Conduit Explosives

Conduit Explosives

Since the 1940s there have been technological improvements in electrical conduit.  Over the years, in using conduit for electrical work, I have run into some unusual circumstances.

For instance, when building on top of a concrete slab very often the conduit will be put in place in the floor before the cement is poured.  The conduit ends are located so as to come up within the space of a future wall.  Then as the building goes through its various construction phases there are wiring raceways in which to pull wire.  When a wall is constructed where the conduit has been stubbed up, new sections of conduit are attached as needed to get to the termination points.

To run wire through the conduit a semi-rigid wire (called a fish-tape) is run through the conduit to an opening, wire conductors are fastened to it, and then the wire is pulled back through the conduit to the point where you are working.

There are a certain phenomena surrounding open ended conduit.  Some people are fascinated by an open conduit end, and will drop things into the open conduit.  I guess they just can’t help themselves.

One place we were working was next to a fast food place.  Someone emptied a bottle of Coca-Cola down one pipe.  When the liquid evaporated it left behind a substance of sticky syrup in the pipe.  Contrary to how cola works with your digestive system, this instance made it impossible to push a fish-tape through the conduit.  The only solution was to dig out the pipe and replace it.

Sometimes people would drop a marble or a little rock down the pipe.  The drag produced by these items made it very difficult to get wiring pulled.

One time, at a job site next to a college dormitory, the dorm residences used the open conduit as urinals.

Worse than that, yes – worse, was the time we terminated some conduit stub outs inside a location for concrete pillars.  Unknown to us the concrete workers had allowed some wet cement to get into the open pipes.  When the cement set it was impossible to get the concrete out of the pipe.  When we returned and attached the next sections of conduit to the stubbed out ends, we didn’t know about what was now in the conduit below.  Of course we found out when we attempted to fish the wire into the raceways.  Our boss suggested that we drop lit firecrackers down the open pipe to blast the concrete away.  It was a good idea that worked on some, but then we found one conduit that had too much concrete in it.

The ensuing blast took the conduit right out of the concrete pillar, taking a chunk of the pillar with it.  The conduit was split open, so we cut the bad piece out, put in a fresh piece of conduit, and continued.  We let the cement finishers figure out how to deal with the disfigured pillar.  However we learned to cover the open ends of conduit.

I know of at least three times where someone deliberately drove a nail through the center of the conduit into the wood framing.  On one of those occasions I was able to push the fish-tape past the nail underneath it and attach some of the wires and pull them back through.  Then I sent the fish-tape through one more time and got it to pass the nail on the upper half of the conduit, attach the rest of the wires and pull them through.

I never heard that it electrified the nail.

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