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 Post subject: PPE Category Interpretation
PostPosted: Tue Jun 03, 2014 10:07 am 
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Hi Friends,
On a 600V switchgear, the Arc flash label on Main Service Disconnect is PPE Category 4. The NFPA 70E 2012 Table 130.7(C) (15) (a) states, with the Enclosure doors CLOSED, the circuit breaker operation (ON/OFF) can be performed with PPE category 0. Now, if the PPE category 0 is going to be eliminated in NFPA 70E 2015, are we suppose to wear PPE Category 1 to operate the circuit breakers/fuse (with enclosure doors closed) or with just any casual dress?


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 Post subject: Re: PPE Category Interpretation
PostPosted: Tue Jun 03, 2014 10:26 pm 
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A similar discussion was held here: viewtopic.php?f=33&t=3230


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 Post subject: Re: PPE Category Interpretation
PostPosted: Wed Jun 04, 2014 1:35 pm 
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Namgay Tshering wrote:
Hi Friends,
On a 600V switchgear, the Arc flash label on Main Service Disconnect is PPE Category 4. The NFPA 70E 2012 Table 130.7(C) (15) (a) states, with the Enclosure doors CLOSED, the circuit breaker operation (ON/OFF) can be performed with PPE category 0. Now, if the PPE category 0 is going to be eliminated in NFPA 70E 2015, are we suppose to wear PPE Category 1 to operate the circuit breakers/fuse (with enclosure doors closed) or with just any casual dress?


Under 70E-2012, see the definition of "Arc Flash". The tasks which would be considered interacting with equipment in such a way that would cause an arc flash get rated H/RC 4. Those tasks that are not are rated H/RC 0. What makes this really confusing is that the informational notes seem to suggest that ANY task in the tables qualifies as interacting in such a way as to cause an arc flash when clearly some do not. Worse still, this is not universal. Some breaker operation tasks are classified as H/RC 2 on H/RC 4 equipment.

The draft changes for the 2015 edition are:

1. What used to be called "H/RC 0" which means nonmeltable clothing is now the minimum PPE standard for qualified workers. As a result, H/RC 0 and any other tasks that require a bare minimum of <1.2 cal/cm^2 rated PPE (which is more of a type rating than an actual rated PPE) goes away. What is missing of course is what to do with unqualified workers. You are on your own with those.
2. Instead of an arc flash HAZARD assessment, the new edition will require an arc flash RISK assessment. Thus the issue of "interacting" MUST be addressed in one of two ways:
A. Do your own risk assessment for all tasks. This would include both a hazard assessment (using IEEE 1584 or another methodology), and a likelihood assessment for each task, combined with what each company considers acceptable risk. For this case you may determine that the likelihood of failure with switching activities is so low that it is a tolerable risk and choose not to mandate any PPE beyond the minimum required.
B. Follow the new tables. The first table looks at likelihood and determines whether or not arc flash PPE is required. The second table identifies the amount of arc flash PPE required based on the type of equipment. The third table is the familiar PPE table based on the "PPE level" (changed form H/RC rating) given in the equipment table.

With this in mind my personal recommendation is to do exactly what you are not supposed to do: mix and match. With separate likelihood, severity, and PPE tables, there is no logical reason that one cannot use the table approach for likelihood, a calculation approach for severity such as IEEE 1584, and the PPE table for required PPE.

In the past MANY practitioners wrongly used IEEE 1584 for the calculation and then used the PPE table "backwards" (using the calculated incident energy rather than the H/RC value). Now that likelihood, incident energy, and PPE are three separate and distinct tables there is no logical reason for not mixing and matching.


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 Post subject: Re: PPE Category Interpretation
PostPosted: Mon Jun 09, 2014 8:20 pm 
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Good Morning

I well explain just my personal experience with circuit breakers.
To operate those breakers is better to be done remotely, If remote operation option is not available better to use HRC4 uniform.
I have seen staff injured while racking in breaker and operating as well.

Now you have to see in category 4 PPE up to what CAL/CM2 you have to use it is depend on arc.

end of the day it is your health and safety forget about who says what.

regards


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 Post subject: Re: PPE Category Interpretation
PostPosted: Fri Jun 13, 2014 1:37 pm 
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abdulaziz wrote:
Good Morning

I well explain just my personal experience with circuit breakers.
To operate those breakers is better to be done remotely, If remote operation option is not available better to use HRC4 uniform.
I have seen staff injured while racking in breaker and operating as well.

Now you have to see in category 4 PPE up to what CAL/CM2 you have to use it is depend on arc.

end of the day it is your health and safety forget about who says what.



This is a common, extremely dangerous, and utterly poor opinion expressed by many people. The idea is that wearing PPE is safer than other alternatives. I can tell you honestly its not, not even close. At best, when it works, and PPE is pretty high on the failure rate category, it manages to reduce the degree of injury. I said reduce, not eliminate. IEEE 1584 makes it very clear that there is a 5% chance of failure in the event of an arc flash even if everything is done properly due to predictability issues with arc flash. With properly maintained breakers, the likelihood of having an arc flash in the first place drops by a factor of 100 or more. So instead of a factor of 20 reduction in likelihood of a major injury but still likely a 100% chance of a minor injury to a factor of 100 reduction in having any injury at all. Industrial accident rates are around 1 in 100,000. Properly maintained breakers fail at a rate of 1 in 1 million to 1 in 10 million. So you are between 10 and 100 times likely to be injured by something else. So the reason that 70E drops the PPE requirement is because wearing PPE to protect against an extremely rare incident is vastly outweighed by the disadvantages.

1. If I don't maintain the breakers in my plant, MANY are well over 40 cal/cm^2 potential. Some are already over 40 cal/cm^2 under normal circumstances and thus marked that way but almost 25% are not. Failure to properly maintain equipment is a recipe for a future major injury or fatality.
2. Your arc flash study and any tables in 70E for that matter don't mean anything if equipment is not properly maintained. 70E is pretty clear on this and given the alarmingly high failure rate on improperly maintained breakers especially the high maintenance variety (draw out), it seems pretty clear that if given an option between attempting to "overprotect" and maintaining breakers, the alleged improvement in safety by wearing the PPE is vastly less than maintaining the equipment. This is a flat out violation of the principle of ALARP (as low as reasonably practicable), which is also clearly spelled out in the 2015 edition. So for you, putting on the 40 cal suit is stupidly dangerous because the equipment is not being properly maintained. The tables and engineering calculations clearly don't mean anything either. I suggest staying home and not coming to work because the likelihood of a fatal automobile accident on the way to work by the way vastly exceeds the likelihood of an arc flash fatality.
3. If breakers are maintained properly, the odds of failure are well under 1 in 100,000 and often 1,000,000 or more depending on some design details. The tables in 70E (2015 or 2012) are merely acknowledging this.
4. Wearing 40 cal suits reduces visibility, hearing, and dexterity, which encourages more reliability issues. Plus since it is a lot more trouble, it encourages short cuts. Maintaining breakers costs money and time too, and again, encourages short cuts in management decision making.
5. I have yet to find a remote operator for a breaker that does not have a chance of damaging/destroying the breaker and yet still functions correctly. Use of these devices reduces breaker reliability, period. So again...we're encouraging short cuts and fooling ourselves into thinking that this is safer.

The only caveat to any of this is defining "proper maintenance". I don't think we're truly there yet.


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 Post subject: Re: PPE Category Interpretation
PostPosted: Mon Jun 16, 2014 11:19 am 
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It is my understanding from an OSHA interpretation, that once the arc flash analysis is completed for the equipment, you are to wear the PPE to protect you from the potential hazard while you are interacting with the equipment.
In our company we have made it a policy to wear the correct level of PPE that is stated in the arc flash analysis if you are interacting with a piece of equipment, whether the covers are closed or not. We have a very extensive maintenance and testing program, but our equipment is getting older. We have had several arc flash incidents, fortunately we have only had one major injury. We have had many pieces of equipment fail with the covers closed while interacting that the covers do not stay closed. Properly maintained or not, there is a lot of energy released during a fault and the covers do fail.


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 Post subject: Re: PPE Category Interpretation
PostPosted: Wed Jun 18, 2014 5:27 am 
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lovetacycle wrote:
It is my understanding from an OSHA interpretation, that once the arc flash analysis is completed for the equipment, you are to wear the PPE to protect you from the potential hazard while you are interacting with the equipment.
In our company we have made it a policy to wear the correct level of PPE that is stated in the arc flash analysis if you are interacting with a piece of equipment, whether the covers are closed or not. We have a very extensive maintenance and testing program, but our equipment is getting older. We have had several arc flash incidents, fortunately we have only had one major injury. We have had many pieces of equipment fail with the covers closed while interacting that the covers do not stay closed. Properly maintained or not, there is a lot of energy released during a fault and the covers do fail.


OSHA is very clear that risk assessments should be done for all tasks. There is no differentiation on this. A hazard analysis is only 50% of what is required.

Covers do matter as far as the hazard is concerned but the real value is that with certain tasks they eliminate the shock hazard and eliminate several vectors to causing an arc flash. It has zero to do with incident energy and unlike 70E I am not hung up on covers and neither is OSHA in their 1600 page update to distribution rules. If I operate a breaker outside the restricted approach boundary, covers do not matter. They only play a role in reducing that boundary to zero. It is a mistake in my opinion in mentioning doors in the arc flash section because the limitation needs to be based on qualifications and working outside the restricted and/or limited approach boundary. Mentioning doors closed is simple to understand but clouds the issue.


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 Post subject: Re: PPE Category Interpretation
PostPosted: Thu Jul 03, 2014 11:13 am 
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I have told many engineers and service techs that all closed doors do is create a shock barrier.

The only thing closed doors do for you as far as arc flash goes is
- you cant throw a wrench (or drop a wrench) into the enclosure or across a live bus if the doors are closed.

If an Arc Flash incident is happening the doors are likely to be melted through - or become projectiles


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 Post subject: Re: PPE Category Interpretation
PostPosted: Fri Jul 04, 2014 12:43 pm 
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Simple class exercise as per another thread. Say arc blast at the door is 2 PSI. Calculate force on a door (pick one). Although JHU has done some work on melting through enclosures, this takes time. Arc blast is over in a few cycles. In other words, doors either bend and give way or are blown off.


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