Work on an energized disconnect

Recently, a client asked if there was something I could point to in the NFPA 70E Standard that specifically prevented a qualified electrician from working on a disconnect after it was shut off, but with the line side left energized?

I asked exactly what he meant? He said our electricians sometimes need to disconnect one of our 480 volt welders for repair or to be serviced. We sometimes have more than one welder on a circuit, so shutting off the breaker to disconnect a welder affects other welders or machines. So, my question is this: is there a specific section in NFPA 70E that prevents the above described activity? Please remember, the electrician has verified that the load side of the disconnect is off. However, he’s left the line side energized. READ MORE