Interesting thread found on plctalk.net. The forum is for PLC type folks.
http://www.plctalk.net/qanda/showthread.php?p=356043&posted=1#post356043
I had an issue with a refiner at our plant yesterday and I was surprised to see the cause. We have a refiner that operates 2 800 HP motors and the control voltage is 120. There was a bundle of wires that ran in the starter cabinet that were used for various limit switches and such. Whoever installed it thought it would be a good idea to secure the bundle to the top of the cabinet with the sticky back zip tie blocks. What we found was the bundle had come loose and fallen onto the top of the mains connection. After a period of time one of the wires rubbed and from our best guess, shorted between 2 phases. I was standing in front of the cabinet working in the 120V section of the cabinet trying to see why the amp signal was not going back to the PLC. Just before I hooked up my process meter there was an explosion and a bundle caught fire.
http://www.plctalk.net/qanda/showthread.php?p=356043&posted=1#post356043
I had an issue with a refiner at our plant yesterday and I was surprised to see the cause. We have a refiner that operates 2 800 HP motors and the control voltage is 120. There was a bundle of wires that ran in the starter cabinet that were used for various limit switches and such. Whoever installed it thought it would be a good idea to secure the bundle to the top of the cabinet with the sticky back zip tie blocks. What we found was the bundle had come loose and fallen onto the top of the mains connection. After a period of time one of the wires rubbed and from our best guess, shorted between 2 phases. I was standing in front of the cabinet working in the 120V section of the cabinet trying to see why the amp signal was not going back to the PLC. Just before I hooked up my process meter there was an explosion and a bundle caught fire.