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 Post subject: 12 Cal/cm2 PPE and Levels
PostPosted: Fri Jan 13, 2012 6:51 pm 
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We were going to use PPE levels 1, 2, 3, 4 etc. like so many others.

How do you handle 12 cal/cm2 PPE with levels. I think 12 cal is better than 8 cal but when using levels it is still level 2 - which is minimum 8 cal. level 3 is minimum 25 cal.

I'm thinking we might need to abandon levels and go with minimum arc ratings.


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PostPosted: Sun Jan 15, 2012 6:45 am 
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Captain Arc wrote:
We were going to use PPE levels 1, 2, 3, 4 etc. like so many others.

How do you handle 12 cal/cm2 PPE with levels. I think 12 cal is better than 8 cal but when using levels it is still level 2 - which is minimum 8 cal. level 3 is minimum 25 cal.

I'm thinking we might need to abandon levels and go with minimum arc ratings.


The "levels" concept (HRC) is tied to the tables. It is theoretically ignored when doing the engineering analysis. Clothing manufacturers are supposed to rate their clothing SYSTEMS (as a package) for the rating it is designed for. That's the theory. In actual practice, most folks "invert" the clothing chart and work it backwards to find the required clothing for a given incident energy (cal/cm^2). Technically this is not what the chart is intended for and is incorrect usage but from a practical point of view it doesn't matter.

The other reason for the table given early on (circa mid 2000's) is that it is convenient. Clothing manufacturers only have to target a few (4) specific cal/cm^2 ratings or get close to that, instead of providing dozens of variations of everything between 1.2 and 40 cal/cm^2, which would be costly in terms of implementation. There is no mention of this in the standard but I've simply heard the argument articulated.

That being said, the clothing system you use MUST have a rating equal to or higher than the expected incident energy level if it is to be effective. For table-based approach the minimum cal/cm^2 requirements are given. For the engineering study approach, use the manufacturer-given ratings.

That being said, in practice, you can drastically simplify even the "1/2/3/4" stuff for a couple reasons. There is very little difference between "3" and "4" except that the multilayer flash suit has more layers. At one time "doubling up" was automatically allowed in the tables to achieve a "3" but now you must have a tested combination. So you can simply drop the "3" rating and not use it with very little real impact on working conditions. Second, very little clothing is actually rated "1" since 12 oz treated cloth is a minimum 8 cal/cm^2 or more. The major difference between "1" and "2" is whether a balaclava or hood is required. If you mandate these, then you can throw away the "1" rating, leaving essentially just 3 "levels" (0, 2, 4).

In a foundry application, I did this a little different. Everyone was required to have fire retardant clothing for molten metal reasons. So "standard PPE" was already a "1". So we had "1/2/4". This is not an uncommon approach. Due to the way that NESC (ANSI/IEEE C2) is written, many utilities also require 4 cal/cm^2 as standard work attire so they don't even need to consider "0" (1.2 cal/cm^2) either.


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PostPosted: Mon Jan 16, 2012 9:15 am 
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We have begun just using the arc rating on the label instead of levels or incident energy. We post 12 cal on most labels. Keeps it simple and gives us flexibility in case other arc ratings develop that don't fit the 4, 8, 25, 40 cal values.


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