[TowerTalk] [Bulk] Fwd: where the condensation comes from

[Tom_N2SR]

 One could rent a tank of nitrogen from their local gas supplier.  Purchase (or rent) a reduction control valve (they typically have two pressure gauges, one for the tank supply, and one for the lower pressure output).  Run a small hose from the gauge to the conduit, and seal the ends of the conduit.  Once the nitrogen floods the conduit, it only takes a few psi to maintain it.  When the tank goes empty, replace it.  
Nitrogen is a cheap gas.  It shouldn't cost that much to rent a tank.   
Dry nitrogen is used in aerospace testing all the time.   We use it to drive out air from thermal cycling chambers, which are used to cycle units to extreme temperatures.  
Tom, N2SR

      From: Grant Saviers <grants2 at pacbell.net>
 To: Hans Hammarquist <hanslg at aol.com>; towertalk at contesting.com 
 Sent: Monday, February 1, 2016 10:59 AM
 Subject: Re: [TowerTalk] [Bulk] Fwd: where the condensation comes from
   

What matters most is the temperature of the buried conduit vs the wet 
bulb of the air entering the conduit.

One end plugged stops the flow, and both ends plugged are usually not 
hermetic so changing atmospheric pressure brings in moisture. (in trying 
to make gas pressure seals, I found it surprising how much flow goes 
down inside regular stranded wire).

So, plugging the outside end of the conduit and leaving the inside end 
open is maybe sometimes possibly better than both ends plugged.

IMO, the only "sure thing" for a dry conduit is a low flow or slight 
pressurization of very dry air.  Since both ends of my conduits are 
outside, I use direct burial cables and don't worry about condensation.  
In fact, a plus of condensation is it keeps the wire pulling lubricant 
active, so removing cables/coax is much easier. Nice when I was 
salvaging about a thousand feet of LDF4 and LDF5 from conduit with 
condensation.

Grant KZ1W