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 Post subject: 70E-2015 Tabular Method
PostPosted: Tue Sep 05, 2017 7:39 pm 
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Joined: Tue Oct 26, 2010 9:08 am
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Location: North Carolina
I know this is picking a fight but consider the fact that my current day job (and sometimes nights and weekends) is field service engineer. Most of the time I'm a guest in someone else's plant. The host may or may not have spent a considerable amount of time and money on an arc flash study, and the study itself may or may not be of the best quality if they have one. In other words a lot of the time the common use of the 70E Tables may be all that I have to go on. So I have more than a little vested interest in whether or not the 70E tabular method as actually practiced (ignoring footnotes) actually works.

So when I saw a statement by Hoagland that actually goes further in suggesting that the fact that arc resistant PPE's properties of not propagating a flame may be the majority of the benefit, that got my attention. I've worn the stuff for years even when I was a young kid practicing welding on a family farm back in the 1970's. Back then a long sleeve cotton checked or denim shirt, blue jeans, and a heavy chrome tanned leather jacket (if you had the fancy stuff) was all that was available. The molten metal slag might penetrate but as long as the shirt wasn't nylon or something similar that melted or caught fire, it worked. Small slag burns were considered part of the trade at that time.

Fast forward to today, Hoagland's statement had a lot of merit to it but I was excited to see it proven out. I got a copy of the referenced article only to find that the proof was nowhere to be found. I was disappointed and in skeptical...I smelled a dirty, rotten rat of a claim. I just had to dig in and tear it to shreds so that I could prove to myself whether Hoagland's claim was really just shameless promotion of arc flash PPE or whether he simply did a quick and dirty analysis that got forgotten and never published. After some time I finally decided to simply do the data analysis myself.

To say the least I was actually shocked at what I actually found to be the case. You'll have to read it though to find out the conclusion to this little story. I know this is a controversial subject so I definitely encourage criticism both of my method and of the crazy idea itself because the potential implications are far reaching.


Attachments:
arc flash chart.xlsx [7.86 KiB]
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doan hoagland neal analysis.pdf [50.86 KiB]
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 Post subject: Re: 70E-2015 Tabular Method
PostPosted: Mon Sep 18, 2017 8:21 am 
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Paul, could you explain your process what each of the columns in your spread sheet means? I think I get what 0 and 1 are for, but please explain.


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 Post subject: Re: 70E-2015 Tabular Method
PostPosted: Wed Sep 20, 2017 6:54 pm 
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wilhendrix wrote:
Paul, could you explain your process what each of the columns in your spread sheet means? I think I get what 0 and 1 are for, but please explain.


0 and 1 are false/true or no/yes depending on how you look at it. I used 0 and 1 because it made it easier to do sums and other types of calculations.

Many of the columns won't make a lot of sense without the original article. Unfortunately I can't really put that in the writeup because it's copyrighted to IEEE.

The first column is the incident number as used in the original Doan/Hoagland/Neal paper, one per victim. It's a little hard to glean from the original if you see a notation like "3A/3B" if that means two victims from the same incident or just two different reports from a single source. It was not explained in the original either.

The equipment column is the equipment type.

The IEEE 1584 incident number number column is exactly as stated in the original paper. I used the highest value when it is given as a range.

The next column indicates whether or not PPE as specified for the equipment type as per 70E tables in the 2015 edition would or would not exceed the incident energy as stated. So a PPE Level 4 is 40 cal/cm2. For incidents 2A and 2B this is less than the stated incident energy of 80 cal/cm2.

The next two columns use the information from the original table to determine if there are 2nd degree or more severe burns in the face/chest area or not, and the next column is whether there are burns at all without regard for location or severity as given in the original report. IEEE 1584 calculation method is supposed to be a threshold on second degree burns to the face/chest area.

The next column states what analyis method was used, if reported.

The next two columns consider if the ATPV of the PPE worn on the body and on the head only exceed the IEEE 1584 column. The same rational is used to look at whether or not the PPE as descriptied exceeds the 70E tables based on the equipment and PPE worn. The final column just indicates whether the PPE is arc fated


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