Determining Arc Flash PPE levels for different tasks

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mull982

Senior Member
I am trying to determine different Arc Flash PPE levels for different tasks around our facility. I have having a full Arc Flash study completed to identify the different Incident Energy at various equipment in the plant.

The next question I ask myself is how to define the arc flash and PPE levels for the different tasks that may be performed on a piece of equipment. For instance lets look at a piece of switchgear that may have a completely different set of hazards for racking in a breaker vs simply looking at a panel mounted meter display.

To define the different PPE levels required for different tasks around a piece of equipment I'm looking at table 130.7(C)(9) in NFPA 70E. For a given type of equipment it shows the PPE levels appropriate for different tasks. However this table assumes a certain avaliable fault current and clearing time to derive these PPE levels. If my Arc Flash study shows that there are higher avaliable fault currents or longer clearing times resulting in higher IE and PPE levels then how do I take this PPE level from my Arc Flash study and corroloate it to the different activities in this table?

As an example for Metal Clad Swgr at 1kV the table shows that to work on energized electrical conductors for control circuits 120V or below exposed only a PPE level of 2 is required. However what if my Arc Flash study shows higher values for the assumed fault current and clearing time that the table used and lets say my study shows this swgr as a category 3. Do I need to change the working on control circuit from a category 2 to 3? Do I need to change all activities in the table to have a minimum of PPE level 3 or can some of them stay what is stated in the table regardless of Arc Flash study results? Would the Arc Flash study simply give PPE values only when involved with working with or involved with energized conductors at the equipment voltage levels.

I'm intersted to hear from others once Arc Flash levels are establised at equipment how you go about defining what is required for different tasks involved with that equipment.
 

billsnuff

Senior Member
Once the arc flash study is completed and the equipment is labeled, you no longer need the tables.

I would direct you to annex e of the 2009 70e and annex f. With the proper safety program and completed risk evals for the many tasks, in conjunction with the labeling, you will know the PPE answers.

Check the safety protion of the forum and the FAQs. Zog put some good stuff there.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
I haven't had a chance to read Zog's "good stuff," but I will risk mentioning a couple things. Unless you match the conditions of the table, the table is useless. Then you are in need of the arc flash study. Thereafter, however, it is no longer about tasks versus risks. You can read a meter from the outside of a panel without any risk, and without any PPE. But as soon as you open the door, it will not matter if your intent is to take a thermographic image or rack out a breaker or tighten a connection or do any other task. You are disturbing the system. Any disturbance can cause the wrench that some idiot left inside the gear to fall onto a busbar, or cause a "somewhat loose" wire to become completely loose, or cause a "nearly broken" spring to fail completely. Any of these things can be the start of an arc flash event.

The arc flash study will tell you how much arc flash energy could be released, and the "rule book" will tell you what PPE is needed for that energy level. You must use that PPE, no matter what task you have in mind.
 

zog

Senior Member
Location
Charlotte, NC
The door being open or closed has nothing to do with the PPE requirements after you have done the study, thee are no "closed door" equations. The key is "interaction with equipment" as defined by 70E, which includes things like operation with the doors closed.
 

MIEngineer

Member
Location
Michigan
With the direction that the doors do not provide any protection why does IR testing require arc flash PPE?
I guess it would also apply that once a cover is removed from a panelboard and there is no more "interaction" with it would arc flash PPE be required to read the model numbers off of a breaker or look at it?
I understand and agree that there is no PPE required to pass by equipment with all covers on. Why then is it required if the covers are removed and I am just passing by?

Thanks.
 

zog

Senior Member
Location
Charlotte, NC
With the direction that the doors do not provide any protection why does IR testing require arc flash PPE?

I never said the doors offer no protection, the problem is there is no way to calculate how much protection, if any, they provide, and likely never will be. In fact, some research suggests in some cases having the doors closed can be more hazardous than open.

I guess it would also apply that once a cover is removed from a panelboard and there is no more "interaction" with it would arc flash PPE be required to read the model numbers off of a breaker or look at it?
A visial inspection in "interaction" per the 70E.

I understand and agree that there is no PPE required to pass by equipment with all covers on. Why then is it required if the covers are removed and I am just passing by?
Thanks.

It is not required.
 

skeshesh

Senior Member
Location
Los Angeles, Ca
I'm not an arc flash expert by any means, but have been involved in several arc flash studies. The senior engineer I worked with provided the required PPE to the client as a part of the study and also indicated this information on the labels. I recommend in the future that you include producing this information and proper labels as a part of the scope of work when you hire a consulting engineer.
 

mull982

Senior Member
I haven't had a chance to read Zog's "good stuff," but I will risk mentioning a couple things. Unless you match the conditions of the table, the table is useless. Then you are in need of the arc flash study. Thereafter, however, it is no longer about tasks versus risks. You can read a meter from the outside of a panel without any risk, and without any PPE. But as soon as you open the door, it will not matter if your intent is to take a thermographic image or rack out a breaker or tighten a connection or do any other task. You are disturbing the system. Any disturbance can cause the wrench that some idiot left inside the gear to fall onto a busbar, or cause a "somewhat loose" wire to become completely loose, or cause a "nearly broken" spring to fail completely. Any of these things can be the start of an arc flash event.

The arc flash study will tell you how much arc flash energy could be released, and the "rule book" will tell you what PPE is needed for that energy level. You must use that PPE, no matter what task you have in mind.

So your saying that once an Arc Flash study is completed you can no longer break the different tasks (IR scan, control measurements, etc..) into different hazard levels, but rather have to have everything at the same hazard indicated by the study and PPE needs to be worn for all of those tasks?

I guess the reason the tasks could be seperated in the 70E table are because they were calcuated based off of certain assumed conditions? But with a study those assumed conditions are out the window so you must where PPE for everything?
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
I am a complete novice on this topic. But at least I am in good company. :grin:

My understanding is that once an arc is created, the amount of energy it will release depends primarily on the available short circuit current and the time it takes for the overcurrent device to terminate the event. How is that related in any way to the task the worker was doing?

So why would 70E even present its PPE requirements in a table that includes the tasks being undertaken? I cannot say. My best guess is that the nature of the task has a bearing on the likely hood that the task will inadvertently cause an arc to begin.
 

zog

Senior Member
Location
Charlotte, NC
So your saying that once an Arc Flash study is completed you can no longer break the different tasks (IR scan, control measurements, etc..) into different hazard levels, but rather have to have everything at the same hazard indicated by the study and PPE needs to be worn for all of those tasks?

I guess the reason the tasks could be seperated in the 70E table are because they were calcuated based off of certain assumed conditions? But with a study those assumed conditions are out the window so you must where PPE for everything?

Exactly, once you have identified the Incident Energy levels you are bound to protecting employees from that Ei. The task tables are no longer valid.
 
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