Avoidance of dust explosions

Totally enclosed equipment is often designed for a greater temperature rise than enclosed ventilated equipment. It should be selected so that the final 

Totally enclosed fan-cooled motors are cheaper than totally enclosed machines of the same output and are, to a certain extent, self-cleaning as the air-flow over the body shell from the external fan prevents the build-up of the dust. 

BS 6467 1988 Electrical apparatus with protection by enclosure for use in the presence of combustible dusts 

BS 6467 has two parts. Part 1 is a specification for the apparatus and recognises two categories IP5X dust-protected, which allows some dust penetration but the quantity is insufficient to cause an ignition, and 1P6X dust-tight, where no dust penetration is permitted. 

The apparatus should be labelled with the IP eategory, maximum surface temperature and minimum temperature for use or storage if this is lower than —20°C. The reason for this is that low temperatures can embrittle some materials and lead to a eraeking risk. The maximum surfaee temperature allows for a 5 mm layer of dust. 

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