Understand the protection methods used to guarantee the level of security of the equipment.
There are several types of protection recognized by the IEC (International Electrotechnical Commission) and CENELEC (European Committee for Electrotechnical Standardization). Each protection mode is symbolized by a letter which appears on the ATEX label of the equipment. Since July 1, 2006, the standards EN50014 and EN50028 have been replaced by the standards EN60079 and EN61241 appearing in the table below. Several types of protection can be used on a single device. In this case, the symbols appear one after the other (for example Ex ib IICT4).
The most common methods of protection for ATEX lighting and low voltage switches are ATEX “d” and “e” flameproof enclosures for increased safety.
Flameproof enclosures « Ex d »
The components which generate electric arcs are enclosed in an envelope which must fulfill three functions:
– Contain an internal explosion without permanent deformation.
– Ensure that the contact cannot be transmitted to the surrounding atmosphere.
– At any outdoor point, a temperature below the auto-ignition temperature of the gases present.
The standards established for the deviation ‘i’ and the stitch length values (L) according to the gas group. Explosion-proof enclosures are usually made of cast aluminum or an alloy (minimum IP54) and require regular and careful maintenance (lubrication of joints and torques).
Increased safety « Ex e »
Each component is designed not to generate sparks or overheating, why:
– Authorizations are higher
– The terminals are specific (no gold-release)
– The enclosure is at least IP54, antistatic, impact resistant material (7 Nm).
The increased security envelopes are generally made of polyester or reinforced polyamide. The cable connections must be rigorous (pickling and tightening) and the instructions for voltages and operating current must be followed. The temperature class takes into account the hottest point of the unit.
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