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Important Survey - Correlating Incident Energy to Category

Discussion in 'IEEE 1584 - Arc-Flash Hazard Calculations' started by Jim Phillips (brainfiller), Sep 14, 2009.

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Do you list both the calculated incident energy AND the category?

Poll closed Oct 19, 2010.
  1. I just returned from an IEEE 1584 committee meeting. As Co-Chairman of the Task Group IEEE P1584.1 “Guide for the specification of scope and deliverables requirements for an arc-flash hazard calculation study in accordance with IEEE 1584” I made a presentation of the latest draft of this document. During the presentation a debate broke out about arc flash warning labels, incident energy (IE) and level of PPE.

    A small handful of members argued that you could not place BOTH the calculated incident energy AND the PPE level / category on the label. NFPA 70E 130.3(C) states that

    “Equipment shall be field marked with a label containing the available incident energy or required level of PPE."

    Most people in the industry interpret this is a minimum of either the IE or category but that it does not prohibit listing both IE and category. This “odd” interpretation means if you calculate 7.5 calories/cm2 you CANNOT list this value AND also Category 2. Needless to say most people’s jaws dropped.

    Table 130.7(11) in NFPA 70E correlates categories with incident energy. As many well know the correlation is as follows:

    Category 0 = No rating < 1.2 cal/cm2
    Category 1 = 4 cal/cm2
    Category 2 = 8 cal/cm2
    Category 3 = 25 cal/cm2
    Category 4 = 40 cal/cm2

    According to the few people that wanted to debate, their position is that you can not use this table with calculated incident energy. My response was:

    If this interpretation is truly the case, then the labels from most arc flash software are incorrect and…

    Most consultants that perform arc flash calculation studies are incorrect.

    I don’t believe either one of these statements that I made are true. I was just using them to make a point about how ridiculous this interpretation is.

    I consider their position “one way logic” which is:

    Category 2 is listed as 8 calories/cm2 but 8 calories/cm2 cannot be listed as category 2.

    Their counter argument is that these tables were only meant to be used with the task tables in 130.7(C)(9). I agree you cannot mix task tables and calculations but mixing calculated IE and categories is done everywhere. My rebuttal to their argument was: “Why do you correlate the categories to incident energy if we are not allowed to use it?”

    I do agree that you are not required to correlate categories with calculations and sometimes it can cause an over kill in PPE by doing so. A perfect example is if you calculate 9 cal/cm2. and then require the use of PPE rated category 3 which is rated 25 cal/cm2 this might be a bit of an overkill. Just because you missed the upper limit of 8 cal/cm2 for category 2 does not mean you need to jump to 25 cal/cm2 for category 3. All you need to do is exceed the calculated energy of 9 cal in this case.

    I thought I would conduct a survey to see how everyone is handling this. The survey is basically this:

    Do you correlate and list calculated incident energy AND PPE categories? Yes or No?

    This means 7.9 cal/cm2 would be listed as Category 2 in the report and on the warning label.

    Please use the survey function of this forum to vote. This will be a very important survey so please provide your vote and also any comments that you have are also greatly appreciated.

  2. Catcher13 Junior Level

    You can't be serious? It is hard enough for people to figure this out. Taking away the ability to narrow it down to 1 of 4 categories could cause more confusion than we already have. I hope the committee people can see what this would do.
  3. Canuck01 Sparks Level

    It is hard enough to train people what the levels mean so our labeling standard has only the incident energy level, working distance, analysis date and equipment ID. The reasoning behind only having incident energy level is so a worker can look at the tag on their clothes and make sure the rating higher than the hazard. A CSA sanctioned Arc Flash instructor advised that the clothing always be 1.2 cal higher than the incident energy level to guarantee a safety margin.
    CSA Z462-08 also has an "OR" standard for labeling.
  4. WDeanN Sparks Level

    I have to answer "yes" for the purpose of the survey, but would like to note that I am against this. It will be coming up for discussion at my site soon! (As you know, Jim, my supervisor is on the 70E committee, whereas I am a 1584 follower. This should be a fun discussion.)

    I do the calculations, and would like to get away from all of the NFPA tables. We do recommend that people wear clothing that is greater than the calculated energy level as posted. Past this point, I have no use for the tables. We also list the required PPE to be worn, including hood, faceshield, etc. necessary to protect up to the calculated energy level.

    As for the "debate" I don't see anything that would restrict using both. I just don't like the NFPA tables and Hazard/Risk Categories. After the calculation is performed there is no need for them. You protect up to the calculated energy level.
  5. PM Walsh Junior Level

    I guess if we can no longer use Table 11 for PPE catagores based on incident energy, we will just have to make up our own system otherwise this will be very complicated and we want to keep it simple for our crews.

    It is nice to have them use Category 2 which we all know is for 8 cal/cm2 instead of spelling out the exact numbers which vary all over the place.

    In lieu of Table 11, perhaps we can categorize our calculated values another way. Maybe we can set up our own system to help simplify the PPE selection process for our people.

    Category A = 0-1.2 cal/cm2
    category B = 1.2-4 cal/cm2
    Category C = 4-8 cal/cm2
    Category D = 8-25 cal/cm2
    Category E = 25-40 cal/cm2

    This is just one idea we have to help cut down on potentially hazardous mistakes when all we have are numbers floating around.

    .... or maybe another idea is instead of using A, B, C, D, E for our categories, we could use another designation such as 0, 1, 2, 3 and 4!
  6. WDeanN Sparks Level

    Actually, TVA has done just that. They set up different categories (I, II, III, etc). These categories were set up to correspond to incident energy levels that matched readily available PPE ATPV ratings at the time (~2002). This makes it easier to select PPE to match the category.
  7. PM Walsh Junior Level

    So in the end what is the difference between:

    Category A, B, C etc.
    HRC 1, 2, 3, etc.
    Category I, II, II etc.

    In the end, call it what you want, a Duck is still a Duck.

    Many people still need to categorize the levels of PPE and the levels in NFPA 70E Table 11 are those that most people seem to use.

    Saying you can not use Table 11 "backwards" just causes people to use a different designation for the same thing like the examples here in this post of A, B, C and I, II, III.

    I guess this might prove that who ever decided you can not use Table 11 backwards needs to think this through a little better.
  8. Good One!

    Exactly the point. There are many really great people working on the various committees - this one item though seems to have landed in a ditch.

    I have presently been working on this one to hopefully bring it to a more common sense interpretation like many have expressed here.

    Thanks everyone - keep the comments AND VOTES on this one coming!
  9. Vincent B. Sparks Level

    Annex B of CSA Z462-08, at figure B.1, shows both.

    15.3" AFB
    1.1 cal/cm^2 at 18"
    #0 at 18"

    That figure is about changing settings on a CB to lower the IE by having the arc current in the INST region of the CB.

    Better yet: Annex Q of CSA Z462-08 has sample arc flash and shock warning labels. Figure Q.2 and Q.3 both list both IE (with the working distance used to calculate it) and the HRC.

    So my take is at least in Canada, we can do it :)
  10. Even Canada uses both calculations and categories - eh? :)

    It's amazing that is seems the whole industry uses calcs and categories but a very small group on the committee still insists it can not be done this way. Thanks for the info Vincent B.
  11. LHall Junior Level

    I hope you can help get this resolved since I know we, and obviously most other people do mix calculations and categories. I know you can not mix the task tables and calculations but that does not seem to be what this is about.

    It seems like the "new?" interpretation is going to cause a lot of confusion and trouble to a situation that is already confusing enough. Good Luck!
  12. Vincent B. Sparks Level

    I can see a point in separating the calculated IE and the HRC, based on the standard (CSA-Z462 numbering as that's what I'm more used to, but I can dig in NFPA 70E if deemed necessary):

    Clause says to use to if PPE selection is based on HRC rather than IE.
    Then, Table 4 is referenced in for HRC determination based on the tasks of table 4 (and associated footnotes). Table 5 is then referenced in to determine the proper PPE required by the HRC, and Table 6 is referenced in for the characteristics of PPE for each HRC.
    Table 4 is referenced elsewhere in the standard, but for its other columns: are insulating rubber gloves required, and are insulated and insulating hand tools required.

    So, based on that, I can see a point about not using both Table 6 and calculated IE (because of the choice of rather than, because the HRC are not supposed to exist outside

    But, PPE manufacturers (and resellers) often advertise their gear using both HRC and ATPV (or EBT). So it's kinda normal to label things using both, as the worker can then easily compare what he wears (or should get at his locker) with what's required for his task.
  13. 321Liftoff Junior Level


    Hope this and many other issues get resolved, regarding the NFPA 70E '09 criterion and their interpretations. If you want to make a difference, consider the following:

    You can view the 2009 and 2004 editions as well as the timeline for approval of the 2011 document at: http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=70E

    The NFPA 70E 2011 open proposal period ends Jan 5, 2010.

    NOTE: For those interested, I sent T2G the .pdf form for Change Proposal - submits.
  14. THE CABLE GUY Sparks Level

    The important thing is to keep the program simple. I know that’s hard for engineers. (I am the one always going overboard) The more “or, if's and buts’” gets confusing to people trying to make sense out of what to do.

    I see no reason to be able to tell the worker what the cal's of heat and proper minimal PPE is on the label. Your not limiting the workers ability to wear CAT 4 if they wish.

    The label is a guide for those who need help understanding the danger. The energized work permit should be the guide for all to follow. The label is not giving permission for the person to work hot. This understanding should be part of a groups training.

    Sorry to ramble. Good Luck Mr. Brainfiller we are all looking for some simple understanding of a complex issue of what to do.
  15. Thanks for everyone's support! I was driving across Oklahoma the other day. Lots of land and open spaces.

    While cruising down the road quite board, I began thinking about Tornados and the Fujita scale. As many people know tornados are classified as F0 through F6 based on wind speed. Depending on the wind speed the tornado is given an "F" rating. If you hear a tornado had a certain "F" rating you know the upper limit of wind speed.

    The Fujita scale makes perfect sense and this is how most people also look at incident energy.

    Based on a hazard risk category (think "F" rating) there is an upper limit of incident energy. Howver unlike the Fujita scale, a few people are saying if you have a known incident energy (wind speed) you CAN NOT assign a category (F rating). It just does not make sense.

    I need to drive through Oklahoma more often!

    Thanks for everyone's comments and please keep them coming!
  16. willcoc Junior Level

    yes but moving to no

    Our next round of labels will just have the incident energy of the equipment. We will have a stand alone document that will then releate you from the energy rating to the actual PPE needed. That way if somebody decides to change what PPE is needed for 12 cal, we don't change all of the labels just our cross referance chart. Does this sound resonable?
  17. acobb Sparks Level

    And you just had to confuse me further didn't you Jim! I can't even spell Fugeeta! What's up with that?:D

  18. Sounds reasonable. You have the choice of listing the incident energy or level of PPE. Most companies and computer programs list both. The 70E movement is to take away your option to use both which does not make much sense.
  19. Vincent B. Sparks Level

    Seems like the CSA Z462 committee is gearing up to officially separate them.

    With 70E and Z462 currently technically harmonized, I don't know how this will develop in the future. I sure hope they stay close to each other, as this will be easier for everybody in Canada.
  20. THE CABLE GUY Sparks Level

    According to Mr. Becker from another question it appears to say; "you cannot put HRC values on the detailed label" after the arc flash analysis.
    Glade to see not only the US has confusion.

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