2 What is an fault arc - Die BG ETEM

8 Risk assessment and calculation of arc risks
There is no mathematical-physical transformation of the results of the both test
methods because of the technical differences in the procedures, but a correlation
may be made empirically.
A pure empirical correlation of test result was made with typical woven fabrics which
were tested both, by box method and ATPV one. Figure 8.2 shows the principal
correlation found for typical arc protective fabrics made of Aramides and FR Cotton.
Generalizing it can be pointed out that box test arc protection class 2 is often safely
just given for ATPV > 30 cal/cm².
Class 1 means about ATPV = 4…30 cal/cm². The range between approximately
24… 34 cal/cm² is a mix zone, where class 2 can be passed or failed in dependency
on the specific fabric properties. The box test classes cover each a wide ATPV range.
Fig. 8.2: Empirical relationship between ATPV and the arc protection class for typical arc protective
woven fabrics/fabric assemblies made of Aramides and FR Cotton (based on [8] and test results of
Kinectrics, Toronto, and STFI, Bonn)
The information of Fig. 8.2 may not be used for characterization of a non-tested material
or PPE product. These considerations are thought for giving a rough estimation
but not for replacing according tests as well as practical decisions or PPE selection.
If the actual characterization of a product is needed, the according test is necessary
to be made.
Different textile materials, of course, have in each case their own relationships
of actual test results. The “generalization” of Fig. 8.2 is made for several textile
materials only and represents the knowledge of today. It is not transferable to other
PPE. In case of e.g. face shields quite different relationships will exist.
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