Do you use a flow gauge?

ChrisJ

As many know I'm fairly new to brazing refrigerant line and only do it as a hobby. I'm curious how many guys use a flow gauge with their nitrogen?



I just bought a Yellowjacket 69086 digital vacuum gauge so the next tool on the list is a flow gauge but I'm not sure if its really necessary. On my past project I simply set my flow by feel and luckily had all clean joints internally.



Also do you prefer nitrogen or another gas? I seem to recall some guys preferring argon over nitrogen



Look forward to all responses.

don_9

Guage

The only thing I use is the regulator on the nitrogen bottle.Also flakes come more rapidly with a high torch setting.Back in the old day we used 50-50 with a propane torch.flakes were not a big issue.

ChrisJ

Flakes and heat

I'm typically using a #5 turbo torch tip which seems to be decent for the size work I'm doing.



Sounds like a lot of guys just use the regulator on the bottle so thats probably best for me.

Techman

Flow control

When brazing, how much nitrogen pressure in the system will it take ,to, prevent you from making the last joint seal ? It happens w/ freons .

When using nitro, inside to tubing, there is no flaking, no oxygen, no oxidation.

Empire_2

Hey Don, How have you been?

Chris, I will use nitrogen at;...(as long as an open pipe exists) 1.5 to 2.psi depending on pipe diameter with most of the circuit almost complete.  Argon and Nitrogen are both (Inert) gases as specified by periodic table.  If I have, say only a access fitting open and finishing up brazing, I will drop to aprox.5 to 1 psi.  Works for me and hope it helped. 

Edit;  Chemist's classify N as an inert gas because it rarely reacts with other chemicals.  In the same breath, "NO" N can form many other compounds with oxygen present.  So as long as you have Nitrogen flowing through the work you are doing, you should be OK.  Nitrogen much cheaper than Argon.



Good Q:



Peace;



Mike T.

Empire_2

Inside is Most important..

Nitrogen is the most common gas used if for nothing else than it's cost.  Elimination of O2 is key, not how much pressure.  A gradual flow (if you will) is anything to keep Oxygen out.







Mike T.                       Hey Terry how are Ya?

ChrisJ

Ah

This was something I learned when I did my last joint. I had my pressure set to around 2 PSI with the service valve on the fridge shut. I then opened it and made sure I had good flow and started brazing.



On my last joint it blew the filler out so I dropped pressure to almost nothing and finished the joint. This is what made me wonder if I really needed a flow gauge or not as I've seen some guys use them.

Empire_2

I Apologise Chris

I thought you were referring to an open system.  Never,....with joints under pressure should you braze or solder.  With a 1 or 2 psi, it's not a safety issue just if the fittings are in place and there is a positive pressure, it will tend to push or spit out the filler being used.  Even when I do an entire system there is always an out for inert gas to flow.  The last joint can't be pressurized or it will or could spit out what you just put in.  As long as an open exit for the gas, be it access port, remote fitting, the gas has to be let out.

If you push 50 psi through a system not only is it excessive, but just going to make you mad.........lol  Put the N in and have an exit point.....Done. Just making a point.  It's not technical, it's common sense.





Peace;



Mike T.

ChrisJ

Ah

That's easier said then done with what I'm working on. There is a service port but only one on the high side. Adding one on the low side is near impossible as the system runs at around 28" HG on the lowisde and I'm told schrader valves don't appreciate this not to mention the refrigerant (methyl formate) will probably attack the rubber in them.





I'm guessing my best option is to leave an end open until I have all but one joint brazed and then connect that joint,wait a few seconds to make sure all air is purged and then cut the nitrogen and braze?



I am proud to say that machine has been up and running leak free for a while now. I have 2 more to do and am always looking at improving my soldering and brazing skills.



Thank you for taking the time to respond. I really appreciate it.



Something I think some guys will get a kick out of is the red funnel in the one picture is used for adding refrigerant as its a liquid at room temperature. This surgery was done to convert the machine from a damaged high side float to a capillary tube system.

don_9

Hi Mike

All is well.How are you? Are you guys into the chill yet? We are starting to gear up for no heat calls.much rather keep the summer gear on.I miss the pretty things one get to look at in the summer.lol Take care.

Techman

Nice refrig units

Lucky you. My methyl formate p/t chart only goes down to 0*f w/ a -13.20psig . So I'm thinking that being at the bottom limit of the chart that 28" vac is a little low. SH &SC ?

ChrisJ

My mistake

You are 100% correct.



Low side operates at approx 26HG not 28 my mistake.



Techman, where did you find a p/t chart for methyl formate? The only one I have is in the GE service manual for these.

Techman

P/T chart.

Hi ChrisJ, I have a book

" The Second Edition of Refrigeration", by Technical Publishing Co. Copyright 1943 . The P/T chart is in there. Got an email/fax? Or is your chart ok ?

ChrisJ

Wow

Hi Techman,



No my chart is fine, thanks for the offer though!

Its not everyday you find someone that has such information.