Ex t EN 60079-31 Explosive atmospheres. Equipment dust ignition protection by enclosure "t"
En 60079-13, introduced in 2009 is a specific standard for dust using 'Protection by Enclosure' i.e. keep the dust out.
Based on the principle, for Dust, that a good ingress protection rating, by definition, should be sufficient to prevent an explosive dust mix forming within the enclosure. The primary concern therefore is the temperature rise of the walls of that enclosure1.
Split into 3 protection levels Ex ta, Ex tb and Ex tc for Categories 1D, 2D and 3D respectively. Ex ta is the only2 Category 1 protection method other than Ex ia.
If the primary protection method is to keep the dust out then generally it does not matter what goes into the enclosure3 as long as the heat dissipation is considered. Any items going through the enclosure walls i.e. coming in contact with the dust must be suitably certified.
Ex ta has additional requirements for arcing and sparking parts and not only must the marked maximum surface temperature must be measured on the outside of the enclosure but also internally ↩
There may be limitations for some specific components e.g. batteries. ↩