That’s what I was told too in the 70e classes I took.Has something changed since I last took a 70E class ten (or so) years ago? At the time, the whole reason for not allowing energized work beyond 40kcal wasn't that there weren't suits that could handle it, but rather that the shockwave would throw you across the room, causing traumatic head injuries.
There is no industry accepted way to calculate arc blast force.Has something changed since I last took a 70E class ten (or so) years ago? At the time, the whole reason for not allowing energized work beyond 40kcal wasn't that there weren't suits that could handle it, but rather that the shockwave would throw you across the room, causing traumatic head injuries.
This is an arbitrary point, based on task table PPE options, adopted by many companies. Some of these company policies go back 20 years and have not been updated to present standard industry practices.Unless something has changed in the latest version, there is nothing in NFPA 70E that explicitly states that no work can be done if the calculated energy exceeds 40 cal/cm2.
This gets into the question of "how long would someone stand in front of an exploding panel".2 second cut off
I dont think you are wrong at all. I would say there would be forces at work to help assist in a persons movement! both from the blast and our natural reactions....if they are functioning.This gets into the question of "how long would someone stand in front of an exploding panel".
I get that when you're in tight quarters you might not have a choice, but for the demonstration at least, I have to imagine most people wouldn't just stand still for 5 or 10 seconds there when their face was being obliterated by plasma. Not sure that's a scientific opinion, maybe it's wrong.
The new standard industry practice that I have seen (since 2022 ish) is if I as a 'outside contractor' need work while energized on a 480V anything someone at the plant needs to authorize it in writing and a signature. For plant mechanics I think its any voltage while energized.This is an arbitrary point, based on task table PPE options, adopted by many companies. Some of these company policies go back 20 years and have not been updated to present standard industry practices.
Large customers understand the financial risks of working hot, so it’s much easier to convince them when a shut down is needed.The new standard industry practice that I have seen (since 2022 ish) is if I as a 'outside contractor' need work while energized on a 480V anything someone at the plant needs to authorize it in writing and a signature. For plant mechanics I think its any voltage while energized.
I have yet to get that signature for my work at any the plants I have been to, they all started doing this about the same time. They just pay for a shutdown.
at one plant as part of the first planned shutdown after that policy each 480 panel got a indicator device installed in it so you can tell when its energized.
The plant guy said the cost of all those 'hot detectors' or whatever they are in the 16 panels cost less than one hot suit. We also put in a new panel next to an existing so they could shutdown one line but keep the other on, seemed like of a lot of work. But worth it to them to keep one line on while the other was in maintenance mode.Large customers understand the financial risks of working hot, so it’s much easier to convince them when a shut down is needed.