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 Post subject: Interaction?
PostPosted: Mon May 10, 2010 12:15 pm 
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Back to a forum favorite topic of "interaction". A question I hear a lot is opening a circuit breaker door to check something like a trip unit indication or breaker status.

The term interaction in the definition of arc flash hazard refers the user to the tables for examples of taks that could cause an arc flash hazard. What do y'all think about opening a breaker door but not operating or racking the breaker if there are no exposed live parts?

An example would be like opening the door on this DS breaker?

Is this "interaction"? Would PPE be required for this task?

I think this is one of those grey areas that could use clarification because it is a common task in many plants, my gut tells me no PPE would be required because you are not interacting in a way that may cause an arc flash hazard but would like to hear what others think.


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PostPosted: Mon May 10, 2010 12:47 pm 
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This one still gives me heart burn as well. There is the "common sense" interpretation and then there is a "run for the hills - legal" interpretation. I am inclined to think the line should be drawn at opening a door as you suggest.

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PostPosted: Mon May 10, 2010 12:47 pm 
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That is a very good question without an easy answer. From my personal experiences, in most cases I would agree that no PPE would be required. However, several years ago I was an industrial electrician. One night I was troubleshooting a lighting circuit when I thought that I saw a little puff of smoke coming from the transformer bank that fed the panel that I was looking in. I proceeded to remove the cover from one of the still energized transformers. As I eased the cover off, some grit that was inside shifted and the transformer blew up in my face! The arc blast knocked me back some 15 feet!

Ever since that incident, I always take extra precautions whether or not I am planning to "work" on a piece of equipment or just visually inspect.

By the way, that is the only time that my children have ever seen me without at least a moustache. (The arc flash/blast burned it all down to the skin)


Oh, and now I am an electrical engineering technician, and electrical instructor.


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PostPosted: Mon May 10, 2010 12:52 pm 
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Sparkytrician wrote:
That is a very good question without an easy answer. From my personal experiences, in most cases I would agree that no PPE would be required. However, several years ago I was an industrial electrician. One night I was troubleshooting a lighting circuit when I thought that I saw a little puff of smoke coming from the transformer bank that fed the panel that I was looking in. I proceeded to remove the cover from one of the still energized transformers. As I eased the cover off, some grit that was inside shifted and the transformer blew up in my face! The arc blast knocked me back some 15 feet!
.


Apples and oranges to my question, at least I think so. First you suspected there was a problem, second you are removing a cover to expose bare energized parts and have the risk of just what happened, happening, so to me that is no brainer, arc flash hazard and PPE required.


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PostPosted: Mon May 10, 2010 12:55 pm 
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[quote="Zog"]Apples and oranges to my question, at least I think so. /QUOTE]

Still quite a story. Glad the only casulaty was the moustache!

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PostPosted: Thu May 13, 2010 4:31 am 
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DB-25 outdoor cans

Hi guys. We have two substations with outdoor DB-25 "cans" fed from open 240 volt bus. There are multiple 500's per phase entering a weatherhead over each can, connected to the line side terminals. There is no transformer secondary breaker and transformer primary protection is an 80 E fuse (too large!).

When we had our arc flash study completed some months ago, it confirmed my suspicion that the potential arc flash energy present is over 100 cal/cm^2 so we don't allow switching or cover removal to reset the trip coils or observation of the solid state trip device cause of trip indication.

My hope is to replace this with a rebuilt DS switchgear with a DS secondary main breaker. This will limit arc flash energy into the feeder breakers to a safe level.

We have multiple substations that don't have secondary mains and have primary fuses. All are over "40 cal". It's a huge problem for us and we can't seem to adress it quickly enough.


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PostPosted: Thu May 13, 2010 5:46 am 
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tjgraf wrote:
My hope is to replace this with a rebuilt DS switchgear with a DS secondary main breaker. This will limit arc flash energy into the feeder breakers to a safe level.

We have multiple substations that don't have secondary mains and have primary fuses. All are over "40 cal". It's a huge problem for us and we can't seem to adress it quickly enough.


I have plenty of those and can build to suit. We see this problem often, usually in paper mills, for some reason they don't seem to have mains very often.


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PostPosted: Mon May 17, 2010 12:27 pm 
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i would have to say yes to the ppe! it would be like removeing the trim on a panelbord but the dead front is still on there is no shock hazard but the arc flash from mech. failer is still present


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PostPosted: Fri May 21, 2010 5:34 am 
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This is an iffy subject. Other things come to mind such as, opening an MCC 480V bucket to reset an overload or to test for voltages. There are no physical alterations being done, only inspection. I suppose you could shake some dust loose or accidently have your meter in current mode instead of voltage mode when measuring. I wish there was a more finite line drawn for these type of scenarios. Common sense is to don the ppe.


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PostPosted: Fri May 21, 2010 6:17 am 
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hastheknack wrote:
This is an iffy subject. Other things come to mind such as, opening an MCC 480V bucket to reset an overload or to test for voltages. There are no physical alterations being done, only inspection. I suppose you could shake some dust loose or accidently have your meter in current mode instead of voltage mode when measuring. I wish there was a more finite line drawn for these type of scenarios. Common sense is to don the ppe.


I think checking voltages or resetting an overload is pretty clear that it is an "Interaction" that may cause an arc flash. I am just asking about opening the door and not testing or operating anything.


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PostPosted: Fri May 21, 2010 8:29 am 
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I would say no ppe. There are two things that come to mind now that may change that though.
1. Are there any switches, meters, etc. mounted in the door that may have wires pull loose when opened
2. Now that the door is already opened and I see an overload etc. that needs to be reset am I now going to take the time to don ppe


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PostPosted: Fri May 21, 2010 9:42 am 
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SPETE wrote:
I would say no ppe. There are two things that come to mind now that may change that though.
1. Are there any switches, meters, etc. mounted in the door that may have wires pull loose when opened
2. Now that the door is already opened and I see an overload etc. that needs to be reset am I now going to take the time to don ppe


No, and no, to answer your question. The purpose of opening the door in my senario would be to attach a remote actuator, just a magnet that sticks to the metal breaker front panel. The breaker would be open or closed wirelessly from up to a couple hundred feet away.


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PostPosted: Fri May 21, 2010 10:32 am 
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Thanks for giving me some clarity on that. What about simply reseting a breaker or an overload with the door closed?


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PostPosted: Fri May 21, 2010 10:49 am 
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hastheknack wrote:
Thanks for giving me some clarity on that. What about simply reseting a breaker or an overload with the door closed?


That is "Interaction", listed task in the table.


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PostPosted: Fri May 21, 2010 12:54 pm 
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Zog wrote:
The purpose of opening the door in my senario would be to attach a remote actuator, just a magnet that sticks to the metal breaker front panel. The breaker would be open or closed wirelessly from up to a couple hundred feet away.


In that scenario, I would call it "working on energized electrical conductors and circuit parts", and refer to Table 130.7(C)(9).

Article 100 defines "working on (energized electrical conductors or circuit parts)" as Coming in contact with energized electrical conductors or circuit parts with the hands, feet, or other body parts, with tools, probes, or with test equipment, regardless of the personal protective equipment a person is wearing.


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PostPosted: Fri May 21, 2010 1:03 pm 
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Sparkytrician wrote:
In that scenario, I would call it "working on energized electrical conductors and circuit parts", and refer to Table 130.7(C)(9).

Article 100 defines "working on (energized electrical conductors or circuit parts)" as Coming in contact with energized electrical conductors or circuit parts with the hands, feet, or other body parts, with tools, probes, or with test equipment, regardless of the personal protective equipment a person is wearing.


What is energized is the photo I posted? There are no exposed energized parts taht anything could make contact with.

Here is a video shwoing my senario. http://www.youtube.com/user/CBSArcSafe#p/u/9/98on0dZbt_M


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PostPosted: Mon May 24, 2010 5:13 am 
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In the photo it appears that something is energized as I see a digital display illuminated. I cannot comment on the video at this time as my company blocks Youtube.

I figure that in the best case (depending on how you look at it), the line side terminals on that breaker are energized. Opening the door could (Low risk I admit) cause conductive grit to become dislodged and cause an arc flash/blast.

You asked for opinions in this scenario, I'm merely providing my opinion. I am not OSHA, therefor I cannot provide you with a formal interpretation. I am only stating how would handle a similar situation for the 120 maintenance electricians that look to me for guidance. Yes, I will err on the side of caution. Yes, it may be inconvienient, but explaining to family members that their loved one is hospitalized or worse is a far worse inconvienience in my opinion.


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PostPosted: Mon May 24, 2010 5:43 am 
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Sparkytrician wrote:
In the photo it appears that something is energized as I see a digital display illuminated. I cannot comment on the video at this time as my company blocks Youtube.


There are energized parts, just not exposed. There is no shock hazard, and it is not "working on energized electrical conductors and circuit parts", but the arc flash hazard is the question here.

Sparkytrician wrote:
I figure that in the best case (depending on how you look at it), the line side terminals on that breaker are energized. Opening the door could (Low risk I admit) cause conductive grit to become dislodged and cause an arc flash/blast.

You asked for opinions in this scenario, I'm merely providing my opinion. I am not OSHA, therefor I cannot provide you with a formal interpretation. I am only stating how would handle a similar situation for the 120 maintenance electricians that look to me for guidance. Yes, I will err on the side of caution. Yes, it may be inconvienient, but explaining to family members that their loved one is hospitalized or worse is a far worse inconvienience in my opinion.


My point is there is not a clear cut answer on this as an interaction that may cause an arc flash hazard and I am just looking for opinions. Thank you for yours, this comment (above) is the type of feedback I was asking for. In your position I think err on the side of caution is the right thing to do, until the 70E offers more clarity on this and similar tasks.

There will always be a hazard, just walking past a switcgear line up and doing nothing, there is a chance a rat could cause an arc flash, but the line needs to be drawn somewhere to figure out what "risk" is reasonable.


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PostPosted: Mon May 24, 2010 9:01 am 
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I could not agree more. :)


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PostPosted: Mon May 24, 2010 12:40 pm 
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In my opinion no interaction occurred until the breaker was operated, and that interaction stopped when the operation completed successfully. If you are collecting opinions, perhaps you want to set up a poll.


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