Arc Flash - Take it seriously

[ramdiesel3500]

Read an article in my local news paper just now. Three men working on a large electrical panel near a live open service panel were severely burned from an arc flash. One of the men has 2nd and 3rd degree burns over 90% of his body. Not sure if he is gonna live through it. Just makes me want to cry!!!

So, please please please everyone, wear personal protective equiment that is matched to the work you are doing. Be careful and stay safe!

 

[JohnE]

One of my guys had a 120/240V panel "blow up" on him. I wasn't there, but the description and results sure sound like a serious arc flash. I'll post a pic if I can ever get my camera to work properly. Very minor injury, but he was certainly fortunate.

Good reminder, RAM.

 

[hillbilly]

That makes me want to stay home today.
I saw a couple of big "bangs" back when I worked in industrial, although I've never been exposed to one..
Mostly in 480V and 575V gear. Back then (25+ years), nobody (mostly maintenence electricians) wore adequate protection when working "hot" in the (over 100) industrial plants where I was installing new OEM textile equipment. After I saw (mostly heard) the first 480 panel explode....it opened my eyes. I've been forever careful after that.
It's scary as H***. You never forget it.
Lukily no-one that I've known was ever seriously injured by arc-flash.
So Yes, be careful. You only get one "screw-up" unless you're very lucky.
steve

 

[bphgravity]

Can you post a link to news article? Does the article indicate why live work was being performed?

 

[zog]

Here is a pic of a nomex coverall worn by one of our guys involved in a arc flash from 480V, the material did break open, but he was not burned, the coveralls saved him from serious burns (Or worse).

 

[tomP]

I too would like to read the story. I went to the News Hearld (I think that was it) but they require a subscription to read the story.
Anyway that we can get more info?
I'd like to use it as a safety talk for our people.

 

[macmikeman]

Byran, on another electrical site, one of the co workers spoke about the incident. It happened in a Wal-mart store. The Utility primary's enter the building and are transformed inside the building down to customer voltage and the service is located inside the building. The workers were working on live equipment at voltage above 13,000 volts. They were pulling new cable next to live equipment. The whole fiasco sounded like it could have been easy to avoid if proper safety precautions were taken, and if the utility power was cut off in order to perform the installation, but management decided they could not afford down time. With 13,000 volts I wonder if even the full space suit would have helped at all. Hope these guys recover from the injurys soon.

 

[MJJBEE]

With 13,000 volts I wonder if even the full space suit would have helped at all. Hope these guys recover from the injuries soon.

I just wanted to make a clarification on arc flash and what actually causes the danger. Voltage IS NOT a good indicator of the hazard. I would argue that the best indicator of how hazardous a system is the clearing time of the breakers and fuses. Sorry to pick on you but lately I have been at war with this idea while trying to educate our plant personnel. In some of our plants the 13.8 kV arc flash hazard is less then the 480 V hazard. As always everyone please be safe and do think about arc flash before you do live work at any voltage level.

 

[don_resqcapt19]

So, please please please everyone, wear personal protective equiment that is matched to the work you are doing.

I don't think this is the correct message. The message should be don't work it hot. The cases where OSHA and NFPA 70E permit hot work are rare. Of course, until you have proved it is locked out and dead, you must have the correct PPE...even just to check for voltage.
Don

 

[realolman]

.... The cases where OSHA and NFPA 70E permit hot work are rare.... Don

So what's going to happen now? What kind of penalties will be levied to the contractor and / or to Wal-Mart?

 

[ramdiesel3500]

I don't think this is the correct message. The message should be don't work it hot. The cases where OSHA and NFPA 70E permit hot work are rare. Of course, until you have proved it is locked out and dead, you must have the correct PPE...even just to check for voltage.
Don

YES!!! Absolutely!! Thanks for the clarification. What I meant to say was, If you positively cannot avoid working on live equipment, then be sure to wear the correct PPE.

I cannot post the article as I read it in hard copy. Real sad day. Article said one of the workers was sent to Riley Hospital. Indicates to me that he was a minor. NOT GOOD!

 

[ramsy]

Of course, until you have proved it is locked out and dead, you must have the correct PPE...even just to check for voltage.

Does that usually inclulde 208 and 240vac panels?

The cases where OSHA and NFPA 70E permit hot work are rare.

Does anyone know off hand what those exceptions are?

 

[jim dungar]

OSHA does not determine the exceptions, neither does NFPA 70E.

The employer's Electrical Safe Work Practices (ESWP) need to outline the requirements for "live" work. After an incident it would be up to the employer to justify why they thought an exception was acceptable.

After all of the studies I have done, I cannot recall a single incident where medium voltage systems (those above 600V) had a higher incident energy than the 480V equipment, except at utility connections.

 

[don_resqcapt19]

Jim,
OSHA says that you can only work hot for trouble shooting or if locking out the power will create a bigger hazard. I think that 70E says the same.
Don

 

[don_resqcapt19]

Roger,

Does that usually inclulde 208 and 240vac panels?

The absolute minimum PPE that would be required is 1000 volt rated gloves and tools, long sleeve non-melting clothes, hard hat and safety glasses. Additional PPE may be required based on an arc flash hazard study.
Don

 

[MJJBEE]

After all of the studies I have done, I cannot recall a single incident where medium voltage systems (those above 600V) had a higher incident energy than the 480V equipment, except at utility connections.

In my case the 13.8 was differentially protected while the 480 wasn't.

 

[jim dungar]

Don,
NFPA 70E has provisions for an employer's ESWP to make allowances for energized work. In fact, there is an example of a live work permit in the back of the NFPA 70E standard.

But the only time an employer will know if they have a valid exception will be after the "verdict is read". I can not think of an exception that I would want to defend in a court of law.

mjbee
Differential protection is very good.

The point I was trying to make is: in most common work locations arc flash incident energy is usually most severe at the areas with <=480V and low bolted fault currents.

edit: changed to less than or equal to 480V

 

[George Stolz]

Can you post a link to news article? Does the article indicate why live work was being performed?

Here is a neighboring town's story. I can't believe the local paper requires a subscription to read the news. :roll:

Here's another.
Here's another.

I hope they pull through it.

 

[NoVA Comms Power]

If those stories are accurate, the Wall Mart appears to have still been under construction and not yet even open.

It would be interesting to know if the EC was directed by the GC to "work hot" simply to maintain a construction schedule.

 

[kingpb]

Jim and MJJBEE are absolutely correct when they said that arc flash is often worse at lower voltages (480V). Arc Flash is time and current dependent. Protection at the lower voltages is typically lower speed, and many times the instantaneous function is disabled to provide better coordination, resulting in higher potential for arc flash. Medium voltage systems usually have faster relaying, and more complex protection systems.

I think their is a misperception that the PPE can be easily selected just by looking at NFPA 70E, but it can't. The values listed in the tables for different tasks are based on a certain amount of fault current, and specifc times. Each system will be different. Therefore the only apporach in my book is DO NOT WORK HOT! Owner's do not have the right to put people in Danger, and electrician's should not be willing to put themselves in peril to make a buck.

Systems that are worked hot, need a specifc plan, need to have a CURRENT arc flash analysis done, and proper PPE needs to be supplied by the OWNER. Owner's seem to not want to pay for the arc flash analysis, therefore workers should not be willing to work it hot.

There is no amount of money worth a life! Refuse to put yourselves at risk. The mindest of the industry/owners needs to change.