Steam question for absorbtion chiller

[cperk]

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?:anyone:

[flange]

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.

[cperk]

Thank's flange. The sensors are in the same location on the chillers. They are identical chillers serial #1 and serial #2. (I know) :eek2: 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.

[klove]

Sounds to me like you got a screwed up temp sensor.

[cperk]

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.

[ga1279]

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

[cperk]

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$$.

[ga1279]

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

[Randy S.]

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.

[cperk]

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!

[LiBrman]

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.

[bertoh]

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

[RichardL]

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....

[ga1279]

I kind of think he lost his job, Now he is walking down I-10 carrying a sign "will install absorbers for food" -GEO

[bertoh]

oouch!! that bang would have hurt ones pride.

[klove]

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....

He probably went to work for jci shortly thereafter......

[cperk]

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

It's on the 2.5" pipe down stream of the reg.. It already had pigtail and new gauge but we replaced both of them. The other chiller that I thought steam temp. was normal on (because I checked temp. when reg. was backed off) turned out to be the same temp. when machine was on and control valve at 100%, with more steam going through regulator. Waiting on an engineer, but I think we are going to install another reg. outside on 200 PSI steam and drop it to 50 or so to maybe get rid of some of the superheat instead of having 380 deg steam 15 feet from the chiller. Oh yeah, chiller is designed for 320 deg max inlet steam and up to 75 PSI. Also it's not getting superheated, It's just not having enough time to get rid of the superheat because regs. are so close. I think?

[Randy S.]

Do you have drip legs and drip leg traps in front of the control valves?

Just wondering.

[cperk]

Do you have drip legs and drip leg traps in front of the control valves?

Just wondering.

Yes and yes.

[flange]

hey, ga, you ight want to become a tad more educated about steam before posting wrong information. THE ORIGINAL steam supply is 200 psig, which at saturation is 387 degrees according to your post. when pressure gets reduced, it doesnt automatically drop temp on the saturation scale, so you then have SUPERHEATED, lower pressure steam. this is a common mistake made in steam troubleshooting. the 280 is real, and can wander, depending on orifice size, transmission of btus to the surrounding air, etc. lower velocities will make for higher surface temps, as he has seen. In addition, the size of the regulator is irelevant, as they are sized by cv, or pounds per hour. i do agree that larger regs with lower velocities are better, but not always done that way by the choo choo men.

this reminds me of the dupont site that used city steam, coming in at 290 psig, and installed new commercial steam rad valves every year, because they kept failing. my service guy asked me to meet the dupont choo choo men to explain superheat. they told me i was nuts, that ten psi was well below the rated pressure of fifteen, and showed me the steam tables indicating temp was fine as well. valves were honeywell and rated at 249 degrees f, but since it was being reduced from 290 psi to ten, the temp was around three hundy on the pipe, outside, in the winter. they told us our instruments were bad, got theirs, and saw the same.......final answer was, and i quote "i must have missed that steam class in college, sell us the right valves".

[cperk]

hey, ga, you ight want to become a tad more educated about steam before posting wrong information. THE ORIGINAL steam supply is 200 psig, which at saturation is 387 degrees according to your post. when pressure gets reduced, it doesnt automatically drop temp on the saturation scale, so you then have SUPERHEATED, lower pressure steam. this is a common mistake made in steam troubleshooting. the 280 is real, and can wander, depending on orifice size, transmission of btus to the surrounding air, etc. lower velocities will make for higher surface temps, as he has seen. In addition, the size of the regulator is irelevant, as they are sized by cv, or pounds per hour. i do agree that larger regs with lower velocities are better, but not always done that way by the choo choo men.

this reminds me of the dupont site that used city steam, coming in at 290 psig, and installed new commercial steam rad valves every year, because they kept failing. my service guy asked me to meet the dupont choo choo men to explain superheat. they told me i was nuts, that ten psi was well below the rated pressure of fifteen, and showed me the steam tables indicating temp was fine as well. valves were honeywell and rated at 249 degrees f, but since it was being reduced from 290 psi to ten, the temp was around three hundy on the pipe, outside, in the winter. they told us our instruments were bad, got theirs, and saw the same.......final answer was, and i quote "i must have missed that steam class in college, sell us the right valves".

Thanks, flange. I'm glad to see someone else has seen this. I know there is some absorber techs that have run into this before also.