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Post by cablehack on Jan 14, 2014 2:02:28 GMT
For various reasons it may be necessary to remove methyl formate from a CA. For example, wanting to work on a machine empty, or needing to reduce the charge after a capillary conversion. Of course, one can simply discharge it out into the open (away from ignition sources). But that's wasteful, and you don't really have an accurate idea of how much has been removed. It turns out that it is not only possible to recover the methyl formate, but the process is actually quite simple, and from my set up seems to be very effective. Again, remembering the properties of methyl formate, it becomes liquid at atmospheric pressure. Straight from the charge valve, there will also be some vapour as well. What needs to be done is to condense this vapour as well as collect the liquid. So now to the set up which will better explain the process. A length of capillary tubing is connected to the charge valve. I used about 8 feet (what was left over from both conversions). Because the charge valve adaptor has a Schrader connector, the capillary is soldered to a short piece of 1/4" tube that has been flared. A flare nut is also required of course.  Then an empty glass bottle is placed in another container filled with ice and chilled water. For the bottle I used one of my empty 1 litre methyl formate bottles, and the outer container was the tin can that the bottle was shipped in.  The end of the capillary is of course inserted into the bottom of the bottle. The inside of the bottle will be cold and further help with condensation. As the methyl formate vapour travels along the capillary tube it condenses back to liquid. A considerable improvement is gained by immersing the capillary tube into the ice just before it enters the bottle. This doubles the liquid flow rate. Furthermore, another tray of ice can be used with part of the capillary immersed in it. One can clearly feel the capillary tube being warm as it leaves the charge valve. You want it cold by the time it enters the bottle.  As with an NCG purge, the evaporator has to be heated with pans of hot water, and the compressor kept running.  The results were that I could not smell any methyl formate which suggests most of the vapour was converted to liquid. The process is slow, but the longer the capillary tube the more vapour will be converted, and the more efficient the recovery. To give an idea of the rate, it took about 3 hours to recover 10 oz.  Some observations to help others who want to try it; have plenty of ice cubes at hand. I found after 3hrs it had all melted and this would no doubt decrease the effectiveness of recovery. I only had one ice tray of cubes. Methyl formate bottles are the best to use because you know they are free from contaminants - but the brown colour makes it hard to see inside. You'll need a strong light. Undoubtedly there will be a little moisture contamination because of air condensing on the bottle, but the CA is forgiving and moisture will be converted to NCG's to be purged. Coiling up as much of the capillary as possible in an ice bath will help. It did occur to me to actually freeze a coil of capillary into a block of ice. However, it also occured to me that doing this might freeze atmospheric moisture in the tube and block it. |
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Post by coldspaces on Jan 14, 2014 2:36:34 GMT
Great right up cablehack. I was wondering maybe a rubber stopper with a hole for the cap tube to go through would help keep out moisture.
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Post by cablehack on Jan 14, 2014 2:47:35 GMT
Great right up cablehack. I was wondering maybe a rubber stopper with a hole for the cap tube to go through would help keep out moisture. That's a good point. I did consider it, and in fact the Sigma Aldrich bottles are designed to be used this way (they come with a neoprene seal designed to be pierced with a needle). For my MkII recovery kit, yes I'd do a few alterations, that being one of them. One could have another capillary tube leaving the bottle to allow the pressure to equalise and have its outlet in a container of oil so moisture does not get back in. |
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Post by ChrisJ on Jan 14, 2014 3:32:44 GMT
John,
Doesn't methyl formate break down to form several things in the presence of moisture, one of which is formic acid which is corrosive?
This is why I believe moisture in the system is bad, perhaps not as bad as in an SO2 machine but certainly harmful. My fear is this could be what caused the green corrosion you found.
There also must be a reason GE used a heater to transfer the refrigerant. My guess is to keep moisture and contaminants out.
Best I can tell formic acid is fairly weak but not something you would want on your skin in any concentrated amount. It's PH appears stronger than carbonic acid but weaker than hydrochloric acid. Carbonic acid is a big enemy in steam piping, specifically condensate returns because it eats iron piping.
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Post by cablehack on Jan 14, 2014 11:34:07 GMT
Well, my knowledge of the chemistry is only what I've read in the manual and patents. It is not a subject I really understand (and hated it at school). That paragraph in the manual claiming that moisture is harmlessly converted to NCG's may have given me excessive confidence about methyl formate. It does give the impression that no amount of moisture is harmful. Given the manual was written well after the CA's were put in service, I tend to think that if there was an acid problem it would be known about by then. (Maybe it was?)I assumed there was enough lard oil to accommodate the predicted amount of formic acid that would be produced. I did wonder about putting something in to neutralise the acid but wouldn't have a clue as to what and how much. I think the reason for using a heater to transfer the refrigerant is partly because it follows DR practice and thus logical to continue that way, but also it's obviously easier out in the field.. One does not have to get involved with the funnel method with the possibility of spillage etc., but also the sealed container has a known amount...the service technician doesn't have to weigh or measure anything. Ultimately, if there's any damage inside the CA-2, I'm almost 100% certain it was caused before I got it. The way its evaporator was blocked and the excessive amount of NCG's it produced after I repaired it would not be normal. The CA-1 has been running for two months now and still has no sign of NCG's. Yet, it was also run open to the atmosphere, and I rebuilt it the same way. The CA-2 will always remain a mystery  |
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Post by cablehack on May 3, 2014 3:32:17 GMT
Here's my improved extraction set up:  One obvious thing is the rubber stopper in the bottle. As the extraction process can take some time, it prevents entry of moisture. As the bottle fills, the pressure inside the bottle increases which also helps keep moisture out. It is thus necessary to release the pressure every so often, depending on the fill rate. As the pressure goes out when doing this, no moisture should enter. Instead of the bottle being in the tin can filled with ice, it now sits in my Peltier Effect car fridge. This is not only less messy, but gives unlimited time to get the methyl formate out. The ice bath for the capillary tube is now inside the car fridge rather than sitting on the Monitor Top cabinet. This considerably lengthens it takes for the ice to melt. Unless the cap tube is immersed in the ice bath, recovery results in about as much vapour as liquid which is obviously wasteful, so it is important to cool the cap tube before the bottle. The ice tray and two freezer blocks are frozen in the CA-1 prior to use. The recovery seems to be very good, with a constant rapid drip into the bottle. |
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Post by ChrisJ on Oct 10, 2015 2:23:27 GMT
So, this is what I made up tonight. The glass jar will be put in a small bucket or pot full of ice water and the large bucket will be filled with ice water. Think it'll work? |
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Post by ChrisJ on Oct 10, 2015 19:13:52 GMT
This worked incredibly well and took a lot less time than I expected. In fact, I wanted to remove 4 ounces, and ended up removing 12 because I didn't take the amount the copper tubing may be holding into consideration. I had two frozen bottles of water floating in the blue bucket to keep the condenser cool and some cubes of ice in the smaller bucket to keep the captured MF cool. youtu.be/2yukPcHImwo |
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Post by cablehack on Oct 10, 2015 22:49:36 GMT
That looks like a very effective extraction set up. With so much surface area of the tube in contact with cold water, it will condense the vapour very quickly. The slower you can release the refrigerant, the more vapour will condense before it gets to the end of the tube.
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Post by Iceman52 on Aug 16, 2016 14:29:06 GMT
Hi. I need to remove the MF from my system since I need to try and repair the compressor. It says above in the post the compressor needs to be running? Of course mine does not run. Will this set up for removing the MF still work or do I need to do it a different way.
Thanks.
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Post by coldspaces on Aug 16, 2016 17:01:34 GMT
Hi. I need to remove the MF from my system since I need to try and repair the compressor. It says above in the post the compressor needs to be running? Of course mine does not run. Will this set up for removing the MF still work or do I need to do it a different way. Thanks. The beginning of this thread shows you how I did it. monitortop.freeforums.net/thread/716/ca-soup-experiment |
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Post by Iceman52 on Aug 16, 2016 17:38:13 GMT
Ok thanks for straightening me out.This is all new to me. Just wanted to make sure.
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Post by douro20 on Mar 10, 2021 23:52:46 GMT
According to the SDS methyl formate is slowly hydrolysed by water to form methanol and formic acid.
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Post by lampe208 on Sept 1, 2021 17:31:42 GMT
For various reasons it may be necessary to remove methyl formate from a CA. For example, wanting to work on a machine empty, or needing to reduce the charge after a capillary conversion. Of course, one can simply discharge it out into the open (away from ignition sources). But that's wasteful, and you don't really have an accurate idea of how much has been removed. It turns out that it is not only possible to recover the methyl formate, but the process is actually quite simple, and from my set up seems to be very effective. Again, remembering the properties of methyl formate, it becomes liquid at atmospheric pressure. Straight from the charge valve, there will also be some vapour as well. What needs to be done is to condense this vapour as well as collect the liquid. So now to the set up which will better explain the process. A length of capillary tubing is connected to the charge valve. I used about 8 feet (what was left over from both conversions). Because the charge valve adaptor has a Schrader connector, the capillary is soldered to a short piece of 1/4" tube that has been flared. A flare nut is also required of course. View AttachmentThen an empty glass bottle is placed in another container filled with ice and chilled water. For the bottle I used one of my empty 1 litre methyl formate bottles, and the outer container was the tin can that the bottle was shipped in. View AttachmentThe end of the capillary is of course inserted into the bottom of the bottle. The inside of the bottle will be cold and further help with condensation. As the methyl formate vapour travels along the capillary tube it condenses back to liquid. A considerable improvement is gained by immersing the capillary tube into the ice just before it enters the bottle. This doubles the liquid flow rate. Furthermore, another tray of ice can be used with part of the capillary immersed in it. One can clearly feel the capillary tube being warm as it leaves the charge valve. You want it cold by the time it enters the bottle. View AttachmentAs with an NCG purge, the evaporator has to be heated with pans of hot water, and the compressor kept running. View AttachmentThe results were that I could not smell any methyl formate which suggests most of the vapour was converted to liquid. The process is slow, but the longer the capillary tube the more vapour will be converted, and the more efficient the recovery. To give an idea of the rate, it took about 3 hours to recover 10 oz. View AttachmentSome observations to help others who want to try it; have plenty of ice cubes at hand. I found after 3hrs it had all melted and this would no doubt decrease the effectiveness of recovery. I only had one ice tray of cubes. Methyl formate bottles are the best to use because you know they are free from contaminants - but the brown colour makes it hard to see inside. You'll need a strong light. Undoubtedly there will be a little moisture contamination because of air condensing on the bottle, but the CA is forgiving and moisture will be converted to NCG's to be purged. Coiling up as much of the capillary as possible in an ice bath will help. It did occur to me to actually freeze a coil of capillary into a block of ice. However, it also occured to me that doing this might freeze atmospheric moisture in the tube and block it. |
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Post by lampe208 on Sept 1, 2021 17:33:50 GMT
My CA monitor top broke the line from the needlepoint valve and refrigerant was starting to leak out I tried to save it but ended up losing probably all of it so now I need to extract if there’s any in there to ensure it’s all gone because I’m going to put r11 in any ideas on how to put the R 11 in?
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