View Full Version : Flooded Absoption Unit
04-16-2008, 04:41 PM
Have a direct fired Trane absorber which has a substantial number of tube leaks due to poor water treatment. Despite our recommendation to replace, customer wants to plug leaking tubes and attempt to run. Solution is diluted, specific gravity 1.23.
I have two questions:
Machine is 1992 vintage; Is inhibitor lithium molybdate or lithium arsenate?
Can I ship the bromide to someone else for reclaiming and reworking?
04-16-2008, 05:36 PM
Direct fired in 92 would probably be the Thermochill/Kawasaki design. It would be most likely nitrate inhibited. Only the 2 stage classic was arsenite inhibited. I would guesstemate at about 20% LiBr, my charts don't have that range. Plug the tubes and just use the machine to redistill the refrigerant out of the LiBr, thats normally how its done. Model number would help.
04-16-2008, 10:04 PM
Thanks Absorbertek! We had told the customer we'd have to distill the water out of the charge.... he didn't want to pay for the manhours to do it.
It's an ABDL 055. Not sure what the original charge was. Planned on cooking it down to where the readings looked about right and it started to produce.
04-16-2008, 10:14 PM
Even after cooking it down, you may come up short on LiBr if any leaked out. Customer sounds like a smacked arse. To cheap for proper water treatment, already complaing about bill due to his neglect. JMHO
04-17-2008, 09:27 AM
ABDL is inhibited with molybdates. Do not mix with nitrates. Mixing enough nitrates with molybdates will cause the chiller to outgas to the point the bromide charge will be useless.
There is no substitute for proper water treatment.
04-17-2008, 04:52 PM
Many thanks again. We believe the machine to be DOA. 76 of 94 condenser tubes are leaking as well as many tube rolls. Tube sheets look bad. Customer still talking about trying to salvage it from the graveyard. Gave some bum info: it's an ABDL 035 not 055 if that makes any difference other than charge size.
04-17-2008, 11:33 PM
Sounds like an expensive retube job. I have cut the crown sheets out in the water boxes, had new ones made at a machine shop and rewelded them in. Worked out well.
You could actualy see bubbles comming thru the crown sheet with 10 PSI of nitro in the machine. When we pulled the tubes, chunks of crown sheet were pulling out with the tubes when we started. :eek:
04-18-2008, 05:21 PM
so how do you keep the air from destroying the interior of the machine during this process. you can't put a nitrogen bleed big enough on it to keep all the oxygen out. When you restart the unit all that corrosion and all the debris busted loose during the retube process ends up in the sprays and the machine won't make tonnage. We've tried installing filters ahead of the sprays to prevent them clogging but still had no success.
These tube sheets definitely need replacing. Spray'em down with soap and they look like a washing machine gone beserk.
04-18-2008, 07:45 PM
A lithium hydroxide was is once you pull whats left of the charge out. I would then do another lithium hydroxide wash after the machine is sealed up and dump it to get the crap out. What size inline filters did you use? I would go with a US filter in the 10 to 100 micron range right off the solution pump. Nothings going thru it into any nozzles. Now if your nozzles are plugged already thats another story.
Does this customer know they are looking at $100k plus job on a 350 ton absorber? I hope they pay well.
04-19-2008, 01:19 AM
If the rest of the machine is in pretty good shape you might want to consider just replacing the generator section if Trane can produce one or if you can find a used machine that has a good generator section. Or replace the chiller with a used one if you can find one.
Unfortunately Lithium Bromide Absorption Chillers only have a life expectance of 10 to 15 years and it sounds like the one you are working on is pretty much in the dead zone. If your plugged tube count on the condenser is more than 10 percent then even if you can get this dog to run it will come up short on refrigerant production which will limit the output of the machine. Even if you replaced the tube sheets and re-tubed the condenser you will still have an old machine that has been seriously compromised and you can expect more problems in the near future.
Where I used to work we had around 45 absorption chillers and we made them last up to 30 years. But it cost us dearly. Over the years we put a lot more into the chillers than it would have cost to replace them. Eventually they all did get replaced with a centralized Cogen/Chiller Plant.
04-19-2008, 02:15 PM
We're going to recommend replacement, but if the customer so desires, where can I find the filters you referred to along with valves to isolate them. Do they still make diaphragm valves that big (like on the old 16c's and E's)? We've tried several styles of ball valve but vendor would not guarantee a seal below 29" Hg.
04-19-2008, 03:15 PM
High performance butterfly valves work fine. York uses multiple butterfly valves on thier units and I have yet to find a leak on one. I would also areate the solution to remove any copper and filter it on the way out and back into chiller to help clean it up.
04-21-2008, 04:50 PM
Thanks again for the advice. I had forgotten about the butterfly valves on the Yorks. Will post more info if the customer attempts to resurrect this beast.
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