Helium purge
 

Has anyone used the cheap disposable helium bottles sold for filling balloons to purge copper lines? Seems like it wouldn't be too difficult to clamp a rubber line to the filling nipple. Or turn up a quick hose adapter on the lathe.

The cheap throw away bottles may have their helium contaminated with oxygen to protect the buyers from the deserving natural selection normally caused by breathing lots of helium.
Plus you normally pressure check the system at the maximum operating pressure, which I am pretty sure you can't get out of one of those bottles.

Well crap. I thought I had a good money saving idea there too. Not too keen on a propane purge as I've seen elsewhere here. ;)

You're correct. 20% air at 260psi according to the balloon time faq.

for the cheaper of us, here's a partial list of stuff:
paintball CO2
welding argon
welding co2

I have a split or 2 to install when I get home.
I was going to use beverage/welding CO2 to pressure test.
But I have a few welding CO2 cylinders and another full 20lb can of R-22.

Can get a 5lb co2 cylinder for $50 or so. That may be the route I go.

Now we're talkin.

https://www.amazon.com/Disposable-Ta...PXWH4YPYE04FWA

Disposable nitrogen bottle, says it will hook up directly to 1/4 SAE fitting, which if I recall correctly, my gauge set uses. Simple solution, hook the bottle in to the gauges, crack the valve and purge. Close it up and run the pressure up to test. No regulator so would have to be careful on the pressure test, should be fine to ramp up slowly and cinch the valve at the target.

1/4 SAE and 4AN are the same. Commonly used on manifold gauge sets.
Once in a while you will see a 3/8 for doing big systems.

Good to know that it's a -4AN, thanks for that bit of info. After some more reading I think I'm leaning towards the paintball co2 bottle now, those nitrogen bottles are only like 1.2cf of gas at 500psi. Won't last long even purging. Not really long enough to justify nearly $30 each, anyway. I think I'm going to go with this: TRINITY PORTABLE CO2 SYSTEM FOR BAR KEG DRAFT BEER TAP KEGERATOR and add a hose with a 1/4 SAE on the end to plug directly on a service port. I can do a vacuum leak test then pressure test with propane, since I'm planning on propane for the refrigerant anyway.