What sort of connectors does one use to flow nitrogen through tubing while brazing? It seems that Nitrogen uses the same bottles and regulators as Argon etc ( CGA580 IIRC ). For leak checking, I'm thinking a hose with a schraeder fitting to screw into the service port. But it would need to be a good one - I really don't want the whole thing coming apart at 150PSI.
For brazing: If I already had such a hose in hand, I'm thinking that a couple of tubing couplings with a schraeder brazed to the end - one 1/8" and one 3/4" - would do the job. Not much pressure involved, just flow.
For really good results you can assemble your piping, put the vacuum pump on it for a couple of minutes and then fill the system up to 1 or 2 psi with nitrogen and just keep the valve slightly open to keep positive pressure on the system. Braze the condenser fittings last as you will need to turn the valve off when doing the last joint.
Make sure you test with pressure. Speaking from experience, you can vacuum down a system with an unbrazed fitting. (Wow..that lady was pissed off mad..)
Don't vent any pressure through the vacuum pump as the oil tends to become airborne when that happens..(another pissed off lady).