Bus Plugs Blog – Expert Safety and Usage Information

MIDWEST was in a manufacturing facility collecting data for an Arc Flash Hazard Analysis project.  While reviewing one of two main 1600 amp bus ducts through the facility, we came across something our Engineering Technicians thought was pretty crazy.  Crazy, but interesting.  One of the bus ducts had a bus plug with black soot on the side from an apparent internal fault.  It was an ITE BOS14353 bus plug and the soot had been blasted out of the seams of the cover and conduit box connectors and between the bus plug and bus duct.  The cover didn’t look like it was bent, but there was a lot of black stuff on the sides of the ITE bus plug.  We asked the maintenance man if he saw that and he said “Oh, ya,” they had a fault at the bus plug, but it didn’t trip the main breaker for the bus duct so they refed the machine from a different bus plug.  They couldn’t turn off half of production for one machine.  They didn’t touch the blasted bus plug, which was wise since they wouldn’t turn off the bus duct.  The feeder from the bus plug fed a fused disconnect mounted separately from the machine.  So they just turned off the disconnect switch, attached the LOTO, and refed the machine from a different BOS14353 bus plug to a new separate fused disconnect.  MIDWEST reconditions ITE BOS14353, General Electric FVK363, Square D PFA36100, ITE UV363, or Westinghouse ITAP363 bus plugs every day.  We know from shop experience and field service experience that the blasted bus plug was a ticking time bomb.  Sooner or later, it was just a matter of time, there was going to be another fault at that bus plug.  Probably at the connection to the bus duct.  Sooner could be an hour and later could be a couple years.  But the big concern was not for the bus plug, it was for a fault in the bus duct itself.  The black soot gets everywhere and the bus duct is very vulnerable.  If it faults, half their plant could be down for possibly days.  By shifting the attention from the bus plug to the bus duct, maintenance got an outage within days to remove the bus plug and clean up the bus duct.  A wise and safe decision.

Here’s another odd but very dangerous circumstance that MIDWEST ran into during the field data collection for an Arc Flash Hazard analysis.  The customer had an old Square D bus duct run in the oldest part of their plant. It was actually a complex made up of several buildings, the oldest being a wood structure going back seventy years.  They had mostly Square D and General Electric bus duct and bus plugs, and a small run of ITE.  The old part of the plant was used for storage.  All the manufacturing equipment had long ago been removed. There were very few Square D bus plugs still being used in the bus duct in this area. There were maybe a dozen bus plugs that were still installed but no longer in use. In most cases, the pipe and wire feeder had been removed. But we found one 100 amp bus plug, no longer used, had a conduit going into a small room full of junk. We had been told the bus plug was off and the fuses probably removed. They didn’t know where the conduit went. When we checked, and we always check, we found the bus plug closed and hot, the feeder energized. The electrician was pretty surprised. We traced the conduit to a back small storage area, dark, no lighting, where it terminated in a 6 by 6 junction box on the wall right next to the door. This circuit was “deadly hot” because the cover was missing and the conductors were sticking out of the box, wrapped with the frayed remains of old cloth type tape. This was a deadly accident just waiting to happen.  When MIDWEST recommended turning off the old bus plug; removing the fuses; and removing the conductors and conduit from the bus plug, they balked. Thought just turning it off was okay. But, since this was an abandoned circuit, not to be used again, we always recommend removing it. We consider this a safe work practice that eliminates the possibility of something “deadly hot” injuring or killing someone in the future.