Soldering with/without nitrogen?

[mooka]

Reading various posts I notice some solder with nitrogen flowing in the copper. This is something I have not done, and am wondering why do it? Would it not blow out the solder from the joint? When I say solder, silfos is what I mean. How many psi are used when doing something like this? I have pressure tested with nitrogen, after the soldering, never used it while soldering.
Thanks

[Brian_UK]

When you apply heat to copper the surface will begin to oxidise and create debris.

Flowing a low pressure of nitrogen removes the oxygen and therefore the chance of oxides forming.

Oxides when on the inside of the pipework will flake off or wash off in the lubricating oil and begin blocking up the smallest orifices it can find. These are normally the capillary tube or TXV.

As aid before, you only need a few psi of nitrogen to flow through the pipes when brazing.

[mooka]

Going to give this a try tommrow. I usualy use a flux, says its compatable with silfos and was hoping this flux would prevent the oxides. Handy Flux is what I have been using. Its on the silfos website, I would post the link but cannot until my 15 posts are up.

Thanks for the quick reply.

Tim

[coolments]

Hi Mooka

I always find the attaching the nitrogen at lowest part of the fridge pipe when purging is best, just a low amount trickling through the pipe work, should feel equivelant to blowing gently on the palm of your hand at an open end at the other side of the pipe work. Nice clean internal pipes is the result, try cutting a braze out you have done this way, you will be astounded by the difference compared to not using it.

[mooka]

I am going to go in early tommrow and test this at the shop, not doubting any of you, but this may change the way we do business.

Tim

[Argus]

.

Test it like this.

Make two joints using your normal brazing rod. One under Nitrogen flowing through, the other without, then cut them both through the joint and look at the insides of the joint area. That should convince you.

The nitrogen is not under pressure, just enough to displace air inside the pipe.

It's basic good practice, even to the extent where, in the commercial world, installations that prove to be done without nitrogen will be refused. I've seen whole new installations ripped out and re-piped for this reason.

If you're doing domestic fridge work, I'd say that it's doubly important because the copper oxide can cause greater damage, due to the small size of the system and the capillaries, than in large plant.
It can block driers and cap tubes, also, it is an extremely effective abrasive when it gets in the compressor -expect surface damage on the moving parts.

.

[mooka]

Tested just as Argus said and wish I had the digital camera with me. The two old timers at the shop said, yeah everyone knows that. Not sure that I have ever watched them do it. Thanks for the heads up!

[BigJon3475]

Tested just as Argus said and wish I had the digital camera with me. The two old timers at the shop said, yeah everyone knows that. Not sure that I have ever watched them do it. Thanks for the heads up!

Of course they did........everyone knows that you just hardly ever see anyone actually use it. When I first started I saw a nitro tank sit for what had to be at least a year before I started questioning why we had it. After some research I asked everyone else about it they all "knew" that also......Even if they never practiced it.

[Argus]

Tested just as Argus said and wish I had the digital camera with me. The two old timers at the shop said, yeah everyone knows that. Not sure that I have ever watched them do it. Thanks for the heads up!

I'll bet one was clean and the other was black?

It's the black copper oxide that does the damage.

.

[paul_h]

Yeah, every knows about using nitrogen, but it's not common to use it on small units for one main reason. You can't pressurise the system with nitrogen (your weld won't work), you need two gauge access points installed, one for nitrogen in, and one for nitrogen to flow out of the system. It's a PITA for small splits with no discharge access point, or fridges with 3/16 steel condenser lines and no access points at all.

[mooka]

I was thinking of my next split unit job, thats all we mostly do, is to take the shroder out of the high side. Then nitrogen 1-2 psi in the low side via the manifold and bottle and silfos away. Will post my problems/no problems on here when done.
Thanks
Tim

[Argus]

.
It’s not complicated – you can assemble a row of joints, just blow out and air and trickle Nitrogen through with an open end, that way you don’t build up any pressure.

You only need a rat’s fart above atmospheric pressure,

.

[US Iceman]

You only need a rat’s fart above atmospheric pressure,

I'm afraid you are using some highly technical language I am not familiar with. What exactly is the pressure capabaility of a rat?

I suppose it depends on the size of the rat and his diet?

[Pooh]

US Iceman
I respectfully note that you implied that for the process described by Argus that only a male RAT can be used have you a problem with the female members or the RAT family or is there something different in their dietry intake that would make their dietry gases less or more powerfull.

Ian