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Post by ChrisJ on Aug 6, 2013 12:33:10 GMT
I'm wondering if it would be possible to recover methyl formate by simply wrapping a cold wet towel around the condenser and then cutting the liquid line and feeding it into a cold glass bottle sitting in a pot of ice water. Then crimp the line going into the evaporator and simply run the compressor and theoretically pump as much as possible into the bottle? Perhaps crimping \ pinching the end going into the evaporator first would be of benefit to keep air out of the system.
Thoughts?
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Post by cablehack on Aug 7, 2013 1:25:49 GMT
Why not simply extract it from the charge valve?
If the charge valve is opened sufficiently, then the float valve will not rise, meaning the methyl formate will go out the charge valve rather than into the evaporator. What methyl formate is in the evaporator will continue to be in a vacuum (with the compressor running), and will thus evaporate and be sucked into the compressor.
Heating the evaporator will also help drive it out into the compressor.
Next thing is to connect the charge valve to a piece of tubing coiled up in cold water or ice so that what vapour remains condenses and emerges mostly as a liquid.
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Post by ChrisJ on Aug 29, 2013 21:45:25 GMT
I'm hoping Allan can respond.
When you evacuated your system of the methyl formate did you use a hose or just let it spray out of the adapter or service port?
I'm concerned about it damaging my paint. And at the same time, I'm concerned about it damaging my hoses.
I plan on doing the first one outside and just need to get the methyl formate out of it before following up with the nitrogen purges before using the vacuum pump.
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Post by allan on Aug 30, 2013 3:22:54 GMT
I'm hoping Allan can respond. When you evacuated your system of the methyl formate did you use a hose or just let it spray out of the adapter or service port? I'm concerned about it damaging my paint. And at the same time, I'm concerned about it damaging my hoses. I plan on doing the first one outside and just need to get the methyl formate out of it before following up with the nitrogen purges before using the vacuum pump. I used a long piece of flared 1/4 inch copper tube to remove all the MF (purged to the outside) and used the same tube to purge with nitrogen and vacuum a couple of times which had it completely MF free! I kept the oil heater on and also had a defrost heater in the evap and a heat lamp shining on the compressor dome to help vaporize the MF. Yes you want to keep this stuff off any finished surfaces. I always wrap a towel around the top of the tank when working with the MF For reliability sake I think the best plan is new MF, especially with the high purity stuff from SA. I would probably distill and recover a MF charge that I put in but it seems like the 80 year old stuff should go, maybe overkill but comforting |
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Post by ChrisJ on Aug 30, 2013 3:33:27 GMT
Right now all I have on hand are a few extra brand new R134A type gauge manifold hoses. I think I'm going to switch the fitting on my good adapter to a 1/2 acme and use those hoses to discharge. Looks like there may be rain this weekend so I'm thinking I may run the hose out under the garage door and keep the unit inside while purging. Of course I will have windows open just to be safe as well as no open flames.
I'm pretty sure the hose will be garbage when I'm done but that's ok as I have a good quality 1/4" charge hose I can use for nitrogen and vacuuming. I just need to get the form A machine running then I can fine tune my projects. Speaking of switching connectors and adding gauges to the adapter. Should I use Teflon tape on the threads? I had considered it but didn't yet. I'm pretty certain pipe dope would be a horrible idea due to oil in it, I may never use dope on my steam pipes again due to this. I have good quality blue monster tape in various sizes and I'm assuming if I put it on but keep the first thread clear that should ensure no contamination.
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Post by allan on Aug 30, 2013 4:34:20 GMT
Right now all I have on hand are a few extra brand new R134A type gauge manifold hoses. I think I'm going to switch the fitting on my good adapter to a 1/2 acme and use those hoses to discharge. Looks like there may be rain this weekend so I'm thinking I may run the hose out under the garage door and keep the unit inside while purging. Of course I will have windows open just to be safe as well as no open flames. I'm pretty sure the hose will be garbage when I'm done but that's ok as I have a good quality 1/4" charge hose I can use for nitrogen and vacuuming. I just need to get the form A machine running then I can fine tune my projects. Speaking of switching connectors and adding gauges to the adapter. Should I use Teflon tape on the threads? I had considered it but didn't yet. I'm pretty certain pipe dope would be a horrible idea due to oil in it, I may never use dope on my steam pipes again due to this. I have good quality blue monster tape in various sizes and I'm assuming if I put it on but keep the first thread clear that should ensure no contamination. That should do it. Use the first hose for a couple of nitrogen purges and short vacuums first and then all the MF will be gone! After that switch to the good hoses and you will have no damage to these hoses. The Teflon is what I used, keeping the first threads bare |
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Post by ChrisJ on Sept 12, 2013 21:22:19 GMT
For recovering methyl formate, lets assume you have new refrigerant in a machine and want it back. Would it be possible to take a clean 30LB refrigerant tank, pull a vacuum, fill with nitrogen, purge, pull deep vacuum and then simply hook it to the machine and pull the charge out?
Maybe this is a really dumb idea but I'm assuming a 30lb tank should have quite a bit of capacity to maybe make up for the fact you're not using a recovery machine?
To empty the tank simply heat it and fill the CA as a gas? I have also assume you won't get all of it back, but 90% is better than nothing at the cost of methyl formate.
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Post by cablehack on Sept 12, 2013 23:14:44 GMT
Sounds like something worth pursuing. This reminds me of the procedure described in the CA literature about adding refrigerant. That is, heat up the refrigerant bottle to make the MF go into the CA. Instead, you heat up the CA to get the flow going the other way and your receiving bottle is in a vacuum.
But to get the refrigerant back into the fridge from your tank, why not just let it come up to atmospheric pressure so it goes back to liquid? Easier to handle that way.
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Post by ChrisJ on Sept 12, 2013 23:36:36 GMT
I don't know, how can you bring it back up to atmosphere? I'd think you need heat to get it to go in as a gas fast enough, as a liquid I don't know.
My assumption is this method would keep the methyl formate pure and away from air and moisture.
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Post by cablehack on Sept 12, 2013 23:43:01 GMT
Once you've filled your 30lb tank with MF in the gaseous form, all you'd need to do is open it to the atmosphere (or to a nitrogen supply until it came up to 0 psi). Don't forget when you open the glass bottle from Sigma Aldrich, the contents are being exposed to the atmosphere in the same way. That's one of the things I like so much about methyl formate - it's not bothered by atmospheric exposure.
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Post by ChrisJ on Sept 12, 2013 23:50:54 GMT
Once you've filled your 30lb tank with MF in the gaseous form, all you'd need to do is open it to the atmosphere (or to a nitrogen supply until it came up to 0 psi). Don't forget when you open the glass bottle from Sigma Aldrich, the contents are being exposed to the atmosphere in the same way. That's one of the things I like so much about methyl formate - it's not bothered by atmospheric exposure. Wouldn't it being exposed over time cause it to break down due to moisture in the air? |
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Post by cablehack on Sept 13, 2013 0:33:31 GMT
It probably would if it was left in an unsealed container, but it'd probably all evaporate first.
I refilled my CA-2 in early December last year. After doing so, I simply put the lid back on the glass bottle. It was probably about 3/4 full after I finished with the CA-2. It was summer and moderately humid, plus the bottle had just been taken out of the fridge so it was cool. Thus, 1/4 of the bottle consisted of atmospheric air, and some condensed moisture after I finished.
8 months later I used most of the remaining contents of that bottle for the CA-1. The fact it had been open to the atmosphere for several minutes had not harmed the contents - I still haven't had to do one NCG purge to the CA-1.
My experience has been that it's quite OK to open the bottle to the atmosphere, but put the lid back on when you're not actually pouring it.
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Post by ChrisJ on Sept 13, 2013 0:45:36 GMT
How long would you estimate it takes to fill a CA-2 after cap tube conversion? I have the 2 liter bottle and am not planning to weigh it. I figure, I should need roughly half of it to fill the machine so I'll just go by eye and keep it towards less rather than more.
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Post by cablehack on Sept 13, 2013 0:59:35 GMT
I think I had my CA-2 filled in about 10 mins or maybe less, but that was filling the whole thing in one go; 2.75lbs. 3 or 4 of my orange funnels full I think - I have it recorded somewhere.
The slow bit is when it sucks into the charge valve; you need to let it in slow enough so you've got time to shut the valve just before the funnel empties. You'll probably use a little less than half your bottle, but put it in several stages and run the compressor for a few mins to get an idea. For the CA-1, I ran it after each funnel full...the bottom of the evaporator will start getting cold even with half a pound in the system. If you've got kitchen scales, they'll be accurate enough to give you a guide.
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