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 Post subject: Exposed or NOT???
PostPosted: Mon Mar 16, 2009 9:22 am 
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I'm sure this has been mentioned before, as it is a big issue. I couldn't find anything that would directly answer my questions. Maybe you guys could help. (brainfiller????)

Since NFPA likes to be vague on certain things, let me bring up few questions regarding "Exposed Live Parts."

Here are three different scenarios:

1. 480V MCC Rated at Arc Flash LVL 3 PPE when working on Energized Parts.

Pull the Disconnet - LVL 0 (according to NFPA 70E 2004 130.7(C)(9)(a) table)
Verify circuit is de-energized LVL 3.

Once verified, okay to perform work without PPE on? This is a debate considering only the top of the disconnect has live parts and you'd have to use something small like a screwdriver to get to it. Is there anything in OSHA, NFPA that says it is NOT okay to work without PPE or is this still LVL 3?

2. 4160V Switchgear with Arc Flash LVL 3 PPE when working on Energized Parts but with breaker REMOVED and shutters closed.

Since the shutters are closed, is it still LVL 3? Technically, since the shutters are closed, you do not have anything "exposed." What about control circuit (ex. 125V DC)?

3. 4160V Switchgear with Arc Flash LVL 3 PPE when working on Energized Parts but with breaker in service (or racked out for that matter).

When you open the cubicle, NO live parts are exposed unless you deliberately defy the safety mechanism. Is this still LVL 3, or no Arc Flash protection required.

HELP!!!!!!


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PostPosted: Mon Mar 16, 2009 10:39 am 
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Jnox wrote:
Here are three different scenarios:

1. 480V MCC Rated at Arc Flash LVL 3 PPE when working on Energized Parts

Pull the Disconnet - LVL 0 (according to NFPA 70E 2004 130.7(C)(9)(a) table)
Verify circuit is de-energized LVL 3.

Once verified, okay to perform work without PPE on? This is a debate considering only the top of the disconnect has live parts and you'd have to use something small like a screwdriver to get to it. Is there anything in OSHA, NFPA that says it is NOT okay to work without PPE or is this still LVL 3? .


You are still working withing the arc flash boundary of the live parts, even though you are not actually working on the live parts. My interpretation is that if you are withing the AFB then you still need the same PPE. I feel that this is overkill myself but the intent of the 70E is to eliminate any type of electrical work. I agree this is a grey area.

Jnox wrote:
2. 4160V Switchgear with Arc Flash LVL 3 PPE when working on Energized Parts but with breaker REMOVED and shutters closed.

Since the shutters are closed, is it still LVL 3? Technically, since the shutters are closed, you do not have anything "exposed." What about control circuit (ex. 125V DC)?


The arc flash hazard still exists, you are interacting with the equipment and the hazard is still there. Working on control circuits in that cubicle could cause another breaker to trip or close and intiate an arc, I wouldnt want to be in a cell when that happens, shutter or no shutters. However, you can argue that you can use reduced PPE per the tables (HRC 2 in this senario), that jives with the HRC 2 requirement for operating the breaker with the door closed. Are you using the tables or have you done an analysis?

Jnox wrote:
3. 4160V Switchgear with Arc Flash LVL 3 PPE when working on Energized Parts but with breaker in service (or racked out for that matter).

When you open the cubicle, NO live parts are exposed unless you deliberately defy the safety mechanism. Is this still LVL 3, or no Arc Flash protection required.


That breaker has nothing to do with the arc flash hazard in that cubicle, it is the upstream breaker (or fuses) that determine the hazard level, so still HRC 3 if that is you calulated value, in fact it may be higher, chances you arc flash analysis assumeed a working distance greater than where you would be working when in the cubicle, so the Ei may be even higher than your label.


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PostPosted: Mon Mar 16, 2009 11:05 am 
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I'm confused about question 3. How do you work on energized parts without exposing them? Can you be specific about the nature of the task you have in mind?


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PostPosted: Mon Mar 16, 2009 11:08 am 
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Zog wrote:
You are still working withing the arc flash boundary of the live parts, even though you are not actually working on the live parts. My interpretation is that if you are withing the AFB then you still need the same PPE. I feel that this is overkill myself but the intent of the 70E is to eliminate any type of electrical work. I agree this is a grey area.


That's a good point. Looking at the table provided it tells you can pull the disconnect with LVL 0 PPE. When you do that, you are also within AFB. At the location where I work, it will be very difficult to convince people it is a shock hazard. If we interpret this as a safe enough situation, will it violate any regulations, or is it completely up to us?


Zog wrote:
The arc flash hazard still exists, you are interacting with the equipment and the hazard is still there. Working on control circuits in that cubicle could cause another breaker to trip or close and intiate an arc, I wouldnt want to be in a cell when that happens, shutter or no shutters. However, you can argue that you can use reduced PPE per the tables (HRC 2 in this senario), that jives with the HRC 2 requirement for operating the breaker with the door closed. Are you using the tables or have you done an analysis?


I have performed the analysis. Not completely done, but for the most part I am. Since I have performed an analysis, can I still fall back on the table in NFPA?

I am assuming, to perform work inside that cubicle, we need to kill the main to that switchgear?

Zog wrote:
That breaker has nothing to do with the arc flash hazard in that cubicle, it is the upstream breaker (or fuses) that determine the hazard level, so still HRC 3 if that is you calulated value, in fact it may be higher, chances you arc flash analysis assumeed a working distance greater than where you would be working when in the cubicle, so the Ei may be even higher than your label.


For this particular switchgear, I have calculated Main incoming breaker as DANGEROUS. The rest of cubicles came out to be LVL 3. Since in this situation, the fault would be compartmentalized, that is the way I will label each cubicle. I guess my question was, if I just open the door to look inside the 4160 switchgear, even though there are no "directly" live parts, I still need to have PPE on? I think I have an idea what the answer will be to this one ;) .

All of this makes sense, but then it also doesn't demanding on the situation. The hard part is convincing people this is the way it's supposed to be given you can't say "it's the law" since NFPA is very vague on this subject. What a pain in the arse.

Good comments, keep them coming people!


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PostPosted: Mon Mar 16, 2009 11:11 am 
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stevenal wrote:
I'm confused about question 3. How do you work on energized parts without exposing them? Can you be specific about the nature of the task you have in mind?


I should probably rewrite the question. Essentially, what I'd like to know is, when you just want to peek inside the cubicle, do you need PPE on?

Most of the MV/HV switchgear, when you open it up, there is no LIVE parts directly exposed. It is all in the back of the switchgear. I have been asked, if this is the case, why need for PPE since you will not work on any live parts?


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PostPosted: Mon Mar 16, 2009 11:33 am 
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Jnox wrote:
That's a good point. Looking at the table provided it tells you can pull the disconnect with LVL 0 PPE. When you do that, you are also within AFB. At the location where I work, it will be very difficult to convince people it is a shock hazard. If we interpret this as a safe enough situation, will it violate any regulations, or is it completely up to us?


The shock hazard exists (Per 70E) if you are working within the LAB of exposed live parts, regardless of "what" you are "working" on.


Jnox wrote:
I have performed the analysis. Not completely done, but for the most part I am. Since I have performed an analysis, can I still fall back on the table in NFPA?


The 2009 70E has verbage that strongly advising against mixing the use of your calcs and the tables. Once you have doen the calcs you have aknowledged the hazard level and to reduce PPE vis the tables would put you in a tough situation with OSHA should an accident occur. Remmember the tables are more or less "gut" feels of the 70E commitee and you analysis represents the real hazard more accuratly than the tables do.

Jnox wrote:
I am assuming, to perform work inside that cubicle, we need to kill the main to that switchgear?


Good question, as a person that spends a lot of time doing exactly the same thing, I always try to de-energize if possible. Is this as hardous as working on the 4160V, yes and no.

Yes, the some potential arc energy is there, even if it may be partially absorbed by the enclosure, but then again the pressures will build up more in an enclosed environment and can be higher than if the arc was in open air, IEEE 1584 is doing research as we speak on pressures, our host here is involved and has posted some of that info on this forum.

No, even though the hazard is the same (Or maybe worse) the risk is reduced, less chance of initiating an arc.


Jnox wrote:

For this particular switchgear, I have calculated Main incoming breaker as DANGEROUS. The rest of cubicles came out to be LVL 3. Since in this situation, the fault would be compartmentalized, that is the way I will label each cubicle. I guess my question was, if I just open the door to look inside the 4160 switchgear, even though there are no "directly" live parts, I still need to have PPE on? I think I have an idea what the answer will be to this one ;) .

All of this makes sense, but then it also doesn't demanding on the situation. The hard part is convincing people this is the way it's supposed to be given you can't say "it's the law" since NFPA is very vague on this subject.



Agreed, but the "law", and by that I mean OSHA, will look at your study results and question why PPE wasnt worn when the hazard was calculated and acknowledged. Sorry I cant give you anything more solid, sounds like you have a good understanding on the subject, do what you feel is right.


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PostPosted: Mon Mar 16, 2009 11:34 am 
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Jnox wrote:
At the location where I work, it will be very difficult to convince people it is a shock hazard.


It's not a shock hazard, but it still is an arc flash hazard, hence your lookup in the table and the usage of arc flash rated PPE.

Jnox wrote:
I have performed the analysis. Not completely done, but for the most part I am. Since I have performed an analysis, can I still fall back on the table in NFPA?


From NFPA 70E 2009, 130.3 Exception No. 2:
Quote:
The requirements of 130.7(C)(9), 130.7(C)(10), and 130.7(C)(11) shall be permitted to be used in lieu of a detailed incident energy analysis.


My understanding is that you can use the tables (watch for the notes), but if you actually do a detailed incident energy analysis, then you can't go back to the tables (especially if the tables allow you to use a lighter PPE than your detailed analysis).

Now, for another equipment, one for which nobody did a detailed incident energy analysis yet, then the tables are good to go (again, watch the notes).

"But the tables don't have the same PPE requirement for different tasks on the same equipment, while a detailed incident energy tells me to wear the same thing for a specified working distance!"

Short answer: Yes, it's true.


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PostPosted: Mon Mar 16, 2009 11:36 am 
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Jnox wrote:
I should probably rewrite the question. Essentially, what I'd like to know is, when you just want to peek inside the cubicle, do you need PPE on?

Most of the MV/HV switchgear, when you open it up, there is no LIVE parts directly exposed. It is all in the back of the switchgear. I have been asked, if this is the case, why need for PPE since you will not work on any live parts?


No exposed live parts here either, would you have wanted to be in front of this switch?


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PostPosted: Wed May 06, 2009 8:00 pm 
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Zog wrote:
No exposed live parts here either, would you have wanted to be in front of this switch?


There looks to have been exposed energized parts in that switch and we do not know what triggered the event.

In general we do not require arc flash ppe to look inside switchgear, providing it is a 'look' and not 'touch' and there is nothing that might disturb the electrical field. That is 'in general' but there are also conditions such as excess spider webs, rusty or loose switchgear componentes where merely opening the door might constitute disturbing the electrical field.


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PostPosted: Thu May 07, 2009 7:06 am 
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Gary B wrote:
There looks to have been exposed energized parts in that switch and we do not know what triggered the event.

In general we do not require arc flash ppe to look inside switchgear, providing it is a 'look' and not 'touch' and there is nothing that might disturb the electrical field. That is 'in general' but there are also conditions such as excess spider webs, rusty or loose switchgear componentes where merely opening the door might constitute disturbing the electrical field.


The 70E tables now have reduced PPE requirements for visual inspections, but you still need PPE to do so.


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PostPosted: Tue Jun 02, 2009 2:41 pm 
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Jnox wrote:
I should probably rewrite the question. Essentially, what I'd like to know is, when you just want to peek inside the cubicle, do you need PPE on?

Most of the MV/HV switchgear, when you open it up, there is no LIVE parts directly exposed. It is all in the back of the switchgear. I have been asked, if this is the case, why need for PPE since you will not work on any live parts?


I was waiting for this one. Kind of like peeking inside of a bomb to see if it is armed.

What about the next guy who just wants to peek inside and it turns out to be a tie breaker cabinet with 15 kv on the top and bottom. Breakers is off but is there any voltage inside the cabinet. You tell me.

The rules are written to try and protect people from themselves. Of course if we do away with OSHA and NFPA then the problem eventually becomes self correcting.


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