Arc Flash Compliance
- Thread starter tmc
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bphgravity
Senior Member
- Location
- Florida
I think you need to provide more detail...
Arc-Flash is a concern for any electrical service and equipment.
Arc-Flash is a concern for any electrical service and equipment.
When dealing with public buildings the NFPA70E rules don't change.
If you are working on energized equipment and have done your flash hazard analysis you will have determined the appropriate protection boundaries. Simply set up barricades to keep the public out of your protection boundaries and it would be a good idea to post a watch to ensure that the public stays out of harms way.
If you are working on energized equipment and have done your flash hazard analysis you will have determined the appropriate protection boundaries. Simply set up barricades to keep the public out of your protection boundaries and it would be a good idea to post a watch to ensure that the public stays out of harms way.
zog
Senior Member
- Location
- Charlotte, NC
tmc said:
You are required to comply, have been since 1995. Here is a checklist of things to do to get in compliance.
L
Lxnxjxhx
Guest
i guess... it won't Demolish the building
i guess... it won't Demolish the building
From
http://en.wikipedia.org/wiki/Arc_Flash
"As an example of the energy released in an arc flash incident, consider a single phase-to-phase fault on a 480V system with 20,000 amps of fault current. The resulting power is 9.6MW. If the fault lasts for 10 cycles at 60 Hz, the resulting energy would be 1.6 megajoules. For comparison, TNT releases 2175J/g when detonated. Thus, this fault energy is equivalent to 736 grams of TNT, or approximately 1.5 pounds."
I think even robots would need PPE for this kind of thing.
i guess... it won't Demolish the building
From
http://en.wikipedia.org/wiki/Arc_Flash
"As an example of the energy released in an arc flash incident, consider a single phase-to-phase fault on a 480V system with 20,000 amps of fault current. The resulting power is 9.6MW. If the fault lasts for 10 cycles at 60 Hz, the resulting energy would be 1.6 megajoules. For comparison, TNT releases 2175J/g when detonated. Thus, this fault energy is equivalent to 736 grams of TNT, or approximately 1.5 pounds."
I think even robots would need PPE for this kind of thing.
Wonderful sound bite - but I suspect, highly misleading. Wikipedia sometimes gets carried away. Ten cycles is 170ms. I am not familiar with the detonation speed of TNT, however it it more likely in the milisecond or less range. Perhaps one of our members is familiar. And the rate, or power is what makes the blast.Lxnxjxhx said:
For example, there was a recent in the IEEE journal about Li-ion battery makers. The energy density is approaching that of a hand grenade. Anybody worried about carrying their laptops?
I'm not saying the stated arc-flash is not dangerous, I'm saying it is not 1.5 lbs of TNT.
carl
zog
Senior Member
- Location
- Charlotte, NC
Lxnxjxhx said:
Nope, just a special high temp paint.
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L
Lxnxjxhx
Guest
1.5 pounds of tnt
1.5 pounds of tnt
Without going into the calculations it may still be in the ballpark because they didn't say the energy from the different sources was released in the same time.
Some say a lightning bolt contains 10^9 joules of energy. If you could release it over 1-1/2 weeks it would give you 1 kW for this time duration.
Also, the same amount of energy, 45 foot-pounds, is contained in a handshake, a 45 cal. pistol bullet and a fatal dose of radiation.
I guess the duration of an explosion is a few milliseconds. I read once that some kind of high explosive, strung out in a thin line, burns at 18 miles/sec.
Heathkit used to make some gadget that detects a gasoline fume explosion in progress and fills your yacht with fire-suppressant foam within 5 milliseconds.
Speaking of explosions, I always wondered what the difference was between an explosion and rapid burning.
A guy who designed nuclear weapons for a living back in the 50's told me that rapid burning has a high but constant burning rate but an explosion has a burning rate that increases with time.
If an engine knock meets this last standard, it really is an explosion in the cylinder.
1.5 pounds of tnt
Without going into the calculations it may still be in the ballpark because they didn't say the energy from the different sources was released in the same time.
Some say a lightning bolt contains 10^9 joules of energy. If you could release it over 1-1/2 weeks it would give you 1 kW for this time duration.
Also, the same amount of energy, 45 foot-pounds, is contained in a handshake, a 45 cal. pistol bullet and a fatal dose of radiation.
I guess the duration of an explosion is a few milliseconds. I read once that some kind of high explosive, strung out in a thin line, burns at 18 miles/sec.
Heathkit used to make some gadget that detects a gasoline fume explosion in progress and fills your yacht with fire-suppressant foam within 5 milliseconds.
Speaking of explosions, I always wondered what the difference was between an explosion and rapid burning.
A guy who designed nuclear weapons for a living back in the 50's told me that rapid burning has a high but constant burning rate but an explosion has a burning rate that increases with time.
If an engine knock meets this last standard, it really is an explosion in the cylinder.
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