A few years ago I was employed at a large factory in Richmond,VA. We were doing preventive maintenance on a 3 phase 480 volt motor control center. The two electricians who were to be doing the work on the panel in question had opened the main disconnect and locked it out. They checked power at the motor control panel and found the circuits dead. Then they proceeded to remove the sheetmetal covers after which they started to tighten the locknuts inside of the panel. This went well until one of them shorted his pliers between a locknut and the 480 volt buss.
He was subjected to a blinding flash but, fortunately, was not electrocuted.
A subsequent safety investigation revealed that the motor control center was fed through a transfer switch from two sources. This transfer switch had a ten minute time delay before it changed sources. That gave the false impression that the power was properly locked out. Further study showed that the transfer switch was indicated and clearly labled on the ELECTRICAL DRAWINGS.
Failure to check the drawings had nearly cost someone serious injury or possibly his life.
Both of the electricians involved that day were well qualified for the work that they were assigned but were only slightly familiar with the power feed in the area where they were working. They had not asked if there were any hazzards of which they might not be aware. Hope this serves as a reminder that all of the hazzards we face in our jobs as electricians are not obvious.
Stephen J. Cole, email@example.com
Copyright © 2003 Mike Holt Enterprises,Inc.