Voodoo Time Dot Com

Today I learned of the phenomenon of the “flying manhole cover”. I have never ever heard of this before. I never even knew manhole covers had even the slightest affinity for aviation whatsoever. But apparently they have.

Evidently, underground electrical wiring, when frayed or otherwise worn out, can begin to melt its shielding which creates pockets of explosive gas. Eventually this gas is ignited by a spark or superheating caused by the wiring itself. If you know how an internal combustion engine works, then you know what comes next.

The explosion causes a pressure build-up which is capable of launching an 85-pound manhole cover up to 50 feet in the air. Consequently, manufacturers are making slotted manhole covers which help prevent the high pressure buildup that allows for these explosions.

By the way, in case you didn’t know, manhole covers are usually round so that they cannot fall back into the manhole.

Am I the only one who thinks the word ‘manhole‘ sounds like it ought to mean something obscene?

This entry was posted on Thursday, October 24th, 2002 at 11:46 pm and is filed under Learning. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.