Enclosure class markings

Enclosure considerations (interlocks, insulation class, shock, marking, etc.). 

Classification and marking of intrinsically safe apparatus concerning explosion groups (I, IIA, IIB, IIC) and temperature classes (T1-T6) are organized in the same way as for, e.g., flameproof enclosure - d (see Tables 4.1 and 4.2, Chapter 4, and Chapter 5 for marking). Some special features, however, which are of importance for type of protection intrinsic safety - i only, will be explained in the following. 

Cautionl U.S. NEMA class and European IP ratings are not always equivalent (NEMA 12 IP 54) Both the dust and water tests must be performed according to EN 60529 with passing results. Enclosures often fail the IP requirements, especially the dust tests. It is best to use a type-approved and marked (VDE/TUV) enclosure to ensure conformity. 

Finally, laser package marking which have a Class 4 carbon dioxide laser [Class 1 with the equipment enclosure in place and the door(s) closed] are used to physically mark the exterior of plastic and ceramic packages. Fumes can be created during the marking and create residues on the equipment surfaces and fume extraction filters. Plastic epoxy packages contain antimony trioxide as a fire retardant (typically 1-5%), and ceramic packages may contain beryllium. 

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