F.Y.I.
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By JESSE MCKINLEY
Published: August 20, 1995
The Helpful Icy Blast Q. I often see a kind of overgrown scuba tank, labeled liquid nitrogen and marked Nynex, on street curbs. (For instance, there was one the other day at Broadway and 41st Street.) Sometimes they have tubing running out of them, taped to the asphalt, which leads down under the sidewalk via manholes. What's going on here? A. Dry-cleaning with chemistry!
But before you get images of Nynex workers freezing their fingers off while washing with supercold liquids, here are the facts.
Nynex has many, many three-inch cables running under the streets, each of which contains 3,600 pairs of copper wires (each pair carries a conversation). Steam, created by subways and heating vents, sometimes gets inside these cables and causes crossed connections and corrosion of the copper wires, said Bob Varettoni, a spokesman for Nynex.
The tanks are actually more like glorified thermoses, keeping the nitrogen very, very cold. Nitrogen boils (that is, starts turning to gas) at about minus 320 degrees Fahrenheit. So when the nitrogen is pumped out of the tank into the tubing you see, it becomes a gas. The gas is compressed and then blown into the three-inch cables, sopping up moisture without otherwise affecting the copper wires, before escaping through a venting hole to dissipate in the air, like steam. Checkitout
