best way to clean lines after soldering?

[wulff]

I installed a new expansion valve and it was the 'sweat' type where you have to solder it in place, I know you are not supposed to flush an expansion valve so what is the best way to remove any flux as most fluxes are acid based? I hate the thought of the flux mixing with the oil, true there isn't a lot but any would seem too much.
The filter-drier was the same but I bought flare-fitting replacements to prevent this but already installed the expansion valve...duh! :confused:
I have thought about cutting the line and adding flare fittings (and clean the EV while it's off).
What do you guys think? Anyone ever wonder about the flux or had this issue?
Thanks
Phil

[monkey spanners]

Hi Wulff,

What sort of solder are you using?

I usually braze in txv's with 15% silver rods which don't need flux so long as the txv has copper or copper plated connections as Danfoss and Sporlan one do. I wrap a wet rag round it and use oxy acetylene. Same with driers, but you can use 5% silver as its a bit cheaper.

I have used 40% silver rods and flux, this sets once cool and i just chip off the bigger bits then soak the rest with a wet rag then clean off with emmery strip.

Jon

[wulff]

I am using a paste that says it can be cleaned up using water. I am at home right now so I don't know what the brand is but the solder is something like 50% silver and it will only work if the paste is thoroughly on every part of the copper you want solder on.
What about running di water through the tubing then purge it with nitrogen till it's dry?
Thanks for helping.

[nike123]

I am using a paste that says it can be cleaned up using water. I am at home right now so I don't know what the brand is but the solder is something like 50% silver and it will only work if the paste is thoroughly on every part of the copper you want solder on.
What about running di water through the tubing then purge it with nitrogen till it's dry?
Thanks for helping.

What is done, it is done. You could change filter dryer with one with portion of activated aluminum to catch residual flux like Danfoss DCL driers.

Don't even think about introducing water in circuit.
What you are describing here is probably soft soldering (<400°C). In my part of world, we do hard soldering (brazing which is above 500°C to 800°C).
If you use 30-50% silver rod and dry borax powder only by what is stick on the rod, you will be introducing minimum flux to inside of circuit. That is used only for disimilar metal jonts and for joints where components are under great mehanical stress and need more elastical joint. In all other joints (copper to copper) we use copper-phosphorus 94/6 rod without any flux (phosphorus in it is actually flux).
If you open modern VRF unit made in Japan you will hardly see any joint made with silver. Almost every joint is made with phosphorus 94/6 rod, therefore no flux. All components that are copper plated can be brazed with 10-15/% silver rod without use of any flux.
So, stop soldering and start brazing.;)

[wulff]

Thanks for the reply Nike, I don't have access to brazing equipment as our company is small. I decided to use flare fitting in place of the brazed fittings I replaced.
Thanks again for your help.