Sure, it's very common to flush a system with dry nitrogen for that reason. But of course if you have to fully open a part of the system you're usually out of l

Sure, it's very common to flush a system with dry nitrogen for that reason. But of course if you have to fully open a part of the system you're usually out of luck (also you usually don't have valves at every intersection etc., so some part may still be exposed to the atmosphere even if part is "kept dry").