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  1. #1
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    Jun 2010
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    U.A. (upper Alabama)
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    Steam question for absorbtion chiller

    I was assisting in the startup of two absorbtion chillers, 100 tons each. Same steam supply at 200 psig, each with there own step down regulator. One has 2.5" supply and 2.5" regulator, low press. side 14 psig and about 235 deg. F. The other one has a 2.5" supply with a 1" regulator stepping back up to 2.5" pipe, at 10 psig and (280 deg. F)! How is this possible, steam temp. for 10 psig is around 220 deg. or so right? Keep in mind steam source is the same from a plant a couple of miles away, and no superheaters. Why is steam superheated so much more on this one? Is it the smaller regulator?

  2. #2
    Join Date
    Mar 2003
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    7,326
    no steam table in front of me, but 200 psig steam at saturated is say 290 degrees? when you reduce the pressure, the temp theoretically would stay the same, unless outside forces act upon it. things such as desuperheaters(water injection), lack of insulation, etc can effect temps. In looking at your situation, i would guess at two items. first, the reduction in pipe sizing means higher velocity for a given load, and lower transmission rate of btu's to the surrounding space, ie, the higher flow through the smaller pipe gives up less btus, at the point of measurement. second, placement of the sensor.

  3. #3
    Join Date
    Jun 2010
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    U.A. (upper Alabama)
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    Thank's flange. The sensors are in the same location on the chillers. They are identical chillers serial #1 and serial #2. (I know) There are no de-superheaters, but that's kind of where we are at. Option #1 add a de-superheater and deal with adding soft water right? Or option #2 add another 2.5" regulator and hope for the best. 280 deg.F is too hot for this machine. Oh, we did check 200 psig steam temp. and it was around 350 deg.F.

  4. #4
    Join Date
    Dec 2008
    Location
    Dixiana, AL
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    2,611
    Sounds to me like you got a screwed up temp sensor.

  5. #5
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    Jun 2010
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    U.A. (upper Alabama)
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    Confused

    Quote Originally Posted by klove View Post
    Sounds to me like you got a screwed up temp sensor.
    We checked several different places past the regulator and they were very close to the chiller sensors.

  6. #6
    Join Date
    Jan 2005
    Location
    Houston TX
    Posts
    880

    I can here my shoes squeek

    I've got a few problems with your thread, not being a smart a$$, just questioning it and yes I do have a vast steam pressure temperature chart in front of me. It's called Bing. At 200 PSIG your temperature is 387*F, at 14 PSIG it's 247*F and at 10 PSIG it's 239*F. I don't know where you got your 280*F, but unless there is a steam stretcher to add an additional 25 PSIG,or 41*F of additional heat, it ain't going to be 280*F (35 PSIG). Thermodynamics says you don't add heat when you create a pressure drop, you loose it. If this were the case there would be no TXV's, AXV's or EXV's. When I worked industrial fitting with high pressure natural gas regulators 1200- 2500 #'s and we would drop it down to 125 #'s. Even though this was all gas with no liquid the air temperature in the equipment shanty was 20*F or colder when it was 105*F outside. You said that the steam comes from the same supply piping and there are are no superheaters from the plant 2 miles away. What is the pressure / temperature leaving that plant The 1" regulator would only restrict the flow of steam. By the way I have worked on salt shakers from 80-3000 tons and have never seen a 1" control regulator used for incoming steam control to the generator/ concentrator. The smallest is 1-1/2" . Check your spec's again also look at the # of steam required at what percentage of load. In general if you have a newer high eff. you're looking at 12-18 #'s of steam per hour per ton. If it's an older design then something like 20-25 #'s of steam per hour per ton. See Yah!-GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  7. #7
    Join Date
    Jun 2010
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    U.A. (upper Alabama)
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    Quote Originally Posted by ga1279 View Post
    I've got a few problems with your thread, not being a smart a$$, just questioning it and yes I do have a vast steam pressure temperature chart in front of me. It's called Bing. At 200 PSIG your temperature is 387*F, at 14 PSIG it's 247*F and at 10 PSIG it's 239*F. I don't know where you got your 280*F, but unless there is a steam stretcher to add an additional 25 PSIG,or 41*F of additional heat, it ain't going to be 280*F (35 PSIG). Thermodynamics says you don't add heat when you create a pressure drop, you loose it. If this were the case there would be no TXV's, AXV's or EXV's. When I worked industrial fitting with high pressure natural gas regulators 1200- 2500 #'s and we would drop it down to 125 #'s. Even though this was all gas with no liquid the air temperature in the equipment shanty was 20*F or colder when it was 105*F outside. You said that the steam comes from the same supply piping and there are are no superheaters from the plant 2 miles away. What is the pressure / temperature leaving that plant The 1" regulator would only restrict the flow of steam. By the way I have worked on salt shakers from 80-3000 tons and have never seen a 1" control regulator used for incoming steam control to the generator/ concentrator. The smallest is 1-1/2" . Check your spec's again also look at the # of steam required at what percentage of load. In general if you have a newer high eff. you're looking at 12-18 #'s of steam per hour per ton. If it's an older design then something like 20-25 #'s of steam per hour per ton. See Yah!-GEO
    Brand new chillers. And I'm not as good with steam as others, but I'm better at ref. theory than most. Sounds like we need to fly you out here and let you change the gauges 5 times and still have 10 psig and 280 deg.F and let you scratch your head and hear your shoes squeek all the way back to Texas. I'm really, really, not trying to be a smart a$$.

  8. #8
    Join Date
    Jan 2005
    Location
    Houston TX
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    880

    Okay dude I'll back off

    I'm sorry to report but the last time I check you can't change physics. I would try to look in another area. You haven't mentioned anything about actual temperature readings. If you want to spin for 1st class round trip and provide all tools, lets do it. Give me model and serial and design spec's. If you are allowing yourself to use chiller sensors try looking at your module power supply voltage as this could be biasing your readings.-GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  9. #9
    Join Date
    May 2001
    Location
    Western Wa
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    1,864
    Engraved in my brain from my process control days is 15 PSIG at 250 degrees saturated.

    I wonder if you temp sensor is closer to the high pressure side on one than the other.
    Or maybe the velocity of the high pressure through the one inch is heating up the pipe downstream.

    My guess is when the modulating valve is closed and if you have the proper drip leg trap before the modulating valve, that your temp would precisely match saturation for the pressure.

    Weird things can happen, but you can't change saturation temps.
    God Bless our Veterans

    God Bless the USA

  10. #10
    Join Date
    Jun 2010
    Location
    U.A. (upper Alabama)
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    874
    Quote Originally Posted by ga1279 View Post
    I'm sorry to report but the last time I check you can't change physics. I would try to look in another area. You haven't mentioned anything about actual temperature readings. If you want to spin for 1st class round trip and provide all tools, lets do it. Give me model and serial and design spec's. If you are allowing yourself to use chiller sensors try looking at your module power supply voltage as this could be biasing your readings.-GEO
    We did, as I stated before, check the steam temp. in several locations after the regulators, and with our own therm., all being consistant with chiller sensor. IM STUMPED!

  11. #11
    Join Date
    May 2010
    Location
    Michigan
    Posts
    37
    I am not a steam expert, but I think the issue is not the PRV with the high superheat bur the larger PRV with no superheat. I expect to see superheated steam from the PRV up to where it enters the steam bundle and the machine with the 1" PRV is showing that. The 2.5" PRV machine is not. As stated in a previous post the saturation temp of 14 psig steam is 247*F so if it is 235* that would mean it is condensing in the line and maybe that is the problem. I would look at the traps after the steam bundle and make sure they are working. Maybe the steam bundle is partially flooded and it is backing up into the supply line. If this is happening I would assume that the machine output is less than expected also.

  12. #12
    Join Date
    Feb 2006
    Posts
    224
    Is that 10 psi being measured near the 1" regulator or back on the 2.5" ?? I would get it away from that hi velocity area and make sure there is a pigtail on the gauge. Just a thought.
    Ga1279 is right, it is not getting superheated without a heat source, or everybody would want one of those regulators.
    Temp is easily enough measured, pressure is a bit tougher on steam. The bit of steam fitting I did , I know that the small things are the ones that kill ya. Pitch that pipe towards the trap, eccentric pipe reducers only etc.
    Double check the pressure. Hope that helps

  13. #13
    Join Date
    Aug 2000
    Location
    Austell, Ga.
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    1,296
    This one reminds me of the great start-up at the SuperDome in New Orleans...
    3 huge 1800 ton York absorbers had the generators blown out of them in a single day when a 600psi steam supply reduced to 30 psi with the de-superheater condensate valves were closed..De-superheater pumps were running & auto valves were functioning but alas,,,,the isolation condensate valves were closed....Cost to replace the upper vessels was over 2-1/2 million$$$ since the building was literally built around these huge puppies,,,
    I wonder where that York start-up man is today....
    Ain't "None" of us as smart as "All" of us..

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