dry ice cold traps

[licensed to chill]

i have a trane traa screw chiller with a busted evaporator and the customer has decided on evaporator replacement versus machine replacement (bad choice).So i am stuck with removing all the water from the refrigerant circuit.
Thought about building a coldtrap due to the high costs of a manufactored one. Has anybody built one? seems pretty simple in design

[icemeister]

http://www.hvac-talk.com/vbb/showthr...ight=cold+trap

[bruiseandy]

we've got a couple at work one is covered with insulation and the other is bare. Made out of 12 and 10" aluminum pipe with 6 half inch flare fittings screwed on.

[chiller mekanik]

Plenty of people make a big deal out of this but getting a machine dry is not that big of a deal, it just takes a little time.

What part of Georgia are you in??

Contact me direct if you want me to hook you up with a heat exchanger that uses liquid nitrogen, which is 10 times better than dry ice.

Building one would take about a day or two with all of the right stuff.

You would need a 250lb tank & you would have to modify it quite a bit. You would have to make a tank within a tank, a header that will allow you to hook up multiple hoses to the machine, large hoses.

You may not have time to build one as you would likely be better off to rent one of these heat exchangers for now & make one later, if you feel like you need it.

As you know, time is of the essence. You need to get started soon. This type of heat echanger will allow you to dry this machine out completely. Of course it will be to your advantage to drain any water you can. Pulling the vacuum through this thing will enable you to keep the pump running without having to change the oil so much, if at all.

I've used this procedure & it works. It may be neccessary to use heat lamps as well. Sometimes you have to stop & thaw the heat exchanger with a torch.

Good luck!

[chiller mekanik]

Look at the reading on my fluke thermometer.

[CrayWild]

Cold traps will keep water out of vacuum pump, but does not realy help with drying.(unless micros rise above boiling point of the water) Try using heatpac on vessels to 120 to 140. I use WF100 oil in my vacuum pump and change often. If you would like more info email me.

[referteacher]

Hey Chiller Mek,
I like that set-up. We made our cold trap using a low-temp refrigeration unit with a 19D oil cooler coil for an evaporator inside the trap.

What happened to the 19XL? Discharge blow through condenser tubes? Evaporator freeze up? Have had both. (Not my fault) I just got to clean up.

[chiller mekanik]

Hey Chiller Mek,
I like that set-up. We made our cold trap using a low-temp refrigeration unit with a 19D oil cooler coil for an evaporator inside the trap.

What happened to the 19XL? Discharge blow through condenser tubes? Evaporator freeze up? Have had both. (Not my fault) I just got to clean up.

A competitor helped us out with that one. They froze it while recovering the refrigerant. We had to replace 70 or so tubes in the cooler. We got it dry though & haven't had to do anything since. We did install a core holder in the motor cooling line with a dry eye, it hasn't changed colors on us but we replaced those cores 3 times for good measure.

[_knight_]

Chiller Mek, Can you explain that process to me, and what your achieving, I'm extremely interested but lost on the concept.

[chiller mekanik]

First you want to drain any water you can out of the machine which means you may have to drill a few holes or cut & disconnect pipes. Once you've completed that you can purge some dry nitrogen through it to chase out little droplets that were missed.

A good place to hook up a large hose is at the relief valve hole, if you have a heat exchanger with a header for multiple hoses you can hook up several, the more the better.

You will want a large capacity vacuum pump thats connected to the outlet of the heat exchanger/cold trap. You are pulling a vacuum through the exchanger. You will need a few large tanks of liquid nitrogen. Run a copper line from the nitrogen tank to the inner tank on the heat exchanger/cold trap. Start a slow bleed & maintain a level real close to the top without going over. You can also play around with filling it up, letting it boil off a little then add again. It will require pretty constant supervision, its a good opportunity for some lower paid apprentices to get some overtime as shift work is the way to handle this instead of killing one guy.

If you try to pull a vacuum without a device such as this the oil will turn white very quickly & you will have to stop & change it, many many many many many many many many times.

This procedure allows you to operate the pump without having to go through multiple oil changes because the cold trap will freeze all of the moisture before it gets to the vacuum pump. Depending on the size of the machine & your vacuum pump, you can usually dry it out within 36 to 72 hours, give or take.

Dry ice will work, but it only gets down to about -105* ( takes longer ). The liquid nitrogen is much colder therefore the freezing of the moisture is almost instant. The dry ice is also messy, as you have to mix it with something that won't freeze & you have to re-load it. Once you've set this rig up you just play with a valve.

We never decided if the reading on my Fluke was accurate or if that was just as low as it would read.

[referteacher]

Chllermek: A competitor helped us out with that one. They froze it while recovering the refrigerant. We had to replace 70 or so tubes in the cooler. We got it dry though & haven't had to do anything since. We did install a core holder in the motor cooling line with a dry eye, it hasn't changed colors on us but we replaced those cores 3 times for good measure.

Pretty much the same for us. Except it was a "borrowed" tech. from another branch. When he found out what he'd done, he drove straight home, left his keys at the shop, and kept going.

Were you able to pull the tubes? Ours were bulged so badly we had to cut windows in the side of the shell and cut them out. Had to remove 150 to replace 50 frozen.

[madhat]

Do you guys have any idea how dangerous Liquid nitrogen is inside a building? When I've used it inside a building the outside doors come off the hinges, there must be cross ventilation, or it's a no go. Piped my vacuum pump outside with 50 feet of half inch copper on one job, customer squawked, but it was that or not doing the job.

http://www.airproducts.com/nr/rdonly.../0/sfgrm07.pdf

[chiller mekanik]

"Do you guys have any idea how dangerous Liquid nitrogen is inside a building? "












Yes.

[colddr469]

Made a quick one today after going through lots of oil over the week-end and still only down to 5000 microns on Tuesday evening. Used 2 30# recovery
tanks and a couple steele 10 gallon trash cans fileed with dry ice a quick oil change and 2- 2 stage vacuum pumps and got it down to 1500 microns in @ 6 hours. The thing works like a raped ape. Kinda old school but still cool. took all of about an hour and a half most of that was explaining that was a time when trash cans really were made of metal.

[onetime]

I use a reciever tank from an old c/u and put it in a half barrel ( cut the long way) and fill it with dry ice. It has always worked good for my low budget operation.

[referteacher]

COLDDR469

Works great when you have an unlimited supply of free dry ice, right?

[StillKicking]

Make good ice traps, use out of date tanks add a dip tube and replace the valves with a 3/8 fitting-or whatever line size is being used. Series two tanks before the pump. I've also used an old tow motor propane tank(many years ago). GL

[colddr469]

About 15 -20 lbs every 6 or seven hours around a 30 lb tank got over 1 gallon of water out with the vacuum between 1750 and 2000 microns.

[yorktek37]

Look at the reading on my fluke thermometer.

So where does the Plutonium go?