Every so often, I will see a large canister of Nitrogen with a hose going into a manhole.
Sometimes I see them straped to the side of a telephone pole.
I’ve always wondered, what exactly is the Nitrogen being used for?
The canisters are used to pressurize telephone cables with dry nitrogen. This forces water out which may have seeped in as the result of a repair or splice. Once the cables have been purged, the nitrogen cannisters are removed. A bit of information can be found here.
thank you!
Another one of life’s mysteries, solved!
The nitrogen, as an inert gas, helps to prevent oxidation of the copper conductors. It is used not just to displace water, but also oxidizing gases, such as, well, oxygen. This type of cable is generally called “aircore,” and is almost obsolete. Pretty much all new copper telephone conductors are filled with a petroleum jelly, both in underground and aerial deployments. And aircore cable currently in place is rapidly be replaced as demands for higher data throughput rates, such as DSL, require better conductors.