Devices that produce sparks under normal operating conditions specifically refer to equipment that generates arcs and sparks under normal operating conditions. Their electrical clearances and creepage distances comply with industrial safety standards, ensuring reliable insulation distances. For instance, switches, relays, and contactors without explosion-proof protection measures. When such electrical equipment is applied in Zone 2 explosive hazardous environments, the “nR” restricted breathing enclosure explosion-proof technology can be considered for protection.
Breathing-limited equipment with normal arc or spark devices should limit the dissipated power so that the temperature rise on the outside of the equipment enclosure does not exceed 20 K above the ambient temperature during normal operation. This is because if the internal air temperature of the enclosure is too high, the risk of explosive gas entering the enclosure when the equipment is de-energized increases, that is, it accelerates the “breathing” effect of the enclosure of explosion-proof electrical equipment. Therefore, it is not advisable to use a breathing-limited enclosure to prevent the ignition of spark contacts.
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