Safety with A3 class refrigerants

[kay86]

Hello, sorry for bothering again. I know that ATEX recovery machines and vacuum pumps, which should be used while dealing with refrigerants such as R290 and R600A because they are highly flamable and potentially explosive. In my case, I plan to build my own refrigerant system using R290 and since I'll have to proceed with some trial and error expecially with the cap tube, I will need to vent the refrigerant, use nitrogen to get as much R290 out as I can, and then braze / vacuum again. I know that the refrigerant can and will mix with the oil, so if you flush the system with nitrogen, it doesnt mean that there is no refrigerant left inside. Expecially when you're vacuuming out the circuit, the refrigerant will boil out and will go thowards the pump. This worries me because I don't have an ATEX vacuum pump and I'm afraid that the little R290 pumped out, can burst due to some sparks in the vacuum pump itself. This is a custom diy project and I'm the only person that can be endangered, so I don't pose any risk on others. But still, I'm trying to learn as much as I can and to follow the safest path for the realization of this project, however an ATEX pump that is suitable for this job is pretty expensive, expecially if I can work safely enough using a different strategy that wouldn't be suitable while working as a company for customers but it's good enough for DIY. For example, I've seen a guy on YT using two refrigerant compressors in cascade for this exact job but I'm not sure how to feel about this. Can you guys kindly suggest me how I could proceed on this matter? Thank you!

[kay86]

A quick note, why am I doing this? I need to realize a cold trap for a vacuum pump and in my country dry ice is extremely expensive and hard to find, exactly the opposite as in the US. Also, even if it costed very little, it wouldnt be feasible because I plan to run this cold trap 24/7. I've tried reaching out to two different technicians to pay them to build this system for me, but they refused to help, so I decided to take the matter on my hands and I've learned that this is an extremely complex and fashinating world.
Also, why am I planning on using R290 refrigerant? For many reasons. It's inexpensive, it's eco-friendly, it's very efficient, it has the exact boiling point for a -35/-40 cold trap and it's perfect for LBP applications. Thanks again for reading all of this, I have a lot to learn and I hope you guy can give me valuable suggestions

[seanf]

Did a hydrocarbon course and dont remember using a ATEX vacuum pump.
Im sure we just used a standard vacuum pump, but it was plugged into an extension cord so that it gave you a on/off switch that was 3 metres away from the pump/work area.

I think the guidance on the course for unbrazing was. Vent the refrigerant, charge with nitrogen to 75 psig, vent nitrogen, vacuum system, charge with nitrogen a second time, vent nitrogen, vacuum a second time, charge with nitrogen a third time, vent nitrogen, keep the system venting while brazing. All in a well ventilated area/or outside.

Could you use a hand expansion valve or a needle valve instead of a capillary?

If your just doing testing with different lengths of capillary tube, could you use flared joints at either end to reduce the need for brazing on a system with refrigerant in it?

[kay86]

Could you use a hand expansion valve or a needle valve instead of a capillary?

Hey seanf, thank you for you precious informations. Yes, the compressor that I'm thinking to purchase does support installations with an expansion valve, however I never look too much into them because my circuit will be very small with roughly 60/70 grams of R290 at most and I'm not sure if expansion valves are very common in such low power applications.

If your just doing testing with different lengths of capillary tube, could you use flared joints at either end to reduce the need for brazing on a system with refrigerant in it?

This would cause a little bit of refrigerant loss and I would also introduce air and humidity, right? Would this be a problem?
Thank you!

[seanf]

Hey seanf, thank you for you precious informations. Yes, the compressor that I'm thinking to purchase does support installations with an expansion valve, however I never look too much into them because my circuit will be very small with roughly 60/70 grams of R290 at most and I'm not sure if expansion valves are very common in such low power applications.

A small needle valve maybe?


This would cause a little bit of refrigerant loss and I would also introduce air and humidity, right? Would this be a problem?

Just for testing different capillary lengths. As long as your leak testing and vacuuming the system, as you would have to if brazing, using flared joints should ok.
Once you know the capillary length you need, braze it in.

Thank you!

................

[kay86]

Amazing. Thanks a lot!