Non-melting clothing

Our company in the past 2 years has implemented an electrical safety and control of hazardous energy program for employees world-wide. Our daily work-wear clothing minimum requirement is non-melting clothing, except in US and Canada for which our AFHA’s determine minimum PPE requirements. Unfortunately, many countries have yet to recognize arc flash is a real threat to people and arc flash isn’t isolated to just North America. (Good news is they are beginning to wake up!)

As the implementation project manager I have not been able to find non-melting clothing for our Chinese colleagues that can be sourced in China. We can get clothing items from other countries but at a higher costs, shipping delays, etc.

Anyone have any experience in this area or have any suggestions? READ MORE

Behavior of Apparel Fabrics During Convective and Radiant Heating

Personal protective equipment (PPE) recommended for arc flash is not always designed for arc flash exposure. The purpose of this paper is to warn of the dangers posed by using the improper materials in arc flash exposures until standards have caught up on this issue.

The table below shows a representative range of everyday textiles along with some of the measurements of importance in establishing their response towards convective and radiant heating[1]:

Properties of Fabric Table

 

Times to ignition or melting of the 20 fabrics in Table above were reported by Wulff[2], [3] for different incident heat fluxes. The Wulff’s data have been used to develop a methodology by which ignition and melting times may be forecast. A semi-empirical relationship between ignition/melting time and radiative heat flux has been derived[1]:

[NF0] = -1 / NBi * ln(1 – NBi / [qxrad]) + a * [qxrad]^b * (1 – NBi / [qxrad])^-1, Equation 1
where [NF0] is the non-dimensional destruction time of the fabric (that is, time to ignition or melting) and is given by:

[NF0] = (k/l) * t / (pl * c), Equation 2

 

where:

(k/l) – average thermal conductance, W / (m^2 * C);
t – ignition/melting time, sec;
pl – mass/unit area, kg / m^2;
c – average specific heat, W * sec / (kg * C).

NBi is the Biot number which is defined as the ratio of the average convective heat transfer coefficient of the fabric to the average thermal conductance of the fabric. It is obtained experimentally for each fabric.

The non-dimensional radiative heat flux [qxrad] is given by:

[qxrad] = ads * W0 / (k/l) / (Tim – T0), Equation 3 READ MORE