Dynamic elaboration on the Art & Science of Hazardous Area Protection
IEC Document : IEC60079-1
Parts which can ignite a potentially explosive atmosphere are surrounded by an enclosure which withstands the pressure of an explosive mixture exploding inside the enclosure and prevents the transmission of the explosion to the atmosphere surrounding the enclosure.
|Type of Ignition Protection||Abbreviation||Region||Classification||Specification/Standard|
|Flameproof Enclosure||AEx d||US||Class I, Zone 1||ISA 60079-1|
|Flameproof Enclosure||Ex d||CA||Class I, Zone 1||CSA E60079-1|
|Flameproof Enclosure||Ex d (EEx d)||EU||Zone 1||EN 60079-1|
|Flameproof Enclosure||Ex d||IEC||Zone 1||IEC 60079-1|
|Explosion Proof||XP)||US||Class I, Division 1||FM 3615|
|(XP)||CA||Class I, Division 1||C22.2 No. 30|
Level of Protection da (EPL ‘Ma’ or ‘Ga’)
Level of Protection db (EPL ‘Mb’ or ‘Gb’)
Level of Protection dc (EPL ‘Gc‘)
1. Machine Control Syatems
2. Power Distribution Systems
3. Terminal Boxes
5. Switch Gear
6. Motor Switches
7. All Power distribution & control applications, involving non-certified industrial components
This is one of the oldest Explosion protection Techniques , still in use today. The basic philosophy is SEGREGATION or separation of the Explosion Causing Elements from the Explosive Atmosphere by providing a strong metallic enclosure for the Electrical Components and sealing it properly so that the the spark-producing electrical component is COMPLETELY separated from the Explosive Atmosphere .
IF however , the explosion does take place inside the enclosure then the residual material (Smoke or flames) remains inside the enclosure because of the strength of the enclosure-material and the extra pressure is released through the special joints of the enclosure-lid so that the escaping smoke and flames are cooled sufficiently. These special joints are called “Flame Paths “.
(See post : Maximum Experimental Safe Gap)
The basic component which provide the protection in the hazardous area (GAS or Dust) is thus the ENCLOSURE.
Buying a certified EMPTY ENCLOSURE (Ex d) , with a ‘U’ certificate and populating it with industrial type electrical components ,in your own workshop, to sell it as a Certified Ex d Assembly is both DANGEROUS and Prohibited.