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 Post subject: Restricted Approach Boundary
PostPosted: Sun Jan 20, 2008 7:52 pm 
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Can someone explain what the Restricted Approach Boundary is trying to obtain and how it differs from the Prohibited Approach Boundary.


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PostPosted: Tue Jan 22, 2008 6:17 pm 
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Depends on the voltage class of the equipment...

For all 600VAC Class equipment, the Approach Boundaries are the same.

Limited Approach Boundary~ 42 inches

Restricted Approach Boundary~ 12 inches

Prohibited Approach Boundary~ 1 inch.

They are defined in Article 100 of the NFPA 70E, but the quick and dirty is this, Limited Approach Boundary is the furthest away, at 42 inches, and special precautions must be taken. Restricted is closer, and the risk of arc-over due to inadvertent contact is increased. The biggie, the thing that makes Prohibited PROHIBITED is that it is considered the same as working on the live part. That is straight out of the 70E Article 100. These levels are different at higher voltages, but I suspect you needed these.


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PostPosted: Tue Jan 22, 2008 9:02 pm 
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I got the basic definitions, but I don't understand how there is a difference in the Restricted and Prohibited. Would there be a difference in PPE. Prohibited is the same as touching a live bus, so you would need gloves. But if you are in the Restricted and say doing a voltage test, you would not need gloves - but guess only if you had 12" probes. Can you give some examples of work where these boundaries would have different PPE requirements.


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PostPosted: Wed Jan 23, 2008 6:03 am 
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Which PPE?

Are you referring to Shock Hazard PPE or Arc Flash PPE? Arc flash PPE is required when you're inside the flash protection boundary, no matter what task you are performing. The difference between restricted and prohibited in terms of shock hazard would be whether you are making contact or not making contact with the energized part. Voltage measurements are considered working on as opposed to working near. If you're working on energized parts, voltage rated gloves and voltage rated tools are required. The best examples I can think of for the difference between restricted and prohibited approach are exposing an energized part by removing a cover, in which case you are inside the restricted approach boundary, and a voltage or current mesurement, where you are within the 1 inch prohibited approach boundary and/or making contact with the energized part. Obviously your measurement device would be voltage rated, as should your gloves. Because you are also inside the flash protection boundary and the equipment is obviously energized and exposed, your voltage rated gloves would need to be covered by protective leather gloves, since your outermost layer must be FR rated if you are within the flash protection boundary.


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PostPosted: Wed Jan 23, 2008 9:35 pm 
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YES, Shock Hazard boundaries.
I guess I am having trouble in the sense that on 480V systems the Restricted boundary is 12". So if you are removing a panel cover or opening an MCC bucket, as you lift the cover off or swing the bucket door open, you probably have your exposed hands within 12" of live parts, so are you really wearing gloves to do this task. I suppose a suitably attired person who is just observing another electrician could be 12" away, but that's about all I can think of. I'm trying to think of real world tasks that exposure is more than 12".


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PostPosted: Fri Jan 25, 2008 8:32 am 
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Yes to gloves

If one is to follow the letter of the law, so to speak, of the 70E and for that matter 29CFR1910.132, then yes, when removing the deadfront from a panel one should wear volatge rated gloves. Again, because the flash protection boundary is probably greater than 12 inches, one would need to have leather protective gloves over the voltage rated gloves.

What is important to remember when rendering equipment "exposed" is whether or not removing a panel cover actually exposes any energized components. It is possible, depending on the configuration of a panel or other device, to remove the oustide cover and the energized components still not be "exposed" as defined by Article 100. A "deadfront" is the last cover over an energized component, whether that be a cover, a non-conductive shield or barrier, or some other material. Just because the outer most cover of a device is removed doesn't necessarily mean that it's "exposed".


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PostPosted: Mon Feb 18, 2008 7:38 pm 
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Still have trouble. To me, there is no difference between the Prohibited and Limited. Once you are past the Limited, you need full shock protection, ie, gloves and tools. How is that different than Prohibited. I get the example about the panelboard, but even if you are more than 12" from the bus, I doubt you would be 12" away from the load side of energized breakers. There is not going to be many, if any, at 480V that energized parts will be 12" from covers and doors. If the PPE requirement is the same for both boundary, why not drop the Limited and just make the Prohibited 12".


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PostPosted: Mon Feb 18, 2008 8:09 pm 
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haze 10

As to your last response. Shock protection is required when crossing the Restricted not Limited Approach. The Shock protection needed when crossing the Restricted Approach can be met with gloves, and sleeves if necessary as they relate only to the parts being worked on. Prohibited Approach requires all parts of the body to be insulated. My take on this is the " it jumped out and grabbed me " scenario which can occur under the right conditions at increasing distances as the voltage increases. This is my interpetation on it, although I find it hard to think of an instance where it would realistically apply under 600 volts.


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PostPosted: Mon Feb 18, 2008 9:08 pm 
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I am Confused

Sparky wrote:
haze 10

As to your last response. Shock protection is required when crossing the Restricted not Limited Approach. The Shock protection needed when crossing the Restricted Approach can be met with gloves, and sleeves if necessary as they relate only to the parts being worked on. Prohibited Approach requires all parts of the body to be insulated. My take on this is the " it jumped out and grabbed me " scenario which can occur under the right conditions at increasing distances as the voltage increases. This is my interpetation on it, although I find it hard to think of an instance where it would realistically apply under 600 volts.


Sparky,

First off, I do not understand how one could function with all parts of the body insulated, except if you were on or in some sort of insulating platform....do you mean arc flash protected?....Please clarify this for me.

Also, I do not understand the jumped out and grabbed me case as distance and voltage increases. I cannot realistically think of it "OVER" 600 volts.....and I have worked as high as 115 kV live and never had it come to get me. I always had to go get it. After all, dry and non-ionized air has no less than 10 kV per inch for dielectric strength and most often a lot more than that.

Maybe you are thinking about the "static" electricity created from the electric field?

Please explain what I am missing,
Alan


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PostPosted: Tue Feb 19, 2008 12:59 pm 
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Sorry, it was late when I typed that. I obviously meant to restrict (no pun intended) the conversation to a comparison between the "PROHIBITED" and the 'RESTRICTED" boundaries.

I am trying to understand how there is a practical difference.

The comment about fully insulating your entire body, I don't believe that to be correct. It might mean adding arm protection in addition to gloves, but I know of no rubber suit that covers the whole body.

The definitions in NFPA70E are vague. I am trying to understand what is actually trying to be achieved. These are shock protection boundaries, so if there is no differences in PPE than why create two boundaries.


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PostPosted: Tue Feb 19, 2008 3:12 pm 
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Sorry for the confusion. My reply was supposed to state " any part of the body that crosses the Prohibited Approach Boundary must be insulated. I did not mean to infer entire body. My apologies. As for the jump out and grab me scenario I mentioned, I can not, and would not attempt to support this theory with facts. What I can support it with, is a co-worker that defeated the fail safes to perform testing, came within 4 inches of exposed 4160 bus, grabbed onto a grounded cubicle without insulated gloves, and due to the high humidity and obviously high moisture content in his body suffered a shock that entered his forehead and exited his hand. Luckily survived.

Back to the issue at hand, I believe the intent was to indicate a need for raised awareness of the danger of close proximity.


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PostPosted: Tue Feb 19, 2008 4:23 pm 
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Yes, awareness, but it doesn't say that. It basically says that you need the same PPE for shock protection. I mean are we say that if you gloved hand has 10" of glove, and you work withing a 1/4" of the live part, that you now need 'arm chaps' to the shoulder because the 2" of exposed hand is past the Restricted boundry.

All the other boundaries are easy to understand. But I still don't see a difference between the Prohibited and the Restricted that creates a clear distinction of what is right and wrong.


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PostPosted: Mon Jun 02, 2008 1:44 pm 
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There are no difference in PPE requirements, but in order to cross the PAB you need specified training (Live bare hand work training linemen get) and perform a risk analysis. 99.9% of the workers dont have this training so essentially no one should ever cross the PAB.

The PAB for 480V is 1", keep your hands above the gaurds on your test probes and you are all good. You think it is a coinicdence the gfinger gaurds and PAB are the same distance?


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PostPosted: Thu Jun 12, 2008 5:58 pm 
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Limited, Restricted and Prohibited have nothing to do with Arc Flash
These are shock hazard boundaries only.
Limited is to keep unqualified away from a shock hazard.
Restricted is to keep Qualified away from a shock hazard
Prohibited of course is the same as making contact. This also means if your tools
cross the boundary.
Limited...risk of shock
Restricted.... increased risk of shock


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PostPosted: Fri Jun 13, 2008 6:30 am 
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Is the PPE required for shock hazard boundaries based off of the results of PPE found for flash hazards? If not, how is shock hazard PPE structured?


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PostPosted: Wed Nov 10, 2010 2:25 pm 
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I'm with Haze - I don't see a difference between restricted and prohibited.

And I don't get ZOg's comment about bare hand work. Are you saying that even with voltage rated gloves, one should not touch (or encroach within 1" for 480V) an exposed, energized conductor ?


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PostPosted: Tue Nov 16, 2010 4:48 am 
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Barrusr wrote:
I'm with Haze - I don't see a difference between restricted and prohibited.

And I don't get ZOg's comment about bare hand work. Are you saying that even with voltage rated gloves, one should not touch (or encroach within 1" for 480V) an exposed, energized conductor ?


RESTRICTED is the area within, which a QUALIFIED electrical worker can enter, to work on a specific piece of equipment under the conditions outlined in 70E.

While working within the RESTRICTED area, the QUALIFIED electrical worker can not cross the PROHIBITED barrier. As doing so is the equivalent of working live; which requires specialized training, risk analysis, etc.


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PostPosted: Tue Nov 16, 2010 7:44 am 
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Look at it this way - with some exceptions (See NFPA 70E130.2(C)):

If you are qualified, you can get to within 1 foot (Restricted Approach) of bare energized 480 volt conductors. You need to wear rubber gloves to get closer than 1 foot, and if you do, you can't get your uninsulated elbow (or nose or any other uninsulated body part) any closer than 1 inch (Prohibited Approach) from the conductor.

Personally, I wouldn't get my uninsulated nose any closer than 1 foot. :o


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PostPosted: Tue Nov 16, 2010 10:50 am 
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Here's my 1.3 cents ...
Because crossing the Prohibited boundary is considered the same as making contact, and therefore you would be considered to be working on energized electrical conductors, in order to cross it you not only need all of the PPE, but also an Energized Work Permit.
See 130.1(B)(1).


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PostPosted: Thu Mar 31, 2011 1:07 pm 
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130.2(C) No qualified person shall approach or take any conductive object closer... than the RAB unless
(1) QP is insulated or guarded from energized conductors


You need the gloves before you get to the PAB.

110.7(F) electrical safety program shall identify a hazard/risk evaluation procedure to be used before work is started within the LAB...

You need a risk analysis before you get to the PAB

130.1(B) Work performed within the LAB... by qualified persons related to [certain tasks] shall be permitted to be performed without an EWP.

Wording seems to imply a EWP is required to cross LAB, again, well before you reach the PAB.

seems jghrist and I are seeing the same thing. I guess I don't see the need to mandate insulation at 1" when it is already required at 12". I think they are trying to mandate blankets on nearby energized parts not being worked on, but doing a poor job of it. Prolly only applicable to lineman w/multiple voltages on a pole, but if someone can think of a 480V scenario, I'd love to hear it.


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