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What PPE do you use to operate a breaker labeled Cat. 3
Minimum Category 3 PPE.
We permit reduced PPE since the covers are on.
No PPE is required.
You may select 1 option

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 Post subject: PPE With Covers ON
PostPosted: Sun Mar 20, 2011 5:27 pm 
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This week’s question was submitted by one of the Arc Flash Forum users. It is a variation of the arc flash hazard/interaction question and protection from doors question.

What PPE do you use to operate a breaker labeled Category 3 with the equipment covers on?

  • Minimum Category 3 PPE.
  • We permit reduced PPE since the covers are on.
  • No PPE is required.


Feel free to post your comments and thoughts.

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PostPosted: Mon Mar 21, 2011 2:29 pm 
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No simple answer.

Our company's policy is "Class 0" PPE for routine operation of properly maintained and applied devices, where no 'electrical work' has been done when the device is in the open position. In this case, full "Class 3" PPE would be required if the breaker was being reset after an event or if some type of work had been done (i.e. a motor change out).


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PostPosted: Tue Mar 22, 2011 5:42 am 
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This is just a thought, but rather than hash up the same thread, maybe what this question should be asking is, 'what is the NFPA Art 130 interpretation for performing switching operations on deadfront equipment'. There is a lot of 'personal' practices that are injected, and while informative as to what others are doing, I would think the starting point would be - what does the Art 130 text say... then one is free to add 'more'.


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PostPosted: Tue Mar 22, 2011 8:22 am 
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A pole for next week

might be "what does the Art 130 text say" because haze10 has a valid point. My answer as a lot of you know is we wear the CAT. 3 no matter what. I'm NOT saying that is how it should be but that is what we do.


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PostPosted: Tue Mar 22, 2011 12:00 pm 

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This is the topic that drew me to this forum. I've checked out the threads about it and I don't feel so bad about being confused.

I understand Haze10's point of view, but I have some close friends that are lawyers and I know how their vulture minds work. Therefore, I'm in the "PPE according to label" camp.


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PostPosted: Thu Mar 24, 2011 6:13 am 
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This week's question was given to me by one of the forum members. I know the topic has been discussed from various angles in the past. It is interesting to see how the results are stacking up when given the three options.

I appreciate everyone's comments!

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PostPosted: Thu Mar 24, 2011 7:37 am 
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100questions wrote:
might be "what does the Art 130 text say" because haze10 has a valid point. My answer as a lot of you know is we wear the CAT. 3 no matter what. I'm NOT saying that is how it should be but that is what we do.

As discussed many times in this forum the requirements for this question can be interpreted different ways, what this poll question shows is how many people interpret the requirements. We all know what 70E says (Article 130 is just part of the standard needed to answer this question).


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PostPosted: Thu Mar 24, 2011 8:18 am 

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This is another case where interpretation of rules and sound engineering judgment might collide. My position is this: We follow standards and procedures for a very good reason. But we have to remember they are a means to an end, not an end in themselves. Rigorous engineering and good judgment still have final say.

Correct interpretation of a standard MIGHT shield you from liability, the absence of injury WILL shield you from liability. Wearing Cat 3 PPE in this situation is not a bad idea. However, the actual installation might be such that a lower category PPE is safe.

So this begs the question, "Why take chances? Why not just require Cat 3?"
My answer is this: "When an electrician in the field (and I spent many years as one) comes to the conclusion that a rule is being imposed by someone higher up the chain just to cover himself, you lose confidence and you feel you have a reason not to comply with the rule(s). This tends to snowball.

Bob Ragsdale P.E.


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PostPosted: Thu Mar 24, 2011 1:51 pm 
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From another thread regarding FRC clothing, we know that the ratings aren't all they are thought to be. The ANSI test says that the value on the label only represents a 50% probability of transferring less than 1.2 cals to the wearer. So how do you include that into the liability discussion. Following the logic that liability must be brought to its lowest value, then Level 3 isn't enough. We need to go to Level 4 to take it to less than 5% chance of injury by burn.

...Oh, but the covers? How much reduction are we crediting to the covers?


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PostPosted: Fri Mar 25, 2011 8:11 am 
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haze10 wrote:
...Oh, but the covers? How much reduction are we crediting to the covers?


I credit no reduction to the covers.


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PostPosted: Fri Mar 25, 2011 8:19 am 

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Covers can make a pretty impressive projectile. :eek:


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PostPosted: Fri Mar 25, 2011 9:41 am 

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C. Marsh wrote:
Covers can make a pretty impressive projectile. :eek:


Indeed they can. And PPE provides no protection for this. So the engineer has to decide how to operate this considering there is no safe PPE for this task. If you are operating a DS type breaker you can purchase a "Chicken Switch" and operate it from 30 feet away. But what about that 200A KA frame in an I-Line panel with 22 cal/cm^2?

This is one of the facets of Arc Flash where trying to establish policies becomes rather difficult because arguments tend to spin out of control. None the less, our goal is NO injuries. At some point, as engineers we have to figure out how to get the job done safely and be willing to take responsibility for these decesions. My approach has always been to evaluate each situation and make the best decesion possible. I avoid blanket solutions.

Bob Ragsdale P.E.


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PostPosted: Fri Mar 25, 2011 11:06 am 
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BCR_1962 wrote:
Indeed they can. And PPE provides no protection for this. So the engineer has to decide how to operate this considering there is no safe PPE for this task. If you are operating a DS type breaker you can purchase a "Chicken Switch" and operate it from 30 feet away. But what about that 200A KA frame in an I-Line panel with 22 cal/cm^2?
You can get remote operators for those too.
BCR_1962 wrote:
This is one of the facets of Arc Flash where trying to establish policies becomes rather difficult because arguments tend to spin out of control. None the less, our goal is NO injuries. At some point, as engineers we have to figure out how to get the job done safely and be willing to take responsibility for these decesions. My approach has always been to evaluate each situation and make the best decesion possible. I avoid blanket solutions.

Bob Ragsdale P.E.
I agree with your reasoning however there is something to be said for keeping things simple. Having a panel covered with different labels for each possible task and different PPE requirements can be confusing. Most people that will work on that equipment do not have the same understanding of the factors invloved and how to adjust for them as an engineer that does the analysis.


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PostPosted: Tue Apr 03, 2012 1:50 pm 
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I give Arc Flash training weekly across the nation and this question comes up in almost every class. I am now, after hearing story after story of arc flash events at local facilities WITH doors closed, all for wearing PPE at the calculated level while performing switching operations. Students have brought up multiple times the seemingly flimsiness of newer gear and although I have not done the research to verify wall-thickness of newer gear with older models, I have seen newer gear when I was doing installs that seem to bend easier than stuff made in the 70s and 80s. I have multilple pictures of arc flash events with the "bolted covers" laying on the floor with locks attached, along with the breaker remains laying beside the cover on the floor. When an arcing event happens, I certainly would want to be in the calculated level of PPE in the hopes of avoiding burns and that is what I recommend to my students. When it comes to burns, having been a firefighter for over 15 years, I say better safe than sorry.


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PostPosted: Tue Apr 03, 2012 4:59 pm 
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The ANSI test says that the value on the label only represents a 50% probability of transferring less than 1.2 cals to the wearer. So how do you include that into the liability discussion. Following the logic that liability must be brought to its lowest value, then Level 3 isn't enough. We need to go to Level 4 to take it to less than 5% chance of injury by burn.

I beg to differ. That is not what the ASTM (not ANSI) test measures. It measures the CLOTH and it does it over the entire time period (Stoll curve). The cloth is mounted perpendicular to the arcing source. Pretty much any undergarments or body position that places you at any angle other than right in front of the arcing source reduces it. Now the idea of going from cat 3 to cat 4 to reduce the risk is a waste of time. Take a look at the actual ASTM curve results. Every clothing manufacturer has the actual test report that they get from Kinectrics and many are published on the internet. It is very clear from examining the report that once you get about 0.5 to 1 cal/cm^2 over the predicted 50% threshold, the results all pass (go to zero). The statistical curve that the standard uses suggests that there is still some risk but the results in every case that I've examined show that the curve that is used in the statistical analysis is way too shallow to represent the real world.

The test does not do any good against projectiles and the test does not test the results against plasma, which can be a much greater concern, depending on the nature of the arc (but no research so far). In these cases, increasing PPE may or may NOT have the intended effect because the test is only against radiative heat, not other effects caused by arcing faults.

IEEE 1584 by the way predicts the incident energy at a point. The working distances are intended to protect against the face/chest area where a burn of roughly 10% of total surface area can be fatal. There is no guarantee that other parts of the body which are not being modeled will fare so well...some are likely to be unscathed in a worst case scenario, others not so well. The intended effect of IEEE 1584 is to ensure survival, not to ensure minimal injuries.

OK...my answer to the question is that currently my employer requires CAT 4 for all switching operations where I work but most of the other plants require either CAT 0 or 2 (most common is 2 for switching operations). It is pretty clear when you read the tables and make the assumption that the Technical Committee intends switching to be "normal operation" of the equipment that they intend that arc flashes are pretty rare events and thus no reason to need PPE. However as mentioned earlier, this gets into everyone's "feelings" about the subject. As I've advocated before, we need to switch to looking at it objectively from a "what's the likelihood" scenario using measured data that is already out there.

The reasoning by the way is at the site I'm at, they've had their fair share of failed breakers have a major arcing fault (and thus injuries) in the past but so far there is flat out refusal to follow the Article 200 recommendations in terms of maintenance of the equipment...so they are reacting to the idea that the equipment is probably not under "normal operation". I generated a spreadsheet/chart showing what happens if we assume the breakers fail and jack the fault clearing times up to 2 seconds across the board for breakers (I left fuses out of it)...all of a sudden, a H/RC 4 suit doesn't look so safe any more. The other reason is because of the same knee-jerk response that IEEE 1584 predicts the threshold and we should give ourselves a comfortable safety margin...but as I just stated, it is NOT safer. And the margin is not just "1 category"...it's more like 0.5-1 cal/cm^2. More interestingly data mining (when you have 1200 buses to work with), shows that only about 4% of them are in the threshold region of 0.5-1 cal/cm^2 of the "limit of the PPE", the PPE we buy already has some margin built in (Salisbury stuff is not exactly rating 8 cal ATPV or 40 cal ATPV), and that when you factor in phase angle (SKM looks at maximum assymetrical current), you drop by at least 1 cal/cm^2 89% of the time just due to phase angle alone.

The others are taking NPFA 70E's recommendations into account and either going for a "simple" rating of CAT 2 across the board or using a combination of 0 and 2. We have lots of medium voltage equipment so the CAT 2 stuff is very common.


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PostPosted: Wed Apr 04, 2012 7:23 am 
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Projectiles are not necessarily effects of arc flash incident energy.

High incident energy, the ability to burn, may have absolutely no direct relationship to arc-blast, the ability to create projectiles. High fault currents do have the 'explosive' ability to create projectiles, but often have low incident energy because the fault is cleared quickly.


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PostPosted: Mon Apr 09, 2012 9:39 am 
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So the next question is at what pressure [blast pressure] does
[SIZE=3][font=arial]The panel board covers / breaker cubicles when properly closed; latched; secured become potential projectiles? Has IEEE done any test with the covers / doors closed and latched to determine at what pressure the can become removed from their secure state?[/font][/size]


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PostPosted: Mon Jul 02, 2012 10:11 am 

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mike01 wrote:
So the next question is at what pressure [blast pressure] does
[SIZE=3][font=arial]The panel board covers / breaker cubicles when properly closed; latched; secured become potential projectiles? Has IEEE done any test with the covers / doors closed and latched to determine at what pressure the can become removed from their secure state?[/font][/size]


The most commonly referenced standard for arc-resistance is ANSI/IEEE C37.20.7-2007. ANSI C37.20.7 was first issued in 2001, and revised in 2007. However, it applies to switchgear, not panelboards, switchboards, or MCCs, which usually will fall under a UL standard. I don't think anything exists yet for those equipment types.


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PostPosted: Thu Jul 12, 2012 7:54 am 
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There is another aspect to this question: who made the switchgear and to what kind of standard. I am aware of two major manufacturers that have tested their doors to stay closed while flexing to vent pressure, and suspect there is a manufacturing standard they are working to within the energy limits that might exist due to AIC ratings. This might not be the case for a small custom panel shop. Others will argue that unless the gear is arc rated, there exists no standard for arc flash containment, however; these manufactures are testing for such, whether there is a standard or not.

I also have correspondence from two major manufacturers (one of which is also mentioned above) given in the specific case of specific new switchgear. One reads something to the effect that with all covers in good shape and closed, there is an absence of exposed energized conductors that could result in arc flash hazard; the other goes beyond and states that due to dielectric distances and arc is not possible. Note that these are for very specific installations and would not cover general installations.

Supporting the idea that closed covers are safe are NFPA 70E prescriptive tables and that viewing ports are manufactured to allow IR scans through closed doors. If no advantage was gained by closed doors, there would be no need for arc flash resistant ports.


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