NESC states that clothing or clothing system must be worn based on the values in Table 410-1 but I could not find anywhere a "clothing system" is defined unlike NFPA 70E which is very definitive.

What is considered a "clothing system" for NESC? Is face shields, hearing protection, etc. included?

Clothing Systems



Barry,

The NESC committee stopped short of defining a clothing system as you say. I believe that their definition of a system is whatever "we" in the field determine. The moderator for the Webinar on 12/11/08 clearly said that face shields are not even included as a part of the proposed 2012 code.

The tables are being revised for 2012 and (as currently proposed) self contained meters, padmounted transformers, panels, and cabinets 251 to 500 volts will now be 20 cal.

M/C Switchgear and MCC's 251 to 500 volts will be 40 cal.

In our recommendations to our clients, we are recommending face shields and hearing protection in some areas, specifically for anything requiring above 8 cal PPE. We are also expecting major resistance and controversy for some of it, but hope the proposed 2012 tables will help.

Alan

NESC and Clothing

The standard's only definition of the system is "apparel" which is usually clothing and "a clothing system that has an effective arc rating not less than the anticipated level of arc energy". This only limits the clothing worn to having an "effective arc rating" (measured or additive of the layers).

No faceshield is "required" but other standards might make it less defensible. One should consider the OSHA requirement published since 1991:

"1910.335(a)(1)(v)
Employees shall wear protective equipment for the eyes or face wherever there is danger of injury to the eyes or face from electric arcs or flashes or from flying objects resulting from electrical explosion."

This isn't cited in arc flash incidents very often but it has been in place as a general electrical safety rule for quite some time. If you are an electric utility this standard has limited applicability and there is no such language in 1910.269. There are now arc flash tested goggles, faceshields and hoods on the market which can work for many exposure situations. I always recommend wearing safety glasses at a minimum. No glasses tested for arc rating that I know of but some would do slightly better than others.

Hope this helps,

See
NESC Section 41.
410. General requirements - A. 3 Note 1

NOTE 1: A clothing system (multiple layers) that includes an outer layer of flame resistant material and an inner layer of non-flame resistant material has been shown to block more heat than a single layer. The effect of the combination of these multiple layers can be referred to as the effective arc rating.


This looks to me like an acceptable definition of what comprises a clothing system.

Hi Kevin,

Yes that is true but it mentions nothing about other PPE such as head or face protection. For example, an equivalent minimum 8 cal system in NFPA 70E-2009 lists under FR Clothing min arc rating of 8 an arc rated face shield or arc flash suit hood.

So, we have one standard specifying a arc rated face shield and another that is silent on the issue with a vague description of a clothing system.

Barry

A significant number of utilities have taken the approach that a face shield is not a requirement of the clothing system and thus are not mandating it be worn when a hazard of 8 cal/cm^2 or greater is identified.

Having attended several utility industry conferences this is based on each utilities interpretation of what the NESC requires and doesn't require.

Unlike NEC/NFPA where compliance requirements are much more specific and clearly defined.

Kevin,

Thank you. That was my thoughts but wanted some other inputs. If I can figure out if there is a way of doing a poll on this website that might be an interesting question to post for polling for other utility answers.