Wednesday, February 15, 2012
The issue shown in this comic is a real concern in the electrical industry. The wires in a tall building are incredibly heavy. If they fall through an open conduit, they can trap and crush anyone in the electrical room. Only after they are terminated in a switchboard is it safe to be in the room.
In a finished building, the conductors are supported every few floors to protect against this possibility and to reduce the strain on the wires. During construction, if the wire is pulled in a single run from the bottom of the building, there is significant danger if the pulling rope fails.
There are two ways of reducing this danger during construction. The preferred method is to pull the wire from the roof down to the lower levels. Of course, care must be taken to make sure that the wire never gets loose at the roof. The alternative method is to pull the wire from the bottom a few floors at a time to a junction box, lay the extra wire out on the floor, then secure it in the conduit. The extra wire is then fed back into the conduit for several more floors and the process is repeated.
What happens to the ninja in this comic really should not have occurred. The supports should have held the wires in place and prevented them from falling into the room. The ninjas would have been foiled, but not dead.
Mark Robison, PE
