EXPLOSION HAZARD ASSESSMENT: TEMPERATURE CLASS

Another important aspect to consider is the ignition temperature of substances present in a potentially explosive atmosphere, which is the minimum temperature at which an explosive mixture will spontaneously ignite.

This value must obviously be higher than the maximum surface temperature developed by various products, devices or equipment located in a place where an explosion may occur. With regard to gases, electrical components approved for use in potentially explosive atmospheres are divided into six temperature classes from T1 to T6.

For a more accurate assessment, it is useful to know the classification of some of the most common substances in an industrial environment according to gas group and temperature class:

Ignition temperatures of some combustible powders
Dust is an often underestimated risk. Below are some typical ignition temperatures for both clouds and layers:

Other methods of protection against combustible dust

For equipment intended for use in environments with combustible dust, additional special methods are applied in accordance with international standards:

• Dust protection: the enclosure prevents the ingress of combustible dust particles, protecting the internal components from possible explosions.
• Sealing: a controlled internal atmosphere prevents dust from entering the enclosure.
• Sealing: parts at risk are completely covered with resin or other insulating material.
• Internal safety: even in the presence of dust, the circuits are designed so that sparks or high temperatures cannot cause an explosion.

These methods, each of which is regulated by specific standards and applicable to zones 20, 21 and 22, ensure that electrical equipment is adequately protected in the presence of both gases and combustible dust.