after the unit hits it's set point on chilled water. Any ideas?

  2. #2
    Join Date
    Jun 2003
    Location
    in a tree looking in your window
    Posts
    1,165
    obviously direct fired, what brand? how old? besides running a lower generator temp how is the machine running? making setpoint, making margin?

    Dude
    If you dont stand behind our troops, please feel free...........to stand in front of them.

  3. #3
    Join Date
    Jul 2004
    Location
    Oklahoma City
    Posts
    18
    9 years old. Both machines making set point. Already adjusted #1 and #2 dampers. No change.....

  4. #4

    Hmm

    Hey General, are these lithum bromide units.Sounds like you need to check condenser water delta t. That should tell if you gotta punch some tubes. Whats your chill h20 supply temp? Gotta go...you might be in salting mode

  5. #5
    Sounds like a control problem.

  6. #6
    Join Date
    Jun 2003
    Location
    in a tree looking in your window
    Posts
    1,165
    Well without knowing what brand machine it is, and which micro the thing has, I would assume you have some kind of control that monitors crystalization margin. It probably has VFDs on the solution pumps and is either not pumping the proper amount of brine to the generator, or the burner is not set up right. I am a little lost as to why you would adjust the dampers to try and get the generator temps the same even though both chillers are making setpoint, is there something else odd with the machine?

    I have seen many times 2 identical machines that dont run exactly the same, thats just the way it is sometimes. You say #2 is consistently hotter than #1, has it been that way since startup?

    Dude
    If you dont stand behind our troops, please feel free...........to stand in front of them.

  7. #7
    Join Date
    Aug 2000
    Location
    USA
    Posts
    4,990
    What model? Whens the last time you had a solution analysis done? What where the results? Which inhibitor are you using? Is your solution black? Is it purging excessively? Have any repairs been made that required the removal of the LiBr? What are your solution concentrations? Temps in and out of the machine? Solution temps? Does your refrigerant have LiBr in it? Is this machine partialy salted up?

    Sorry for all the questions but need more info!!!


  8. #8
    Join Date
    Jul 2004
    Location
    Oklahoma City
    Posts
    18
    Thanks for the responses Gang. Here is some additional info:


    1. The units are Direct-Fired Sanyo/McQuay DC-U/H/S 500 Ton Absorbers.
    2. The last two chemical analysis (Lithium Bromide) came back from Rocky Research good.
    3. The inhibitors used are Molybdate and Monohydrate
    4. The higher temperatures from what I'm told started increasing several years ago. We did fix about seven leaks in the unit shortly after I got here almost seven years ago.
    5. I believe that the refrigerant does have some LiBR in it, we are verifying now.


    I do understand that the machines will not run exactly the same, the 25 - 25 degree difference in the generator temperature is the main issue, we adjusted the dampers individually (then set them back) in an attempt to lower the temperature( and pressure)in the high temp generator. On startup, after cleaning strainers the temperature in the generator runs up to 330 degrees F*. and sometimes goes off on pressure.

    My guys have minimal training on these units. We are not in a bind yet, just trying to avoid one.

    Thanks gang for the quick responses we have received so far.

  9. #9
    Join Date
    Aug 2000
    Location
    USA
    Posts
    4,990
    You may want to check the heat input on the burner and set it a little lower so it cant overfire. Sounds like its possibly overfired. This needs to be done at full load. Have had this problem before with other direct fired absorbers. Only takes a small adjustment on the regulater to get the temps down.

    At 330F your smoking your inhibitors and the octyl alcohol isnt happy at those temps either. I would limit it at 300F to 310F on startups and full load by adjusting the burner.

    Usualy the only other time I see high gen temps and pressures is with non condensables in the unit. The inhibiters can deplete out in a heartbeat, make sure you check them at least twice a year.

  10. #10
    Join Date
    Jul 2004
    Location
    Oklahoma City
    Posts
    18
    Originally posted by absrbrtek
    You may want to check the heat input on the burner and set it a little lower so it cant overfire. Sounds like its possibly overfired. This needs to be done at full load. Have had this problem before with other direct fired absorbers. Only takes a small adjustment on the regulater to get the temps down.

    At 330F your smoking your inhibitors and the octyl alcohol isnt happy at those temps either. I would limit it at 300F to 310F on startups and full load by adjusting the burner.

    Usualy the only other time I see high gen temps and pressures is with non condensables in the unit. The inhibiters can deplete out in a heartbeat, make sure you check them at least twice a year.
    Everybody here is nodding their heads, the question came up, if the gas burner tips are dirty or fouled would that increase the temperature of the burner?

  11. #11
    Join Date
    Aug 2000
    Location
    USA
    Posts
    4,990
    I wouldnt think so but your fuel efficiancy would probably go down.

  12. #12
    Join Date
    Jul 2004
    Location
    Oklahoma City
    Posts
    18
    If we adjsuted the regulator would we have to make other adjustments to the burner, such as air?

  13. #13
    Join Date
    Aug 2000
    Location
    USA
    Posts
    4,990
    Yes it should be done that way.
    Originally posted by generalforeman
    If we adjsuted the regulator would we have to make other adjustments to the burner, such as air?

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